Pro-jection, EGR vs Non-EGR Question

[Narnian]

The previous owner of my Jeep removed all the smog equipment and put the Edelbrock performer non-EGR manifold on the beast.

The previous owner of my Holley Projection told me that with the non-EGR version of the performer, I was likely to get pinging at highway speed under load. He included an EGR performer manifold with the pro-jection unit.

Ralph and I finally got all the power working super-duper a month or two ago when we replaced the timing chain.

I get some pinging under load, at highway speed. Is there any reason to believe that using an EGR manifold (with the EGR plugged up) would make ANY difference, or do I just need to tinker with the tuning?

Or do I just need to go to a higher octane?

[Stolen76]

Do you have the O2 sensor kit installed ?

[Narnian]

Yes. It's not precisely where they recommend it, but it is within 3 feet of the exhaust ports.

[Sgt. Dave]

Since you have an O2 sensor, tie in a A\F ratio meter and check the mixture at cruise speed. EGR reduces detonation by lowering combustion temp.
Make sure your cold air inlet is hooked up and working, and the exhaust heat riser is free. Run a 180 or even a 160 degree thermostat. Add a bottle or 2 of wetting agent to the cooling system. Any oil control problem will cause detonation. Believe it or not, changing brands of oil can make a difference! No, a EGR manifold without the EGR hooked up will not make a difference. But when they are available, the Edelbrock Air Gap Manifold will help.

[JohnnyJ]

I've been playing with the same issue and almost the exact same setup. I've got the Projection 4Di and Edelbrock Performer (no EGR), and I've been trying to tune out that same pinging.

I noticed that when I am climbing hills at highway speeds I get some pinging. The computer shows that its running a good mixture, so I thought the mallory unilite I was using at the time was advancing too much or something along those lines, or I didn't have the acceleration compensation dialed in. I haven't hit highway speeds with the stock dist with EFI upgrade yet to see if it solves the problem. I never thought to link it to the lack of EGR valve...

I haven't tried higher octane gas yet, either. At 10mpg, premium is mighty spendy. There was another guy in my area with Projection, I wonder if he has the same issues; I'll have to send him a mail.

[Sgt. Dave]

Could also be vac advance related. Run a temporary vac gauge, and see what the dist. vac is when you get the detonation. If it is high, dial out some vac. advance. If you are showing low vac., back off the base timing, or put in heavier advance springs to slow down the timing curve.

[Narnian]

This is good info. Basically, you guys are saying I need to play with the tuning and not worry about the EGR manifold. That's what I really needed to know.

I'll give all these suggestions a try when my garage warms up some more.

My temp seems to run pretty cool generally. I have one of those Edelbrock Air Filter covers that leave the filter open to air, and I have the fancy air filter too. I intend to keep the airfilter but eventually hook up a stock cold air intake setup, which in my opinion would work better. At any rate, I don't suspect the air being too hot, but I admit it is possible.

I would be quicker to suspect the vacuum advance. Especially since I've never been convinced that I hooked it up correctly to the throttle body & CTO. I do have a vacuum pump with a guage, but I'm not sure how you would test that while driving up a hill on the highway, nor do I know what would be high or low. Any more suggestions?

Of course, if JohnnyJ is having a similar problem, it might not be a problem with the vacuum advance - Isn't the unilite a mechanical advance unit?

[Sgt. Dave]

Bypass the CTO, and put a "T" fitting in the line. Grab about 6' of vac. line, and run it into the cab. Now you can see what vac. signal your distributor sees.
BTW, make sure you are running ported vac, not manifold vac, to the distributor.

[RWC]

If I recall correctly, the Pro-Jection instructions said to run premium fuel. While it's spendy, I think its worth it. I only get knock if I try to (like trying to accelerate up an on-ramp in 4th gear). Since having installed the DUI with timing-control, I haven't had any knocking whatsoever, and I'm still dialing in the timing curve. When I still had the stock distributor, I just left the vacuum advance unhooked. Oh, and yes, I have the non-EGR manifold.

So in short, my recommendation is to run high-octane fuel.

RWC

[Narnian]

What is a DUI?

I will run through some of these checks, do a fresh tuneup, and if that doesn't do it, I'll go to a higher octane by using octane additives from Autozone.

Thanks fellas.

First person to tell me DUI is Driving Under the Influence will get a chuckle and a sneer.

[RWC]

A DUI is a Driving Under the Influence. ;)

Performance Distributors makes the Davis Unified Ignition, which is a hot HEI that they put on another distributor. I got one custom made to include the GM spark-control (ECU controlled timing curve).

RWC