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Author Topic: Compression change from 208 psi to 250 psi  (Read 4463 times)

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Offline crazycraftsman

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Compression change from 208 psi to 250 psi
« on: August 27, 2016, 08:16:02 pm »
This is on a 35 vanny twin . Was running 92 non ethonal , should I change to vp 110 race gas? Will help it run cooler? More compression more heat right? Thanks for any help
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owen
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Offline Jim Knutson

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Re: Compression change from 208 psi to 250 psi
« Reply #1 on: August 27, 2016, 08:44:49 pm »
Owen, I do not know what you have for fuel choices up there....but I have no issues with non ethanol 98 octane we can get here.
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Offline crazycraftsman

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Re: Compression change from 208 psi to 250 psi
« Reply #2 on: August 27, 2016, 09:03:16 pm »
92 is the highest here at the pump. Guess I'll have to read plugs and re-adjust jets?
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owen
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Offline Gui961

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Re:
« Reply #3 on: August 28, 2016, 01:17:12 pm »
what is the actual compression ratio. 12:1 - 13:1. its on the limit for 91. but if you want a safety margin you could mix a little 110.  do not run pure 110 without very high compression.
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Offline crazycraftsman

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Re: Compression change from 208 psi to 250 psi
« Reply #4 on: August 28, 2016, 06:34:32 pm »
Haven't figured out the compression ratio but thought it was high at 250 a side. Got .150 shims on plugs to stop from hitting and .055 from valves. Sure I'm losing some do to dome top Pistons .
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Offline BIG AL 202

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Re: Compression change from 208 psi to 250 psi
« Reply #5 on: August 29, 2016, 08:35:22 am »
YOU CAN MIX TO GET WHAT YOU WANT, 50-50. THAT WILL RAISE THE OCTANE UP TO AROUND 98 OR SO.
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Offline crazycraftsman

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Re: Compression change from 208 psi to 250 psi
« Reply #6 on: August 29, 2016, 09:10:06 pm »
Thanks. I'll try the 50/50 and do the plug reading. One more race , then I'll pull heads off and figure out the compression ratio. ;)
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