18 replies to this topic

[TerrA LX]

Can an EGR valve on a red 6 cause over heating or running problems if it is not functioning properly?

[rodomo]

Yes. It will run lean and idle rough.
At the end of the diaphram is a valve that stops exhaust gasses entering the intake manifold until the thermal switch opens which then allows ported vacuum to open the e.g.r at cruise.
If the valve is stuck partially open it is a vacuum leak.
This is common on older engines at they become carboned up.

[TerrA LX]

So it could also cause it to run hot and ping at medium throttle i take it?

[rodomo]

If it's idling O.K. and you can adjust the mixture, it's probably not the e.g.r.

[GML-31]

sounds like the timing to me.. too advanced

[Dr Terry]

Hi Guys.

The EGR can do one of 2 things if it's faulty.

1.If it's stuck open, the engine will have a lean, rough idle because it will act like a manifold vacuum leak.

2. If it's stuck closed, (because it's frozen or the diaphragm is inoperative), then the engine will ping & get hot, simply because the EGR system not doing its job.

The whole idea of an EGR valve is to dump exhaust gas into the inlet mix to REDUCE combustion temperatures. The only way to fix it is to richen the carby (worse fuel economy), retard the timing (loss of performance) or fix the EGR valve. If the engine is stock, it's best to get the EGR working properly.

EGR valves are misunderstood, they do NOT cause loss of power or excessive fuel consumption. They are not open at idle or full throttle.

If the engine is not stock, (it might have a different cam or head) then the dissy & carby will need to be matched on a dyno to suit the new combination & then the EGR can be eliminated. If this is not done, then performance & economy won't be optimised.

Dr Terry

[TerrA LX]

2. If it's stuck closed, (because it's frozen or the diaphragm is inoperative), then the engine will ping & get hot, simply because the EGR system not doing its job.

Dr Terry

This is exactly what is happening.
Thanx DrT.

[GML-31]

here you go for everyones interest...

EGR Valve

The Exhaust Gas Recirculation (EGR) valve sends some of the exhaust gas back into the cylinders to reduce combustion temperature. This is required because nitrous oxides (nasty pollutants) form when the combustion temperature gets above 2,500 degrees F. This is as a result of the formation of nitrous oxides when the nitrogen in the air mixes with the oxygen. When it�s sunny, the nitrous oxides from the exhaust get together with the hydrocarbons in the air to form smog. This is when the EGR valve comes in handy. By recirculating some of the exhaust gas back through the intake manifold to the cylinders, we can lower the combustion temperature. Lowering the combustion temperature lowers the amount of nitrous oxide produced. Consequently, less of it comes out the tail pipe.

In a typical automotive Spark Ignited engine, 5% to 15% of the exhaust gas is routed back to the intake as EGR. The maximum quantity is limited by the requirement of the mixture to sustain a contiguous flame front during the combustion event; excessive EGR in an SI engine can cause misfires and partial burns. Although EGR does measurably slow combustion, this can largely by compensated for by advancing spark timing. Contrary to popular belief, EGR actually increases the efficiency of gasoline engines via several mechanisms:

Reduced throttling losses. The addition of inert exhaust gas into the intake system means that for a given power output, the throttle plate must be opened further, resulting in increased inlet manifold pressure and reduced throttling losses.
Reduced heat rejection. Lowered peak combustion temperatures not only reduces NOx formation, it also reduces the loss of thermal energy to combustion chamber surfaces, leaving more available for conversion to mechanical work during the expansion stroke.
Reduced chemical dissociation. The lower peak temperatures result in more of the released energy remaining as sensible energy near TDC, rather than being bound up (early in the expansion stroke) in the dissociation of combustion products. This effect is relatively minor compared to the first two.
EGR is typically not employed at high loads because it would reduce peak power output, and it is not employed at idle (low-speed, zero load) because it would cause unstable combustion, resulting in rough idle.

There are two types of EGR valves. One operates through the use of a vacuum, and the other operated through the use of pressure. Both types allow the exhaust gas in to lower the combustion temperature when it gets too high.

[rodomo]

Interesting stuff!
So, Dr Terry, what would be the main difference between and non e.g.r 202 and an e.g.r 202 that stops the non e.g.r 202 from this pinging? Cam? Jetting? Dissy?

[Dr Terry]

Interesting stuff!
So, Dr Terry, what would be the main difference between and non e.g.r 202 and an e.g.r 202 that stops the non e.g.r 202 from this pinging? Cam? Jetting? Dissy?

Correct, it is a combination of cam timing, ignition timing (centrifugal & vacuum) & carburettor fuel curve.

Dr Terry

[FastEHHolden]

Sometimes you can free them up by puting your fingers into the back of the diaphram and moving it....once you get it moving start the engine up and move the diaphram...if the idle changes then the passage isn't blocked.

[TerrA LX]

I've just realized that this thing is redundant cause it's got extractors, would this still play a factor as stated above?

[FastEHHolden]

So if the egr is hooked up and functioning....then at cruise it should be running very lean (unless a blanking plate has been fitted and seals correctly on the bottom of the manifold.).....Take the vacuum line off, plug it and go for a run.

[TerrA LX]

So if these things are redundant im barking up the wrong tree then.

[TerrA LX]

Actually had a look at the bottom of the manifold 2day and there is no blanking plate fitted.

[LHSL]

Sorry to revive an old thread. The top hole on an EGR equipped intake manifold is it supposed to go through outer skin of manifold? Cleanining out the old six.
Cheers.

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[LHSL]

I have had idling issues with the car so rebuilding the carby. That top hole for EGR feeds through to intake manifold mine was blocked.
Cheers

[claysummers]

Put a blanking plate between the mani and EGR valve at the very least. You don’t want inert gas in your intake charge, you want fuel and oxygen.


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[rodomo]

EGR shouldn't be open at idle. I'd look elsewhere.