Gas Octane

[engineermike]

If we assume a 91 octane rating for E10, moving to E30 would result in an increase of about 3 to 5 octane points, bringing the octane rating to approximately 94-96. Split the difference and say 95.

It’s actually quite a bit higher than this in practice, especially with gdi. The octane rating of e85 doesn’t account for all of the evaporative cooling knock suppression effects.

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[shogun32]

If the tuner moved the borderline tables up like FRP does (and myself and others), it will send it deep into knock very fast and severe knock events will happen.

ok, fine. but I was speaking from a point of "routine driving", not sending it. Or are you saying the tuners are getting "greedy" to the extent that <65% throttle and <4000 RPM is flirting with danger? If so, that level of aggression is irresponsible IMO.

 

[WildHorse]

ok, fine. but I was speaking from a point of "routine driving", not sending it. Or are you saying the tuners are getting "greedy" to the extent that <65% throttle and <4000 RPM is flirting with danger? If so, that level of aggression is irresponsible IMO.

Some do. Running on the edge of the envelope kinda thing.
I don't trust any tune, I seen knock with 93 pump. Never seen it
with 94 or 95. So I use an octane amount where I never
see the KS getting unhappy.

 

[junits15]

I just saw at ACE today canned fuel with 93 octane rating on the can. Somebody is still making it. The marina on the Ohio river used to carry it, but no more.

Careful with that stuff, I think you’re talking about tru fuel, I don’t believe it’s the same as pump gas. It has a ton of additives in it.

ok, fine. but I was speaking from a point of "routine driving", not sending it. Or are you saying the tuners are getting "greedy" to the extent that <65% throttle and <4000 RPM is flirting with danger? If so, that level of aggression is irresponsible IMO.

not if you run the fuel the tune is designed for.

 

[shogun32]

not if you run the fuel the tune is designed for

well yeah.

My point simply was just because you dispense "93" into your tank doesn't mean you actually got "93". Or maybe I'm in god-forsaken Colorado and they only have 89.

Even a tuned car should "sneak up" to the expected threshold, even if the sneaking is done in strides and not baby-steps like factory.

No?

 

[K4fxd]

Careful with that stuff,

I use it in my chain saw

 

[WildHorse]

even if the sneaking is done in strides and not baby-steps like factory.

I like fast ramp rates.. way more fun ha-ha.

 

[engineermike]

ok, fine. but I was speaking from a point of "routine driving", not sending it. Or are you saying the tuners are getting "greedy" to the extent that <65% throttle and <4000 RPM is flirting with danger? If so, that level of aggression is irresponsible IMO.

Understand that the borderline spark tables are where they expect onset of knock on 87. Virtually every 93 na tune worth having, including FP, increases the borderline tables 3-5 deg to account for higher octane. At light loads it’s running on MBT timing rather than borderline anyway, so it wouldn’t matter much. But if it’s a 93 tune and you put 87 in the tank, the starting point will be deep into knock when you go wot. I think it’s bad advice to tell someone with a 93 tune to just run 87 and it’ll be fine because it might not be fine the moment they go to pass someone.

As far as advance rates go, there are normal and fast advance rates and each one is a function of rpm. I’d guess that some tuners increase these rates but my personal strategy is different so I don’t change the rates from stock.

 

[GregO]

Careful with that stuff, I think you’re talking about tru fuel, I don’t believe it’s the same as pump gas. It has a ton of additives in it.

 

[K4fxd]

This is what I use in the weed wacker and chain saw.

https://www.tractorsupply.com/tsc/p...MIreDzoI3fhgMVv0H_AR1ofAt5EAQYBSABEgKjdfD_BwE
Q: What octane is the fuel rated
2 years ago
1 Answer
A: Thank you for your inquiry! The VP 40:1 Small Engine Fuel has a 94 octane rating.
2 years ago

 

[shogun32]

But if it’s a 93 tune and you put 87 in the tank, the starting point will be deep into knock when you go wot

Who the hell drives Wot on public streets? But point taken.

 

[engineermike]

Who the hell drives Wot on public streets?

Seriously? Who doesn’t?!?

 

[ice445]

Eh, I wouldn’t be giving out that advice. If the tuner moved the borderline tables up like FRP does (and myself and others), it will send it deep into knock very fast and severe knock events will happen. The stock tune starts it out at values safe on 87 and “sneaks up” on knock so the knock events are low magnitude which doesn’t do much damage.

Yup, I experienced this first hand. I saw as high as +8 sometimes and even had a few throttle closures. Too low of octane for the tune is detrimental long term on the GT.

 

[WildHorse]

This is what I use in the weed wacker and chain saw.

Too much additives/aromatics in a fuel:

Engine performance: While some additives can improve fuel performance, excessive amounts can lead to negative effects. For example, high concentrations of detergent additives can cause deposit buildup in the engine, leading to reduced performance and efficiency. Similarly, high aromatic content can increase the fuel's sensitivity to knocking, which can cause engine damage.

Fuel system damage: Some additives and aromatic compounds can be corrosive or form gums and varnishes in the fuel system over time. This can lead to clogged fuel filters, damaged fuel injectors, and other issues that may require costly repairs.

Fuel stability: High levels of certain additives can compromise fuel stability, leading to the formation of gums, sediments, and other contaminants that reduce the fuel's quality and shelf life.

 

[K4fxd]

Too much additives/aromatics in a fuel:

What are the additives in the VP 2 cycle engine fuel?

I suppose I could just add oil to turbo blue, might even be cheaper....

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