octane

[Royal Tiger]

Originally Posted by NOT A 45

E85 will make more power on any engine even a stock one because it's rated at 120 octane. So like I said above, the ecm will not remove ignition timing because there will be no spark knock. Other advantages are cylinder cooling, and ethanol is 1/3rd oxygen.

[hudson773]

you guys need to see the video, all the myths you believe were disproven in a scientific way using state of the art computers, not opinion. when you do the same tests they did and come up with a different conclusion, then I will listen.

[Silveradoss573]

Where is this video at because I want to watch it. Guess for the past 20+ years in racing, we should've just used 87 pump gas in all our engines lol.

[Badbubba]

Originally Posted by hudson773

after watching the Engine Masters show on octane where they compared regular with 93, 110, 120 and e85 on the dyno and found NO significant power difference, are you still willing to pony up .20 a gallon more for premium and much more for the racing stuff? all the fuels liked the same timing advance which kind of debunks the theory that higher octane burns slower.. watch the episode if you can, it was very interesting.

Believable. Depends on the parameters of the engine. BTUs will drop from pump 87 to 93. But unless they are running the tests on a LS3/L99, it's not relevant for us. Use the octane rating the engine likes. There's a limit to the amount of octane that increases performance. Higher than that will not really yield any benefits. So, their engine only required 87 for maximum performance. Increase compression or install a power adder, turbo or supercharger, then a higher octane will be relevant. That's where ethanol will shine. E100 is about 113 octane, pump E85 109 octane and pump E70 106 octane. You get race performance at pump gas prices. Plus ethanol has twice the cooling effect over standard gasoline, due to it's latent heat of vaporization. I have dyno sheets verifing increased hp and torque on a turbo vehicle when comparing E10 with E70. But there will still be a point where more octane will not add performance. It just comes down to what your engine requires.
I tried to watch that episode after reading your post, no luck. Just free trails, not worth my time.

[FasNuf]

Originally Posted by hudson773

you guys need to see the video, all the myths you believe were disproven in a scientific way using state of the art computers, not opinion. when you do the same tests they did and come up with a different conclusion, then I will listen.

OK, so watching the CSP video, all I saw was that the OEM tune wasnt optimal. We all know this.
He then tuned it to 87 and made a gain over OEM. He then filled it and ran on 93 and saw basically no HP increase. This is correct. octane doesnt make HP on it's own.
He did make more HP on 93 after he advanced it 3 times for an additional 7 degrees which showed a much improved gain. If he kept the 93 tune and refilled with 87, he said it would not be good. In other word it would detonate.
This seems to jive with the tuning worlds methods of tuning in that added octane allows increased timing to get more HP/TQ. His 87 tune was knock limited is why he couldnt add the 7 degrees on that tune to make the same power as the 93 tune.

[RS/SS '10]

Originally Posted by NOT A 45

E85 will make more power on any engine even a stock one because it's rated at 120 octane. So like I said above, the ecm will not remove ignition timing because there will be no spark knock. Other advantages are cylinder cooling, and ethanol is 1/3rd oxygen.

Thank you Not A 45

[silversleeper]

Fasnuf already answered the orignal post above me.
I'll comment on some things that make it true as far as more octane required. Already mentioned in this thread, it does no good to have more than 85 or 87 octane in many or most cars, not all for sure.
Why would more be required?
Higher compression ratios
carbon buildup on pistons or combustion chambers of heads
a piston or head hotspot due to inadequate cooling or burn pattern
hot spot on spark plug (need a colder one) or exhaust valve
unequal fuel, air in or out , intake ex manifold do to poor design or limitations
humidity and elevation and temperature outside
airflow of intake and ex systems
psi of boost if applicable
alcohol or water injection
type of fuel delivery, worst to best- carb, throttle body injection, port injection, direct injection. Injector spray pattern good?
dynamic compression ration, a function of what camshaft and intake port and ex port/tube lengths and diameters have for compression waves and flow
ignition advance
load on the engine, light or heavy load. Rpm changes other things in the list so by changing rpm many things change including fuel air mixing and dynamic compression ratio or cylinder filling
swirl of mixture in the combustion chamber due to intake ports and design and quench area design of combustion chamber along with piston design
oil leaks into intake include valve guides etc. Oil has low octane

well, that's what is off the top of my head. Feel free to add to the list.


I was just thinking back to some cars I had. A couple needed high octane even though they weren't super high performance engines so they wouldn't knock. And a few I had ran better on low octane. I believe it's because I couldn't tune them, so that low octane brought them closer to knock, without knocking, than high octane so it made them run better, slightly more mpg and power.

[gtstorey]

I had the video in my screen and just rewatched. They are running an LS3 with the Holly ECM. I don’t know if the Holly has load/rpm tables or just a fixed timing. They talk like timing is a single number so I don’t thank they were using load/rpm tables or even rpm tables. They also said they don’t have a knock sensor so they couldn’t really try to maximize through the rpm range.

They also said they wouldn’t run 87 in the motor in a car but it was safe in the controlled enviro of the engine dyno.

[Royal Tiger]

Originally Posted by hudson773

you guys need to see the video, all the myths you believe were disproven in a scientific way using state of the art computers, not opinion. when you do the same tests they did and come up with a different conclusion, then I will listen.

I didn’t realize watching MY engine do a dyno pull on 93, filling the gas tank with E98 which worked out to about E60 and doing ANOTHER dyno pull minutes later and getting MORE HP and TQ was a myth.

[gtstorey]

And the e85 made some more power. Not a huge amount but some.

[demonspeed]

I think all you guys who parade the virtues of low octane are heroes. We need more guys like you out on track - 20 minutes of WOT should sufficiently narrow the cluster of cars out next round.

FasNuf explained it best.

[redcoats1976]

i drive a 6 cylinder at close to legal speeds.if i was going to go to the track a tank of 93 would be the first thing on my list.lots of full throttle would make that cheap insurance,but for around town and doing 75-80 on the highway ,87 should do.would not get frisky with a V8 unless i was running 93...

[FasNuf]

In case anyone didn't realize, there's an additional spark table besides Hi/Lo. There is one used for flex fuel and is based on alcohol content from the FF sensor. This is the adder table that adds onto the hi/lo octane table. Just more info for you guys.
(E67 ECM) possibly E38 but I'm not sure.

[demonspeed]

Originally Posted by redcoats1976

i drive a 6 cylinder at close to legal speeds.if i was going to go to the track a tank of 93 would be the first thing on my list.lots of full throttle would make that cheap insurance,but for around town and doing 75-80 on the highway ,87 should do.would not get frisky with a V8 unless i was running 93...

In your case, it would be a waste (unless the 3.6 actually recommends premium for best performance - which I don’t think it does). Unlike the performance engines (L99/LS3/LSA/LS7), there’s nothing in the V6 tuning to take advantage of the additional octane.