Octane Booster Additives

[types26/36]

Do octane boosters work? I'm running an engine with approx 11:1 CR and getting pre-ign on acceration, this is on super unleaded 99 octane, I've retarded the timing but it has not helped.
I've heard that the octane booster additive are nothing more than a scam and when they quote a 7 point raise in the octane rating it is actually only a point seven rise ...e.g.. 87 octane would only end up at 87.7 and not 94 octane as presumed!
Has any one used an octane booster and found any significant improvement?
I don't doubt that the additives can clean the fuel system but has any one had a detrimental experience (effects on rubber hose/plastic floats/o rings etc.)
Any comments?

[hatman]

Tetraboost lead additive is the stuff - it's the real thing rather than a substitute and, as the supplied-at-source lead used to do, does in fact raise the octane rating (up to 102 if you need to go that high). My own skimmed-headed twink is also of the order of 11:1 and never pinks.

[bcmc33]

We had this discussion a little while ago, and I was condemned as an idiot for not only using the stuff, but believing that it works. I use Tesco 99 octane plus an additive on the basis that it should make 105 octane.
I still believe that the lead additive must work as Tetra-ethyl lead was always used to increase the octane rating (to eliminate knocking in engines by increasing the octane value) until the use of catalist converters became the prime method of making vehicles more ?green?.

However, the question remains; what do the petrol companies add to make 95 octane into 99 octane?

And does the additive make the Elan go better? I really don?t know. But as some sort of comparison, 99 octane in my normal road car goes better than 95 octane.

[paddy]

However, the question remains; what do the petrol companies add to make 95 octane into 99 octane?

I think the answer is that it is refined at the refinery to a targeted mix of different hydrocarbons according to the target octane rating. It's not just the same basic fuel with additives added.

The effect of any specific additive depends on the mixture it's being added to; you can't keep adding more and more additive to keep increasing the octane rating indefinitely.

There's an site here with lots of background information:

http://www.turborick.com/gsxr1127/gasoline.html

Paddy

[Rob_LaMoreaux]

one interesting thing I learned from my Father-in-Law is that leaded gas can actually make spark knock more likely. The lead can form nodules in the combustion chamber that then become hot spots leading to uneven ignition. While he has mainly been doing diesel emmission research the last 10 years, he has been in engine development for the last 30. So it might pay to clean out the combustion chamber some.

I'll ask him to forward the article he wrote for the Alfa club magazine and see if he has any other comments when I get home (they are coming over for dinner).

Rob

[elandoc]

Hi Brian

I ran 11:1 for ages on 98RON with only occasional knocking. The engine was tuned on the dyno and I don't believe they had to retard it - it was one of those freakish engines, however, with good torque and power (now scattered down Conrod Straight). I would think that if you can't tune it on 99RON, then either the oil company's lying (Shell is infamous for it down under), or your engine builder forgot to carry the one and your CR is too high. 11:1 is about the limit unless you have engine management and knock sensors.

Currently in OZ, the big additive is ethanol, which gives an increase in RON, but is cheaper (no excise) to produce. If you look at the chemistry, however, it's not anywhere near as dense and so gives less energy per gram - the increase in power from the higher CR is lost by less energy in the fuel. On modern cars, it's even worse as the Lambda sensor gives erroneous readings and your fuel consumption goes up.

Patrick

[rgh0]

Hi patrick

You get that engine back together yet ?

Brian

11:1 does require some octane boost versus any normal road fuel premium unleaded you can buy. The ethanol blends do increase octane rating but the refinery companies reduce the rating of the rest of the blend to bring it back to the specification as best they can - no need to waste high octane components in fuel where it is not needed.

The lead based boosters are the best most of the rest that typically use high octane fuel components are a waste of time as the proportion you add it in is to small to make any difference. In Australia at least it is illegal to use a lead based octane booster in road cars and illegal to sell it for use in road fuel. To buy leaded Avgas to use in my Elan running 12.5:1 I need a permit and I am only allowed to use it on the track as an historic race car.

cheers
Rohan

[types26/36]

Patrick,Rohan & others, thanks for the replies, Patrick could very well be right in that I may have a higher compression then 11:1 but as for blaming the engine builder then I only have myself to blame
The engine has a 1600 crank in a 1500 block with piston mods and due to memory fade I cant find/remember the specs(it was done a couple of years ago)
I may just do a combustion chamber volume check but in the meantime I'll try one of the octane boosters as I have heard good reports about the Millers additive.

[bcmc33]

Patrick,

How can you doubt those nice altruistic oil companies that have only our best interests at heart?

I guess I've never really believed that the Tesco super unleaded I use is actually 99 octane. But I am prepared to believe that with the small amount of lead additive I put in the octane level will be nearer the 101 octane for which the engine was originally designed.

[John Larkin]

I have used Miller Octane booster in my Elan and in 1974 Rover V8 (10.5:1 C.R. I think) for about six years. The Rover used to pink badly under heavy acceleration with the Castrol product that I previously used --- it would pink under normal acceleration if I filled up and forgot to add the booster. I never had any pre-ignition in the Elan, but it seems to run better with the Miller additive.

John Larkin

[twincamman]

you may as well add a can of Guinness ---all that additive junk is just pixie dust -----ed

[cabc26b]

available addtives/ccompounds to increase octane rating ( ranked approx by volume to effect)

Alcohol
MBTE
MMT ( the replacement package developed by Ethyl Corp and marketed as HiTec 3000)
TEL

TEL and MMT were favored b/c the ratios need to impact the octane rating were very low. like one drop per gallon of gas would treat ...

[elandoc]

A drop of Guinness can do wonderous things, Ed.

Rohan, the engine is still in bits but the head has been repaired with new... everything, really. I'm waiting on rods and pistons from Steve Taylor which I thought would be air-freighted, but he seems disturbingly vague about delivery dates - I think they're from Dave Bean - 5.23" rods and slipper pistons to fit the L bock (CP pistons, I believe). I hope they're strong (and light).
I've entered Speed on Tweed, which coincides (and is co-located) with the Australian WRC round, so I didn't want to miss it. To make sure, I switched entries from the Elan to Derek's 240bhp 340R. That should be some ride.
I probably won't get back to Tarmac Rallying until the kids are in school (a long time - one isn't even borne yet!).
I may yet have another crack at FoSC Bathurst next year - why don't you pencil it in?

Cheers

Patrick

[rgh0]

Good to hear your making progress on the engine. Bathurst next year is certianly on my list depending on my workload on the income producing side of my life.

Steve normally supplied in the past JE Pistons and Carillo rods - both top quality items. If delivery is vague through Steve and time is critical you can get them direct from the US potentially quicker direct from the manufacturers or through US ditributors.

cheers
Rohan

[denicholls2]

Other things aside, you may want to consider retarding the spark a bit as an alternative to adding lead.

Yes, you will lose power. But you will not suffer the other detrimental aspects of burning lead in your engine. While one of these is an environmental impact, I'm primarily referring to reduced longevity of engine internals.

If you're racing or for some reason have sky-high compression on a pure street engine, this won't work so well. But if you're just trying to get rid of the occasional knock and can spare a couple horsepower, it may be a much cheaper alternative in the long run.

Europa-Renault's run stock 10.5:1 compression, which seems to be borderline for available U.S. premium fuels. They also have a mild reputation for dropping piston skirts under detonation. I back off the advance, but different fuels will still give the occasional ping. I'm annoyed enough by it that at first excuse a thicker head gasket will be likely to get the compression down. If I need the power back, I can always eat more judiciously.

-- Doug Nicholls, 54/1822 Ma~