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Old 05-08-2015, 01:15 PM   #1
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Default possible boost creep?

Finally have my mx5 based kit car on the road. Getting it properly tuned on the rolling road in 3 weeks so I'm mainly trying to test all my hardware is working properly.
Spec (in brief) is:
1.8bp engine
ms2
td04 turbo from WRX
rx8 injectors
water to air intercooler
3" diy exhaust

I have a boost control solanoid setup but have it on wastegate pressure (signal taken at the inlet manifold) to be safe until I get it on the dyno. Anyway I had to relocate the wastegate actuator and used a saab one that is supposed to open at 5 psi. Have done a few datalogging runs and was a alarmed to see close to 11 psi and high inlet temp. I have tested the wastegate and actuator operation with a bike pump on the signal line and it works ok. Can't confirm the pressure.

I was wondering if boost creep could be the cause. I guess that is the wastegate opening but failing to bypass enough gas. However my gut feeling is that its not going to happen on a mild setup like this. The boost seems to taper off and then increase again during a roll on.

Anyway here is a datalog of a 4th gear roll on. Closest I could get to dyno conditions on the road. If someone with more experience then me could take a look at it and let me know what they think that would be appreciated.
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File Type: msl 2015-05-08_15_modified.msl (612.6 KB, 95 views)
File Type: msl lukeszero.msl (253.6 KB, 97 views)
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Old 05-08-2015, 01:44 PM   #2
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Quote:
(signal taken at the inlet manifold)
Picture or better description of the location of the WG signal source, please.

You can also disconnect the WGA arm and wire the WG open to know for sure what kind of creep is due to Turbo / Exhaust manifold / DP. On my TD04, with segregated downpipe, I get about 5psi at 7k RPM with WG wired open.

11 psi sounds like a high WGA setting, or a leak somewhere. Take off the line from the WGA. Pull the arm out, plug the nipple (finger will do). If is retracts, then the diaphram is bad.

If your Air-Water were working properly, 11 psi should not cause high MAT. Are you the guy we tried to discourage from such a set-up?
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Old 05-08-2015, 02:05 PM   #3
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Quote:
Originally Posted by DNMakinson View Post
Picture or better description of the location of the WG signal source, please.

You can also disconnect the WGA arm and wire the WG open to know for sure what kind of creep is due to Turbo / Exhaust manifold / DP. On my TD04, with segregated downpipe, I get about 5psi at 7k RPM with WG wired open.

11 psi sounds like a high WGA setting, or a leak somewhere. Take off the line from the WGA. Pull the arm out, plug the nipple (finger will do). If is retracts, then the diaphram is bad.

If your Air-Water were working properly, 11 psi should not cause high MAT. Are you the guy we tried to discourage from such a set-up?
WG signal is taken from the first nipple engine side of the throttle body. I will try your idea tomorrow of wiring the wg open and see what that does and also try the original subaru wastegate if I can make a bracket to mount it.

I am indeed the guy you tried to discourage from such a setup. That being said I have tried to use large radiator, large pipework decent pump to get the heat out as quick as possible and I really can't imagine fitting a reasonable sized air/air unit in the nosecone.
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Old 05-08-2015, 02:14 PM   #4
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move that source to pre-tb or you'll have massive boost spikes
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Old 05-08-2015, 02:17 PM   #5
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Quote:
Originally Posted by 18psi View Post
move that source to pre-tb or you'll have massive boost spikes
Precisely. To fight creep, connect to turbine outlet. To fight droop, connect just Upstream of the TB. To create havoc, put it Downstream of the TB.
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Old 05-08-2015, 02:24 PM   #6
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Excellent! Knew I was doing something wrong.
Care to elaborate why? I can see why the signal would be higher at the turbo outlet - not sure why post TB is bad.
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Old 05-08-2015, 02:27 PM   #7
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because with a partially closed butterfly the manifold see's a whole lot less boost than the rest of the system
making your turbo huff its lungs out trying to catch up
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Old 05-08-2015, 02:54 PM   #8
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Thanks! I'll try it straight off the turbo nipple tomorrow
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