Thread: Saws and octane-toulene?

Back when I was into turbo gassers (I've since graduated to turbo diesels) the name of the game was octane when increasing boost. I stumbled across some Porsche guys who were using toulene (a common thinning agent for some paints and adhesives) to boost the octane of pump gas to 105+ when starting with premium (92). I have a Sunoco near me so I can get 94 and I usually do for the saws. Is there any benefit in bumping the octane up 6 points or so? Be advised though-you have to show ID to buy it because unfortunately it's also a main ingredient of meth

Originally Posted by IHDiesel73L

Be advised though-you have to show ID to buy it because unfortunately it's also a main ingredient of meth

I just bought a quart of it and its sittin on my front porch. I better lock it up ...Bob

Octane above 93 is only beneficial with compression readings above 200psi.

Excess octane can actually inhibit performance.

Higher octane will make an MS Deuce-Eleven run stronger and faster than a ported 660.


Sheesh you guys are idiots!

Originally Posted by IHDiesel73L

Back when I was into turbo gassers (I've since graduated to turbo diesels) the name of the game was octane when increasing boost. I stumbled across some Porsche guys who were using toulene (a common thinning agent for some paints and adhesives) to boost the octane of pump gas to 105+ when starting with premium (92). I have a Sunoco near me so I can get 94 and I usually do for the saws. Is there any benefit in bumping the octane up 6 points or so? Be advised though-you have to show ID to buy it because unfortunately it's also a main ingredient of meth

I bought a gallon of toluene from Sherwin-Williams and the octane rating is 120

Originally Posted by nmurph

Octane above 93 is only beneficial with compression readings above 200psi.

Excess octane can actually inhibit performance.

Agreed.

Engine efficiency is directly related to compression ratio, and higher compression ratios require more octane to prevent detonation. I guess people saw high performance high compression engines running high octane fuel and assumed that the higher octane fuel must be part of the performance advantage, when in fact the opposite is true. Pure octane has less energy per unit than regular fuel, so if you use more of it than you actually need to prevent detonation, you'll get (theoretically) less power than you would without it.

Years ago I saw this first hand when I bought a new motorcycle that had a relatively low compression engine. After trying several tanks of fuel in it, it became obvious that I got a few miles more per tankful on 87 octane compared to 91 octane.

Originally Posted by cityboy

Agreed.

Engine efficiency is directly related to compression ratio, and higher compression ratios require more octane to prevent detonation. I guess people saw high performance high compression engines running high octane fuel and assumed that the higher octane fuel must be part of the performance advantage, when in fact the opposite is true. Pure octane has less energy per unit than regular fuel, so if you use more of it than you actually need to prevent detonation, you'll get (theoretically) less power than you would without it.

Years ago I saw this first hand when I bought a new motorcycle that had a relatively low compression engine. After trying several tanks of fuel in it, it became obvious that I got a few miles more per tankful on 87 octane compared to 91 octane.

Makes sense-I just didn't know much about the compression ratios of saw engines.

Originally Posted by IHDiesel73L

Makes sense-I just didn't know much about the compression ratios of saw engines.

Some of them can benefit from higher octane fuel, especially if modded a bit to increase compression. My Dolmar 5100s is pushing almost 200# in stock form and many others that I've worked on had room for more compression which can often be achieved by using a thinner, or no, base gasket. You sound like you'd probably know how to do a squish test.
As mentioned, though, 93 is fine to @ 200#. Not sure anyone would want a work saw with much more than that.
Might as well build an alcohol saw if you want to run special fuel.

Just as an FYI for guys that need higher octane numbers for their performance saws or??. I bought some VP C5 Octane boost to increase the octane for my 1970 Chevelle SS. I had a 582 cu-in pump gas motor installed with 10.6:1 compression and noticed some slight detonation on really warm summer days. I added about 7 oz of C5 to about 12 gallons of fuel and it took care of the detonation immediately

I am only offering this up for those that might need a fairly cheap solution @ .50 per ounce it really does the job!

Toulene or methyl benzine has a strong benzine ring that doesn't break down until much higher temperatures. It will work in high compression engines to reduce detonation (acetone is another additive that can raise the octane rating), but in a stock engine the toulene inhibits the rise time of the cylinder pressure and you will lose power.

Stick with the pump gas, it is all you need.

Thx Terry for your quick reply. Just wondering if the C5 octane boost which is a VP race fuel company product will hurt my big block chevrolet motor? Do you think it will leave deposit or ?? C5 has MMT as the main additive to boost octane.

I wouldn't know. Why don't you contact VP and see what they have to say. They may be able to give you some guidance as to what engines or mods they recommend with their fuel.