Let's talk octane...
 

Admittedly, I am not a gearhead or anything really even close. I know a little about engines, how they work... just basic stuff.

Obviously when a person goes to the track, some will run race gas, I don't know how many here do, but that usually requires the tune to be for the higher octane, correct?

What is the increase in power with the increase of octane?

Some will run E85, others on here say on an NA engine it doesn't do much for the car in terms of power output. With the Evo's and being on the Evo forums for so long. They just switch to E85 and gain like 30 or 40 whp. How unfair :mad:

So what are the ins and outs with all of this? Can we make more power this way or not?

Higher octane is used on turbo cars to turn up the boost safely. I ran 27psi on a stock f20 by running c16.


On an NA app, you can advance the timing some, but there aren't usually huge gains t be had from adjusting timing.

ok, well what about the VVEL? Can the Z's timing even be adjusted because of that? How much NA power could be had by running 100 or more octane?

I haven't spent a lot of time checking out datalogs for the Z, but I highly doubt there is much to be gained by running high octane gas-- probably not enough to make a substantial difference.

When you're switching from one octane to another, you need to siphon out all of the previous fluid correct? Mixing the two = vewwy bad??

not necessarily. Of course, running your high octane tune and getting a load of 93 into the engine can be risky.

I ran mixes of C16 and pump gas with no issues.

With that being said, is there say a noticeable difference you could sense that you knew it was time to switch from say a 93 octane map to the racing fuel octane map or vis versa?

:confused: Why would mixing high octane with a regular octane be possibly risky?

Octane is nothing more than a measurement of a fuels resistance to detonate. Higher the octane, higher the resistance.

You could, in theory, cruise around in a 370 with 87 octane...but if you even think about putting a load on the motor, your odds of running into trouble are high.

E85 is great if your car is setup for it: it burns cooler, has a higher overall octane, and its cheap. Assuming you make sure your source is ACTUALLY E85 (and not, for instance, E70 or whatever they run in the winter in many places...), then in essence, its race gas on the cheap. However, its downside is obvious: to get the same amount of energy from E85, you need to burn something like ~30% more fuel to get the same effect as pure gasoline of the same octane. None the less, E85 will still be cheaper overall, over race fuel.

So, when your running forced induction, you can keep raising your boost thanks to the higher octane, and go for a more aggressive tune with E85. Obviously, raising boost is a very quick way to gain power, hence why anyone who has a 335i, WRX, or Evo do these mods very quickly (along with the good breathing mods, of course).

On the 370, all you could do really is advance your timing and squeak out a little bit of extra horsepower, but (like Zed's already said), you wont be seeing a huge gain at all in our car - its pretty efficient as it is.

some fuel formulations don't blend well together. And running the aggressive map when it's not suitable puts you at risk of detonation.

On my car, it wouldn;t run on 93 with the c16 map.

If your tune is for...say....93 octane and its a VERY aggressive tune...but you can only source 91 octane at the time? That could be risky.

Other than that, with a comfortable tune, I see no reason why it'd be risky.

So your range per tank goes down considerably using E85 due to needing more fuel per cycle? So larger injectors are a must?

Correct.

Gotcha. I've run FI before, but I've never tuned for anything above what I could get at the local pump.

Since larger injectors will come with any Z TT kit, could you theoretically convert to E85 at the time you went TT? Or would you need even larger injectors than the ones that come with the kit being the kit has already compensated for the extra fuel needed for TT?