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+T boost issue

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Drunk_Babies

Member
Joined
Jun 3, 2020
Location
Spokane WA
B230F+T
LH2.2
Red 315cc injectors
15G
3bar FPR
EZK 117 conversion
541 Turbo ECU
Stock MAF
740 Intercooler / Piping
NGK BP7ES @.035 gap
Manual turbo control, max 12-13 PSI
Compression last tested at 170-175# on all cylinders
20lbs vacuum at idle
12 deg. advance timing

I think that's all the relevant info, let me know if I'm missing anything.

Anyways, this thing runs solid- pulls well in almost all situations. The issue I'm running into is during >75% throttle sustained pulls it will always stumble after a few seconds of holding 10-12 lbs boost. Typically this is during a pull from 70 - 100, I'll be cruising at 3k, and as I near 4k and I'm holding boost above 10lbs it will break up and I have to quick get out of the throttle and it's fine.

I'm thinking likely a fuel issue? I don't have any issue running through the RPM range when I'm banging gears but those long sustained pulls in boost don't ever hold on.
 
Drunk_Babies said:
No, would probably tell me all I need to know though wouldn't it :)
Click to expand...

+1 on the AFR gauge.

Later Turbo cars use 337cc injectors (the green 804's) and although they usually have a bit of headroom from my experience when turning up the boost, I'd make sure your AFR looks good throughout the rev range with your injectors.
Could be that earlier Turbo cars use other injectors with less flow, but I'm not sure on that.

Only way to know for sure is a gauge.

Also, do you run custom chips or stock map?
 
Fa182 said:
+1 on the AFR gauge.

Later Turbo cars use 337cc injectors (the green 804's) and although they usually have a bit of headroom from my experience when turning up the boost, I'd make sure your AFR looks good throughout the rev range with your injectors.
Could be that earlier Turbo cars use other injectors with less flow, but I'm not sure on that.

Only way to know for sure is a gauge.

Also, do you run custom chips or stock map?
Click to expand...

Stock fuel & ignition maps.

I think I've got plenty of information to run with here- I'm going to first try dropping the boost down to 8-10PSI max and see if I can get some long heavy pulls in. I took a peek at my fuel pumps, the inline pump looks incredibly old so maybe it's just not flowing well enough. I have both on order so I'll swap those out when they arrive and update this thread with what I find.

Thanks for the help so far guys, wish me luck!
 
Update:

It appears my MBC was cranked down too far- started from scratch and worked my way back up to 10psi.
This WG has a 5lb spring, and I was attempting to run 13-15psi.(Or who really knows what I had it cranked down to) Doing some reading and I found this:

"If You try to Boost More than Double the PSI of your Wastegate Spring, the Boost PSI will Fall off to a Lower PSI, The Reason Why is Because the Higher Pressure of the Engine At Higher RPM will force Open the Wastegate Valve, if the Base Spring PSI is too low. This is the Reason Why you Cannot use a Base Pressure 8 PSI Spring Cannot be used with a Boost Controller to run over 16 psi at Redline."

So if I ever want to try 15psi again it sounds like I may need a 7-8lb spring.
 
the best thing i did for my 240 was a EBC so much better, more precise and spools much faster than a MBC and only was like 180 euro wiring was easy too
 
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