Demon88 Project
LS7/T-56 Widebody Mk3 Supra
The Recipe
Take one 1988 Toyota Supra, strip it down to a bare chassis, build a full roll cage, stuff a Chevrolet LS7 crate motor under the bonnet, mount coilovers in the corners, flare the fenders out to run wider wheels, and rattle can a coat of flat black on the body.
What do you get?
I jokingly refer to it as the Demon88 project.
It's either the recipe for complete success or for complete and utter disaster.
The Idea
We start with the car. The Mk3 Toyota Supra. A great car in and of it's own right. A superstar of the boy racer scene, the Supra is universally known for it's twin turbo motor, and many an intertard fanboy will argue its superiority over any car made. The stark reality is that the biggest down fall of the Supra is in fact this twin turbo motor. This laggy beast is known for it's insane output when spun up and make excellent drag cars. Only problem is that Im not building a drag car. My goal is to build a swiss army knife, not a sledge hammer. This car is intended to be used as a road car, so it has to be quick in a straight line, but faster in the twisties.
The Car
This project is built on is a 1988 N/A, Targa, 5-speed, with a 7MGE motor. I have owned this car since 2000 and have been plagued by the typical host of Mk3 problems. Leaky targa, blown head gaskets, blown motors, and over heating.
Let's focus on the motor, since this is the main goal of this project.
The 7MGE motor is a 3.0 litre 24-valve DOHC/fuel injected engine. It had an output of 204bhp at 6800rpm and 200 ft-lbs at 4800rpm and weighs in at chunky 698lbs for the engine/tranny combo adding to the nose heavy 3398lbs car. Not exactly the recipe for a quick car.
Mk.3 Supra, LS7. LS7, Mk.3 Supra. Now you two kids play nice.
The LS7 is GM's golden child of a motor. This engine breaks all the rules for big motors. The 7.0 litre 427cu.in. 16-valve has an output of 505bhp at 6300rpm and 470 ft-lbs at 4800rpm and with the Tremec T-56 6-speed transmission it's not unheard of to get up to 30 mpg. The LS7/T-56 package weighs in at 598 lbs., a 100 lbs weight savings.
Now making the nose of the car lighter and more than doubling the power and torque output of the car is an awesome thing. That 100 lbs diet gives the car a more central bias, pushing the weight distribution closer to 50/50 which is the goal for any race car. Now that we've made the car lighter, given it a better weight distribution, and increased the overall output by 2.5 times, we might have a some problems it we dont address safety and structural rigidity.
The Targa Twist
I plan to completely strip the interior out of the car, losing even more weight and mounting a full roll cage to stiffen up the twisty targa unibody and tying all four suspension towers together to allow the suspension to be more efficent and keep the car glued to the road. Now roll cages are an interesting subject. If I ever want to actually race the car in a series event, I have to design and build the cage to series specifications. I really have no idea if this car will ever be raced in a formal series, but it will be run in road rallies, fun runs, and the occasional track day. So my major concern is my own personal safety and the safety of my co-driver.
My basic design is a 9-point cage based off of Group N specs that will incorporate all four shock towers, engine mounts, transmission mount, and k-bars to connect the strut towers braces to the cage to further decrease lateral flex and increase torsional rigidity. There will also be bracing in the roof section to increase safety when the targa has been removed. The roll cage will also serve as the superstructure for the cockpit rebuild and hard mounting of the electronics package.
Springs and such
There are two parts of this project that offer the most options and yet there is reletively little hard data to help with the selection process of these areas. Those are suspension and wheel options. In this section I am going to focus on suspension selection.
If the motor is the heart of a car, the wheels are it's shoes, and the suspension is it's legs.
What I would like to achieve with the suspension of this car is to have as much adjustment as possible and for it to be as easy as possible to adjust. Now that the roll cage has made the chassis as stiff as possible the suspension is going to have a much easier time doing it's job, since we have eliminated the flex and wallow of the unibody chassis, we need to put some control at those four corners. Coilovers are the only option and there are a lot of them to choose from. There are possibly too many options in fact. From the basic coilover all the way to the full race application with remote servo motors to allow on the fly adjustments to full custom builds. More research needs to be done in the selection of suspension.
So, I have had a few more ideas for this project. Most good, some bad. I had a stroke of genius insanity this morning on my commute in to the office and am now playing with the idea of a transaxle. Porsche G50 or one from a ZO6. Although this will move the weight distribution closer to center, it does come with extra comlications. With the application of a tranaxle, I now have to fabricate the whole of the rear suspension into the roll cage. But, the upside is that it would be easier to accomodate the shifter in the cab, being that it is a remote unit off of the transaxle. I would also be able to move the engine further back in the bay, and thusly further behind the front axle make the car more centrally balanced. This is an option, although an utterly too expensive one, that might have an excellent benefit to the project if the concept can be proven. More research will have to done before the idea is chosen for the project.
200mph is the ultimate goal.