Octane Booster?

Technical advice Q&A
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Heuer
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#1 Octane Booster?

Post by Heuer » Fri Jul 04, 2008 5:21 pm

Anybody have any experience of this stuff? I found a bottle of Millers and a can of GTA octane booster at the back of a shelf and wondered if they were any good. Sounds a bit like snake oil to me but some years ago I filled up with leaded fuel at one of the Thrust stations still selling it. They used super unleaded as a base and added lead which gave it an octane rating of 102 RON. When I did a Road Dyno test I saw a 10% increase in horsepower and torque. Too expensive and hard to find for regular use though.

Maybe I will add some to the tank and run it on the dyno for the hell of it!
David Jones
S1 OTS OSB; S1 FHC ODB

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andyp
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#2

Post by andyp » Fri Jul 04, 2008 11:09 pm

David

I run my old girl on super unleaded and Valvemaster plus. It allows me to run a couple more degrees of advance without any signs of pre-ignition. I'm not sure that you'd notice any difference just adding it to the tank as you'll already have your engine set up to suit your existing fuel.

That said it's would make a good test for your new gizmo.

Andy
1966 2+2 MOD Conversion

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Erikantwerp
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#3

Post by Erikantwerp » Sat Jul 05, 2008 6:55 am

Hi David,

Not much technical information I can provide you, only that I have been using Miller classic VSP+ for over a year and had no problems at all with it. In fact the engine just continues to run very smoothly and after a check up of the engine a week ago, everything looked very good inside so to me it appears to be a good product. I use it as an add on to 98+ unleaded fuel .

cheers
erik

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#4

Post by Heuer » Mon Jul 14, 2008 6:59 pm

OK I just added a bottle of Millers VSP to a 3/4 tank of super unleaded (97) and did a Road Dyno test. Made absolutely no difference to bhp or torque. I assumed with my high compression head (9.5:1) the octane boost would have made a difference, but no.

Next I will try the GTA Power Plus although it seems to be slightly more hazardous to use - contains aniline and xylene - but promises a 6.5 octane boost to standard 95 leaded. No idea where I bought this from or if it is still available. Web site on can says www.gta-oil.co.uk but I can find no mention of it to buy. Probably means it really does work!

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David Jones
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kingzetts
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#5

Post by kingzetts » Tue Jul 15, 2008 9:16 am

Speaking as a chemical engineer by profession, octane boosters cannot improve performance in an engine which is not first modified to run more ignition timing advance or a higher compression ratio.

To get maximum performance you want to have achieved complete combustion of the fuel by the time the piston has just passed TDC - too early and the gas pressure is resisting piston rise, too late and you don't reach peak pressure as the fall of the piston has already increased the volume of the combustion chamber into which the burnt gases are expanding. Since fuel/air mixtures take a small but finite amount of time to burn completely, you need to ignite the fuel shortly before the piston reaches TDC to allow time for combustion. But if you ignite too early you will cause power output to fall - you are looking for the optimum degree of advance.

Knocking (detonation) or pre-ignition (pinking) both involve fuel/air mixture outside the main flame front (propagating from the spark) igniting before the flame front reaches it. Detonation is pressure/temperature induced auto-ignition, while pre-ignition is usually caused by a secondary ignition source such as a hot carbon particle somewhere in the cylinder. Each phenomenon mimics additional ignition advance and by allowing peak pressure to be reached too early they reduce power (not to mention possible engine damage).

As higher octane rating fuels are less likely to detonate, and are more resistant to pre-ignition, it should be obvious that IF you are unable to set the optimum ignition timing on regular fuel, using a higher octane fuel may allow you gain increased performance - BUT ONLY IF YOU ADVANCE THE TIMING.

If by contrast you can already set optimum ignition timing with regular fuel, you will gain no advantage from using a higher octane rated fuel whether by using super-plus or an octane booster.

The only way in which boosting octane without timing changes will help performance is if your engine was already suffering from slight detonation but you were not aware of it (or if your engine has knock-sensor-driven adaptive timing like most modern cars do, in which case the brain makes the change for you). In any other case where improvements are noticed it is far more likely to be the Placebo effect with which doctors are very familiar - you expect an improvement, so you see/feel one. The only other reason I can think of to use one is if you are right on the edge on your timing, in which case it may insulate you from the effects of an occasional "dodgy" fill - you can be pretty sure that the actual octane rating of fuel in the petrol station tanks can vary a point or so from the official rating.

Sorry if this is teaching granny to suck eggs - but I think people can waste a lot of money on these products which are great in the right circumstances but useless for the majority of us.
John '62 S1 OTS

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#6

Post by Heuer » Tue Jul 15, 2008 10:10 am

Indeed. My car was set up on the rolling road using V-Power fuel (they claim 99 octane) which works well with the high compression ratio. I bought these additives to try, many years ago, if I was running on normal (95) unleaded where presumably I would need to retard the timing for optimum performance. Having made the decision I then promptly forgot about the additives and never carried them with me. I notice the GTA stuff needs a 5% solution in petrol to achieve a 6.5 octane boost which would cost an extra ?25 per tankful. It is however designed for race cars. With my single 500cc can I will get about 1 RON increase in an tank of petrol so hardly worth bothering about.

However several years ago I used my Road Dyno to compare super unleaded 98 with Thrust "Leaded" (102). I no longer have the recorded data, only a couple of printed graphs. I did two types of run - super unleaded and leaded - and for what it is worth this is what I measured:

Super-unleaded:
Image

Leaded 102 octane:
Image

I should add that I have no idea what the timing was set at but the car felt very quick with the politically incorrect fuel!
David Jones
S1 OTS OSB; S1 FHC ODB

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