EGR Discussion - split topic

[OR-Zman]

G-E wrote: a "simple" system exists on my k-car.... there's a vac line infront of the throttle body, same as the Z... but there's no solenoid "off switch" so it's always opening when there's sufficient vacuum.... (it's a flapper door much like the heater core door)

and I can tell you having tested different types of intake, including ram air, that the k-car ecu is definately not tuned to deal with a higher efficiency intake, the car doesn't ping or anything but it becomes gruff and feels like it's breaking up, but as the timing is 8 degrees stock on 9.5:1 that could be cured with added timing and 94 octane.... still not much point

the ram air made a huge difference when flooring it at highway velocity, I could actually pass reasonably quickly (read: less than eternity), but the moment I let off and start cruising is would get choppy, touch the gas and everything back to normal except for the unwanted acceleration

in both cases, the Z and the K don't activate the egr idle, the throttle is closed and the vacuum port is outside, only light throttle will create vacuum on the Z and lets say due to the restrictive intake design the K suffers from more vacuum at greater throttle positions

I know how the car breathes, it's almost like a turbo, I have to close it to get some engine vacuum going and pop it open to increase VE to get anywhere, but steady state running will trigger the egr and it can't turn it off..... the Z can

Now that is an interesting point. Every once in a while I get a "rough" running condition on the Z if I let it lug for more than a few seconds. I have played around with it and it is re-creatable, but it is fixable by shutting off the car for 30 seconds or revving it hard 3-4 times. This typically happens in city driving. Ive often suspected that it was the EGR being blocked off (NA headers) so I didn't have a lot of choice.

Ive also noticed some slight inconsistency, but hardly noticeable to most, in the lower rpm range (below 2500) when cruising in town below about 40 mph. I often suspected vacuum leaks but Ive exhausted those possibilities and reserved myself to the EGR without a good reason why before now. :?

Anyhow, interesting stuff. Much appreciated here. 8)

[got boost?]

300zxt wrote: The JDM VG engines didn't have an EGR system at all.
then be consistent and run the JDM ecu tune

300zxt wrote: I dont have a problem trusting the engineers who built our cars myself.

They designed/tuned the car to run with egr.

[300zxt]

If you bothered to read this thread entirely, as you obviously havent, you would've notice that I already said that using the stock ECU and removing the EGR will result in an overly rich situation.

300zxt wrote: The only thing that might be an issue is that the stock ecu might over/under compensate the a/f mixture but a stand alone or any other means of ecu modification would fix that.

Please read before you just chime in...

I dont plan on running the stock ECU for long, and most people who have tuned it i.e Jason, tune it to the point where removing the EGR has zero negative effects.

[84z31]

are you talking turbo or nonturbo?

i have completely removed mine and i have no issues with it running to rich. i just recently had my exhaust redone. there is no black build up from running to rich.

[quote]300zxt wrote: If you bothered to read this thread entirely, as you obviously havent, you would've notice that I already said that using the stock ECU and removing the EGR will result in an overly rich situation.

The only thing that might be an issue is that the stock ecu might over/under compensate the a/f mixture but a stand alone or any other means of ecu modification would fix that.
Please read before you just chime in...

I dont plan on running the stock ECU for long, and most people who have tuned it i.e Jason, tune it to the point where removing the EGR has zero negative effects.

[300zxt]

You can still be running rich and not have soot built up, you need an AFR gauge to accurately measure a change in mixture. I dont know that it does richen the mixture to a certain fact with it removed, I'm just taking a guess that it does because the air/fuel ratio wont be exactly what the ecu has mapped for with the EGR blocked up. It very well could do nothing at all, and the maps were never reprogrammed to compensate for the EGR; who knows. That goes well beyond the scope of most peoples knowledge I think, unless one of us was an engineer at Nissan in the 80s? lol

[G-E]

the Z ecu closes the egr whenever it senses you need performance, like when you are cruising and floor it, you still have adequate vacuum to but it would impede performance to keep it open

I think this is one of the misunderstood points, the ecu is tuned around the egr in the sense that when you want power it turns it off, it decides this based on the various sensors, so depending how you drive you might rarely trigger it, or it might be open half the drive

when you push the pedal to accelerate and the ecu adds fuel to accomplish this, even if there's a slight lean condition and timing is a touch advanced in this map point, you will be safe with the added fuel (this is assuming factory tune), so it is indirectly controlled by the go pedal, you might tick once or twice at high boost which is why extra octane will help here

also when going from boost to closed throttle and cracked open, it would pop the egr for the split second you had the vacuum which is replaced by boost, but you've just lowered the engine air capacity so you end up with a buffered bov effect but into the engine

if you argue that you never had a problem with no egr, that is like saying I've never had a problem with theft so I don't feel we need locks and keys

[84z31]

the egr in my opinion does nothing except make it a greener running engine.

the mixture is controlled by the computer. the computer makes desicions through the oxygen sensor. it reads the mixture and adjusts how the injectors put fuel into the engine.

[G-E]

in my opinion locking doors doesn't mean anything either

[MrwassmanNA2T]

G-E wrote: in my opinion locking doors doesn't mean anything either

it just means the thieves have to break more stuff to steal what they came for.

[Jason84NA2T]

If someone else has something meaningful to add to this thread (such as a wideband datalog containing several minutes of regular driving before/after EGR removal) PM me and I will unlock it.