So, I'm trying to get my single turbo project car (I admit, bought not built) running properly, and I think the main reason its not running right is that there's too much fuel pressure, causing a massive amount of fuel to be injected and consequently flooding the engine, dousing the plugs, causing a rev wall at 4,000 rpms, and causing a huge amount of black smoke.

I suspect the SARD FPR is the culprit; possibly jammed with old fuel. But to fix it, I'm going to have to get the fuel pressure and probably the computer settings retuned.

In order to at least get the car moving, what ball park fuel pressure should I aim to at least make it driveable?

The car has a TD06-25, relatively small V-mount, about a 3" exhaust with resonated straight pipe, a Power FC, and SARD fuel pump, and is supposed to make about 350 flywheel HP at 0.8 Bar (about 12 PSI).

 

depending on injector sizes, but 43.5psi should be your base

 

So only about seven or eight PSI higher than stock?

Injectors are stock.

 

About 3bar is usual, but its a tuned car, could be anything.

 

i would worry about what afr im at not what pressure.

 

Eh, if I get the fuel pressure back where it's supposed to be, the AFRs should be OK.

Right now I just want it to run properly and not blow through 10 gallons of gas in less than an hour of idling.

 

Got an AFR guage? If you've got one then you can tweak the fuel pressure until it runs good enough to get to a tuner.

 

"What it is supposed to be" is whatever it was tuned for. I tune everything to 43psi base pressure. Some other people don't, depending on if they are running out of fuel pump or fuel injector.

This is stock pressure for an FC, not "seven or eight PSI higher".

Aftermarket regulators are almost universally bad for failing at the diaphragm and blowing fuel through the vacuum hose. I'd check that first.

 

^ yeah good advice, check the diaphragm. What is the fuel pressure doing ATM? Might be something else - timing? weak spark? crappy earth?

 

I know. I can only expect to get it to a ballpark.

The stock FD pressure spec is 36-38 PSI, IIRC.

I don't have a fuel gauge yet (well, I do, but it's in the states).

If it runs fine with the SARD FPR bypassed I might just get a temp plate and drive it to the tuner.

I hadn't considered that it might be shooting fuel into the throttle body... I'll take a look at that.

 

Timing on the FD is done with the computer and can't be adjusted....well, except that this is a Power FC. But I don't have a commander.

Sparks WERE weak but seem to be OK now that I have new plugs and wires.

 

That's nuts, stock FD base pressure is only 37psi (2.5 bar)? I wonder why Mazda did that.

 

 

I think it comes down entirely to your components. OEM injectors are spitting fuel compared to anything modern.

Misty. You want MISTY, atomized fuel. If your pump(s) and regulator can handle it, with a new set of Injector Dynamics Injectors, you could probably run 55-60psi base and if boosting up to 25psi, your fuel pump would have to be able to flow that required fuel flow at 80-85psi.

 

Yeah im running 4 bar base.

 

the FSM lists 35ish psi fuel pressure, but that is at idle with about 7psi vacuum onthe regulator. engine off, it would be closer to 43psi

 

No, the FSM lists 36-38 with the engine off.

 

most base maps will be tuned to 43psi

if youre tuning from scratch, you could run a higher pressure, so long as your pump doesn't loose flow from the extra pressure at high rpm/load. So if you have a lot of fuel pump capacity, you could run 60psi, get bunch more flow out of your injectors, and have better spray pattern.

I'll be running a 50psi base to keep all things simple.

 

I found that the regulator is giving me 45 psi, but it won't hold vacuum, so I will probably just buy a new one...

 

You should use a 1:1 rising rate regulator and set the base fuel pressure at 43.5 psi. This means for every psi of boost it will add 1 psi fuel pressure. The Sard regulators I've seen were not rising rate. I recommend Aeromotive or Fuel Lab.

 

If the FPR has a vacuum hose, it's rising rate, no?

 

no.

the fuel pressure will drop from 43 to about 28 under 15 inchs of vacuum but not all FPR increase pressure with boost.

 

15inHg of vacuum and 43psi base pressure would be 35.5 psi. 1inHg is .49 psi.

 

oh math math math