rb20det e85 questions

[rbS10]

I want to build an RB20 for a special project of mine, and I am looking for around 400rwhp. I live in the upper midwest, so E85 is cheap and plentiful. Im going to run a Holset HX35 turbo. I know that running e85 requires a significant amount more fuel than regular pump gas. So what I need to know is just how much more, and what size injectors, fuel pump, etc. to use in order to get to my power goal. Also, what differences does it make in the amount of power and boost and stuff the engine can take before it kerplodes? Im a moderate noob when it comes to turbos. Thanks

[Ken@PTUNING]

I want to build an RB20 for a special project of mine, and I am looking for around 400rwhp. I live in the upper midwest, so E85 is cheap and plentiful. Im going to run a Holset HX35 turbo. I know that running e85 requires a significant amount more fuel than regular pump gas. So what I need to know is just how much more, and what size injectors, fuel pump, etc. to use in order to get to my power goal. Also, what differences does it make in the amount of power and boost and stuff the engine can take before it kerplodes? Im a moderate noob when it comes to turbos. Thanks

E85 requires 46% more fuel compared to gasoline. The main benefits are that the fuel has an effective octane rating between 100-105, burns slower, and runs cooler. All this means that you're able to run more ignition timing for a given level of boost, run leaner AFR's safely with a much lower chance of detonation. The limiting factor is what power you're likely to bend rods since we're not likely to be knock limited (and I'm assuming you're tuning this properly).

As far as parts, I'd get a set of injectors no smaller than 750cc. At your target power level, you should be right around 80% duty cycle with that size and 43psi of fuel pressure. Pick up Walbro's E85 specific 450LPH pump and you should be good to go fuel wise. I'd also recommend you set up your standalone (you are tuning this with a standalone, right?) to use a flex fuel sensor as well. I have never been to an E85 station where I received actual E85. It always comes up E65-E75. This is because companies are required to premix ethanol with gasoline before being shipped out. Since gas stations mix at the pump, you're actually mixing something like E9X with E00-E10.

[RRRRB]

46% seems a little on the high side, from my experience its between 30-40%

Never heard of stations mixing at the pump... the station near my house has been 85% everytime for the last 2 years ive been filling there... I test manually and verify through my Ethanol sensor

Power increases very from setup to setup but expecting 2-7% increase at same boost level is fairly normal with tuning.

400whp shouldnt be an issue, you will be limited by the RB20's factory internals.

[Ken@PTUNING]

I'd agree that 35-40% is more realistic. It all depends on what regular gas really is and what the engine wants.

Stations mix all the time. They do it with all the octanes between regular or premium. They mix 87 with 91 (or 93 if that's premium) to get 89 for example. If you're actually getting E85, you're lucky. We have two stations here in Northern VA and it's never been higher than E75. Sometimes it's as bad as E65.

2-7% is the power increase just from switching to ethanol. Ethanol per liter has less energy than gasoline BUT you use more of it per cycle since stoich for E85 is 9.85. Plus, of course some fine tweacking to the timing map because of the slower burn rate helps too. In my experience though, when switching to E85 in a knock limited FI engine, the gains can be much higher. For example, we were running 10psi from a GTX2867 making 320whp. The only reason we didn't turn up the boost as there was no combination of fuel and timing to give us a reasonable power increase without some kind of fine knock. We pumped it full of E85, turned up the boost and maxed out the turbo at 400whp. We did the same thing with a GTX3076, which made 330whp at 10psi (slightly more efficient). Once again, converting to E85 (E70 actually during that tuning session) and made it to 500whp before maxing out the turbo. Ethanol is wonderful for turbo cars! Just make sure you're not going to throw a rod (which you shouldn't at 400whp).

[rbS10]

Thanks a ton, guys.

Would a standalone be required for e85? I will shell out for it if I have to, but I dont have super deep pockets.

[Ken@PTUNING]

Required? No. Highly recommended? Yes.

Regardless, you'll need some way to tune for the additional fuel requirements. Nistune at least does offer flex fuel support if you're looking to keep costs down. A true standalone will also allow you to take full advantage of flex fuel with things like boost by ethanol content. I personally wouldn't try and run E85 on just a piggyback.

[rbS10]

Okay. Do you have any standalones you would personally recommend? Something that would work but isnt top-of-the-line-expensive

[Ken@PTUNING]

Personally, I run a Megasquirt MS3X. It's cheap but oriented towards DIY with a steep learning curve but is extremely capable (I've tuned AEM, Haltech, Nistune, and Hondata for reference). If you plan to tune it yourself, this is the route I'd go.

Honestly, you're probably going to have someone else tune it. You want to consult your local tuner to his/her preferences for tuning. The last thing you want is to drop a standalone a tuner is unfamiliar with and tell them to have at it.