Megasquirt Support Forum (MSEXTRA)

Anyone here ever try to tune their knock sensors with high octane fuel ? If so, what were the results.

You better define what you mean by "high octane". Is that 100 octane, or something more like 115/145 avgas? How is the octane level boosted, using TEL, lots of alcohol, something else?

Even though I've done tuning via reading the knock sensor, dyno tune is the best, you can see the result on the graph and don't have to worry about speed limits, driving, road condition, or traffic.

Sunoco and it's an alcohol blend as far as I know. 110 MON.

If you mean setting up your knock threshold and other various knock system settings, then yes. I've tried the retarded ignition map by -10* degrees with 92 octane, and the retarded ignition map by -5* with a full can of Torco octane booster and 92 octane. Both methods are similar according to my logs, but the torco method is my favorite so far. I used scatter plots to identify the normal engine noise levels.

KaPower wrote:If you mean setting up your knock threshold and other various knock system settings, then yes. I've tried the retarded ignition map by -10* degrees with 92 octane, and the retarded ignition map by -5* with a full can of Torco octane booster and 92 octane. Both methods are similar according to my logs, but the torco method is my favorite so far. I used scatter plots to identify the normal engine noise levels.

What scatter plot did you use ?

My Favorite is RPM/Knock-in/Knock-in & also RPM/Map/Knock-in

Haven't been able to make much use out of the table generator other than looking at individual cylinders to setup the gain based off load and rpm (instead of the single rpm vs noise table that we currently have) The interesting thing to note is how useful a load vs RPM table would be for setting knock input noise thresholds.

How much octane did the booster provide. I hear they don't do all that much. Was contemplating on mixing toluene into the fuel as seemingly Sunoco stopped their supply of race fuel here.

Torco is the real deal. Most octane boosters advertise in points that equal .1 so 92 would become 92.4 with 4 added points. Torco actually added several points extra depending on the mix ratio. My knock sensor went dead quiet with Torco added to the system, and the engine felt more powerful (possibly because way less false knock retard?). Try it out and let us know. It's 20-30 per can, but seems effective from my testing.

-Jason

Methanol is also a good additive directly to fuel. I routinely use 10-15% by volume in all my cars.

Jim

benckj wrote:Methanol is also a good additive directly to fuel. I routinely use 10-15% by volume in all my cars.

Jim

I thought it doesn't mix well with fuel. I was told toluene was a better alternative.

Keep in mind that things like forged pistons, solid lifters and stiff powertrain mounts can give you false knock readings. Racing suspensions can also produce false knock on road.

prof315 wrote:Keep in mind that things like forged pistons, solid lifters and stiff powertrain mounts can give you false knock readings. Racing suspensions can also produce false knock on road.

Yes, the intention was to make sure I have a situation with no knock to set a baseline.

I thought it doesn't mix well with fuel. I was told toluene was a better alternative.

I've done some tests and if using low mix ratios it mixes just fine. Much the same as ethanol. Toluene is expensive and I believe more corrosive to certain metals (ie brass, copper) than methanol.

benckj wrote:

I thought it doesn't mix well with fuel. I was told toluene was a better alternative.

I've done some tests and if using low mix ratios it mixes just fine. Much the same as ethanol. Toluene is expensive and I believe more corrosive to certain metals (ie brass, copper) than methanol.

Are you sure about the corrosivity of Methanol vs Toluene ? I thought meth was rather corrosive ...

Methanol is generally much worse than toluene, especially when the methanol starts to absorb water.

that's what I thought.