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Discussion Starter · #1 ·
My engine mod: S1

Ok, so my stock wires died, and it turned out that the MSD 8.5mm wires were cheaper than the stock ones, so I got them.

I installed them and everything was great, for a short while. After about 2 days of driving around I noticed that the car felt weaker. I got out on the highway and did a couple 3rd gear pulls. Sure enough, it wasn't going up to 14 PSI.

I thought about the problem, and I knew I didn't have any boost leaks, so I figured I'd reset the ECU (I did this by disconnecting the battery - I didn't know about the ignition trick). Once I reconnected my battery, I took it back out on the highway - 14 PSI once again. So I figured the ECU was detecting knock and pulling boost and possibly timing. I guess the low resistance of the wires means more eletrical power goes into the spark, increasing cylinder temperature.

I didn't want to be resetting the ECU all the time, so I just filled up with 94 octane. The car boosted 14 PSI constantly. After a few tankfulls, I went back to 91 octane. Sure enough, the engine would not go above 11 PSI after a short period of time.

So my thoughts are that if I want to be able to use 91 octane and still make power, I'm going to need to change to possibly colder plugs. Am I right? Those of you running MSD wires, which plugs do you use with them, and what gap? I'm using 0.050, and am considering increasing it to 0.055 or even 0.060 to see if it helps increase the resistance enough to lower the power (and heat) going into the cylinder. Am I off the wall or on the right track?
 

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Discussion Starter · #3 ·
AdvanSRT-4 said:
What mods do you have?

Try a smaller gap, like 0.032 or 0.035.

Atlas said:
My engine mod: S1
Don't you usually decrease gap to correct blowout? My car doesn't even come close to blowing out. Besides, a smaller gap has less resistance, which means even more current, which means even more power in the spark. If I'm right about what's causing the ECU to pull boost, a smaller gap would be worse.
 

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Atlas said:
My engine mod: S1

Ok, so my stock wires died, and it turned out that the MSD 8.5mm wires were cheaper than the stock ones, so I got them.

I installed them and everything was great, for a short while. After about 2 days of driving around I noticed that the car felt weaker. I got out on the highway and did a couple 3rd gear pulls. Sure enough, it wasn't going up to 14 PSI.

I thought about the problem, and I knew I didn't have any boost leaks, so I figured I'd reset the ECU (I did this by disconnecting the battery - I didn't know about the ignition trick). Once I reconnected my battery, I took it back out on the highway - 14 PSI once again. So I figured the ECU was detecting knock and pulling boost and possibly timing. I guess the low resistance of the wires means more eletrical power goes into the spark, increasing cylinder temperature.

I didn't want to be resetting the ECU all the time, so I just filled up with 94 octane. The car boosted 14 PSI constantly. After a few tankfulls, I went back to 91 octane. Sure enough, the engine would not go above 11 PSI after a short period of time.

So my thoughts are that if I want to be able to use 91 octane and still make power, I'm going to need to change to possibly colder plugs. Am I right? Those of you running MSD wires, which plugs do you use with them, and what gap? I'm using 0.050, and am considering increasing it to 0.055 or even 0.060 to see if it helps increase the resistance enough to lower the power (and heat) going into the cylinder. Am I off the wall or on the right track?
Your problem solving and test prodecure is SPOT ON!! Good job!!!

Yes AdvanSRT-4 is completley off base and his suggestion will do nothing for you.

You're absolutley right, a colder plug might help you run better when using 91 octane,if your hypothesis is true. The best way to check this by reading the timing to see if its reduced, since there are other factors that would cause the ecu to limit boost.

The plug gap has little to due with temp of the plug. Yes it takes more voltage to bridge a larger gap but the current is what causes what ever heat is generated and it won't be changed. With that said the closer you can get the plug gap to .100" and STILL fire reliably the better.

Champion has a "platinum" RE10pmc5(~$3 at Autozone) that are good 3-4 steps colder and will more difinatively test your idea of the plugs causing the boost drop

Note: NGK 4306 are NOT colder than stock
the Champion "Hemi" plugs are NOT colder stock
 

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Discussion Starter · #5 ·
Thanks! That is extremely helpful.

When you say check for reduced timing, do you mean I should see what the timing is with 94 octane, then see if it changes with 91 octane?

Also, what can limit boost that is affected by fuel octane rating? I know temperature and pressure can, but it's been 60-75 degrees and 1.0 bar pretty consistently here...

I'll try increasing my gap since I should do that anyway.
 

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Food for though:

I was running MSD wires and tried switching to Mopar wires as a last resort because I was getting 6 degrees of KR on 15psi with my 60trim. After switching to the Mopar wires my KR went to 0. That was the only changes made.
 

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Discussion Starter · #8 ·
I wonder if there is something wrong with MSD wires then - suppose they don't suppress EM noise as they are supposed to, what would be effect be?
 
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