1995 850 Turbo Replacement engine has EGR

[dtmmoore2]

I have purchased a Volvo 850 B5234T engine. For some reason it has EGR whereas the engine it is replacing does not and my mechanic says this is an issue. What are my options?

Thanks for any advice.

[Ozark Lee]

The engine is all the same. The differences are on the intake and exhaust manifolds. If you need to use the exhaust manifold from the EGR engine for some reason just get a threaded plug and plug off the hole.

...Lee

[dtmmoore2]

Thanks for this!

[dtmmoore2]

I was thinking about this some more after talking to my mechanic. The original engine did not have EGR and the replacement does. He does not want to switch manifolds. Am I right in thinking that this means that there is more to an EGR system than what's attached to the engine? Or put another way, if I really wanted to, could I have a functioning EGR system in a car that originally didn't have one without having to make additional upgrades to the car itself (except of course swapping in the EGR equipped engine itself)

I was lucky not to have had check engine light or emmission test problems with my original non-EGR engine. Does swapping in an EGR engine and plugging the hole as you have suggested have any effect on whether or not I am likely to have any headaches with emmission testing or any check engine light issues. Akso, my car was equipped with LED indicator self-diagnostic system. Will this continue to work with the replacement engine?

[erikv11]

I replied in your other thread but will make this comment here: it is pretty easy to do but I can not recommend installing EGR. If you do, then in addition to the visible hardware in the engine bay you would need to get an ECU with EGR on it. And you will probably need to clean it out real well before you install it, they get crudded up pretty badly.

The diagnostics is a function of the ECU (engine computer, basically) so yes it will all be the same. You are not touching the ECU in a standard engine swap.

[Ozark Lee]

The EGR is completely contained outside the engine block. It consists of a threaded hole in the exhaust manifold, a stainless steel pipe that leads from the hole in the exhaust manifold to the EGR valve and an EGR control valve. The EGR control valve monitors the temperature of the EGR valve and reports that temperature to the ECU. The ECU takes that temperature information and calculates an EGR flow rate and the ECU, via the EGR control valve, modulates the vacuum to the EGR valve. The modulation in vacuum to the valve alters the EGR flow rate. The exhaust gases flow through the EGR valve to a hole in the bottom of the intake manifold which is located just behind the throttle body.

If your car did not originally have EGR then the ECU in the car is not programmed to control it. I suppose you could hook it back up but it won't do anything other than possibly stick open and make the car run poorly. Why your mechanic doesn't want to leave your original mainfolds on the car is a mystery to me but to each his own. It is always my preference to keep as much of the original setup as possible, largely because of situations like yours where the emissions control systems vary between the original engine and the donor engine.

So long as you leave the original ECU in the car you will retain the OBD-I and OBD-II diagnostics. If the donor engine is running properly then you should continue to not have a Check Engine (Lambda) light and the car should pass the emissions tests as before. If you try to create a hybrid emissions system by somehow trying to install the EGR system then there is a chance that the car will fail emissions testing since the ECU isn't programmed to deal with it.

You are way over-thinking this. EGR is not an upgrade, it is an inelegant solution to keep federal regulators happy. It actually robs the engine of performance since it tires to re-burn exhaust (Primarily CO) rather than oxygen all in the hopes of capturing a tiny percentage of unburnt fuel which is an even more infinitesimal percentage of the exhaust.

Number six in the 2004 Darwin Awards will give you a rough visualization of how EGR works.

http://www.snopes.com/horrors/freakish/darwin04.asp

EGR is not in any way a part of the engine any more than the chrome exhaust pipe tip is.

...Lee

[dtmmoore2]

Thanks very much for this info. It goes with what I was thinking. EGR is just another potential headache that robs performance. As as long as I am not setting myself up for emission testing problems I am happy to not have it and as you said I would need to get an EGR compatible ECU for it to work. To be clear, the replacement engine as I remember it came with at least the exhaust manifold still attached. My mechanic wanted to save time by not going through the process of removing the non-EGR configured exhaust manifold from my old engine, removing the exhaust manifold with the EGR off of the replacement engine and finally installing the old exhaust manifold on the replacement. I think instead he wanted to work around this by plugging the hole and I guess leaving a non-functioning EGR attached to the manifold. With both engines sitting on the garage floor, the job of keeping the original manifolds on the car through the process I describe above I am told could be done in fifteen minutes and I believe all that would be required is a new gasket - does this sound right?

Thanks again to you and the previous poster for the info/advice and for leading me to a more fuller understanding through the troubling vizualization of number 6!

[Ozark Lee]

You've got it correct. To put the original exhaust manifold back on is real simple. Each exhaust port has its own gasket so it will take 5 small gaskets rather than one big one and the only real risk, albeit small, is breaking a stud while removing the old manifold. The studs are standard auto parts store fare so parts aren't an issue to source if one gets broken.

If he wants to leave the manifold and plug up the hole then that is perfectly acceptable as well but it is never any easier to "stage zero" an engine than when it is on the engine stand. Part of the 'stage zero" process is to replace as many seals and gaskets as possible. I always change the camshaft seals, the rear main seal, the intake and exhaust manifold gaskets, the PCV system, the timing belt and all of its component, and the turbo oil return gasket and O ring. One other thing that is somewhat Volvo 5 cylinder specific, is to change the O rings in the oil sump. Those O rugs are problematic and changing them while the engine is in place is much harder than doing it on the engine stand due to clearance issues.

...Lee

[abscate]

I'm going to spend all weekend trying to scrub the visual of Darwin 6 from my head, thank you very much.