Which race gas to diagnose knock ?

ManBearPig · Nov 22, 2017

I see some intermittent knock at throttle tip-in and am trying to determine if it's real or false. I've mixed in some vp octanium and saw no change but would like to try some actual race gas as well. I know that certain oxygenated fuels have a different stoich than the standard e10 the car is tuned for. What fuel is best to use when strictly trying to troubleshoot s potential knock? I see ms109 is the most commonly discussed but if I'm not mistaken it really needs a specific tune otherwise the car will lean out.

Thanks

EFI · Nov 22, 2017

I would use some Sunoco 260 GTX. You don't need to go all out on something like MS109 to diagnose false knock.

Although tip-in KR is not going to be solved by race gas, nor is it a false knock situation. The PCM instinctively takes away timing in sharp throttle actuation and it doesn't necessarily mean the knock sensors actually pick up noise.

15GTBEN · Nov 22, 2017

ManBearPig said:
I see some intermittent knock at throttle tip-in and am trying to determine if it's real or false. I've mixed in some vp octanium and saw no change but would like to try some actual race gas as well. I know that certain oxygenated fuels have a different stoich than the standard e10 the car is tuned for. What fuel is best to use when strictly trying to troubleshoot s potential knock? I see ms109 is the most commonly discussed but if I'm not mistaken it really needs a specific tune otherwise the car will lean out.

Thanks

Sunoco 260 GTX is good. Make sure your tank is completely empty before using race gas. In my case it was false knock and poor fuel quality in my area.
My car ran the best on race gas, too bad it’s so expensive.
I ended up going back to stock as my tuner wasn’t willing to work with me.:rant:

ManBearPig · Nov 22, 2017

According to Sunocos website the closest location 260 GTX is sold is 118 miles a away.

There is a station that sells Sunoco "standard" leaded 110 about 50 miles away though.

EFI · Nov 22, 2017

Meh I wouldn't use leaded stuff in there, even if for a little bit.

You can also try a can or two of Torco...that stuff really works well to increase effective octane up to 100. I know you said you tried octanium, but I never had as good results with that as I have Torco.

ManBearPig · Nov 22, 2017

Torco may be a better option if I can't find anything unleaded and non oxygenated in my state.

15GTBEN · Nov 22, 2017

ManBearPig said:
Torco may be a better option if I can't find anything unleaded and non oxygenated in my state.

Definitily use unleaded. I tried torco and it did not work as well as real race fuel in my case. Lucas did nonthing.

ahl395 · Nov 22, 2017

Two whole cans of Torco should really do the trick. Put in one can before filling and one can after filling if you want to really make sure its mixed well.

mustang1 · Nov 22, 2017

Owners manual ~
"Do not be concerned if the engine sometimes knocks lightly. However, if it knocks heavily under most driving conditions while you are using fuel with the recommended octane rating, contact an authorized dealer to prevent any engine damage.

I think for knock to mess up an N/A engine, the engine would have to be under load. Can't recall if you get the same thing with stock tune and 93 octane. Whatever knock you see with that should be "normal".

dubster99 · Nov 22, 2017

A can of torco or octanium should do the trick

ManBearPig · Nov 22, 2017

I've tried octanium and didn't see any difference. I'd just like to try out some proper high octane fuel too. I've read mixed reviews of octane booster effectiveness.

moffetts · Nov 22, 2017

Personally, I see a huge difference mixing the Lucas octane booster stuff in with 91. 2-3 degree positive knock becomes 2-3 degrees negative. Based purely on my experience, I would say you don't have an octane issue.

ManBearPig · Nov 22, 2017

moffetts said:
Personally, I see a huge difference mixing the Lucas octane booster stuff in with 91. 2-3 degree positive knock becomes 2-3 degrees negative. Based purely on my experience, I would say you don't have an octane issue.

That is entirely possible. But I won't be comfortable saying that for sure until I try some real race fuel.

dubster99 · Nov 22, 2017

ManBearPig said:
I've tried octanium and didn't see any difference. I'd just like to try out some proper high octane fuel too. I've read mixed reviews of octane booster effectiveness.

If it's octanium or torco and an MMT based octane booster, it's the same as running race gas basically. If you mix it as specified, you're fine. Running a 100oct mix of pump and octanium/torco won't be different than running 100 unleaded.

Knock at tip in is probably not false, if you're not seeing it anywhere else.

ManBearPig · Nov 22, 2017

dubster99 said:
If it's octanium or torco and an MMT based octane booster, it's the same as running race gas basically. If you mix it as specified, you're fine. Running a 100oct mix of pump and octanium/torco won't be different than running 100 unleaded.

Knock at tip in is probably not false, if you're not seeing it anywhere else.

I don't think it's false either. But if it's not from low octane and it's not false....wtf is it from?

Which race gas to diagnose knock ?

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