Big time fuel problems grrrrrr

[gs14racer]

Ok, guys heres the skinny.

Im out of fuel.

I replaced my fuel pump with a brand spanking new walbro 255hp. The car doesnt drop fuel pressure anymore and doesnt go crazy lean anymore but i am officially out of injector.

Data logs show

at 5800rpm 87% injector duty cycle and 12.3 afr wotand by only 6600rpm99% duty cycle 12.1 afr wot.

Clearly im out of injector, now heres some ideasBand-aid ideai can run the injectors @ 4br 59psi rail pressure and give me a new flow of about 430cc per minute, and i should see 88-90 percent duty cycles by redline. Only problem is that with that rail pressure the walbro 255 will only flow enough fuel to support 440cc injectors. So ill be maxing out the pump yet again!!!! My only solution to this is to run either a second walbro intank, or an external pump such as an aeromotive.

The right idea.Grab some deatscworks 550cc injectors and run them around 74 percent duty cycle by redline, but once again not enough for the walbro as at standard rail pressure it will only flow enough for 480cc. So im in the same boat.

My main problem is $$$ i have officially run the project fund dry here, i cant afford to do both the pump and the injectors, so do you guys think that runnning the stock injectors at 4 bar and 88-90% duty cyclle is a bad idea? Obviously i would imagine that 99 percent is much worse, but im really concerned about the 12.1 afr as i would like it to be a tad lower in the 11.7-8 range.

What are you turbo guys doing, i find it so hard to believe im flowing so much air through this motor that dumping 370cc of fuel per cylnder is not completly pig rich? I mean the maf is pegging 5.094 volts @ redline, which is the highest ive logged but im not to concerned with that as much as the high duty cycles and afr.

[gs14racer]

also to verify my afr readings, i pulled the plugs after a wot pull and the ceramic is spick and span white.

[scir16v]

What about 440cc injectors instead of 550's? Will the duty cycle be too high with those?

[newbissan-tech]

im not a big turbo guy jerry but i've seen guys run 440cc injectors on all motor honda's so i could definitely see you running lean with 370cc's on a boosted vehicle especially on this beast of a vh. when doing a small turbo upgrade on a stock honda we put at least dsm 450cc's and that's only running like 6-8lbs. of boost. what size are the stock injectors??? (370) and is that what you're running? man i hope you get this thing lined out! good luck

[T45]

Instead of varying the injectors...just hook them to +12v constant and put the fpr next to the gear shifter. 100% d.c. and no worries! Or...we could plumb an extra fuel line into the brake booster port. There's always a solution man, think outside the box! lol

BTW, Im staying at my girls house sat night, getting up early sunday and probably be there around 7-730 or so. Off fri,sat,sun so holla if you need a hand!

[CrazyTrance]

Yes, stock injectors are 370cc.

It sounds like either way your going to have to go to a higher flowing fuel pump or dual setups. On an SR you can get away with going to 550cc injectors on a Walbro because there are only 4 injectors to feed. VH you've got 8. Dual pumps is my vote along with new injectors. Budgets suck.. i know.

[Mettler]

Apparently you can linish off the end face of the injectors (decapping I think it's called), and it increases them by heaps, they go up to like 650cc after doing this mod.

I haven't got much more info at this stage, but this is word of mouth from a reliable source who plans to do this with his VH41DE injectors.

Might pay to do some googling and look into it!

:edit: Here's a thread about doing this mod on subaru injectors, check it out:

http://forums.nasioc.com/forum...78921

[CrazyTrance]

^^ I have heard about the Subaru guys doing it and it works really well from what i understand. I would definitely check that out Jerry. As long as the fuel will still disperse properly and "atomize" i think it would be worth trying.

[gs14racer]

Well, i bumped up the fuel pressure to 60 psi, and took it out for a drive. Hit afrs of 11.0 at wot 6800rpm, so thats good. I didnt however hit 99 percent injector duty cycles, in the mid to high 80s, now i dont know if thats a function of the increased fuel pressure maybe slowing down the injectors, or the fact that i hit 1 less load point in every gear, i can only imagine that being caused by the temperature last night which was 94 degrees, so it was pretty hot, compared to my previous runs.

[CrazyTrance]

How much cooler were the temps during your last runs?

[gs14racer]

it was damn near 15 degrees cooler, mid to low 80s. I have no leaks before the maf, which is the only thing that would cause less load. Boost was still the same and the maf still hits 4.99 volts at redline.

[LEMHEAD16]

what are you using for data logging?

[gs14racer]

the nistune, which is some pretty awesome software.

[XJared]

A Walbro 255 will make over 500whp with big enough injectors, I've done it. Keep your pump, and put in a set of injectors and be done with it.

[Guishnu]

What about a 2.5ltr swirl pot, walbro in-tank, 044 main pump and 4.5bar fuel pressure?

[Nealoc187]

How are you calculating that your fuel rail does not have the capacity to flow XXX cc at a given fuel pressure?

While I have 0 experience with VH rails I can't imagine that they're much different from the VG/VQ/SR/KA rails that I do have experience with, and they have no problem with a single walbro pump flowing that amount of fuel at reasonable fuel pressures.

Aside from that, making custom fuel rails is incredibly easy, and it could provide a good opportunity to upgrade to some top feed injectors. Top feed injectors have more responsive coils, run cooler at higher duty cycles, and are able handle higher duty cycles before going static than the JECS side feeds than VHs and most nissan motors from the early to late 90s use.

I'd advise against doing the mod that lots of subaru guys do when they don't want to spring for bigger injectors, while it increases the flow as stated, it also makes the fuel atomization properties of the injector pretty poor. Far from ideal.

[Q45tech]

Why not add a 9-10th injector just after the Throttle Body and a simple cotrol to pulse it appropriately. By 4,000 rpm the air flow is enough to mix the fuel enough.

[dsagers]

Here is a good example.

http://cgi.ebay.com/ebaymotors...21088

[gs14racer]

while all those are good ideas, they are ultimatly band aids for the main problem.

I posted my temporary solution on the other thread but i guess it didnt translate this way.

I got a new walbro 255hp pump and bumped up the fuel pressure to 60psi rail, that got me to 88-90% duty cycle on the injectors. That will be fine for the time being.

Next month, i will be upgrading to an aeromotive a1000 external pump, with a -8 feed line, then it will Y off to the fuel rails , basicly to dual feed the rails, and those will come back to an aeromotive fuel pressure regulator. Then ill go -6 return back to the tank. That couple with the 750cc fuel injectors im also getting should insure plenty of room for growth .

Ive also been toying with the idea of running e85, but thats another topic all together.

[Bart]

Im using the Edelbrock #1790 for the EFI And Edelbrock #1791 for the surge tank.No probs with the 1790, will instal the 1791 soon.

[Loch Ness]

have stillen make u a computer....450zxtt has a stillen computer........ur computer tune right now will burn up the valves since u have a '94 motor(which dont have the sodium-filled) valves and ur a/f ratio under boost isnt in the low 10's more than likely.....get a q45/TT Z32 fuel pump and injectors[good till 10psi] used for cheap

450zxTT Automotive Extreme Enginerring A.X.E. Power Baby!!

[Chrispy300]

Aren't the standard '94+ exhaust valves inconel like the TT 300ZX? Plenty of them getting around running ~12:1ish

[SuperHatch]

Aren't the standard '94+ exhaust valves inconel like the TT 300ZX? Plenty of them getting around running ~12:1ish

No, stainless on the intake and exhaust, verified by M2 Race Systems when they prepped my heads.