Lean spike at beginning followed by very rich....
08-26-2011, 07:50 PM
#1
Lean spike at beginning followed by very rich.... I got my trans am tuned on the bottle and on the initial hit we experienced a lean spike but as the run progressed it became very rich low 10's. When using the recommended #38 pill for fuel a/f was in the 9's by the end of the pull. We backed it down to a #35 then down to #33. The tuner stated that the lean spike was too high (mid 14's i believe) to lower the fuel pill again but still did not like how rich it ran on the bottle (low 10's). N/a tuned was spot on. Im not too worried about the spike because it only occures for a very short period of time but what are you thoughts on why it runs so fat up top? Thanks
08-26-2011, 11:52 PM
#4
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my wet kit had a lean spike on activation as well. usually only on the first hit in a short amount of time. 58 psi fuel < 1050 psi nitrous. nitrous wins the race. Both the nitrous and fuel lines are empty after the solenoid and obviously nitrous is faster. only thing you can really do is buy a controller that can open the solenoids at different times, like opening the fuel solenoid 1/10th of a second before nitrous.
as far as running fat up top, how is your n/a tune? is it nice and flat wide open? whats happening to your bottle pressure throughout the pull? if its falling off your gonna go rich.
as far as running fat up top, how is your n/a tune? is it nice and flat wide open? whats happening to your bottle pressure throughout the pull? if its falling off your gonna go rich.
Last edited by got-a-ls1; 08-26-2011 at 11:57 PM.
08-27-2011, 11:27 AM
#5
The n/a tune is completely flat. If you look at the graph and look at the blue line. It is flat all the way across. Bottle pressure doesnt seem to drop that much. normally ran at 950 psi. I not TOO worried about the lean spike. More interested in figureing out how to make the top end more stable.
08-28-2011, 03:10 PM
#7
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Is it a stock fuel pump? Are you pulling Fuel off the Rail?
It looks like a lean spike from you losing fuel pressure on the hit...then the pump catches back up and fills the rail again. I have had this happen on many vehicles which were at the limit of the fuel system ability to put out the volume to compete with the hit of a wet kit that is pulling fuel off the rail.
If you have an aftermarket pump when was the last time you changed your fuel filter.....have had this problem recently on 3 cars in the south texas area. Dirty Fuel filters causing erratic/loss of fuel pressure. This was on 2 cars with 10an inline filters and Eliminator pumps and an 03 Cobra with a Triple pump system with an 8an inline filter....all plugged bad
It looks like a lean spike from you losing fuel pressure on the hit...then the pump catches back up and fills the rail again. I have had this happen on many vehicles which were at the limit of the fuel system ability to put out the volume to compete with the hit of a wet kit that is pulling fuel off the rail.
If you have an aftermarket pump when was the last time you changed your fuel filter.....have had this problem recently on 3 cars in the south texas area. Dirty Fuel filters causing erratic/loss of fuel pressure. This was on 2 cars with 10an inline filters and Eliminator pumps and an 03 Cobra with a Triple pump system with an 8an inline filter....all plugged bad
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09-01-2011, 08:03 AM
#10
62 n20
33 fuel
I do not know the flowing fuel pressure during a pull. I do have a brand new racetronix fuel pump kit w/hot wire and fairly new fuel filter. Most say the lean spike is not a concern but at which point does the spike become a concern? Numbers? Could I go another size down on the fuel and go from there? I was thinkin bottle pressure drop but Nitrous Outlet says that I should not be having bottle pressure problems with only 150 shot. I was also thinking about removing the inline filter. The filter is fairly new. 3 bottles only but that doesnt really mean anything.
33 fuel
I do not know the flowing fuel pressure during a pull. I do have a brand new racetronix fuel pump kit w/hot wire and fairly new fuel filter. Most say the lean spike is not a concern but at which point does the spike become a concern? Numbers? Could I go another size down on the fuel and go from there? I was thinkin bottle pressure drop but Nitrous Outlet says that I should not be having bottle pressure problems with only 150 shot. I was also thinking about removing the inline filter. The filter is fairly new. 3 bottles only but that doesnt really mean anything.
09-01-2011, 05:31 PM
#12
62 n20
33 fuel
I do not know the flowing fuel pressure during a pull. I do have a brand new racetronix fuel pump kit w/hot wire and fairly new fuel filter. Most say the lean spike is not a concern but at which point does the spike become a concern? Numbers? Could I go another size down on the fuel and go from there? I was thinkin bottle pressure drop but Nitrous Outlet says that I should not be having bottle pressure problems with only 150 shot. I was also thinking about removing the inline filter. The filter is fairly new. 3 bottles only but that doesnt really mean anything.
33 fuel
I do not know the flowing fuel pressure during a pull. I do have a brand new racetronix fuel pump kit w/hot wire and fairly new fuel filter. Most say the lean spike is not a concern but at which point does the spike become a concern? Numbers? Could I go another size down on the fuel and go from there? I was thinkin bottle pressure drop but Nitrous Outlet says that I should not be having bottle pressure problems with only 150 shot. I was also thinking about removing the inline filter. The filter is fairly new. 3 bottles only but that doesnt really mean anything.
Pressure drop in your bottle is of no concern on a single .062 jet.
Lean spikes can be a common problem with a wet sytem. With the size system that you are using should be transparent though. Start by changing your fuel supply off the rails and use a dedicated fuel system. Using a deadheaded sytem helps alot with lean spikes on much larger systems.
09-01-2011, 09:27 PM
#13
I started with a 38 fuel jet because thats what was recommended with the kit. We then moved down to 35 then to 33. The tuner did not feel comfortable moving any lower with the jets because of the lean spike. The lean spike was very quick then leveled out then continued to go further and further rich. How much of a lean spike would be considered dangerous? I guess what im asking is, as long as the spike is very quick, on the initial hit only, is it something to worry about or should i keep lowering the pill till the rich condition levels out to where i need it.
