Kingtal0n

this can get ugly. ok now i have boost, sooo...

I have a 2barmap. it works fine, i see boost on my computer.

problem is, i just installed larger injectors (42Lb@44PSI) And im having a few problems associated with retardation involving VE and fueling.

for starters, so i dont suddenly combust into flames, some info for you.

The car wont idle closed loop, whether i did something wrong or the injectors are just too big, i dont know but theres info for ya. i think they just go from rich to lean a little bit too big of a jump.

it likes to idle around 2.0-2.2MS
it seems to want to cruise in the 3MS area, maybe a little less its hard to watch while driving. closed loop works while driving.

now the problem comes in where, i dont want to lean out under boost, but i have NO CLUE where to begin my pulsewidth fueling table. I mean, 10MS used to not be that much fuel but NOW its probably a crapload of fuel. im not sure where to begin.

for starters, i put in about 8MS of fuel right when it comes on 1-2PSI of boost (113 KPA) and it started breaking up real bad, so i assume its too much fuel or not enough, probably too much. but im afraid to back it off too much;

suggestions? can i trust the narrowband in this situation? its located in the downpipe right after the turbo. what roughly would my pulsewidth be around 3000rpms, 2-3 psi of boost with these sort of injectors? is that just too hard to figure out?

askulte

Step one is to get yourself a wide band air fuel meter... Based on that, tuning for fuel is actually very easy. Much more accurate than SOTP. I'd set it at mid 12's for now to be conservative. If you can eliminate the AFR dips and mountains when stepping in the throttle, your drivability will be great.

Kingtal0n

I would love to add a wideband, but they are like $450 to work with the computer, and $350~ without the ECU upgrade for my situation. thats alot of money considering its almost what I have invested in my twin turbo setup.

for right now, its gonna have to be narrow-band + SOTP im afraid. right now it needs exhaust and i cant even afford that.

83 Crossfire TA

iTrader: (2)

What ecm/engine management are you using (from the pulswidth numbers it doesn’t sound like a GM ECM, but I could be wrong)?

Kingtal0n

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commander 950. it manages fuel map very simply, you input the numbers that correspond to the pulse width you want.

83 Crossfire TA

iTrader: (2)

Yea, I figured as much… it’s similar to a few of the other aftermarket systems, that is the way that Haltec deals with fueling also, where GM likes VE and maf tables and then calculating pulswidths from that… you never see them unless you’re paying attention to them with a scan tool.

anesthes

iTrader: (12)

Thats because the OEM setups have 8 or 9 values that affect the PW.

I hear the edelbrock 950 is a nice setup, if you use tunercat to program it.

I'm using $58 on my car. After over a month of tuning issues (difference between a truck vs modded car, etc) I got it.. really sweet.

Are you using a DELCO 3 wire o2? If not, you should be.

-- Joe

83 Crossfire TA

iTrader: (2)

Aftermarket ECM’s also use multiple parameters to determine injector pulsewidths, but there is a difference in the thinking in getting there. GM seems to want to figure out what the VE is at that specific point, and then calculate the injector pulswidth from that modified by the rest of the conditions, where the aftermarket stuff that I’ve dealt with for the most part starts with a base pulswidth and modifies it for the rest of the conditions… Unfortunately, I have no experience with the holley setup so I’m not sure what to recommend besides going to their site and trying to find a program for a similar setup and starting from there.

Kingtal0n

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thats exactly what i did, i found a base map for a 355 running 14PSI on a supercharger, with 45Lb injectors. im going to try it out tommarow.

anesthes

iTrader: (12)

What fuel pressure are you running the injectors at?

I'm running 36# ford injectors.. not enough fuel.

-- Joe

83 Crossfire TA

iTrader: (2)

Not enough fuel for what? You should be able to run FMS/SVO 36’s reliably at least as high as 60psi which should feed close to 600bhp…

Kingtal0n

im running 51PSI without the vacuum line hooked up. on these injectors thats like a 46-48Lb injector according to the math. it backfires and breaks up with 10MS of pulsewidth under 2-4 PSI of boost. the new fuel map from holley has 12MS of fuel, so maybe it IS running lean.

I was however, under the impression 12MS of fuel was 500-600 horsepower worth of fuel, but that may be up near 6000 rpms right now i was seeing that 2-4PSI of boost around 3000rpms rolling into the throttle during 2nd gear. Im also running a kind of large gap, maybe its blowing out? .055" or thereabouts. MSd6 of course, but also factory distributor.

anesthes

iTrader: (12)

There is a couple things you need to realize.

1) 36# injectors flow 36# at SAE 43.5 psi, unlike some rumored pressures.
2) I'm running 50psi idle, 55-60psi under boost.
3) Close to 600hp on a n/a .40-.45 BSFC motor. Not a non-intercooled supercharged engine. I'm closer to .65 BSFC.

Car runs just a sniffle lean and injectors are running static under full boost. Hoping the water/alky injection cures it.

-- Joe

anesthes

iTrader: (12)

12ms of fuel at what RPM?

83 Crossfire TA

iTrader: (2)

Right… as a matter of fact, I’m pretty sure that I was one of the first if not the first to point that out around here, years ago. Most injectors are flow rated at 3 bar.

Most of the reason for the higher BSFC for a supercharged engine is that some of the fuel ends up being used for cooling and detonation control. You could avoid that a number of ways, including injecting water, lower compression, some egr action (either through cam timing or by injecting _cooled_ exhaust gasses into the intake), or with killer engine management and careful chamber design you can actually control burn rates by running a _lean_ mixture (lean has the same effect as rich for different reasons, but the “safe” window is much smaller when you’re lean).

If you’re really in the .65bsfc range you’re either running a really safe tune, supercharging a rather badly breathing engine requiring a lot of boost, or compensating for too much compression (yea, don’t all f-body guys believe that a good boosted engine build has 9:1 compression or better )

If you’re basically feeding the engine enough fuel but need the extra to control detonation then injecting just water will take care of you, but if you’re actually short on fuel then adding some alcohol will act as a fuel…

FWIW, my brother’s boosted 4 door ran 11.6 @ 119 with 36pph injectors with no signs of detonation (timing locked out at 33*) seeing between 98 and 100% DC on a pass. Since he was technically getting enough fuel but seriously borderline, upgrading injectors didn’t make his mph any faster but helped his launch and et (by ~.2s) since he really wasn’t getting enough fuel to deal with transients. Larger injectors also made the car much more driveable and much easier to tune for transient response.

83 Crossfire TA

iTrader: (2)

42pph FMS injectors at 51 psi should be flowing roughly 45pph. At 6000rpm you have 20ms to open and close each injector, so 12ms is roughly 60% DC is roughly enough fuel for 390hp at a bsfc of .55

anesthes

iTrader: (12)

I think we're on the same page.

The motor breathes ok, but its around 9:1 c/r. The cam doesn't self egr, and the heads well. THe sportsman-II heads arn't suited well for a blown app.

I get picked on by some of the guys on here saying "9:1 is low compression".. Of course, none of these folks ever boosted a v8..

S-trim at max rpm with a small pully.. 12ish psi. FUlly ported intake.

Yeah I'm using fuel to cool down the air charge. We're talking 180f+ air temps.

20ms? On batch fire TPI, 10ms at 6,000rpm is static.

-- Joe


-- Joe

B4Ctom1

wow! really? so I bet 36's with an FMU would really get it done.

Kingtal0n

hrm <b>20ms? On batch fire TPI, 10ms at 6,000rpm is static.
</b>

thats what Ive heard. my commander seems to think that at 6,000 RPMS there is enough time for 14MS though, weird? maybe thats got something to do with its open/closing time calculation, you can change the rate of opening VS voltage in the calibration right now its set to .8MS open/close time, which is apparently standard for 13~volts at the injector.

Right now, at 3000RPMS I have about 10MS of fuel around 2-4PSI of boost and thats where it begins to break up and backfire. If i hold the motor to about 1PSI of boost, borderline going on 113KPA, it runs fine with 8.5MS of fuel in that area, running up to 9.5MS near 4500rpms. (at roughly 1PSI of boost).

its just when it hits that 2-4PSI mark, pulse width is around 10MS (3000-5000rpms) im sort of shooting in the dark, and it breaks up nasty. pop-pop-pop right out the intake. Like i said, the holley map has 12MS of fuel in the 3000RPM 2-4PSI of boost range, which i think may fix it but no telling till i change it over.

83 Crossfire TA

iTrader: (2)

yep

Depends on if the commander is doing single or double fire…

83 Crossfire TA

iTrader: (2)

and the duty cycle that you can get away with depends on the injectors and drivers.

anesthes

iTrader: (12)

Odd. I don't get into trouble until around 5500rpm at 12psi..

Maybe turn up the rail pressure a bit. I'm running high rail pressure.

Whats the rest of the setup? Can you post or link your entire build. I'm curious. I thought my car was worst on fuel.

-- Joe

83 Crossfire TA

iTrader: (2)

You should be able to get away with an actual injector timing of close to 16ms or higher if you’re doing single fire. As far as the voltage compensation, every ECM that I’ve ever seen (OEM and aftermarket) has it. You’d be surprised how big a difference it makes (hum, I wonder if this might be the cause of the 30 seconds of cold tip in stumble that I’ve been chasing… need to put the car back together and try it).

That sounds like A LOT of fuel for 2psi boost… OTOH, if you’re sure that the backfires are out the intake you’re pretty much guaranteed that you’re running lean. I wonder if you might need more PE/AE (I don’t know what Holley calls it, that’s what GM calls it, Haltech has 2 “accelerator pump shot” adjustments, duration and volume and they are proportionate to the TPS % change and MAP % change).