Torque.........Defined???

[RandD]

Torque curves

Originally posted by Crofter
Glen, I have to agree about the room for doubt on that data as presented. It could be correct, but nothing indicates that all saws were tested under identical conditions. Temperature, accessories (such as air cleaners, mufflers), length of time tested, etc., could possibly not have been the same for the competition. I think there is sufficient similarity in the relationships to predict that characteristic operation would be similar though.

Hi,

seeing the differences between the measured curves, I can understand your doubt.

But all machines were tested under the same conditions on the same dyno. They were all in serial condition (muffler, port timing, etc.). The measurement according to the EWG/ECE standard assures, that the results are comparable. The influence of temperature, air pressure and humidity is compensated.

The good results of the PS-7900 were also measured by the dlg.
(http://www.dlg-test.de/pbdocs/5050.pdf)

Another point are the expierineces of the users in this forum.
The PS-7900 is known for its amazing torque, especially when compared with the Husky 372.

 

[glens]

Re: Torque curves

Originally posted by RandD
The PS-7900 is known for its amazing torque, especially when compared with the Husky 372.

Yes the 7900 is well-liked.  I'm a little curious (I know there is no comparable-by-displacement saw in the Husky lineup) how that isn't an apples-to-oranges comparison, except that they both weigh the same...

Glen

 

[bwalker]

Rand D, The charts you posted are not dyno charts are they? If they are I am calling BS. I have never seen a dyno chart of a two cycle motor where one is stock and the other is modified in which the mod motor makes more power through the entire power curve. I have seen many of these " charts" like the one you posted that are used to sell high dollar snowmobile mods by to numb skulls by unreputable companies.

 

[ehp]

Boy that is correct on the snowmobiles, i am sure you can remeber back in the late 80's and the 90's when every man had a better set of pipes and made 15 more HP, most made less


in 1989 i had a 650 indy built by a big name shop, stock it had 96 hp. they did everything to it and open pipes , it made 149.96 Hp now , i went down and watched it run on the dyno, it ran great , never missed a beat, so put in the chassis, added another rad to help cool it and race track here we come, well it lasted about 1000 ft on a rader run,

On the dyno it was getting 60 degree water so the motor never got even warm, on the race track it would see 180 degrees which is not hot but with 4 to 4.5 thousand clearance on a cast jug the piston would grow faster than the jug and seize, ended up open the clearance up more and she run good then, even with nitrous on her

 

[dbabcock]

A couple of years ago, I went through 3 cryoed center pistons for the same reason on this "trail ported" unit before I realized what was going on. Next season, I'm going to mount 5 race ported MS290's in a pro stock drag chassis and a 12" diameter chrome tipped sewer pipe exiting below the heat exchangers. When I go trail riding with my buddies, I'll use it as a forwarder to break new trails.

 

[RandD]

Torque curves

Originally posted by bwalker
Rand D, The charts you posted are not dyno charts are they? If they are I am calling BS. I have never seen a dyno chart of a two cycle motor where one is stock and the other is modified in which the mod motor makes more power through the entire power curve. I have seen many of these " charts" like the one you posted that are used to sell high dollar snowmobile mods by to numb skulls by unreputable companies.

Hi bwalker,

this are curves from the dyno!

The difference between the RS and the standard version is not made by powerporting. In such a case I would agree with you regarding the difference.

But you can get more torque over the whole rpm range by reducing the friction.

A good example for this kind of moding is the use of one piston ring instead of two.