Walbro pump

[JJ1224]

Hey guys,

Is the walbro 255LPH too over powering? I heard that some guys couldn't even set their FPR below 50psi because of the pump. And if I was to get a low pressure 190LPH, would I need a FPR?

 

[evil_eagle]

If it's on a 1gen you will be fine with the 255 low pressure pump, if you get the high pressure pump you will need to get a AFPR to get the fuel curve back to linear. 2g yes you need a AFPR with the 255, so 190 would be the way to go on 2g's.
-Jake

 

[DSMTommy]

What pressure settings should a 2g be based at? I just installed my 255 today and wanted to do the AFPR tommorow... Just wondering where to start withe the pressure. It has a Gauge built into it..

 

[larryd]

From a post I asked a long time ago and reply by JW

"Stock base fuel pressure:
1G - 36-37psi
2G - 42-43psi

Should be done at atmospheric pressure (without hose). You will want to put and pull the hose a few times just to be sure the pressure is set correctly.

You can set your fuel pressure to your liking because it's all up to the tuning. Turning up the base fuel pressure will make the injectors *act* bigger. Most injectors are rated at 43psi. 1G stock injectors are actually acting like a 410cc instead of 450s because of the lower fuel pressure."

 

[DSMJim]

so a good base fuel pressure would be 45 for a car with a 255 and afpr then? When you mention setting, im assuming you mean 45 as WOT pressure when the vaccume line is off or at WOT. The base with the vacume line on would be 8-10psi lower then. (34 with line on, 42-43 with line off which is WOT)

Just want to confirm that so I set mine properly. I never checked mine unfortunately before I took my pump out.

 

[pneumo]

Yeah, you have the right idea. But to put a fine point on it, WOT on a turbo car gives higher fuel pressure than atmospheric because WOT on a turbo makes boost. Atmospheric pressure is reached when the boost gage reads "0". With boost the fuel pressure rises one psi for each psi of boost. So if your gage reads 45 with the line off, it should go to 55 at ten psi boost, and 65 at 20 psi, and so on. So, yes, set it at 45 with the line off, it should drop 8 -10 psi with the line on.

 

[larryd]

Regardless of what fuel pump you are running or injectors you are running your base fuel pressure should be stated as I said above.

"Stock base fuel pressure:
1G - 36-37psi
2G - 42-43psi

This is at idle with the hose on the FPR off.

 

[DSMJim]

Originally posted by pneumo
Yeah, you have the right idea. But to put a fine point on it, WOT on a turbo car gives higher fuel pressure than atmospheric because WOT on a turbo makes boost. Atmospheric pressure is reached when the boost gage reads "0". With boost the fuel pressure rises one psi for each psi of boost. So if your gage reads 45 with the line off, it should go to 55 at ten psi boost, and 65 at 20 psi, and so on. So, yes, set it at 45 with the line off, it should drop 8 -10 psi with the line on.

Yeah, I realize that but thanks for the reference. I was refering to when the line was removed or at atmospheric pressure.

Has anybody set base higher by a few psi to acheive the larger injector symptoms along with acctually using larger injectors like 550cc or 660cc? Im asking because Im putting in my safc, rc 550cc and sard afpr and walbro 255 today and wanna set it however it works best for people in the past.

 

[pneumo]

I've run 55psi base pressure with 550 injectors. I did it because I was getting 9 degrees of timing at zero knock. The ECU was pulling timing based on airflow, which was huge in my 1G MAF. It wasn't the best fix, but I needed a quick fix at the track. I was able to lean out the AFC by a few % with out changing the A/F ratio, which means the ECU saw lower aircounts. Later I hacked the MAF more to reduce aircounts and returned to more sane fuel pressures. Then I put 660 injectors on my wishlist.
I don't reccomend higher pressure as a fix for too small injectors, but it can be used to tune if you know what to look for.