Fuel Type

[LOUD MOUSE]

As I raced those engines for 4 years and used several of the Race Gas Names (use gas and put decal on the car and get $$$ if ya won) I didn't GET LUCKY at all.
I'm in no way a chemist but I KNOW WHAT I did/do and works and don't appreciate your GOT LUCKY comment.
Mid racer at best???????????????.............lm

A hot running two stroke may well reduce it's EGT with a race gas, but it has to be the right gas. Sounds like LM got lucky that time.

It's an old thread, but many questions were left unanswered.

100ll is designed to burn slowly in a slow running aircraft engine. The old myth about it being good for performance came back in the 50s when gas was about 80 octane and compressions were low. The car guys wanted more compression and that caused detonation, so if they were able to beg borrow or steal some av gas they could run a higher compression without meltdown.

So higher compression was the power generator. Av-Gas allowed them to use it.

We found on the dyno that 89 octane made marginally more power than VP C12 with a smoother power curve - that was on a full race CB160 turning 11,500 with raised compression.

Some race gas burn faster than others and a faster burning gas will have more burned before it leaves the exhaust port. Others are slower burning. Some have a low evaporation curve and some don't evaporate until at least 100 degrees higher.

All the gas is not used before it exits the port. Poor atomization and non effective squish mean that some of the larger fuel droplets are still burning as the gas goes down the pipe.

A hot running two stroke may well reduce it's EGT with a race gas, but it has to be the right gas. Sounds like LM got lucky that time.

Any more octane than a motor needs to avoid detonation is a complete waste of time and money and usually results in less power and a lighter wallet.

The only thing I really like about leaded race gas is that it tends to burn cleaner than unleaded and needs a cooler spark plug which is much easier to read at the race track. Unleaded tends to leave a sooty deposit and often needs a hotter running plug to keep clean.

Ethanol and methanol are hard on fuel systems, but we don't have rubber tipped float needles, or galvanized fuel lines, so that is less of an issue. Ethanol will leach the resin out a fiberglass tank though.

E85 is a whole different story though. It generally needs larger jets, more spark advance and can stand much higher compression. Alcohols generally need to be jetted differently than gasolines.

[teazer]

LM, I think you misunderstood my comment. Maybe it was ambiguous.

It was not intended to be insulting in any way. I read your post to mean that you had just tried it and it worked. I was saying that you were lucky that it worked, because it might have produced the opposite effect had you chosen a slower burning gas or one with a lower vaporization temp.

Why is it that you think I'm trying to insult you? I go out of my way to make polite respectful reference to you and your services. I don't get it.

As for mid racer at best - if that was supposed to be insulting to me, it was off course. I never claimed to be the best racer in the world. My Cb72 was reasonably successful, but it was never a match for the Jerry Kooistra rocketships. I got lucky a few times (not on the CB) and took home first place trophies but most of my results were just top 5 finishes. I can live with that luck. I was really lucky that Jerry and Barney lived in a different State :-)

[LOUD MOUSE]

OK.
This was a VERY OLD subject and I had asked a question not make a statement. (June 29,09) (Dec 6, 2009 last entry)
One feller responded and I left his reply for others to respond but alas no further interest until ya resurrected it.
Ya have a habit of doing that and at times (many to me) ya expound theories (usually mention race days) as though to me should give merit to your statement and at times "I more than often ignore
them as it's old info which isn't correct today".
The fuel thread was/is a chemist nightmare (will lean or rich mixture BLUE the pipes for one???)
I recall fellers claiming to get some AV GAS (just after WW2) and how they thought the engine ran hot and was the fastest engine "out there".
Of course I believed them until I (now my turn) I was competing in the Mickey Thompson Series where we wanted all the power available and not melt a piston or seize the engine to get that power. "small airplane engines use pyrometers in each exhaust to measure temp today" (computer controlled) and I found any of the 5 (depended on event and location which was offered, all above 102 OCTANE) gases/fuel LOWERED the exhaust temp and allowed us to LEAN the jet and gain power/speed. (FLAME SUIT IS ON!)
My racing history is long and to some would be boring so I attempt to share my experience with questions at hand with others as a Layman who realizes most on this forum are Neophytes" and want to get their Street Bike (usually just acquired) running. (usually want the cheapest, quickest way) as today for instance not many need or can afford a timing light (use it once/twice a year) but can make simple test tools.
Another thing ya don't know is when a correct answer/cure to a question is offered I don't Usually get involved as many on this forum have Gained lots of info (even bought books) and share it well.
I believe in KISS and do that most times!
LM............... A EXPERIENCED RACER IN 4 TYPES OF COMPETITION OVER MANY YEARS!!!!!!!!!!!!

LM, I think you misunderstood my comment. Maybe it was ambiguous.

It was not intended to be insulting in any way. I read your post to mean that you had just tried it and it worked. I was saying that you were lucky that it worked, because it might have produced the opposite effect had you chosen a slower burning gas or one with a lower vaporization temp.

Why is it that you think I'm trying to insult you? I go out of my way to make polite respectful reference to you and your services. I don't get it.

As for mid racer at best - if that was supposed to be insulting to me, it was off course. I never claimed to be the best racer in the world. My Cb72 was reasonably successful, but it was never a match for the Jerry Kooistra rocketships. I got lucky a few times (not on the CB) and took home first place trophies but most of my results were just top 5 finishes. I can live with that luck. I was really lucky that Jerry and Barney lived in a different State :-)

[jensen]

As a theoretical discussion is of no use, and memories start to change the reality, I decided to measure it on the dyno.

I used RON 95 and RON 98 petrol, both unleaded, and found out that the temperature of the engine and mufflers where the same, as the power-curve was the same too.

Putting RON 98 petrol is just a waist of money, accept when the engine is pinging on RON 95.

Jensen

[Tango911]

old timer told me to use a lead additive, did these not run on leaded gas back in the day??

[brewsky]

The need for lead in old engines has been debated for a while, and if you search long enough, you can find any answer you want.
The fear is softer valve seats in older pre-unleaded engines will wear faster without it.
I don't use lead additives or substitutes, since I don't think I will put enough miles on the engine to matter.
Most technical sites I searched previously said not to worry about it unless you plan on using the engine in constant high load situations.
It's probably more important to keep the valves adjusted than to worry about finding a gas additive to replace lead.
Even when lead was standard in gas, you will notice very short valve adjustment intervals in the maintenance books for older engines, so maybe the lead wasn't all that great to begin with?

[jjjjjj]

I have been having a problem with my late model dream running rich. I was looking for some jets at Western Hills Honda and told the vintage parts guy that I was using non-ethanol premium. He suggested that might be my problem as the bike's compression does not require it and it may also be burning incompletely. Hey I don't know! That's just what he said. Will try regular soon and see if it makes a difference.