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  #1  
Old 30th August 2017
thecarfarmer's Avatar
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Default I'm almost afraid to ask this...

...because I can see how this thread could devolve into a ��storm of "why would ya' wanna' do that - you'll go fast enough on pump gas" comments.

So, I'm going to ask for guys who've got first hand experience: on Evo Sportys, what kind of gains can be had on a hot bracket engine by going from 10.5 or 11.0 CR and pump gas to Max CR (basically, whatever dome you can stuff in the chamber) and real race gas?

Got to be some guys here who 'been there and done that'.

TIA,

William

Last edited by thecarfarmer; 30th August 2017 at 07:09.. Reason: fawkin phone auto-correcting stuff it oughta leave alone
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  #2  
Old 30th August 2017
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How about mid nines? Get Ya some head work and some oxygenated fuel.

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  #3  
Old 30th August 2017
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On my 10.5:1 bike MS109 is a consistent 5-6 mph faster in the 1/4 than 93 Octane.


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  #4  
Old 31st August 2017
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Default

IME, these things don't like compression, they love it. The more the better. Seems to help get the bike moving.
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  #5  
Old 31st August 2017
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Default

These things are also very hard to make compression (cylinder pressure) with.
When you get into big valves you also get big chambers.
At that point reverse dome pistons like those 10.5-1's just wont work any longer
I have 1.98 intakes in 80CC Chambers with .400 full dome pistons that are front and rear,meaning the exhaust valve pockets are much smaller and my numbers say the engine is 11.81-1 compression.
The Hot Street guys claiming 14-1 compression dont have pistons or heads anything like mine which is a grocery getter motor compared to they're engines.
Just dont Kid yourself what its gonna take to really haul ass.
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  #6  
Old 31st August 2017
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Octane in and of itself simply inhibits Detonation [lights hard, burns a bit slower]
Does your engine need that?
Having been sponsored by 2 Different Fuel companies,and close enough to a 3rd...
I only use the Fuel I need.. On a Stock engine. or somewhat. the Unleaded [really unleaded, with No Alcohol] fuel is probably the very Best!!!
If you don't "pop lean" or encounter Detonation, out on the track...you can only go Slower by inhibiting "Burn".
Switching from 114 to 118 [on a whim] slowed us Down..
Fact
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Old 1st September 2017
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Oh
As Stated above...Compression is King..
11's to low 10's just with Compression and Timing!!!
Definitely required a fuel change.. The Proper Fuel
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  #8  
Old 2nd September 2017
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Quote:
Originally Posted by jcro61 View Post
On my 10.5:1 bike MS109 is a consistent 5-6 mph faster in the 1/4 than 93 Octane.


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That's a lot of performance!

BTW, I wonder what that difference would be throughout the year as the formulation of the pump gas was adjusted for the seasons...
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  #9  
Old 2nd September 2017
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Slower burning!!! Timing is the key with high compression engine with cams that can fill the chamber full. Combustion engine work with the expansion of the flame. You can built a high compression motor that run on regular gaz but It will be so hard to control timing and AFR, even on EFI, you'll choose racing gas; just easier to manage. The downside of racing gas is the price; That why HC bikes get trailered at the track.
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Old 2nd September 2017
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Quote:
Originally Posted by jcro61 View Post
On my 10.5:1 bike MS109 is a consistent 5-6 mph faster in the 1/4 than 93 Octane.


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I have Not found this.. Only maybe on inefficient combustion chambers, Think IronHead!

Quote:
Originally Posted by thecarfarmer View Post
That's a lot of performance!

BTW, I wonder what that difference would be throughout the year as the formulation of the pump gas was adjusted for the seasons...
We Have both offroad gas, and Non-alcohol gas available where I am..
Makes a Big difference, especially as regards seasonal "formulation" changes.
I hate Alcohol.../it is the root of the Tuning and Performance Problems..
Unless you use 100% I guess!!!
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