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Author
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Topic: Blowing out the spark....
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Liv4Spd
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Member # 3784
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posted
 
 
Guys I am at a loss, I've got a 93 Cobra with a Vortec SQ, FMU, custom auto logic chip, MSD coil, distributor, wires, plugs @ 1deg colder than stock, full BBK exhaust etc etc. Aside form the blower and exhaust the engine has never been opened up and is bone stock. I'm pretty sure that my ignition is running hot enough but I could be wrong seeing as how this problem is persisting even as I shorten the gaps. Originally the gap was at .035 and then I dropped it down to .032 and this is where it has stayed. I'm worried that if I go any lower "like .030" I might do more harm than good.
I have been having persistent problems with my spark blowing out around 5200-5300 RPM and other than closing the gap some more I don't have any idea as what to do with it. As you all are aware, centrifugal blowers don't even hit peak boost until around 4800 RPM and I'm missing out on my power band. Can anyone recommend a fix for this.....should I cut the gap down some more? What should I do?
Posts: 67 | From: East Bay | Registered: Nov 2003
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mtbaughs
Road Racer
Member # 4052
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posted
Well you won't hurt anything going down some more but why not just buy an ignition booster instead and be done with it. I assume this is a case where the spark is blowing out and not another issue. Crane HI-6 boxes are nice with the built in rev limiter. Easy to install. Good luck.
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R.I.P. Charlie Bruno Dec 2001
Posts: 2019 | From: Boise, Idaho | Registered: Jan 2004
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wilit
Mustang Messiah
Member # 3367
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posted
How much boost are you running? I've run 18psi in my old SVO with .035 gapped plugs and the stock ingnition and never had a problem. What exactly leads you to believe the spark is actually getting blown out?
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"If a man hasn't found something worth dying for, he isn't fit to live." - Martin Luther King Jr.
Posts: 4793 | From: 37.78514° North 122.40100° West | Registered: Oct 2003
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Liv4Spd
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Member # 3784
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posted
Sup Mike ![[Big Grin]](biggrin.gif)
The only reason I'm avoiding the ignition booster is #1 the money and #2 all the people I've heard that haven’t needed a booster with setup similar to mine.....I guess what I'm getting at is why should mine be any different?
BTW running 8 pounds of boost
[ March 02, 2004, 10:27 PM: Message edited by: Liv4Spd ]
Posts: 67 | From: East Bay | Registered: Nov 2003
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ray95
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Member # 752
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i don't think you're blowing out your spark plugs but i would buy an msd or crane ignition box anyway. i like my msd and can notice a big difference with & with out it.
Posts: 895 | From: The Bay Area | Registered: Jan 2002
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Blu50Stang
CAFords OG
Member # 489
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posted
Are you sure you are having spark blowout? Can you describe the symptoms?
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Ross
'88 GT - 5.0&SF 4/04 | MM&FF 8/09 | MM&FF 79-93 Mustang Performance Cover 12/12
'17 GT350R
Posts: 1916 | From: Not CA | Registered: Oct 2001
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9lbpony
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Member # 3510
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posted
Keep in mind - spark blowout feels exactly like valve float...
Posts: 111 | Registered: Oct 2003
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wilit
Mustang Messiah
Member # 3367
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posted
Can you describe the symtoms a little better? Also can you describe your setup? It sounds more like you've got a lean spot rather than the spark blowing out. Unless there's something majorly (is that a word?) wrong with your ignition, 8psi should not blow the spark out.
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"If a man hasn't found something worth dying for, he isn't fit to live." - Martin Luther King Jr.
Posts: 4793 | From: 37.78514° North 122.40100° West | Registered: Oct 2003
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Liv4Spd
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Member # 3784
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posted
quote:
Originally posted by Blu50Stang:
Are you sure you are having spark blowout? Can you describe the symptoms?
I'll do my best...
For example, WOT my car runs like gem up through about 4500 RPM by this point I'm at about 5 to 6 pounds of boost. Around 4900 to 5300 I notice that my power band starts too feel like it's starting to fall flat, albeit slightly. Come 5300 the first signs of "hesitation" arrive, almost like a hiccup.... Anyways at this point I have arrived at full 7 to 8 Psi. The remainder of my RPM "6250" the car persists with the same hiccup that arrived at 5300 RPM. It also seems like in this last 1000 RPM my power band starts to fall flat on its face, or in other words it feels like my power stay the "same" through 6250.
Posts: 67 | From: East Bay | Registered: Nov 2003
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Liv4Spd
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Member # 3784
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posted
quote:
Originally posted by wilit:
It sounds more like you've got a lean spot rather than the spark blowing out.
Pretty sure lean is not the problem. Without an FMU it seems feasible, but wouldn't it compensate for the engines demand for fuel? It's not like I've got a 500HP beast on my hands. Also, there is absolutely NO detonation or pinging.
Thanks guys!
Posts: 67 | From: East Bay | Registered: Nov 2003
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wilit
Mustang Messiah
Member # 3367
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posted
Detonation and running lean are two completely different problems. Detonation is caused by the fuel combusting too early, and actually "pushes down" on the piston as it's trying to move up, causing the pinging sound. You won't always hear a lean condition. A lean condition comes from not having enough fuel, and can feel like you're engine is falling flat on it's face. Just having the FMU will not guarantee a stoich mixture. An FMU will only increase the ammount of fuel the injectors can "squirt", you still need the computer to be calibrated to make sure the injectors fire for the proper length of time, and at the right time. If I were you, I'd invest some time on a dyno with a wideband to make sure your A/F is correct.
[ March 03, 2004, 12:21 AM: Message edited by: wilit ]
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"If a man hasn't found something worth dying for, he isn't fit to live." - Martin Luther King Jr.
Posts: 4793 | From: 37.78514° North 122.40100° West | Registered: Oct 2003
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Liv4Spd
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Member # 3784
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posted
If I hook up a wide band that'll tell me what I want to know....at least fuel mixture wise, right?
Posts: 67 | From: East Bay | Registered: Nov 2003
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wilit
Mustang Messiah
Member # 3367
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posted
What size injectors are you using, what type of FMU, what type of fuel pump, what's your static fuel pressure set at, what is the ratio of your FMU? Also, what year car is this? 5.0? 4.6?
Yes, a wideband will tell you your A/F, and at least narrow down the problem to whether or not it is a fuel problem or an ignition problem.
[ March 03, 2004, 12:24 AM: Message edited by: wilit ]
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"If a man hasn't found something worth dying for, he isn't fit to live." - Martin Luther King Jr.
Posts: 4793 | From: 37.78514° North 122.40100° West | Registered: Oct 2003
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Blu50Stang
CAFords OG
Member # 489
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posted
quote:
Originally posted by Liv4Spd:
If I hook up a wide band that'll tell me what I want to know....at least fuel mixture wise, right?
Yes. I want to point fingers at the FMU, but you should be able to tell when you get the wideband. It is probably cheapest to take the car down to be dyno'd with an a/f reading.
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Ross
'88 GT - 5.0&SF 4/04 | MM&FF 8/09 | MM&FF 79-93 Mustang Performance Cover 12/12
'17 GT350R
Posts: 1916 | From: Not CA | Registered: Oct 2001
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JohnB
Tech Moderator
Member # 969
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posted
Definitely sounds like an FMU problem. If you ease into the throttle, will the car make the desired RPM? If it does, you have a faulty FMU. All the FMU does is hold line pressure when there is an increase in boost. More than likely, the disc inside the FMU is sticking. I had this same exact problem with my 93. Tore the FMU apart, put a new 12:1 disc kit in, ta-da..no more problem. ![[burnout]](graemlins/burnout.gif)
Also, make sure your vaccum source for the FMU is from the tree, no other source is acceptable. ![[Smile]](smile.gif)
Edit: the belt IS tight, right? The problem you're describing can be belt slippage also...
[ March 03, 2004, 08:22 AM: Message edited by: JohnB ]
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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CobramanPhil
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Member # 2170
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posted
It still may be spark blowout (even though you are gapped smaller and have a decent coil). Back in the days when I first start started modding the car, I would get spark blowout at around 5300rpm. I first thought it might be fuel related (fmu problems or the fmu just doing too good of a job by putting out too much fuel at high rpm). I did the smaller gaps, better coil, and replaced the fmu disk (even tried putting a bleeder valve on the fmu) and I would still get that hesitation. Once I put the crane ignition it...all the problems were gone
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2013 Shelby GT500
2011 Porsche 911 TurboS/AWD
2014 GSXR750
2002 GSXR750 Track Beater Bike
2016 Explorer Unlimted
Posts: 1016 | From: California, Bay Area | Registered: Dec 2002
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2stangs69-91
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Member # 1951
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posted
I will chase you all over the internet LOL Aotolite racing plugs gaped at .028 or .030. All the reaserch has been done for you by me LOL. so just do it.
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69 Mustang on hold
1991 LX hatch getting a make over
1994 F150 4X4 351
2006 Yamaha V-max 1200 Modded
Posts: 3711 | From: Redding | Registered: Oct 2002
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Liv4Spd
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Member # 3784
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posted
So do you think I should try regapping my plugs to .028 or .030, I've heard this helps.....j/k
Thanks for your help everyone!
Posts: 67 | From: East Bay | Registered: Nov 2003
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