dburt86

iTrader: (2)

So forcefed mentioned i could gain some head room in my nearly maxed 80lb'ers if i increase my base fuel pressure.

This is always what i thought also, but when i mentioned it to a friend much smarter then me, he took a look at the flow chart for the walbro 485 and thinks that increasing the pressure would actually work against me.

Flow chart
http://www.dynosty.com/2012/04/new-e...485-fuel-pump/

He goes on to say that because we suspect i dont have enough fuel pump, rather then not enough injector, that this would happen.

So looking at the chart, it seems he is right, but i wanted to see if we are over looking something simple.

Thanks

93camaro_zzz

iTrader: (13)

Well yeah, first thing you would want to do is to see if you have enough pump to support the flow for the current base pressure. Do you have a 1:1 rise FPR on the car right now? What is your base pressure set at as of right now? You should be able to go quite a bit further on those injectors. I have the exact same injectors in my car, and I made 931whp through a really high hp loss drivetrain. 87% IDC, 58psi base, 1:1 rise fpr. And I don't have meth. This was on VP110, which is nearly the same stoich as pump gas.

dburt86

iTrader: (2)

1 to 1 regulator, 50psi base

this was a mustang dyno, not sure on what you use. The dyno owner says that it reads 12-15% lower then a dynojet, so even at 10% thats aboout 800 to the wheel.

93camaro_zzz

iTrader: (13)

Potato Potaughto. My car has much more drivetrain loss than yours. So it would about even out. Do you have a way to monitor your fuel pressure? I just put a $5 oreillys gauge on the side of my FPR. Works fine. Wouldn't be surprised if your pump was falling off as of right now. I run triple 255's in my car, but after the 1:1 rise, my car is at 80psi fuel pressure. lol

dburt86

iTrader: (2)

I did just get a transducer so I can log it, but I know I don't have enough pump and won't be surprised to see the pressure drop. But I will be logging that soon.

I guess my question is even if I turn my pressure up, it won't help until I get enough pump to support my fuel needs, correct?

svslow

Raising the pressure will increase the injector flow rate but you will ultimately be limited by the decreased output of the fuel pump at the elevated pressure. You just need more pump.

JoeNova

Didn't Denmah make almost 900whp in Mark's Camaro with a 450lph and 80s? Maybe he will chime in.

svslow

I do think it was on 80's but I am not positive on the pump.

svslow

What kind of fuel lines are you running?

JoeNova

It was a walbro 400/450. He used Mark's camaro as the reason for using one in his truck.

dburt86

iTrader: (2)

The fuel lines are stock Bmw lines, not too sure on the size but you can imagine they aren't too big.

I'm going to pull the pump out and make sure it's not bottomed out or something in the tank. Maybe put it on a relay and get it some more power too.

svslow

Stock lines could be an issue if they have a ton of bends in them. If you are using all factory wiring to the pump that could also cause some problems. Power a relay straight off the battery (fused) to the pump and use the existing wiring to turn the relay on.

Forcefed86

iTrader: (4)

Just throw another 450LPH pump in there while you've got it out and run it on a hobbs switch. It's cheap and you know it will have enough fuel to really lean on the small injectors.

Something like this...




Or if you don't have room...

Leave your 450 intank and use it to feed a surge tank with 2 bosch 044 (or AEM 380) pumps off the surge in parallel.

MIGHTYMOUSE

iTrader: (59)

increase base pressure until it does not hold, back off a little and that is the high spot on the efficiency island.