Has anyone used the E85 OTS Map on MHD for the supra?

[WhiteNissan300zx]

Just realized I had this map show up after I started the car up after a month. I thought full E85 cannot be used unless you have a LPFP and PI. Thanks.

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[Thraxbert]

A full e85 map on the stock fueling will probably use less boost and less engine timing to keep the fuel trims accurate. I would not be surprised if an E60 tune was more powerful as the sweet spot of ethanol v. timing v. boost.

It's not that the car can't pump full e85. It's that the pump can only flow so many gallons per hour, and if your boost/timing situation demands more than that, the pump cannot keep up with the requisite quantity of fuel. But if you make the turbo and engine more conservative, less fuel is demanded.

Every ~25% ethanol you add into the fuel raises the fuel pump flow rate requirements by 10%. That's where the problem is with full E85. The engine is asking for 30% more fuel to keep up with the air quantity from the turbo, and the pump can't flow any more.

E60 ends up being the sweet spot because you can push the stock turbo to its max performance (22-24 PSI) and the fuel system can still keep up.

//Edit: just to help visualize what I'm talking about, here's a made up chart that illustrates the issue. As you add more ethanol, the PSI (air volume) needs to come down so the fuel pump can keep up and keep the air/fuel balance correct. You can run full E85, but you need to give up boost. Exactly how much kinda depends on intake and ambient air temps.

 

[Twisted Tuning]

Just realized I had this map show up after I started the car up after a month. I thought full E85 cannot be used unless you have a LPFP and PI. Thanks.

As stated above, E85 has always been able to be used. It's just that as stated max power usually isn't achieved with it due to HPFP limits.

For someone who wants the convenience of not mixing and is ok with not having the absolute max power full e85 is fine. And will still be a fun car.

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