Replace V8 with Toyota MR2-Make your own supercar

Note: This is the first article in a series of articles on this subject.

For years, I dreamed of owning an exotic mid-engined supercar. Unfortunately, they remained financially out of my reach. I decided that the only way to get it was to make it myself. I have always been fascinated by mid-engined sports cars. It has better handling, braking and traction than a front engine sports car. Even a front engine car with a rear transaxle probably has an optimal 50/50 weight distribution. The weight distribution is like a dumbbell, both ends are heavy, and the center is light, so we call it a “dumbbell car”. This is clearly not optimal for acceleration, handling and braking.

Compare this to a mid-engined car. If you resemble a dumbbell in a mid-engined car, the weight will slide to the center. Now, if you want to make a dumbbell, or if you want to rotate a mid-engined car around its vertical axis (called “yaw” in aircraft terminology), it’s much easier and faster. This is because tire traction does not have to overcome the inertia that the front engine / rear transaxle car gives to both ends of the car. As a result, the car can turn faster and wear less tires. Peak G-force is much higher even in mid-engined cars. In other words, it will be faster around the corner. Due to the increased weight on the rear wheels, the traction of the rear wheels during acceleration is excellent. Curiously, mid-engined cars not mentioned by the car press have many “side effect” benefits.

Some examples:

1) Mid-engined vehicles usually have very short exhaust pipes (compared to front-engined vehicles), so the engine must overcome “pumping loss” and resistance to exhaust from the tailpipe. This means more power. It is lightweight because there are few exhaust systems. Dumbbell cars have no advantage here.

2) The rear wheel brakes make more stops than the front engine car. When you step on the brake, the weight is transmitted to the front wheels. This means that the rear wheels will be unloaded. In front engine vehicles, the front brakes do about 80% of the stoppage. That’s why the rear disc brakes took so long to catch up. They are simply not needed at the rear. Mid-engined cars have significantly heavier rear wheels (usually around 55-60%). When you step on the brakes, the weight moves to the front, so when you apply the brakes, the front can be 50% to 60%. Dumbbell cars get some of the help that mid-engined cars get, but not so much because the engine is still in front and much heavier than the rear transformer.

3) Mid-engined cars do not have drive shafts (except for AWD cars such as the R8 and Veyron), so weight reduction is done here.

Unfortunately, most mid-engined cars are very expensive. Ferrari, Lamborghini, McLaren, Zonda, Koenigsegg, Bugatti, etc. Some of these cars are over $ 1 million! Mid-engined cars also tend to be difficult to work with. Replacing the exotic spark plugs is a major operation. The McLaren F1 requires the engine to be removed to replace the plug.

The area of ​​affordable mid-engined sports cars includes the Pontiac Fiero and the Toyota MR2. In each case, the car was equipped with a 4-cylinder motor. Fieros also got the V6s, but those V6s were a whopping 140 horsepower and very underpowered. In 1990, Toyota redesigned the MR2 and upgraded its power. The base model was 130hp and the high-end turbo was 200hp. This was quite large for a car weighing 2700 pounds at the time.

The new body looked a lot like the Ferrari 348 of the time and looked very good. After all, because it is Toyota, the build quality was also excellent. In 2005 I decided to buy the 1993 Toyota MR2 turbo. I was planning to replace the Toyota V6, which many people have done so far. At about the same time, I discovered that there were some attempts to install the V8 engine on the previous MR2 (Generation 1, 1984-1989 Body Style, or Mark 1). There was also an attempt to install a Toyota / Lexus V8 engine on the MR2 Mark 2. The attempt to mount the V8 on the MR2 Mark 2 was not completed and the project owner gave up. The reason is not clear, but it seems that the Toyota V8 was too long for horizontal placement, even after the car was severely cut and fitted.

As a mechanical engineer who happened to be a mid-engined sports car nut, I was intrigued by the possibility of putting the V8 in the MR2 Mark 2. With a powerful V8 engine, the MR2 transforms into a supercar and delivers supercar performance. .. The Fiero guys have enjoyed replacing the V8 with their own car for years. The Fieros is superior to the MR2 in that it has a large engine compartment and can use a large and long engine like the V8. The Fiero and MR2 all have a transverse engine. Another advantage the Fiero guys had was that the stock Getrag transaxle was bolted to the Cadillac 4.9L OHV V8 from the late 1980s / early 1990s. The later Cadillac North Star is also bolted without the expensive custom machined adapter plate.

In late 2007, another V8 with MR2 Mark 1 (1st generation) was completed by a European man. The car was crazy fast and I made cookies just by wearing a hat. How fun! So, I took a closer look at the previous attempt to install the V8 on the MR2 Mark 2. I noticed that they were trying to “keep it in the family” and use a Toyota or Lexus V8. There was really no good engineering reason to use this power plant. It wasn’t bolted to any of the MR2 transaxles and was too long. The Toyota V8 (engine code 1UZ-FE) used has a length of about 26 inches from the crank pulley to the back of the engine or the bell housing interface. This is an important aspect. Compare this with a stock MR2 engine like the 2.0L 3S-GTE turbo motor with a 20 inch limit dimension. This dimension is important because it fits between the unibody pseudo-frame rails on the MR2 chassis.

I decided to take a different approach. I started looking for a V8 engine that fits the MR2 chassis on the internet. If possible, do not cut, or just cut the MR2 unibody a little. My requirement was that it was a V8 with at least 300 horsepower, it was available, cost less than $ 5,000, and was short and narrow enough to fit the MR2. I succeeded in finding it. Audi has an interesting habit of making a very short V8. They do this because they want to use the Quattro drivetrain, but at the same time they don’t compromise too much on handling. Audi seems to prefer a longitudinal engine and transmission arrangement to a transverse engine and transmission. The Quattro drivetrain includes a driven front axle that must be located behind the engine. If the engine is too long, it will be too heavy in front of the axle, so shorten the engine to make up for it. This has the added benefit of being able to install this engine in a small car that Audi originally intended to have a four-cylinder power plant. For my purposes, I found that the Audi V8 engine from 1991 to early 2000 had marginal dimensions of about 20.6 inches in length and about 29 inches in width, and did not include headers or other easily removable items. ..

I bought an Audi 4.2L V8 (engine code ABZ) and transaxle in 1997 and started working on the project. Unfortunately, after a lot of trial and error, I finally decided that the Audi V8 wasn’t suitable for this engine swap. The problem was the fact that the engine was always designed to be vertical. In my case, the lateral layout required a properly sized axle to run along the sides of the engine, and Audi didn’t design the engine with that in mind, so the large blocks that get in the way of that axle. There is a part. The starter, oil filter / cooler and engine mount are also getting in the way on that side, but I’ve solved those problems. The nail in Audi’s casket was an adapter plate. The adapter plate could not be tightened because we decided that we needed to place some of the mounting bolts inside the bell housing of the 6-speed transaxle we were using. At that point, I decided to change my approach and use a different engine.

Stay tuned for the next article in this series.