Saw & Log Tees

Upgrading an Husqvarna 365 to 372XP specs

Discussion in 'Chainsaws and Power Equipment' started by StihlHead, Oct 31, 2013.

  1. StihlHead

    StihlHead

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    From my engineering perspective: what matters in an engine like a chainsaw is HP. HP is a function of torque x revs. You can have all the torque that you want, but if the chain does not move, you will not cut any wood. Similar to having all the chain speed that you want; without torque it will just bog in the wood. So to get power from a chainsaw and chain, you need both torque and revs. What chainsaw designers try to do is balance chain speed with torque to get a saw that cuts well.

    If you look at the saw list that we collectively posted, a lot of the HP gains have been in higher revs from the same displacement engines. The flip side to that has been smog requirements and more choked up mufflers to make them quieter. There are other issues like where the peak torque is in the engine, and how steep the torque curve is, etc. That affects how the saw runs, how fast it gets up to speed, etc.

    I dug up the data on the 191 and did a double take myself. It has the largest displacement and weight, and hence I would have thought it would be the more powerful saw. But that is not the case. My guess is that it is because it is a lower revving saw with a max RPM of 12.5K. To compare, the 200T has a max RPM of 14k. It could also have a choked up muffler, less efficient porting, or a smaller or restricted carb, all which would further reduce the power of a larger displacement engine.
     
    Last edited: Oct 31, 2013
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  2. StihlHead

    StihlHead

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    If you want a comparison of how porting can make a difference in a chainsaw, look at the power differences between the newer Husky 372xp x-torq and the Husky 365 x-torq. They have the same 70.7cc displacement, and essentially the same engine. The difference is in the porting. The 365 has a rated HP of 4.6 HP (same as my 60cc Stihl 036!) and the 372xp is rated at 5.4 HP. You can also see what happens by choking up mufflers in these saws in the US to reduce the HP: In the UK, the same 365x-torq is rated at 4.9 HP and the 372xp-torq is rated at 5.5 HP.
     
  3. Mastermind

    Mastermind

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    And what is different about the porting of those two saws?
     
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  4. StihlHead

    StihlHead

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    The 365 has horizontal baffles in the transfer ports (cast into the removable port covers) that restrict the flow. You can remove the baffles and grind them out and make a 365 x-torq into a 372. At least that is what 'they tell me', as I have not done it myself. Seems odd that they would de-tune a saw that way, but apparently that is the only real difference between the two engines.
     
    Last edited: Nov 1, 2013
  5. Mastermind

    Mastermind

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    You are close. They have a divider (vertical) cast in the transfer cover. There are no differences in port sizes, timing numbers, compression, etc.
     
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  6. StihlHead

    StihlHead

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    Any differences in the low end? Like bearings, rod, case? O/w its $150 less to do a small amount of work to make a 365/72.
     
  7. clemsonfor

    clemsonfor

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    So is there a quick way to turn the 36 5to 372? New covers?
     
  8. Mastermind

    Mastermind

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    There are no differences in the bottom end either. The 365 comes with only one bucking spike, and is a low top. The 372XP comes with dual spikes, roller chain catch, and the HD filter system.

    The cylinder has to be removed to grind out the transfer dividers......and Husqvarna does not sell the covers separate from the jug....
     
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  9. StihlHead

    StihlHead

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    Smells like the EPA is lingering... have to get a Husky/Poulan carb re-tuning tool as well. You could get a HT/HD filter, and the spike, and a 372 sticker...
     
  10. Mastermind

    Mastermind

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    I defeat the limiters on all the ones that cross my bench........it's no problem.
     
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  11. Mastermind

    Mastermind

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    I also use a 346 coil that is limited to 14,100 on these saws. I makes tuning much easier. Set high speed at 13,500 and forget it.

    One of the biggest complaints I hear about the X-Torq is that it has a wanky idle. The stock coil begins to increase ignition timing at a lower rpm that the older coils. This means that if the user has the saw idling at the point of the timing break the change in timing affects the idle and makes it surge.....
     
  12. HittinSteel

    HittinSteel

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    Good things happen when you grind on the 365/372..... don't ask me how I know :smoke:
     
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  13. MasterMech

    MasterMech The Mechanical Moderator

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    Randy, do you use the limited 346 coil because it is limited or because the limiter is set higher than the saw should ever run? I think I got the primary reason is because it doesn't mess with the low rpm timing as much.
     
  14. mdavlee

    mdavlee

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    You shouldn't need to tune any 372 work saw over 13.8k or so. I've not seen one make more power tuned up that high.
     
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  15. Certified106

    Certified106

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    Man, I really have enjoyed reading this thread and picked up some good info! Thanks for taking the time to share with us on here, it's much appreciated.
     
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  16. mdavlee

    mdavlee

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    No problem.
     
  17. MasterMech

    MasterMech The Mechanical Moderator

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    Man I would love to see something like Chadiman's (did I get that right?) chainsaw dyno spitting out HP and torque curves for different saws, ported vs stock, etc.....
     
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