Chainsaw Dyno broke down. Tired of spending $ off to the scrap pile it goes

[chadihman]

Well not all the title is true.

The hyd pump is trashed but a new larger displacement pump is on it's way. I tried to test 100 octane no e vs 92 octane e with my 460 but the dyno couldn't pull the 460 below 9500 rpms. I sure am glad I put a hyd filter on the dyno cause I'm sure the pump has spit out some metal. That pump was just to small to hold back a big saw. The higher flow pump will allow me to pull the saws down at lower hyd pressure and should keep everthing a little cooler.

I should have the new pump on Monday 8/12 and then I'll have the results for 100 vs 92 fuel. I will also be advancing the ignition timing to see how that affects power with high octane fuel. I'm thinking the 100 will do little to nothing on my stock saw but 100 should help with a high compression ported saw with advanced timing.

 

[old-cat]

A tip you may already know; Tighter squish makes gas burn faster, less advance required. It also reduces octane requirement. I can't give you numbers, that comes from many hundreds of hours of studying SAE technical papers AND a 1928 research & development book.

 

[chadihman]

A tip you may already know; Tighter squish makes gas burn faster, less advance required. It also reduces octane requirement. I can't give you numbers, that comes from many hundreds of hours of studying SAE technical papers AND a 1928 research & development book.

I was thinking higher octane burns slower and the advanced ignition would help the high octane fuel get a more complete burn.

 

[Magnumitis]

:msp_thumbup: waiting to hear from the "dyno" man again

 

[moody]

Best results you'll find will be 89 no or low E fuel.

 

[old-cat]

I was thinking higher octane burns slower and the advanced ignition would help the high octane fuel get a more complete burn.

Correct. srcarr52 is very knowldgeable.

 

[chadihman]

RK Tek 2-Stroke Heads: Exposing the Myths of High Octane This educated me on octane. The 100 octane fuel I have is GT 100. Well the dyno test wont lie. High octane usually has nothing to do with burn speed. It's just more resistant to detonation. Might help a high rpm two stroke. Higher octane fuel can get the perfect ignition if the engine is set up for it.

 

[old-cat]

RK Tek 2-Stroke Heads: Exposing the Myths of High Octane This educated me on octane. The 100 octane fuel I have is GT 100. Well the dyno test wont lie. High octane usually has nothing to do with burn speed. It's just more resistant to detonation. Might help a high rpm two stroke. Higher octane fuel can get the perfect ignition if the engine is set up for it.

Study the SAE papers. Univ. of Washington Engineering Library is one place to find them.

 

[o8f150]

ok since I am a retire mechanic I am putting in my 2 cents,,,, plain and simple,, the high the octane the slower the burn is,, that's why people go to a higher octane if they have a lot of pinging in their car

 

[chadihman]

ok since I am a retire mechanic I am putting in my 2 cents,,,, plain and simple,, the high the octane the slower the burn is,, that's why people go to a higher octane if they have a lot of pinging in their car

That's not what I was reading but not everything on the internet is true. Slower burning sounds true because an older car without auto ignition advance will ping with lower octane. Higher octane fixes the ping because the burn is slower. Ping is when the explosion in the head is slightly before tdc. The piston actually is trying to go back down before it comes to tdc. Making the ping and reducing power. New cars automatically adjust the ignition timing. Thus the need for knock sensors. Max power is made were the ignition is set right before it pings or knocks.

High octane is needed in high compression engines to prevent pre ignition. Low octane gas will ignite from the high pressure and heat like a diesel engine operates.

 

[o8f150]

That's not what I was reading but not everything on the internet is true. Slower burning sounds true because an older car without auto ignition advance will ping with lower octane. Higher octane fixes the ping because the burn is slower. Ping is when the explosion in the head is slightly before tdc. The piston actually is trying to go back down before it comes to tdc. Making the ping and reducing power. New cars automatically adjust the ignition timing. Thus the need for knock sensors. Max power is made were the ignition is set right before it pings or knocks.

High octane is needed in high compression engines to prevent pre ignition. Low octane gas will ignite from the high pressure and heat like a diesel engine operates.

give the man an A+:biggrin::biggrin::biggrin: now your getting it

 

[blsnelling]

Higher octane fuel does not make more power. It simply allows a higher state of tune that requires higher octane to prevent pre-detonation. If you don't have high enough compression that it's pre-detonating on pump gas, higher octane is not going to help. If anything, it burns slower and will hurt power, minimally. At least, that's the way I understand it. I've never seen any kind of erosion on any of my builds. Generally, I run up to about 200 PSI and timing advance.

 

[chadihman]

If you don't have high enough compression that it's pre-detonating on pump gas, higher octane is not going to help. If anything, it burns slower and will hurt power, minimally. At least, that's the way I understand it.

I disagree a little bit but I'm not a pro at this either. High octane gas is less likely to pre ignite from high compression. High compression can cause pre ignition on low octane fuel because it ignites from the pressure and heat not the spark of the plug.

I cut the squish really far on a meteor 460 kit a while back and it hurt the performance maybe because of detonation. I ran that kit on the dyno and it blew out the rod bearing at the crank. Maybe it was because of detonation and not the aftermarket crank I blamed it on. I might get that jug back on a saw and retest it with GT100.

 

[Nate66n1]

I believe the higher octane fuel will burn longer also. Not just a big explosion and then it's out

 

[blsnelling]

I disagree a little bit but I'm not a pro at this either. High octane gas is less likely to pre ignite from high compression. High compression can cause pre ignition on low octane fuel because it ignites from the pressure and heat not the spark of the plug.

I cut the squish really far on a meteor 460 kit a while back and it hurt the performance maybe because of detonation. I ran that kit on the dyno and it blew out the rod bearing at the crank. Maybe it was because of detonation and not the aftermarket crank I blamed it on. I might get that jug back on a saw and retest it with GT100.

I suspect that the squish velicity was too high on your modded 460. Get that too high, and it'll beat a 2-stroke engine to death, from what I've studied. I suspect that's why others have found that a bigger squish is better when cutting the squish band. High octane fuel may be a bandaid in a situation like this, since it burns a little slower.

 

[RiverRocket]

I always thought that the higher the compression the higher the octane you wanted to use?
I know that's the way it is with a car engine.

 

[CR500]

That is what I thought as well. I always thought if you have an outrageous amount of compression you need the higher octane fuel to not have pre-ignition??? I mean of course running to high of an octane will make power go backwards because you are not able to use the energy in that fuel efficiently.

 

[chadihman]

I think I'll find that the sunoco gt 100 fuel will help somewhere in my dyno tests. Probably a stock saw will have a negative to no power gain. A 200-225 compression saw will probably gain especially with a timing advance. I'm going to test the 100 octane in my stock 460 and in my brothers 460 that I ported a bb that blows a tad over 200 psi. I plan to also advance the timing 2 deg at a time.

 

[Mastermind]

I've found that 100LL doesn't seem to perform as well. :msp_unsure:

 

[dozerdan]

A tip you may already know; Tighter squish makes gas burn faster, less advance required. It also reduces octane requirement. I can't give you numbers, that comes from many hundreds of hours of studying SAE technical papers AND a 1928 research & development book.

What was the compression ratios in the 1928 book ? Most engines of the era are super low.

Later
Dan