Since no one reads the FAQ section, i am going to post this in the technical as well. Please read.
VACUUM LEAKS answer that drives me crazy.
IN RESPONSE TO THE LINK OBOVE!
While some good points are made here not all are correct. Even the piont you are trying to get across is not correct. The reason “check vacuum lines for leaks” is given so often is because a vacuum leak can cause a numeruos amount of problems. From cabin heating to detonation a vacuum leek can cause the problems. Ex. If you have a vacuum leek causeing the EGR to be defective you could have HARD STARTS aswell as detonation. Oh ya for all you people who disconect your EGR you are hurting the performance of your engine. The EGR does infact cool your intake charge reducein the chance of detonaion.
If you think I am full of sh** then just check in the factory service manual under the TROUBLE SHOOTING section, you will see “check for vacuum leeks” more then a few times.
You are indeed correct. Disconnecting the EGR will hurt performance, I remember reading about this on the KA forums on NICO.
As for vacuum leaks, they can cause so many problems and in the FSM it is an option for most engine problems. I have lost count of the different little problems that were caused by vacuum leaks on my KA. Almost everytime it was a vacuum leak.
Andrew.
The EGR does not reduce the intake temperature.
EGR = Exhaust Gas Return, i.e. exhaust gas is pumped into your intake. HOT exhaust gas… I know because I burned myself on the EGR system for my NX2000.
Most EGR systems aren’t even supposed to be open except under light load… i.e. cruising. Full throttle or idle and it’s supposed to be shut.
So how does it improve performance? It doesn’t.
It’s sole purpose is to reduce NoX emissions.
What it does reduce the temperature of is the combustion which means LESS power… the ECU will counter this by slightly advancing timing and lowering the amount of fuel injected.
Disconnecting it will have a negative (slightly) effect on your engine’s efficiency at cruising speeds or light load since the computer is expecting it in the mixture. Maybe in an extreme case it could cause detonation but I’ve never heard of it. Also if you’ve tuned your ECU or used a piggy back syste you’ll have tuned based on AFR anyway so it’s no longer an issue.
So as long as the system is working properly (i.e. the valve isn’t stuck open) it won’t affect the full throttle performance of your vehicle.
Disconnecting it will ALSO not affect the full throttle performance either.
The negative effects will be cruising etc and they aren’t major
My experience:
My NX2000.
I did some engine work on it (replaced the motor mounts) and when I tried to pull the EGR return line off the intake box the little plastic piece came with it and I couldn’t get glue it back on.
Until I disconnected the vacuum line to the control valve it would emit a nice “farting” sound whenever I let up on the throttle or cruised.
Since then I’ve been driving around without EGR with no major issues.
Edit: AND passed Emissions.
Yes what you say about the EGR for the most part is true. It returns exahust gas to the intake, and by doing this it cools the cumbustion. How you ask!! Because the gas that is being returned is not burnable filling a percentage of the cylender with gas that can not be inighted creats a cooler cumbustion garge. Does this hurt performance buy use ing up “room” for more A/F . No ! It would mearlly cause a rich mixture if the computer did not compensate for it. The computer knows when to compensate because the computer tells it to open via a vacuum seliniod. Thid is what I am in school for so we can argue for ever but you can just look in the factory service manual and see under trouple shooting.
Detonation
Over-advanced timing - Reset ignition timing
Defective Spark Plugs - Replace Spark Plugs
Fuel Lines Clogged - Clean Fuel Lines
EGR SYSTEM MELFUNCTION - CHECK AND REPAIR EGR SYSTEM
PCV system malfunction - Repair PCV System
VACUUM LEAK - CHECK AND REPAIR
SYSTEM
NEED MORE?
Okay I don’t want to get into a flame war but in your post you said INTAKE CHARGE which is not correct, COMBUSTION TEMPERATURE is correct, which is what I said.
Also I didn’t say it would affect performance, I said EFFICIENCY, but you’re also wrong in another aspect, disconnecting the EGR won’t cause the engine to go rich, it will actually cause it to go LEAN. The car expects less oxygen (since the exhaust would take up it’s space) so it uses less fuel, it ALSO expects the mixture to be “harder” to ignite due to the greater distance between the oxygen and gas particles so it would ADVANCE the timing in order to compensate. Before someone says it doesn’t make sense don’t forget to burn fuel you need oxygen, if you have LESS oxygen adding more fuel won’t make it burn better, you still have a finite amount of oxygen which will “burn” a finite amount of fuel.
BUT, remove that exhaust gas and you have MORE oxygen with LESS fuel, thus increasing speeding up the reaction of the combustibles, combine that with an EARLIER spark (because it advanced the timing) and you risk the expanding gases hitting the piston BEFORE it should… which is detonation.
And finally on OLDER motors the EGR system is not controlled by the ECU at all, my 1991 NX2000 with an SR20DE is entirely pneumatic.
And lastly you proved my point yourself… Detonation look at vacuum leaks, a RICH mixtre WILL NOT detonate (in the too early sense).
Whoops I misread your response as you misread mine.
I didn’t say the system had a negative impact on the actual performance, I just explained why it made no real difference in either direction since it’s only used bsaically during cruising and the computer is compensating either way.
For the part about detonation I was explaining that if you disconnected the EGR system the ECU would still think it’s dealing with it and would lean out and advance the spark thus creating a situation that could cause pre-detonation. BUT, in the situation where it’s compensating (because the EGR should be engaged) it’s usually under light load which unless something is seriously wrong it’s rare for detonation to occur anyway.
You’d get the rich mixture only if the computer didn’t realize it had an EGR system… which I would hope wouldn’t happen OR the TPS is messed up (resulting in other problems anyway)
So other than what I just explained as probably misread I don’t see how what I said was only “partly” true.
Oh and I left my post up simply because it goes into more detail anyway so someone will learn something from it.
I was not wrong here. I said it would be rich if the computer did not compensate for the egr opening. Lets recap. The Egr is to reduce NOX right. What causes NOX? High combustion tempretures!! How does the EGR reduce NOX? It reduces combustion tempratures! When is the combution temprature high? Under heavy load! This is when the EGR goes to work not at idle or low throtle. The EGR does sacrifice some power and eficientcy doing this but I would rather have a engine that is not going to blow up than a engine that has 3 more horse power, and even more so when under boost. That last statment may condratict something i said earlier and I will admit that after doing some more research and the difference is not much.
Thank you very much Canadiandrifter for your response. Finally someone actually took their time and tried to make an intelligent post. Nocwage, good job as well. I stand corrected however, and I’m glad you guys had this discussion since I learned more, and I got my facts straight.
It’s 3:30 am, and i just got home… however, I’d like to add, andrew, I would have liked better to see a post like that from you since you are the once blaming vacuum leaks for everything, and not just wait until someone posts something like this 2 days lates…
As far as I’m aware no EGR system on the market today will be open under heavy load. And definately none of the EGR systems on any 240SX .
Only light to moderately light load where you don’t even care about how much power you make.
The majority of driving is done at barely any throttle (i.e. cruising) and that’s where the EGR system runs, as soon as you put any real load on the car it cuts off since the kind people that make our cars realize we want to go faster.
Again I give the example of my NX, I drove around a bit with the EGR’s intake hose detached, the car would make a wonderful “farting” noise whenever I was just cruising, if I accelerated it would go away. (Which led to a rather up and down speed to avoid the embarassing noise)
Remember, Emissions Testing doesn’t have you floor your car, they test you at idle and test you at cruise. Car companies don’t care outside of that range
I’ve also drove a car with the opposite problem, my mom’s Sentra.
The B13 chassis with the GA16DE has a common problem where the EGR valve gets stuck open, the car won’t idle properly and runs like shit anywhere BUT cruising, acceleration etc is all hurt, even when it’s not WOT, just regular acceleration from a stop or to pass on the highway.
The car will also run rich and stink because of it.
(When i describe the symptoms to the Dealership they knew right away what was wrong, so I looked up on the net where the valve was and learned a lot about EGR in the process)
So to end this…
If the EGR is working fine it won’t affect any real performance of your car, if it’s busted it will make your car run like poopy and there are very few ill effects to just ripping it right out.
From Sentra.net:
Q: Why does my car accelerate so rough?
A: You may be in need of a thorough tune-up. Your plugs may need regapped or replaced. Your spark plug wires may need replaced. Your air filter may be clogged. Your engine may not be receiving enough fuel due to a clogged fuel filter, clogged or faulty fuel injectors, and or weak fuel pump. Your battery may not be holding a strong enough charge to fire the plugs under acceleration. The EGR system may be clogged or have a faulty EGR valve.
You are wrong here. I thought I explained it well enough when the EGR is needs to be open to reduce NOX. But I guess not .
A short chemistry lesson is in order here. It was discovered way back when, that high combustion chamber peak temperatures (the really short duration high temperatures near the end of the combustion process) caused oxygen and nitrogen to combine chemically and form these oxides of nitrogen mentioned above. Most of the anti-pollution devices of the day did a pretty good job of reducing the other bad by-products of combustion, namely excessive hydrocarbons and carbon monoxide, however they tended to induce the formation of oxides of nitrogen. Something had to be done else we would all die of smog diseases.
The automotive engineers figured that they needed to do something to lower the peak combustion temperatures which only occurred under certain high load driving conditions. They figured they could do so at the expense of power and fuel economy but what the heck, ya can’t have everything! If they could only add something to the combustion chamber that would act like sort of a fire extinguisher to cool the combustion temperatures that would do it.
So they invented a way to allow some very inert gas to get back into the combustion chamber only when needed. They needed a source of this gas - it wasn’t air, cuz that contains oxygen and nitrogen which caused the problem in the first place. So they chose carbon dioxide. Where to get a supply of carbon dioxide . . . ??? Hmmmm, how about the exhaust system? That is mainly carbon dioxide and water (plus a zillion other noxious chemicals) Suppose we allow some of the exhaust gas to get back into the intake manifold under strict control and only when we need it? That would cool the combustion chamber and prevent the formation of the NoX. Maybe we should call it recirculated exhaust gas (REG??). But a guy named Reginald voted no cuz he didn’t want his name associated with a car part, so they called it exhaust gas recirculation (EGR) since there was nobody around with that name.
Now we understand why it is there. And we understand what it does. So what can go wrong with it and what are the symptoms??
It’s really pretty simple - it can be open when it isn’t supposed to be, or it can be closed when it is supposed to be open. Not rocket science, but it is science. If it is open when it is not supposed to be open, at idle for instance, It will act like one monster vacuum leak and the engine will not idle or will idle really roughly. If it doesn’t open when it is supposed to open you will probably experience a symptom of “pinging” or “knocking” since the combustion chamber temperature will be higher than normal (one of the main causes of pinging in an engine).
As far as I’m aware no EGR system on the market today will be open under heavy load. And definately none of the EGR systems on any 240SX .
Only light to moderately light load where you don’t even care about how much power you make.
The majority of driving is done at barely any throttle (i.e. cruising) and that’s where the EGR system runs, as soon as you put any real load on the car it cuts off since the kind people that make our cars realize we want to go faster.
Again I give the example of my NX, I drove around a bit with the EGR’s intake hose detached, the car would make a wonderful “farting” noise whenever I was just cruising, if I accelerated it would go away. (Which led to a rather up and down speed to avoid the embarassing noise)
Remember, Emissions Testing doesn’t have you floor your car, they test you at idle and test you at cruise. Car companies don’t care outside of that range
I’ve also drove a car with the opposite problem, my mom’s Sentra.
The B13 chassis with the GA16DE has a common problem where the EGR valve gets stuck open, the car won’t idle properly and runs like shit anywhere BUT cruising, acceleration etc is all hurt, even when it’s not WOT, just regular acceleration from a stop or to pass on the highway.
The car will also run rich and stink because of it.
(When i describe the symptoms to the Dealership they knew right away what was wrong, so I looked up on the net where the valve was and learned a lot about EGR in the process)
So to end this…
If the EGR is working fine it won’t affect any real performance of your car, if it’s busted it will make your car run like poopy and there are very few ill effects to just ripping it right out.
From Sentra.net:
Q: Why does my car accelerate so rough?
A: You may be in need of a thorough tune-up. Your plugs may need regapped or replaced. Your spark plug wires may need replaced. Your air filter may be clogged. Your engine may not be receiving enough fuel due to a clogged fuel filter, clogged or faulty fuel injectors, and or weak fuel pump. Your battery may not be holding a strong enough charge to fire the plugs under acceleration. The EGR system may be clogged or have a faulty EGR valve.
[/quote]
With some of this post you only prove the point originally trying to make. A FAULTY EGR CAN CAUSE PROBLEMS! When the EGR is not worknig and stuck in the open posisiton it acts like a massive vacuum leek. When it stays closed it is useually because of a faulty vacuum hose. So a commaon vaccum leek can cause bad operating conditions.
arghh
I never said a vacuum leak wouldn’t cause problems… I just said you can disconnect the EGR without a performance hit.
I mean sure if you just left it’s vacuum line unplugged it’d cause problems but I figured it’d be assumed to remove.
Also PLEASE show me where you say i’m wrong, all I see is you re-wording exactly what I already said in various posts…
Please read this pdf:
http://www.autoshop101.com/forms/h61.pdf
To quote for the lazy:
High EGR Flow is neccesary during cruising and mid-range acceleration. When combustion temperatures are typically high.
Low EGR Flow is needed during low speed and light load conditions.
No EGR flow should occur during conditions when EGR operation could adversely affect engine operating efficiency or vehicle drivability(engine warm up, IDLE, WIDE OPEN THROTTLE)
Exactly what I said… It’s only really in use while cruising and it shuts off when you go heavy load.
Also I said right at the START what the EGR is meant for… sheesh.
mid range ecceleration = load !
And I always said it was on during light and moderate load…
I said it wasn’t on during HEAVY load, which is what you kept saying but anything I’ve ever read contradicts.
Ok so I am in class right now and I questioned my prof obout this depate if you want to call that. His answer was that when the EGR opens all depends on what kind of EGR it is. So with that said it would be apperent that we are both correct.
The term performace has been used a lot. What do you guys mean? I think when performance is used its meant, better for the engine, not actually more power. This might be the confusion, both might think the other person means something else.
Either way i see what nocwage is saying:
Detontation is more likely to happen at WOT (can’t argue with that), and the EGR isn’t used at WOT, another fact thats been brought up (maybe like Canadiandrifter said, depends on the EGR system, but this is with the nissan one that doesn’t open at WOT). So its purpose must be something else, for example like Canadiandrifter said: to help with emissions, and like nocwage said: to lean out at cruising speeds to reduce fuel consumption.