1st question, Im still having the problem with the engine sounding like its missing or something after 5psi. I put in the fuel pressure gauge and am running 45psi on stock injectors and it boosts to about 100 during boost. is this too high? and by boost I mean by 5psi.

also what is the correct pressure to be running on stock injectors(got my 370's on their way) and also what should the pressure be later for the 370's?

2nd question, what could be causing this hesitation/missing problem? the a/f gauge does say its running extremely rich during boost. could it be flooding? and should I get a different FMU? idk if its the correct one or not..

could I be overfeedin g the engine due to using a 12:1 fmu?

 

also I just found out that i CAN get it to go to 15psi if I take it up there easy. it only hesitates when I really get on the gas.. any ideas? maybe injectors?

 

You should not be running an FMU at all at 15psi on my opinion. I sure as sht wouldn't be running 100psi of fuel pressure... you're just asking for an injector to go static and then it's all over for your engine, or at least your head gasket.

As for your hesitation issue I have no idea, too many possibilities, not enough info.

 

your bogging because your running super rich, you need a better fuel management system like an Emanage.

 

yea thats what i figured. As far as that goes i guess remove fmu, install emanage, and do you think 370cc's will be enough injector? And I tried disconnecting the fmu and i still get the hesitation, So maybe could I have injector damage? So far ive replaced the plugs, coils, and MAF, though I also ordered a z32 maf... any other posibilities? It is something with the ignition or fuel system though it seems...

 

Here in your post, it's 5 psi, right? Nealoc upstairs assumes 15 psi? I'm a little confused on just what boost you're running...

Anyways, on a 5 psi setup, you probably won't even need a fmu at all, just adjust the fuel pressure regulator up by 2-5 static psi's, and you should be good to go. 5 boost psi + 12:1 disc fmu is too high for fuel, thus running extremely rich. You can probably do good with a 8:1 disc already.

Now, if you are running on 15 psi's. 12:1 disc is going to already give you 150+ dynamic fuel pressure. This is not going to work, bro. The larger your boost is, the worse an incremental disc ratio would do on your tunes. When you get above 10 psi boost, you should start tuning by adding a electronic controller...

-Peter-

 

He is running 15psi I believe based upon post #2 in the thread and his pulley size, but starts having problems around 5psi...

trial I don't believe 370s will supply enough fuel for your car at 15psi of boost without a fuel pressure bump. there are calculators out there to help you determine what size injector you'd need.

 

i was using 555 injectors(no fmu) with the 2.62 pulley (15psi) . And i was only taking 3 or 5 % off with the vafc in the mid range.

 

Thanks, Neal, I didn't catch that 2nd post.
For his sake, I second the motion saying that 370cc's wouldn't work for 15 psi's without a slight bump in fuel pressure.



Tiralt, I do think that you need to get rid of that 12:1 disc for the 15 psi boost. It's going to be too rich already once he gets 6 psi's. See, 5-7 psi's boost needs fuel pressure in the 60's. Not 80-90. You're just flooding the engine as I see it from your descriptions.

Here's a little of my rough calculation for the 12:1 disc:
5 psi = 71 psi
6 psi = 83 psi
7 psi = 95 psi
8 psi = 107psi
9 psi = 119psi
10psi = 131psi
11psi = 143psi
12psi = 155psi
13psi = 167psi
14psi = 179psi
15psi = 191psi

Yes, you'll need more fuel on higher boosts, but your 12:1 disc increases fuel by step sizes too great that it actually deviated your A/F target out of whack. On 7 psi boost, you are already running 95 fuel psi, this 95 psi isn't needed till 10 lb boost. You're just running rich A/F's. Need to switch to smaller FMU if you are running under 10lb boosts. But you're doing 15, basically, not one disc size can accomodate your 15psi boost because it'll swing the A/F out of feasible range across the rpms. It may be okay on one segment of the rpm band, but not the whole thing. You'll need to use a smaller disc, around 8:1 along with a tuning system.

As for your injectors, 370cc will not work for your 15 psi boost unless you bump pressure by a slight amount, like Neal said. You'll need a 555cc to be in the ballpark without doing anything else.

This seems like a mess to me, you got a overkilled FMU, and a set of undermined Injectors. You're gonna need to do more homework on this fuel stuff here.

-Peter-

 

It is too much pressure for the walbro to handle. I think they stop working out of the effective range at about 100psi.

12:1 is too high for any boost really.

You either need to put a smaller pulley and get a smaller ratio FMU disk or get much bigger injectors with emanage at least for a 2.62 pulley.

 

ok, so right now I am trying to get an emanage, and i guess i also have to find some 555cc injectors, as for the fmu, its what came with my kit, so ill just remove that. and I hope that will solve the hesitation problem =)

btw what idle pressure should I adjust my fpr to w/ stock injectors now and later to the 555cc?

 

i still have my 555 for sale.... i didn't use any fmu with it and i didn't raise fp i left it stock+ a couple psi from the walbro.

 

so let me get this straight... if i use the emanage and use 555cc injectors i wouldnt have to touch anything else and it would run good?

 

well, if worst comes to worst, can I still possibly make it work with 370cc's for a whuile until I can get some 555's?

 

damnit... the hesitation problem still boggles me.. fmu on or off, it doesnt matter... and its weird because if I ease the gas then it can hit boost and pull how it should, but if I just floor it then it hesitates when it hits 5psi or so... this is so confusing!! so far ive replaced coils, plugs, fpr, and ive attached and detached the fmu, and some 370cc injectors are on their way( I know theyre too small, i ordered them a while ago) soon to be replaced by 555cc's in the future, as well as im ordering an emanage... But I still think it should not be doing tha.. regardless of the injectors or not... and I just find it weird how I can ease it to hit the higher levels but cant just floor it...

 

hey trait, do u have a black 97-99 max with body kit dropped with bodywork all over your car??? do u live in salt lake???

 

do i kno u?

 

i saw ur car in salt lake coming out of the housing area going to the shopping center by mc'd's

 

ya its my project

 

cool...nice project...we should meet up sometime....my 96 max should be up and running in 3 weeks with a 3.5...

 

do u live in salt lake also?

 

i live in waipahu but my gf was driving my car in saltlake all the time...i got the gold 96max se and it had the 18''7spoke g35 rims painted black...

 

Sounds like maybe a maf problem?

 

well im going to change the maf soon so maybe thatll fix it