fuel pressure

[jonk00000]

My car has not been keeping a steady fuel pressure. on my afpr, I'll set it on 40 psi, drive for a while then check it, and it will have dropped 5 psi or maybe went up 5 psi.

Another problem is at wot, around 5500 my car will cut out almost like fuel cut but with 680's 255hp on the 14b i doubt i should be hitting fuel cut.

I am running s-afc 2 / maft combo any tunning suggestions would help.


thanks a lot guys
jon

 

[flinguist]

Could be the fuel pump o-ring leaking.

 

[sweet97]

Fuel cut has nothing to do with the amount of fuel but the amount of air the ECU "sees" so you have a tuning issue. I just use the MAFT, however I would set the maft for the 650-680's and get the trims close and use the afc for the tuning. That size injector is tough for the maft and safc to compensate for without excessive timing which may produce knock so be aware. mark

 

[jonk00000]

i have my maft set at 680's and my safc at low fuel trim around +5% across the board and around -5% across the high fuel trim board. Am i aiming in the toward the right direction or no?? Also i noticed my fuel pressure guage was at 50 psi after sitting in the driveway for a while then startting it.

thanks again for the feedback

 

[oldman]

Another problem is at wot, around 5500 my car will cut out almost like fuel cut but with 680's 255hp on the 14b i doubt i should be hitting fuel cut.

Like already stated above, fuel cut has little to do fuel supply, more to do with air count. I suspect either you have issues with the MAFT or you have boost leak, I would check both.

BTW What brand afpr is this?

 

[Talesin]

I'm hoping that you have it set to 40 with the vac line off... stock 1G fuel pressure is 36-38 without vac, which drops to 26-28 with vac.

And yeah, check your fuel pump o-ring. The 'waver' in pressure could be attributed to an air/vapor bubble in the line, working its way into the gauge/sender. I had the same thing happen... normally keep mine at 30 (vac on), but had it drop to 20 without warning. Readjusted it, and two minutes later it shot to 40 with vac. I can only assume that the bubble was there, then the higher fuel pressure cleared it through the fuel return. Remember... air compresses, whereas liquids do not.

 

[jonk00000]

This is my afpr: http://www.extremepsi.com/store/customer/product.php?productid=16653&cat=310&page=1

I will be working on my car all day so i will keep this post updated.

I was under the assumption that "fuel cut" was when the system wasn't getting enough fuel. thanks for clearing that up for me

 

[oldman]

I was under the assumption that "fuel cut" was when the system wasn't getting enough fuel. thanks for clearing that up for me

Fuel cut happens when ECU stops the firing of the injectors because it sees more air then the limit pre-programed into the ECU as a safety precaution against runaway boost. Some of most common causes of fuel cut are boost leaks, boost creep and defective maf.

 

[jonk00000]

Fuel cut happens when ECU stops the firing of the injectors because it sees more air then the limit pre-programed into the ECU as a safety precaution against runaway boost. Some of most common causes of fuel cut are boost leaks, boost creep and defective maf.

thanks alot for the info .

i did some adjustments on my hi throttle and the car is runnin great . i have it set at 10 psi b/c i heard its easier to start tuning at a low psi. but when i try and monitor my fuel trims on my pocketlogger, they're all at 100% except fto2 which bounces around. I know they are sappost* to be around 100 maybe a little more but ive been adjusting my translator as well as my safc and no change on the logger like all three are stuck at 100%
any ideas??

 

[jonk00000]

Also another idea I had; if I was running a little lean, can i turn the boost up to compensate/ even out the fuel trims. Like I said, I am currently tunning at 10 psi, I want to bring it up to 18 psi.