Nine Ball

iTrader: (38)

As most of us know, the '98-'00 F-bodies have an EGR (Exhaust Gas Recirculation) setup on our motors, yet the Corvettes from '97+ do not. The only thing within our engines that varied were the cam specs. How were the Corvette cam specs changed to compensate for a lack of EGR system?

Here is the weird situation with my car. I have my EGR valve blocked off completely, so no line going into my LS6 intake whatsoever. When I still had the 221/221 T1 cam, I would get that EGR SES code/light about once per week. After I put the 232/232 T2 cam in the motor, I have not seen the EGR code for the duration of 2250 miles on this setup. No computer work was done, nothing at all was changed on the EGR setup. And yes, my SES light still works because I get the P0300 random misfires sometimes.

Anyone have any ideas of why this cam swap took care of my EGR SES codes? Not that I'm complaining hahaha!

Tony

John B

iTrader: (10)

Tony, my understanding is that the C5 accomplished its EGR via additonal overlap degrees in the camshaft.....in other words it mechanically accomplished the same thing that the F-bodies had to do via the manual EGR valve. The reason the '01 & '02 F-bodies no longer have EGR is due to the Truck camshaft which has more overlap (supposedly).

Now, onto your situation, is anything left connected on the other end of your set-up (at the headers and are the electrical components still connected to the EGR tube)?

What is really strange here is that the PCM sends out a 5.0 volt reference signal to the EGR valve to determine the position of the pintle. The PCM is doing this typically during deceleration to determine the MAP sensor reading while runing a diagnostic to determine EGR flow. Since your EGR is "not flowing" I cannot imagine where the PCM is getting a return signal <img src="images/icons/confused.gif" border="0">

I would only be guessing, but somehow I believe the larger camshaft has fooled the PCM into believing that EGR flow is occuring (because it is mechanically, due to the larger overlap)....I just don't know how!

Another thought and maybe more plausible....perhaps the MAP sensor is reading a lot lower now (due to the decreased vacuum) and the PCM doesn't think that EGR is required so it is not asking for the EGR valve to open.

I noticed that with my B1 cam installed (obviously a lot less radical than yours) that the MAP sensor readings are a lot lower indicating that I have a lot less MAP hg now compared to the stock cam. Since the MAP sensor is key to EGR function when the PCM tests it, maybe like I said, the PCM just doesn't activate the EGR circuit now because the hg readings don't necessitate it based on the tables contained in the PCM. Just my .o2 <img src="gr_images/icons/wink.gif" border="0">

[ January 09, 2002: Message edited by: John B ]</p>

Nine Ball

iTrader: (38)

That sounds reasonable John, maybe it is the increased overlap cam and the different MAP sensor readings that prevent my EGR setup from activating. Hmmm.....

My EGR setup is still on the car and the electrical wires are still plugged in like normal, I just have a sheetmetal block-off plate inside the valve itself.

Tony

WhiteDiamond

Tony,

The operation of the EGR is monitored the MAP sensor at the rear of the intake manifold. It is fairly simple, PCM commands the EGR to open to some setting(steps) and then looks for a corresponding change in the MAP sensor. In reality, nothing you do with your cam should really have an effect on this. I guess you are getting lucky on this somehow. I wished it would have happened on mine, but I got the EGR code consistently until the PCM got changed.

Todd