I was wondering if anybody could give me an in-depth explanation of how the EGR system works, what factors determine whether exhaust gas is recirculated, what are the advantages and disadvantages to this, and especially how the passages are arranged in the cylinder head and intake manifold.

I would also like to know what heat risers are and since the L98 Vette heads don't have EGR passages, would it be bad to put an intake manifold that supports EGR on my engine. I'd like to keep the EGR valve there so it'll pass visual inspection and keep a fairly stock look.

Jason

 

I can't answer all of your questions, but here's what I know. The EGR system recirculates exhaust gasses back into your combustion chamber to keep combustion chamber temperatures down and therefore emissions (NOX I think). The valve is obviously run by vaccum, but I'm not sure where this vaccum actually comes from. If your car originally had an EGR valve on it, then if they do a visual inspection it better have one. If the engine that you are running didn't however, I don't know if you can really incorporate one. If it did originally have one keep it because it actually helps your engine, not hinder it like many people believe.

 

http://sethirdgen.org/egr.htm

As for your other question, a heat riser is when exhast gas is routed into the intake for the purpose of heating it up for cold starts.

As for the EGR on a Vette, no it doesn't have EGR passages in the head, that is why there is an external tube from the exhaust to the lower intake righ in front of the distributer on the passanger side.

------------------
If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
Ported Plenum,
TB Coolant Bypass,
SSM SFC,
Boxed LCAs,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims.

'97 Bonneville SSE

 

Thanks for the help guys. Vader, the link you gave me answered a lot of my questions, but I have another for you.

If I want to put the L98 Vette heads on my Camaro (89 RS, 305 TBI), what can I do with the EGR? The article on that link says that EGR can actually help performance a little so in my opinion there's no real reason to get rid of it, especially if it helps emissions.

Do you know of any way that I can keep the EGR system operative while using the L98s? I will be doing headers at the same time as the heads, is there anyway to hook up this Vette "tube" that'll take the EG right from the headers and throw it at the EGR valve? If not, are there any other ways to keep EG flowing to the EGR vavle?

Any help you can offer on explaining this to me would be greatly appreciated,

Jason

 

BTT

 

I'm not Vader, I just act like I'm as smart.


As for EGR boosting performance, well, thats kinda how you see it. It does cool combustion chamber temps, allowing more timing, but the trade off unburnable gas choking out fresh air. I wouldn't say it boosts performance, but I wouldn't say it hurts it either. I would say the trade off is even.

If you had TPI, the simple solution would be to use a Vette TPI base, and crossover tube, and just attach it to the manifolds, but since you have TBI, that puts a dampner on things. I really don't know how you would plumb EGR around the heads.

------------------
If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
Ported Plenum,
TB Coolant Bypass,
SSM SFC,
Boxed LCAs,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims.

'97 Bonneville SSE

 

Thanks for the reply GMTech. Let's assume I switch to TPI at the same time. Then let's say that I get the Vette TPI base, where does this tube connect to? I'm under the impression that it connects to one of the Corvette's exhaust manifolds and to the intake of course, is this right?

Jason

 

Yes, the tube bolts to the intake on the passenger side, but I don't remember how it attaches to the exhaust manifold.

------------------
If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
Ported Plenum,
TB Coolant Bypass,
SSM SFC,
Boxed LCAs,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims.

'97 Bonneville SSE

 

I know this one! I saw an 88 Corvette up close, and I am planning on putting in my EGR this way, since I'm using the L98 Corvette heads. The Corvette EGR has a tube that goes from the #8 spot on the exhaust manifold, over the valve cover, and into the port on the back of the intake manifold. Corvette intakes and all aftermarket intakes have this, so your best bet would be an aftermarket intake. There is no AIR tube on the #8 spot on the exhaust manifold either, only #2, #4, & #6. I wish I had pics, but I dont, yet.


------------------
1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

Thank you all, I think I'm pretty much squared away on this issue,

Jason