exhaust
Postmaster
Joined: Aug 2003
Posts: 4,483
Likes: 2
From: Central Texas
I think I have this right but the Manifold Absolute Pressure (MAP) sensor should limit boost or at least read it. The PCM controls everything. We don't have a waste gate because we have an electronically controlled hydtaulically actuated variable geometry turbo. Say that fast. The PCM reads the exhaust back pressure and MAP. When the human steps on the accelerator, the PCM senses the back pressure and through the VGT control valve, closes the vanes to focus more exhaust on to the turbine blades, making the turbo spin faster and creating more boost. Boost is again sensed by the MAP. There is no turbo speed sensor. Pressure is sensed by the MAP and the VGT vanes are opened under high map and exhaust pressure.
Former Vendor
Joined: Mar 2004
Posts: 4,362
Likes: 3
From: Hendersonville, NC
Originally Posted by SBV45
I think I have this right but the Manifold Absolute Pressure (MAP) sensor should limit boost or at least read it. The PCM controls everything. We don't have a waste gate because we have an electronically controlled hydtaulically actuated variable geometry turbo. Say that fast. The PCM reads the exhaust back pressure and MAP. When the human steps on the accelerator, the PCM senses the back pressure and through the VGT control valve, closes the vanes to focus more exhaust on to the turbine blades, making the turbo spin faster and creating more boost. Boost is again sensed by the MAP. There is no turbo speed sensor. Pressure is sensed by the MAP and the VGT vanes are opened under high map and exhaust pressure.
Senior User
Joined: Dec 2003
Posts: 152
Likes: 0
From: NorCal ,ca
I'd be interested in this wastegate idea. I have a 3.5" downpipe to 4" out b4 rear tire, no cat of muff, straight pipe. I've been getting alot of check engine lights but so far none have been related to the exhaust, as far as I know. The dealers have taken care of the check engine lights each time w/o saying anything about my exhaust except for compliments. I'm beginning to think that i would have less problems with a muffler though. Right now, sometimes the turbo flutters up and down after a long (1 hr. driving or more) trip at idle. It doesn't sound right. We'll, I'll keep the thread updated on any new developements. P.S. Predator to arrive Friday! 
Post Fiend
Joined: Oct 2002
Posts: 11,314
Likes: 4
Coogan -
only prob with wastegate is the same as an exhaust brake - your just signing away your warranty....
but u WON"T have an idle problem once u get that predator ---
Heck, you'll feel disappointed if you're idling !!!
get ready for the "Predator Grin" when you first push that throttle past the "easy" point!
only prob with wastegate is the same as an exhaust brake - your just signing away your warranty....
but u WON"T have an idle problem once u get that predator ---
Heck, you'll feel disappointed if you're idling !!!
get ready for the "Predator Grin" when you first push that throttle past the "easy" point!
Post Fiend
Joined: Aug 2002
Posts: 5,324
Likes: 1
From: Denton,TX
Why not just use a boost gauge and be done with it? I can't imagine that modifying a turbo that had already had issues in some trucks (you may need warranty work on it at some time) would be a good idea.
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Former Vendor
Joined: Mar 2004
Posts: 4,362
Likes: 3
From: Hendersonville, NC
The best way to control your peak boost pressure is to install a blow-off valve on the boost line. It is not related to the turbo, and can cause no damage. It is nothing but a self-seating valve that can be set a speficified pressure level to vent anything above the level you set. That will control your maximum pressure, and installation is nothing more than drilling and tapping somewhere along the pressurized side of the intake.
Postmaster
Joined: Aug 2003
Posts: 4,483
Likes: 2
From: Central Texas
Originally Posted by PSD 60L Fx4
The best way to control your peak boost pressure is to install a blow-off valve on the boost line. It is not related to the turbo, and can cause no damage. It is nothing but a self-seating valve that can be set a speficified pressure level to vent anything above the level you set. That will control your maximum pressure, and installation is nothing more than drilling and tapping somewhere along the pressurized side of the intake.
Former Vendor
Joined: Mar 2004
Posts: 4,362
Likes: 3
From: Hendersonville, NC
Originally Posted by SBV45
I have a picture of a crashed helicopter I was piloting when the boost relief valve opened prematurely during a maximum performance take off. What do you mean can cause no damage?
But on our trucks, no harm would be done if the valve stuck open...you would just lose some boost until you fixed the valve. Many of the rice turbo cars use blow-off valves in place of wastegates. Its as simple as it is effective.
Former Vendor
Joined: Mar 2004
Posts: 4,362
Likes: 3
From: Hendersonville, NC
Originally Posted by Skipped_link
I thought that the problem was over spinning the turbo, neither a wastgate or a popoff valve wound slow the turbo down would it?
As for overspinning, I have not heard of it, however I am not denying it as an issue. Someone else may know about it around here.