Bruce A. Frank
July 2nd 03, 06:25 AM
In theory the lead provides lubrication, but in application it causes
sticking and burned valves from un-even deposits on the sealing surfaces
of the valve and seat. Now if you have rotators on the valves there
might be a different story. With the materials used in valves and valve
seats, even antique aviation engines 8^)... valve seat recession hasn't
turned out to be a problem. Unleaded fuel may extend the TBO for top
overhauls. If it is a concern, run a tank of LL through every 4th or 5th
fillup.
Jay wrote:
> It's true that the 2 stroke (BSFC .6-.65) will burn "far" more gas
> than the 4 stroke (BSFC .4-.5) but av-gas costs "far" more than mo-gas
> so this offsets the difference.
>
> I was under the impression that the aircooled 4 strokes needed the
> lead for lubrication of valves, etc, so while you might get away with
> burning auto gas, how much wear do you want to put on your engine top
> end? Sounds like people with 4 strokes running auto gas run some of
> both types to keep the top end lubed. For the same capacity tank you
> will have shorter max range on the 2 stroke.
>
> The thing I liked about the 2 stroke engines was the high power to
> weight ratio and small amount of adaptation required from other
> applications (such as Snow Mo). And I realized that your cost per
> mile/hour in fuel was less with the 2 stroke.
>
> The difference in reliability is real but could possibly be offset by
> a redundant power arrangement which would be really nice to have for
> other reasons such as mountain flying or extended flight over water.
> Its common practice to use reducnt systems in hi rel systems, so why
> not the most complicated and critical componant? So save money?
>
>
>
> "Gilan" > wrote in message >...
>
>>A 2-stroke uses far more fuel than the same HP 4-stroke.
>>Even if a 4-stroke used more fuel, but it doesn't, the reliability alone
>>makes the 4-stroke a lot safer engine to use. If you are looking around the
>>100HP range than there are 4-strokes that run fine on 93 auto gas so the
>>fuel price difference is minimal.
>>
>>--
>>Have a good day and stay out of the trees!
>> See ya on Sport Aircraft group
>>http://groups.yahoo.com/group/Sport_Aircraft/
>>
>>Join "The Ultralight & Experimental Aircraft SiteRing"
>>http://pub27.bravenet.com/sitering/add.php?usernum=2286862090
>>
>>
>
--
Bruce A. Frank, Editor "Ford 3.8/4.2L Engine and V-6 STOL
Homebuilt Aircraft Newsletter"
| Publishing interesting material|
| on all aspects of alternative |
| engines and homebuilt aircraft.|
sticking and burned valves from un-even deposits on the sealing surfaces
of the valve and seat. Now if you have rotators on the valves there
might be a different story. With the materials used in valves and valve
seats, even antique aviation engines 8^)... valve seat recession hasn't
turned out to be a problem. Unleaded fuel may extend the TBO for top
overhauls. If it is a concern, run a tank of LL through every 4th or 5th
fillup.
Jay wrote:
> It's true that the 2 stroke (BSFC .6-.65) will burn "far" more gas
> than the 4 stroke (BSFC .4-.5) but av-gas costs "far" more than mo-gas
> so this offsets the difference.
>
> I was under the impression that the aircooled 4 strokes needed the
> lead for lubrication of valves, etc, so while you might get away with
> burning auto gas, how much wear do you want to put on your engine top
> end? Sounds like people with 4 strokes running auto gas run some of
> both types to keep the top end lubed. For the same capacity tank you
> will have shorter max range on the 2 stroke.
>
> The thing I liked about the 2 stroke engines was the high power to
> weight ratio and small amount of adaptation required from other
> applications (such as Snow Mo). And I realized that your cost per
> mile/hour in fuel was less with the 2 stroke.
>
> The difference in reliability is real but could possibly be offset by
> a redundant power arrangement which would be really nice to have for
> other reasons such as mountain flying or extended flight over water.
> Its common practice to use reducnt systems in hi rel systems, so why
> not the most complicated and critical componant? So save money?
>
>
>
> "Gilan" > wrote in message >...
>
>>A 2-stroke uses far more fuel than the same HP 4-stroke.
>>Even if a 4-stroke used more fuel, but it doesn't, the reliability alone
>>makes the 4-stroke a lot safer engine to use. If you are looking around the
>>100HP range than there are 4-strokes that run fine on 93 auto gas so the
>>fuel price difference is minimal.
>>
>>--
>>Have a good day and stay out of the trees!
>> See ya on Sport Aircraft group
>>http://groups.yahoo.com/group/Sport_Aircraft/
>>
>>Join "The Ultralight & Experimental Aircraft SiteRing"
>>http://pub27.bravenet.com/sitering/add.php?usernum=2286862090
>>
>>
>
--
Bruce A. Frank, Editor "Ford 3.8/4.2L Engine and V-6 STOL
Homebuilt Aircraft Newsletter"
| Publishing interesting material|
| on all aspects of alternative |
| engines and homebuilt aircraft.|