b16ef

My friend is still in high school, so he doesnt have a job to get it tuned. It's an external wastegate, we retarded the timming but it didn't help....I guess we could try to retard it more? We've tried alot.

BAD4DR

Nope. Will only help the situation. Not fix it.

b16ef

ight thanks.....What about the iav? he said he loosened one of the bolts on his when he took the throttle body off, would that have anything to do with it? And also we were wondering since it is an obd0 car would he have to use any check valves on the sensor on the firewall, along with a missing link?

b16ef

Is there anyway to tell if the fuel pump is going bad?

DAintegra90

take the nut off your fuel filter and crank the engine, if fuel comes out, then it should be good

b16ef

Could it be that the fuel pump is jus going bad, so it's not able to push that much pressure when the fmu kicks in?

BAD4DR

The problem is, that with most FMU's (10:1 or 12:1 being the more agressive ones) you don't have any additional fuel pressure until after 3.5-4 lbs of boost. At 5 lbs, with a 12:1, you have 60 psi.

Additional fuel for pressure is solved as:

Square root (New pressure/Old pressure) times Original Specification.

Meaning, it's important to know what size your injectors are, what the turbo is, so you can determine the HP it's trying to push, and then the base pressure, so you can solve for the FMU.

i.e. 440 cc injectors: lb/hr is cc/10.5.
That's 41.9 lbs/hr. @ 80% duty cycle = 33.5 lbs/hr.
You're turbo, so BSFC (Brake specific fuel consumption) should be calculated at .6 lb/hr per hp, that's 55.9 hp per cylinder.
So, you can support 223 hp.

That's assuming you're running at the stock base pressure.

Upping the pressure with a 12:1 FMU will yield nothing below 3.3 lbs of boost, if your base pressure is 40 psi. Afterwards, it builds at a rate of 12 psi fuel pressure for each lb of boost. So, at 7 lbs of boost, it's pushing 84 psi of fuel pressure.

84/40 = 2.1
Square root of 2.1 is 1.45.
1.45 x 223 = 323.

So, a 440 cc injector (measured at a base pressure of 40 psi) will support around 320 hp on a 12:1 FMU and 7 lbs of boost.

Let's assume you're on somewhat closer to stock injectors, since this seems to be a total budget project....

Stock injectors are probably less than 230 cc injectors. (Figured at 120 hp for stock hp levels, so I know that's a safe bet.)

That means, basically, that at 7 lbs of boost, an a 12:1 FMU, they'll support about 175 hp. If the turbo is trying to push air enough to go over that, then it's going to be lean all the time, and you need to upgrade the injectors badly.

Assuming you were to up the base pressure, i.e. to 60 psi, then you would have no additional fuel until after 5 lbs of boost, when the FMU pressure crosses the base fuel pressure.

It's a good idea to calculate the airflow/hp throughout the range, at various boost levels, to make sure you won't be off on early fuel consumption, or late fuel consumption, etc., causing a lean spike somewhere in the range. And, it's fairly necessary from that point, to have a fuel controller, to dial out excess that may occur in the lower ranges, in order to have it properly tuned.

Somehow, I doubt any thought was put into this when the project was done, or you wouldn't be having these problems.

As for checking the fuel pump, a 100 psi fuel pressure gauge would tell you. Also, if you have to go over 100 psi fuel pressure to achieve the amount of fuel needed, you are seriously a lot better off upgrading the injectors.

And, as a just in case, check all of your wiring again. You could possibly have loose connections, or just faulty connections if it was done typical, using butt splices, and crimp connectors. Electronics should always be soldered cleanly.

b16ef

alright.....thanks for your help!