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Q&A regarding engines, turbos, and intercoolers and power upgrades
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Maximum boost in ST185 All Trac (not Carlos Sainz)

Mon Dec 18, 2017 8:25 pm

Good afternoon.
I have been told that the maximum efficient boost in the ST185 All trac (not Carlos Sainz) is 0.8 bar (11.6 PSI)

Once this figure is raised the ECU does not manage well more boost since it does not have good maps of Fuel and Spark

Is this correct? Is there someone who has higher boost with the stock ECU of an all trac?

Is there a trick or solution (without mounting other ecus) that allows you to increase the boost a little more efficiently?

I would like to get to 1 / 1.1 BAR (14.5 / 15.9 PSI)

Any video of an all trac running at 0.8 bar?
Any test in bank with this Boost?

You can think of some other way to increase the car's power without changing the ECU.

Air filter
Anything else?

I apologize for my English. I use google translate

Thank you very much
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Re: Maximum boost in ST185 All Trac (not Carlos Sainz)

Wed Dec 27, 2017 6:05 pm


Sadly my GT4 system knowledge is in need of a refresher reading, so if someone knows otherwise, you are correct.
The JDM ECU has a higher fuel cut of 14 psi, the RC is higher, and the 205 is higher still.

Without disabling the fuel cut using a fuel cut defender, u are stuck to a max of the ECU factory limit. Not sure if someone around here has tried a fuel cut defender. I think most just get a JDM ECU. After that they go for a Gen 3 efi swap or aftermarket ECU and a larger turbo to support it.

On my original JDM ECU, I ran about 12 psi (fuel cut 14) with the the following mods:
TTE metal head gasket and arp studs
2.5" koracing downpipe
ARC highflow tmic
Manual boost controller
Stock turbo.

I'm now running Gen 3 efi with an MR2 ECU. The fuel cut is about 20 I think but I still only run 12 psi.

The best mods for power without the ECU swap will be straight intake, better intercooler and an exhaust. But honestly, going for the Gen 3 swap upgrade is the best thing you can do since it ditches the restrictive AFM

Re: Maximum boost in ST185 All Trac (not Carlos Sainz)

Fri Dec 29, 2017 2:30 am

I believe fuel cut for the standard 185 is 14.7psi, the RC/CS/GrpA is 17, and the 205 is either 17 or 20. A downpipe will let the engine breathe much better. For anything beyond that, check out the "MR2 power primer".

Re: Maximum boost in ST185 All Trac (not Carlos Sainz)

Sun Feb 04, 2018 7:51 pm

I'm not sure what fuel cut is on the alltracs but on mine instead of the hks fuel cut defender I have the Greddy version of it and with that I also have a fmic and 3in downpipe and exhaust and 20b turbo. I was running 20psi pretty good until the turbo went. hope that helps!
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