Gordon0652

iTrader: (4)

Tomorrow i will be testing the theory octane and the effect it has on ONLY horsepower and torque.
I will start off with two runs with 87 in the tank, move to two runs with 93 in the tank then i will put the "octane booster" in with the 93 and see what happens.
Bought the booster at my local car quest. On back of the bottle it says "NOT STREET LEGAL".

We'll see what happens...

RPM WS6

iTrader: (3)

There is no theroy. It's all fact. Lower octane combusts more easily, and will make more power right up to the point where detonation begins. At that point, you need to increase octane to resist unwanted, early combustion.

In a modern engine, we have knock sensors that will pull timing when detonation is observed, so lower-than-required octane will always reduce engine power (unless you kill the low octane spark tables), and obviously, detonation itself will also reduce power production. This is why your test results won't really prove or disprove the relationship between octane and horsepower.

On the other hand, it would be easier to demonstrate this will an engine that will run without detonation on 87 octane to start with. Then, as you increase octane you will notice performance (and MPG) decrease.

Tx91z28

RPM beat me to it... dam lol

Gordon0652

iTrader: (4)

"theory" was the wrong word to use. My fault. Maybe I can find a local with a 4-cylinder. Mostly I'm testing if a good rated booster is legit.

idle

iTrader: (5)

Did I hear someone say that running a car that can normally run on 87, that when fueled with something like 93, would decrease HP and MPG performance?

RPM WS6

iTrader: (3)

Yes. If an engine is able to run *optimally* (meaning, no timing advance reduction from knock retard) on 87 octane, then adding additional octane will reduce engine performance and mileage. Same is true of an engine that can run optimally on 93 octane....if you add 100 octane, it can only hurt.

Higher octane is harder to combust and burns slower. This is great to prevent detonation and allow full timing advance in high(er) compression applications; but the harder, slower burn does nothing to help (and will decrease) engine performance when not needed.

idle

iTrader: (5)

So I have a stock Trans Am WS6... putting 91 in it slows it down?

RPM WS6

iTrader: (3)

No. The LS1 was designed to run optimally on 91-93 (premium) octane. This is the factory recommendation, and will provide best performance in a stock LS1 engine.

If you run an LS1 on 87 octane, there are knock sensors which will reduce spark timing and allow operation of lower octane fuels with reduced detonation. This, however, is not optimal for performance, since the engine was designed with spark and compression characteristics that require premium fuel to properly take advantage of. Reduced timing advance and detonation will hurt power.

Having said that, if you put 100 octane in your stock LS1, it will reduce performance. It is far more octane than is needed to keep full timing advance without any detonation.

Similarly, if you put 93 octane in an engine that was designed to run optimally (no detonation, no spark reduction) on 87 octane, it will reduce performance.

71novaguy

iTrader: (2)

ding ding. this is why top fuel cars squirt 87 octane fuel into their butterflies to get the thing started.

the only true way to test the octane booster is in a controlled knock situation, like the test that is actually used test octane/cetane ratings.
Its a controlled knock. You may be able to find an old unit somewhere on the internet. We used them at school in our fuels class. It was neat to test some of the local gas stations and see if the were actually putting out what they said they were.