fuel rail, uprated injectors, fuel PR

[Drax]

Unless your going turbo or the Stage 3 cams route, is there any real point in getting an uprated fuel rail and bigger fuel injectors? as the ludes traditionally run pretty Rich already (and apparently mine stank of fuel when on the national meet dyno lol) so im trying to justify them in an engine build.

Ive been advised to get a fuel pressure regulator anyway, not sure on peoples thoughts here?

p.s. i already have an uprated fuel pump as my old one was suspected to be dodgy so i thought to swap to a Walbro 255 while i was at it.

[mercutio]

I don't think you need an fpr but it all depends how far your looking to go in the future. An fpr only raises pressure at the injectors doesn't do anything other than allow more fuel through the injectors per time of opening as far as I can make out check out robs build thread he explains it all pretty well.
Or just have a chat with the guys at Paw

[judderod]

The larger 4th gen injectors are big enough for all but the most insane NA builds.

[nucleustylzlude]

As judderod says, they're man enough for basic mods before you start building a high C/R block. And Merc is right a FPR is only required when you need to raise the pressure to squeeze more fuel out of the existing injectors, but by doing so you raise the duty cycle. It's only when you're raising the duty cycle too much that you need to invest in bigger injectors.

So in theory you could add a FPR to add more fuel for mods, but go with other mods first and some decent tuning before bothering with that.

[nucleustylzlude]

This is the fuelling guide I wrote that Merc was talking about:

http://www.ludegeneration.co.uk/post1910.html#p1910

[Lude-dude]

have one on my build, rich recommended I get one

that's about 244hp build

also have fuel rail, but I just added that for bling I think

[nucleustylzlude]

Well that's fair enough for 244bhp.

According to my calcs, the standard 4th gen 345cc injectors are good for 210bhp at 80% duty cycle (recommended cycle). The maths, if anyone is bothered = 345cc / 10.5 = 32.86 lbs/hr. 32.86 x 0.8 (80% duty cycle) / 0.5 B.S.F.C (brake specific fuel consumption) = 52.57hp per injector.

52.57hp x 4 injectors = 210.29hp (at 80% duty cycle).

Of course we can increase the fuel trim in tuning to a point before you need to introduce an adjustable FPR to up the pressure too. Then you'll hit a limit before larger injectors are required and bring down the duty cycles again. For example my build as in my link is rated to around 303hp at 80% duty cycle. Great, for my goals (assuming I've worked out my mods and psi correctly based on other similar builds) should land me around this point, so I can stick with the OEM fixed FPR.

It's all just methods of throwing in more fuel.

[Drax]

Ok, so if im right into what your saying Rob, if im after a medium build of Skunk2 Stage2 tuner cams, ATR pistons, P&P Head, ATR Inlet, 66mm TB, CDA cone and a (hopeful) prediction of around 250bhp, id need uprated injectors, fuel rail and FPR? or still not worth it

ill ask PAW and read your thread as well at the same time

[nucleustylzlude]

For those mods and power goals then I would agree with you to get something, either an adjustable FPR or uprated injectors, most likely the FPR to begin with, cheaper and easier to make the changes required.

On a side note, with a duty cycle over 90% is getting into the realms of 230-240hp+, which is pushing the injectors.

[nucleustylzlude]

Oh and a fuel rail at that point is just bling, but didn't stop me getting one as well though - but this allowed me to run my custom AN fuel line.