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Discussion Starter #1
I'm going on 40K miles with my fuel injectors that run at 80 PSI under full boost. How long will they last and what would be the symptoms when they are worn out? Has anyone else had a problem running this much pressure for this many miles?
 

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It has zero impact on injector wear or longevity. You know something is up when your fuel trims start going out of spec. Usually the spray pattern goes to crap and cold start and idle function gets bad first. If everything is working fine then I would not worry about it. You could run a larger injector and bring the fuel pressures down. I run a max of 62 psi making over 1,200 HP on E-85. Base fuel pressure is only 40 psi. It is good to remember that as fuel pressure goes up, flow/volume goes down. So the higher the pressure, the less volume of fuel you can deliver to the engine.
 

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Discussion Starter #3
I'm asking because I get a bucking, or misfire occasionally at high load, 80 psi. Sometimes I can't reproduce it so I'm thinking it may be the injectors.

 

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Most likely spark blow out. Stick a fresh set of plugs in it and close the gap by .005
 

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Discussion Starter #5
Dun dat. No good.
 

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spark is kinda like fire. You can tell how hot it is by the color. Blue means it is a really hot spark. Orange is not quite as strong. It can even look white, which is pretty weak and needs part replacement.

pull a spark plug wire off.
stick a screwdriver in it,
then place the screwdriver close to a grounded metal while someone cranks the engine.

I usually try to set it down on the plenum or maybe an accessory bolt if I can do so and leave a gap to see the fire.
 

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Discussion Starter #9
Ok, never heard of that. I did just install a screamin demon coil with no change.
 

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Discussion Starter #12
Did that too, nuttin' changed.
 

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Indo-Canuck-Yankee
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Is the MAF pegging out? What MAF?
 

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Discussion Starter #15
Yes, it's at WOT. It only happens at WOT.

I believe the MAF is from an '89 Mustang. I don't have any diagnostic/tuning device.
 

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measure the voltage of maf signal while you redo that run

you will need to setup the leads so you can see it in real time
 

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Indo-Canuck-Yankee
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Don't mean to rain on your parade there, but my engine exceeds the stock 55mm MAF flow (835 kg/hr) at as little as 3700 RPM under boost.
 

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Discussion Starter #18
Am I looking for the voltage to max out? Doesn't it run open loop at WOT anyways?
 

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Indo-Canuck-Yankee
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Yes, you're looking for the MAF voltage to peg out, somewhere past 4.7V. If it does this before your engine is wound out, you've basically got a MAF that's too small and can't read all the additional air mass that's being crammed into your engine by the supercharger. Since the computer will only see whatever kg/hr flowrate the maximum MAF voltage your MAF transfer function supplies, your injector pulsewidths at that point will be limited there. It doesn't work, you need a MAF with enough headroom to measure your maximum airflow.

The MAF is still used during WOT open loop operation. You might consider running a 90mm LMAF. Not expensive and very reliable.
 

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Yes, it's at WOT. It only happens at WOT.

I believe the MAF is from an '89 Mustang. I don't have any diagnostic/tuning device.
This is old school stuff, Before different ECU's, chips, & tuning. It can be made to work.
MAF is too small for you build. 55mm sensor will work in a larger housing, since all 4-pin sensors are the same. MAC (formerly C&L) is an option. They can be tricky to choose & install, so most feel they are junk (they are not).
Your Build:
'88 Mustang GT-GT40 Iron Head Engine w/stock cam, Kenne Bell SC/FMU, stock AOD w/trans cooler and shift kit, '89 mass air/computer, 1.7 roller rockers, Moroso cold air intake, subframe connectors, etc.
 
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