I was wondering what fuel pressure I should run on my aggressively street ported s4 t2 running on 9 psi? I have an aftermarket fuel pressure regulator and my fuel rails are modded to use it. also have 3" exhaust and fmic piping and a 255lph walbro but with stock 550's

 

43 psi sounds good.

 

It's not such a good idea to try to keep your engine from blowing by simply raising the fuel pressure. What you really need are some larger fuel injectors and an aftermarket fuel computer.

With the Walbro, I don't think that you will be able to raise the pressure enough for your engine. However, I am guessing that you will be able to run about 50-55psi before there is a flow loss. In theory, 50psi should support about 300hp on the stock injectors, but there are a lot of factors like the quality of the electrical connection to the fuel pump, condition of the fuel injectors, engine tune, turbo efficiency, fuel system flow losses, etc. I think that you are going to fry your engine, but good luck.

 

and you still are running pig rich out of boost.

popping an engine is mandatory for the learning process.

 

Worst part of the whole equation is that full 3" exhaust...best way to blow a motor. With the ported motor and S4 wastegate you will be way over 9psi in the 5-6,000rpm range.

Want to run stock injectors? Run stock boost and stock exhaust. Otherwise you need to do something else if you want the motor to last.

 

Dang, that means I haven't learned anything during the 24 years that I have owned RX-7s.

 

lucky! i went through a few learning the tuning process on turbo rotaries. but that was also before there was bible sized threads about what to do and not to do.

most people now want you to hold their hand through the whole process for nothing but a few kind words. dang, i'm sounding bitter... probably because i've typed it all out god knows how many times and the info is still out there.


#1, fuel pressure is a bandaid for properly sized injectors. moving up much further requires a way to tune fuel.

of course i've seen these threads more than i care to remember, upgrading everything that shouldn't be upgraded before upgrading the things that should be, like fuel system and engine management. yes, they are the most costly parts to accumulate, they are also the most important.

 

It never boosts over nine lbs in any gear even at high rpm wot. Its closer to seven unless I'm at 6500 wot. Injectors and ecu are next and I know that's important. My friends car has the same setup on 10lbs and he was running like 60psi but that seems wacko to me. So 43?

 

Or higher?

 

Without a wideband you're only guessing, so guess away. We can't tell you what the best fuel pressure will be.

 

True, just thought somebody had the same mods and a wideband too. nvm