My Miata is a 1991, BRG Special Edition, 1.6 engine. This is my second Miata. The first I ordered three months before the first Miatas entered the U.S. I received the third one the dealer received, a red "A" Pkg. Drove it for three years, loved it and sold it for about what I paid. I wanted the ‘91 BRG model since it first came out and finally about two years ago I purchased one.
It is absolutely stock in appearance but I have done a few things to pep it up. The foundation of my power improvement is the Wipple Supercharger Kit from BEGI. I will discuss the following subjects which may be of interest to you if you are considering some additional power for your Miata:
If you have read some of the other articles on the internet you may fear tackling the installation of this kit. I have no professional mechanical experience but did work on my own cars when I was younger. I did not find the installation to be extremely difficult. It did take longer than advertised. However, I took my time, but even a skilled mechanic would be pressed to do it in the six to ten hours advertised. I installed the kit, working with my two boys who were home from college, over the Christmas holidays (Dec. 1995). Installation will require a standard mechanics tool set with both SAE and metric sockets and wrenches. The factory shop manual is worth the price. Try AUTOMOBILE FACTORY SHOP MANUALS, HELM CORP., 1-800-782-4359 for best price and mail order.
Upon receiving the kit, first, I laid all of the parts out on the floor and checked them against the parts list. This done, the boys and I went step by step through the instructions with the car in the garage so we had an overall understanding of what we were going to do.
Next, we went exactly by the instructions which are numbered, step by step, to do the installation. It starts with all of the parts to remove from the engine and then goes item by item with numbered steps for each item to be installed: fuel pump, drive pulley, AUTOROTOR, idler pulley, cruse control actuator, air intake system, throttle linkage, intercooler and tubes, boost gage, fuel pressure regulator and ignition retard. By taking it one item at a time and following the steps it is not difficult. Additional pictures and diagrams would be of assistance. Some were provided but additional would make for more complete installation instructions.
The next procedures are start up and setting the timing, and then running through the test procedures to adjusting the fuel pressure regulator for proper fuel mixture. This is all pretty straight forward. The instructions are specific enough that you do not have to have auto mechanic experience to do it. When first looking at the twenty-four pages of instructions and parts list I can understand someone being intimidated. The document length shows what a detailed explanation of the installation is included. Corky Bell, owner and manager of BEGI, keeps the instructions on the computer and as a customer has a question, he updates the instructions with improvements where possible. I am sure the instructions are even more specific and clear now than when I purchased my kit in late 1995.
Was the installation without problem, you ask? No. Here are the problems on which I needed consultation: Two items did not fit properly. First, the supercharger drive pulley that goes on the crank had a different bolt pattern. Second, one of the pipes from the intercooler and the intake manifold on the engine wasn’t right. Upon discussion with Corky, it was determined that for these two items the 1.8 engine components had been pulled from stock and put into my kit. Corky sent the correct parts via overnight delivery without waiting for me to return the other components which I returned the next week.
I did not like that the exhaust pipe heat shield must be dented to keep from hitting. Dent the right place, and the right depth. I dented it too far and it touched the exhaust pipe making a rattle. With some work this was corrected. However, I don’t know of a better way to engineer that installation.
As you can tell from the discussion above, Corky Bell and his team at BEGI are very "customer satisfaction" oriented. Corky is very personable and attentively listens to problems and works with his customer to find the correct solution. He has gone beyond normal support to assist me with my car.
Let me say that the difference between 6 psi boost and 8 psi boost is a lot, a lot! -- It is fast. -- When I raced against a Miata with a 6 psi system without the intercooler, I just blew him away. His eyes almost popped out.
When I completed the installation I had a fairly new set of stock "size" tires. They were of a hard rubber and did not squeal when spinning on the asphalt. This meant I did not realize how much they were spinning when I made a rapid start from stop. It was just over 30 days after completing installation that I realized I had no tread on my rear wheels. I replaced the tires with Yokahama AVS Intermediates in size 205/55 ZR 14. These do not spin so easily as they are two sizes wider and much stickier rubber. I have been driving on them for about 10 months and have not noticed significant wear. Yes, I can spin them if I want, in first or second (see below).
As you may have read in other articles on the internet, the engine has very little noticeable noise during regular cruising. On normal acceleration you can hear the supercharger but it is not distracting. Upon heavy acceleration, you will definitely hear the whine of the supercharger as it spins up. The sound has the whir of a turbojet engine. Not that loud, of course, but that is the sound. I like it, my wife doesn’t. It is noticeably louder when you go to the "additional performance" discussed below. This does not mean it is loud enough to interfere with the radio or talking except under heavy acceleration.
Well, I’m the kind of guy that gets carried away with stuff. I talked to Corky about more power. After several discussions, he sent me a new smaller pulley for the supercharger which he had calculated to give me 10 psi boost. After installation, it reads exactly 10 psi. I mentioned the difference between 6 psi and 8 psi, well the same thing holds true in going from 8 psi to 10 psi. WOW!!!
This was not without some problems.
1) At over 90 degrees ambient, the engine started overheating. I have installed a dual core radiator which is supposed to double the cooling capacity. It is a drop in swap, but cost a couple of hundred.
2) The engine appeared to run out of fuel on the top end under full boost. This caused severe knock. This would lead to engine destruction. There are several ways to attack this problem. I have done two things to make sure the engine is safe. First was to replace the stock 210 cc/min. injectors with 250 cc/min. injectors. I purchased these from R.C. Engineering, (310) 320-2277. This sounds sophisticated but is easy if you have the shop manual. The manual only devotes one page to it; it is only about 4 steps. I have never done anything with fuel injection before and was surprised at the simplicity of replacing injectors. I did it by myself in one evening after work. The other thing I did was to purchase and install the J & S Electronics Knock sensor/spark retard unit ((714) 534-6975. This unit comes from the General Motors knock sensor used on the Saturn. It detects minuscule knock and retards the spark to maintain optimal timing while keeping a safe margin for the engine. It is so accurate that it detects the knock for each cylinder separately and retards the spark for each cylinder as specifically required for that cylinder.
3) The clutch was short lived after going to 10 psi boost. It may have gone out at 8 psi after a while but I did not have any problems until I went to 10. I had the clutch job done professionally. It is the first modification that I have not done myself. I had a Centerforce Dual Friction clutch installed. It has the same clutch peddle pressure as stock but it does hold. You would have to read about Centerforce’s patented centrifugal weight system to see how they do it. Works great!
The other day I was driving down the highway at about 50-60 mph. A Porsche Carrera came along side with his whale tail that lifts when he exceeds some mph threshold and his foot wide tires. He decided to show me why he had purchased a Porsche. Naturally I got on it too. You wouldn’t believe his face when he couldn’t pull away from me. We ran side by side up to about 120 when he had to slow down to exit the express way.
Yes, I love my little car. It now has 80,000 miles. I drive it 60 miles to and from work each day and put about 400-500 miles per week on it, unless my wife and I take it for a long weekend trip to New Mexico or Atlanta (where one son lives).