Author Topic: octane denotation  (Read 248 times)

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Offline joe_indi

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Re: octane denotation
« on: June 12, 2018, 12:21:00 pm »
Glancing through the posts I came upon this one.
The bit about octane rating was something I would have posted earlier but feared appearing like a prize ass , which you yet might when you read down
Here in India our regular fuel is (optimistically) claimed to be 86 or 87 RON, but several factors play villain.
Usually it gets adulterated. So 75 - 80 might be being generous.
What this fuel does is kills a lot of saws from pinging. The preventive measure that I used to do till recently was setting carbs to run richer, filing ignition module to be set a bit retarded and lowering compression with a thicker cylinder gasket or two thin ones.
You might recall my post on issues with my Renault. I have a friend who is an engine tuner (he remaps ECUs). He had come home to flash a new map on my Renault. I asked him whether he could also tweak the tiny 3 pot Hyundai that I have for local runs. The ignition timing gets retarded if the throttle is pressed too hard to prevent knocking. Unfortunately he could not read the ECU, but he suggested boosting the octane level to fool the sensors so that the timing would not retard.
Toluene is what he advised me to try but it is not easily available here. He then suggested I try any solvent that contains toluene, the most common being Nitro Cellulose thinner.
He told too much will do no harm except to my wallet, but too little would have no effect. 10% would make some difference he said.
Well it made a big difference and I use NC thinner regularly.
I have an old Yamaha, a 2 stroke, so I thought why not?
So the old Yam got a dose of NC and the difference was remarkable. No death rattle when the throttle was twisted too fast and a more pronounced growl.
The progress to a chainsaw and brushcutter was inevitable.
So the next to get a dose of NC was my FS 100 brushcutter. Very nice
So was my saw guinea pig, my old 018, then it was a 460, and a 461 and then it was done on some customers' saws, with very positive results.
What they all claimed is the power delivery improved, lesser heat, a more pronounced exhaust note and very smooth progression.
Being the unethical guy that I am I did not want to scare them away by saying "Hey lets mix some thinner in your saws"
Instead I gave the thinner an impressive blue tinge using some marker ink ;D
I told them it was a special fuel additive that I was testing.  ;D

10 - 15% works really well.

Now several guys in our automobile group are adding NC thinner to their cars' fuel tank .
So in my opinion, Octane is to the good  8)
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