Dyno Results

I dyno tested my stock GTZ on a Dynojet at Atlanta Chassis Dyno. I have published the results for the Beretta and Quad4 community to peruse. My GTZ made 151 HP at the wheels which puts it in the hunt with some of the hottest import cars currenly on the market. It has about 10 HP more than an Integra GS-R and about 10 HP less than an Integra Type-R in stock form. Results from these cars can be found at the Integra Dyno Center. Both have a very strong following on the import scene. I only hope that we can develop a good market for the Beretta like the import cars have. Performance parts are hard to find for our cars and the results of those parts are even harder to find! I have started my trek though the possiblities in hope to find some parts and combinations of those available parts that will increase the performance of my car as well as yours. Others will be joining me in this process with different model Berettas. Hopefully we can publish all the results here on this site.

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

I have also learned to use a program called Street Dyno. This program allows you to do "runs" with your car while recording the tach pulse. You then take the recordings and input them into a computer program that will output a dyno "run" much like a real dyno will. This program can be very accurate, but is only as accurate as the operator! Learn to use this program and understand how it works and you will be able to make accurate and repeatable results with your car. Here are some of the tests I have done recently. The best way I have found to record the tach pulse on my car was to tap into the tach wire in the dash and then record that directly into a portable camcorder. This gives a high quality signal that is easily captured.

92 GTZ Quad4

Stock vs Tornado Air Management System (also like Spiralmax): This device is a waste of money. This Spiralmax was sent to me by a mailing list member so that I could test it. I found that it made no measureable difference and may have slightly harmed high RPM horsepower. Overall I would save my money and use it on something else!

Stock vs Cut top of stock airbox: This has been a common modification by list members that want the sound of an open element filter like the K&N cone filter. I have long argued that I didn't think that this modification really helped. Well I did learn some interesting things about this modification during testing. It seems that it does help in some areas, but hurts in others. If you average the power output from 3000-6500 RPM the HP and TQ difference is nothing. However, the modification does raise the HP above 4800 RPM to redline. The drawback is that it lowerd HP and TQ below 4800 RPM. If you are a drag racer it may help slightly. The biggest change is that the RPM range that you use for everyday driving will lose TQ and HP. You will gain a really nice inake growling sound. Of course this extra sound doesn't mean you have more power. The airbox modification gives a peak increase of 3 HP and 2 ft-lbs of TQ.

Stock vs Custom 2.5 inch exhaust system: Whoa! You can really feel the car pull on the top end of this setup. It only has about 5HP more on the top of the RPM band but pulls harder than ever up to the limiter at 7000 RPM. I accidentally bumped the limiter a couple of times because of the extra pull up top. This system gains all across the power band, but mainly above 3600 RPM. Unfortunately it is WAY TOO LOUD! I'll have to have a resonator put in to quiet it down some. I am wearing ear plugs back and forth to work. I still don't recommend removing the factory airbox without a well designed cold air intake system (which no one makes). I suggest designing your own.
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. This converter leads into a 2.5 inch center-center Edelbrock RPM series muffler which hides in the stock converter location. From there the pipe turns and exits right in front of the drivers side rear tire.
Sounds:
Here are some MP3's of the new exhaust. The first is starting the car. The second is inside the car taking off in traffic. The third file is taking off in traffic running the engine up to about 4000 RPM. Don't let these files fool you. It is LOUD!
Pictures:
1st - New 2.5 inch downpipe from the manifold.
2nd - New 2.5 inch downpipe from the manifold.
3rd - Random Technology converter and Edelbrock RPM series muffler.
4th - The whole system.

I have since mounted a resonator after the Edelbrock RPM muffler. The car is still loud, but is now bearable. I think the resonator hurt my top end power a little. I haven't been able to get a test yet to find out.

Future

I have a few more power mods to make and already have some of the parts. The first is a modified manifold made by Robert Cossaboom. It is a VIN A manifold that has had the exhaust ports cleaned up and the collector slightly enlarged.
Pictures:
1st - The exhaust ports of the manifold.
2nd - Closeup of an exhaust port.
3rd - Another exhaust port.
4th - Another angle of an exhaust port.
5th - Getting tired of exhaust ports yet?
6th - How about the collector?
7th - Closeup of the collector.
8th - Another angle of the collector.
9th - The exhaust collector one more time. I think it needs to be enlarged a bit more.

Email: Rex

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