Observations With The Egr System

[Slater]

OK, I have been suspect of the EGR since the day I got the car.

I know what the EGR is ADVERTISED by automakers to do. Don't believe a word of it - it's all BS. At least the "cooler temps for less knock" crap. It's for decreased NOx emmissions, period. VADIS says the average exhaust temperature coming out of the EGR valve is 200F. You are a fool if you think that "cools" the intake charge. Garbage.

I bought a scan tool so I could track IAT temps. Well I come to find out that Volvos don't have an IAT sensor. So I bought my own IAT and installed it in the intake manifold and have been logging temps for a few weeks now. The results are shocking.

I have 3 ECUs. A stock 95 ECU, a stock 98 ECU, and a 96 BSR Stage 3 ECU.

Obviously the 96 and 98 ECUs "disable" the EGR since it is nonexistant in those ECUs.

The way the EGR works on a Volvo is this. The valve injects exhaust gas into the intake manifold at idle and part throttle. It closes the EGR valve when in boost or WOT. However the negative effects of the EGR gas are influenced even when the valve is closed as everything is super heated already from the EGR being on, so if it turns off for a few seconds whoopdie doo. It's not enough time to make any kind of real difference. What's worse, if the diaphram leaks it will exhaust gas by ALL of the time. That's great for knock eh?

I did all of my testing by averaging results on a variety of road setups. Sitting at a red light idling, driving in stop and go traffic, driving at a slow but steady speed (i.e. 35mpg on a country road), or on the highway (60-80mph).

So here's what I found.

On average my IAT temps were 73-80F OVER ambient temperature with the 95 ECU installed. That's right folks you read that correct - when the outside temp is 90F my intake temps are a cool 163F-170F! This is REGARDLESS of driving condition, and happens very soon after the car is warmed up. It doesn't matter if I stopped at a red light or hauled along at 80mph on the highway. The car feels slow and sluggish, and jerks often at part throttle which I assume is knock. How on earth this is supposed to be "good" for the engine is beyond me.

Now, regardless as to which ECU I ran - the stock 96 ECU or the 98 BSR ECU, my intake temps immediately dropped to 40F to no more than 60F over ambient temp. The 60F was in stop and go traffic and driving the car for a second trip after it sat hot. Starting out with a cold car the temps are 40F over ambient for a looong time. And when you are on the highway the temps vary from 40F to 50F over ambient. The interesting thing to note is that both ECUs feel incredible. Even the stock 98 ECU. There is no studder and the car feels fast as nuts.

I go to the dyno in 3 days to test and lot of these theories as well as the ECUs I have and some other parts I have in the works. So stay tuned for a full report.

So as you can see EGR is not you friend. The difference between 130F and 170F intake temps is tremendous and kills power horribly including increased knock. Knock is what kills rods no matter what others may say. Why do you think so many Volvos bend rods? Anyways we are talking about EGR here. The more exhaust gas gets pumped into your intake manifold, the higher your intake temps, and the more it heats up EVERYTHING under your hood - the intercooler piping, heat soaking the intercooler, etc. EGR = bad.

Now, what can you do about it? If you have an EGR equipped car you can obviously upgrade to a 96+ ECU to disable the EGR system that way. I am also working on CEL-free ways to disable the sensor without upgrading the ECUs or removing the EGR system. I will keep you posted of the results as I find stuff out.

Finally, this whole thing has been an eye opening experience. Even with no EGR we are seeing 40F-60F temps over ambient. This is terrible and the number needs to be much lower to see significant power increases and decreased knock. Why do you think your car runs so much better and faster at night? This is where better ICs, vented hoods, more efficient turbos, and cold air intakes come into play. I also have a few more tricks up my sleeve to help in this dept. Even if you can get the temps down to 20F over ambient the power increase and throttle response will be instantly noticible. On my previous normally aspirated cars I was able to get intake temps down to 5F over ambient or less. Turbo cars will be much hotter than that just due to the nature of FI, but 80F over ambient is just plain ridiculous.

[turbobrick]

how did you go about routing the EGR / blocking it off ?

car will run like stuff im guessing by just blocking off the EGR ?

my little head is turning gears..

is this a pump type system ? the EGR or does it just draw gas via crappy ducting ?

[Slater]

how did you go about routing the EGR / blocking it off ?

car will run like stuff im guessing by just blocking off the EGR ?

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I will show you on Thursday.

I haven't disabled it yet other than by using the later model ECU. I have all of the parts to do it, but the main problem is that the EGR valve is a pain in the jerk to get to.

Anyways, it's like a pumping system. The system has a diaphram and a few sensors (pressure and temperature), and the sensors dictate when the diaphram opens and closes.

I had an old carbbed 87 Honda years ago that just had a stupid pipe for it's EGR that drew exhaust gas all of the time. Very low tech. On that car I just ripped the pipe off. There was no CELs because there was no ECU!

[turbobrick]

*gets out vadis*

[turbobrick]

oh snap...

just a theory.. on EGR equipped cars why not use the pump still.. just route a breather intake from like the bottom of the car.

i mean honestly, how much would you effect the readings on the 02 sensors by accomodating additional air ?

[Slater]

oh snap...

just a theory.. on EGR equipped cars why not use the pump still.. just route a breather intake from like the bottom of the car.

i mean honestly, how much would you effect the readings on the 02 sensors by accomodating additional air ?

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I'm not following you...breather intake?

[turbobrick]

well.. esentially the gas is drawn from a brake line looking thing thats attached to im guessing the exhaust manifold..

disconnect that brake line, and reroute it to a place where cool fresh air is received.. of course you'd have to setup some type of filter on it but i was just thinking a breather/crank case ventilator could be used to filter that air.

the pump can only pump so much i'd think, from the looks of it it couldn't be much but i dont see how it would hurt it.

[Slater]

well.. esentially the gas is drawn from a brake line looking thing thats attached to im guessing the exhaust manifold..

disconnect that brake line, and reroute it to a place where cool fresh air is received.. of course you'd have to setup some type of filter on it but i was just thinking a breather/crank case ventilator could be used to filter that air.

the pump can only pump so much i'd think, from the looks of it it couldn't be much but i dont see how it would hurt it.

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The problem with that idea is the EGR temp sensor is right at the intake manifold and would never get triggered unless it saw 200F air, so the diaphram would never open defeating the purpose of your idea. Plus any new air you introduce would be unmetered which may or may not be a problem.

If you're gonna go to that trouble you may as well rip the whole pipe and all the associated crap out altogether. I think that would do the same thing as a fresh air filter but both would throw a code.

I think I know the easiest way. We'll find out Thursday.

[lax01]

how does the 96+ ECU "disable" the EGR pump? Does it stop the exhaust gas at the intake manifold? Or does the gas not even reach the IM? If its reaching the IM, then it really shouldn't be that much different, since the exhaust gases will still be creating heat in that area...I would think...could you post actual pictures of it also? I'm not quite sure on what it looks like...though I've probably seen it

[zimmy77]

so what I'm gathering is, if we can route cooler metered air(from the intake hose after the maf) to the egr while maintaining 200 degress at the sensor, we're gonna be flyin? is there a way to jumper out the sensor so it will always read 200?(as per your description of it reaching operating temp rather quickly) I dunno much about it, but i sounds like it could work. I'm willing to try it.

[kenhoeve]

how does the 96+ ECU "disable" the EGR pump? Does it stop the exhaust gas at the intake manifold? Or does the gas not even reach the IM? If its reaching the IM, then it really shouldn't be that much different, since the exhaust gases will still be creating heat in that area...I would think...could you post actual pictures of it also? I'm not quite sure on what it looks like...though I've probably seen it

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come on lax...

the EGR is not a pump, it is a valve. operation is simply closed, or with closed circuit open. so if the ECU doesn't have provisions for an EGR, the valve simply never opens.

[lax01]

ok ok, but even if the valve is closed, its still bringing unwanted heat towards the manifold correct? and if its leaking, then its allowing heat into the manifold...whats the true purpose of EGR? just emissions? how does it possibly lower emissions? by diverting the gas back into the intake flow? does it just get burned off in combustion?

[Meek]

Slater-

has your MPG dropped at all? Just asking cuz when I put an EGR block-off plate on my DSM I lost a couple of MPG's.

Hope you find a good way to drop intake temps :)

[Slater]

Slater-

has your MPG dropped at all? Just asking cuz when I put an EGR block-off plate on my DSM I lost a couple of MPG's.

Hope you find a good way to drop intake temps 

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Well, it's dropped a little but I attributed it to the BSR stage 3 ECU vs the stock ECU. Plus I am a leadfoot ;0)

I'm working on the intake temp problem.

[Slater]

come on lax...

the EGR is not a pump, it is a valve.  operation is simply closed, or with closed circuit open.  so if the ECU doesn't have provisions for an EGR, the valve simply never opens.

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Exactly.