i was reading threads about boost pressure and how a stock turbo on a lly won't usually make more than 23 to 25 psi but can handle 35 or so?? is that correct? i've got and edge box w/*** and i never see more than 23-25. but my question is why not? with all the fuel and timing added, how come the boost pressure doesn't change? one guy says it's because of vvt. how does it all work together? but most importantly, is the truck actually making more boost pressure than what the edge box reads?
thanks

I am wondering the same thing. I have my truck on level II with my PPE econo. I notice the additional power but the boost pressure has remained at a max of 22 PSI. Not sure why. I read that increased boost pressure keeps EGTs down, I would have thought they would be up a little.

I wonder if a boost stick would help?

32 Lbs boost is the max that a stock turbo will be efficient. The Edge box, will only read so much boost by default. You could be making 30+ Lbs and the Edge will only show what it is capable of reading. Which I think is 26Lbs max if I remember correctly.

You need a real boost gauge that will give you real numbers.

I have the edge and I haven't read or heard anything about it only reading 26lbs of boost. I had my warning set at 32 and have had it go off so I know the edge will read and display more than 36. A mechanical guage is the way to go, especially if you have a boost stick as it fools the computer into thinking it needs more boost.

Alan

Good info Alan. I stand corrected.

so if the edge box is only reading what it thinks it see's, but the turbo is actually producing more boost pressure, am i recieving the max level of power from the edge in a given setting and how exactly does the edge know what's it's doing if it's not recieving or reading the correct data?? huh

Good info Alan. I stand corrected.
You can stand half correct and half corrected.:D The early edge modules weren't able to read/display boost over a certain pressure. I don't remember what the exact number was, but 26-27psi sounds about right. . That was corrected years ago.

More boost will lower egt's and adding a few pounds over stock is still well within the stock turbo's effective range. Boost stick will lower egt's but the ECM and Edge module will think that it is still running stock boost levels. Your edge display might say 25psi when a mechanical gauge says 31psi.

Either way ....32 psi is the max sweet spot on big tunes with vvt . 22 psi is stock .

thanks for the info... i just need to break down and invest in a set of gauges.

You can stand half correct and half corrected.:D The early edge modules weren't able to read/display boost over a certain pressure. I don't remember what the exact number was, but 26-27psi sounds about right. . That was corrected years ago.

Man I knew I only saw 26 LBs on my old Edge setup.....Thought I'd gone crazy for a minute there.:o:

There is a large disparity. 32 psi is a once proclaimed limit espoused by a few folks who were running on the ragged edge, near the failure limit. It was a trial and error determination of the choke point. That was before induction overhaul. Induction overhaul adds around 6 psi to this failure limit.

I still find no smarts in running at 38 psi, but that is the eq limit with the Induction Overhaul Kit. It will run quite comfortably now at 30 psi, with reasonable vane position 25 degrees less.

The actual limit is not a psi limit, it is a combination of factors. Elevation for example, dramatically reduces that 32 psi. RPM above stock does also.

take it from me guys i have the kennedy boost stick. It was nice and kept egt's down but with the turbo now pushing more then 32 psi of air my head bolts could not take it for long and I had to ready my head gaskets, Warrenty covered it for now, but if not it would have been a 12 thousand dollar job.

My dad just had to do his head gaskets and it was only a couple thousand more to just buy a new engine so that is what he did.

GM also told me that the LLY gaskets seperate because of getting dirt in the engine. thats what they told me and I got my warranty,, but they never did know that I had the boost stick.

I am wondering the same thing. I have my truck on level II with my PPE econo. I notice the additional power but the boost pressure has remained at a max of 22 PSI. Not sure why. I read that increased boost pressure keeps EGTs down, I would have thought they would be up a little.

I wonder if a boost stick would help?
I run ppe on level II and am experiencing exactly the same thing. I have manual gauges and it seems like boost built quicker w/o PPE. The added power is still noticed but where is the extra boost?

With the VVT boost is controlled to whatever the ECM commands. More fuel/power doesn't mean more boost. The ECM will compensate for the increased heat and exhaust flow that would create more boost on a non-VVT or wastegated turbo by opening the vanes to let more exhaust escape and keeping the boost at the commanded pressure. The manufacture of the tuner would have to program the tuner to make more boost over stock for you to see it on a gauge.

When I had my edge and my ppe boost valve, I saw 30-32 often on my edge.

I've got a boost stick, edge, and a mechanical gauge. I've seen 31 lbs.

take it from me guys i have the kennedy boost stick. It was nice and kept egt's down but with the turbo now pushing more then 32 psi of air my head bolts could not take it for long and I had to ready my head gaskets, Warrenty covered it for now, but if not it would have been a 12 thousand dollar job.



Read THIS (http://members.cox.net/td-eoc/Timing%20the%20Diesel.pdf). It will help explain why over-boosting to reduce EGT is perhaps the most foolhearty concept in TD circles. 32 psi is nothing to your head studs. But it does result in the perfect recipe to precipitate an eruption. The irony is in the reality. The EGT gauge has probably done more harm than good to anyone who believes that increased boost is somehow benefecal.

http://members.cox.net/td-eoc/Timing%20the%20Diesel.pdf

The problem with exceding 32 pounds with a vvt turbo is that the fall out of there effiency range if you push excessive amounts they have been knowen to come apart. There are guys running over 40 psi on stock headbolts and gaskets. As far as the boost that is being read by the edge is that it is read from an electonic sensor which does not have a history of being the most accurate. For a true boost reading a mechanical gauge should be installed.