EGR valve block off plate

[b4black]

Has anybody ever seens these for sale in the auto parts stores? I what to try running without the EGR in place. I can fabricate one, but I'd just buy one if they're cheap and easier to get. Probably not, since their purpose is disabling emissions.


I'm still trying to get rid of the WOT strumble. I put most stuff back to stock, 10 psi, and eliminated all the knock, but I can still feel a flutter. My latest thought is that the EGR is opening and allowing exhaust gases to pass thru. The EGR sees pre-turbo backpressure. This can be 20+ easily at WOT. This might be enough to push the valve open. It's a Tomco aftermarket valve. I've sent an e-mail to the manufacturer to see if they know what psi it can hold back.

It's a pain getting to the EGR. It's behind the carb.

 

[pat83t]

Actually they are not offered anymore. Edelbrock a few years ago was threatened with a whole world of trouble for offering them so to avoid trouble they pulled the item. Now if you want one you either have to seach the swap meets or fabricate one.

 

[Freddie's Buick]

I cut one from 1/4 " aluminum plate, polished it to a mirror finish with various stones and made a gasket to fit. It looks great! But after all that work once I installed it one could'nt see it anyway. (Oh well).

Rich, I'm sure you know that on most of our cars the EGR is a positive back-pressure type. Modifications to the exhaust, (ie: headers, gutting the cat or any type of elimination of exhaust restriction will impede the EGR from working properly).

I still have'nt figured out how to overcome this yet, but I'm still working on it. On my Regal removing the EGR caused detonation at the OEM timing specs. I had to drop the timing down to 8 from OEM spec of 16. This eliminates my knock, but performance dropped.

The EGR valve allows for the higher timing and performance since under load the re-circulated exhaust gas enters the combustion chamber, cools and dilutes the mixture thus drastically reducing knock.

A lot of people think that the EGR valve is just an emissions control device and remove it. Technically it is an emissions device, but it is a needed on our cars since it allows for the higher timing.

 

[b4black]

My EGR's diaphragm has be blown for some time. But it doesn't knock, unless the coolant gets above ~180° (Initial timing @ stock 15°BTDC).


The EGR I'm running needs just a tiny amount of backpressure. Vacuum is only applied by the solenoid during cruise, and there is always some BP at cruise, so the BP transducer may become un-necessary. I will be trying to set up the EGR as a straight vacuum operated valve, with vacuum regulated by the ECM.


The point of blocking it off it to diagnosis the WOT flutter. The easilest way to confirm it's not being forced open by the exhaust backpressure (which is greater than 20 psi prior to the turbo) is to block it off and see what happens.

 

[b4black]

Originally posted by b4black
I've sent an e-mail to the manufacturer to see if they know what psi it can hold back.

It tooks me several e-mails to get an answer:

I applied 25 PSI to the bottom of our EGR Valve. It was not enough to lift the pintle. Naturally, there is some leakage with that much pressure, around the seating area. So in answer, I hope to your question, it should not be able to lift the pintle off the seat.

Some leakage? I'll take that as a maybe. That leakage may be enough to hurt perofmance. I guess I'll try finding some time this weekend to pull it off and test it myslef.

 

[Freddie's Buick]

The easilest way to confirm it's not being forced open by the exhaust backpressure (which is greater than 20 psi prior to the turbo) is to block it off and see what happens.

Rich,

How do you know BP is greater than 20 PSI? Did you attach a back pressure gauge in the oxygen sensor opening? That is how it's done now-a-days and I am thinking of getting one.

If you did go this route why don't you ask them how much BP is needed to open the EGR?

Anyway, here is what I am brainstorming about: First of all I think that the EGR/VAC selonoid's only function is prevent vac from getting to the EGR during cold operation.

The ECM tells the EGR/VAC/SEL to allow vacuum through once temperature is 195 or above. But just because it allows vac to get to the EGR does'nt mean that the EGR will open. Back pressure under a load condition is what opens the EGR.

Our EGRs are basically a duel diapragm. The top is controlled by vacuum. The lower is by pressure volume. When pressure is high at the bottom it pushes a pintel that closes. This allows the vacuum to open the valve.

When warm there is almost always vacuum at the top. Ports below the pintel on the diapragm inside the EGR prevent the valve from opening.

I think that maybe a better way to allow vac to the EGR is using a 190 degree TVS rather then an EGR/VAC/SEL. By the way, I tried a reguler GM ported vacuum type EGR. It opened the valve too quickly and for too long. The results were horrific. I think the BP EGR valve is the way to go.

My EGR is new and is made by Wells. It came with different sized metal washers. Each has a different sized port opening to restrict or reduce pressure on the exhaust side of the valve. I used the OEM size for my model year but it still opened too quickly. I've yet to tinker around with the other sizes yet. (Working back there behind the carb as you are well aware of sucks).

 

[b4black]

I can measure BP at the EGT bung I added near the O2, or at the EGR itself. I already ask Tomco at what pressure it opens. That's their answer above.


I've watched how/when the EGR is functioning, by hooking up a vacumm guage to the solenoid. It's only on at part-throttle cruise. The ECM is turning it off and on often and when it's on, it's pulse modulated. (But the '83 is a little more advanced than '81).


It's not the EGR's operation I am having trouble with. It's when it's closed at WOT, it can't stay closed. Nothing do to with vacuum, solenoids or ECMs.