fuel myth

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fuel myth

Postby yelnats » Sun Feb 27, 2022 5:49 pm

my 04 liberty sedan h6 engine recommends premium fuel so is that 95 or 98 octane fuel that it is tuned too or both?
im aware i should go to e85 fuel though once raptor supercharger is fitted for some more bang , does that only involve a re tuning of computer or is there other things to be done to run on e85 ? or can i run on e85 fuel now as its cheaper or not a good idea?
i read somewhere to mix your fuel at the bowser with say half e85 and half tank of say 91 unleaded to create a better fuel ratio mixture or mixing 98 instead with e85 obviously would be betterer yer or na ?? cheers specimens
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Re: fuel myth

Postby Yowie » Sun Feb 27, 2022 6:02 pm

Welcome.

Others can reply Re whether a H6 needs 98 octane. Even if 95 is ok in it, I would run 98 if I owned one.

Don't muck around with E85 (blends or "neat") unless the car is set up for it. At minimum this will be a tune to suit, but could involve bigger injectors, replacement fuel lines, bigger fuel pump, etc.

E85 (being 85% ethanol) contains fewer calories of energy per litre than petrol. As such a greater volume of liquid needs to be injected under most/all running conditions. If your factory computer isn't set up for E85 it will inject a "petrol quantity" of fuel, the car will run lean, knock will probably occur under load (despite the anti-detonation quality of the fuel) and engine damage may result.

Also, if the ECU isn't set up for E85 it won't know to advance the ignition for more power, so the fuel-blending or wrong-fuel-adding exercise is probably pointless from a "more power" point of view. When my turbo forester was tuned for correct E85 fuel volume but NOT ignition timing it made no extra power (I had the car for a few days between tune stages).

If you or a mate try it anyway, get lucky & prove my predictions wrong - well done, but you will be gambling with that engine.

Best wishes for the exciting journey of learning more about your car & power-adding. We all have to start somewhere.
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Re: fuel myth

Postby bigBADbenny » Mon Feb 28, 2022 9:02 pm

As stock the h6 is prone to octane/timing related knock and as such may not hold iam/dam 1.00…

So 98 at a minimum is essential if not tune/detune.

The rough idea that the timing is a little too optimistic in the stock tune eg more suited to jdm 100 octane.

Generally e85 ,tuned for, can make more power, but with around 30% more fuel used.

On the fuel supply side, the ethanol solvent action can clog fuel filters and other fuel system components so you may want to discuss the fuel type transition from 98 to e85 with regard to the tune type, eg tune or detune, plus when to upgrade the pump/s, jet pump and injectors and especially the fuel filter.

On the combustion side of e85, the water content released during combustion has a cleaning effect on the cylinders and valves, a primary side effect being contamination of the engine oil with water.

In turn, this requires longer driving stints and more regular oil checks and changes.

If you want to start adding small quantities of e85 to your fuel, logging & learning view analysis will quickly reveal the effects and how severe they are.

Just be aware that the ecu will probably ask for more fuel, your fuel system may get clogged, your oil may get water in it.

You may require aos cc, as the water in the sump makes oil/water blowby vapor, aka snot.

I’d consider it just to clean the internals as well as the opportunity to detune the car somewhat so it’s got headroom but still be drivable.
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