Justin 87 GTA

iTrader: (3)

I am about 2 hrs away form having the S-Trim kit running. Just putting back the oil pan and what not. I got a Walbro 340 intank fuel pump. My question is, do you think Ineed to use an FMU w/ the setup? The one I have is dissasembled and I'd have to have it sent back and re-gasketed and whatnot. W/ 26lb inj. and the pump, I was hoping that I wouldn'tneed the FMU, but the guy at Vortech, said theat the kit was "designed" to run w/ the FMU and not using is would risk detonation. What do you think. Do youthinkmy pressure will be high enough? Thanks

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SUPERCHARGED 87 GTA: Blk/Gld w/Superam, 355cid Trickflows, forged pistons 9.5:1. Auto 2,600 stall, 3.45 9 bolt disc, Best time & mph (Naturally Aspirated): 13.567 @ 101.900 w/ a poor 60ft. Best mph: 104.3 *This car is 100% NYS emissions legal, w/ all emissions controls!* "If you want to have a fast car, hang out w/ those who do!"
http:// www.community.webtv.net/munks87/JustinsGTApage.com
VORTECH S-TRIM, INSTALLATION IN PROGRESS: 10 & 15 LB> PULLEYS, CUSTOM HKS RACE BYPASS, CUSTOM DUCTING W/ COLD AIR, SWAPPING TO SERPENTINE, & MANY EXTRAS! BEST TIME: 11'S I GUESS. WE'LL SEE IN SPRING!

IROCKZ4me

The fuel pump will reduce the risk of not supplying the fuel rails with a consistant supply of fuel.
It will not increase the amount of fuel metered or change the air/fuel ratio though. It will just ensure that enough fuel volume is fed to the fuel rails to keep them full and pressurized.

The larger injectors will increase the fuel metered into the engine.

You can also increase the amount of
fuel metered into the engine by changing the injector pulsewidth with a custom PROM.

Changing fuel pressure also changes the amount of fuel metered. That is the method used with an FMU

The potential problem is that the stock mass air flow meter (MAF) and ECM & PROM are calibrated to measure air up to 255 GPS and meter fuel to match. If you flow more air than 255gps the ECM & PROM will still pulse the injectors to meter fuel for only 255gps even though the airflow increases beyond 255gps.

Vortech uses the FMU to increase the fuel pressure so that more fuel is metered than the stock PROM pulses the injectors to deliver.

You do not have to use an FMU but if you don't then you will probably need a custom PROM to increase the injector pulse width at and above the RPM where the stock system maxxes out.

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Tracy /AKA IROCKZ4me
'86 IROC-Z Camaro
"Cogito ergo zoom"

• 355 cid
• AFR heads
• Arizona Speed & Marine hydraulic roller cam w/ AFR hydra-rev kit
• modified SLP runners
• TRW forged pistons/ceramic coated
• fully balanced
• Edelbrock headers/ceramic coated
• SLP cat-back
• Paxton supercharger
• Nitrous Express nitrous oxide

EFI Performance Club on Yahoo

SecretFormula

Justin,you don't have to send it back to vortech to be regasketed!I sent you at least 2 new gaskets with the recalibration kits.If you are uneasy about doing the changeover, send it back to me,and i will do it for you. Give me a call,Don B.

Willie

iTrader: (1)

The safest and most efficient method to determine what you need (or not need) is to record O2 voltage at WOT. I feel the bare minimum equipment you need in a blown application is a scanner (Auto Xray, Diacom, etc.), a vacuum/boost gauge and an on-board fuel pressure gauge.

If you're producing 10 psig boost (for example), record O2 voltage at WOT and let off the gas at 5 psig. Evaluate the O2 voltage. If it holds between 850 to 900 mV, you don't need any more pressure (fuel) to that point. Retest but increase boost to 7 psig. Evaluate the data again. Step it up in small increments until you obtain full boost. This is the safest method to use.

Personally, I believe an FMU is the worst way to manage fuel in a blown application. It taxes the entire fuel system and it is not adjustable (linear). It is very possible that the O2 voltages may be where you want it at low boost, but not high boost (and vice-versa). Or you may develop a lean condition at mid-boost. An FMU cannot correct for any of these conditions.

One alternative is to go with larger injectors and a custom EPROM. The problem with this "solution" is that it tunes only on the top end. Low-end driveability will suffer. Here's an example: I'll use a BSFC of 0.47 which is considered to be the value to use in modern fuel injected engines. If you have stock 22# injectors @ 50 psig, this injector will support 401.36 horsepower. To bump up to 24# injectors, fuel pressure needs to be lowered to 41 to sustain the same power without compromising bottom-end performance and driveability. For 26# injectors, the pressure needs to be below 40, which is something you never want to do because of the lack of atomization. Therefore with larger injectors, you'll be pumping way too much gas at low engine speeds, which results in sluggish throttle response. This can be compensated for somewhat with a custom EPROM, but not completely.

These are the reasons why I have never used an FMU. I decided to select my injector size and calibrate my EPROM for a normally aspirated engine. The Superfueler system I use takes care of additional fuel needed through its three dedicated injectors when in boost, as read by a dedicated MAP sensor.

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Willie

Supercharged 1987 305 IROC-Z, Daily-Driver, Emissions-Legal.
Former Paxton (6-psig) with 50-hp nitrous: 12.043 @ 112.86 mph.
ATI D1SC (10-psig): 12.056 @ 116.62 mph.
All stats are altitude corrected for 3,100 feet using NHRA's Altitude Correction Table.

http://willie.camaro-firebird.org/

1987 "20th Anniversary Commemorative Edition" Z28 Convertible -- Super Chevy Show Class Winner, 1998.

[This message has been edited by Willie (edited July 08, 2001).]

Justin 87 GTA

iTrader: (3)

Don, I appreciate the offer, but they said that because I took it totally apart, and took out the piston, it has to be rebuilt by them, because it will not hold vaccum, due to air bubbles in the small gasket and thin metal plate inside. Kinda sucks, but ohwell. i've been trying to call you, are you going to e-town, my car will be there w/ the charger, I just might not run it. Hope to see you, call me before you go. thanks for all the replies everyone.

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SUPERCHARGED 87 GTA: Blk/Gld w/Superam, 355cid Trickflows, forged pistons 9.5:1. Auto 2,600 stall, 3.45 9 bolt disc, Best ET (Nat. Asp.): 13.567 @ 101.900 w/ a poor 60ft. Best mph: 104.3 -*100% NYS emissions legal*
http:// www.community.webtv.net/munks87/JustinsGTApage.com
VORTECH S-TRIM, Install completed 7/9/01: 10 & 15 LB. PULLEYS, HKS race bypass, Custom cold air, Swapped to serpentine. Best ET: High 11'S I Hope. We'll see July 14th @ E-town!

Guido

I took my Vortech FMU apart to change the fittings on the top of it lsat year to have -6AN connections instead of the NPT connections. I put it back together and it worked just fine. I think they are feeding you a line to be honest.

But good luck! Hope to see you guys this weekend.

Hi Don!

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-86 IROC
S-Trim, Speed Pro, AFR
this years goal: 10.50 @ 130+ mph
-=ICON Motorsports=-

Justin 87 GTA

iTrader: (3)

Yeah, I will be there. But like I said, probably not runnning, because I haven't done the fuel pump or the FMU yet, and my tranny is on the way out. If I get the FMU back in time I may make 1 pass.

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SUPERCHARGED 87 GTA: Blk/Gld w/Superam, 355cid Trickflows, forged pistons 9.5:1. Auto 2,600 stall, 3.45 9 bolt disc, Best ET (Nat. Asp.): 13.567 @ 101.900 w/ a poor 60ft. Best mph: 104.3 -*100% NYS emissions legal*
http:// www.community.webtv.net/munks87/JustinsGTApage.com
VORTECH S-TRIM, Install completed 7/9/01: 10 & 15 LB. PULLEYS, HKS race bypass, Custom cold air, Swapped to serpentine. Best ET: High 11'S I Hope. We'll see July 14th @ E-town!

SecretFormula

bring that fmu to the track,we'll get you running! I will definately be there on sat. I will be looking for you.Do you still want to try that e-prom? I will bring it with me.
Goido,I'll be bringing you some cogs!
I'll see you guys down there,call me if you need anything.

Guido

cogs. lol

If I had em, Id try em once or twice.

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-86 IROC
S-Trim, Speed Pro, AFR
this years goal: 10.50 @ 130+ mph
-=ICON Motorsports=-

89 Pollo

My FMU actually leaked from a fitting when I installed it. Instead of sending it in and waiting another 7-10 days. I carefully took it apart so I could reseal the fitting that was leaking. It never leaked after that, but at 4 or 5 pounds of boost the car would just fall on its face like someone shut the ignition off. After I let off the gas and got out of boost the car would run fine. I ended up putting a gauge on the fuel side and realized the FMU was restricting up to like 90 lbs! The injectors could not pulse at that pressure. I sent it in, they repaired it for nothing and the car has not had any problems. What happened is beyond me.

just fyi,
Mark

Justin 87 GTA

iTrader: (3)

I think that's why they said they have to do it. I had it apart too, put it back together, and then took it apart again. I saw a huge air bubble just like they said under the piston. So needless to say, I sent it out yesterday anyway. I appreciate the offer Don, but I didn't even put in the fuel pump yet. So either way, I don't think it would be wise to run it. Believe me I want too. But, Don't forget, my tranny is ready to blow up also. Being that I am so far away, i guess that would be an expensive tow. I will be going to bristol soon, and will meet yout there. But either way, I'll be at E-town, this weekend, hanging out and whatnot. It'll be a pleasure just to drive it. Don, if you want to bring the chip, I'd like to try it, but I would have to hold on to it until the next weekend so I could use it at Long Island Dragway. Btw, how is your car coming, give me a buzz. later -Justin

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SUPERCHARGED 87 GTA: Blk/Gld w/Superam, 355cid Trickflows, forged pistons 9.5:1. Auto 2,600 stall, 3.45 9 bolt disc, Best ET (Nat. Asp.): 13.567 @ 101.900 w/ a poor 60ft. Best mph: 104.3 -*100% NYS emissions legal*
http:// www.community.webtv.net/munks87/JustinsGTApage.com
VORTECH S-TRIM, Install completed 7/9/01: 10 & 15 LB. PULLEYS, HKS race bypass, Custom cold air, Swapped to serpentine. Best ET: High 11'S I Hope. We'll see July 14th @ E-town!

[This message has been edited by Justin 87 GTA (edited July 10, 2001).]