e30 vs e40 (or higher)

[GoMax]

I've noticed that many members have e30 tunes, and was wondering what was the limiting factor in how far up the eXX scale to go.
I know that our fuel system isn't designed for e85, so is e30 the magic level? e40?

Other than following on the successful heels of others, is there a clear reason to use e30 over e40?

Many thanks!

-- Max

 

[twolf]

I don't feel much difference between e30 and e40 so I just run e30.

 

[Rhinopolis]

I asked this question in a separate thread and never received a reply that answered my question, so I take the forum silence to mean that not too many people know the answer. This includes myself btw......

The higher up the ethanol content scale we go the higher the octane, and also the greater the evaporation rate since ethanol evaporates more quickly than gas.

I have the E30 tune file from the tuner that I work with, and I am installing my TTR engine mounts this coming Monday and will then datalog the car for a Virtual Dyno comparo of the results both before and after E30. I am going to share those results on a thread that already exist where someone asked to see those.

The tuner that I work with says that his tune file is fine to run between E30-E40, and my goal is to factor in a margin of error for safety with E35. I have an ethanol tester, and I am going to gauge the ethanol content at my local E85 pump before each fill and then mix with "up to 10% ethanol" 93 octane Chevron until it's at my best estimate of E35.

 

[rodmoe]

Beyond E50ish tunes I am told there isnt much to be gained other than going Full E85 for ease of filling the tank with no mixing. The Low Pressure Fuel Pump runs out of pumping ability (for lack of a better word here) to supply fuel to the injectors Also to supply enough fuel to the engine at the higher Emixture tunes you need to add a Aux Fueling system as the Hi pressure fuel pump can not keep up alone. So the limits seem to be E40 and E60ish do to mechanical limits of the fuel system and since there is no big gain from E50 on up as of yet it isnot worth the effort . But I am sure someone will figure out a way to upgrade the fuel system at some point. or at least i hope..

 

[Wimp Lo]

As the ethanol percentage goes up, octane goes up and energy density goes down which requires more fuel.

With higher octane fuel, boost can go up (if your turbo can handle it) which requires more fuel.

With a stock turbo, boost is limited because it is too small. With limited boost, there is only so much octane you need to get optimum ignition advance and power. After you get to a certain point adding more ethanol won't help.

With a "big turbo", there is a sweet spot of octane, energy density and boost level that produces maximum horsepower with the stock fuel system.

With a big turbo and aux fuel you can get a bit more before the in tank fuel pump runs out of volume.

Its a juggling act and E30 usually works well.