sybelix

Hi. I'm getting 55-lb/hr injectors. What is the max rear wheel hp, that they are good for (with upgraded fuel pump of course).
I'm planning to get a larger turbo (k27/8) and I have MAP stage 2.
So should I get even bigger injectors, or will I do just fine with those.
I'm planning of using something between 16-18 psi.

OriginalSterm

I didn't think you'd needed a bigger pump for 55# injectors unless you were almost static?

TurboTim

You can make about 360-375 at the wheels safely with those injectors. You will have to bump your fuel pressure up beyond 3 bar though.

TurboTim

Actually you might need a bigger pump if you are trying to make a decent amount of power.The stock pump cannot generate the volume of fuel required to make big power.

OriginalSterm

With a MAP stage II and a K27, we aren't talking power in the 360-375 rwhp range. The 55# injectors should be fine with the stock fuel pump with those upgrades I would think.

But I guess it does depend on fuel pressure since the capacity is lower than the stock 2.5 bar pressure capacity. Anybody with experience with these mods want to chime in?

TurboTim

I doubt you will make power like that with a k27 turbo.

Highlander944

If I understand correctly the fuel pump can deliver a greater volume of fuel at a lower pressure.

Thus, you may wish to consider larger injectors and going back to the 'stock' 2.7 bar fuel pressure regulator. You can then use the 'bigger' hole in the injector at lower pressure to deliver maximum fuel without changing fuel pumps.

Peter.

OriginalSterm

The bigger injectors are usually rated at 3 bar, running lower pressure will not yield the same flow rate. It will be higher than a stock injector at stock pressure, but not as high as the rating.

2.5 bar is probably not too low, but if you go to low you can effect the opening and closing response of the injector and my not function properly or as expected.

Danno

Yeah, I wouldn't go below 2.5-bar, the fuel just dribbles out rather than misting; not good for vaporatization.

"With a MAP stage II and a K27, we aren't talking power in the 360-375 rwhp range. "

You can if you run 20psi. Just requires some dyno-tuning. Here's a K27/8 @ 20psi:


Notice the wide and flat torque-curve, which is representative of GURU upgrades. Also HP is made near redline and is higher than TQ (shows good high-RPM breathing). The previous run was actually 362rwhp, but got really lean in the upper-RPMs with 50-lb/hr injectors. Adding some fuel-pressure killed the mid-range and helped the upper-PRMs somewhat. Since it's right at the limit of the stock pump as well, we're replacing the pump 1st and giving it a little more pressure.

So in your case, no need to replace the pump yet if you're going with 55# injectors. I can get you an updated chip with mappings for 20psi too.

B951S

I have 55# with a 3 bar FPR and the injectors run fine with a T04E/#8 turbo running up to 18psi. They see ~90% duty cycle at red line. You should be fine.

toddk911

Danno beat me but I was going to mention GURU is getting 350rwhp+ with just k27 and chips and stock AFM. So with MAP, it should be in the 365-375rwhp range easy.

OriginalSterm

If he's going to run 16-18 psi as he stated, he won't see those numbers though. He may not need a larger fuel pump either, I'd have to look at the flow curve of the stock pump and I think those injectors are a pretty good fit for his setup.

Danno

"GURU is getting 350rwhp+ with just k27 and chips and stock AFM"

Actually it's an APE-MAF and a massaged head, but close enough. The K27 chip for AFM run at 18-20psi and is good for 290-320rwhp. There's a lot of potential in the K27, I don't think people give it enough credit. The secret isn't in just throwing more and more parts at the car, but tuning your existing configuration optimised to extract the most performance you can from it.

billgot

I have #55's with 360+ at rear wheels you wont need biggerinjectors in fact you might be to rich down low I hope you have a way to control the flow on the injectors.

sybelix

guys, for your help. Could you also help me with this white stuff on the ground..snow..
Ok, it is supposed to melt in a couple of weeks, I hope