This 066 Grenaded........What The Hell Happened???????

[one.man.band]

Separation is normally associated with castor oils, or oils with castor in them. Maxima castor 927 being one of such oils. http://www.maximausa.com/shopping/index.php?main_page=product_info&cPath=2&products_id=13

on the back of my bottle there are some cautions: "Can be mixed with pump or race gasoline. May separate at temperatures below 32F (2C) with some race gasses and AV gas with specific gravity of less than 0.735."

probably not a big deal for most everyone, because we run pump gas. race gas info can be had from the manufacturer to be sure, maybe for AV gas as well. have not seen anyone ever test race gas, even at the track. i have not noticed any separation in pump gas even at much lower temps than 32F. (7F actually).

looked at AV gas... spec. grav varies and probably should not be used w/castor unless you know the SG.

95% of race gasses are fine. (over 0.735 sg). (higher SG number means it burns slower).

-omb

 

[Trx250r180]

I've been using 87 with no additives in saws with 200 lbs of compression and none have shown any damage 5 gallons of mix later and one had at least 75 tanks thorugh it.

but you cheat by using a sharp chain

 

[Trx250r180]

is there any downside to the 92 octain i buy and mix 32 to 1 ? besides it may not be as fresh as the 87 that gets bought more of ?

 

[one.man.band]

curious.... were there any signs of preignition/detonation on the plugs?

-omb

 

[shootingarts]

I've been using 87 with no additives in saws with 200 lbs of compression and none have shown any damage 5 gallons of mix later and one had at least 75 tanks thorugh it.

This is interesting because if my cyphering is right you are at about 12.5:1 compression. Pure 87 octane doesn't cut it with that kind of compression and high RPM engines. Some say that two cycle oil increases the risk of detonation. However octane is the measurement of where a fuel starts to detonate. If two cycle oil increases the risk of detonation then it would reduce octane and the more oil you added the more you reduce octane and increase the risk of detonation. You benefit from increased lubrication but at the cost of detonation and the material removed by detonation often winds up as spatter in the chamber and on the spark plug increasing the chances of pre-ignition.

Since these things aren't happening, it does seem that some two cycle oil boosts octane.

Hu

 

[mdavlee]

The 288 that had machine work was at 200 lbs and had 5 gallons of 87 through it with 927, k2, and R50. I checked the piston last week and it looked like it did when I put it together. It was used bucking and some milling using a whole tank of mix per cut.

 

[Mastermind]

This is one of those things that we've kicked around for a few years now. And over the years the same things always come up.

The shorter the stroke and higher the RPM, the shorter the dwell time. A short dwell time and flame front travel increases from tightened squish can prevent detonation without using a high octane fuel. 87 octane will make more power than a higher octane fuel as well, because the slower burning fuels don't have time to fully burn in the short dwell engines.......think about it.

 

[mdavlee]

Tree monkey is the one that got me thinking about it and trying the 87. I had ran some 110 in a few saws a long time ago and got nothing but red eyes. 93 isn't a big seller but there's lots of places that have e free 87 close to me.

 

[one.man.band]

This is interesting because if my cyphering is right you are at about 12.5:1 compression. Pure 87 octane doesn't cut it with that kind of compression and high RPM engines. ......
Hu

static compression and dynamic compression are two different animals. at high rpm...there is much less charge to compress.


mdavlee....... that my friend is an unbelievably clean piston after thrashings like that!!!

-omb

 

[mdavlee]

static compression and dynamic compression are two different animals. at high rpm...there is much less charge to compress.


mdavlee....... that my friend is an unbelievably clean piston after thrashings like that!!!

-omb

It was tuned richer than I would for normal wood cutting for milling. I think it's at 12.9k or so. The klotz left a little stuff in the combustion chamber but nothing on the piston top.

 

[Mastermind]

Tree monkey is the one that got me thinking about it and trying the 87. I had ran some 110 in a few saws a long time ago and got nothing but red eyes. 93 isn't a big seller but there's lots of places that have e free 87 close to me.

Here is a great article to read......

The part about chamber design is very thought provoking.

http://www.contactmagazine.com/Issue54/EngineBasics.html

 

[tallfarmboy]

Randy, by chance was there any damage to the case? The Flat Top 066 that I bought this summer at an auction had a bad big end bearing on the rod/crank.... The bearing pieces had knocked a dent in the magnesium underneath the counterweights... It wasn't a hole, but it COULD have been if the bearing pieces had hit the case the wrong way under the crank.
I put a little JB weld on the "bump" to prevent any future issues....

Just some food for thought. Take care,

TFB

 

[Mastermind]

We won't know for sure till it has been split and check over well.

 

[shootingarts]

Here is a great article to read......

The part about chamber design is very thought provoking.

http://www.contactmagazine.com/Issue54/EngineBasics.html

Read it earlier. Some things he is right about, some wrong, plus he makes generalizations that don't hold universally true which leaves me a little skeptical about the things he says that I don't know if are right or wrong. Ultimately I don't know how much of what he is saying can be applied to a single cylinder two cycle engine either. The fast burn chamber is interesting but as you know it is only a small component of a system that starts at the air intake and ends where the exhaust dumps. Plus there is considerably more sophisticated computerization to the Caddy's fuel and fire control system. Worth a look but chances are the devil is in the details when trying to export the technology to a chainsaw.

Some old technology that might be interesting in a chainsaw might be dual plugs or multiple spark systems. If faster burn could be obtained then it would make two cycle engines much more efficient. Of course every manufacturer of two cycle engines already knows this and most have millions to throw at R&D. I know they have strato engines now but I got the impression it wasn't the old stratified chamber deal. That created better efficiency way back when. A pain to mass produce too but it wouldn't be that big of a deal at all when considering the time spent porting anyway.

About short dwell times: The old indy cars from four or five decades ago sat there and vibrated. 14000 RPM about like a chainsaw, large bore close to four inches, less than one inch stroke. They ran on methanol which is higher octane than any gas I know of. I still suspect that being able to run 87 octane gas has more to do with what is mixed with it than a short dwell time.

One thing I do wonder about is the article's claim of a universal optimum of peak pressure at 14 degrees after top dead center. I suspect the number isn't right for a single cylinder two cycle but if the pressure curve could be optimized for chainsaws it is possible that one ignition timing and one peak pressure degree could work for pretty much all saws. Would simplify things a bunch then you would "only" have to figure out how to tune everything on the engine to deliver the most pressure possible for the longest time. Piece of cake, right? The theory is always so simple!

Just had a thought how to pick up a two cycle engine by it's own bootstraps, pretty sure it won't work though!

Hu

 

[Trx250r180]

ok then why does my atv ,250cc 2 stroke with 200 psi detonate real bad with 87 octain ,and my 70cc chainsaw with 200 psi wont ? they both spin a chain opcorn:

 

[shootingarts]

ok then why does my atv ,250cc 2 stroke with 200 psi detonate real bad with 87 octain ,and my 70cc chainsaw with 200 psi wont ? they both spin a chain opcorn:

I'm doing my level best to not stir the pot in threads I am in. Sure glad somebody is here to take up my slack!

Hu

 

[Mastermind]

The "fast burn" we are hoping to see in a chainsaw engine's combustion chamber is what we are doing with the wider squish band and tighter squish area. The thinking is that with the machining process we can increase squish velocity, reduce chamber volume, have higher (and therefore faster burning) compression ratios, and still utilize a flat top piston. It has been discussed that this could make the engine more resistant to detonation by design.

 

[Mastermind]

I'm doing my level best to not stir the pot in threads I am in. Sure glad somebody is here to take up my slack!

Hu

I'm enjoying the discussion.....

 

[Trx250r180]

I'm doing my level best to not stir the pot in threads I am in. Sure glad somebody is here to take up my slack!

Hu

i think the answer is cause i'm a fatazz and the engine can't take it ,but i would like a pro opinion

 

[exSW]

ok then why does my atv ,250cc 2 stroke with 200 psi detonate real bad with 87 octain ,and my 70cc chainsaw with 200 psi wont ? they both spin a chain opcorn:

250 cc vs 70cc and timing?Chainsaws are made to run flat out your atv has a powerband that matchs up with your gears.