I was surprised to find out how many mods I could do without tuning my car. I know it is recommended a lot, particularly to realize the full potential of what you're putting in, but I wonder if there are any mods that I HAVE to tune the car after to avoid damage risks?

One specific change I was wonder is if I switch to E85? I only ask because I read in the owners manual that the car can take Ethanol as long as the octane rating is higher than the recommended 93. It doesn't say anything about tuning.

 

I hope you put your flamesuit on. The Evo must be tuned for E-85. E-85 is not an easy switch it is absolutely required that you change the fuel pump, fuel injectors, and tune the Evo. Installing a Wideband is also an optional mod that adds a sense of security. The stock tune cannot compensate for the extra octane.

When I refer to tuning the Evo the best option would be to take it to a reputable Evo shop in the area that has a physical dyno.

 

Things requiring a tune:

Cams. Turbo. Injectors. E85.

The manual says the car can handle a small percentage of ethanol because a lot of gasoline these days is E10 or 10% ethanol. It depends upon where you live. E85 though is a drastic change. The stoichiometry of e85 is somewhere in the realm of 9:1 AFR as opposed to gasoline's 14:1 AFR. If you just dump e85 into your tank without a tune, you will be extremely lean. Just dont do it.

As deylag said, at minimum you will need a bigger fuel pump, bigger injectors and a proper tune. I highly suggest you get a wideband AFR gauge to monitor things and make sure there is not dangerous lean conditions from a bad batch of e85 (not common but depends on your state and the time of year). I also HIGHLY suggest you upgrade your headstuds to handle the higher boost. Also its a good idea to upgrade intercooler piping or at least the couplers and clamps because, again, e85 demands higher boost which tends to pop stock intercooler piping which can get annoying.

 

For completeness' sake: stoich for gas is 14.7 and stoich for E85 is 9.8

 

just get all bolt ons, fuel pump and 3-port solenoid then get a tune. Evo X's make decent power on bolt ons.

 

Ah, I get it, the manual is talking about the 10% ethanol additive, I just saw this when I was getting gas today. I didn't realize this was (1) "E10" and (2) different from "regular" premium. Thanks for the explanation.

I was reading the introduction sticky and found this post:

Would it be a good plan that if I'm going to go E85 to just do the remaining part replacements after #5 and then get the tune? This seems to be the most logical and, I guess, cost effective order of upgrades. Also, if I were to do an UICP in there somewhere, when would be a good time to do this? I think this is one of the things that doesn't take a tune, is this correct? I just want to make sure.