Racod

I am swapping the exhaust on the 1990 vette I just picked up.

I am swapping out the front cats for a straight thru Y pipe. This will go into a HI Flow resonator and into another Y and finally to the exhaust. Everything is MAGNAFLOW, Stainless Steel.

I hope to have significant improvement in both sound and power. I am keeping a resonator in an attempt to eliminate possible drone. The shop is making me a pipe to swap it in and out if I like.

Y pipe


Pipes

65Z01

That will nicely open up your much restricted exhaust system.

Now match that with cut lid & K&N, bump fuel pressure a tad and you should see/feel a nice power boost.

Racod

Running great. But my check engine light is on. I retained all sensors.
Could it be the oil in the new pipes? They really stink.

corvetteronw

Pull some codes and see what they tell you.
http://www.corvettephotographs.com/c4vettes/codes.htm
There is a good chance that the Oxygen sensor got screwed up/broken/banged up on the install or was never even hooked up at all.

Racod

Code 32. EGR valve failure. I assume this is the tube that goes to the mid cat/resonator. It is attached. Could this be due to a high flow cat?

Any harm being done??

aklim

I don't think this is going to see significant power seeing as you still have the stock exhaust manifolds and no tune.

Racod

Drove today for 15-20 minutes with no code. Weird. I will keep and eye on it.

Concerning the power, seems a little more snappy. Throttle response seems better. Could just be the exhaust note.

From what I have read, most of the chips for the L98 are worthless.??????

The guys who helped me out said freeing up the pipes and removing the cats is good for about 20-25 HP. May get another 20 by installing headers. I think those are a bit high but I am happy with it now. At least it sounds like a vette should.

aklim

EGR isn't always going to show. I believe it has to have certain conditions to activate. Been too long since I had to deal with it.

Most likely it is a placebo effect.

Mist any chip off the shel is worthless. Either get it tuned using Datalogging or a dyno.

Using those calculations, I'd have 2000 HP. I don't think headers and exhaust alone is going to net you 50 HP. Toss in a dyno tune after you do an intake and you probably would

Racod

how exactly does a tune work on an L98??

aklim

They programs the ECM with different values from factory to optimize the system in place. They strap it onto a dyno and tweak the entire program to utilize what you have. The other way is to hook up a laptop and record what the ECM sees and tune it remotely.

Racod

so they re-program the chip while its in the car.....

coupeguy2001

no, it's not done that way
the chip gets pulled out andis modified on a chip burner witha laptop and program

The EGR code is set when the ECM sends a signal to the EGR solenoid to open the EGR valve. THe sensor on the EGR pipe then (supposedly) gets hot, generating a resistance change that the computer sees and interprets as the pipe getting hot, ergo, the EGR valve is open, and exhaust gasses are flowing, heating up the pipe.

I have an 86 with an 89 right hand exhaust manifold. THe 89 manifold has the bolt-on type of EGR tube that you have. I loosened the two bolts out by the outside edge of the rocker cover on the exhaust, and slipped a thin piece of aluminum in there and i tightened the bolts, effectively turning off the EGR.
The interesting thing here is that the sensor on the pipe apparently gets hot enough that the code never gets set.
A few years ago, the connector became disloged from the EGR solenoid and that threw a code. THe pipe that never gets hot doesn't.
I saw an 89 corvette at a car show once that the guy installed a blanking plate on the right EGR pipe, drilled a hole in it, and installed the EGR sensor right in the blanking plate. I asked him about it, and he said it worked for all intents and purposes. I.E. no codes.