# egr



## dentedsub (Oct 23, 2007)

i just spent all day taking out the egr valve on my 4banger d21 (huge pain in the ass, like some nissan engineer was looking for ways to make it hard to remove) and not started to really notice all the many vacuum hoses that seemed to all go to random valves charcoal canisters. i finally got it out to find out it needed more than a cleaning but napa wanted almost $150 for a new one. i am not going to pay that much for a useless power sucker. i put it back on but all the vacuum hoses were ruined getting the valve off so i plugged the vacuum port that supplied the whole system. i just drove it around and saw no difference, none, and the best part, no more check engine light. anyway, i wrote this cause i'm wondering if anyone can see any long term effects this might have, cause i don't see any, and i'm curious if there is any other useless "emissions" systems that can be bypassed?


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## saudade (Apr 10, 2010)

Well, the "text book" answer is it's a violation of federal law to tamper with the emissions systems. If Utah has emissions testing, you will fail.


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## apmason (Jul 21, 2004)

I'm with saudade on this. The emissions stuff is on there for a reason. Maybe you aren't a big fan, but hey, its the answer you get. FYI, when I replaced my egr and all the associated vacuum lines, I noticed an improvement in performance, and my cel went off.


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## zanegrey (Dec 5, 2005)

egr = exhaust gas recirculator.

you may or may not notice a difference in performance or gas milage..


if you are going to replace the parts i have them used but in good condition...


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## NissanPartsDept (Mar 31, 2010)

The egr is not just a "useless power sucker".

As a matter of fact you may see a huge repair bill down the road if you don't get it working again.

Modern engines are designed to use all the emissions systems together ...... disabling one can ruin another!!!!!!!!!!


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## dentedsub (Oct 23, 2007)

NissanPartsDept said:


> The egr is not just a "useless power sucker".
> 
> As a matter of fact you may see a huge repair bill down the road if you don't get it working again.
> 
> Modern engines are designed to use all the emissions systems together ...... disabling one can ruin another!!!!!!!!!!


this is why i started this thread. i'd heard that but couldn't figure out how NOT sending hot exhaust into the intake could be bad for it. i'm just a curious guy. i'm not sure this could be called a "modern engine" the egr is 70s tech. i can't remember the exact numbers but my '79 sub with a 350 is rated for 155 hp when the '73 350 had around 210 hp. the only difference was emissions systems. 
as for legality, once i get new vacuum lines i can just plug them back in where i capped it off.
it seemed to run rich before, probably from all the little vacuum leeks.
thanks for the replies, and letting me vent a little.


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## smj999smj (Jan 1, 2006)

The EGR valve system helps prevent pre-ignition detonation by routing some of the inert exhaust gas into the combustion chamber, which lowers the combustion chamber temperatures. 96-97 HB's had some issues with the EGR valve sticking, addressed in TSB #NTB97-100. A countermeasure EGR valve to correct the problem is available, P/N: 14710-86G01.


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## dentedsub (Oct 23, 2007)

i don't mean to sound rude but that doesn't make sense to me. i don't see how a little fresh exhaust is going to prevent preignition. i don't see why its even needed when the comp ratio is like 8.6:1. this is a common idea i've read in many forums though and i feel like i should clear up some misconceptions. preignition and detonation are 2 different things. preignition is the fuel/air exploding before the spark plug lights it, usually caused by running lowgrade gas in high compression engines. detonation is random explosions of the fuel/air or unburnt fuel caused by hot spots on the cylinder wall.


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## zanegrey (Dec 5, 2005)

that made me laugh...


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## smj999smj (Jan 1, 2006)

Preignition can occur when the temperatures inside the combustion chamber get too hot. Exhaust gas is inert, meaning it doesn't burn, and routing it back into the combustion chamber will lower combustion temperatures. Many late model engines, like the 2.5L used in 2002+ ALtimas that use variable valve timing, eliminate the EGR valve. Instead, it actually sucks the exhaust gas back through the exhaust valves. This is good in that it eliminates the EGR valve system, but bad if a pre-cat deteriorates and debris is sucked backed through the exhaust valve into the engine...which is what caused many of the oil burning 2.5's until they straightened out those issues.


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## schmauster (May 18, 2010)

It will run better with all the emission stuff removed if you can retune, otherwise you might as well leave it. The problem is that the ecus fuel and timing maps are tuned for the equipment. You will get more part throttle power having the EGR off, but keep in mind whenever you are full throttle, all that stuff turns off anyways. 

I eliminated all of my stuff and welded all the flanges shut just to make the truck easier to work on and cleaner. I dont want any extra places for leaks. Im smog exempt so i dont have to worry about that stuff at least.


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