nevermind, guess I didn't search extensively enough:
http://www.mr2oc.com/showthread.php?t=246786&highlight=egr

mods can delete this unless someone wants to add their :2cents:

 

Ive run about 200,000 miles with the egr disabled on the Mk1. No problems ever. One was NA, the current one is SC. All the egr does is dump non-combustable, hot exhaust gases into the cylinder during non-peak times. Cruds up the intake tract something crazy.

To disable the egr, put a bb in the hose that actuates the valve. then it stays shut.

 

Ive run about 200,000 miles with the egr disabled on the Mk1. No problems ever. One was NA, the current one is SC. All the egr does is dump non-combustable, hot exhaust gases into the cylinder during non-peak times. Cruds up the intake tract something crazy.

To disable the egr, put a bb in the hose that actuates the valve. then it stays shut.

Which raises the knock threshold. The ECU probably takes advantage of this by adding ignition advance. Removing EGR then could increase the chance of detonation.

-Rob

 

Rob, how does that really work? Doesn't it keep the intake track cooler by not re-cycling the hot unburnt gasses back in? I can't figure out how that system really works or what it really does for the engine besides the emission stuff.

 

Rob, how does that really work? Doesn't it keep the intake track cooler by not re-cycling the hot unburnt gasses back in? I can't figure out how that system really works or what it really does for the engine besides the emission stuff.

When you are cruising the egr opens and allows exhaust gases to re-enter the cylinder and take up some of the room the combustable mix normally would; ie it reduces the displacment of the engine from a combustion standpoint. This allows the ecu program to inject less fuel which translates to higher fuel mileage. The egr only opens during low load conditions. Step on the gas and the valve closes and you operate like a normal engine.

It also dumps hot hot gases into the cylinder which increases cylinder head temperatures which in turn adds to the cooling system load. Exhaust gases are dirty with burned hydrocarbon particulates and oil which coat the inside of the intake tract and make it sticky.

 

I kind of knew about the emissions function of it but I'm still not sure how it would affect detonation when deleting it, it should make the intake charge/head cooler. Shouldn't it?

 

This sums it up pretty good;
From : http://www.misterfixit.com/deton.htm

"2. Check for loss of EGR. The Exhaust Gas Recirculation (EGR) system is one of the engine's primary emission controls. Its purpose is to reduce oxides of nitrogen (NOX) pollution in the exhaust. It does this by "leaking" (recirculating) small amounts of exhaust into the intake manifold through the EGR valve. Though the gases are hot, they actually have a cooling effect on combustion temperatures by diluting the air/fuel mixture slightly. Lowering the combustion temperature reduces the formation of NOX as well as the octane requirements of the engine.
If the EGR valve is not opening, either because the valve itself is defective or because its vacuum supply is blocked (loose, plugged or misrouted vacuum hose connections, or a defective vacuum control valve or solenoid), the cooling effect is lost. The result will be higher combustion temperatures under load and an increased chance of detonation."

-Rob

 

Or better yet, right from toyota training literature;

http://www.autoshop101.com/forms/h61.pdf

 

When you are cruising the egr opens and allows exhaust gases to re-enter the cylinder and take up some of the room the combustable mix normally would; ie it reduces the displacment of the engine from a combustion standpoint. This allows the ecu program to inject less fuel which translates to higher fuel mileage. The egr only opens during low load conditions. Step on the gas and the valve closes and you operate like a normal engine.

It also dumps hot hot gases into the cylinder which increases cylinder head temperatures which in turn adds to the cooling system load. Exhaust gases are dirty with burned hydrocarbon particulates and oil which coat the inside of the intake tract and make it sticky.

You are correct about the first part. When cruising (partial throttle), EGR opens and allows exhaust gas to re-enter the cylinders and takes up some of the room the combustible mix normally would... The rest although true, is a complete red herring.

The exhaust gases are inert particles. They don't burn, but they are there. This slows down the flame front. This makes the fuel burn slower, just like higher octane gas. The purpose of it, most fundamentally is to decrease engine temperatures.

Reduced temperatures allow the engine to run more reliably with less chance of detonation/knock. It also allows you to run more ignition advance which boosts fuel economy (and power although if you are at partial throttle you don't really care about power). Reduced engine temperatures also dramatically decrease NOx emissions.

EGR is turned off at idle because the mixture isn't as homogenous as it should be at idle, and inert gases added in could cause the combustion to be unstable. Its turned off at WOT to limit so not to limit maximum power (also the car should be running slightly rich which should have a similar impact to the inert gas (remember fuel is only combustible in the presence of oxygen).

The Pros are: reduced engine temps, improved reliability, dramatically reduced NOx emissions. Cons: Well, you could probably save 2-3 pounds by removing it completely and if you are running rich or burning oil you could be putting oily soot into the intake. In all honesty, I wouldn't touch it. Its there for a reason, and it doesn't decrease power or harm fuel economy

 

so is there any benifit to deleting the egr other than having a cleaner looking engine bay?

 

so is there any benifit to deleting the egr other than having a cleaner looking engine bay?

No... Removing the EGR will increase your NOx emissions dramatically and make the engine run hotter (which has to harm long term reliability, perhaps making it easier to blow headgaskets). The only potential advantage I see (other than weight savings, which is trivial) is that your intake manifold might stay a little cleaner.

 

japanese didnt put EGR on their 4ages. *Shrugs* if the consequence was that damaging, they wouldnt have been too careless to leave it off.

 

if you have a welder and are willing to cut up the old exhaust manifold i don't see a need to machine the new manifold

If it actually helps emissions and milage i can't see it being worth getting rid of (isn't it only like 5lbs at most?)

Im no enviromentalist, but pollution is definitely real (its obvious), as well the money in my pocket from better gas milage is definitely real . Global warming im not so sure about though, just my opinion though

 

japanese didnt put EGR on their 4ages. *Shrugs* if the consequence was that damaging, they wouldnt have been too careless to leave it off.

The Japanese ECU would probably also compensate for this difference.

edit: If you study the vacuum hose diagram, you will also see that when the ECU opens the T-VIS valves the EGR is disabled. So the EGR is off above ~4,400 RPM regardless of load if your vacuum lines and T-VIS actuator VSV are working properly.

 

japanese didnt put EGR on their 4ages. *Shrugs* if the consequence was that damaging, they wouldnt have been too careless to leave it off.

This is completely misleading.

1) The primary reason why car manufacturers include EGR is to reduce emissions. Back in the 80s, the US was well ahead of most if not all industrialized countries in terms of emissions control, its now closer to the back of the pack. The Japanese neglected it in their domestic cars because it cost money and they didn't need them to meet lax Japanese emissions standards.

2) The Japanese were running speed density intake "measurement". Speed density has advantages in that it responds faster, its cheaper, and it won't get screwed up by air leaks. Its also less accurate, and would be messed up by EGR. The EGR is inserting inert particles into the intake at some times and not others. An airflow sensor would never see those particles, but they would affect the reading of a MAP sensor and the MAP sensor would have no way to distinguish between inert particles (not combustible) and air (combustible). As a result, the car would run rich when the EGR is on unless it had some magic way of compensating for stuff. A real PITA...

3) Designing a car without EGR is completely different from taking a car with EGR and removing it. The MR2 doesn't have a knock sensor. When the EGR is on, the fuel essentially has higher octane, and so you can run with more advance. If the computer bumps up the advance on ignition timing when it opens the EGR this could be an invitation for knocking (which the computer can't compensate for because it doesn't have a knock sensor) if the EGR has been removed. If the car never had EGR to begin with they wouldn't bump up the ignition timing. Big difference.

4) The whole point of EGR is to reduce NOx emissions by lowering the engine temperature. I can't believe you would suggest that a cooler running engine wouldn't be a more reliable engine. Just because it isn't necessary doesn't mean its not helpful.

I have a master cylinder brace on my car. Toyota didn't put one on from the factory. Does that make my brace unnecessary? Yes. Did it substantially improve brake feel? You bet... Three guesses why Toyota didn't include a brace with the car? Errr... I'm thinking... money, money, and ummm, for my final guess... MONEY!

 

Or better yet, right from toyota training literature;

http://www.autoshop101.com/forms/h61.pdf

whoa. OK, you convinced me. straight from the horses mouth, page 5:
"if EGR is commanded but doesn't flow, severe detonation will occur"

the engine doesn't have a knock sensor and Toyota
has documentation for this specific engine that says "SEVERE detonation
will occur". Not MAY occur, WILL.

So, EGR stays. I'll call Aaron at Lithia tomorrow. The only way i'd feel safe deleting it is using a JDM ECU.

thanks for the tech documentation & debate, I learned a lot.

 

whoa. OK, you convinced me. straight from the horses mouth, page 5:
"if EGR is commanded but doesn't flow, severe detonation will occur"

the engine doesn't have a knock sensor and Toyota
has documentation for this specific engine that says "SEVERE detonation
will occur". Not MAY occur, WILL.

So, EGR stays. I'll call Aaron at Lithia tomorrow. The only way i'd feel safe deleting it is using a JDM ECU.

thanks for the tech documentation & debate, I learned a lot.

As stated earlier in this thread, roughly 200000 miles, no problems.

 

do you run premium or 87? What's your gas mileage like?

those are 2 of the things I love about the NA MR2 - you can get 35mpg on pump gas (87) and still have fun doing it. If I had to run premium, I'd go GZE or turbo the 4age.

 

I have a JDM SC motor without the EGR. When smog tested, everything tests low except NOx, which is just below the highest acceptable. Since it was built to run w/o an EGR, no detonation. The penalty is relatively high NOx levels. Maybe if you change to a JDM ECU, it could run EGR-less without being too rich.

 

I was running my GZE (with knock sensor) EGR-less using the usdm ECU and never once heard it knock under partial throttle, and it makes no sense to me why would they put make the ECU to go on aggressive timing mode when you are at partial throttle or cruising (at least for our car). Well maybe I am just not believing the fact that it damages the engine by increasing the combustion temp, because the coolant system is more than enough to keep the engine at a safe temperature as long as it is well maintained. For the most part, our engines are designed to make the best of its power after TVIS kicks in and to be able to handle that power safely, when the EGR is off. But still I wouldnt recommend removing the EGR even if you dont have smog laws.. just for the sake of the environment.

 

I have a 3sgte with no EGR (Gen3)... my emissions were tested last week, it didn't register enough NOx (or anything else for that matter) for them to care.

It fastpassed. Basically meaning it's no where near the limit so they kill the test early.

 

I have a JDM SC motor without the EGR. When smog tested, everything tests low except NOx, which is just below the highest acceptable. Since it was built to run w/o an EGR, no detonation. The penalty is relatively high NOx levels. Maybe if you change to a JDM ECU, it could run EGR-less without being too rich.

That would have been sweet if the JDM engine came with an ECU. Then I could have used the better pink injectors with 4 holes instead of the green stock 86 ones, but as it is I am stuck with the stock 86 ecu.

As thorough as Redvalkyrie's writeup is, I just don't feel comfortable deleting EGR with a US computer. like i say, the words "will" instead of "may" and "severe" detonation right from a 4AGE specific tech document does not sit right with me.

 

irony strikes again. the red car i just bought doesn't have egr

 

I was running my GZE (with knock sensor) EGR-less using the usdm ECU and never once heard it knock under partial throttle, and it makes no sense to me why would they put make the ECU to go on aggressive timing mode when you are at partial throttle or cruising (at least for our car). Well maybe I am just not believing the fact that it damages the engine by increasing the combustion temp, because the coolant system is more than enough to keep the engine at a safe temperature as long as it is well maintained. For the most part, our engines are designed to make the best of its power after TVIS kicks in and to be able to handle that power safely, when the EGR is off. But still I wouldnt recommend removing the EGR even if you dont have smog laws.. just for the sake of the environment.

Why would they "put make the ECU to go on aggressive timing mode when you are at partial throttle or cruising"?! Because, generally speaking the more advanced the ignition is, the more efficient the engine runs. Other than emissions, the other priority when cruising is high fuel economy.

I also never said it damages the engine by increasing the combustion temp. I said that there is no doubt that operating parts at higher temperature is more stressful for them. Its a plain fact that virtually every mechanical and electrical device's failure rate goes up as you ramp up the temperature, in some cases dramatically. The coolant system may do a decent job of controlling the average temp of engine, but there's no doubt that local temperatures can be higher. I mean, let's put it this way. NOx emissions are almost completely dominated by combustion chamber temperatures. When people say without EGR they are just barely passing NOx, that clearly implies that combustion temperatures are very high. I'm glad that anecdotally, on your 1 engine you haven't had any problems, but I bet if you took 2000 engines, and removed the EGR from 1000 of them, and then otherwise treated them identically, there would be more failures in the removed EGR group.

Either way, there's no good reason to remove it. It certainly doesn't hurt anything and it definitely improves emissions, as well as as potentially fuel economy (if you have a knock sensor), not to mention it reduces the engine temp

 

I could have used the better pink injectors with 4 holes instead of the green stock 86 ones, but as it is I am stuck with the stock 86 ecu.

As a compromise, I am using the 88-89 4 hole injector with my 86 ECU. Simply with bypassing the resistor and changing the injector electric connector. My objective was not power or speed but efficiency from the improved spray pattern.

John

Don't try to disassemble your injector!