[cortez08]

I have a 100 octane pump down the street from my house and the nearest E85 station is 1.5 hours to 3 depending on traffic. With no port injection or meth how much whp could be expected on upgraded twins or single on 100 octane alone. What if I added PI and only ran 100? Would it be comparable to E85 numbers? I know it's expensive but I don't have time too spend hours driving for E85.

[335e92tx]

Id find someone that has a truck where you can load up on e85. At least for 30gals at a time. The prob with most race gas (maybe 100 Unleaded is close) is that its not the same SG as unleaded 93. They do have unleaded 100 race but it will be more expensive even than 100 race with lead (usually about 4 grams per gal). Anything below 4 is likely to be unleaded.

Power wise, It will probably be close to e85. I think e85 is like 105 octane math wise but since it has less BTU it requires more per hp so the 100 will be easier on the pumps and probably wont induce as much of a change in AFR (depending on Specific gravity) - which likely will make a more consistent AFR thru the power band. I would start with like 50/50. That should get you to 96-98 and just watch individual cyl retards..

BUT, I dont know that I would run a e85 map. I would run like a 95+ map or something.. think custom tune really..

[mike@x-ph.com]

It all depends on your map and how hard you are going to push these turbos.

[Ozzie335i]

Cortez, how much per gallon for the high octane stuff would you have to pay?

[cortez08]

Thank you for all the helpful info. I did not know that 4 grams was the threshold between unleaded and leaded.

I pay about $8 a gallon for Sunoco 100oct unleaded out of the pump.

I want to push the turbo(s) 25+ I am wondering if it is any easier or harder to tune with port injection 100 octane versus E85.

$8? lol

Just size the turbo(s) appropriately to benefit most from 93. If you do it right, you'll make more power than you'll ever need anyway.

[335e92tx]

Originally Posted by cortez08

I want to push the turbo(s) 25+ I am wondering if it is any easier or harder to tune with port injection 100 octane versus E85.

The biggest issue with traditional race gas (105+ usually) is bc it has lead, it will cause plug life to be much less. But, leaded gas does a better job of coloring plugs are far as proper mixture goes. Now, having said that, bc most people dont 'read' plugs anymore and just tune via the ecm, its not as difficult to get a good AFR.. at least overall. A properly tuned carbed engine could probably have just as good mixture control and atomization as a FI after it reaches operating temp. But at all other times, a FI motor will be easier to drive during warm up.

So, the answer to your question is ( ;-) ) no, not likely to make any difference on a DI motor with advanced controls such as the MSD81 dme. The biggest difference between the two options you are looking at will be in fuel delivery not in engine control.

[Jeff@TopGearSolutions]

Originally Posted by FCobra94

$8? lol

Just size the turbo(s) appropriately to benefit most from 93. If you do it right, you'll make more power than you'll ever need anyway.

Same over by me for 100 octane. At the drag strip it's little cheaper but not by much.