I own a 1988 rx7 turbo, with the S5 turbo i should be boosting 14psi

lately i noticed that when i step on gas the boost shoots up to 14psi were it should be but like a second later the boost drops to 10 or 11 and stays there. Then when i change to 3rd it stays at 11 to 12psi. Usually it would stay at 14 or drop a little to 13 but never this much.

My guess that there is a leak or theres something going on with the wastegate. Any suggestions Please

 

First, don't run 14 psi on the stock turbo. There's no added power above ~12psi, and it will decrease the life of the bearings.

The stock compressor wheel, and turbine to a lesser extent, are not efficient enough to hold much more than ~7psi up to redline. It will typically start to fall after about 5000 rpm. To hold higher pressures throughout the rpm range, a larger compressor wheel can be added (ie BNR hybrids).

 

i put the bigger gsl se injectors on the secondaries, then i bought the AEM wide band, and since i really cant tune i had to raise the boost till my afr was good again at 11.5, if i run lower boost it gets to rich so im sort of stuck =\ also got a spare turbo just in case ;-)

About the no added power over 12 psi, i heard that also had to do with the stock intercooler not being affective past 12psi resulting in the no power gain as well is that true? will a front mount intercooler help.

 

i think the turbo is dieing from trying to push 14psi. remember the thing is designed for less than half of that.

 

yes the top mount is only efficient for only about 10 PSI. the stock turbos can push about 10 only too. any higher, no power band... unless you port the wastegate and add a fuel cut defender. unless you want to have more power, go here: http://www.bnrturbos.com/2ndGen.htm great sourse for someone who may want a stock turbo appearance but bigger turbo. its called hybrids.

also, front mounts will be better in a sort. just make sure you dont get one too big or small, and try the quikest path to avoid any great pressure lost.

 

Why put in the bigger secondaries?
IMHO, seems like a rather stupid course of upgrades. Probably would be smart to get a safc to control the bigger injectors, THEN think about raising the boost. Raising the boost to control A/F ratios seems like it can only end in disaster...

and yes, stock turbo is only good to ~12psi, same with the intercooler. Even with a fmic, the turbo is still going to be a blow dryer above 12.

 

Stock turbo efficiency / specs: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/stock-turbo-wheel-size-818137/

The compressor wheel is very inefficient at high pressures, which means it's greatly heating the air that it is trying to compress. At high rpms, the engine requires more air, which just makes the situation worse. That's why there's a point where increasing boost no longer makes more power. The air temps are being increased so much that it counteracts the gains from pressure increases.

Intercoolers have a set thermal efficiency and pressure loss, so going to a FMIC is just a bandaid. It will allow a little more power to be extracted from the post-turbo air, but it won't help the turbo's efficiency.

 

thnx guys for the help well i put the boost down, havent tried it yet and im going to put the FMIC probably this weekend,since its been laying in my garage for weeks.

Oh and for Kakaroto, of course i have the fuel cut defender i wouldnt be able to be boosting more without it.

putting the FCD plus the injectors is a great way to boost up a bit, expecially when its free =D
i ran a 13.5 on the quarter with it, huge difference from stock lol. i think thats as fast as it could get with all this stock equipment, but i couldnt be anymore proud of my daily car. =)