My Mazda MX-5

Next project starts a new blog...

2018-07-05T13:36:00.004-07:00

...which can be found here https://mydatsun120y.blogspot.com/

Happy readings!

My cars - Second chapter

2016-09-16T22:16:00.000-07:00

I am sitting in a long hauler bus and it is 7 am. I woke up an our earlier and in three and half hours I will see, lets hope so, my next car. If it appears to be as advertised, it will be another four hours drive back. A perfect way to spend a saturday.

The red MX-5, which this blog originally was about, was sold one year ago. I had it for over ten years and it basically was nothing but a pleasure. Sure, we had some downhills too, but really there was nothing wrong with that car. And boy oh boy, that 8500 rpm redlining 173 bhp naturally aspirating four banger was pure ear candy. Despite all of that somehow my thoughts began to shift towards older vehicles, perhaps ones with a hint of historical value and 70's flowing body lines.

So why has it taken a year to get to this point? I went to see and test drive a couple of candidates during the summer while last winter was spent with other activities. Two BMW 1502s fell into 70's category. BMW's driver oriented reputation compensated the lack of flow in the body styling. The better example was in very good condition but unfortunately the lack of use was clearly felt in the ride quality. A couple of Datsun 180B's were on offer too. The better one was in original condition, reasonably priced and to no one's surprise was sold in couple hours. The other one, which was in SSS trim, revealed to be in poor condition. Most of the bits and pieces were there but the corrosion was wide spread and the paint was - well, a money pit with a capital p.

I even explored the early 80's super car option. Early Porsche 928s were very tempting in many ways. The better samples are expensive for a reason and vice versa. I drove one 928S with automatic transmission. It had over 200 thousand klicks on the odo and six or more owners. How should I put it? In the kind of condition a Porsche 928 deserves to be, that car would have been a wonderful piece of German engineering. But that one was not. And I was not going to be the one who spends a fortune to bring it to the original glory.

So here I am sitting in a bus with three more hours to go. Will that 42 years old, low mileage, four seater, two door sedan win my heart? Most likely yes, but nothing is sure until it is sure.

Klaus Ludwig’s 1988 DTM Title Winning Ford Sierra RS500 Cosworth - Alive Again!

2014-12-06T05:23:00.000-08:00

The one and only, the legendary, Klaus Ludwig’s 1988 DTM title winning car Ford Sierra Cosworth RS500 is presented in its original winning glory. Where? In Finland – of course! This unique piece of European racing heritage is so amazing that it deserves to be brought into public attention.

The owner of the race car power house - Sarlin Race Team - Kalle Sarlin did not just win the Finnish Touring car championship with this same Sierra Cosworth in 1991, but he also took the time and effort to take this classic back to its original glory.

Kalle and his crew started the restoration of this fine piece of machinery about ten years ago. It has taken hundreds of hours to get it to this point where everyone can let their eyes feast on its beauty. The restoration began from the bare body shell and continued step by step until the current state was reached.

Nowadays to an untrained eye it might just look like another Ford Sierra with some stickers on it. But to all of you guys who know what to look for its obvious that this beast is nothing but business. Wide racing slicks wrapped around three piece BBS magnesium alloys with center-locks are yelling “No, it is not another tuned 3-door Sierra with graphics”.

Under the bonnet lurks a turbocharged 2-litre RS500 racing engine. This Ford’s YB-series 16 valve DOCH inline four has been seriously refined to be able to take the heat of the continuous racing. Garret’s T3/T4 turbocharger feeds compressed air to the engine through a big air-to-air intercooler. Group A cylinder head and Group A pistons guarantee that neither the airflow nor mechanical strength becomes an issue. Three external fuel pumps and 8 injectors make sure that the air fuel ratio stays where the Bosch Motronic MP1.7 engine management system commands it to be. Roughly 480 hp is transmitted to the rear wheels through a sand casted Getrag 5-speed gearbox and a Ford Motorsport 7.5” differential. Both gearbox and differential are cooled with PWR oil coolers.

What is a race car without a proper suspension and brakes? A street car, perhaps. Well, in this case nothing but Ford Motorsport Group A magnesium uprights, Group A magnesium rear arms, quick steering rack, Bilstein coil-over shocks (front/rear) and adjustable front anti-roll bar are there. The brakes are from AP-racing with 4-pot calipers front/rear and vented rotors 330x35 mm front plus 304x28 mm rear.

As if all of the above mentioned was not enough, the list of the goodies goes on: Factory RS500 front lip spoiler, bumpers, twin rear spoilers, heated windscreen, seam-welded chassis, FIA-spec multipoint roll cage, air jacks, Recaro SPA carbon/kevlar seat, 6-point harness, Bosch Motorsport LCD display and so on...

Oh, what mechanical beauty.

Article update: Cossie has found a new owner, and I have been told, had some serious track time on the Nürburgring!

Follow SRT also in facebook:

https://www.facebook.com/sarlinraceteam

More NA POWER part 5: 100 bhp per liter in 1.7 liter B6ZE

2014-11-06T10:08:00.000-08:00

My engine tuning project has finally achieved its goal - to make 100 crank hp per liter in naturally aspirating form. Current maximum figures are 173 hp of power and 181 Nm of torque (crank). And max figures are not all, torque peaks up at 4000 rpm and there is usable power up to 8000 rpm. Let’s first take a brief look at the previous modifications and then inspect the current setup a bit closer.

In 2008 basic bolt ons with oem cams produced 132 crank hp and 151 Nm (105 rwHp and 124 rwNm). That was all I could get out of a 1.6 liter engine with bone stock internals and a larger RX-7 AFM.

In 2009 the engine was bored to 1720 cc with high compression (11:1) Toda Racing pistons. The head was mildly ported with oem valves which were left untouched. Also Toda Racing 272/9 cams (in&ex) and solid lifters with stiffer springs, measured to be good for 8300 rpm with safety margin, were installed. Conrods were still the old ones with about 140 000 km behind. There were no adjustable cam gears and the catalytic converter was bone stock, also possibly clogged. Van Kronenburg Management System’s fully adjustable ECU was wired to have a command on the injection and ignition. This setup produced 156 hp / 175 Nm (121 rwHp / 147 rwNm). After the build I had almost two years of happy high revving when the original conrods finally gave up. It luckily happened with no drama as the engine suffered a spun rod bearing.

Forged Toda Racing pistons (3 mm oversize) and CP Carrillo A-beam rods, 110 grams less than stock.

In 2011 as the engine was torn apart for the bottom end rebuild the cylinder head also went under maintenance. The block received a factory new long nose crank, Carrillo A-beam rods, ACL Race Line bearings, Toda Racing pistons and Toda Racing light weight flywheel - all dynamically balanced. New valve guides were installed and stock valves received a three angle grind to improve the head flow. Old cam gears and worn cat were replaced with Toda Racing adjustable gears and Catco’s metallic 400 cell unit. Instead of the standard 1.0 mm thick head gasket a 0.8 mm thick optional part from Toda Racing was installed to increase the compression ratio to about 12:1. I also wanted to lower a bit high intake air temperature and fabricated a sealed airbox that was supposed to produce a ramming effect in higher speeds. With revised cam timing this setup produced an estimated 160 crank hp. Crank power is estimated because this time a hub dyno was used and the measured figures were 132 rwHp and 142 rwNm. I was getting closer to my 100 crank hp per liter goal!

During the 2011 dyno session it was noticed that the original throttle body started to restrict the flow (a vacuum was building in the intake manifold over tb). Another visit to the hub dyno was made in 2012 with a new 60 mm diameter throttle body installed and ported to the intake manifold. The result was a bit disappointing with only minimal gains (135 rwHp and 145 rwNm). At this point the airbox started to be the main suspect for creating a bottleneck.

AT Power 60 mm 'Shaftless' throttle body required some porting to the intake manifold.

Finally this spring I made the latest to the dyno (inertia type once again). A wanted to make a back to back comparison with the old airbox and the new “cold side” cone filter intake. I prepared for the dyno session by checking the valve lash and noticed that they all were on the loose side. Meticulous adjustment to the specs (0.20 mm intake and 0.25 mm exhaust) was done. I also checked that the intake manifold was port matched to the head. First pulls on the dyno with the old airbox indicated restricted flow above 5500 rpm. Peak torque was 159 rwNm at 5000 rpm and after that the curve sank to about 150 rwNm. Max power was 138 rwHp.

After that the new intake was installed and it was time for the final pulls. And there it was! The torque stayed up till 6750 rpm, and maximum output of 173 crank hp (144 rwHp) was achieved.

What is the most noteworthy, in my opinion, is that this motor runs on a stock intake manifold, although port matched. The head porting is also mild, I would call it a “fast street porting”, and stock sized valves are used. The potential of producing current figures has always been there but the output has been hampered with various restrictions. In the very beginning it was the displacement and cams. Then it was the flow of the cat, improper cam timing, restrictive throttle body and intake plumbing.

So, what is the current bottleneck? Evidently there is something restricting the flow above 7000 rpm. Intake runners, stock valves, current cam profiles, exhaust manifold, 2” catback exhaust pipe or something else. Stretching the power band 800 – 1000 rpm higher would be good for another 15 to 20 hp. We will see…

Miata Camber Gain and Latest Suspension Mods

2014-05-25T09:46:00.000-07:00

It was about time to get rid of the original rubber bushes that had taken the beat at the track and resisted the wear and tear of road use for 23 years. I installed a complete set of Energy Suspension poly urethane bushes during the winter. The job was quite straight forward and I could complete it in my ordinary garage. It took some time but I was not in a hurry.

I also wanted to replace my old Koni Sports Kit with something more suitable for racing. Most of the track oriented guys here in Finland have opted for BC Racing. They seem to work nice and customers are satisfied. I must admit having an issue with BC-racing shock coming from Taiwan. I also don’t like the high spring rates they use. I know, they are not all bad and BC’s kits evidently work nice. Another issue was money. Bilstein, Öhlins, KW, AST, JRZ and Koni all make excellent shocks and complete kits, but they come at a price – too high for me.

So, after some consideration I took my old shocks to the local Koni importer who offers an inspection service for all of their products – free of charge. And guess what, they were as good as new! After a short chat with the mechanic I decided to keep them and try to find adjustable perches with slightly stiffer springs. It did not take long to find out that Ground Control Suspension Systems in California had what I needed. I was more than happy that a set of Eibach racing springs was included in the kit. I went for 6,6 kg in the front and 4,4 kg in the rear, which the Koni mechanic recommended was a good starting point. Shocks could be revalved afterwards if stiffer springs were needed. I must emphasize that at the Ground Control the quality of the service was as excellent as the quality of the kit – I have nothing but good feedback to give!

While I was waiting for the GC-kit to arrive I made some basic research and measured Miata’s camber gain. Both front and rear were first set to a reasonable suspension height ( 310 mm front and 325 mm rear from the wheel hub center to the fender flare). Then I simply jacked the wheels up while the car was on four jack stands and measured the change of the camber angles. The gain is roughly 0,5 degrees per 10 millimeters of wheel travel, both front and rear.

I could not be happier with these two simple mods. Combined with increased chassis rigidity and more aggressive wheel alignment the car really has started to take corners. I was able to shave of almost two seconds from my best lap time at the first visit to the Ahvenisto racing circuit this spring.

The car feels more planted, steering inputs are more precise, front-rear weight transfer and body roll are reduced and the overall driving experience has become more effortless. This is a good start for the season 2014!

Chassis supports – 2nd measurement

2014-03-10T13:37:00.001-07:00

I made a couple of additional measurements motivated by a reader’s comment. Last time in “Chassis supports and door bars – project ready” I used car’s own weight to bend the front and rear downwards. This time I put weight on the door sill and measured the bending that way.

Here are the results:

Weight 70 kg, without door bar. Left: 0,35 mm. Right 0,35 mm.

Weight 70 kg, with door bar: Left: 0,27 mm. Right 0,27 mm.

Weight 100 kg, without door bar. Left: 0,51 mm. Right 0,49 mm.

Weight 100 kg, with door bar: Left: 0,39 mm. Right 0,40 mm.

Conclusion is that door bars reduce bending 18-23 % when measured with 70-100 kg weight. Sounds nice, doesn’t it!

Seriously, deflection with 100 kg is less than half millimeter measured from the height of windscreen frame. Bars seem to work and they give some extra stiffness to old car’s chassis.

More NA POWER part 4: B6ZE cam specs and cam timing

2014-02-22T23:09:00.002-08:00

See also the latest post in More NA POWER! Part 5: 100 bhp per liter in 1.7 liter B6ZE

It is hard to find documented data about the effect of cam timing in B6ZE. There are some general rules, though. Solo Miata's Randy Stocker has written in his site that 1.6 liter Miata engine with stock cams benefits from 6-8 deg retardation, if you are looking for max power. Advanced timing gives better torque to mid and lower revs.

As a general rule increased overlap moves torque into higher revs and decreased overlap gives better torque in lower revs. Explanation is that overlap improves gas exchange in high revs but decreases vacuum in low, which results in lower intake velocity and poor mixing.

For cams in general, a couple of rules apply. Increased lift increases flow across the power band, but extremely high lifts (1,5 times the original, maby) can make intake velocity to drop in low rpm. Increased duration moves power band higher up at the expense of lower revs.

B6ZE WITH STOCK, 264/9 AND 272/9 CAMS

So what happens in real life with B6ZE? Here are two examples. Baseline is from Import Tuner Magazine's archives (intake, exhaust and JR cat). Real life examples are from two Finnish private engine builders, both measured at the same dyno. Graphs are in rear wheel figures. Pay attention, don't concentrate on the numbers! Note how the torque curves look like and where the power starts to drop.

Nro 1 specs: 79 mm high comp pistons (1.64 liter), 3-angle ground stock valves, mild street porting port matched intake manifold, 4-2-1 header (origin unknown), stock cat, sports exhaust, afm delete, stock 56 mm throttle body and 264deg/9mm Schrick cams (German street and racing cam manufacturer).

Nro 2 specs: 81 mm high comp pistons (1.7 liter), 3-angle ground stock valves, mild street porting, port matched intake manifold, Racing Beat 4-1 header, high flow cat, sports exhaust, afm delete, stock 56 mm throttle body and 272deg/9mm Toda Racing cams (Japanese).

First I must note, that there is an odd dip in Nro 1’s torque curve. I think that could be sorted with some map and/or intake tuning.

Some observations:

- Schricks start to pull as low as the stock cams

- Torque stays up about 1000 rpm higher with Schricks (measured at a point where still 95% of max torque occurs)

- 95% of max power at 6800 rpm with stocks and and at 7300 rpm with Schricks

- Todas start to show some peakiness, as they start to pull hard from 4000 rpm

- Todas keep torque up until about 7300 rpm (95% rule)

- 95% of max power at 8000 rpm with Todas
- All three engines are running with stock intake manifolds and throttle bodies

- Torque/displacement-comparison shows no significant increase in max torque, but increased flow in high revs pumps power up

SAME CAMS – DIFFERENT TIMING

Here is a demo how timing affects the torque and power. Test was done with engine Nro 2. You can see that increased overlap (from 8 to 26 @ 1 mm) makes higher numbers from mid to high revs. But what really happens here? In theory bigger overlap should give better flow in higher revs. Max power gains are moderate, only about 5 rwhp. Torque gains are significant, but they are in mid revs. Retarded timing was also tested. It slightly dropped torque between 4k and 5,5k, but had no effect in high revs.

Obviously engine has reached its maximum torque, about 140 rwNm, in current setup and flow reaches its limit at 6750-7000 rpm. What happens when intake cam is advanced, in this case 9 degrees, is that dynamic compression increases. Advancing intake means that valves open earlier and also close earlier. Early closing means that there is more cylinder volume to be compressed, thus higher dynamic compression. More compression -> higher thermal efficiency -> more torque.

CAM TIMING CHARTS

Here is a collection of timing charts illustrating different cam timing options. It is easy to see overlap in degrees in circular timing charts. ‘Valve lift versus crank angle’ -charts demonstrates overlap in millimeters. If you find this information useful, please leave a comment!

CONCLUSION

More torque requires more flow. In reasonably tuned hot NA engines practical maximum torque per liter seems to be in 110Nm/l ballpark (in crank figures for 'hot street tune’). High torque in high revs means high power. To keep torque up above 7000rpm is a true test for engine’s, and B6ZE's, breathing abilities. For that, I would suggest, you need unrestricted (preferably tuned) intake and exhaust plus high flowing cylinder head with larger valves and 280 deg or bigger cams.

See also More NA power part 3!

Chassis supports and door bars – project ready

2014-01-26T00:44:00.000-08:00

Chassis supports are now ready and welded in. Door bars still need to be painted. Templates were accurate enough to make the final fitment easy. The biggest effort was cutting the 3 mm steel plate with angle grinder. Top looks wasn’t the priority this time.

I was lucky to get help from a fellow race car builder who suggested a couple of smart changes: to add triangle plates, use sturdier tube for door bars and make them removable. It’s a street car after all. Door bars are made of 38x3 mm steel tube and bolted on to the support in the front and to the roll bar in the rear.

The idea was to weld the door bar front mounts as high as possible, and still keep the car entry easy.

And here are the results: before and after comparison. Bending reduced roughly to the half. On the road chassis feels more solid and car responds to steering inputs crispier than before. In general it felt like new set of stiffer shocks was installed. Shakiness and 60 mph shim are also gone. Am I satisfied? Yes I am. It wasn’t realistic to expect bending go down to zero. Current situation is a clear improvement and stiffer bushes are next on the list.

Chassis support preparations

2014-01-09T08:57:00.003-08:00

In previous post I wrote that no deflection was noted when measuring “O” and “P”. That was incorrect. Once the rear was jacked up deflection in “C” and “D” increased about 2 mm. In my notes I had written that “it was difficult to do measure “O” and “P” accurately (alone with measure tape…)”. So in the future let’s just concentrate on “C” to “F”. Also slightly loose roll bar bolts could play a role here. Oh well, I must tighten the bolts for next round.

Here is a photo from miataturbo.net (http://www.miataturbo.net/race-prep-75/some-seam-weld-photos-59541/page2/#post761185) forum. There is a great thread about race prepping the chassis. I draw my supports in black. Number one connects floor to the sill and side frame, and number 2 connects fire wall. I am not going to take the dashboard out to make things easier…and harder.

So far I have made models from 1 mm thick aluminium sheet that I found from scrap bin. That is why there are odd holes. The idea is to make the final support (support 1) from 3 mm thick steel and weld it in. I’ll also add a traditional triangular steel sheet (support 2) to the corner.

Stiffer chassis for Miata - please

2014-01-06T09:31:00.003-08:00

Believe me, I have carefully studied all the existing methods of getting Miata’s chassis stiffer. The result is that there are as many solutions as there are car builders. Frame Rails, Frog Arms, butterfly brace and front/rear sub frame braces are all marketed to make Your Miata more solid. Well, they most certainly do so, but would they help me to deal with my “chassis issues”?

To find out where my Miata’s chassis flexes I decided to make a series of measurements. I used a “jack it up” method. This was basically the only way to use enough force to make the chassis bend and twist. The conditions are static and they do not simulate actual driving situation, but the measurements give an overall picture how the chassis reacts.

Here is what I found out. Rear is well attached to middle section (the floor and center tunnel). Front instead isn’t. For some reason the front bends down when front wheels are jacked up. Pivot point is more or less where the floor and door sills end and fire wall begins. Chassis also twists. Deflection was measured between six different points. “O” and “P” didn’t change at all and that is where I reasoned that the “rear end was stiff” (Correction: "O" and "P" deflection was about 2 mm once the rear was jacked up. Some error and uncertainty could have come from loose roll bar.) Changes in the other measures are shown in the graphs. Bending is quite heavy. 7 mm deflection in the height of the find screen frame means the front is bending down about 4-5 degrees.

The following pictures show deflection when only on side is jacked up. This time I used a dial indicator for improved accuracy and to verify my rougher tape measurements. It was surprising to find out what kind of an effect the lifting point has. This was another proof that the problem was the weary connection between the middle section and the front.

Conclusion:

Because my Miata’s chassis behaves like this I believe that neither Frog Arms, Frame Rails nor bolt on roll cage will work. Why? Because they don’t attach the front to the rest of the chassis. (See first picture in this post.)

My plan is to first weld a couple of supports to the chassis that connect floor, door sill, fire wall and front chassis. Here is the first template fitted in. After that I will add door bars that connect front and rear. This should help!

Last I must emphasize that I am not building a race car. With this modification I am hoping to get some extra stiffness so that future modifications to suspension can have their full effect.

Track fun from past years

2013-12-26T02:30:00.000-08:00

It is amazing to watch old track videos and realize that nothing major has happened. Especially when bunch of eager amateur weekend racers want to show their best, someone should definitely hit a barrier or some other obstacle. Well ok, sometimes that did happen but luckily no one got seriously hurt!

I have selected here a couple of videos from the past seasons for you to watch. Back in 2008 youtube had only limited capacity for video uploads and that shows. I filmed the earlier videos with a Panasonic compact camera. It recorded quite decent 480p video, but it had to be heavily packed to make it fit youtube’s limitations.

Hope you enjoy!

This was filmed during Radalle.com track day in 2008. These events are open to everyone and usually very crowded. Lover than average video quality, noisy audio but lots of overtaking with 132 hp Miata!

Best parts in first 5 minutes.

- Mitsubishi EVO, Mk1 Supra, Opel Omega, RX-7, Porsche 944

http://youtu.be/f0tbbV3bmUI

Screaming 8000+ rpm single lap from 2010! Revlimiter was set to 8500 rpm since engine was still making good power up there and I got away with fewer gear changes. Very nice engine tone from open cone filter and aluminum intake plumbing, average 480p video quality and some tire squeal.

http://youtu.be/uY1DJn1bRdc

Open racing practice in 2012. This was my first video with multiple angles. Nothing really special happens here, some corner exit power slides, one mild-ish throttle tap drift at 3:32 and two race cars. Put HD720 on!

- Legends race car, Citroen DS3 R3 rally car

http://youtu.be/1VB9yoYNxrg

Miata Club of Finland’s track day at Alastaro in 2013. A fellow member wanted some footage of his driving, so I tried to keep up with him. 100hp/Nm extra makes a difference! This was also a test for a chin mounted Hero2-camera. Put HD on!

http://youtu.be/skQeCtts8Ms

Radalle.com track day at Motorpark in 2013. This stint turned out to be a true -90’s battle! At 1:20 I let a Ferrari 348 TS pass me and then followed it. Eventually we caught a Honda Civic VTi with slightly tuned B18 that was competing in Time Attack Club –class. We passed it and after that also E34 5-series drift car. Audio quality is not good. Hero2’s internal microphone is poor and open top makes quite lot turbulence. Something to be dealt with…

http://youtu.be/hbE9ZjAYQpE

Need 4 Suspension

2013-11-26T13:26:00.001-08:00

Let's face the fact; my MX-5's suspension is stock. Yes, I have done some improvements and installed a couple of upgrades but neither Koni Sports Kit nor a set of H&R anti roll bars really mean it's race ready. The car is drivable and pretty fast by all means and the whole package is in balance on the track. Obviously I have learned to adjust my driving style according my current setup. I could benefit from having 100 extra horses under the hood, but after that current balance would be gone. Further engine mods have to wait for a while then.

The best single handling mod so far has been my current tires. That was no surprise! Before that it was racing inspired wheel alignment and before that Koni’s sport suspension.

Real need for further upgrades came along with stickier tires. My current Yokohama AD08s offer a lot more grip compared to Toyo T1Rs. Higher grip has resulted in increased compliance of the suspension. Increased roll and change of the tire alignment in fast corners are the symptoms. T1Rs in the front wore evenly but AD08s are starting to take the heat more on the outside of the tread. So, what is happening here? Obviously 22 years old stock bushes are starting to give in and my camber angles are “dialing in”.

The other issue is decreased chassis rigidity. Front and rear are starting to feel even more detached than before. When a pot hole or a kerb on track is hit, a horrible wobble occurs. If car is jacked up from only one point the flex can be seen with bare eye when the door seams are not in line anymore.

Here is what I am planning to do. First I am going to get the front and rear attached again by installing door bars. After that polyurethane bushes and some sort of coil over solution have their turn. Stiffer bushing and springs won’t have their full effect without increased chassis rigidity. I want my suspension to do the work instead of the chassis.

MUR Services

2013-11-26T13:07:00.001-08:00

MUR Services tarjoaa:

- Huolto- ja muita palveluita Mazda MX-5/Miata -autoihin
- KMS Engine Management Systems - Van Kronenburg ECU:n perussäädöt

Yhteydenotot sähköpostitse:

murservices(a)hotmail.com
MUR Services
Helsinki
Y 2583651-7

MCF meet in Hyvinkää

2013-07-12T01:54:00.000-07:00

Miata Club of Finland arranged 2013 summer meet in Hyvinkää about a week ago. I took a few pictures of some chosen cars that showed up.

CLEAN BLUE NA

Two early 90’s NA Miatas in blue caught my eye immediately. The other was very nice and clean on Enkei Apache II rims. Tein suspension gave it a nice balanced stance and combination of paint, rims and some details was really working!

SLAMMED BLUE NA

The other was built with different goal. It was slammed and had a racier look. Nice details were there also and pink with blue seem to work together nicely. Still, highest points go to center console decoration!

NA Miatas - they are simply fabulous!

Season 2013 starts

2013-05-11T12:37:00.000-07:00

First ride and first photos for this season!

More NA POWER part 3!

2013-03-24T10:04:00.000-07:00

PREVIOUSLY ON "MORE NA POWER..."

Let’s drill deeper into tuning a naturally aspirating B6ZE for more power. Until now we have done all the basic bolt-on upgrades in part 2. Better flowing intake and exhaust are in. Ecu has been left stock with only mild adjustments to AFR and ignition timing. These modifications gave us about 85 crank hp/liter from 1597 cc engine.

See also 'cam specs and timing' in More NA POWER part 4.

ECU UPGRADE

Next there is the programmable aftermarket ecu. Nowadays many have opted for Megasquirt which is an affordable choice with good online support. Aside the make of ecu, what matters is that with fully programmable ecu it is possible to fine tune ignition and fuel tables for every setup. A chance to get rid of possibly restricting AFM or MAF is also an added bonus. Here is a dyno comparison which shows nicely how some 10 extra hp can be found by getting rid of stock AFM and tuning the ecu. I must mention that ARC intake was also installed, but I have no idea what kind of an effect it would have alone. 90 crank hp/liter is pretty nice for B6ZE with stock internals.

INTERNALS

Most of high power B6ZEs are equipped with 80,5 mm (or so) diameter pistons. Larger bore increases displacement to about 1700 cc and high compression pistons also rise compression ratio from stock 9,4:1 to 10,5 or even 12:1 –depending on the piston design. Both serve the same purpose: pumping torque up from bottom to top. And then there is The Flow. In order to make high power in high revs the head must flow properly. In addition either exhaust or intake must not form a bottleneck for the gas flow. Bigger cams, larger valves and head porting all serve the same goal: better exchange of gases in the cylinder. And don’t forget high quality, light and balanced internals like valve train parts, conrods, crankshaft and flywheel, if you also want your engine to last long in high revs. Here were the starters.

SAME GOAL, TWO PATHS...AND TWO RESULTS

At last we come to main course. Here are torque and power figures from two different engines. They are plotted into same graph and presented in wheel Nm and hp to make comparison easier. Original data for both is taken from chassis dyno graphs presented in wheel torque and power. So the only “manipulation” that I have made is torque conversion from lbft to Nm for the Engine nro 2. Power was calculated from torque in both cases. Still some consideration is required! I don’t know in which conditions Engine nro 2 was originally tested, what type of dyno was used and what was car’s actual drivetrain setup. So the figures presented here are not 100% comparable. “Are not 100% comparable”, what does that mean? It means that I, or anybody else, can’t state that engine nro 2 is “exactly” 10-20 Nm stronger than engine nro 1. But yes, nro 2 outflows nro 1 above 7000 rpm. That is “sure”.

Engine nro 1’s specs:
• Toda 81 mm bore pistons (1720 cc)
• Carrillo A-beam rods
• Balanced stock crank
• Street ported head, stock size valves, 3-angle valve job
• 272 degree cams, 9 mm lift
• Stock intake manifold fitted to throttle body and head
• Stock 1.6L throttle body
• 4-1 Racing Beat header, 2” pipe after collector

Engine nro 2’s specs:
• Maruha (Mahle) 80.5mm bore pistons (1700 cc)
• ETD Rods
• Knife-edge Crank
• Race head with oversized valves (ported and polished)
• 284 degree race cams (possibly 10-12 mm lift)
• Maruha ITB
• Racing header, 2,5” pipe after collector
• (This data is from winkyl’s engine taken from clubroadster.net and youtube.com.)

CONCLUSION

As was mentioned before, the aim of the comparison is not to stare at the numbers. The shapes of the torque curves are the most interesting part. Power band for both engines starts from 3500 to 4000 rpm. It doesn’t mean that nothing happens below that. There is more torque at 2500 rpm than in stock engine at 5500 rpm. The biggest differences between these two power plants are above 7000 rpm. Nro 1’s torque starts to drop from 6750 rpm and power reaches its peak at about 7000 rpm. Winkyls’s engine keeps torque up until 7000 rpm. And more importantly, the angle of descent is gentle enough to keep power rising until redline at 8000 rpm. I wonder what figures would be with higher redline!

This comparison isn’t the best demonstration of camshafts’ effect on torque and power since the other engine is equipped with stock intake manifold while the other runs on ITBs. Stock manifold possibly forms a bottleneck for airflow. However, the reason for broad power band up to 8000 rpm+ in engine nro 2's case is evident: High flowing head, larger valves, 284 deg. high lift cams and ITBs are the main factors.

See also:
More NA POWER part 1! and
More NA POWER part 2!

Ahvenisto lap comparison – 3 times NA Mazda MX-5

2012-12-28T11:19:00.002-08:00

THE TRACK

I’ve spent most of my track time in Ahvenisto Racing Circuit. It is by far the most demanding race circuit in Finland. It’s technical, it’s beautiful and it’s legendary. And perhaps it’s world famous already since Captain Slow visited it with Mika Häkkinen – a Formula1 double world champion. http://www.youtube.com/watch?v=2bmqdnx5R1U

Ahvenisto Racing Circuit is built in late 1960’s and that makes it a bit different. It’s like Norschleife’s little brother. Most of the time it’s either uphill or downhill and there are no real runoff areas. Difference between the lowest and highest point is 30 meters (100 feet). It’s pretty much for a track that is roughly 3 km long. No picture can communicate track’s true profile. Incar videos give a hint but this track is something one must experience personally.

Enough with the praise. Here is some data extracted from this video http://www.youtube.com/watch?v=Ft3Cx6fHrhI&feature=youtu.be. Here is some basic steering, throttle and brake input data to tell its own story about track’s profile.

Lap time (dry weather): 1´38 s

Steering wheel straight forward: 22% of the time

Wide open throttle: 43%

Foot on brake: 17%

Throttle partially open: 40%

Longest time throttle is continuously 100% open (including gear changes): 17 s

THREE CARS, THREE LAPS

Next follows a brief analysis of three laps done by three different MX-5s. They are in many ways similar but at the same time totally different. I will call them Silver, Red and Green. They all are from early -90’s with B6ZE engine.

Red’s specs:

- About 120 crank hp, completely stock engine with silenced decat pipe, 7200 rpm rev limiter

- 4.1 final drive with torsen type-2 differential

- BC Racing BR coilover suspension, Energy Suspension poly urethane bushing, stock stabilizers

- Track spec wheel alignment

- Yokohama Advan AD08 tyres, 205/50/15

- No roll cage or roll bar, P5 frame rails
- Lap time 1:39.5

Silver’s specs:

- About 130 crank hp with intake and exhaust mods, 7200 rpm rev limiter

- 4.3 final drive with Kaaz 1.5way L.S.D

- Tein SuperStreet coilover suspension, full set of poly urethane bushing, stiffer front stabilizer (22 mm diam.)

- Track spec wheel alignment

- Toyo Proxes R888 tyres, 195/50/15

- Full roll cage, interior strip down to compensate cage’s extra weight, plus no air-con and power steering.
- Lap time 1:38.5

Green’s specs:

- About 160 crank hp, 8300 rpm rev limiter.

- 4.3 final drive with Kaaz 1.5way L.S.D

- Koni Sportskit suspension, stock bushing, H&R stabilizers front and rear

- Track spec wheel alignment

- Yokohama Advan AD08 tyres, 205/50/15

- 6 point roll bar
- Lap time 1:37.5

Colors painted on the track illustrate gears: light green is 2^nd, yellow is 3^rd and orange is 4^th. Numbers in the boxes are “gear”/”revs” and speed below (in kph).

Okay, what does this tell then? First take a look at the gear changes. Red changes gear 6 times per lap because of the wider total gear ratio (4.1:1 differential and large tyres). Silver must change gear 10 times per lap (shorter overall gear ratio). Compared to Silver, Green’s total gear ratio is similar but Green benefits from higher rev limiter set to 8300 rpm - hence 6 changes per lap for Green. Silver’s extra two up and down changes both come in bad places. The first is before turn 3 where all the concentration should be aimed on upcoming left turn heading uphill. The second is between 8 and 9, on an uphill, not the best place to shift up either.

Next take a look at the table with cornering speeds. It’s interesting to notice that all three have almost identical cornering speeds in 5 turns out of 11. Track is very technical from turn 6 to 10 and the trick is to keep up the momentum. It’s basically one big complex of turns where clean driving and good handling is rewarded. In paper Silver should have highest apex speeds as it is equipped with a set of R888’s.

After turn 10 it’s flat out for a while. Keep the throttle floored through turn 11 and get your top speed measured before going on brake and diving into turn 1! This half of the track from turn 10 to turn 6 holds all the straights - or not so curvy parts. High powered cars gain some ground here but are usually caught between turns 3 and 5 if drivers aren’t familiar with the track. Turn 11’s apex speeds show Silver’s more favorable gear ratio and power over Red’s.

Technicality of the track, the effect of gearing and apex speeds were three most important things I wanted to highlight here. Power isn’t everything in Ahvenisto and skillful driving is a key to success. Please continue checking the graphs by yourself – there is plenty of more to be found!

Practice, practice, test and practice…

2012-06-12T12:58:00.001-07:00

This season’s first handling modification was a set of H&R adjustable anti roll bars. There is two possible settings in front and three in the rear. I decided to try something in the middle. Well, I couldn’t do that because while lying on the garage floor (car was jacked about 30 cm of the floor) all my muscle seemed to have disappeared somewhere and the front was set “stiffer”.

Testing took place at Ahvenisto Race Circuit. With stiffer anti roll bars corner turn in felt immediately more responsive and weight transfer was noticeably quicker. This is what these parts are for and they were doing their job nicely. However mid corner- and corner exit oversteer was kicking in. One had to be very careful with gas. Let’s see how milder rear setting affect…

Wednesday is the day for free practice session for everyone. There was a couple of modern formulas (F3 class?) and older ones also. Bikes had their fun for the first half of the day and left the track for cars when it started to rain.

I managed to drive both on dry and wet track. I really enjoyed driving in the rain because limits could be found at lower speeds. The other agenda was to shoot some film and test new Hero 2 –camera. In car pictures shown here are from testing different helmet mounts. “Chin” is a bit too low and I believe that “fore head” makes a better angle.

Just can’t wait for the next visit! http://www.youtube.com/watch?v=1VB9yoYNxrg

More NA POWER part 2!

2012-06-12T01:30:00.001-07:00

See also 'cam specs and timing' in More NA POWER part 4.

The efficiency of an engine can be divided into three main factors: Volumetric efficiency (Ve), Thermal efficiency (Te) and Mechanical efficiency (Me). Te and Me stay more or less constant when basic bolt-on engine modifications are made. (For more info check: http://www.fordscorpio.co.uk/efficiency.htm)

Te tells how well engine makes use of the energy that is produced when fuel is burned in the cylinder. Compression ratio and combustion chamber design affect this factor. Higher compression ratio -> higher Te.

Me tells how well engine transfers energy from burned fuel into rotational force that turns the crankshaft. Higher inner and outer mechanical losses means lower Me. For example lowering the masses of rotating engine parts lowers internal inertia. Instead of using power to accelerate engine internals more power is fed through the crankshaft to the transmission to propel the car. Lower internal inertia and other internal losses -> higher Me.

Volumetric efficiency is what one is improving when basic bolt-ons are installed. Ideally, during the intake stroke, cylinder would “suck” in as much air as the mechanical volume of the cylinder is. In B6ZE’s case this would be 399.25 cc. If the volume of the air “taken in” is under that, the Ve is under 100%.

Naturally aspirating engine works optimally (= Ve is close to or even over 100%) in a narrow rpm range. Variable valve timing, valve lift and variable geometry intake designs are used to widen the optimal rpm range.

Ve tells how well the gases flow through the engine. First air flows through the entire intake tract to make its way into the cylinder. After work stroke exhaust gases flow out of the engine through the entire exhaust system. If there are flow restrictions either in the intake or exhaust side of this “gas pump”, Ve is decreased. It’s that simple! Take out restrictors and Ve is increased. Higher Ve -> higher torque. The trick is to know which restrictor should be eliminated first. Throwing in a race cam to an otherwise unmodified engine does not improve Ve at all because flow is heavily held back by other parts of the engine.

That was basic introduction to combustion engine’s efficiency. Now back to business.

Graphs shown here are from two different sources: Import Tuner Magazine and my own engine build. Both are lacking a baseline graph from a completely stock engine. Import Tuner’s stock engine’s torque curve is an estimation done by me (some discussion about it in my previous post) and “Einspritzer motor” is a copy of some kind of a manufacturer’s graph from some German site. All figures are presented (and converted, if needed) in crank torque and hp. To make comparison easier all curves are presented in similarly scaled graphs.

When I compare Import Tuner’s (IT) findings to my own many similarities and some differences can be found.

First similarities:

- Stock intake and exhaust (together) form a flow restriction worth for 10-20 Nm and 10-15 max hp. That is 10-15 % power loss across the entire rpm range.

- Stock intake makes about half of that. High quality cone filter is a must compared to stock airbox. Snorkel’s diameter is small and in stock airbox there are too many tight bends. Just make sure intake air is as cold as possible, at least not hotter than with the stock airbox.

- Stock engine benefits from a better flowing and better tuned exhaust manifold and gains worth for 5-7 Nm can be found. A little torque is lost below 3500 rpm.

- Both engines start losing torque above 5500-5750 rpm. Reason for that is cam specs (duration and timing).

Then differences:

- IT’s engine made its max hp at 6500 rpm and after that power dropped quickly. Exhaust manifold improved flow but torque curve’s form stayed more or less the same.

- My engine showed no signs of choking above 6500. Reason for that is a bigger AFM that outflows the stock unit. Stock AFM limits air flow to previously mentioned 165CFM, which is about 130-135 crank hp. Exhaust manifold’s true potential can be seen above 6500 rpm because stock AFM isn’t there to limit the flow.

- IT’s engine made about 10 Nm more low- and midrange torque. I have no real explanation for that. Maybe high flowing cat does its job there or drive train losses were less than 20% that was used for calculations. If losses were 18% instead of 20%, max figures would have been 153Nm and 128hp.

Enough with the speculations! My point here is not to stare at the numbers but the shapes of the curves. They will guide you to think of the right things.

More NA POWER for 1st gen Miata, Part 1

2012-05-18T06:00:00.001-07:00

What interests a gearhead the most? Getting more juice out of the motor, of course. So lets drill deeper into B6ZE's potential of producing more than 136Nm/116hp - in naturally aspirating form.

Q1: Why only 136Nm and 116hp?
- In 1600cc engine that makes 85Nm and 72,5hp per liter. That is not the poorest result if you see the big picture. Late 80's engine management tuned for "what ever gasoline", low compression ratio (9.4:1), super silent stock intake and exhaust, mild cams and relatively standard valves. Clearly a healthy dose of performance potential is hidden somewhere there.

Q2: Why so small torque?
- Displacement is only 1600cc, so it will never be a torque monster of any kind. Compressio ratio (CR) is only 9.4:1 and stock ignition timing is far from wild. Adding 4deg ignition timing can produce 5-8Nm extra torgue below 5500rpm (with basic intake and exhaus upgrades). Check dyno graph: http://www.mymazdamx-5.blogspot.com/2007/05/tehomittaus-dynamometriss.html

Q3: Why torque peak is in relatively high rpm, 5500?
- Mazda wanted to make a revhappy motor. That was basicly the only way to make such a small motor enjoyable and at the same time produce decent performance, with the right gearing of course. Stock intake manifold and cam specs are the main reasons for torque peak to occur at 5500rpm. Intake manifold's runner lengths are tuned so that the resonation takes place at around 5500rpm. Stock cams make the airflow (edit: not airflow, but volumetric efficiency, Ve) reach it's peak between 5500 and 6000rpm. It is intetersting that this can also been seen in boosted motors with original intake manifold and stock cams.

Q4: What restricts the top end power, essentially the air/exhaust gas flow?
- Through the whole rpm range there are two basic restrictions: intake (air box and filter) and exhaust (original cat back exhaust pipe). Torque curve come's up about 5% from bottom to top with each of the basic mods: high flow cone filter and high flow cat back exhaust. Import Tuner magazine has done excellent dyno testing that can be found here: http://www.importtuner.com/powerpages/impp_0808_1993_mazda_mx5_miata/
NOTE that baseline is not showing true stock motor rear wheel performance because catalysator was busted. Guys put a new one in but did not bother to make a new dyno run. So, I would say that estimated stock crank hp in that particular motor was about 112 hp or so (89-90 rwhp with 20% drive train loss).
- Flapper door style air flow meter (AFM) is small and can flow about 165CFM (cubic feet per minute) in atmospheric pressure = naturally aspirating motor. Randy Stocker has done some flow testing (http://www.solomiata.com/airflowmtr.html) and with 90% volumetric efficiency at 6500rpm the peak intake flow rate becomes 165CFM (http://www.mk5cortinaestate.co.uk/calculator3.php). This is enough evidence for me to come in the conclusion that stock AFM restricts power to about 105rwhp (about 130 crank hp) as seen in Import Tuner's dyno testing: http://www.importtuner.com/powerpages/impp_0808_1993_mazda_mx5_miata/total_cost.html.
- Stock header get's small above 6500rpm if all the other basic bolt on mods are made, including larger AFM. Graph shows significant gains from 6500 to redline (pictures are really poor, sorry...): http://www.mymazdamx-5.blogspot.com/2008/05/tehopenkitys-nro-2.html
- Unbroken stock cat can support at least 155 crank hp. It's highly recommended to get rid of it, but I would do that last.
- And last there is The Flow: the cylinder head, valves, cams, throttle body and intake header. More about these later.

No pictures at the moment, only hard core text. Links should give you something to watch for a while. Better quality graphs, torque curve comparison and further analysis coming up in Part 2!

Yes, it's still active!

2012-04-30T03:42:00.001-07:00

I finally reactivated my account and noticed that it has been almost two years since last update. First, thanks for all of you who have been following this blog! I discovered that this new version can tell some stats about visits and dispite my lack of time there has been some readers' activity.

So, what's new? About year and a half ago I had a spun conrod bearing. That was no biggie and hardly did any damage. Oil starvation during hard driving on the track caused that more or less. Remedy: racing oil pan baffle that keeps oil under the snorkle at all times. Having the engine opened it was also a convenient time to finish all the other stuff that was left half way the year before.

2011 upgrades:
- 160000 km driven short nose cranck -> factory new long nose cranck (balanced)
- Stock rods -> Carrillo A-beam rods
- ACL Raceline bearings (main and conrod)
- 3-angle valve job and valve train rejuvenation
- Toda adjustable cam gears
- DIY CAI with pressure box: inlet pipe from the "mouth", pipe diameter 100 mm -> 76 mm -> 60 mm -> stock TB
Result: Fully maintaned, reliable, in tune B6ZE. More of these will find their way here soon.

Thus summer 2011 was filled with carefree and revarding moments on and outside the track:

Another nice video for you. White gen 1 Miata emits very nice exhaust note (3:00 on, and 4:30)!

Night out

2010-06-25T22:19:00.001-07:00

Spring 2010 updates

2010-05-07T22:45:00.000-07:00

- The same pattern is repeated every year. In the autumn when the season ends I promise myself that no great modifications will take place next spring. But somehow it always happens that during long winter months some odd parts are piled up in the garage. At the moment I have five projects waiting to get started: oil cooler, Autometer 5" tach (10k scale), fire extinguisher mount, front strut brace and wheel alignment reset.

- All of this is made in the name of better handling, increased durability and safety. I would like to squeeze another one or two seconds from my ordinary "hot" lap at Ahvenisto racing circuit.

Motivation and blue skies for the winter

2010-02-12T06:23:00.000-08:00

- Here is a nice blog for those who think small japanese fourbangers are smart pieces of engineering and cool to play with. Yes, its about Toyotas and souping up 4A-GEs. The basics of naturally aspirating engine tuning is the same and all the good advice written here apply to our B6- and BP- motors.
http://www.hachiroku.com.au/blog/?tag=ae86-tuning-guide
- And this is how all track races should look like! Tight matches, close (almost) contact and high pitching engine growl! Yes please:
http://www.youtube.com/watch?v=f3dTkMDQmC0

Hot and cold

2010-02-12T06:08:00.000-08:00

- Now when the Finnish nature shows its best and there is plenty of snow even in the south most parts of Finland, it’s a bit hard to recall all last summer's overheating issues. But that's the way it was only three months ago.
- I was leafing my old notes from previous driving seasons and to my surprise there was one or two bullets about high engine temperatures already in 2007 and 2008. Back then the only instrument to monitor coolant temp was the car's original temp gauge. Most of time needle stands straight up and too high temp can be observed as a slight tilt towards northeast.
- As I found myself spending more and more time on track I thought it would be a good idea to install a set of real instruments on top of dash. So I went to get two A'PEXi EL-series gauges: water temp and oil pressure.
- I can confirm that NA's (at least in my car) original water temp gauge is there just for show. Original's "normal temperature" = needle straight up means anything from 60-110 deg C. Well, actually that is just fine, but the scale is too rough for my purposes. On the other hand the oil pressure gauge in my 1991 MX-5 is decent. The only problem is that it hides behind the steering wheel, because mine is a bit smaller than the original.
- Now I know that on track, if the day is warm – say +20-25 deg C, coolant temp rises to 100-110 deg C after five to eight hard laps. Even on very cool autumn afternoon, outside air temp showing little less than +10 deg C, the engine heats immediately to 95 deg C. And that's not all, oil temp rose to 110 deg C plus plus. How much above 110? I can't tell any better because the scale ended there.