UPP Secondary fuel system issues
Thread Starter
Staging Lane
Joined: Jun 2019
Posts: 73
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UPP Secondary fuel system issues Like the title says, I'm having issues with my UPP fuel system.
Car is a 1999 C5.
Twin turbo, supporting mods, meth injection ect.
I also have a racetronics pump in the tank and a hot wire kit.
The upp system kicks on in boost like its supposed to but by 10 lbs of boost I start dropping fuel pressure down to 45 or so and going scary lean..
I want to run higher boost but am limited by this issue for now.
Any ideas how to fix this? System is installed correctly and works well under 10 lbs of boost.
Car is a 1999 C5.
Twin turbo, supporting mods, meth injection ect.
I also have a racetronics pump in the tank and a hot wire kit.
The upp system kicks on in boost like its supposed to but by 10 lbs of boost I start dropping fuel pressure down to 45 or so and going scary lean..
I want to run higher boost but am limited by this issue for now.
Any ideas how to fix this? System is installed correctly and works well under 10 lbs of boost.
TECH Fanatic
Joined: Jun 2003
Posts: 1,869
Likes: 99
Probably need to install a boost referenced FPR. If you are still using the stock regulator its pressure is static. It doesn't compensate for boost. It maintains 58 psi all of the time whether NA or Boost. At 10 lbs of boost fuel pressure needs to be increased to 68 psi inside the injector (rail pressure) to compensate for the 10 lbs of positive pressure inside the intake pushing against the outside tip of each injector (58 + 10). So if the stock filter/regulator is maintaining 58 psi at the rail, but there is 10 lbs of positive pressure inside the intake, then the effective rail pressure is only 48 psi (58 - 10).
But these two links explain much better than I can.
https://www.turbosmart.com/news/how-does-an-fpr-work/
https://aeromotiveinc.com/wp-content...c_Boost_01.pdf
But these two links explain much better than I can.
https://www.turbosmart.com/news/how-does-an-fpr-work/
https://aeromotiveinc.com/wp-content...c_Boost_01.pdf
Last edited by dlandsvZ28; Nov 26, 2019 at 11:03 AM.
Thread Starter
Staging Lane
Joined: Jun 2019
Posts: 73
Likes: 0
I get what you are saying but their kit is designed to go onto your factory setup and maintain fuel pressure / supply enough for 1,400hp.. I'm at maybe 650whp and its dropping pressure like its going out of style..
I know what your talking about is a better setup and I'll switch over eventually I'm sure, but for right now I'd just like to get what I have working like so many other people have without needing to get manifold referenced FPR and everything else. At 650whp / 10lbs of boost with 2 fuel pumps and a hot wire kit I should not be dropping down into the low 40psi range..
I know what your talking about is a better setup and I'll switch over eventually I'm sure, but for right now I'd just like to get what I have working like so many other people have without needing to get manifold referenced FPR and everything else. At 650whp / 10lbs of boost with 2 fuel pumps and a hot wire kit I should not be dropping down into the low 40psi range..
Thread Starter
Staging Lane
Joined: Jun 2019
Posts: 73
Likes: 0
Well, I'm going to the 1:1 FPR setup.
That being said, my 60lb injectors are rated at 43psi.
should I set the FPR to 43 or 60 at idle?
I know once PSI is set I then connect my vac / boost reference and it will pull fuel down a few pounds from there.
Also, if I set it for 43 and my duty cycle ends up being to high I'm assuming I'd just re adjust my base fuel PS1 to 60 to make the injectors flow more.
If that were the case, and I had to set pressure to 60 would I still use the 0kpa value in the IFR table across the board or would I need to figure out what they flow at 60psi and enter that number into my IFR table?
I'm assuming if I set it to 43psi I can just flatline the IFR table using the value from my 0kpa cell.
That being said, my 60lb injectors are rated at 43psi.
should I set the FPR to 43 or 60 at idle?
I know once PSI is set I then connect my vac / boost reference and it will pull fuel down a few pounds from there.
Also, if I set it for 43 and my duty cycle ends up being to high I'm assuming I'd just re adjust my base fuel PS1 to 60 to make the injectors flow more.
If that were the case, and I had to set pressure to 60 would I still use the 0kpa value in the IFR table across the board or would I need to figure out what they flow at 60psi and enter that number into my IFR table?
I'm assuming if I set it to 43psi I can just flatline the IFR table using the value from my 0kpa cell.
