What is the maximum boost that people are running with a stock turbo and stock fuel system? I heard that the stock injectors/stock fuel pump will start to run out at around 22psi...is this true?

Thanks.

 

Not really. It depends on many factors beyond just boost. The amount of fuel you use is not just dependent upon the boost. It is also dependent upon the airflow you get from your mods (cams, exhaust, header, o2, etc), and your tune. If you have the stock tune, which is very rich, then you are going to overrun the injectors and/or fuel pump much sooner than if you're leaned out heavily on alky or race gas.

Typically, we don't like to go above 22psi without a fuel pump. It's not that the pump can't supply enough fuel (I went low 12s @ 24psi many times before upgrading my pump), but that it is not RELIABLE, which puts you at risk of fuel starvation. The injectors aren't a problem at all - you can pretty much max out the stock turbo on the stock injectors.

 

I see. Do you have a fuel pressure regulator with your upgraded pump?

 

before and after my fuel pump i was hitting 30 psi and holding 25. on race gas though. my pump map is more tuned for saftey because of the heat here

 

My cams and exhaust manifold are stock. I have a a cool air intake, BR lower intercooler pipe, a 3" exhaust and reflashed ecu.

 

We don't use FPRs, no. Just a basic, simple fuel pump upgrade is all you need. You should get an MBC to control boost, too. Set it at 22psi peak in 3rd gear.

 

That's where I'm at right now...thanks for the info.

 

I was under the impression that Evos do indeed come equipped with a fuel pressure regulator....just that it is not an adjustable one.

 

Yes it is on your fuel rail, it regulates fuel rail pressure by controlling how much gas is returned to the fuel tank. Its a small round diaphram valve with a vacuum hose connected to it.

 

Just to add another data point, I'll post my usual BS.

Like War said, the stock injectors are just enough for the stock turbo. With the stock turbo's flow maxed out at 43 lbs/min (no boost signal to the WGA for race gas example), I would see 100-102% IDC at 11:1 on pump gas, and 96-97% on race gas with a Specific Gravity of .70. I know everyone on here follows the internet myth about going over 80% IDC being bad, but I ran injectors like this for years with no negative side effects.

The pump is real close. War's advice of upgrading it for reliability is probably valid. It's such a cheap upgrade, especially if the factory dual voltage circuitry is still active on your car (it's not on mine, had to get a regulator, which adds about 200 bucks). But that being said, the math says the stock pump on stock wiring, even on the "high" voltage output, is only enough to maintain 12.5:1 AFR. And that is exactly what I got. And the math says that rewired (www.vfaq.com) it will support 44 lbs/min with all of the proper variables entered, and indeed I have seen up to 43 with rock solid AFRs (WBO2 matching DSMlink target AFR).

I did eventually upgrade to a 255 just because they're cheap and it makes it easier for me to sleep at night. I also tossed in a set of FIC 950s, which are my new favorite injector for the last few years, because DSMlink let's me roll like that.

As always, do this at your own risk, YMMV, etc.

 

Doesn anyone know how much more fuel the IX pump flows over the VIII pump?