[dreksnot]

If I add a flex fuel sensor on my stock LT4 and tune, can I run full E85 or will I be limited to something lower, like E60 or lower?

[D3adch1ld]

Only a mix, you'll have to tune to see where you land. Likely need a low side aux pump too.

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[arpad_m]

No, your stock LT4 fuel system is inadequate for E85. As D3adch1ld implied, you need to monitor your fuel pressures and see what ethanol percentage your low side starts dropping off, then cut back a bit of the E to have a safety margin.

If you don't want to go through these iterations, professional tuners who do this every day will be able to look at your setup and know off the cuff approximately what your E limit is.

Just as a data point, I have the LT4 fuel system (low side, high side, injectors), +32% fuel lobe cam plus a JMS low side voltage booster, and I can do E60 on a regular basis at ~10-11 psi of boost with my Magnuson 2300 supercharger. I may get away with E65 for a pull, but I don't want to risk it longer term.

The good thing is that performance gains taper off hard beyond E60-65, so you aren't gaining much beyond that. Going with a mix instead of straight E85 also helps a bit with fuel economy, because the engine will gobble up that ethanol like there's no tomorrow.

[Joshinator99]

Originally Posted by D3adch1ld

Only a mix, you'll have to tune to see where you land. Likely need a low side aux pump too.

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Agreed. As stated many times before: low side goes out first followed closely by HPFP (w/stock cam lobe) then injectors. JMS voltage booster can extend the low side for a bit. Best bet is to get a real in tank fuel system sooner than later so you have a rock solid foundation going forward. DSX aux is a bad deal, but DSX & Katech in-tank systems are great. Fore Triple if you want big power for drag and/or roll racing.

[WiggyB]

Originally Posted by dreksnot

If I add a flex fuel sensor on my stock LT4 and tune, can I run full E85 or will I be limited to something lower, like E60 or lower?

Before I did the port and jms bap I was on e50 with the full LT4 fuel system.

[KingLT1]

Actual 85% ethanol NO. But most pumps do not have Full E85. Most pumps are E65-78. Being a LT4 car, You "might" be able to do E70 with a JMS and no other mods. There is no need for anything above 60% on a stock car anyway. Just do a 60/40 mix of E/Pump and call it good.

[SOCAL.M6.ZLE]

Originally Posted by KingLT1

Actual 85% ethanol NO. But most pumps do not have Full E85. Most pumps are E65-78. Being a LT4 car, You "might" be able to do E70 with a JMS and no other mods. There is no need for anything above 60% on a stock car anyway. Just do a 60/40 mix of E/Pump and call it good.

[dreksnot]

Thanks, all. I was hopeful in thinking I could get a teaser before going all-in just by installing the flex fuel sensor and tune. Might as well wait until doing the "package" in full. Do plan to do DSX in-tank, port injection, FF sensor, bigger air-pump, headers and settle for around 800rwhp.

[Megahurtz]

E60 is as far as you will get even bone stock. Can you push E70? yeah but you will drop pressure and actually lose power.