went to e town last night for test and tune

last november i went 11.87 @114 w/ a 1.65 60ft
full weight car

this time i went 12.26 @110 w/ a 1.67 60 ft

since last year i have put pro stars all around skinnys up front 28x10.5 et drags in back, some tuning of the car on the dyno before it broke down, and a more loose converter (3600). on the way there i was having troble with the fuel pressure again it was fluctuating like crazy in traffic, and stalling out while in traffic. but when traffic cleared up and i was at highway speed it was better, i got to etown let it sit for 2 hours and it was fine, my friend said that it seems like the fuel pump is getting hot and dying. while making a pass i noticed my fuel pressure drop from 55psi to as low as 25 so after that i was done for the night and drove home and it was fine on ride home (no traffic at night) could it be my fuel pump (i dident run too low on gas on the way there) i was about a little less then 1/2 tank when i was having this problem.
sorry for the long post

thanks

 

If your not getting the right fuel pressure, your AF ratio will be messed up. Check for a constant V supply to the pump. If its gettin sufficient V, and is grounded alright, replace the pump and go from there.

 

i tested that last week i was getting 12.49 volts with the car running

 

The car's charge float voltage should be 13.5 volts or greater. Therefore, you're losing 1 volt to the pump.

WD

 

what tire did you have on there before the 28s? If they were stock size or close to it what gear did you change too to compensate for the bigger tire? What rpm did you cross thefinish line at?

 

I would start with the fuel filter and make sure it is not clogged up. You should not be dropping to 25 psi of fuel pressure.

 

fuel filter is brand new,

im not sure what rpm i was trapping
before the et drags on prostars i was running 275 40 17 zr1's gears are the same (3:91)

 

well there is a huge problem. You lost a ton of gear going from a 25.5" tire to a 28" + top end growth tire. I bet your final drive ratio is at or below stock.

edit..ran some calculations. YOur final drive ration is just below a stock setup consisting of 25.66" tires and a 3.42 gear. Its like your running a 3.37 gear with your current tire/gear combination after you account for tire growth on top end.

 

so that may be a problem in itself, what tire size should i be running, i did not think it would make so much of a difference? i originally had plans for a 200 shot but that has changed.

 

This is true, but his 60' tinme was only .02 slower this time, and his trap speed was down ~4 MPH. This coupled with the fuel pressure problems tell me that there is some serious horsepower missing here that may not show itself until the car is really demanding fuel(after the first 60' for instance). Fix the fuel delivery problem and go back to the track. I would not worry about tires and gears until you get this fixed!

 

yea im going to be fixing that first before i change anything
is the racetronix fuel system good enough for me, do i need bigger injectors as well?

 

More than likely your fuel pump is dying. In no way is the pressure ever supposed to decrease as you accelerate.

 

The Racetronix pump is a great choice.