Author Topic: Max Compression Ratio on 93 Octane?  (Read 5335 times)

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Offline DeereRacer

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Max Compression Ratio on 93 Octane?
« on: January 09, 2015, 12:11:00 pm »
I am building a 44 Intek with some used Ryker heads with an unknown amount of milling.  The previous owner of the heads ran 108 octane on a 40ci. He claimed it did not run right on premium gas. There was no mention of knocking or pre detonation but if it did knock it should have snapped his stock 40 rods like a twig.  I would like to run 93 octane because I am cheap and believe when the rules say pump gas they mean everyday regular premium not race gas.  So how much compression can I run on 93 and was the previous owners problems with it just a matter of tuning? 
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Offline Darkviper

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Re: Max Compression Ratio on 93 Octane?
« Reply #1 on: January 09, 2015, 05:16:12 pm »
On my gx440  it said anything over 10 to 1 should run on race fuel. 15dollars on race fuel last me and my buddy a hole day.
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Offline cycloneracer

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Re: Max Compression Ratio on 93 Octane?
« Reply #2 on: January 09, 2015, 09:32:28 pm »
Id run race fuel just for the safety.   It will probably perform better on regular but you run the risk of detonation. 

Race gas is USLMRA legal as long as it comes out of a regular gas pump.  No oxygenated fuel or VP.   Sunoco is sold at the pump.  There may be others but Sunoco is probably the most common.    There are several grades available. 
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Offline DeereRacer

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Re: Max Compression Ratio on 93 Octane?
« Reply #3 on: January 09, 2015, 11:51:10 pm »
That pump gas rule is pretty vague. I am sure if you looked hard enough any fuel you wanted could be found at a pump.  Why don't they just list what isn't legal to burn? 
I don't want to drive 40min just for a few gallons of race gas that will get old by the time I use it all. I will have to measure the chamber size and see if I am anyware near 10 to 1.
"There are three easy ways of losing money - racing is the quickest, women the most pleasant, and farming the most certain."

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Offline cycloneracer

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Re: Max Compression Ratio on 93 Octane?
« Reply #4 on: January 09, 2015, 11:58:51 pm »
I have a 15 gallon barrel I fill.  As long as it isn't exposed to sun light and sealed it will keep a long time. 

Get an EGT.  That will help you with fuel selection. 
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Offline Darkviper

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Re: Max Compression Ratio on 93 Octane?
« Reply #5 on: January 10, 2015, 03:51:09 am »
I just run 110 race fuel from Speedway gas station.
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Offline slonomo

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Re: Max Compression Ratio on 93 Octane?
« Reply #6 on: January 16, 2015, 11:53:28 am »
You can use high octane, but you may not hear or notice any detonation.  This is why most will just use race fuel, no guesswork then.  There is a website I saw somewhere here where you can type in your zip code and it will tell you locations of race fuel and/or ethanol free fuel stations.  Anyone know that website? 
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Re: Max Compression Ratio on 93 Octane?
« Reply #7 on: January 16, 2015, 12:25:33 pm »
I run 87 octane in my Indians anyone can tell ya they aint lacking on HP. Go figure. I use to mix it 50/50 with race fuel 110 just for the smell. Was not about performance. For performance you want to run as low an octane and you can possibly run with out predetonation. Ign.,Timing, cams, carbs, and compression  all play a big role in it.
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Offline mcollins

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Re: Max Compression Ratio on 93 Octane?
« Reply #8 on: January 16, 2015, 05:33:12 pm »
Id run race fuel just for the safety.   It will probably perform better on regular but you run the risk of detonation. 

Race gas is USLMRA legal as long as it comes out of a regular gas pump.  No oxygenated fuel or VP.   Sunoco is sold at the pump.  There may be others but Sunoco is probably the most common.    There are several grades available. 
the rules say you can run VP race fuel if you buy it from a pump station.
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Re: Max Compression Ratio on 93 Octane?
« Reply #9 on: January 16, 2015, 05:55:55 pm »
Up here VP only comes in a can.   

But yes if you can pull your car up and fill it your good to go!!!
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Offline mcollins

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Re: Max Compression Ratio on 93 Octane?
« Reply #10 on: January 16, 2015, 06:27:47 pm »
Where I go they "pump" it out of a 55 gal drum into my can, its going to be hard to tech this
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