dscottr

I just ordered a custom chip from ed wright to go with my LT4 hot cam and was talking to him about my plans for the exhaust. He indicated that a client of his lost 10 hp when taking out the cats. I was going to go with long tube headers into my new corsa cat back system, and delete the cats. Now I am not sure which way to go. Any suggestions?

Raysur

He probablt forgot to install some O2 simulators. His cars needs them (OBDII). But we don't.

Many here on the forum have gained power from doing this. I want to run cats when I get headers. The smallest cats I found are 3" in diameter (casing). These are high performance cats for the Civic SI and Integra. It's ok to laugh:D. These suckers look like polished pipes. When they are installed there will be no clearance issues what so ever. :smash: You can see a good amount of light through them too. :cheers:


[Modified by Raysur, 11:56 AM 7/31/2002]

Nathan Plemons

When I went from my stock manifolds with cats to long tube headers and no cats I picked up 23 hp and 32 pounds of torque. This was with the Ed Wright chip & LT4 Hot Cam.

tkrussell

There are two issues.
1) At WOT, the PCM controls the AirFuel Mix and Advance in a predetermined map. With major changes, such as cam, head porting, headers, intake, etc. there is good probability that the previous predetermined (at the factory) AirFuel and Advance map will need modification. Hence the new chip.

2) At part throttle with the engine warm, the car runs in Closed Loop, where the precat O2 Sensors read the AirFuel Mix and adjust it to ideal (about 14.7:1) This optimizes emissions, but is a little less than ideal for fuel efficiency. If the O2 sensor doesn't heat up or is otherwise not working, the car will not go into Closed Loop, and a preset (by the factory) AirFuel and Advance map is used. This part throttle Open Loop map is just a likely to need alteration after major engine changes, but is usually not redone for cost reasons ( if the engine is in Closed Loop, why bother)

3) Incidentally, on the LT-4, the cam has enough overlap to do away with the need for EGR. So if you are redoing the chip anyway, why not remove that source of hot gasses in the intake manifold.

Zora

Did you gain 23 HP with just the headers and No cats? Or was that including everything(headers,No cats,Ed,LT4HoTcam..etc..)?

silver & red CE

You're not going to lose HP by adding long tube headers and eliminating the cats. But your Vette will be real loud. Vettewrench here in town has exactly the set up you are considering, I was amazed at how loud it was. In fact, I was going to go that route until I heard his car, made me stop and rethink my plans. I know RichS had exactly the same set up and he added cats to quiet it down.

Eric