Fuel pressure for 80 lb siemens fuel injectors

Talk and Tech about turbocharged 924/944/968 cars
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blade7
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Fairly simple check for plug wires is to start the car in a dark space, and you may see them shorting out. Do not touch the wires with the engine running under any circumstances. It can really hurt, or kill you.

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notny41
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yes, I was thinking about doing that just to see if I could see any arcing. i pulled plug number 4 and it seemed pretty carboned up. Once the new plugs get here I’ll toss those in and see if clears up a little more. right now after replacing the coil has been a dramatic improvement.

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Tom
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notny41 wrote: Mon Nov 13, 2023 9:54 am yes, I was thinking about doing that just to see if I could see any arcing. i pulled plug number 4 and it seemed pretty carboned up. Once the new plugs get here I’ll toss those in and see if clears up a little more. right now after replacing the coil has been a dramatic improvement.
Glad you are making progress. Ignition is my go-to guess for on-boost stumbles on the 951-- and it rarely disappoints. :)

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notny41
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Ok, plugs arrived today. I gapped them all to .028

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I pulled the old ones out. Mixture looks very rich to me with the possible exception of #3 and #4.

Makes me wonder if I should back the fuel pressure regulator off a little.

I will take it out for a spin tomorrow and see if it feels any different while driving.

I checked the gap on the plugs that I pulled out and they were between .032 and .035 on my feeler gauge.

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Tom
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Do you have a wideband? Vitesse software is pretty dialed in (as long as you are running the fuel pressure and injectors it's mapped for). Missing and stumbling can screw up plugs too. I'd run it with the new plugs (and wires?) and see how it does. If it really is is running rich, I'd be inclined to use the FQS, assuming you have the specs for your chipboard.

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notny41
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what’s a wideband? also what is an FQS? not sure what chips are in the car. i did connect a laptop to the car one time.

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notny41
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Well, just had it out for a spin. New plugs didn't seem to make too much difference. I will try wires next and then rotor and cap.

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Tom
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notny41 wrote: Fri Nov 17, 2023 12:41 am what’s a wideband? also what is an FQS? not sure what chips are in the car. i did connect a laptop to the car one time.
Ah, sorry. A wideband oxygen sensor is an aftermarket O2 sensor that monitors the exhaust and tells you exactly what your air-fuel-ratio is on a real-time basis. It takes all the guess work out of trying to figure out if your car is rich or lean or just right. They are popular on modified 951's and other turbo-tuner cars, since air-fuel ratios are so important for power and head gasket preservation. (Ignition advance is also important, but that's a whole different thing.) Here's a thread showing me put a wideband into an old Mercedes, just to give you the idea.

viewtopic.php?t=222

FQS is 944-lingo for Fuel Quality Switch. There is a little rotary knob with 8 settings on the DME computer that allows you to add and subtract a small amount of fuel and/or ignition advance. It was intended by the factory to let you tailor your fuel and timing to the quality of your local gasoline. However, if your car has a Vitesse MAF, then it also has a Vitesse chipboard rather than simple 'chips.' The chipboard is a small circuit board that plugs into the chip socket and does some active processing of its own, in addition to supplying tuning maps normally found on the memory-only 'chips' used by the factory. As part of all that, Vitesse re-purposed the FQS to hold custom maps in the various 8 locations (maps for race gas, e85, etc.). So unless you have the details that came with your Vitesse MAF, I'd probably stay away from the FQS.

Fingers crossed the new wires help....

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notny41
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Put the new wires on and it still feels like a faint (but consistent) miss or maybe a better term for it would be a shudder when getting on it good in 2nd gear. I guess I can try swapping out dizzy and rotor from my other car but I'm not real confident that will make a difference either...

I forgot to mention this car does have a lindsey turbo boost enhancer on it too - do you think that could have anything to do with it at all?

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notny41 wrote: Sun Dec 03, 2023 8:52 pm Put the new wires on and it still feels like a faint (but consistent) miss or maybe a better term for it would be a shudder when getting on it good in 2nd gear. I guess I can try swapping out dizzy and rotor from my other car but I'm not real confident that will make a difference either...

I forgot to mention this car does have a lindsey turbo boost enhancer on it too - do you think that could have anything to do with it at all?
I would not think the boost enhancer would do that. Do you know if Vitesse MAF came with those injectors?

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