Dolmar 6100 just finished, pretty impressive!

[Chris-PA]

Im still just trying to get my head around how hes allegedly getting 15k rpms on a saw thats limited to 13.8 from the factory. Unless he was able to make a coil from another saw work (which is possible of course), i just dont see how its possible. Rpms on a limited coil saw will jump around a little up past the limit, but ive just not seen them go more than 1k rpms past the limiter...

As I wrote, with the short bursts it was hard to be accurate, so maybe that's all it was turning, or maybe it was overshoot. But the saw cuts at 10k so what does it matter? Randy's ported 6100 was cutting at 12k when the carb was going lean, and did seem to be limited to about 13.8k, but again what does the limited rpm matter?

There is a lot of fascination with WOT rpm numbers as if higher were better, but on modified saws it means nothing. Similarly limiters as if they were a bad thing, but if it's not limiting the cutting rpm why the concern? It's like wanting a 200mph speedometer when you can't get to 120. All that matters is rpm under load, and most work saws won't be near 13.8k then.

 

[cus_deluxe]

As I wrote, with the short bursts it was hard to be accurate, so maybe that's all it was turning, or maybe it was overshoot. But the saw cuts at 10k so what does it matter? Randy's ported 6100 was cutting at 12k when the carb was going lean, and did seem to be limited to about 13.8k, but again what does the limited rpm matter?

There is a lot of fascination with WOT rpm numbers as if higher were better, but on modified saws it means nothing. Similarly limiters as if they were a bad thing, but if it's not limiting the cutting rpm why the concern? It's like wanting a 200mph speedometer when you can't get to 120. All that matters is rpm under load, and most work saws won't be near 13.8k then.

I would agree with that with the exception that WOT rpm on a modded saw is a good indicator of how well the ports are all working together and can give feedback on how a builder goes about doing different thinggs. You are right that it tells nothing about performance at different rpms and under load. My issue with this thread is the unsubstantiated claims regarding the performance of this particular saw. Declaring that it turns 15k rpms, when the saw is limited to 13.8k from the factory should require some kind of proof no? Declaring that he “figured out how to keep the benefits of the scavenging deal in the muffler” with no explanation of wtf hes talking about. Maybe hes right, but if hes “figured it out”. Then he should be able to explain.
Still curious on the gapless ring setup, a couple grainy pics of “what does appear to be) 2 rings in one groove is cool and all, but rings are pinned in place for a reason as far as i know, and relying on combustion pressure to hold rings in place doesnt work anywhere else so how has he managed it here? Im not saying he hasnt done what hes claiming, i just need a little more documentation and info is all.

 

[Chris-PA]

I would agree with that with the exception that WOT rpm on a modded saw is a good indicator of how well the ports are all working together and can give feedback on how a builder goes about doing different things.

Mostly it's just the carb, which delivers an increasingly rich mixture as the rpms increase (at WOT). At first it misfires (4-stroking), but can still rev higher until at some point it's too rich to rev any further. The particular rpm it makes it to is some combination of the characteristics of that engine and that carb. Mods change that rpm, and the relationship between WOT rpm and the fuel mixture under load, so it's no longer useful as a tuning guide. You can only tell if you're richer or leaner on that modded engine, but no longer know what the mixture will be under load, so you have to tune it in the cut. It could rev great WOT and fall on it's face under load.

Still curious on the gapless ring setup, a couple grainy pics of “what does appear to be) 2 rings in one groove is cool and all, but rings are pinned in place for a reason as far as i know, and relying on combustion pressure to hold rings in place doesnt work anywhere else so how has he managed it here? Im not saying he hasnt done what hes claiming, i just need a little more documentation and info is all.

The ring mod is what he showed, he's hoping it won't spin but has not made any claims about longevity and plans to tear it down and check. It would make me nervous, but it's running. He's got a decent cylinder pressure at a couple of rpm, but here again is a number people put too much weight on. How has the combustion pressure at 10k changed with this mod, with much higher pressures and only a couple of milliseconds to bleed off? No way to know.

None of the other mods to this saw were described in any detail.

 

[cus_deluxe]

hows about that muff mod chris?

 

[sunfish]

Cuz & Chris, you both make good points!

I use WOT as a starting point to see how high a modded saw will rev and still 4 stroke.
Then put a load on it and adjust for best power in the cut.

The muff mod does look f-ed up, but I don't know what's going on there?

 

[cus_deluxe]

Mostly it's just the carb, which delivers an increasingly rich mixture as the rpms increase (at WOT). At first it misfires (4-stroking), but can still rev higher until at some point it's too rich to rev any further.

so ur tellin me carb adjustment has more to do with max possible rpms than port timing?

 

[cus_deluxe]

Im not trying to argue with you chris, i just wanna see more. I wanna see a tach on that thing that says 15k. I wanna hear how he knows hes kept “the benefits of the scavenging deal in the muffler. Its not this guys first thread of complete nonsense.

 

[Chris-PA]

hows about that muff mod chris?

I'm pretty sure that's a different saw - I don't know much about Dolmars but I thought that SLR thing was a lame attempt to meet emissions without a cat or strato. I didn't think they used that on the strato 6100? Anyway I ignored it because there is no explanation, and based on my understanding of how the SLR was supposed to work, you cannot have it function and have it flow well.

so ur tellin me carb adjustment has more to do with max possible rpms than port timing?

Absolutely. You adjust it with only the H screw on the carb, and if fuel mixture were not the primary variable that determines WOT rpm then this would not work well.

The fuel mixture of these carbs varies wildly, getting massively richer as rpm (air velocity) increases. The relationship of mixture to rpm may be a complex and non-linear relationship, but it is repeatable on a mass produced saw. So the factory works out the correct mixture at working rpms under load, and then sees what WOT rpm it gets to. Then if you duplicate that mixture / WOT rpm setting, you will have duplicated the mixture setting they worked out under load too. It is only a means of telling people how to duplicate the factory setting (a lot more convenient in a shop setting than tuning in the cut), but if the saw is modified it's all out the window.

Just about any cheap saw engine will rev to the moon with no load and a correct mixture - it tells you little about how well the ports work.

 

[cus_deluxe]

I'm pretty sure that's a different saw - I don't know much about Dolmars but I thought that SLR thing was a lame attempt to meet emissions without a cat or strato. I didn't think they used that on the strato 6100? Anyway I ignored it because there is no explanation, and based on my understanding of how the SLR was supposed to work, you cannot have it function and have it flow well.

Absolutely. You adjust it with only the H screw on the carb, and if fuel mixture were not the primary variable that determines WOT rpm then this would not work well.

The fuel mixture of these carbs varies wildly, getting massively richer as rpm (air velocity) increases. The relationship of mixture to rpm may be a complex and non-linear relationship, but it is repeatable on a mass produced saw. So the factory works out the correct mixture at working rpms under load, and then sees what WOT rpm it gets to. Then if you duplicate that mixture / WOT rpm setting, you will have duplicated the mixture setting they worked out under load too. It is only a means of telling people how to duplicate the factory setting (a lot more convenient in a shop setting than tuning in the cut), but if the saw is modified it's all out the window.

Just about any cheap saw engine will rev to the moon with no load and a correct mixture - it tells you little about how well the ports work.

So i sent my 262 to a reputable builder. He modded the saw. Prior to me sending the saw to him, the ideal mixture as you have described resulted in a max wot rpm of around 13,500. Upon return it reaches close to 15k with out leaning it out completely til it screams. Are you telling me he adjusted the carb and that had more of an effect on that max rpm than all the machine work and porting?

 

[cus_deluxe]

If so this is a big deal. Lots of guys are gonna want there money back from all the saw builders that used to hang out here. LOL

 

[Deleted member 117362]

Im not trying to argue with you chris, i just wanna see more. I wanna see a tach on that thing that says 15k. I wanna hear how he knows hes kept “the benefits of the scavenging deal in the muffler. Its not this guys first thread of complete nonsense.

Ditto! Put a tach on it and make us non-believers apologize and shut up. Easy right!

 

[cus_deluxe]

saw - I don't know much about Dolmars but I thought that SLR thing was a lame attempt to meet emissions without a cat or strato. I didn't think they used that on the strato 6100? Anyway I ignored it because there is no explanation, and based on my understanding of how the SLR was supposed to work, you cannot have it function and have it flow well.

I chose not to ignore it. It was posted in his thread that is specifically about a 6100 that he modified. I guess i assumed it was the same saw, simce the addition of that pic to the thread blended seamlessly into his description of how it blows out his 7310, amd makes his 461 redundant. Making unsubstantiated claims is my problem with this thread. Period.

 

[Deleted member 117362]

Listen to Mr. Evans Dolmar 6100 in his video where he compared it to a 357xp and my 562xp. There you will hear saws running above 14,000rpm and a 6100 that is not stumbling in the cut. And yes I know mine was slower, but a real smooth smile maker.

 

[Chris-PA]

So i sent my 262 to a reputable builder. He modded the saw. Prior to me sending the saw to him, the ideal mixture as you have described resulted in a max wot rpm of around 13,500. Upon return it reaches close to 15k with out leaning it out completely til it screams. Are you telling me he adjusted the carb and that had more of an effect on that max rpm than all the machine work and porting?

Did you pay someone to increase the max no load WOT rpm? I'm guessing rather you were after more rpm under load, and probably got that. The increased WOT rpm is just a consequence of the changes, not a goal, and it's particular value means little as it's a different engine now. You cannot evaluate the porting job based on that WOT rpm at all.

I did not write that fuel mixture was the only thing that determines what that WOT rpm is, but that it is the primary thing. Without knowing what changes were done to the engine and/or carb who can tell where it should run now? It would be quite possible to modify the porting such that really high rpm flow were enhanced and WOT rpm went up, but to actually lose power at cutting rpm and have a saw fall on it's face down low.

My main point was that people assign a lot of meaning to this WOT rpm value where little really exists. Anyway, this is beating a dead horse now so I'm done.

I chose not to ignore it. It was posted in his thread that is specifically about a 6100 that he modified. I guess i assumed it was the same saw, simce the addition of that pic to the thread blended seamlessly into his description of how it blows out his 7310, amd makes his 461 redundant. Making unsubstantiated claims is my problem with this thread. Period.

It was pretty clearly not on the 6100 in the video.

 

[cus_deluxe]

Did you pay someone to increase the max no load WOT rpm? I'm guessing rather you were after more rpm under load, and probably got that. The increased WOT rpm is just a consequence of the changes, not a goal, and it's particular value means little as it's a different engine now. You cannot evaluate the porting job based on that WOT rpm at all.

I did not write that fuel mixture was the only thing that determines what that WOT rpm is, but that it is the primary thing. Without knowing what changes were done to the engine and/or carb who can tell where it should run now? It would be quite possible to modify the porting such that really high rpm flow were enhanced and WOT rpm went up, but to actually lose power at cutting rpm and have a saw fall on it's face down low.

My main point was that people assign a lot of meaning to this WOT rpm value where little really exists. Anyway, this is beating a dead horse now so I'm done.

It was pretty clearly not on the 6100 in the video.

I see now that there is no way for you to accept any other point of view than ur own and you jus argue for the sake of arguing. I guess we must agree to disagree sir.

 

[huskihl]

Dibz on the now seemingly useless 461

 

[cus_deluxe]

There is a lot of fascination with WOT rpm numbers as if higher were better, but on modified saws it means nothing.

Sorry jus re-reading some of the posts. Apparently you know something that every other saw builder doesnt. Never heard of anybody aiming for lower peak rpm?...i try to stay away from generalizations, but here goes: Generally, when the sharp spinny thing goes faster, it will cut faster.

 

[cus_deluxe]

You cannot evaluate the porting job based on that WOT rpm at all.

I would say this is false in almost every circumstance. My first (only) ported saw was a complete failure. I lost over 1k rpms from stock form. I made mistakes that led to poor performance, that was immediately noticeable due to the lack of top end rpms. I just went and took part in a build off where a lot of guys didnt F there saws up (haha) amd lemme tell ya, that ones that spun that chain faster, cut faster. I fully understand that most saws that make extreme rpms, make their power in a very narrow rpm band (pipe saw for example), and that wot rpms isnt the end all, but to say it has nothing to do with the overall effectiveness of the job done is just ****ing ridiculous.

 

[big t double]

What's the deal with that abortion hanging off the side of the muffler...is it stock? I'm not familiar with dolmars. I'm also not good at reading.

 

[r black]

What's the deal with that abortion hanging off the side of the muffler...is it stock? I'm not familiar with dolmars. I'm also not good at reading.

homemade expansion tank ? no they don't come stock that way and you should give a 6/7series a shot...........