EGR and transitional knock

[TType85]

I have been chasing down a few problems where if I go to WOT from part throttle the car stutters and I sometomes get knock as boost comes up (as I mash down on the throttle).

Just to put it out of the equation I unhooked the EGR and took the car for a test run. Knock and stutter went away.

How could this be possible?

Does the computer advance the timing when the EGR is working?

Maybe the ECM can't keep up with the way the motor flows air now?

 

[TType85]

TTT

 

[WarpSpeed]

Maybe,, maybe the little filter that bleeds off vacume on the back of the EGR solenoid, is dirty. Maybe the EGR valve itself is getting lazy/old.

 

[buickboy]

Walbro 307 pump is not enough fuel for your combo. 340 hotwired or a Red's XP+ hotwired is the ticket.
Mitch

 

[bruce]

Originally posted by TType85
I have been chasing down a few problems where if I go to WOT from part throttle the car stutters and I sometomes get knock as boost comes up (as I mash down on the throttle).

Just to put it out of the equation I unhooked the EGR and took the car for a test run. Knock and stutter went away.

You probably have 2 problems.
One is the fuel pump size,

With the EGR on, it is allowing HOT EXHAUST fumes to channel up and thru the intake manifold. These Hot Exhaust Fumes heat the manifold. The hot Manifold Heats the air that the engine is consuming. This hot air needs either more fuel to cool it off, or less timing.

The ecm doesn't sense EGR flow. It just expects that if it's commanded on that it is. In the original calibration they run lots of timing in cruise, because they figure the EGR is going to be on.

And when you increase the cam, and run EGR you're probably over EGR'ing the engine, since the larger cam increases the self EGR'ing aspects of the engine.

 

[TType85]

I'm waiting for some more $$ to come in to do the rest of the fuel system. The 307 is hotwired and i'd think would be fine on the street, but who knows.

I didn't know that the larger cam would act sort of as a EGR valve. Seeing as I have GN1's I want to put on the car, maybe I can get away w/o having the EGR for smog? (there but not functional at least).