Leaded vs. Unleaded Gas
Leaded vs. Unleaded Gas
(OP)
I have a Yamaha WR426F with a fourcycle engine with a 12.5:1 compression ratio. Yamaha specs that the minimum octane rating is 95 and must be an unleaded gas. Most all pump gas within this area does not exceed 91 and does not work well at all when used with an octane boost additive. Race fuel is readily available but the leaded versions are much cheaper and have still higher octane ratings than the unleaded. Yamaha states that leaded gas will harm my engine,,, is this true and if so why and how?





RE: Leaded vs. Unleaded Gas
Adding Tolulene or Xylene will increase the octane rating. To the best of my knowledge, this is a technique used by oil companies to make premium unleaded.
This link will give you a wealth of information on internal combustion engine fuels
http://blizzard.rwic.und.edu/~nordlie/cars/gasoline.htm...
Regards
pat
RE: Leaded vs. Unleaded Gas
The link also makes reference to the troubles of blending unleaded with leaded fuel, which I didn't completely understand???
RE: Leaded vs. Unleaded Gas
The problem with brewing your own fuel, is that burning fuel is a chemical reaction, and as you mix the chemicals, they may interact in a way other than as expected. Normally with the major hydrocarbon components, this is not a problem, but with various additives it can create unexpected side effects. This is unlikely, but not impossible.
Some time ago (probly something like 8 or 10 years) i mixed premium unleaded and leaded 50/50, and got a better result than either on its own in that the mixture prevented pinging whereas the pure as from the pump fuels did not. I discovered this one day as I needed leaded, but could only get unleaded, so I topped it up to get to the next station.
Some years later, the reverse was true. The mix pinged while the premium unleaded did not.
First time was on a very hotrodded old air cooled VW with 10:1 static compression ratio, but as it had steel valve seat inserts, and was well and truely pre polution controls, it could run on either so long as the octane was OK.
Second time was a 350 chev in my ski boat, also with 10:1
Regards
pat
RE: Leaded vs. Unleaded Gas
It does burn dirty and increases black deposites on plugs, chamber and exhausts, and if to much is used this can be a problem due to loading up of plugs. There might already be a lot in the premium unleaded you are buying.
Sorry the answer is not straight forward, but the situation is not straight foward.
Regards
pat
RE: Leaded vs. Unleaded Gas
If you decided to go for the leaded please keep me informed
RE: Leaded vs. Unleaded Gas
RE: Leaded vs. Unleaded Gas
Geez, 12.5 is a big ratio for a factory machine!
RE: Leaded vs. Unleaded Gas
RE: Leaded vs. Unleaded Gas
Guyguy may be right with any deposits being blown out since this machine revs up to 10,000 or 11,000 rpm.
Swall, I've tried all the different 91 pump gases with no success. I currently use a 50:50 110 leaded with 91 unleaded thereby yielding a 100.5 blend which works fairly well but still runs better on straight 110!!
RE: Leaded vs. Unleaded Gas
at 12.5 to one, I would be looking at 105 octane or more.
Unless otherwise stated, I always presume pump octane.
I agree, it sounds to me like the lawyers wrote the manual
Regards
pat
RE: Leaded vs. Unleaded Gas
Incidently Don has been using 91 with additive so far and he won in the Intermediate class last week in Victorville!
Rod
RE: Leaded vs. Unleaded Gas
Shaun TiedeULTRADYNE/LUNATI Arl,TX(stiede@ev1.net)
RE: Leaded vs. Unleaded Gas
Carbonic acid is formed as a byproduct of the combustion of hydrocarbons, and NOx forms when air is heated to the temps encountered in a high compression engine. NOx with water makes nitrous acids which are relatively strong.
I never had a race car exhaust rust out, as they normaly get broken or become obsolete before that happens
Regards
pat
RE: Leaded vs. Unleaded Gas
Shaun TiedeULTRADYNE/LUNATI Arl,TX(stiede@ev1.net)
RE: Leaded vs. Unleaded Gas
RE: Leaded vs. Unleaded Gas
1) Your modern exhaust might be made from a more durable material.
2) Your more modern engine is designed to minimise the NOx output as it is considered a major polutant. The acid produced from the NOx is a lot stronger than the acid produced from the CO2 that is still there in large quantities.
3) Your more modern fuel probably contains less sulphur, thereby producing less SOx and subsequent strong acids.
Regards
pat
RE: Leaded vs. Unleaded Gas
Just consider that in Jan. 2001 (I think--- my famous 'memory', you know!) I rebuilt the engine in my 1930 Model A Ford after something like 70 years and a bit over 100,000 miles---funny, not a spec of rust!!!
Rod
RE: Leaded vs. Unleaded Gas
Despite what I say above, I agree, rust is not a problem in engines, as carbonic acid is weak, and the stronger acids are in lower concentrations, especially in polution controlled cars.
The acids are purged from the engine in the form of gas as it runs. They collect in the water that condenses in the cooler end of the exhaust. Mufflers have always been prone to rust.
My only point was, that it is not caused by lead, so running leaded fuel won't rust your exhaust anymore than unleaded, and possibly even less as the light grey coating might just protect the surface a little
Regards
pat
RE: Leaded vs. Unleaded Gas
If there is perchloroethylene in there it most definitely will form HCL which is as strong an acid as the acids formed by oxides of nitrogen and sulphur.
I am amazed to hear that perchlor is used when you consider how long it has been known that it is a castiogen. I know the lead is to, but you needed it for the antiknock and lubrication and valve seat coating.
Regards
pat
RE: Leaded vs. Unleaded Gas
The argument about the corrosive nature of lead really doesn't matter in this case, as I have never known a race engine exhaust to rust out before it is discarded for other reasons
Regards
pat
RE: Leaded vs. Unleaded Gas
drwebb's comments are pretty well on the mark
Brominated and/or chlorinated hydrocarbons are added to leaded fuels as lead scavangers to convert the lead deposites to volatile lead halide salts, so as to avoid excessive build up of lead.
The level that these are added at is critical. To much, and you get corrosion, to little and you get fouling.
Avgas specifies the chemically correct ratio, while automotive gas normally has a little more.
Once again, one of the advantages of leaded fuel was that the deposites lubricated some components, so for this to work, the lead scavangers must be in the correct proportion to leave a little lead behind.
The light grey or white deposites on the tailpipe of a correctly tuned car running leaded fuel are probably these lead halide salts. They will deposite where the temperature of the tail pipe surface is low enough for them to solidify on contact.
See the link in my post of 06/11/03 for details
Back to reality again.
The only engines I ever saw corrosion problems on were boat engines which operated in a salt water environment, or engines that were left exposed to the weather and not used for years. I am sure that the corrosion in these cases is down to the salt and long term exposure to water, and occurs no mater what fuel is used.
The only cars I ever saw with premature corrosion of the exhaust system, were those production road cars that had a design that retained water (like the loop over the back axle), and where the manner of use never evaporated the water out of the system. In my experience, racing use blows and boils all water out of the tailpipe and muffler.
I don't see any of these problems with this guys motor bike
Regards
pat
RE: Leaded vs. Unleaded Gas
On a related note, spray-type chlorinated carburetor cleaners are reputed to sometimes ruin oxygen sensors due to HCl formation on combustion if used on EFI equipped cars. There are non-chlorinated carb cleaners available, but ALL 'throttle plate cleaners' are nonchlorinated for this reason.
As you note, chloride from NaCl in the marine environment is a corrosion promoter, and HCl has chloride built in to the acid, which makes HCl even more corrosively aggressive than H2SO4 or HNO3. But I don't want to delve too deeply here for fear someone from the Corrosion Engineering board will wander by and give us all a schooling!
Probably the reason they weren't too concerned about the 'carcinogenity' of perch is that in gasoline it's contribution would be totally swamped by the much more potent compound benzene, which is still there!
RE: Leaded vs. Unleaded Gas
The Cl- ion is certainly agressivly corrosive to many metals, but the SO4-- ions and NOx- ions are also quite corrosive. The NOx ions are often in much larger quantities in a high compression, non polution controll engine, where I expect that in any properly formulated fuel, very few Cl- ions will remain as ions in the exhaust.
I got outmy old chemistry book, but could not find the reactivity series tables. Maybe it's to long since I studied this.
Bottom line still remains that corrosion is not a real world issue with race engines.
There are certainly some inconsistencies on how we view toxins. Chlorinated hydrocarbons are mainly banned or listed as dangerous in the minds of most of us, but many still splash benzine containing compounds around with careless abandon. Maybe it's the fact that we can buy it so easily, that we take it for granted
Regards
pat
RE: Leaded vs. Unleaded Gas
What happens is that welding will make a heat-sensitized zone in unstabilized stainless where the chromium precipitates out as chromium-carbides along the grain boundaries, and the very smallest exposure to halides, especially the Cl in roadsalt, will produce intergranular corrosion and cracking-type failures.
Proper stabilization takes the form of added Ti or Cb to tie-up the excess carbon as titanium-carbides or columbium-carbides.
RE: Leaded vs. Unleaded Gas
Rod
RE: Leaded vs. Unleaded Gas
Harvey.
RE: Leaded vs. Unleaded Gas
Also, I agree that leaded fuel should pose no problems with your engine, but I’d be interested in knowing how toluene works. If I’m not mistaken, there was a lengthy discussion on its use in this forum earlier this year. I believe Pat had some insight during that discussion. Take a look at thread 71-41617.
-Joest
RE: Leaded vs. Unleaded Gas
RE: Leaded vs. Unleaded Gas
110 or 140 octane it does need rejetting and is heavier on the float etc. Tell them it is for racing and you may get some slick sponser help.
also Compression can be fooled by the use of cam overlap or cam seperation angle, We are limited to flatops in one class of racer and I use a 104 lobe seperation that brings the pumping compression way up there.
Hope this helps or gets you thinking.
RE: Leaded vs. Unleaded Gas
Thanks all for your input.
RE: Leaded vs. Unleaded Gas
Low leads are safe and many racers use them, just not in AMA because it has been outlawed.