Fuel Pressure/660s

[Mike 99GSX]

I just installed my 50 trim T3/T4 last week and last night I swapped in Denso 660s into my 2g in place of the RC550s. I have a VPC/GCC with the 550 chip.(Buschur says their 660 chip won't work in a 2g). I have had the base FP set at 43 without vaccuum. Basically, I couldn't keep the car running unless I kept the idle up to about 1500, if I let off the gas the car would die. I decided to lower the base FP to about 38 without vaccuum and the car started right up and idles great. I datalogged a few runs and was able to dial in about 20 degrees advance with EGTS touching about 1550 in the top of 3rd. I assume its OK to lower base FP with bigger injectors right as long as I'm not running lean up top? Also, this should help my gas mileage a little during daily driving? Oh yeah fuel pump is a 255HP and I have the Aeromotive FPR.

 

[nowayout]

I have 660 and vpc/AFr my car idles great with the 550 chip your talking about. It idles at 750 rpm. My fuel pressure is an 43 with vaccum.
But my car is a 1G so it's hard to compare munbers.

 

[Mike 99GSX]

Thanks. My main question though was about altering the fuel pressure. I assume its OK to lower it as long as I don't run out of fuel up top?

 

[RipperXX]

I think it should be fine as long as your not runing lean.

 

[candela]

Yes its fine to lower it. But you wont be taking advantage of the injectors. If you get a somewhat steady idle the way it is now (not bumping around in 'inHg' on the boost gauge) then adjust with the vacuum line hooked up. I would say that you shoudl at leist leave it at stock pressure so you get the rating you paid for in the injectors. I also have a VPC/AFC, 660's, afc, and 255lphHP and my base is 50psi with vacuum line on. I was hittting close to 88% DC with injectors on 18psi pump (91 piss) so I bumped it, and lowerd the idle on the VPC and it worked out just fine. However I have the 660 chip in mine....

 

[Mike 99GSX]

Thanks for the info. The obvious advantage that you've got is being a 1g. I can't see any of that stuff unless I had DSMlink. It would be helpful to know my duty cycles to see where I'm at.

 

[candela]

everythign I mentioned can be done with a 2G... I dont see duty cycles either I have to do the math to convert...

 

[Mike 99GSX]

Originally posted by candela
everythign I mentioned can be done with a 2G... I dont see duty cycles either I have to do the math to convert...

Could you please explain this. What numbers do I use then to figure out the duty cycles? This would be very helpful.

 

[candela]

injector pulse width is seen at the ecu. The conversion will be different for every car cause everyone will have somewhat different dead times (the time it takes to fire the injector). But basically you take the 1 or so millisecond it takes to fire and subtract it from the total time it shows on yoru logger which is picking it up from the ecu adn thats yoru duty cyle...you just need to convert and it will depend on injector and such.

 

[Mike 99GSX]

Correct me if I'm wrong but there is nothing regarding duty cycles on my 2g pocketlogger. I've got STFT, LTFT, o2, timing and thats about it.

 

[candela]

ok well just forget I said anythign then...I have had a total of maybe 3 runs with a logger on a 2G. If there isnt an injector pulse width option than NM, but if there is then thats what you use.

Note to self- boy pocketloggers for 2G's really do suck...

 

[nowayout]

I'm thinking of bumping my fuel pressure to 50 at idle too. Running into 90% duty cycle at 14psi of boost with 660cc.

 

[nowayout]

play around with the fuel pressure this morning.

increase the base FP to 50 psi with vacuum. Lower the idle setting from 0 to -8 % on the HKS AFR . Seem to do the trick it's idling good.
Will drive it layer to se if the duty get to 80% or less.

720 cc here I come. !!