EFI fuel pressure ?

[camcojb]

Originally Posted by supremeefi

I tune it for minimal correction so if you bump the pressure and the O2 is correcting it'll correct right back to the preprogrammed air/fuel, period.

If it's tuned to where the O2 has a big correction to begin with then yes it will fatten it, only because the O2 runs out of room so to speak.

my point was that if it's tuned for minimal correct and then you bump the pressure that much, it will no longer be tuned for minimal correction.... You are correct, should have enough room for the O2's in closed loop to correct it, but my point was that it will change the O2 correction and a tuning adjustment will be needed to get it back as close as it was. Not saying it won't run. Just saying I would tweak the tune to get it back to optimal.

Jody

[supremeefi]

Originally Posted by camcojb

my point was that if it's tuned for minimal correct and then you bump the pressure that much, it will no longer be tuned for minimal correction.... You are correct, should have enough room for the O2's in closed loop to correct it, but my point was that it will change the O2 correction and a tuning adjustment will be needed to get it back as close as it was. Not saying it won't run. Just saying I would tweak the tune to get it back to optimal.

Jody

O.K but you said it would run richer, it won't, not if the O2 has enough room to correct.

The opposite is true when someone has tuned it for minimal correction and then you use fuel with more ethanol in it, guess what, it'll have to add fuel. But as long as it was done correctly there shouldn't be an issue, no more so than an older EFI'd car that was calibrated for 100% petroleum based fuel and now runs on todays 90/10.

[camcojb]

Originally Posted by supremeefi

O.K but you said it would run richer, it won't, not if the O2 has enough room to correct.

well, it will run richer during warm up, cold start, and any open loop areas. That's also a big "if" on if there's enough room for the O2 to correct. Should be I agree.

We're not disagreeing, just playing semantics. My point was raising the fuel pressure will affect the a/f and I would re-tune to compensate to get my trims back in line and to get my cold start and open loop areas back where they need to be. But you are correct in that there should be enough correction available in the O2's to at least keep the closed loop areas in line, but again that assumes the tuning is right in the first place. If the O2's are already maxed out or close to it, and are pulling a bunch of fuel in closed loop to maintain the desired a/f then raising the fuel pressure will cause it to run richer then desired all the time...........

I do appreciate your info and feedback.

Jody

[Denvervet]

Thanks for all the input guys Didn't mean to start something...lol Supreme once I get my project to that point I just my hire you to help some. I do have a person that came highly recommended and well versed in Gen 7 stuff lined up locally. After reading some posts here even expert (?) people can struggle with this Gen 7 stuff.

[MrForce]

Most older OEM fixed fuel pressure regulators were set at 3 bar (43.5 psi), therefore the injectors were rated at that pressure. If you change the fuel pressure to 58 psi (the OP's question) the injectors do flow more, search the web for the formula. For the Gen 7, simply plug the new injector flow rate into the config screen and all is good without a re-tune.


Peace,

Rob

[supremeefi]

Originally Posted by MrForce

Most older OEM fixed fuel pressure regulators were set at 3 bar (43.5 psi), therefore the injectors were rated at that pressure. If you change the fuel pressure to 58 psi (the OP's question) the injectors do flow more, search the web for the formula. For the Gen 7, simply plug the new injector flow rate into the config screen and all is good without a re-tune.

Peace,

Rob

Not true, it won't change the VE number automatically.
The Gen 7 uses 7 parameters in a mathematical formula, one of which is the VE, to calculate how long to pulse the injector to achieve the desired air/fuel. If you change the fuel pressure after doing the tune and change the fuel pressure value in the config as mentioned, then you'll need to change all the VE numbers to a lower value. However this can be done easily by clicking and dragging across the entire table, pushing the X key and multiplying everything by .90 or whatever. In theory you would have the same amount of excess in all areas.