I've got a 1987 RX7 Turbo 2, and I was wondering how much, if at all, you could crank up the boost on one of those. I know that there is a boost cut, yet I don't really know 100% why. If anyone could help me out, or give me a link to a website that has all this information, I'd appreciate it. Thanks.

 

Fuel cut happens at around 7.5-8.5 psi depending on which series you have. It cuts fuel to the 2nd rotor so you dont have the chance to overboost. To overcome this you need a FCD (fuel cut defender) which tricks the ECU into thinking that you are not over boosting the stock preset limit. You could be running 15 psi but your stock boost gauge would not read so. If you get to around 10+psi you will probably want to upgrade your fuel pump or at least rewire the stock fuel pump.

 

the problem though, as you raise past the 7.5 mark, the ecu still only sees the 7.2 or what ever and at 15 psi you will only be putting 7.2 psi mapped fuel so BE CAREFULL!!!!

 

In my opinion you can boost up to 12psi on a stock turbo safely. Any higher and you run down the effiancy of the turbo. The problem is controlling the boost and also how much fuel your getting at that psi. Because of our small wastegates the turbos tend to boost all the way to 15psi with open exausts and this is simply too high.
The fuel problem aint too bad as a good piggy back like a S-AFC can give you proper control. But the boost creep is a major pain in the ***. the only way to cure it is it to have a big enough wastegate, then once you can flow enough boost through the WG you can get some kind of boost controller to get it steady.
This for the most part works but it takes some work, intelligence and research.

 

http://fc3spro.com/TECH/FM2W/power.htm


-Ted