nx fpss setup psi
07-22-2005, 09:13 AM
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nx fpss setup psi just got an nx fpss from ramchargers, what is the default psi settings on these? how does everyone set theirs up? i dont have a fuel pressure regulator, so i cant do the test light procedure to dial it in to 35psi. please help.
07-22-2005, 02:29 PM
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They come preset at 35psi already. Occasionally they are a little off either direction and need adjusting, but not often. I would suggest installing it on the car and running it, if it happens to be set too high the system will shut off and on (feels like spuddering) and you will know that you need to turn it down a little.
07-22-2005, 02:43 PM
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The fuel pressure safety switch or FPSS is a normally open switch; that closes at a preset pressure. It is used to prevent engine damage in the event of fuel pressure loss, or the lack of fuel pressure. It is installed in the fuel line between the fuel rail (or pressure source) and the fuel solenoid. The FPSS monitors the fuel pressure that the system feeds to the solenoid. It has two terminals that are wired in series with your groundside of the relay.
http://www.nitrousexpress.com/Instructions/fpss.pdf here is the standard wiring for the FPSS.
For an older MSD window switch the yellow wire that normally went to ground would connect to one terminal on the FPSS and the other terminal on the FPSS would go to ground.
There are many ways to use this switch to help prevent engine damage. The one thing that all the diagrams will have in common is the FPSS is put into series with what ever wire is controlling the system.
The FPSS is adjustable. On the topside of the switch there is a rubber plug. Removing this plug and you will expose a hex type screw. Tuning the screw clockwise will raise the set point. Counterclockwise will lower the set point. Normally there is no need to adjust these switches they come from the factory preset. WARNING: setting the FPSS to close to the operating fuel pressure of your system will cause the nitrous system to bounce, chatter or go on off really fast. And setting to far away will not do you much good.
Ricky
http://www.nitrousexpress.com/Instructions/fpss.pdf here is the standard wiring for the FPSS.
For an older MSD window switch the yellow wire that normally went to ground would connect to one terminal on the FPSS and the other terminal on the FPSS would go to ground.
There are many ways to use this switch to help prevent engine damage. The one thing that all the diagrams will have in common is the FPSS is put into series with what ever wire is controlling the system.
The FPSS is adjustable. On the topside of the switch there is a rubber plug. Removing this plug and you will expose a hex type screw. Tuning the screw clockwise will raise the set point. Counterclockwise will lower the set point. Normally there is no need to adjust these switches they come from the factory preset. WARNING: setting the FPSS to close to the operating fuel pressure of your system will cause the nitrous system to bounce, chatter or go on off really fast. And setting to far away will not do you much good.
Ricky
07-22-2005, 02:59 PM
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run with out it. I had nothing but problems with it on. when their is fuel voulum drop the fpss kills everything. due to not having enough fuel flow. not enogh voulum in fpss. took mine off works fine now.
07-22-2005, 03:05 PM
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Originally Posted by NXRICKY
The fuel pressure safety switch or FPSS is a normally open switch; that closes at a preset pressure. It is used to prevent engine damage in the event of fuel pressure loss, or the lack of fuel pressure. It is installed in the fuel line between the fuel rail (or pressure source) and the fuel solenoid. The FPSS monitors the fuel pressure that the system feeds to the solenoid. It has two terminals that are wired in series with your groundside of the relay.
http://www.nitrousexpress.com/Instructions/fpss.pdf here is the standard wiring for the FPSS.
For an older MSD window switch the yellow wire that normally went to ground would connect to one terminal on the FPSS and the other terminal on the FPSS would go to ground.
There are many ways to use this switch to help prevent engine damage. The one thing that all the diagrams will have in common is the FPSS is put into series with what ever wire is controlling the system.
The FPSS is adjustable. On the topside of the switch there is a rubber plug. Removing this plug and you will expose a hex type screw. Tuning the screw clockwise will raise the set point. Counterclockwise will lower the set point. Normally there is no need to adjust these switches they come from the factory preset. WARNING: setting the FPSS to close to the operating fuel pressure of your system will cause the nitrous system to bounce, chatter or go on off really fast. And setting to far away will not do you much good.
Ricky
http://www.nitrousexpress.com/Instructions/fpss.pdf here is the standard wiring for the FPSS.
For an older MSD window switch the yellow wire that normally went to ground would connect to one terminal on the FPSS and the other terminal on the FPSS would go to ground.
There are many ways to use this switch to help prevent engine damage. The one thing that all the diagrams will have in common is the FPSS is put into series with what ever wire is controlling the system.
The FPSS is adjustable. On the topside of the switch there is a rubber plug. Removing this plug and you will expose a hex type screw. Tuning the screw clockwise will raise the set point. Counterclockwise will lower the set point. Normally there is no need to adjust these switches they come from the factory preset. WARNING: setting the FPSS to close to the operating fuel pressure of your system will cause the nitrous system to bounce, chatter or go on off really fast. And setting to far away will not do you much good.
Ricky
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07-22-2005, 03:25 PM
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Originally Posted by badls1
run with out it. I had nothing but problems with it on. when their is fuel voulum drop the fpss kills everything. due to not having enough fuel flow. not enogh voulum in fpss. took mine off works fine now.
07-22-2005, 04:00 PM
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Originally Posted by JustAnIlluzion
hey dude, sweet camaro, im in troy too. u going crusing this weekend?
07-22-2005, 05:51 PM
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As I have previoulsy noted, the FPSS is still a "bug" that needs to be worked out. It's too bad, because I will soon be running an NX wet kit and would want a RELIABLE safety device.
Consensus is to run without it, which is a bummer because if I ever blew my **** up, the block will sit for a looooong time before I could afford to rebuild it.
Consensus is to run without it, which is a bummer because if I ever blew my **** up, the block will sit for a looooong time before I could afford to rebuild it.
07-23-2005, 06:16 PM
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I ordered a FPSS with my NX Wet Kit from Dave. A bussy of mine last week said the same thing, that people had a lot of issues with them?
I never heard of any until this thread. So does anyone run a FPSS and they like it and they work,,,,consistently?
I never heard of any until this thread. So does anyone run a FPSS and they like it and they work,,,,consistently?
07-25-2005, 08:59 AM
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I am honestly surprised to hear of this number of guys not happy with them. As I stated earlier, in the 4 years of being with NX I have personally only heard of one person having a real problem with the FPSS (it was the guy that had it blow up on him). Other than that, it has always been an adjustment issue.
07-25-2005, 08:34 PM
#14
Originally Posted by NXJeremy
Did you try adjusting it?
Don't these cars run about 55 psi fuel pressure? If so isn't 35 psi a little low for LS1 & LS6 cars?
What is the normal drop in psi you should expect to see? At what psi would you be likely to have inadequate fuel flow when spraying?
If NX sets them at 35 psi are they saying you will get adequate fuel flow at 35 psi? But these switches are used for lots of different cars and I expect different cars to have different safe fuel pressure criteria.
Why not watch your fuel pressure guage and if it drops to 45 psi for example when the systen activates wouldn't it be good to set the FPSS to 40 psi, which I would think keep you from having it cause problems but give an extra 5 psi safety cushion over the factory 35 psi setting?
It seems to me it would be better to have the car stumble on you because you had the psi set too high rather than have a broken motor because you had it set too low or did not have a FPSS because you think they are unreliable???
07-25-2005, 09:15 PM
#15
A FPSS is to save your motor from catasthrophic failure (read: fuel pump failure). It is not for detecting an inadequate fuel system (read: fuel pressure drop from volume problem). If your system is dropping 10lbs or more then, imo, you need fuel system upgrade.
Robert
Robert
07-26-2005, 11:47 AM
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yeah i have issues with my FPSS but i beleive its just an adjustment problem. I bypassed it for awile and the system works fine. soon as i get the clutch in and back on the road ill be adjusting it so that it does work.
i run a racetronix and at idle or normal cruising dynotune gauge shows approx 62-65psi depending on weather and how long the car has been runnning. under WOT on the nitrous ive only seen it drop to about 56 or so psi.
i run a racetronix and at idle or normal cruising dynotune gauge shows approx 62-65psi depending on weather and how long the car has been runnning. under WOT on the nitrous ive only seen it drop to about 56 or so psi.
07-26-2005, 11:55 AM
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Originally Posted by Robert56
A FPSS is to save your motor from catasthrophic failure (read: fuel pump failure). It is not for detecting an inadequate fuel system (read: fuel pressure drop from volume problem). If your system is dropping 10lbs or more then, imo, you need fuel system upgrade.
Robert
Robert
Robert is exactly right. The FPSS is simply a device to help prevent catostrophic engine damage. If it is set too high (read-too close to the psi that your vehicle drops to at WOT w/ system activated), then you can get a stuttering issue with the system and that is not better than having it set at 35psi on an LS based motor IMHO. 
07-29-2005, 10:01 AM
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Sorry, Terry. Here is your answers.
I hope this helps Terry.
Originally Posted by terry s
Can you use air pressure and a continuity checker to set the FPSS? You can't use air pressure, but you could use a continuity tester. It would be easier to what a guage though.You would have to start the car (to build pressure), then turn the car off. Now activate the fuel solenoid and as the pressure bleeds off you will need to watch a fuel psi gauge and pay attention to when the FPSS cuts the system off. Then you could adjust it and do the whole process over again.
Don't these cars run about 55 psi fuel pressure? If so isn't 35 psi a little low for LS1 & LS6 cars? Yes, they run between 55-60psi. Again the FPSS is mainly to prevent extreme engine damage.
What is the normal drop in psi you should expect to see? At what psi would you be likely to have inadequate fuel flow when spraying? This is hard for me to answer since I have not driven an LS1 that had a fuel pressure gauge within view while driving. I would say that it shouldn't be more than 10psi (for a split second).
If NX sets them at 35 psi are they saying you will get adequate fuel flow at 35 psi? But these switches are used for lots of different cars and I expect different cars to have different safe fuel pressure criteria. Again, the FPSS is not a monitoring device. It is only to prevent catastrophic damage to the engine in the event that it loses an abnormal amount of fuel pressure.
Why not watch your fuel pressure guage and if it drops to 45 psi for example when the systen activates wouldn't it be good to set the FPSS to 40 psi, which I would think keep you from having it cause problems but give an extra 5 psi safety cushion over the factory 35 psi setting? Of course you can do this, but do you think it is going to be a very large amount of time between the pressure dropping from 40psi to 35psi in the event of a fuel pump failure, fuel filter clog, or over extending the abilities of the fuel system? If there is an abnormal drop in fuel psi, I don't think there will be much time between 40 and 35psi.
It seems to me it would be better to have the car stumble on you because you had the psi set too high rather than have a broken motor because you had it set too low or did not have a FPSS because you think they are unreliable??? I would not recommend not using a FPSS, in my experiences with them (NX's) I have found them to be very reliable. INHO the FPSS isn't too low at 35psi. It will do it's job of protectin the motor from a total meltdown when set at that pressure, which is all I personally am concerned with.
Don't these cars run about 55 psi fuel pressure? If so isn't 35 psi a little low for LS1 & LS6 cars? Yes, they run between 55-60psi. Again the FPSS is mainly to prevent extreme engine damage.
What is the normal drop in psi you should expect to see? At what psi would you be likely to have inadequate fuel flow when spraying? This is hard for me to answer since I have not driven an LS1 that had a fuel pressure gauge within view while driving. I would say that it shouldn't be more than 10psi (for a split second).
If NX sets them at 35 psi are they saying you will get adequate fuel flow at 35 psi? But these switches are used for lots of different cars and I expect different cars to have different safe fuel pressure criteria. Again, the FPSS is not a monitoring device. It is only to prevent catastrophic damage to the engine in the event that it loses an abnormal amount of fuel pressure.
Why not watch your fuel pressure guage and if it drops to 45 psi for example when the systen activates wouldn't it be good to set the FPSS to 40 psi, which I would think keep you from having it cause problems but give an extra 5 psi safety cushion over the factory 35 psi setting? Of course you can do this, but do you think it is going to be a very large amount of time between the pressure dropping from 40psi to 35psi in the event of a fuel pump failure, fuel filter clog, or over extending the abilities of the fuel system? If there is an abnormal drop in fuel psi, I don't think there will be much time between 40 and 35psi.
It seems to me it would be better to have the car stumble on you because you had the psi set too high rather than have a broken motor because you had it set too low or did not have a FPSS because you think they are unreliable???
I would not recommend not using a FPSS, in my experiences with them (NX's) I have found them to be very reliable. INHO the FPSS isn't too low at 35psi. It will do it's job of protectin the motor from a total meltdown when set at that pressure, which is all I personally am concerned with.