Help , fuel pressure drop undeer load during NITROUS
07-09-2016, 10:12 PM
#1
Help , fuel pressure drop undeer load during NITROUS Hey guys wanted to get some opinions on where to look next,
Before the problem here is some info
2002 trans am
Lsx motor
Nitrous outletstinger pate kit
Holley dominator setup
walboro lph 450 running on e85 in tank
90# inj
-8 feed line running to aeromotive regulator
return line
The fuel pump is directly wired to the Holley dominator harness and grounded to the chassis
now the problem:
Ive been trying to fine tune the nitrous kit on this thing but im having some issues that are not allowing me to really start.
What ive noticed is fuel pressure drops low under load during a Nitrous pass.
I though my accessories and stock alternator were the issue since voltage and psi were consistently dropping at the same time in my logs so i had my alternator amped up to 200 and went out and tested again.
On the new logs :
During a motor pass, voltage stayed 13.3 average with 2 dips to 12.0
fuel psi steadily went down to 51psi from 55 and then came right up to 55 as i let out.
During a Nitrous pass, voltage steadily went down to 12.0 fuel pressure during this went down to 36psi as rpms increased, then shot up to 55 as i let out.
Before the alternator amp up i saw psi drop down to 45 but not as low as today.
Anyways any help on where to look next or any tests i can do to try to get to the bottom of this thing so i can start enjoying it would be GREATLY appreciated. thanks guys!
Before the problem here is some info
2002 trans am
Lsx motor
Nitrous outletstinger pate kit
Holley dominator setup
walboro lph 450 running on e85 in tank
90# inj
-8 feed line running to aeromotive regulator
return line
The fuel pump is directly wired to the Holley dominator harness and grounded to the chassis
now the problem:
Ive been trying to fine tune the nitrous kit on this thing but im having some issues that are not allowing me to really start.
What ive noticed is fuel pressure drops low under load during a Nitrous pass.
I though my accessories and stock alternator were the issue since voltage and psi were consistently dropping at the same time in my logs so i had my alternator amped up to 200 and went out and tested again.
On the new logs :
During a motor pass, voltage stayed 13.3 average with 2 dips to 12.0
fuel psi steadily went down to 51psi from 55 and then came right up to 55 as i let out.
During a Nitrous pass, voltage steadily went down to 12.0 fuel pressure during this went down to 36psi as rpms increased, then shot up to 55 as i let out.
Before the alternator amp up i saw psi drop down to 45 but not as low as today.
Anyways any help on where to look next or any tests i can do to try to get to the bottom of this thing so i can start enjoying it would be GREATLY appreciated. thanks guys!
07-09-2016, 10:31 PM
#3
The car no longer has the stock wiring, I had a complete control panel built for everything on the car,
the motor harness runs seperate though and pulls power and ground from the battery, the fuel pump attaches straight to the holley harness for power wire, and grounds to the chassis( thinking about moving this to the battery )
The alternator was rebuilt yesterday to provide more amps, the battery is a year old red top optima
07-10-2016, 01:08 PM
#6
Where are you getting voltage reading from?
Ideas:
Test voltage at alt
Test voltage at battery
Test voltage at pump.
Is there a difference?
Do you have a 1 wire alt or do you rely on PCM to command charging?
For my race car I had Alt converted so that it always puts our 14 volts. Only wire on it is the thick power wire.
Ideas:
Test voltage at alt
Test voltage at battery
Test voltage at pump.
Is there a difference?
Do you have a 1 wire alt or do you rely on PCM to command charging?
For my race car I had Alt converted so that it always puts our 14 volts. Only wire on it is the thick power wire.
07-10-2016, 05:33 PM
#7
Where are you getting voltage reading from?
Ideas:
Test voltage at alt
Test voltage at battery
Test voltage at pump.
Is there a difference?
Do you have a 1 wire alt or do you rely on PCM to command charging?
For my race car I had Alt converted so that it always puts our 14 volts. Only wire on it is the thick power wire.
Ideas:
Test voltage at alt
Test voltage at battery
Test voltage at pump.
Is there a difference?
Do you have a 1 wire alt or do you rely on PCM to command charging?
For my race car I had Alt converted so that it always puts our 14 volts. Only wire on it is the thick power wire.
Voltage is read from the Holley dominator which connects directlyto the battery.
I also tested voltage at the alternator, power cut off switch, and battery while idle. all ready 13.0
the alternator is a 1 wire, it is on during key on.
i have battery relocated to the rear. using tick perf. battery relocation kit which comes with heavy duty grounds and power wires.
TODAY:
i cleaned up the grounds on the motor, and also wired the pumps ground straight to the battery.
went out to test again with the same results.
voltage drops to 12.0 during nitrous pull,
and the fuel pressure steadily declined to 40 psi while rpms climb. once i let out fuel pressure shoots back up to 55.
im debating some sort of boost a pump device.
any other ideas?
thanks guys
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07-10-2016, 06:35 PM
#9
On my old truck we saw a pressure drop at the top of the rom range. It got worse as rpm increased. This was a sign that we ran out of pump.
So we added a boost a pump.
It fixed the issue.
But I think you have a bigger charge issue here.
I don't like 13 volts when the car is running.
Can you check voltage at higher rpms? It is a 12 volt system but under load, the alt should be putting out close to 14 volts.
Turn lights on, and every electronic in the car and check it. With the nitrous OFF trigger the relays.
What does the electrical system do when fully loaded?
So we added a boost a pump.
It fixed the issue.
But I think you have a bigger charge issue here.
I don't like 13 volts when the car is running.
Can you check voltage at higher rpms? It is a 12 volt system but under load, the alt should be putting out close to 14 volts.
Turn lights on, and every electronic in the car and check it. With the nitrous OFF trigger the relays.
What does the electrical system do when fully loaded?
07-10-2016, 06:40 PM
#10
On my old truck we saw a pressure drop at the top of the rom range. It got worse as rpm increased. This was a sign that we ran out of pump.
So we added a boost a pump.
It fixed the issue.
But I think you have a bigger charge issue here.
I don't like 13 volts when the car is running.
Can you check voltage at higher rpms? It is a 12 volt system but under load, the alt should be putting out close to 14 volts.
Turn lights on, and every electronic in the car and check it. With the nitrous OFF trigger the relays.
What does the electrical system do when fully loaded?
So we added a boost a pump.
It fixed the issue.
But I think you have a bigger charge issue here.
I don't like 13 volts when the car is running.
Can you check voltage at higher rpms? It is a 12 volt system but under load, the alt should be putting out close to 14 volts.
Turn lights on, and every electronic in the car and check it. With the nitrous OFF trigger the relays.
What does the electrical system do when fully loaded?
ill chk what it does when all lights are on.
also i had a friend bring up a good point, it should be noted this car has pwr str delete and a underdrive pulley aswell.
may try to replace the alt pulley with a snaller one.
