All this power valve talk . . . . .

[owenbstory]

I'm thinking that there has got to be a way to trick the ecu into seeing what it needs to see, feedback wise. And make the power valves open and close more like the pro style? Maybe a spring and mechanical linkage? What's the draw back of trying to do this?

 

[BILTIT]

Problem i see is the test it does on startup, tough to mimic this with a spring and linkage.

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[owenbstory]

Maybe just leave the servo hanging there hooked up so the ecu thinks all is well?

 

[owenbstory]

I'm just reading through the other posts and other peoples experiences. It seems that when the mechanical cable going from the servo to the valves is "broken" or unhooked the ecu doesn't know it. The engine just doesn't rev or pull like it should. Sounds like there isn't any check engine codes for a bad cable. I'm thinking of a throttle cable something like the old mechanical oilers had. A block part way down that tees so your flipper pulls the slides and the oiler at the same time. In this case it pulls the valves open instead of an oiler. Leave all the factory electrical intact, servo relays etc. Then just figure out the right ratio of travel for the powervalves per pull of the throttle cable. Anyone try running these engines with the valves wired open yet? Used to work in the M1000 days!

 

[simnil]

So has anyone dynoed the engine with valves locked at fully open?

Wasn't that an old A-C trick on the F7?

I for one doesn't really understand why a snowmobile engine needs the exhaust valves. With a proper clutching the potential bottom end gains from the exhaust valves should not be needed or be so small that it wouldn't be worth it?!?!?!?!
My personal guess why they are there is that the valves help reduce sound at lower revs.

 

[Teth-Air]

So has anyone dynoed the engine with valves locked at fully open?

Wasn't that an old A-C trick on the F7?

I for one doesn't really understand why a snowmobile engine needs the exhaust valves. With a proper clutching the potential bottom end gains from the exhaust valves should not be needed or be so small that it wouldn't be worth it?!?!?!?!
My personal guess why they are there is that the valves help reduce sound at lower revs.

My understanding is that when you reduce exhaust flow at low rpm's you increase torque. Like a single pipe engine v.s. a dual pipe engine. The single has more torque at low rpm but the dual has hp at high rpm.

 

[ndC7M8]

The M1000 benefited from having the valves wide open but I never saw a great gain on my Crossfire 700. I really think some of these things nowadays are proven to work & there isn't enough call for someone to come up with a fuel map & clutching for an exhaust valve delete. Don't think you would get a worthwhile gain from it because the engine is built to work with them. I'd assume they hold some heat in the compression chamber at lower rpm for a better burn.

I just think of my powervalve deletes on my CF7, then I did the Polaris style pressure operated exhaust valves later. I don't think it ever ran right just being fooled into thinking it was. I think you would need to actually tune a machine to run properly without exhaust valves

 

[simnil]

My understanding is that when you reduce exhaust flow at low rpm's you increase torque. Like a single pipe engine v.s. a dual pipe engine. The single has more torque at low rpm but the dual has hp at high rpm.

Yes they are supposed to help bottom end power, but a properly adjusted CVT doesn't need that as much as a vehicle with a gearbox does.

Oh well, all of them have the valves now anyways but I genuinely think they are overrated and put there for another reason than they advertise..... anyone got any tin foil I can borrow