Quote:
Originally Posted by bfrank1972
I was under the impression the OTS stage 1 tune was actually optimized for 91, not 93. Might actually be able to squeeze a little more out of 94 fuel.
Also regarding the OTS E85 tune, is there room for more timing advance for true E85? @ shiv@vishnu says anything greater than E60 is fine, just wondering if he built in a large safety margin or if its that you just can't benefit from any further timing advance.
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Hi,
If you have a look at the release notes for the tunes its says petrol tunes optimized for 93 AKI (american) fuel so the tune will run its maximum advance on 93, hence running 94 or higher octane will not get you any more power.
Octane is a rating of the fuel's resistance to knock/detonation not a measure of the energy content of the fuel.
E85 has a greater octane rating than straight petrol but actually less energy value per liter due the ethanol content hence you have to use more to produce the same energy at petrol. so fuel economy is less. aprox 25-30%
However you can run much more ignition advance due to the higher octane rating and I believe it burns cooler than petrol.
Shiv said somewhere that even E60 has enough octane rating to run the full advance with no knock and that that was about as much octane as a N/A motor with 12.5/1 compression needed. different if its boosted as effective compression ratio increases under boost and better octane rating needed. So for N/A it would appear it already running close to the max timing possible for this motor and nothing much left to improve.
His tunes adjust fueling using ltft to account for the different fuel density's between the range of E60 to E90 but the timing remains the same. ( (@jamesm blood pressure rising already)
Although with a true flex fuel kit (sensors wired into ECU) you could probably reduce safety margins and get better fueling compensation so I would imagine you could squeeze a bit more out of it.
Note I am not a tuner just done a bit of reading
anyhow shiv beat me :-)