Compression testing

[Stihlbro]

There is more to it than just rpm.

 

[Deets066]

Well thank god for multi quote lol. Glad you're up to speed TM. Now why in the hell does compression hurt rpm's?

Good luck! If he does answer it will most likely be at 2:30 in the morning and his answer will be in the form of a riddle.

 

[huskihl]

There is more to it than just rpm.

We're all ears....

 

[tree monkey]

friction from to tight of a grip

 

[huskihl]

friction from to tight of a grip

D cells or 110?

 

[Deets066]

friction from to tight of a grip

 

[tree monkey]

flesh light

 

[drf256]

Parasitic drag.

There's gonna be a breaking point when you're expending more energy to compress mix than you're getting back out of the compressed charge power potential.

I think it works on all engines, but some better than others, and there's a point you fall off the curve.

Also has a lot to do with air flow. How much compression you REALLY have at rpm is debatable. I would be nice to be able to measure dynamic compression.

This is where port geometry intrigues me. You leave a nice sharp acute exhaust roof when you raise it (after cutting the band) and you will get more dynamic compression than a flatter curve.

And then, compression=heat, so you're getting a less dense air charge then a cooler motor.

So it's all balance, I think.

 

[Deets066]

Parasitic drag.

There's gonna be a breaking point when you're expending more energy to compress mix than you're getting back out of the compressed charge power potential.

I think it works on all engines, but some better than others, and there's a point you fall off the curve.

Also has a lot to do with air flow. How much compression you REALLY have at rpm is debatable. I would be nice to be able to measure dynamic compression.

This is where port geometry intrigues me. You leave a nice sharp acute exhaust roof when you raise it (after cutting the band) and you will get more dynamic compression than a flatter curve.

And then, compression=heat, so you're getting a less dense air charge then a cooler motor.

So it's all balance, I think.

I agree completely, and I'm sure that balance is goin to be different for each engine. But the question is how does one find that balance

 

[drf256]

I think it's gonna be trial and error unfortunately.

I used to want super high compression and did all I could to attain it. Now I'm finding my self thinking of ways to keep it down after mods.

I still think it makes power up to around 240psi. Less on bigger saws that can't cool as well.

No doubt that it's the measure of a tight saw that one can see on the Internet. Side by side, a ported saw with 220psi will create more interest than one with 180. Just how it is in this "bigger is better" world we live in.