dubious
Needs a life
Needs more time to ride!
Posts: 8442
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posted June 03, 2009 09:52 AM
From my experience with 2 strokes, which have cooler surface head temps and no hot exhaust valves in the combustion chamber to induce detonation, I have had to run 103+ octane at 15:1 compression....
I am not implying I know better than anyone else here, just my own experience...
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natural selection.....
destiny will overcome intervention.
Some are not worthy of the effort.
  
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dougmeyer
Needs a job
moderated
Posts: 2713
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posted June 03, 2009 06:19 PM
Why not C 25??? If I remember correctly, that is the spec fuel for NHRA Prostock- and that's pretty much what we've got here. C-44 is a unknown to me. C-25 is very predictable and stable.
Tim,
I didn't say LEAVE it rich, just find out where the F rich is.... I'm not trusting the data.
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It's not that I think you're dumb, it's just that so much of what you know isn't true....
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tcchin
Zone Head
Posts: 867
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posted June 03, 2009 07:23 PM
Aw, that's no fun! I like my bikes to be a reflection of myself, so fat and slow works out perfectly.
I trust AFR very little as a tuning aid, and trust the AFR measurement devices even less.
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2000redrocket
Pro
Posts: 1662
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posted June 04, 2009 10:26 AM
can i ask what kind of cranking compression u get at 15 to 1 on your bike ent?that to me is a good bit for 98.
doug what is c25 rated at?
when i go with my 1270 i think suspose to be around 13 to 1 or so will pump gas 92 or 93 be ok? this is good stuff. i know my fired engine guy was not happy with me running 100 sunoco in my car at 265deg@.050 in my 440 said 110 or 112. but it seams a bike needs less octane compaired to equal compression in a old skool car chamber. what do you guys think?
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VincentHill
Needs a life
Posts: 6520
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posted June 04, 2009 01:23 PM
Karl, what does the Underside of the Piston look like? is it carbon Flaking or still have a little shine in it! If I saw a little shine then I would clean up the top and continue with Dr. Doug Rich if it is dull and a little flaking I would consider more Pistons because the metal structure had started to fail!
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Made History @ Daytona and still one fast old man!!
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KZScott
Needs a life
high on speed
Posts: 7235
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posted June 04, 2009 03:39 PM
quote:
when i go with my 1270 i think suspose to be around 13 to 1 or so will pump gas 92 or 93 be ok? this is good stuff. i know my fired engine guy was not happy with me running 100 sunoco in my car at 265deg@.050 in my 440 said 110 or 112. but it seams a bike needs less octane compaired to equal compression in a old skool car chamber. what do you guys think?
from the mixing fuels thread:
quote:
last season. 13.5:1 cr (measured), 86mm bore, 87 octane, 5 degrees advanced. ran that way one wknd at the track with no problems. it was even running lean(13.6:1 afr) by mistake (5 degrees was a mistake too, it was supposed to be 3) pistons/combustion chambers were prepped for nitrous so that probly helped a lot.
i ran all my nitrous passes on 91 octane
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01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
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dougmeyer
Needs a job
moderated
Posts: 2713
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posted June 04, 2009 06:50 PM
Pent-roof four valve chambers can handle much higher compression without serious detonation. This is because of the nice squish areas and good flame front control. Compression / octane combos that work in a center plug four valve would turn a Chevy or Mopar wedge into Three Mile Island. Old Hemi's are even worse, there's almost no squish and nothing to control flame front. The twin plugs help a lot, though. (The new ones aren't true hemi's and are pretty good).
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It's not that I think you're dumb, it's just that so much of what you know isn't true....
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2000redrocket
Pro
Posts: 1662
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posted June 04, 2009 07:22 PM
thanks doug. i listened to you and have a strong 12 i'll not worry on the 1270 using expensive gas just good quality non ethonal 93.(can still get it in pa)
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psycho1122
Pro
Posts: 1608
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posted June 06, 2009 06:35 AM
On my 14:1 CR 1270, I run 12:8-1 A/F with 91 octane (NO LEANER!). No base gasket get's me .028-.030 piston to head (Quench).
Piston prep to remove all sharp edges on pistons helps keep things happy.
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You say PSYCHO like it's a BAD thing!!
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KSPZ3
Expert Class
Posts: 334
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posted June 09, 2009 07:19 PM
And twice the cost of mr9 if i remember correctly...OUCH!
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