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Racing Fuel and No Cats with Stock ECU

Old 09-24-04, 08:12 PM
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Question Racing Fuel and No Cats with Stock ECU

I have a 93 touring that has no interior and a full, welded-in cage. I built it primarily for SCCA Solo I but am thinking of putting it back on the streets too, as a joy ride type car. I live in FL and this car qualifies as street legal here..

My question is about using race fuel to overcome the detonation risks associated with doing too many mods without an ECU upgrade. The driveline is presently bone-stock with the exception of an open catback and downpipe. I have done a little homebrew tweaking to get more and cooler air into the stock airbox and done some aluminum ducting to force more air through the stock IC.

What I'm really wanting to do is go ahead and remove the main cat and air pump and possibly put an aftermarket intake on it. Other than that, I don't see myself doing any significant mods to the engine any time soon. If I do that and run pure race fuel all the time, should it be ok???

In case anyone is going to mention how terribly expensive race fuel is, I'm aware of that. This car is only raced right now and would only be on the streets once a week or so, and not for a lot of miles. I wouldn't really use that much fuel with it.

Thanks for any advice.
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Old 09-24-04, 08:23 PM
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Just do the ECU upgrade. Either way the ECU itself will not let you go over 12psi in boost anyways.
Im running a gutted cat with a stock muffler, downpipe, intakes and i have no detonation problems on 93 octane. My next mod is an ECU.
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Old 09-24-04, 09:39 PM
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No, running race fuel is not good compensation for running lean. Doing too many mods on an FD without changing the fuel maps will cause the engine to run too lean and your engine will suffer. Secondly, if you remove your cats you'll need to port your wastegate in order to avoid boost creep. The stock wastegate can't keep up with such low backpressure.

If you want to remove your cat you MUST make sure your engine is getting enough fuel and you can still control your boost or else you're engine is going to die a premature death.

-John
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Old 09-24-04, 10:11 PM
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Yeah, that's what I was afraid of ... more looking to eliminate the weight of those parts and the drag of the oxygen pump than anything else, but if that's how it is, then I'll just have to wait till I can afford a new ECU.

Thanks,
Tubbs
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Old 09-25-04, 12:27 AM
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You can remove the air-pump if you want.
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Old 09-25-04, 12:39 AM
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With all due respect to the cautionary notes from the above posters, simply opening up your exhaust will not yeild high enough boost to blow the motor assuming 101, or better gas. What boost are you seeing on a 4th gear pull? I suggest you dyno the car with a wideband O2. As long as you are in the 11.3 or richer you will be fine on race gas. You might see an additional 50hp with an open exhaust, and that is well within the capability of the stock fuel system. If you like, add an E manage, or an Apexi S-AFC, with either you can increase your injector duty cycle, and stay well in the safe zone. Do a search on the third gen forum, "max HP on stock fuel", you will get the validation you require. Carl
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