Let's talk octane...

MightyBobo · 11-06-2011, 03:22 PM

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.

XwChriswX · 11-06-2011, 03:25 PM

Quote:

Originally Posted by MightyBobo

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.

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

MightyBobo · 11-06-2011, 03:25 PM

Quote:

Originally Posted by XwChriswX

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

Correct.

XwChriswX · 11-06-2011, 03:29 PM

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?

MightyBobo · 11-06-2011, 03:34 PM

Quote:

Originally Posted by XwChriswX

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?

Depends on the injectors, but I'd hazard to guess you'd need to go even BIGGER. I dont know how close we are to maxing out the stock injectors with only basic breathing mods off hand, but I doubt any FI kits are going to come with HUGE injectors - just enough to handle the max HP of the kit. Whereas with an E85 setup, you'd need injectors 30% bigger than THAT, really.

Also, cant forget the fuel pump...one that can at least keep up w/ those injectors...

XwChriswX · 11-06-2011, 03:37 PM

Quote:

Originally Posted by MightyBobo

Depends on the injectors, but I'd hazard to guess you'd need to go even BIGGER. I dont know how close we are to maxing out the stock injectors with only basic breathing mods off hand, but I doubt any FI kits are going to come with HUGE injectors - just enough to handle the max HP of the kit. Whereas with an E85 setup, you'd need injectors 30% bigger than THAT, really.

Also, cant forget the fuel pump...one that can at least keep up w/ those injectors...

Of course, once you know how much you'll be 'injecting' then you know how much fuel you need, in terms there is your pump size required so you get that as well. Interesting... Soooo much involved with just switching gas lol.

MightyBobo · 11-06-2011, 03:39 PM

Quote:

Originally Posted by XwChriswX

Of course, once you know how much you'll be 'injecting' then you know how much fuel you need, in terms there is your pump size required so you get that as well. Interesting... Soooo much involved with just switching gas lol.

Theres a lot of science behind setting up a proper fuel system. You'd think you can just add a pump, but sometimes even just one pump isnt enough for an E85 setup. I should see if I can find my friends crazy *** home-made pump setup for his garage built, TT 427. He already had a 1100HP/1000Tq twin turbo Silverado, and sold it...

Red__Zed · 11-06-2011, 03:43 PM

Quote:

Originally Posted by Methodical4u

so back to my other question... since the VVEL cannot be changed, can the timing of the engine still be changed? Basically i'm saying... if I wanted to run race gas for a run down the 1/4 and I needed to tune for it, can the timing be advanced due to the higher octane to maximize power? OR is that all part of the VVEL?

You can advance timing within certain limits.

Quote:

Originally Posted by XwChriswX

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?

like most things, it depends on what you are doing. the other thing you have to watch for when setting up for e85 is corrosion in your fuel system, which often requires running different components than what TT kits come with (not that familiar with Z kits though)

XwChriswX · 11-06-2011, 03:45 PM

I dunno, but all of it sounds really cool, the R&D of it.

Would be crazy to see.

Would the VQ37 be a platform that you'd wanna see in E85, or the fact that it's not boosted and VVEL limitations would make it a waste of time?

MightyBobo · 11-06-2011, 03:47 PM

Quote:

Originally Posted by XwChriswX

I dunno, but all of it sounds really cool, the R&D of it.

Would be crazy to see.

Would the VQ37 be a platform that you'd wanna see in E85, or the fact that it's not boosted and VVEL limitations would make it a waste of time?

VQ37 in stock form, N/A with E85 is a waste of time, IMHO.

Boosted however, you can get gains. But I question the worthiness of such gains other than flexing the e-penis size...

11-06-2011, 03:22 PM	#1 (permalink)
MightyBobo A True Z Fanatic Join Date: Feb 2009 Location: Las Vegas, NV Posts: 8,465 Drives: No cars; only bikes Rep Power: 53	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. __________________ I don't own a car anymore.

11-06-2011, 03:29 PM	#4 (permalink)
XwChriswX WFLYIDNNE Join Date: Jul 2009 Location: In The Fastlane Posts: 50,648 Drives: 02 GDB WRX Rep Power: 452	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? __________________ Bonnie - Stage 2, Audio build coming this fall! R.I.P. Abby 3/29/10 - 3/30/14

11-06-2011, 03:45 PM	#9 (permalink)
XwChriswX WFLYIDNNE Join Date: Jul 2009 Location: In The Fastlane Posts: 50,648 Drives: 02 GDB WRX Rep Power: 452	I dunno, but all of it sounds really cool, the R&D of it. Would be crazy to see. Would the VQ37 be a platform that you'd wanna see in E85, or the fact that it's not boosted and VVEL limitations would make it a waste of time? __________________ Bonnie - Stage 2, Audio build coming this fall! R.I.P. Abby 3/29/10 - 3/30/14

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