Evo 2T Gas

[wayneniner]

not sure this warrants a new topic..but here goes:

 

Do I need to run race gas in 14,15,16 Evo 2T (250 or 300)?

 

In my 07 Rev 3, I need to run at least 1:1 race gas(110)/premium(91) or I will get the knocking after the motor gets hot...lately I've been running 2 parts race gas to 1 part premium-no problems. (70:1 oil FYI)

 

I am thinking of upgrading to a newer Evo(14,15,16) and wondering if the newer bikes still need race gas?  I would like to use premium only..race gas around here costs around $12/gallon.

 

Bonus Questions:

 

also, out of the 14,15,16 years of the Evo 2T 300(or 250), is there a year I should avoid or go for?  

 

Do the Evos(14,15,16) still have the magnesium side case that corrodes?

 

I am guessing the stator issues that I've read about the Rev3 having has been fixed with the newer Evos?

 

 

 

 

[heffergm]

I never did. Ran fine on premium pump gas. The GasGas is a different story.

[dan williams]

Race gas has a couple of advantages over pump fuel. First is consistency. Pump gas, even from the same pump can be highly variable. Second is race gas usually has no alcohol in it. This means less water absorption which tends to displace the oil in premix but also no waxy build up in the fuel system as the alcohol breaks down.

As for the octane needed to prevent pre-ignition that is solely dependent on the compression ratio. There will be an optimum mixture for a certain compression and ignition timing and bikes with similar compression ratios will have similar octane requirements. You can reduce that requirement with an accessory chamber from S3 as I did on my '13 EVO. I still run race gas though because I like the bike to run consistent a I'd prefer to disassemble and clean the carb less than I have to with pump gas. As for years of EVO I ride with guys that have an '11, '13, '14 factory and a '15 factory. They all have slight differences but are pretty similar in form and function. Biggest difference is in how the bikes have been treated. Beat bikes will have more issues than Sr ridden bikes.

Edited March 27, 2016 by dan williams

[lineaway]

A properly jetted Rev 3 will not knock.

[dan williams]

An optimally jetted engine of a specific compression ratio requires a certain octane fuel. You can jet rich to add additional cooling from fuel evaporation and reduce chamber pressure slowing the flame front from non-ideal stoichiometric ratio. You can also delay the ignition timing which reduces peak pressure and temperature. Both result in reduced power output.

So yes a Rev 3 can be jetted to run on pump gas without knocking. But an optimally jetted Rev3 with stock compression near sea level will run best with a higher octane.

There are many variables though as pump gas can vary widely. Carbon buildup can increase compression. Worn rings can lower compression. Variation in base gasket and head gasket thickness and machining tolerances change compression. Each engine is unique. But in thirty years of riding Betas I've seen many bikes pinging on pump gas.

[dadof2]

A properly jetted Rev 3 will not knock.

 

Unfortunately no longer true. Some of the crap being sold as fuel round here now makes anything knock and even brings engine management light on in cars. Switch to BP or better still BP ultimate and the knock disappears and performance improves.