Question and an FYI for all you boosted FMU guys....

[Magnus]

With the turbo and SC kits coming out.... what are you guys doing about fueling, are you even thinking about fuel?

FYI, I ran out of injector in my NA setup at 50psi with a walbro in tank... but you guys will be using FMU's to boost fuel pressure,.. stock injectors lock up at high pressures. I think Mike Huff was having injector freeze problems around 80 psi or so..

For 6-8lbs of boost you should be ok with the stock setup, but if you want to push anything more you really should consider fueling upgrades, like bigger injectors and most definately an in tank fuel pump.

In power adder applications, fuel is critical to engine life.

PCM tuning really can't provide you with the kind of fuel a big boosted application needs. It can calirate for fuel curve, but won't increase fuel delivery. Only way to do that is bigger injectors, FMU that doesn't lock up injectors, and fuel pump.

So what do you guys plan to do?

[malloynx#2]

keith; you think my injector's are going to be able to handle this new cam. i already got a walbro in the tank

[Magnus]

really depends on how high you rev. My setup was seeing 22ms pulse widths at high RPM's... anything past 6K and my injectors would be over worked.

I put up a table in the engine tech database..

Putting in accel 24 lb'ers dropped my MS's to around 18 or so.

[Radcat]

Already have everything but the walbro ;)

[Tiago]

yea on the turbo kits as radcat said we run fmu, injectors and the big walbro

in teh future I woudl love to get PCM programming to eliminate the FMU and get more precise fuel and spark curves (badly needed).

[John_D.]

I'm running a power adder, at 150 additional hp, so I'll share my fuel solution...

It happens to be nitrous rather than a blower or turbo, but fuel requirements is still fuel requirements... [img]smile.gif[/img]

I went with 24lb injectors, and the standard bypass line to the fpr for a dry kit. I also rejetted to a 28 bypass jet vs. a 42 or whatever came with the kit, so I am applying more pressure to the vacuum port than typical, but no more than what the blue regulator allows (I have no idea what that value is by the way..)

I hold about 65 psi on the standard 85 dry shot and above. Up until I ran a 120 shot that is, then fuel pressure would fall off to 40-45 on the last third of the track. (So 120 additional hp, and the stock fuel system can't keep up anymore...)

I put on a boost-a-pump and then I starting running rich on the 120 shot with all the fuel I was getting then. So to fix that, I went up to a 150 shot. :D (more than one way to skin a cat...)

Still ran rich. I can hold nearly 70 psi if I crank the boost-a-pump all the way up. I run it on about 35% (max setting is 50%) and it holds 60-65 psi again. It still is running a little rich even now.

Even running rich, I am only seeing 20ms pulse widths at the top of my shifts, with 150 extra hp demand on the system. (note that a single stage nitrous system self-tapers off on top end though, since the jet flows the same at low rpms as it does at high rpms... Meaning that the "additional" fuel requirement is not quite as high on top end, if that makes sense. The percentage of nitrous to normal intake charge is less.

When I get done tuning to pull the o2's down, the pulse widths should come back down some more, to a safer range. If I remember right, 20ms is right at 100% duty cycle at 6k. (I guess I could go look at the table huh!??)

[ May 06, 2003: Message edited by: John_D. ]</p>

[TurboProject]

I didn't even consider using my stock fuel system with the turbo. I started out with 24# accels and an FMU when I put the turbo on. Then as I saw my pressures die off at WOT I put in a 255 high pressure walbro and I've never seen it run lean. My problems are heat, not fuel, I need an intercooler...I ran a tank of 100 octane 93 mix and boosted to 10psi and it took it beautifully...

[Magnus]

Excellent, you guys got it down!

How about all you new ATI beta guys, what do you plan to do?

[Arctc Wolf]

the 24 lb injectors look like they do well w/ a FMU for higher hp cars. the bigger fuel pump is required to be able to feed the higher fuel pressure and bigger injectors. I'd suggest 26 lb injectors, but i dunno if the computer could deal w/ that big a difference in fuel injector size. Also, some ppl forget that making the engine more volumetrically efficient will reduce fuel requirements to make the same hp. That's why proting the heads and blending bowls and bigger valves all help make mroe power, but by upping the volumetric efficiency.

[98GREENGLOW]

Wow thanks guys, this is some great imformation so please keep it going.

[Tyler]

how much would a set of 24# injectors cost for our cars?

the 3.8 that is

[John_D.]

ACC-150624 PERF FUEL INJ 6PK 24LB $173.69

That's from Summit Racing.

[TurboProject]

That's pretty good, although it's on back order. I paid $230 for 8 accel 24# from jegs.

[Magnus]

I'm selling a set of 8 used accell injectors.. 24 lb'ers for $100.. search the for sale if your interested, don't reply here about it cause this is not the for sale section, this is just a heads up.