suggestion on fuel starvation at track.
10-25-2010, 10:24 AM
#1
Racer
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suggestion on fuel starvation at track.
first off here is a brief discription of whats on my car. 385 w/ q-jet. set up with a/f meter (on street). holley electric black pump, put on to fix fuel starvation issue witch helped. she runs out of gas around 6k. and not sure what else to due. has stock fuel lines but pump rated to 700 horse, witch im at maybe 475. so running out of gas twice it went 13.11 @ 105mph 
. any suggestions?
. any suggestions?
10-25-2010, 10:51 AM
#2
Le Mans Master
Did you remove the fuel sock in the tank? Check the float level in the q jet. I would guess it's a carb problem.... Bowl is not filling up fast enough or at all. You could rig up a fuel pressure gauge and tie it in at the carb inlet, route the gauge up to the cowl area for temporary use and make a pass and see if the pressure drops below 4psi....if it does, it's a pump/line problem. If the pressure stays up, it's a carb problem.
10-25-2010, 11:01 AM
#3
Racer
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replaced sock with delco one, rubber lines ect. float as high as possible. next i was going to make a test port for my fuel pressure gauge, but dam thing only happens at track, street its fine. ajrothm you still using your stock fuel lines?
10-25-2010, 11:05 AM
#4
Burning Brakes
How much fuel do you have in the tank when you are at the track and you experience this issue?
I had an issue in another vehicle when I ran with less than 5 gallons of fuel at the drag strip. Turned out, under full acceleration, the fuel was thrown to the back of the tank and the pickup was just sucking fumes. Solved the problem by fitting a 2 litre surge tank. Electric fuel pump fills the surge tank, whilst fuel for the motor is drawn from the surge tank. Surge tank is tall (about 30cm) and about 10cm in diameter, so accelleration doesn't cause fuel delivery issues anymore.
I had an issue in another vehicle when I ran with less than 5 gallons of fuel at the drag strip. Turned out, under full acceleration, the fuel was thrown to the back of the tank and the pickup was just sucking fumes. Solved the problem by fitting a 2 litre surge tank. Electric fuel pump fills the surge tank, whilst fuel for the motor is drawn from the surge tank. Surge tank is tall (about 30cm) and about 10cm in diameter, so accelleration doesn't cause fuel delivery issues anymore.
10-25-2010, 11:14 AM
#5
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How much fuel do you have in the tank when you are at the track and you experience this issue?
I had an issue in another vehicle when I ran with less than 5 gallons of fuel at the drag strip. Turned out, under full acceleration, the fuel was thrown to the back of the tank and the pickup was just sucking fumes. Solved the problem by fitting a 2 litre surge tank. Electric fuel pump fills the surge tank, whilst fuel for the motor is drawn from the surge tank. Surge tank is tall (about 30cm) and about 10cm in diameter, so accelleration doesn't cause fuel delivery issues anymore.
I had an issue in another vehicle when I ran with less than 5 gallons of fuel at the drag strip. Turned out, under full acceleration, the fuel was thrown to the back of the tank and the pickup was just sucking fumes. Solved the problem by fitting a 2 litre surge tank. Electric fuel pump fills the surge tank, whilst fuel for the motor is drawn from the surge tank. Surge tank is tall (about 30cm) and about 10cm in diameter, so accelleration doesn't cause fuel delivery issues anymore.
10-25-2010, 11:15 AM
#6
Le Mans Master
I'm using the stock 3/8" fuel line, 172gph mechanical pump. I do get a good bit of pressure drop. I haven't tested the pressure drop at the strip but on a chasis dyno pull my pressure dropped from 7psi down to about 4psi. I am sure on a full 1/4 pass it is even less then that but.....my AFR holds around 11.6 through the traps at 123mph so for now, I am letting it ride.
I have some nasty bends and a small -6 90* swivel inlet to my pump so I think that is my restriction. Eventually I will change pumps with a separate inlet plate that is clockable on it's own so I can run -10 line to it...
Also Robb Mc C Performance is making a 1/2" sending unit for the vettes now.....it's $$$ though.
I have some nasty bends and a small -6 90* swivel inlet to my pump so I think that is my restriction. Eventually I will change pumps with a separate inlet plate that is clockable on it's own so I can run -10 line to it...
Also Robb Mc C Performance is making a 1/2" sending unit for the vettes now.....it's $$$ though.
10-25-2010, 01:24 PM
#8
Le Mans Master
$180 though.....damn... You could mod the original sending unit yourself cheaper if you can weld...
I don't really think the 3/8" p/u and lines are my problem though, it's the fittings into the pump inlet that kill me..
10-25-2010, 02:03 PM
#9
Team Owner
what is your fuel pump regulator set at and are you using a bypass return line. Can you mod the needle and seat/
On Holley type carbs you can also go to larger diameter N&S bowl valves. I used to run the holley Alki needle and seats because they flow twice as much as a typical gasoline N&S.
Bigger pumps and lines are not the answer!
On Holley type carbs you can also go to larger diameter N&S bowl valves. I used to run the holley Alki needle and seats because they flow twice as much as a typical gasoline N&S.
Bigger pumps and lines are not the answer!
10-25-2010, 02:51 PM
#10
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my holley electric black pump preset at 7 psi, so no regulator, going to put higher pressure spring in pump, put the regulator back on and that should give enough pressure up to front of vehicle on hard launches-i hope.- got a .149 needle an seat. float at max, q-jet can only hold so much fuel i guess
10-25-2010, 07:15 PM
#11
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what is your fuel pump regulator set at and are you using a bypass return line. Can you mod the needle and seat/
On Holley type carbs you can also go to larger diameter N&S bowl valves. I used to run the holley Alki needle and seats because they flow twice as much as a typical gasoline N&S.
Bigger pumps and lines are not the answer!
On Holley type carbs you can also go to larger diameter N&S bowl valves. I used to run the holley Alki needle and seats because they flow twice as much as a typical gasoline N&S.
Bigger pumps and lines are not the answer!
10-25-2010, 07:46 PM
#12
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10-25-2010, 07:55 PM
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I'm running a 427 (w/a Holley) on road courses with longer straights than just a quarter mile. A quarter mile at WOT is not that big of a deal. As I mentioned earlier, I agree with gkull that the stock fuel line size is not the problem here (unless you pinched it somewhere).
10-25-2010, 08:07 PM
#14
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I'm running a 427 (w/a Holley) on road courses with longer straights than just a quarter mile. A quarter mile at WOT is not that big of a deal. As I mentioned earlier, I agree with gkull that the stock fuel line size is not the problem here (unless you pinched it somewhere).
10-26-2010, 07:58 PM
#15
Le Mans Master
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Stock fuel lines are adequate for what you're doing. I've run 12.66, on drag radials (1.75 60 ft time) with a Qjet, stock fuel lines and pickup in the tank, with a stock type mechanical pump.
10-26-2010, 08:16 PM
#16
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my 60' was 1.70 but my reaction was .384 i was making a sandwich at the line everyone tells me. figured my lines are good, going to mess with my fuel supply and delivery. i know its a 12 sec car at least, once i fix my gremlins
10-26-2010, 10:49 PM
#17
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Did you remove the fuel sock in the tank? Check the float level in the q jet. I would guess it's a carb problem.... Bowl is not filling up fast enough or at all. You could rig up a fuel pressure gauge and tie it in at the carb inlet, route the gauge up to the cowl area for temporary use and make a pass and see if the pressure drops below 4psi....if it does, it's a pump/line problem. If the pressure stays up, it's a carb problem.
