Dyno Results

More dyno tests were performed on my GTZ on a Dynojet at Atlanta Chassis Dyno. This time my GTZ made 158-167 HP at the wheels depending on the configuration of the modifications. I have found a few combinations that do increase the performance of my car and most are not expensive.

Ever wonder what is is like to have your car dynoed? How about getting a first hand look.

YOU MUST REMEMBER ALL THESE FIGURES ARE WHEEL HP NOT FLYWHEEL HP!

92 GTZ Quad4

Stock vs Custom 2.5 inch exhaust system and modified Vin A exhaust manifold: I have 7 HP more at 6300 RPM and it pulls harder than ever up to the limiter at 7000 RPM. This system gains all across the power band from 2800 RPM to 6900 RPM where the limiter cuts me off. This system is NOT for the faint of heart and is a bit loud. I have found that the stock airbox is only restricting a peak of 3 HP at the wheels. I hope to design a good cold air system soon. I had some dyno runs done without any of the factory tubing. Those results are interesting.

Stock vs Exhaust, exhaust manifold and removed stock intake system: This was a bit of a suprise. The removal of the stock intake only gave me 3 HP extra at the wheels, but the gains were all over the RPM range. Gains came from 2600 RPM up to 6900. The largest gains were in the upper RPM range. It really just shifted the entire power band up a couple hundred RPM. This gave me a total of a 10 HP gain at the wheels versus the stock motor.

Stock vs Exhaust, exhaust manifold, removed intake system and no A/C - Alternator belt: Since the Quad4 water pump is driven from the timing chain you can remove the air conditioning and alternator belt from the engine with no chance of damaging anything. This REALLY HELPED for drag racing and it showed on the dyno! I gained ANOTHER 7 HP at the wheels for FREE! After seeing this I think that power pullies really are probably worth the money. If you have a 91-93 Quad4 then you have a larger factory pulley then the 90 Quad4's did. If you can locate one of these smaller pulleys then I would grab it. I think the gains would be worth while. Unorthodox Racing also makes a pulley kit that should fit our cars which is made of aluminum. These smaller aluminum pullies also save rotaional mass, which frees up more power from the engine. I gained a total of 17 HP at the wheels from these simple modifications versus the stock motor!
Parts:
I had a custom 2.5 inch pipe made from the exhaust manifold back. I used a Random Technology high flow small body converter. That leads into a 2.5 inch center-center Borla Mello-Primo series muffler. The muffler is in the stock converter location. From there the pipe turns and exits right in front of the drivers side rear tire. I have also added my modified Vin A exhaust manifold. I increased the collector size from 2.0 inches to 2.25+ inches. I had to modify the flange on my downpipe to accept the increased air flow. The downpipe flange was also 2 inches or smaller on the inside diameter. This is probably why I initially didn't see much increase in power from the larger exhaust. It now serves as a smooth transition from the manifold to the downpipe.
Sounds:
Here are some Real Player files of the new exhaust. The first is taking off from a stop light. The second is inside the car playing around with the gears. I then stop at a stop light and take off rather quickly in the rain. When I shift to 2nd I get a lot of wheel spin. I repeat it at the next light. The third file is taking off from a light and running up near the limiter.
Pictures:
1st - Stock exhaust flange.
2nd - Modified exhaust flange.
3rd - Stock vs. Modified Vin A exhaust manifold. (Stock is on top)
4th - Stock vs. Modified Vin A exhaust manifold. (Stock is on top)
5th - Stock vs. Modified Vin A exhaust manifold. (Stock is on top)
6th - Rex at work.... (Notice that this is before I changed mufflers)
Movies:
1 - What is a dyno run like?

Future

I have a few more power mods to make. (Of course!) I'm not 100% sure what it will be but it will likely be a smaller crank pulley or an intake system. I also got to ride in Adam Mufford's 93 GTZ with a 50 HP NOS "wet" system and let me tell you it is FAST! That nitrous feels good!

Email: Rex

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