fuel pressure

[budd]

Can anyone tell me the std fuel pressure '95 Griff 500(into/at the fuel rail), I'm fitting an adjustable fuel regulator, and need a (safe) base setting until I can get it on a dyno and make a more accurate adjustment.

[Guillotine]

28psi in standard trim, but you can take it upto 32psi without jamming the injectors for more power.

use a VERY good regulator (i have a webber in mine) the FSI one was crap...dropped to 22 could have burn out the top end.

as you know, too much NOT to little!!!

[budd]

I'm looking at getting AEM or Aeromotive regulator from the states, 20 to 100 psi adjustment range. It will be interesting to see the dyno results, will lifting the pressure at the injector a little make more power or just waste fuel?. It's got to be running a touch lean with the recent ACT inlet mods, 32psi should be abit safer until I can get the Mark Adams to look at the ECU may even gain a couple of BHP.

>> Edited by budd on Thursday 7th October 22:21

[GreenV8S]

I don't know how much pressure your pump can generate at the flow rates required by your engine, but if you raise the pressure too far you can end up beating the pump. Your pump probably won't last very long if you do this. Sod's law says that the problems will be worse under load when the fuel pressure and flow requirements are both higher. Raising the pressure also increases fuelling over the whole map, including part load where overfuelling might result in pretty driveability as well as long term coke buildup, fouled plugs, and depending how far you go more damaging effects such as bore washing and oil contamination.

I agree that too much fuel is better than too little, but go too far from the optimum in either direction and you can end up in trouble.

Edited to add: unless you are suffering from detonation and use fuel as a charge coolant to allow more aggressive ignition timing, adding more fuel than the optimum will reduce the net power output.

>> Edited by GreenV8S on Thursday 7th October 22:29

[Guillotine]

running at 32 could save your engine if you have act tripple and give it max at a track day.

low fuel can mean cooked heads. i was at a track day at mallory when a very expensive engine did this!
when mine was tweaked i was told to stay below 75% throttle 'till the fueling was sorted. Griffs run lean on standard maps anyway!

TOO high (over 32) will cause the injectors to jam. not good either.
with act stuff an increase in pressure will help BHP but its a waste if not mapped correctly. you can't beat a mark adams set up to get the mix right thru the range as Peter says.