Can EGR Blank cause blown motor?

[NAV2795]

Hi all,
Recently installed a EGR blanking plate in my 2007 spanish d40 diesle. Its stopped alot of the smoke, and feels a lot better. However i was talking to a diesle mechanic and he reacons he just rebuilt a d40 due to the engine overboosting which was caused by the egr blanking plate. Is this true? thanks

 

[d22-outlaw]

Complete none sense.

 

[BJJ84]

someone correct me if i'm wrong, but the only way an engine can overboost is if there's a problem with the wastegate sticking and not letting excess boost out???

 

[NAV2795]

BJJ84 i personally think your correct. Surely if there was an overboost it would go through the waste gate? Perhaps the guy that blew his engine had a brocken wastegate?

 

[BJJ84]

or he increased the boost too much

 

[Old.Tony]

I call "mistake" (rather than "bullshit", because not everyone knows the conditions the EGR works under).

The EGR valve is closed at full throttle, so under the heaviest load you can place on the engine, there's no difference between blocked & unblocked. It's also closed at idle (so your engine doesn't stall) and is only really opened during mid-range throttle application.

Overboost is caused either by deliberate action - cranking it too high - or an issue with the turbocharger.

 

[tweak'e]

some engines can overboost with blocked egr. patrols with there crap boost control can do it.
i havn't heard of it with D40's because they have better boost control.

odds are mechanic probably had a seized turbo vanes. sometimes they stick. even then i have my doubts high boost caused engine failure.

btw no wastegate with d40's as they are variable turbo's.

 

[NAV2795]

Thanks for the info, But what exactly is a variable turbo? does it somehow release excess pressure to prevet over boost? cheers

 

[Old.Tony]

In the Garrett 206V (fitted to D40s) the vanes around the impeller (which sucks in fresh air and compresses it) are opened and closed by a turbocharger actuator. With the vanes closed, the turbo produces no output, so there's no chance of overpressuring the intake or the engine - as long as it's working properly.

 

[Black_Outlaw]

The vanes open and close via a vacuum controller..

The more vacuum, the more they close and the more boost..

http://www.youtube.com/watch?v=CbdY1rymBJg

 

[tweak'e]

In the Garrett 206V (fitted to D40s) the vanes around the impeller (which sucks in fresh air and compresses it) are opened and closed by a turbocharger actuator. With the vanes closed, the turbo produces no output, so there's no chance of overpressuring the intake or the engine - as long as it's working properly.

nope sorry tony.

the vanes are on the exhaust side.
they close to make a smaller hole which increases exhaust gas velocity to spin the turbine faster to make more boost.

one big advantage is closing the vanes increases exhaust back pressure to make egr flow into the engine.
now if the egr is blocked the exhaust isn't bled off and the back pressure will rise and exhaust gas velocity through the turbo will increase spinning the turbine faster making extra boost. if the ecu is dumb it won't change the position of the vanes and the turbo can overboost. if the ecu is smart it reads the increase in boost and opens the vanes to lower backpressure and gas speed.

 

[Black_Outlaw]

nope sorry tony.

the vanes are on the exhaust side.
they close to make a smaller hole which increases exhaust gas velocity to spin the turbine faster to make more boost.

one big advantage is closing the vanes increases exhaust back pressure to make egr flow into the engine.
now if the egr is blocked the exhaust isn't bled off and the back pressure will rise and exhaust gas velocity through the turbo will increase spinning the turbine faster making extra boost. if the ecu is dumb it won't change the position of the vanes and the turbo can overboost. if the ecu is smart it reads the increase in boost and opens the vanes to lower backpressure and gas speed.

Is this why people notice boost come on earlier when they have the EGR blanking plate in place... Or is it because clean air is the only thing entering the combustion chamber?

 

[Old.Tony]

I learned something new. Never bothered to check what I'd been told about the turbo and I should have. No matter.

If the EGR is blocked there'll be more available pressure (in the mid-range only) than normal. You ought to notice that in low to medium throttle applications as extra boost - but the ECU can back that off, so it'll probably just result in what feels like a faster spool-up, which is what it is.

Thanks Tweak'e for straightening me out!

 

[tweak'e]

If the EGR is blocked there'll be more available pressure (in the mid-range only) than normal. You ought to notice that in low to medium throttle applications as extra boost - but the ECU can back that off, so it'll probably just result in what feels like a faster spool-up, which is what it is.

and thats about it.

but remember that extra boost creates more exhaust gas which makes more boost. the catch with variables is the control system. vac operated ones, i'm told, are slow in operation. so if the ecu is a bit dumb and the control system is slow its very easy for the boost go rise faster than the control system can react, resulting in overboost.
however i don't think thats a problem for the D40.

 

[Old.Tony]

That'd be why they changed to the electronic version in the 2011 (maybe late 2010) models. Just a shame they mucked that up and so many had to go back to be replaced!

 

[NAV2795]

thanks for the replies, good leason

 

[DieselTuner]

Its actually the exhaust side that has the variable geometry.

Good video too.

 

[Tappet]

Ok that's interesting. Thanks! Never had a good hard look at the turbo but I to thought it was the compressor side.

One thing I did notice in blocking the EGR is just off idle, its a bit better but say if I give is light throttle say to 2000 rpm or so then all of a sudden floor it. (which is rare i may add) It certainly feels like it has more mid range punch. So perhaps bit of over boosting happening in that situation? It's a Thai built truck so has the vacuum actuator.

Might have race out and get myself a boost gauge now

 

[Teleman191]

Very interesting reading about the turbos's. if the d22 turbo is a waste gate turbo, is it still vnt? Bit confused.

 

[DieselTuner]

No its not.

A wastegate vents excess exhaust manifold pressure before it contacts the turbine wheel to control intake boost pressure.

A VNT/VGT turbo moves the vanes to control nozzle pressure at the turbine choke point.

Basically you can use a relatively small exhaust wheel and tight nozzle actuation to get a turbo to spool up very quickly. Then, make the nozzle pressure low by opening the vanes which acts as a very large A/R turbine housing.

You can achieve a similar effect by using a wastegated turbo and a very large external wastegate to vent the same pressure, the effects are not quite as good as a VNT and the packaging of such a setup becomes problematic in an OEM situation.