Dawes valve question

[phum]

Hello All,
I read on an obscure US. site about fitting a Dawes valve to a later model liberty CRD (looked like my 2006 model)
Has this been done here and do the vehicles that we have here benefit from the fitment?
Peter

[cmohr]

I'm not too sure, from a bit of reading, it's mostly about overboost, which, I'm unsure we really have an issue on our CRD's. I know, Glen, basiclly made his CRD EGR valve a work similarly to it, as our EGR does let the overboost away, he cut off the pipe that runs around to the inlet, and he said it does that relief whoosh when it releases, but, this is only with a GDE ECU tune, that only uses the EGR to relief overboost, not vent the gases. I'll see if I can find his write up here, also some people have done similar over on the LOST site.

Read THIS before atemping anything.

http://www.ausjeepoffroad.com/forum/...5&postcount=10

[phum]

After reading this I may have a concern. Mine has about 20% ecu tune with the egr disabled in the tune. I also have the egr pipe blanked at the inlet manifold end flange. I am now wondering if the ecu sees overboost where can this go with the egr pipe blocked

[glend]

Blocking the EGR pipe at the manifold, on stock ECU software CRDs, will prevent the stock software feature which blips the EGR valve open momentarily to prevent compressor overboost (which will damage the vane adjustment mechanism over time). This software feature is retained in the GDE tunes, but other so called tunes I don't know about. The vacuum operated EGR valves, on the 2006 and 2007 CRDs, can be repurposed to operate as a dump valve, but only if you have a GDE tune. You cannot repurpose the EGR on stock software models because it will want to open the EGR valve in line with its original programming and you will destroy drivability.
I consulted Keith at GDE about converting my EGR valve to dump to atmo instead of dumping into the exhaust, and he had no issues with it. So in my case the oem EGR pipe around the back of the engine is removed, the exhaust manifold port is blocked, and the EGR valve now dumps overbooked to at no via a short stub pipe. At least I can hear it working now so I know when it would happen. I should point out that if your running the GDE tune this happens anyway, it just blips the overboost into the exhaust manifold through the EGR pipe. So you gain nothing in terms of functionality, but you can hear it. The danger of course is that the ECM software can never be returned to stock, so don't let some Jeep dealer touch it.

So short answer to your concern, yes, blocking is bad in standard configuration because there is no where for the overboost to go except back through the turbo vanes (vane bounce or slamming). But if you vent the EGR to atmo, instead of to the manifold, then you can block at the manifold.

[glend]

In addition, avoid the US intake elbow replacement kits which eliminate the Flow Control Valve (FCV). The FCV provides the necessary diversion of the intake pressure out through the EGR valve. If you use the straight through intake pipe the engine can never bleed off overboost, prevent compressor stall, etc so it will eventually destroy the turbo.