what fuel pressure?

[DSMeclipse4G63]

Ok heres one of my 2 questions. I have a 95 gst mods are as follows: 1g bov, 1g throttle bodie, mild ported intake mani, 1g intercooler, boost set from 13-16 psi(depending on day), intake, and cat-back exhaust. ok what should I set the fpr to and what is the stock setting?

also I am getting one of those fuel pressure gauges that hooks up to a fuel line ir filter, and as u know the 2g fuel filter is way down on the firewall. I was wondering is there a better place to install these? pics would be nice if possible tahnks for ur help.

 

[90AWDTalon]

Stock fuel pressure is 43psi. I wouldn't play around with changing the pressure untill you get a logger. Even after getting a logger I would only make very minor changes untill you get some sort of AFC to control the fuel, changing your fuel pressure, changes the effective size of your fuel injectors.

 

[DSMeclipse4G63]

I was figuring 45-47 psi fuel pressure to make up for added boost. I am sure a few psi will net some gains added security when boosting and wont affect gas mileage signifacntly. Thanks for responses

Oh yeah does anyone know if there is a better way to mount a fuel pressure gauge, the kind that usually go on the fuel filter. Is there any way this can be mounted in a better location? if so please reply.

 

[djpast]

i runa 1g NT FPR on my car which is 47psi. trust me, without tuning tools like an afc. you car will run like poo.

edit: i also have a TMO logger

 

[DSMeclipse4G63]

damn that sucks...my civc ran I think 20 something psi and I boosted it (civic and boost dont belong in same sentence sorry) to 35 and my car ran fine infact noticably faster than stock fuel pressure. Obviously I got worse gas mileage. Mabey Im stupid tonight but what would cause it to run like poo?

 

[90AWDTalon]

The ECU doesn't know you've increased the fuel pressure, which increases your injector size, it keeps telling the injectors to open and close as if nothings changed so with each pulse you get too much fuel. A couple of psi probably would be ok for some safty margin while under boost, but you will run richer at other conditions. Personally I'd want a logger so I know exactly what going on.

Bigger increases will make the car run worse, for example using the N/T fuel pump in a 1g, would be the equiliant of putting 514cc injectors in. If you have no afc to control this it's not going to run very good. You can use the formula squareroot( new psi/old psi ) * injector flow ( rating at 43psi) = new injector size. Using the example above:
sqrt( 47/36 ) * 450 = 514.17


I hope this is understandable, I'm kind of tired and it feels like I was rambling.

 

[djpast]

yep hes correct. i run 550s with my NT FPR so they roughly put out 627cc of fuel at 47psi.

NT FPR @ 47 psi
sqrt(47/36)*450cc = 513cc
sqrt(47/36)*550cc = 627cc
sqrt(47/36)*660cc = 752cc
sqrt(47/36)*680cc = 775cc
sqrt(47/36)*720cc = 820cc

Aftermarket FPR @ 43psi (what injectors are rated at)
sqrt(43/36)*450cc = 490cc
sqrt(43/36)*550cc = 599cc
sqrt(43/36)*660cc = 719cc
sqrt(43/36)*680cc = 741cc
sqrt(43/36)*720cc = 784cc

most 2gs wont even have to worry about this as their stock FPR is 43 psi

and jsut so you know.... 1G injectors stock only put out 410cc stock. damn low fuel pressure!

 

[djpast]

Originally posted by DSMeclipse4G63
damn that sucks...my civc ran I think 20 something psi and I boosted it (civic and boost dont belong in same sentence sorry) to 35 and my car ran fine infact noticably faster than stock fuel pressure. Obviously I got worse gas mileage. Mabey Im stupid tonight but what would cause it to run like poo?

well considering most civics have 240cc injectors and most stock honda FPR are set to 42.5-43 psi stock i am kinda interested in how you got those numbers? was that on a gauge?

even if you ran the PSI you said you did.... lets just say 20 or even 29 psi and you went to 35.

sqrt(35/20)*240cc = 420cc
sqrt(35/29)*240cc = 290cc

now. if it was on the the 20 psi side, you would be running incredibly rich. civics running DSM 450cc injectors usually run v-afc. and lower the fuel about 35-40%. and those are usually turbocharged

 

[DSMeclipse4G63]

yeah I cant remeber the exact number but it was 20 somthing psi on my 96 ex 2dr. I boosted it to anywhere from 30-35 and noticed a signifacnt diff in performance. And yes it was on a gauge that I got these settings. thanks alot I was tired and wasnt aware tahnks for the info