EGR blocked today...

[the evil twin]

As Lemo79 said, you will need to take boost control away from the ECU now that the ERG is blocked. Otherwise you will be running low boost when you least want it.

Uuummmm... never ever had low boost on mine and it was fully instrumented.
The ECU will still boost similar MAP with/without EGR overall and if anything my boost was higher till I tweaked the VNT to reduce boost pressures.
EGR block my cruise boost stayed around the same, put the welly in and the boost was momentarily higher post EGR block at around 36 to 38 PSIA
Had to tweak the VNT because of higher boost due to the EGR valve not cycling like the ECU was proggy'd to expect so reduced the MAP to around 32 PSIA max.

[Rock Trol]

Lemo and Rock Trol you make very valid points. I just went for another run and I believe it perceptible that I have lost boost and had to put the loud pedal further down to the floor as a result of the lower boost. Think I will just remove the blocker. I've already fitted the catch can, so think I'll remove the blocker and leave it at that.

Cheers for some sage advice.

Steve

it' not too hard to install a Dawes valve and needle valve (if needed). Once you bypass the connection to the air box which lowers vacuum and thus boost you will have full boost control. It will be a very linear boost curve, much nicer to drive.

its just a matter of redirecting the 4mm vacuum hoses and splicing in the valves. The hardest part is to find a boost source for the Dawes valve. My inter cooler (x country) had a port I could tap into. Otherwise you might need to weld a bung into the air pipe after the turbo.

the other option is to unblock egr and clean the intake on a regular basis. You can do this by removing and decoding or using something like wynns egr cleaner. My mechanic used the cleaner on my car last year and it breathes a lot better.

[Lemo79]

What year model Evil Twin? As you could imagine if the turbo is still pushing pressure into the intake manifold not a lot of EGR is going to get in there, it's going to take the path of least resistance which is out the exhaust, so the ECU throttles boost back to allow the Exhaust gas to flow into the inlet manifold. Just curious what year model as mine is a 06 GUIV and deffinately behaves this way.

Lemo.

[Lemo79]

I should add it is not a constant low boost, it will usually drop after you have been at cruise speed for a little while, then after a period or when you start to accelerate will come back up. But while it is low EGTs climb and if the timing was right you could hit a hill with already high EGTs getting them pretty damn high by the top.

Lemo.

[Rock Trol]

My crd used to drop from 14-15psi down to 10-12psi when cruising which is not too bad and then go higher if I accelerated or hit a hill. Being a crd it definitely controlled it better and I ran without a Dawes for 18 months without any dramas (until the 3 inch zhaust). When I installed the manual boost control the car did feel peppier and was always on boost. Much nicer to drive.

With the DI cars it may be different. When you look at the egr as part of a whole system then changing the boost control when you block it makes sense as all the fluctuations in boost are there to promote egr flow. Some cars may be more affected than others but it's interesting that you said you could feel the difference.

[steve4377]

Thanxs again people. Good advice all round. Gunna watch and shoot for the next month. Also gonna monitor fuel consumption rates. After about 80kph the extra go pedal is noticeable, but not alarming. See the rationale for the Dawes control but may just do a manifold clean every 50k if I remove the block.

My theory is that crud is mainly made of carbon. Carbon is a very poor heat conductor. When carbon is thick it retains massive heat and this causes the problem, more so than over fuelling. The heat creates local heat store areas than increase the local temp until the combustion chamber can take no more - classic reason maybe why the early failures were whilst cruising. Heat is the enemy and should be disposed of per design. Air passing through masses of hot carbon in the intake manifold must I would think raise the temp of the combustion gasses. Food for thought maybe. So if you fit catch can, Dawes and such then this may still not be enough if you don't clean out your manifold when you fit all those!

Interesting.

Cheers
Steve

[threedogs]

http://www.ebay.com.au/itm/Patrol-ZD...IAAOSwsB9WDzLX
You can buy this style boost adaptor, fits booth the Di and CRD GU

[Sir Roofy]

Thanxs again people. Good advice all round. Gunna watch and shoot for the next month. Also gonna monitor fuel consumption rates. After about 80kph the extra go pedal is noticeable, but not alarming. See the rationale for the Dawes control but may just do a manifold clean every 50k if I remove the block.

My theory is that crud is mainly made of carbon. Carbon is a very poor heat conductor. When carbon is thick it retains massive heat and this causes the problem, more so than over fuelling. The heat creates local heat store areas than increase the local temp until the combustion chamber can take no more - classic reason maybe why the early failures were whilst cruising. Heat is the enemy and should be disposed of per design. Air passing through masses of hot carbon in the intake manifold must I would think raise the temp of the combustion gasses. Food for thought maybe. So if you fit catch can, Dawes and such then this may still not be enough if you don't clean out your manifold when you fit all those!

Interesting.

Cheers
Steve

GOOD POINT you might be onto something there

[Daveyboyjunior]

The throttle manifold is surprisingly easy to remove, to be able do this job regularly as you say Steve. Better than throwing an EGR cleaner in and sending all the loose crud into your engine!
Be careful to align the pressed metal gasket correctly when you do!

Hey TD that is a great little adaptor to allow a boost connection. Nice one!

[steve4377]

http://www.ebay.com.au/itm/Patrol-ZD...IAAOSwsB9WDzLX
You can buy this style boost adaptor, fits booth the Di and CRD GU

That's as clever as clogs that is 3dogs...