EGR and turbo....I don't understand....?

[nel5on]

I have a Merc c270(old one) and did a EGR delete on it with a small electrical shunt, but that got me thinking....

My merc has 18psi when the turbo comes on, if the EGR is open at the same time, what stops the 18psi inlet pressure purging into the exhaust?
Is the exhaust pressure higher? or can it purge back into the exhaust...maybe this helps the cat temps?

[Rich]

The boost is lost to exhaust. The EGR system isn't activated under conditions that would affect drive, it's usually lower Rpm and boost conditions. Common issue on modern cars is the EGR failing open due to carbon buildup then loosing all driveability because they won't run as an N/A. Blanking the EGR is the best thing you can do IMHO.

[nel5on]

I guess that explains why my car now likes to wiggle its tail....when before it was more unwilling.
Guessed it was getting more boost....now just need to remove the swirl flaps, as I can hear they leak under boost.

[composimmonite]

I've just removed and blanked off the EGR system on my 300TDi Discovery. The pipe from exhaust to manifold was almost completely clogged with carbon. Not sure about actual valve but just glad I've got rid of a useless piece of additional complication to the engine.

[nel5on]

This Merc uses a MAP sensor to regulate the EGR, so if the pressure does not drop when the EGR is meant to open, it faults into limp mode.
So 2 resistors and a diode do the trick on the ECU, and all the EGR gear just become redundant and unused.

[Rich]

May 18, 2015 15:36:58 GMT composimmonite said:

I've just removed and blanked off the EGR system on my 300TDi Discovery. The pipe from exhaust to manifold was almost completely clogged with carbon. Not sure about actual valve but just glad I've got rid of a useless piece of additional complication to the engine.

I'm amazed there are still 300TDi engines with EGR left on.. Someone got to mine before me

[Deleted]

I used to run a modified Vectra B and when towing long distance I would have to stop and replace the EGR because it would clog up, I kept a spare in the boot. I eventually fitted a blanking plate.

Now I always remove and blank the EGR on cars I buy

[althebass]

I too blank EGRs if fitted.
A copper coin can work or a steel plate depending on fitment.

[Thrasher]

First modification I did on my mk4 golf TDI was remove the egr assembly entirely and replaced it with an aftermarket pip with a boost guage outlet. Sorted....bit more turbo noise..less gunk in the system and perfect for when I remapped it. :-)

[hario]

2.7cdi 5 cylinder? Mind telling me how you can tell the swirl flaps are leaking boost, presumably past the worn spindles?

I can hear a leaking /whooshing sound when under boost but I just thought that was normal turboturbo sound because race?

[nel5on]

Jun 17, 2015 14:27:26 GMT hario said:

2.7cdi 5 cylinder? Mind telling me how you can tell the swirl flaps are leaking boost, presumably past the worn spindles?

I can hear a leaking /whooshing sound when under boost but I just thought that was normal turboturbo sound because race?

Look for oil leaks on the inlet system, this will lead the way to your problem.

[hkr91]

I bought a blanking plate for £2.50 off of eBay and fitted it to my Focus 1.8 TDDi... Before I fitted it the inter cooler pipes were saturated with oil and she would blow smoke always when booting... (170k on the engine). After fitting the plate immediately the smoke lessened and upon removing the inter cooler hoses to get to the engine there was hardly any oil residue in the pipes.

[hario]

Jun 17, 2015 19:43:47 GMT nel5on said:

Jun 17, 2015 14:27:26 GMT hario said:

2.7cdi 5 cylinder? Mind telling me how you can tell the swirl flaps are leaking boost, presumably past the worn spindles?

I can hear a leaking /whooshing sound when under boost but I just thought that was normal turboturbo sound because race?

Look for oil leaks on the inlet system, this will lead the way to your problem.

I just don't understand how one would 'tell' there is a boost leak occuring without any other symptoms, asside from oil leaking out. I suppose that is the symptom.. lol

[sparkyt]

My understanding of the valve is that it adds oxygen to the cat on start up to get the temp up quicker as the cat works better and the overall net is the car has less emission from start up . .

[nel5on]

Jun 17, 2015 19:43:47 GMT nel5on said:

Jun 17, 2015 14:27:26 GMT hario said:

2.7cdi 5 cylinder? Mind telling me how you can tell the swirl flaps are leaking boost, presumably past the worn spindles?

I can hear a leaking /whooshing sound when under boost but I just thought that was normal turboturbo sound because race?

Look for oil leaks on the inlet system, this will lead the way to your problem.

Swirl flaps are a known problem on Mercs and BMW's, in markets outside the EU these were not fitted and had none of the problems that "swirl flap" car can have, one is leaking via the spindles, the other is the flap being ingested by the motor, this can have big problems, a expect when any metal passes through a motor.

I can hear leaking when the turbo comes on, on my Mondeo this was a split pipe, on this I have checked...nothing is clear to show leaking, but the motor under the inlet looks a little wet with oil.


Mostly, I understand you will only hear a turbo when it is purging off air(other than the "whistle" turbos make), either via a "waste-gate" of some description or a leak, coming on boost slowly, you should only hear leakage until the full boost is achieved, then the waste-gate will purge off the extra air.

On the EGR fix, mine now gets 55-60mpg (on the dash) on a longer run. 45mpg is the average.

[bortaf]

Jun 19, 2015 8:52:52 GMT sparkyt said:

My understanding of the valve is that it adds oxygen to the cat on start up to get the temp up quicker as the cat works better and the overall net is the car has less emission from start up . .

My understanding is the EGR adds ex gasses to the inlet charge to cool the burn, doesn't add O2 as there is/should be no O2 left in the ex cos it's all just been burnt ?
Modern cars run high comps ratios and that causes high upper cylinder temps that create NOx, hense the need for cooling, the trouble is Ex gasses contain soot which when cooled by passing into the inlet settle out onto the cool surfaces inside the EGR and clog it causing itthe valve to stick