968 Turbo boost problems whilst mapping

Talk and Tech about turbocharged 924/944/968 cars
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Thom
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This is only guessing from looking at the interface as I have never used VEMS myself, but if you are in "Absolute" pressure mode, then the "Boost Valve OFF Below This Pressure" may not be active?

You may still switch to "Relative" pressure mode and set "Boost Valve OFF Below This Pressure" to different values to see if it makes a difference.

Does turning on the boost controller below or above the wastegate spring pressure make a difference?
'90 944 turbo

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Willy Wabtec
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Thom wrote: Thu Apr 10, 2025 1:16 am This is only guessing from looking at the interface as I have never used VEMS myself, but if you are in "Absolute" pressure mode, then the "Boost Valve OFF Below This Pressure" may not be active?

You may still switch to "Relative" pressure mode and set "Boost Valve OFF Below This Pressure" to different values to see if it makes a difference.

Does turning on the boost controller below or above the wastegate spring pressure make a difference?
Fool around and find out 😏
Last edited by blueline on Thu Apr 10, 2025 7:23 am, edited 1 time in total.

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Rickuk1
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Just a quick update Thom kindly put me in contact with Dave Chapman who is a whizz with vems. Dave has helped us set up the boost tables correctly and looked over our logs. Things are definitely improving. It looks like we may have a boost leak and or some sort of choking problem as suggested earlier on this thread I’ll update when we find out what it is.

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ealoken
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Want to share any logs of your pulls?

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Rickuk1
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ealoken wrote: Fri Apr 18, 2025 1:12 am Want to share any logs of your pulls?
I’ll ask Will if he can

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ealoken
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Here is my log from last night.
OE IC is the next choke point, see the IAT and EGT rising.

GTX3576 G2 turbo, full boost by 4000 and out.

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Thom
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Rickuk1 wrote: Fri Apr 18, 2025 1:10 am Just a quick update Thom kindly put me in contact with Dave Chapman who is a whizz with vems. Dave has helped us set up the boost tables correctly and looked over our logs. Things are definitely improving. It looks like we may have a boost leak and or some sort of choking problem as suggested earlier on this thread I’ll update when we find out what it is.
Any udpate?
'90 944 turbo

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Rickuk1
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Thom wrote: Fri May 02, 2025 5:09 am
Rickuk1 wrote: Fri Apr 18, 2025 1:10 am Just a quick update Thom kindly put me in contact with Dave Chapman who is a whizz with vems. Dave has helped us set up the boost tables correctly and looked over our logs. Things are definitely improving. It looks like we may have a boost leak and or some sort of choking problem as suggested earlier on this thread I’ll update when we find out what it is.
Any udpate?
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ealoken
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there is your problem :)

not uncommon.

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Rickuk1
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After taking the wastegates off Will found that one of the diaphragms has a tear and the other wastegates which looks has heat resaltes damage to the control pipes as you can see above. This obviously is affecting achieving boost. Will has ordered new silicone hoses and a new diaphragm so hopefully we have resolved the problem. The only other thing is one of the wastegates is obviously getting a lot hotter that the other with the citation of the metal body which could be related simply by its location the other wastegates is lower down the manifold and has more air circulation. Any thoughts on this?

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