E85 vs water-meth injection

[Desperado]

Where I'm at. 13t's on temp hiatus, so 9b's it is. As it is I can only get 91 oct as the highest grade of gas I can get other than the e85. So as you can imagine I'm worried about detonation with the 91. On 91 what would be a safe boost psi range without injection and is there one? Or just go e85 and not worry about it.

To me pros water injection
1 not bad for engine
2 cost starting about 400
3 water and rub alcohol cheap
4 higher boost
5 basic simple setup

Cons
1 always having to maintain extra fluids
2 still buying exspensive gas

Pros for e85
1 not bad for engine
2 cheap
3 no worries about reasonable boosting

Cons
1 buying another set of injectors, new fuel pump, fuel filter, and not bad but buying flash ecu for mapping
2 not available everywhere
3 bad mileage
4 no worries about over boosting

[KeithMac]

Personally for 9b's on E85 I would run a SAFC, 550 injectors and a walbro 255. It will be a different car!.

I would always go E85 if it's readily available where you live, it's like race fuel at the pumps.

[sergechronos]

Agree with Keith.

When you upgrade to 13Ts you'll probably need to step up to 680 or 720 injectors and a better AF control system. Flash ECU or AEM would be the best way to go about that, but an ARC2 or MAFT MIGHT be able to adjust for injectors of that size. Once the Flash ECU has the switchable maps option, there likely wouldn't be much reason to do meth injection if you have E85 available nearby. Your pros and cons list is a good start but is missing some concerns:

Water meth is still going to require bigger fuel pump and injectors and an AF controller, you can't just throw water meth in and go with 13Ts. Personally, I would also want some kind of progressive system and a way to monitor to in case the pump fails or the nozzle(s) get clogged.

E85 doesn't necessarily require a new filter as many people have and are currently running it through the factory fuel filter. So you'd need bigger fuel pump, injectors and an AF controller just like with meth injection. It does different torque characteristics than pump or pump+meth. Pending when you're looking to make the switch, the Flash ECU will have switchable maps in one of the next updates (no timetable for when that will be though) which would negate the E85 not being everywhere and the bad mileage concerns. The tune with E85 could be a concern as you can't use the knock sensor to tune, and requires your tuner to know how to do E85 tuning so he doesn't mess things up.

Best thing to do is break down the cost of E85 near you versus 91 octane near you and how much meth you would go through (plus the cost of the water+meth.) Finding out from people with similar builds will point you in the general area as to what to expect from both in terms of consumption/mileage. Figure out cost per mile and then decide whether or not it's enough to justify doing it. As an example, E85 is 2.89 a gallon here and 93 octane is 3.50 a gallon here. E85 will get about 25-30% less mileage, so just adjusting for that, E85 really costs between 3.61 to 3.75 a gallon. So based on that, water+meth would have to cost less than .25 a gallon to make things equal. Then consider the other factors to each: How hard is it to tune? How does it change torque/hp? Added cost for other things to run each fuel?

I decided to go E85 as I have E85 stations near me, and I can switch back to a pump tune whenever I want for fuel economy or availability concerns even without the switchable maps in Flash ECU.

[kywhitelightning]

This makes very little sense to me. 9b's are a factory turbo and will run out up top to boost pressures that pump alone can handle. The spikes they can create is the only thing to be concerned with. Set the boost controller correctly to near 12-13psi and buy nothing else and enjoy. If that is the issue then put the factory BC back on it and enjoy the car the way the factory intended it as 91 is still considered premium fuel.

Once the 13t's are on, look to upgrade things. Once they are on a meth kit using methanol is the only way I would go. Run enough meth in there and you won't need to upgrade any of your factory fuel components. If you are terribly concerned with meth running low or out, pony up for a flash ecu and turn the cel on after knock exceeds your allowable threshold. Pull out when the light illuminates.

Jeff

[Desperado]

The sad part is after I found out what getting both of my 9bs rebuilt I could have almost purchased 2 new 13T chra's with billet wheels.