Cc or hp

[spudulike]

Do you remember that film with Tom Cruise when he was young ? His parents went away and he had a mega party in the house culminating in thrashing and trashing his Dads Porsche . After the carnage he said " Porsche , there is no substitute ! "

 

Unfortunately, I am an old fart like you Andy so YES, I can remember Risky Business.....and Top Gun:thumbup:

[SawTroll]

And Torque is more crucial to performance than either HP or CC.

But at this time of night I cannot explain why!

 

Power (hp) is a product of torque and rpm, so torque isn't a seperate factor.

 

Low end (max) torque is usually not interesting, as the cutting will be slow anyway at that point. It matters only if your saw is way too small/weak for the task at hand.

[TimberCutterDartmoor]

Power (hp) is a product of torque and rpm, so torque isn't a seperate factor.

 

Low end (max) torque is usually not interesting, as the cutting will be slow anyway at that point. It matters only if your saw is way too small/weak for the task at hand.

 

In a constant volume cylinder yes, not constant pressure one.

[GardenKit]

Certainly, torque is not a separate factor, but it is an important factor.

Hp is the product of Torque x RPM divided by 5252, but thats not important.

 

What is important is how torque helps the chainsaw user.

 

As an extreme example take two 5hp saws. One modern saw developing 5HP @ 12000rpm, and an old shool Mac or similar developing 5HP @ 6000rpm.

The old saw is producing twice the torque at half the speed.

 

This indicates that the torque of saws can be vastly different, but how is torque of value to the user?

 

As long as the higher revving saw is able to work whilst holding on to its revs it will outperform the slower revving saw, but if the revs drop off in heavy work the power will drop significatly whilst the slower revving (high torque saw will be able to keep plodding on.

 

Generally high speed, low torque engines will be short stroke engines with large bores, whilst low speed high torque engines will be long stroke with a smaller bore.

 

Torque, and therefore HP, varies between saws of the same CC due to influences such as air flow (port design) and compression ratios.

 

Hence the 'porters' ability to increase power and torque through port mods and squish.

[TimberCutterDartmoor]

Generally high speed, low torque engines will be short stroke engines with large bores, whilst low speed high torque engines will be long stroke with a smaller bore..

 

Precisely. "Under square" vs "Over Square". I know which I prefer.

[GardenKit]

Precisely. "Under square" vs "Over Square". I know which I prefer.

Haha, terms which we do not hear much these days.

 

Thats why I had a straight six 'over square' Triumph 2000 rather than the 4cyl 'square' Rover.

[Pinkfoot]

My brother is square with a lot of talk.

Think it may be the fuel he uses..

[GardenKit]

My brother is square with a lot of talk.

Think it may be the fuel he uses..

very good:biggrin: