I have noticed with datamaster that the egr system doesnt function/no duty cycle above 70 mph or so. I use tunercat but cant seem to find how or why its doesnt work at those speeds. Any ideas on how to recalibrate it to work at higher speeds???


thx

 

I dont remember the exact tables, but there is a minimum RPM for the EGR and maximum as well. If i recall theres also a minimum/maximum MAP reading section too.

They should be in the same table that has fan cutoff temps and all the variables.

 

I have tried adjusting those but it still shuts off @70+

 

Do you have a reason you need it on?

 

Unless its hard coded (anyone know?).. the only reason it would be shutting off at 70+ would be if its not in the allowed RPM range OR not in the right MAP range either... Check your logs and compare it to the program i guess?

 

yea kinda curious of that myself

 

because I can't drive 55 lol


so its suckin more gas with no egr

 

Is there some reference you have that says EGR improves gas mileage?

 

yes there info out there. It not only reduces NOX but also partially fills the cylinders during cruise to lower fuel requirements

 

I'm not 100% sure of this but if EGR recirculates exhaust gases back into the combustion chamber, the car would be replacing the air coming from intake with this recirculated air. This would also mean that there is less metered air coming in through the maf while EGR is functioning (Hence less "fuel" being used). So the statment that it's lowering "fuel requirements" may be true.... But that is only because its detecting less air coming in through the MAF. When you mix "already" used air back into the system you will make less power... it may reduce combustion temperatures because there is less "boom" going on in the combustion chamber because the air is a bit "mixed", but i don't think it would improve milage any.

On top of that, I belive the computer adds additional spark retard when the EGR is in use, which of course means less power... [EDIT] It Actually adds spark advance not retard, just checked tuner cat.

The whole reason for EGR is to reduce emisisons, which usually is counter productive to power and efficiency.

So anyhow, I'm not tottaly sure if my thinkings right, but it's what makes sense to me right now There are a lot of sites saying a malfunctioning EGR could hurt fuel ecomomy - TRUE... but I didn't see much saying that a working EGR gives better milage VS a car running off of no EGR.

 

EGR does nothing to save gas.. In fact a few have found that the computer has "adders" to add fuel when EGR is on

As well as spark

 

Where is this?

The gas mileage concept does not make sense to me.

 

The info I refer to may be in a text book of mine, most websites only seem to indicate it ONLY is for NOX. (again) Its main purpose is for emissions, and a side benifit is that it displaces some of the air/fuel in the combustion chamber and uses some of the unburnt fuel in the exhuast . the egr system itself is metered as well as being controled be the computer. As for adding fuel when egr is operating I have only seen the canister purge being the only fuel adder ,at the same time I have seen the LT fuel trim lower when egr and canister purge are on. I havent heard of anyone trying to make more power at cruise anyway so as for a loss in power I cannot say. BTW- the debate between gas mileage (egr vs. no egr) is mute point because more than likely it wasnt the only leadfoot mod performed to a vehicle. I was refering to my car that has few mods (no cam,no stroker no blower no turbo, no RR's) just a cat back, CAI, t/body. You can always try it for yourself , however it seems to be the customers who notice the difference more often then us who drive differently with every mod.

 

Shall we continue with this debate because it seems the orginal purpose of the post has been lost

 

Just extra info for the original poster.... LT4=no factory EGR (enough cam overlap to render it unneccessary). EGR performs an emissions only function.