jrwilliams95z28

Hey guys,

Ive always been running ultra 94 octane, but recently discovered it has 10% ethanol content. learning this brought into question the need for the extra octane compared to the subsiqent loss of energy content due to ethanol.

My question is, in a N/A application, stock block, heads, cam with just bolt on mods, would 91 octane pure gas deliever a better power output than 94 with ethanol? are there any dyno comparisons on these two?

I havent had the chance to try and datalog shell in my LT1 camaro yet but I switched to shell 91 in my 12' cruze ECO (1.4 turbo) and noticed a improvement on power and a big improvment in mileage. I always ran petro 91 in the cruze, which apparently has no ethanol as well but only at station's without the ultra 94, station's I dont often see or use.

The cruze is a turbo car so ive always seen a big difference from 87 to 91 octane for everything from performance to throttle response and mileage but the camaro I havent burned through my tank of 94 yet to test the 91 shell gas.

I am tuned but my spark advance is not set obsenely higher than stock its basically where it should be for 91 octane.

Another point in favor of 91 shell is that ethanol burns alot slower than gas and apparently the extra octane dosent get used to its full potential because a lot of the burn happens ATDC.

Does anyone have more information or links to research I can follow up on.

Ill be making one more trip to the drag strip this year and will be testing the 91 octane shell V-power out, last time I ran a DA corrected 13.1 on ultra 94so with the only change being the fuel I should get a decent indication of what is better for a naturally aspirated LT1.

bufmatmuslepants

iTrader: (3)

Every shell station around me, every gas station except marine gas stations, have 10% ethanol. Are you sure the shell has no ethanol? I always laughed about v power because it is "nitrogen enriched", but nitrogen acts like an inert gas, it's just marketing hype for "we put filler in the gas to lower our cost but Americans are too stupid to know"

ckyconan2003

iTrader: (2)

We only buy Shell gasoline, and I've never had a problem with V-Power 93.

However, I've been hearing a lot of rumbling about using a gas station with 100% gasoline. There's a place down the street from us that serves it and maybe I'll give it a try. Assuming they take debit cards...

jrwilliams95z28

Yes, I am 100% sure it is non-ethanol here in Canada. it says it right on the pump; 87 up to 10%, 89 up to 5% 91 "V-power" 0% ethanol.

Ill let my track times speek for themselves I guess

96capricemgr

iTrader: (1)

There isn't a definitive answer. How is the tune? What is the conditions of the injectors, anything internal like deposits causing it to want more octane?

My gut says the 91 is fine because the engine doesn't need any more octane and if the car is infrequently used then I would stick with the 91 just to avoid the potential troubles caused by ethanol sitting in the tank. I wouldn't overthink it beyond that though.

Puck

iTrader: (17)

Bit of a loaded question.

Unless you are tuned for it, lower octane gas makes more power. Octane is a measurement of resistance to detonation. This means that technically, the lowest octane your motor can run before detonation will make the most power. This is not a safe practice though, and because "Numbers Sell" (Megapixels on Camera, MHz on processors, HP on cars, etc) gas stations needed a way to differentiate fuels and decided to use octane ratings to directly compare.

Why do people with tuned engines make more power with race gas then? The higher octane is not what is making more power - it is the ability to run more timing, boost, nitrous, compression, etc before reaching detonation that makes more power.

TL;DR: Basically, if 91 is not pinging or showing knock, run the 91. You will save a bit of cash and might even make a HP or two more .

jrwilliams95z28

Good points! Thanks

flame

iTrader: (13)

When/where you hitting the track?^^^^

jrwilliams95z28

Probably next Friday at Cayuga (Toronto motorsports park) I just bought a house so I'm moving this weekend otherwise I'd go this friday

ThoR294

iTrader: (6)

generally, higher compression calls for higher octane to avoid detonation from the factory, GM states our cars need 91 or higher. if you put 87 in and try to drive your car like you stole it... you will feel the detonation. so it depends on your build

kgkern01

iTrader: (10)

I think you mean to avoid detonation, not quite the same as pre-ignition. The higher octane is used to avoid 'detonation' in higher compression engines. Ethanol is very resistant to detonation and has higher octane than typical unleaded gasoline, this why a lot of high compression and high boost cars run E85. Yes it has a lower energy content and requires more fuel to produce the same energy, thus the slight mileage loss with ethanol blends. If you are worried about mileage in your LT1, yes the non ethanol blends may give you another mpg, but power should be almost non affected assuming you are comparing same octanes of non vs low ethanol blends.

Ps, Once you get into the higher blends of ethanol power gains are to be found, but at the expense of mileage.

ThoR294

iTrader: (6)

true, my bad

jrwilliams95z28

Not concerned with Mpg's on the lt1. Only in my cruze which I switched to 91 v power with, never run less than 91 in either vehicle so don't even mention 87.

I'm not convinced on the debate for ethanol so I will be switching between the two and conducting my own datalogging and track testing because I can't seem to find any direct comparison just hearsay and opinions which don't count for much without evidence.

Ed Wright

iTrader: (1)

I had to back the timing down in my. '98 WS6 driver. (had the learn-down function disabled) so it would stop pinging on same (91) octane E10, wife's Lexus took about a day to learn that crap. Both of those cars and the gasoline motor home with which I was towing the race car all lost min 2 MPG on that **** compared to straight gas. Some stations began selling 100% gas, and the mileage reflects the change. That **** is only a good deal for corn farmers. 2 MPG in that motor home was 25%, 8 MPG on. 100%, 6 MPG on E10. E85 won't make the same power as 100% gasoline of the same octane. There is more to it than octane.

Sof86

It's true, that's what the signs say at the stations. I've never had a problem with Shell 91.

I just put a tank of Petro 91 in the car. First time using anything other than Shell 91. I'm about to take the car out....I'll be keeping an eye on the lt1 scanmaster and see if it pulls timing, knocks etc.