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Old 08-17-2014, 09:02 AM   #21 (permalink)
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I am a fan of spark plug mods, but this is really taking a step backwards. You would have much better results/gains by running a normal plug and using ethanol blending to improve the octane rating.


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Old 08-17-2014, 02:59 PM   #22 (permalink)
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But ethanol is bad for the environment, makes you loose mpg, causes the engine to run lean........

Originally Posted by ksa8907 View Post
You would have much better results/gains by running a normal plug and using ethanol blending to improve the octane rating.
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Old 08-17-2014, 03:18 PM   #23 (permalink)
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Let me see if I can summarize:
  • Your car is a 2009 Smart ForTwo
  • Your car has thoroughly modern computer controlled engine management
  • You don't want to feed it 93 octane anymore, as a way to save money
  • You cut threads off one side of the spark plugs
  • You think that cutting threads off the spark plugs is why your car runs okay with 87 octane
I would bet dollars to doughnuts that the plug mod is doing doodlety-squat, and in fact what is happening is that your ECU is pulling timing. That is the *real* reason why you are able to run lower octane.

Here is what I would suggest. Go get some new spark plugs, leave them whole, and install them in your engine. Run several tanks of 87 octane in the car and get honest MPG figures. Then run several tanks of 93 octane, again getting honest MPGs. Try to be as consistent as you can regarding driving conditions. Then compare the MPG differences and see if there is a dollar value to running 87 octane.

Even if you decide not to do the comparison, the very least you should do is replace those mangled spark plugs. The sooner you do, the less it will cost you.
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Old 08-17-2014, 03:44 PM   #24 (permalink)
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What about using washers and some copper grease to lift those plugs a few mm?
A 3 mm thick washer would add about 1 cc(*), that's more than you can get by chopping the thread.

At 333 cc per cylinder and a (guesstimated) compression ratio of 11:1 that would reduce the compressed chamber area (of 30.3 cc) by 3.3 %; it would reduce the compression ratio to about 10.6:1.

And when it gets really cold and your car does not start well anymore you can still just get the washers off and get moving again.

(*) of course that depends on the thread width. Assuming 18 mm here.
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Old 08-17-2014, 10:32 PM   #25 (permalink)
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That what I was saying Red. Why hack up the threads and risk breaking a plug off in the head?
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Old 08-18-2014, 12:34 AM   #26 (permalink)
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Originally Posted by iveyjh View Post
Spark plug non foulers will lower the cr without cutting anything.
Try this if you want to lower C/R.
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Old 08-18-2014, 10:49 AM   #27 (permalink)
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Lower compression and retarded timing are the antithesis of economy. I don't know why anyone thinks this is worth the trade off, regardless of method.

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Old 08-18-2014, 11:56 AM   #28 (permalink)
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Originally Posted by BikerModder View Post
Well here you have it. I am getting remarkable results while driving my car through the Blue Ridge Mountains I have no pinging. It is much cheaper and I won't change my story... Though don't know why... I did. I remember that I ought to at least remember that I did.
If your driving at high altitudes, you don't need as high of octane fuel because the air is thinner up there, and thus your charge density is lowered. High altitude gas stations usually only sell lower octane fuel because of this.
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Old 08-18-2014, 04:43 PM   #29 (permalink)
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Wow I couldn't open the picture on my tablet for some reason, now with a real computer I see whats going on. Holy crap!
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Last edited by oil pan 4; 08-19-2014 at 10:51 AM..
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Old 08-18-2014, 08:39 PM   #30 (permalink)
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This is Premium now.

No more ideas? Enough good threads and octane will lower the risk of predetonation and were it up to the computer but it wasn't meant for that. It lowered it some... Sometimes...

Enough for me to chance the experiment on my Smart car. I was thinking it is a spark plug mod for 87 . I had done this on an 87 Corvette with a thicker gasket by increasing the ceiling .007 which is the amount in ratio to the change of the cylinder volume of the 09 Smart Fortwo. This is good beer if it is hot outside and you want just one.
Thanks for letting me share.

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