Question about my race tune

[08dmaxxx]

While cruising the boost consistanly rises up to 10, back to 0, up to 10 and back down, it will do this in every gear, also under 1/2 throttle it will fall on its face then boost will pick up and will do this unless i get more agressive with it or boost is already above 10 psi. During WOT i see high as 45psi. This is a stock trans/turbo. If someone with extensive knowledge could take a look at it and tell me what they think might be the issue send me a PM and ill email you the file.

[JoshH]

You see 45 psi on a boost gauge or in a log? If that is what your boost gauge is showing, that is way too high for a stock charger. If you see 45 psi on a log (looking at the info from the GM.Boost2_DMA PID), that is perfectly fine and normal. The boost fluctuations could be caused by a poorly mapped boost table where there is a very steep rise in desired boost pressure. Small fluctuations in fuel quantity can cause the boost pressure to spike up and down if the boost rise isn't smooth and gradual in the normal cruising areas. I have also heard of some guys having trouble with boost fluctuations from the EGR not being properly disabled or blocked.

[bballer182]

I would agree with Josh.

[08dmaxxx]

This is on my boost gauge and its tapped in my intercooler tube, EGR is not blocked or disabled(that i know of). Boost will sit around 37-39 on WOT and will spike to 42 then 45 and back down to 38ish.

-Josh what is you email? It wont let me PM you for some reason, probably not enough posts.

[Dmaxink]

I would say go back in and look at your tuning as well, x2 on what Josh said

[JoshH]

This is on my boost gauge and its tapped in my intercooler tube, EGR is not blocked or disabled(that i know of). Boost will sit around 37-39 on WOT and will spike to 42 then 45 and back down to 38ish.

-Josh what is you email? It wont let me PM you for some reason, probably not enough posts.joshh81 at live.com

[Boost]

You see 45 psi on a boost gauge or in a log? If that is what your boost gauge is showing, that is way too high for a stock charger. If you see 45 psi on a log (looking at the info from the GM.Boost2_DMA PID), that is perfectly fine and normal...

Great informative reply. May I ask why it's fine to see the high reading in the log? Is it consistantly inaccurate say for example 5 psi higher than actual boost? Does it have something to do with where or how it's measured? I have seen 42.7 psi on a TechII when the LMM first came out in '07

[Dmaxink]

It goes by "absolute pressure" the guage is so when you see 14.7 or 15 that is absolute pressure and the boost is actually 0. So say your seeing 40 on the log, that would actually be 25 (40 minus 15). This is referenced by rpm and mm3. Also, be aware that vane position is the deciding factor to rather you do, or do not hit your desired boost. If you see in your log desired boost not being hit by your actual boost take a look at your vane positions, just be mindful of where you are going, you should not see yourself needing to up the maximum vane position tables as of you. 36(51) is as high as i would push the charger... i have not seen much benefit after that.

[Boost]

Thanks

[killerbee]

While cruising the boost consistanly rises up to 10, back to 0, up to 10 and back down, it will do this in every gear, also under 1/2 throttle it will fall on its face then boost will pick up and will do this unless i get more agressive with it or boost is already above 10 psi. During WOT i see high as 45psi. This is a stock trans/turbo. If someone with extensive knowledge could take a look at it and tell me what they think might be the issue send me a PM and ill email you the file.

look at EGR position, commanded and actual, to see if it is opening/closing with your cycles.

[SGFastMax]

i was having the same prob on an 07 lmm. thanks for the info