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Ethanol Blends vs Race Gasoline

Flex Fuel Tuning

Discussion and questions related to the course Flex Fuel Tuning


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Hello all,

I understand the benefits of tuning with E-blends of fuel vs straight pump gasoline. However, it is not mentioned in the course how, say, E85 fares against gasoline of the same octane rating.

The way the topic is explained by Andre in the course, there seems to be no real benefit to go through the trouble and expense of upgrading a fuel system is E85 is not available at the pump and costs about the same as a high-octane fuel. (in my case, a 5-gallon pail of C85 VP costs around 80$usd whereas the same amount of C16 costs just 20$ more)

In a car that isn't a race-dedicated vehicle, is there no benefit to using ethanol fuels vs high-octane gasoline?

In the past I have read that due to the increase fuel mass required to achieve a given power level when compared to gasoline (93AKI or 116AKI regardless), ethanol decreases spool time on a turbo charged vehicle and that increased fuel mass is also what provides the increase in power over gasoline.

I've personally done some back to back testing between VP Q16 and E85 on a 600 kW high boost 4G63 and the results were almost identical so there isn't necessarily a power advantage by switching to E85 The advantages normally come from the cost saving of pump E85 however if you only have access to E85 from a race fuel supplier then it might not be as appealing. Some race classes however won't allow the higher octane race fuels that contain lead so there are some considerations depending on what you want to do.

E85 does run cooler than a gasoline based race fuel for a given power level so this can also be beneficial to engine reliability in some cases.

John Reed and I did back to back testing with MS109E and E85 awhile back when I first put flex fuel in the rally car. Just corrected for fuel, we had a gain of 23 hp in the mid range and 8-9hp up top using E85. We both looked at each other a little stunned. Motor was an EJ257 and from what I've seen, they love E85.

I get my E85 from Thunderbolt Fuels by the drum in Oregon for much cheaper than MS109E. It's made from apple waste product so smells way better than corn too. They can also do whatever blend you'd like.

One big thing to consider is if there is a lambda (oxygen) sensor being used - C16 is a leaded fuel, as Andre mentioned, and that is going to contaminate the sensor. Estimates of how long it will take vary, and it may start giving a richer reading as it fails.

There are many different 'race' fuel blends, here is a link to the VP data sheet https://vpracingfuels.com/master-fuel-tables/

Note, C16 is the base fuel, Q16 is oxygenated and said to be worth around 4% more power - it's also rather more expensive.