Finally recieved my EGR plate, what do you guys think, looks a little better than the rusty old EGR valve.

 

I had to have it polished though, as it just looks so much cleaner .

 

That's a nice piece, but why are you blocking off your EGR?

 

Well, to be honest the main reason was it cleaned up the engine bay a lot. I was able to remove the EGR valve and the bracket with all the various components (and boost bypass) on the drivers side of the blower. I can now change plugs in under 30 mins without cussing . Also, it seems most tunes have it turned off anyway (I know my JDM tune did). I would have done it for how easy it makes getting at the plugs alone, but the nicer appearance was a plus.

 

Ok I got ya. You did leave the BAP sensor on though, right? You don't want to be taking that off.

Just for your own knowledge, the EGR plays an important role in keeping cylinder temps cool, which suppresses part throttle detonation. So if you start having part throttle ping issues, you know why. Removing the EGR will also drop your gas mileage. If you want to keep it off, that's fine, just be aware of the possible issues that may show up so you aren't scratching your head as to why if it happens.

 

Sal,

Thanks for openly shaing this kind of info.

I've seen you post before with answer to questions like this for guys that obviosly are not using you for tuning.

Thanks for being 'stand-up'!



Herb

 

Sal sure does appear to be a quality guy.

Sal

Rich

 

Anybody have an idea on how much the mileage is affected?

 

Can't be much... Driving techniques I'd think would have a much greater effect.

I drive like your grandpa and get 16.5ish with my mods (egr still on). Little higher out on the superslab.

Rich

 

Thankyou very much for the reply Sal, the guys are right its very nice of you to offer this information even to people who don't use you as a tuner. I am well aware of the EGR functions, I am an engineer in the automotive field (SAE member, etc) and I work almost exclusively on PCV systems, filtration and EGR functions for several OEMs such as International (powerstroke Ford), Detroit and OEM for Ford and GM. I have had my EGR removed (yes, I did retain the BAP sensor, I just bolted it onto the rear fuel rail post) for about 9 months. I did carefully check gas mileage before and after the mod as well as IAT's, EGT's, etc. The mileage was too inconsistent to make a definitive conclusion as the weather began getting much colder around the same time and we switched to winter gas. I can say its still within the same range I got before removal ~14.5mpg mixed city and highway. Thanks again for the input and I may actually be contacting you soon about a tune, plan on coming out to CA anytime soon

 

I'm still trying to figure out how NOT having spent gasses mix with the intake promotes tip-in detonation. Is it because the mixture is more volatile (without the dilution effect of the exhaust gasses mixed in)?

I always thought EGR had a "leaning" effect, which I would think promotes detonation. I thought EGR was an emissions thing (leaning out the mixture, get a better tailpipe reading).

 

The EGR injects inert gases (already burned, does not affect mixture). The inert EGR gas helps cool the cylinder temps down. The original intent was to supress NOx emmisions. But along with high chamber temps comes detonation with vehicles like ours.

 

Sal,
on a mildly modded L (4# lower, SCT tune, FTVB, CAI) is the part throttle detonation THAT risky? I REALLY want to do this to clean up my engine bay but the word "detonation" is like having a hot girl walk up to you and when you get three feet away from her you notice a mole shaped like Texas on her nose.; instant turn off.

Talk to me Goose!

 

Same discussion just came up on our local board the other day. I posted this article I found to help explain things.

The purpose of EGR (Exhaust Gas Recirculation) is to reduce the NOx emissions. Air is mainly made of oxygen and nitrogen (O2 and N2). At temperatures above 1300°C (2372°F), these molecules split apart and rejoin with each other to make nitrogen oxides (like NO, NO2, etc...). The nitrogen oxides contribute to smog formation.

EGR puts a portion of the exhaust gas back into the intake manifold, so it mixes with the fuel and air. (Note that the exhaust adds to the fuel and air; it doesn’t replace any of it). The added mass in the cylinder is harder to heat up, so the combustion events have lower peak temperatures. The lower temperatures prevent the O2 and N2 from splitting and combining. Even though the exhaust is hot, about 600°C (or 1112°F), it's much cooler than the 1300°C required to make NOx.

In summary, the exhaust adds mass, increasing the heat capacitance of the mixture (i.e. making it harder to heat up the mixture in the cylinder). Peak temperatures are lower, reducing NOx formation, which ultimately reduces smog in the environment.

The reason EGR improves fuel economy is because it reduces the engine's pumping losses. For the cylinder to move down on the intake stroke, the piston is working against the intake manifold vacuum. Another way to say it is that the vacuum above the piston tries to prevent the piston from going down. EGR increases the mass in the intake; more mass means higher pressure, or less vacuum. Now the piston has less resistance during each intake stroke, which results in better gas mileage.

I dont know how relevant the last paragraph is to a supercharged application, but I included it as the author intended.

 

What percentage of the inlet charge is fresh charge and how much is egr?

Rich