How Much Fuel Pressure Is Safe?

[benl1981]

Just looking at getting a little more out of my injectors to support around 225rwkw..

I realise a Nismo FPR is a pretty easy way to get a little more. You raise the base Fuel pressure from 36psi upwards.

I guess the fuel lines are getting old but all EFI hosing should be rated to SAE 30R9 which I think is rated to 125psi with a burst pressure of 900psi. Is this correct?

So currently I have 36psi base pressure (Is that right) plus allowing for boost increase (10psi currently)

Max fuel rail and line pressure = 46psi

So if I raise the base fuel pressure 10psi and run 15psi boost I'm looking at

36 + 10 + 15

= 61 psi

Do other people run this kind of pressure without upgrading there fuel lines etc? I'll check the condition etc and the clamps..

Does anybody know what the fuel filters are rated to - Ryco don't state this.

Thanks

[benl1981]

anyone?

[Craved]

who can say if your 10ish year old lines will hold the pressure ?????

if you are concerned buy about 3m of new 600psi hydrolic line that is fuel safe and use all new host clamps .. then it will hold your fuel pressure without the worry in the back of your mind that it "might" explode/break/crack etc etc

Edited February 12, 2007 by Craved

[MANWHORE]

I wouldn't do it using the stock lines. Have you actually seen them?

I mean actually played with them. Like when you change the fuel filter, give the hose a squeeze.

My car came from japan with about 30 000ks on it (yes genuine, bought from a japanese friend). I've since done a few ks on it, and the hoses are quite firm.

Notice how hard it is to get the filter off, because the hose has hardened and formed aroudn the filter?

Just replace them with a better quality hose. If you go to your local auto one store, they'll know what I mean. They have the cheap hose and the expensive hose.

You'd better replace the hose clamps too with better clamps.

That's not to say that your stock lines and clamps won't cut it, but I like things to be perfect, and the way I see it, it's cheap insurance.

[Beer Baron]

I'm also not 100% sure how well your fuel injectors will cope with an extra 30% (15psi) of pressure behind them, or how well the old stock fuel pump will. I would think bumping it up a few psi would be ok, but I couldn't say where the safe limit is. personally if you need more fuel, start with better pump, and then size the injectors to suit.

[benl1981]

Thanks fellas..

so a few psi is ok...

might upgrade the hose and clamps..probably not a bad idea on an old car anyway.

One thing I still can't find is the pressure rating of fuel filters.

Anyone know the max psi of Ryco or cooper fuel filters.

Also, what is the max psi a GTR pump can deliver - is it around 73psi?

Edited February 12, 2007 by benl1981

[RB30-POWER]

most standardish type pumps don't pump against high pressure well, the flow drops down as the pressure goes up.

however this is where the bosch motorsport pumps shine, they are rated at high pressure, some models 5 bar pressure.

if you have one of these pumps go for it, other pumps i haven't seen specs for, so your more then likely going to have to try it.

injectors vary, if you go too high in pressure the injectors can lock up so to speak and not open, if you go way to high in pressure.

doubling pressure only increases flow by 40% if that give some idea on the possible gains, if you could go that far in reality...

i would happily raise pressure by 10-15psi, but thats it.

fuel lines least of your worries if its efi hose. fuel filter will have a very high burst pressure as well, unsure of actual specs for the filters.

if you have rb20/26 top feed injectors and they are like 15+ years old don't up the pressure as they will leak from the body. (as they will all do anyway, even with stock pressure)

if you have side feed, or new top feed injectors, easily bang 10-15psi extra pressure if you tune to suit, only small flow gain though.

on one of my engines i run 45psi under vac, 55psi at 0" vac and boost on top, 20psi on top is 75psi fuel pressure, but have bosch motorsport pump, ohh and brand new almost r34 injectors. standard 15+ year old top feed leaked in 2 days of driving from the body, haha.

[kismetcapitan]

I ran 700cc injectors at 4 bar (60psi about) at idle on my RB26, stock fuel pump. It lasted about a month before dying, and taking the pistons along with it. US$13,000 later, I'm back on the road....