S

spitfire

Active Member
Hi, The service continues and I thought I would have a look at the egr valve as I know they can be troublesome. After fetching it off it all looks a little oily with some carbon deposits but I would like to check it's operation.
Does any clever person out there know what kind of pressure is required to lift the valve. I've had a bike pump on the diaphram up to 20psi and it doesn't budge, any ideas and is it a problem if it doesn't open, presumably a jammed open valve is worse?
Cheers
Ian
 
I have no idea, but the Turbo Boost Pressure is around 1atm (14.7psi - 1bar) so if it has to operate against that, then I am surprised it didn't lift at 20psi.
 
They are vacuum operated I think as there is a small vacuume hose that connects to the valve.

Best thing you can do is fit an EGR bypass to stop any more of the dirty exhaust crap from getting into the engine.

Done it to mine, now much better and slightly better MPG

;)
 
2.0_hippo said:
They are vacuum operated I think as there is a small vacuume hose that connects to the valve.

Best thing you can do is fit an EGR bypass to stop any more of the dirty exhaust crap from getting into the engine.

Done it to mine, now much better and slightly better MPG

;)
Click to expand...

I agree
:)
 
The pressure needed to make it work is 14.7 psi. But that is pressing on the opposite side of it. You know, the side that the vacuum is not sucking on. They are vacuum operated not pressure operated. 20 psi into the vacuum port could have knackerd it good and proper.
 
Last edited:
Just replaced mine with an Allisport unit. 15 minute job, and on first impressions (10 mile drive to the local tip & back), are that it seems a smoother with a bit more torque. I seems to change gear a bit more readily, where as before it would seem to hang on a bit longer before changing up.
Bit too early to make any assumptions about fuel economy, but averaged 24.7mpg on tonight run, will report back after a tankful. It usually averages between 19-21mpg on my short trips to work, so any improvement on that would be welcome.
 
They're vacuum operated! You could fit a dump valve and start an argument:D
But I'd settle for chucking the EGR valve in the bin cos it can't go wrong then!
 
I ain't mad then! I definitely noticed a difference once bypassing the EGR on my td6 ! Engine was smoother !

They do make a difference when bypassed lol
 
It depends how much they do and at what time they open in the driving cycle as to how noticeable they are, and obviously this is only compounded with age gunge and faults
 
No measurable difference with my EGR disabled, maybe I'll try blocking it off at the next service.
 
I think that when you notice a major difference it means it was faulty! Or if you replace it it removes a big restriction as in td5! 300tdi poses no restriction so I'd be surprised if it was noticeable unless faulty! Assuming your inlet system isn't clogged up:)
 
The restriction value of the EGR valve is much over stated unless it is clogged solid. The only time removal of restriction would have much effect is at low RPM when turbo pressure is low. At all other times air is being blown into the engine and providing the intercooler is clear the engine will never lack air.
 
wammers said:
The restriction value of the EGR valve is much over stated unless it is clogged solid. The only time removal of restriction would have much effect is at low RPM when turbo pressure is low. At all other times air is being blown into the engine and providing the intercooler is clear the engine will never lack air.
Click to expand...

I disagree, the recycled air is much warmer than 'normal' air from the intake, the intercooler can't possibly cool it as well as the usual air. Removing this recycled air means the intercooler isn't getting hot air and can keep it a more uniform heat ..

I also question the viability of re-burning already burnt air/diesel mixture ... when what we mostly want to do is get clean air into the engine .. from a performance point of view.

Ecologically it might make a little sense, but empirically, my MOT smoke test readings from after removing the egr to before, are way lower and are now miniscule, whereas with the egr they were halfway to failure ...

Burning clean, cold air is 'a good thing' .. burning warmed recycled air isn't .. ;)
 
I am not gonna enter the argument (this has been through the ringer a number of times previous) - I just want to check something.....

You said the Recirc. air goes through the intercooler.....I thought the charged air goes through the intercooler first, then picks up the recirc air from the EGR then into the manifold...???

Or am I wrong and the charge air goes throught the EGR first then into the intercooler before being inducted through the manifold..!!??
 
Actually you're right .. a nice cool charge of air gets heated up by burnt air before going into the engine .. same principle .. why bother with air filters etc then?

The EGR drops the hot air in after the intercooler, my bad, sorry!
 
Paul D said:
I disagree, the recycled air is much warmer than 'normal' air from the intake, the intercooler can't possibly cool it as well as the usual air. Removing this recycled air means the intercooler isn't getting hot air and can keep it a more uniform heat ..

I also question the viability of re-burning already burnt air/diesel mixture ... when what we mostly want to do is get clean air into the engine .. from a performance point of view.

Ecologically it might make a little sense, but empirically, my MOT smoke test readings from after removing the egr to before, are way lower and are now miniscule, whereas with the egr they were halfway to failure ...

Burning clean, cold air is 'a good thing' .. burning warmed recycled air isn't .. ;)
Click to expand...

Think you really need to read what was said. Block your EGR by all means if you want to. But there is no need to replace the unit with a bypass type device because the air flow restriction on the EGR valve itself is nether here nor there on a turbo fed engine. EGR reduces NOX production by cooling the combustion gas.
 
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