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Old 10-15-2006, 04:29 AM   #1
1st Gen
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Join Date: Oct 2006
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I just put a turbo engine in my 91 Mazda and I'm having some trouble with boost cut off. A buddy recommended this forum as having a lot of good turbo related information so I figured I'd see if I could find something that would help. I already did a "boost cut off" search and I got a bunch of threads ranging from several hundred to several thousand. Whoa!

I'll take a look at the tech threads and see if I can find anything there. If someone can shoot me a link or something, it would sure save me some time. My trouble is that my engine cuts out at 11psi. It should boost to 14 all the way to redline but I never make it under full throttle because of the cutting out.

Thanks
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Old 10-15-2006, 09:02 AM   #2
dibblejr
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Chapter/Region: South East
Location: Dirty South
Vehicle:
05 LGT
PSM

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Need more specifications on your vehicle to help you out.
What type of mazda engine Rotary or OHC. What type of turbo system, OEm or AM.
Lots of more info.
I am sure that a Mazda community can help you out just as much as the Suby community.
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Old 10-15-2006, 08:21 PM   #3
1st Gen
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Default

The engine package is out of a 1988 323 GTX
DOHC BPT package
BP 26 ECU
Stock SMIC with all the piping
IHI VJ 20 TURBO
BP 26 VAF
BP 26 wiring harness that I had to lengthen by three feet to fit may left hand drive car.
The exhaust is 2.5" from the turbo dump back.. That is not stock.


It runs real good for the most part accept for the limit at 11 pounds of boost. I usually can't reach the cut off in lower gears but 3, 4 and 5th all get shut down on hard acceleration. I've been told that it could be an improper air fuel ratio, or it could be an air leak between turbo and intake manifold.

I wonder if it could be the waste gate opening to soon. I'm not sure it that's possible really but it would explain some things. I have asked at some of the Mazda forums, in fact it was a guy at one of those forums that directed me here because there was such a wealth of turbo knowledge.

Would a wide band o2 gauge help me with this problem?
Could it be a leak in the intake piping?
Could it be a sticking waste gate actuator?
Anything else I'm missing?
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Old 10-15-2006, 08:44 PM   #4
dibblejr
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Location: Dirty South
Vehicle:
05 LGT
PSM

Default

I was hoping you said rotary because I know them inside and out, TT, St, SC, NA, but I know a little about the car your motor came out of.

Did you also get the ecu with the motor?
When you talk cut off your are talking limiter of fuel cut, which one?
What type of boost controller are you running? Stock solenoid, MBC, EBC?
Do you have a laptop?
With the install did you happen to also plug in the ecu plug to read codes?

Answer those for a start

Jay-R
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Old 10-15-2006, 09:02 PM   #5
1st Gen
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Quote:
Originally Posted by dibblejr View Post
I was hoping you said rotary because I know them inside and out, TT, St, SC, NA, but I know a little about the car your motor came out of.

Did you also get the ecu with the motor?
When you talk cut off your are talking limiter of fuel cut, which one?
What type of boost controller are you running? Stock solenoid, MBC, EBC?
Do you have a laptop?
With the install did you happen to also plug in the ecu plug to read codes?

Answer those for a start

Jay-R
Yes, I’m using the ecu that came with this motor
If I understand the information that I’ve read so far, boost cut causes the ecu to cut power to the injectors thus causing fuel cut. The only thing that makes me think it ‘s boost cut is that 11psi ceiling that I hit when ever I step on it.
I don’t have any type of aftermarket controller.
I don’t have a lap top and I didn’t read any of the codes in the ecu.
I figured since I was emulating the original setup, there shouldn’t be a problem with codes or maps.
The engine itself has around 60K on it but it sat outside for several months in Japan while shipping was being arranged.

Thanks for spending time on this. I know those minutes don’t come back.
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Old 10-16-2006, 11:11 AM   #6
dibblejr
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Chapter/Region: South East
Location: Dirty South
Vehicle:
05 LGT
PSM

Default

You must have a boost control solenoid controlling the boost. If you do try to but an MBC on to adjust the peak boost yourself.
I do not know what the stock boost for that engine is, if you know this it would help.
Not a problem on the minutes, there is so much that we can do online.

Quote:
Originally Posted by 1st Gen View Post
Yes, I’m using the ecu that came with this motor
If I understand the information that I’ve read so far, boost cut causes the ecu to cut power to the injectors thus causing fuel cut. The only thing that makes me think it ‘s boost cut is that 11psi ceiling that I hit when ever I step on it.
I don’t have any type of aftermarket controller.
I don’t have a lap top and I didn’t read any of the codes in the ecu.
I figured since I was emulating the original setup, there shouldn’t be a problem with codes or maps.
The engine itself has around 60K on it but it sat outside for several months in Japan while shipping was being arranged.

Thanks for spending time on this. I know those minutes don’t come back.
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Old 10-16-2006, 04:35 PM   #7
1st Gen
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14 psi I believe.
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Old 10-16-2006, 05:17 PM   #8
dibblejr
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Member#: 94070
Join Date: Aug 2005
Chapter/Region: South East
Location: Dirty South
Vehicle:
05 LGT
PSM

Default

You probably have a boost leak. You need to check all your hoses. Also like I mentioned you can get an MBC foe $25-$75 depending on what one. Try installing that and see if you can increase.
Im not sure about your car, but also check your floor mat to make sure it is not interfering with the accelerator pedal. ( you'd be surprised how often this happens)

Quote:
Originally Posted by 1st Gen View Post
14 psi I believe.
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Old 10-16-2006, 08:17 PM   #9
1st Gen
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Join Date: Oct 2006
Default

Is there a test for this type of thing? I was thinking that I might actually be able to pressurize the system from the CAI clear to the throttle body and use a tire pressure gauge to see if it holds. I could use a piece of radiator hose with a clamp to keep it on the filter side of the vaf and have a plug in the other side and have it help on with a clamp. The plug would have a tire stem in it for adding and checking pressure.
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