Let us discuss the EGR system

Someone decided to start a knife fight on one of my youtube videos discussing the methods of deleting the EGR on my SVX engine.

His claim was that the EGR system reduces adiabatic flame temperature in each cylinder and this was done for engine longevity purposes. He said that deleting the EGR would result in an engine that would "burn up."

I agree that the EGR reduces cylinder temps thus reducing the production of NOx compounds, but I do NOT agree that lack of EGR would result in poor engine longevity.

I went to do more research on this and wasn't finding anything conclusive about it's use in motorsports or it's effect on longevity.

Thoughts?

FWIW, Chrysler can get the cam profiles just such that an engine can have "internal" EGR and not need the external EGR valve and associated bullE36 M3. Most of their crap motors can last 150k on the hard parts no problem. Plus most of the vehicles that get their EGR's deleted, don't live or lead easy lives after deletion.

Well, I remember the SR20VE was a recent example of an engine that passed NOx emissions tests (on a roller) and it was not equipped with an EGR.

In response to Taiden, if you read it on the interwebs it MUST be true, right?

Ok, while your "friend" has the right idea of lower combustion temps, he's also barking up the wrong tree.

You (and he) are correct that the primary use of EGR is to reduce peak combustion temerpature, which lowers the formation of NOx.

A very interesting secondary effect- when done correctly, EGR can also be used to reduce pumping losses, which can increase fuel economy. This actually can also increase combustion efficiency via less spark retard needed to not knock. HOWEVER we are talking a system here. EGR reduces combustion efficiency just by being there and can increase knock sensitivity thanks to its high temperature. So it takes a whole lot of work to get fuel economy benefits from EGR. Possible, even probable, but freaking hard.

Now, where your friend is barking up the wrong tree- so EGR can be used to lower combustion temps- cool (great pun there ). But it's pretty pointless to do that when you are trying to make maximum power. And when you are running max power, one is allowed (and gernally expected to) ignore emissions requirements, which actually puts absolute peak temps/pressure right when you don't want EGR what so ever. The second point- even IF combustion temps were a problem, or, far far more likely, exhaust temps are a problem- it's significanly more effective to go rich. Both for temperature AND for any spark benefits.

Race cars are put together to make them not have a temp problem, although I think many still do based on the soot you see after a 24hr race. But when racing, best power will be around 12-12.5:1. Not that it helps your argument much.

No way in heck will you compromise pumping via VCT or EGR when you can just go a little more rich.

I don't see the point of eliminating EGR. It's usually worth a significant boost in fuel economy.

Taiden wrote: Well, I remember the SR20VE was a recent example of an engine that passed NOx emissions tests (on a roller) and it was not equipped with an EGR.

One is not forced to have EGR. Don't put it on if you don't need it- cost money.

Note that the 2010 EcoBoost equipped SHO, Flex, MKS, MKT do not have EGR as well. Nor does the 2011 F150 with EcoBoost.

Horse puckey.

On one hand, you get a decrease in AFT, which only matters during the power stroke and only heats up the engine internals during combustion of the gases right next to the walls. Note that one of the reasons to go with fewer, larger cylinders is to decrease the surface area for a given volume, and that's important because the fuel and air get too cold to burn next to the edges. This boundary layer also saves your pistons from the worst of the heat.

On the other, you are mixing in 1200-1500 degree exhaust gas to your intake air stream. That'll heat up the engine internals all the time!

The GM Quad 4 family didn't have EGR. The later 2.4 Twin Dual didn't either IIRC. Anyone know about the Ecotech series?

alfadriver wrote: One is not forced to have EGR. Don't put it on if you don't need it- cost money. Note that the 2010 EcoBoost equipped SHO, Flex, MKS, MKT do not have EGR as well. Nor does the 2011 F150 with EcoBoost.

Sure, they are direct injected. They don't need EGR, they can use excess air to reduce NOx. You can do that with funky combustion space shape and the ability to direct fuel exactly where you want it. Get a small kernel of flammable mix near the spark plug, surrounded by air, which is just as inert as exhaust gases as long as you can keep fuel out of it.