[JSH]

Originally Posted by Snowwolfe

You guys should try to find an episode on Engine Masters where they did dyno runs on the same motor but using different octane fuel. 87-93 made no difference in power. Same for 104. It was an education for sure.

Did they change the tune for the 104?

[MatthewAMEL]

Originally Posted by Snowwolfe

You guys should try to find an episode on Engine Masters where they did dyno runs on the same motor but using different octane fuel. 87-93 made no difference in power. Same for 104. It was an education for sure.

Carb engine with no ECU and fixed timing advance.


I really enjoy Engine Masters and Freiburger/Dulcich's stuff in general, but they are dinosaurs who abhor Fuel Injection and ECU's.


Adding 104 or TORCO won't increase power on OEM tune, but it will keep the engine from pulling timing as temps increase.

[Joshinator99]

Originally Posted by Snowwolfe

You guys should try to find an episode on Engine Masters where they did dyno runs on the same motor but using different octane fuel. 87-93 made no difference in power. Same for 104. It was an education for sure.

Originally Posted by MatthewAMEL

Carb engine with no ECU and fixed timing advance.


I really enjoy Engine Masters and Freiburger/Dulcich's stuff in general, but they are dinosaurs who abhor Fuel Injection and ECU's.


Adding 104 or TORCO won't increase power on OEM tune, but it will keep the engine from pulling timing as temps increase.

Matthew is spot on. Even in bone stock form the LT engines are knock limited on 93 octane, never mind 87! I bet you an LT4 on a hot day under heavy load would be putting out nearly 100 HP more running the 104 (or even a blend of 104 & 93) than one running on 87 (assuming it didn’t nuke itself on the 87 first).

[Snowwolfe]

Originally Posted by JSH

Did they change the tune for the 104?

All I remember is they reported optimum timing was 29 degrees for each grade of octane they tested. I was surprised at the results as I would of guessed significant hp/torque losses with the lower octane fuels and potential knock.
Think they also said they couldn’t really say how much knock was present due to the testing in the dyno room.

[KingLT1]

Originally Posted by Snowwolfe

You guys should try to find an episode on Engine Masters where they did dyno runs on the same motor but using different octane fuel. 87-93 made no difference in power. Same for 104. It was an education for sure.

That is because the engine they tested this on was not octane limited on 87 octane. So there was nothing to gain since optimal timing could be ran on 87. Octane is used to control detonation. LT engines are octane limited even on 93 let alone 87.

[Snowwolfe]

Originally Posted by KingLT1

That is because the engine they tested this on was not octane limited on 87 octane. LT engines are octane limited even on 93.

I have already covered the basics in my first 2 posts in this thread...not sure what is so difficult to understand?

Not difficult to understand. Just reporting what I watched on TV

[Camaro1973]

Originally Posted by Joshinator99

Matthew is spot on. Even in bone stock form the LT engines are knock limited on 93 octane, never mind 87! I bet you an LT4 on a hot day under heavy load would be putting out nearly 100 HP more running the 104 (or even a blend of 104 & 93) than one running on 87 (assuming it didn’t nuke itself on the 87 first).

Octane really isn't going to matter tbf. Power loss is mostly just due to high IAT/MAT temps and humidity not necessarily from knock itself.


When I mixed race gas on my 93 tune it made no difference in power. Only thing that helped was my chiller in hot ambient temps.


If the engine is knocking, then that is a completely different story. You would need to be 150+ MAT temps for that to start though.

[RamAir02]

Originally Posted by Joshinator99

Matthew is spot on. Even in bone stock form the LT engines are knock limited on 93 octane, never mind 87! I bet you an LT4 on a hot day under heavy load would be putting out nearly 100 HP more running the 104 (or even a blend of 104 & 93) than one running on 87 (assuming it didn’t nuke itself on the 87 first).

So for a road course application (HPDE events, 20+ min sessions), would a stock ZLE benefit (pull less timing) from running unleaded 100 octane? That's typically available at tracks I frequent. Or is the gain negligible for that application?

[NG329]

Originally Posted by RamAir02

So for a road course application (HPDE events, 20+ min sessions), would a stock ZLE benefit (pull less timing) from running unleaded 100 octane? That's typically available at tracks I frequent. Or is the gain negligible for that application?

Honestly, I don't think it will matter until you get to the faster end of the group.

For reference, I picked up 5mph down the front straight at NJMP when I put in E40 over Premium 93 -- which really only equates to a couple of tenths off the lap time. However, the straight speed is just one aspect of the lap. Staying off the brakes for as long as possible and carrying as much momentum into corners as possible will serve you better than trying to extract every bit of power out of the engine with race fuels.

Also, earlier in the season I ran a 45 minute stint on pump gas in the ZL1 and the car did not heatsoak. Lap times were consistent and the speed down the front straight was consistent.

If Ethanol wasn't cheaper than regular gas I probably wouldn't run that either unless I was trying to go for a PR or keep up with someone faster. But to go fast at a HPDE event, Premium gas should be fine.

As we head into cooler temps the car will run stronger anyways so I would just save the $$$. Race Fuel is $10-$15/gallon at the track by me.

[Gunkk]

Originally Posted by David Gordon

I now have a station by me that sells 104 Unleaded. My car is stock, save for a cold air intake. Would adding 5 gallons gain me any power? With no tuning. Will the cars computer reconize there might be no knock and add timing on its own?

If the car is not tuned and you've got 93 in the tank, you're already the best the car can give. If you get into a high IAT situation, a point or two more octane probably won't help much. Because IIRC the ECU will pull timing on high IAT alone even if you're not getting knock retard.

[David Gordon]

Originally Posted by Snowwolfe

You guys should try to find an episode on Engine Masters where they did dyno runs on the same motor but using different octane fuel. 87-93 made no difference in power. Same for 104. It was an education for sure.

I saw one where n/a motors benifited almost no power gains, but the they threw in a F-150 Ecoboost and it gained 25+ rwhp, I would assume from that episode we could gain some.

[wnta1ss]

Originally Posted by David Gordon

I now have a station by me that sells 104 Unleaded. My car is stock, save for a cold air intake. Would adding 5 gallons gain me any power? With no tuning. Will the cars computer reconize there might be no knock and add timing on its own?

According to Jannetty Racing, there is a performance gain (above 93) from running 100 octane unleaded in a stock ZL1, yes getting away from knock retard is the purpose, see his comments about it in this thread https://www.camaro6.com/forums/showt...=569561&page=3

[JSH]

Originally Posted by wnta1ss

According to Jannetty Racing, there is a performance gain (above 93) from running 100 octane unleaded in a stock ZL1, yes getting away from knock retard is the purpose, see his comments about it in this thread https://www.camaro6.com/forums/showt...=569561&page=3

I don't think anyone doubts you can tune a stock LT4 for 104 and make more power, but I'm a bit surprised it makes a little more w/o a tune.

[MatthewAMEL]

Originally Posted by JSH

I don't think anyone doubts you can tune a stock LT4 for 104 and make more power, but I'm a bit surprised it makes a little more w/o a tune.

Agree. I have my doubts about Jannetty. When someone asked if he could post the dyno sheets showing the 30hp gain, he suddenly does too many dynos and couldn't find one.


Be awesome if someone with a stock LT4 could do a comparison with 93 vs 100+ octane and post.