EGRs

[Shayne]

the engine has felt slightly strangled. Like a blocked air filter almost. No, the air filter isn't blocked.

Try as in test , alternatively you could spend 30 quid on a high flow filter just to try it .

 

[Beau]

After some thought Chris, I have a strange theory to share...

You've blocked your EGR using the vacuum pipes which works... The trouble is the actual valve for the EGR is on the Intake side of the engine, not the Exit.

Is it possible that the Exhaust gases that are meant to re-circulate are causing some sort of turbulence in the system as they are traveling down the EGR pipe, but obviously on the EGR Intake it is closed and therefore they have no where to go...

In my head I can't see such a little thing affecting the engine so much but I thought it's worth sharing! I've blocked my engine with actual plates, on both sides and it's been fine

 

[Chris]

Beau, that may well be pure genius. Unfortunately, I can't say if it is or not. This is the first time I have ever dealt with an EGR and all I know is it's valve of sorts that lets exhaust product back into the airstream to be burned. There is some arrangement that means that they don't open all of the time so they are connected to the ECU in some sense.

Now, I am not trying to block the EGRs are such - not yet, I am just stopping them activating to see if it cures the black soot, which it does. But as I have said, something else is happening too. Blanking them fully would be the right answer. I know that. But I wouldn't want to do that if the net result was the same as I have now. I'd rather have the soot!



I don't know what pushes the gases through the EGR. Back pressure? Could it be that the pressure is pushing back into the cylinder somehow, strangling performance? I really have no clue as to what's actually happening.

Thing is that the EGRs are not open all the time. So when they aren't, they are in exactly the same position that they are when they are blocked. I don't know if there is some form of feedback to the ECU that says "When the valve opens, alter X setting". With me simply blocking the pipe, the valve is supposed to be open but isn't.

But people have removed them without problems and in fact have seen benefits. That's what I don't get. What do you do with all the solenoids and wiring etc?

 

[Towpack]

Exhaust gases will not 'flow' down the EGR pipe when the vales are closed so there will be no turbulence. A bit like water will not flow down a hose pipe when the nozzle on the end is shut. There will be pressure but not flow. The exhaust gases are forced through the valves by the pressure in the exhaust manifold brought about by the back pressure of the turbo and exhaust system so I would guess the ECU closes the valves during periods of low pressure, i.e., on overrun.
EGR is an emissions device aimed purely at burning any unburnt fuel in the exhaust. The recirculated gases will reduce the oxygen content of the intake air in addition to heating it, both of which are, in theory, detrimental to performance and economy. I disabled my valves and also blocked them off with some thin metal plates and did notice an improvement in economy but can't honestly say I noticed any change in performance. I opted to leave all the bits in situ so the ECU still thinks the system is working, avoiding and fault codes or warning lights on the dash. JMO

 

[Chris]

I get what the EGR is and what it does, just not in its entirety, how.

It doesn't work when the engine is cold. I have watched. Therefore it must be tied into the engine management somehow. It's not a purely mechanical system. There is trickery involved.

 

[Beau]

Beau, that may well be pure genius. Unfortunately, I can't say if it is or not. This is the first time I have ever dealt with an EGR and all I know is it's valve of sorts that lets exhaust product back into the airstream to be burned. There is some arrangement that means that they don't open all of the time so they are connected to the ECU in some sense.

Now, I am not trying to block the EGRs are such - not yet, I am just stopping them activating to see if it cures the black soot, which it does. But as I have said, something else is happening too. Blanking them fully would be the right answer. I know that. But I wouldn't want to do that if the net result was the same as I have now. I'd rather have the soot!



I don't know what pushes the gases through the EGR. Back pressure? Could it be that the pressure is pushing back into the cylinder somehow, strangling performance? I really have no clue as to what's actually happening.

Thing is that the EGRs are not open all the time. So when they aren't, they are in exactly the same position that they are when they are blocked. I don't know if there is some form of feedback to the ECU that says "When the valve opens, alter X setting". With me simply blocking the pipe, the valve is supposed to be open but isn't.

But people have removed them without problems and in fact have seen benefits. That's what I don't get. What do you do with all the solenoids and wiring etc?

From what I've read and gathered, the EGR's on these older trucks don't feed back to any form of ECU. When a certain air pressure is created in the intake, some sort of vacuum or pressure is created to activate a vacuum/pressure switch. This then activated a Solenoid which opens the EGR valve letting Exhaust gases into the intake. I believe this is generally activated above 2500RPM, possibly even lower.

Guess work here, but there's probably a vacuum created when the EGR valve is open pressure differential in the Exhaust Exit side and Intake side hence created a draft and sucking the exhaust gases into the Intake. Other than this, what stops the Exhaust gases exiting down the down pipe as per usual? This is why the only thing I can think of is some sort of air flow is disturbed and the balance is distorted... which may be why people generally use blanking plates instead of the vacuum hoses?

And regarding the wiring and solenoid, you can just leave them in place or remove them, they have no real part when you probably blank off the EGR. Actually thinking about it you may need to keep the vacuum hoses as everything is sealed?

Anyway, I think you should look into properly blanking off the EGR with some metal and see what happens then...

 

[Chris]

"Anyway, I think you should look into properly blanking off the EGR with some metal and see what happens then..."

Thing is Beau, that's exactly my point. I don't want to go to all that trouble if the result is exactly what I am getting now. See what I mean. I hear that blocking the pipes IS the same as blanking off. So if it is, all I will get is the same but lose a Saturday pissing around making plates and tussling with rusty bolts. This is why I am trying to work out 'why' so that I can work out what best to do. I can make plates, I have the gear, but I am time poor. I need to be doing other things.

 

[Jon Wildsmith]

When you blocked the vacuum pipes, did you reconnect them to the EGR valves or leave them dangling? I'm wondering if those pipes are not sealed properly now, letting some air into the vacuum system and reducing fueling curing the black smoke but not fixing the real cause just masking it.

 

[Chris]

Good thought Jon, but they are extremely blocked. Had a right job unblocking them last night. But yes I did reconnect them. Didn't really need to did I. Anyway, I shall man up and just make some plates and take them off. I am trying to get the truck ready for a possible trip into France and the days just fly by. Not got the tank in yet, because I need to to the rust treatment first. Can't do that because it keeps raining etc etc. I'll make them in ally and use a bit of exhaust paste on one and some RTV on the top two and we should be good. Don't have my new suspension yet either. Why does everything take so Goddam long in this country? Have to get my cargo system in before I can get my water tank made. With a bit of a luck and a following wind, there is an outside chance I could be nearly ready for Romania.

 

[Chris]

Well this just goes to show that knowing more doesn't necessarily make you any wiser.

Had a lunchtime look at the EGRs. I reconnected the right hand one and went for a spin. It made no difference to anything at all. I stopped and did the same with the left hand one. Instantly the engine MOJO was back. Woof. Looser, quicker and more responsive. The smoke came back, but after a bit of a 'tune up' in second it does seem to have cleared a little. Now, the valves were activating together and reliably, but odd that doing one made no difference. No, I didn't then block them the other way around to see what happened. I might do that later. Maybe only one isn't enough. Or maybe the RH one is not working properly.

Now here's the interesting (ish) bit. If I unplug the single vacuum pipe to shut them off the is a noise that disappears. Put the pipe on and open them and it's back immediately. It's a sort of tub thumping whuump whuump whuump noise in the air box. It makes me wonder if the reason that on the later 24v engines they put the attenuator on the air box top. Because of the noise generated by essentially exhaust noise getting into the air box from the intake manifold. People say it's quieter with that maybe removing the EGRs would do the same. Interested to know what you guys who have done the air box lid and the EGRs - which way round you did it.

See? No wiser.

 

[mrdelmonti]

Not familiar with the setup on 80s so this might be irrelevant but on a previous car I had the EGR valve was linked to the anti-shudder valve and blocking off the vacuum pipe to the EGR had the same effect, down on power. Turned out this was because the anti-shudder valve was essentially working the entire time, the way round it was to T off of the vacuum pipe before the blockage.

Like I said not familiar with 80s but thought it might be worth a mention.

 

[Chris]

Mr D, that's just the sort of thing I am looking for. Now I have never heard of an anti shudder valve although after my breakfast each day .....OK leaving that aside, I do feel that there is something happening here that is either as it's supposed to be or possibly not working as it should so that when I disable them things get worse rather than the same or better. I should record the noise perhaps when I connect and disconnect the pipes. it's very pronounced. Given then these things aren't supposed to be open all the time (they wouldn't have a valve other wise would they) I think that mine are basically open pretty much all the time once warmed up at any rate. They're 19 years and 217k miles old. I shall get them off tonight and see.

 

[frank rabbets]

The 80's do not have anti shudder valves.

The later air box lids had the plastic resonator chamber added as part of continual improvement. Nothing to do with egr's.

This noise Chris. Is it just on idle? There should not be any noise in the air box. There can be noise in the air box if the valve clearances have been set incorrectly or the cam belt is one or more tooth out. This noise is not intermittent though.

 

[Chris]

Evening Frank how do you know the resonator is nothing to do with that noise? I didn't actually say the adaptation was connected TO the EGRs, I indicated it might have been as a result OF the EGRs. The fact that yours doesn't make this noise and you have the modified airbox is kinda supportive of that, no? There ust have been soething to prompt Mr T to think, hmm we should make this change.

As I said, at idle when I connect the vacuum pipe it makes this drubbing noise immediately in the airbox. I know it does, because I am there when it does it. It's hard to say what happens when I rev it as the noise of the engine pretty much drowns everything out.

OK so whose bloody idea was it to take them off and block the ports? First few nuts and studs came out lovely. Well I thought this won't take long. No, not until one snapped off. The far side on the exhaust manifold!! So two and a half hours later they are blanked. Have to say so far it sounds very good. I couldn't find any problems with the EGRs themselves. All looked good to me. But without them on there the engine does seem to whoosh like it used to. Can't drive tonight I am blocked in on the drive so it have to be tomorrow.

Will make report then.

 

[Beau]

Are you sure the 80's don't have a anti shudder valve? I know on the 90 series intakes, there a smaller butterfly chamber which is a electronic anti shudder valve which only gets operated when you're turning the engine off... Even with the engine running and this closed it won't affect the Intake anyway as the main butterfly Intake will be open...

Hmm the story seems to be getting more interesting

 

[Chris]

My 24v could do with one by the sounds of it. It stops with a right bang and judder. The 12v just stops. All my 12v 80's have just stopped. But the GS is different. I'll see if it changes with the removal of the EGRs.

 

[Scott]

My 24v could do with one by the sounds of it. It stops with a right bang and judder. The 12v just sops. All my 12v 80's have just stopped. But the GS is different. I'll see if it changes with the removal of the EGRs.

Interesting observation.

 

[frank rabbets]

Chris what I meant was the resonator was fitted as continual improvement and nothing to do with egr valve problems.

Beau. No anti shudder valve on the 80. I've had the inlet system apart several times and there isn't one.

Chris on top of the fuel pump there is a hex screw with a locknut. If the locknut comes undone the screw turns round and round through 0 - 360 degrees altering the mixture. The screw does not move up and down as it's not in a thread. It may not be obvious therefore that the screw is loose. Perhaps check the nut?

Also check you have vacuum in the system and that all the hoses are secure around and below the pump.

 

[Chris]

When the EGR valve opens, there is a direct passage from the exhaust side of the engine to the induction side - via the intake system. So it stands to reason that when they open there is an increase in noise causing a resonance in the air box. I can't see how this wouldn't be the case Frank. When I connect the vacuum pipe and they open, the noise is immediate and you can tell where it's coming from. It's no mystery, it's a bank of 6 cylinders going up and down blasting out burned fuel. It's pretty apparent to me that Toyota made improvements to the induction system to combat this noise and maybe as part of overall improvements maybe, but to say that the attenuator improvement had NOTHING to do with this particular noise that only appeared when they fitted EGRs to the 24v is a bold suggestion.

Anyway, they've gone and it runs fine. The odd strangulation seems to have gone and so has the smoke too. So that's that. And it's quieter too. Odd that.

 

[warrenpfo]

My 24v could do with one by the sounds of it. It stops with a right bang and judder. The 12v just stops. All my 12v 80's have just stopped. But the GS is different. I'll see if it changes with the removal of the EGRs.

x2 mine also judders on switching off