Race Gas Required?

[risk74]

EC300 with new S3 cylinder and head. Black high compression insert, squish is as tight as I can get it without machining at 1.25 mm. The black insert is the only one that gets squish even in the ballpark with a thin base gasket. Kicking compression reads 165-170 PSI.

Have not run the motor yet, I am wondering if this set up will require race gas or a mix of pump and race? Previously I have run 93 octane pump on the stock EC with an RB head. Opinions? Thanks.

[Brian VT]

Should be fine on pump gas. Closer to 200 might want higher octane.
Your compression will probably increase with oil and break in so you should check it again then.

[Anders]

What octane is your pump gas?
I run my EC200 with machined head and compression on the high side with Norwegian 98 octane pump gas without any trouble.

[risk74]

The highest I can get at the pump is 10% ethanol 93 (R+M)/2. I have 100LL av gas available, I am thinking about trying that.

[webmaster]

Originally Posted by risk74

The highest I can get at the pump is 10% ethanol 93 (R+M)/2. I have 100LL av gas available, I am thinking about trying that.

You can find listings of stations that sell non-ethanol fuel here...

https://www.pure-gas.org

Mixing 50/50 pump fuel and 100LL av gas works very well - I like it better than straight av gas. There is enough lead in the 100LL to bump the octane in the unleaded part of the mix - so mixing the two works very well... And you cut the net amount of ethanol in half.

As a bit of history - back when unleaded regular hit the pumps - in the mid to late 70s - you could still buy leaded premium. If you mixed the two 50/50, there was enough lead in the premium to boost the octane in the unleaded half - enough so that the net octane of the 50/50 was higher than the premium by itself. As time went on - lead was reduced in the premium to the point where this no longer was effective. And then premium went unleaded as well...

In my experience, the ideal thing is to mix ethanol free premium with 100LL. Even mixing 20% 100LL and 80% ethanol free premium yields a very nice mix. e.g. put a gallon of 100LL in a five gallon can and top it off with pump premium.

jeff

[risk74]

Originally Posted by webmaster

You can find listings of stations that sell non-ethanol fuel here...

https://www.pure-gas.org

Mixing 50/50 pump fuel and 100LL av gas works very well - I like it better than straight av gas. There is enough lead in the 100LL to bump the octane in the unleaded part of the mix - so mixing the two works very well... And you cut the net amount of ethanol in half.

In my experience, the ideal thing is to mix ethanol free premium with 100LL. Even mixing 20% 100LL and 80% ethanol free premium yields a very nice mix. e.g. put a gallon of 100LL in a five gallon can and top it off with pump premium.

jeff

I've been waiting for years for someone in Richmond VA to sell non-ethanol fuel, still can't get it without travelling. I have an airport 7 miles from me that sells to the public, so I am going to get some av gas, I will take your suggestion and try blending it with pump and see how it goes. Thanks!

[webmaster]

Originally Posted by risk74

I've been waiting for years for someone in Richmond VA to sell non-ethanol fuel, still can't get it without travelling. I have an airport 7 miles from me that sells to the public, so I am going to get some av gas, I will take your suggestion and try blending it with pump and see how it goes. Thanks!

The other benefit of mixing is you don't have to re-jet for the av gas.... Av gas has a slightly different specific gravity than pump fuel.

jeff

[memphis2857]

I have been running the black insert on my last 2 bikes. On my 15, I got a little detonation with 93 octane. Lucky for me I have 110 available at the pump so made the switch with no problems.

I took the time to measure volume and do all the calculations and with the black insert the compression ratio was about 13.9:1, that’s right on the edge of needing race gas.


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