power valve

[martinr]

has anybody tried rigging up an exhaust power valve would there be any point any advantages

[RICSPEED]

mb had a bash at it but its a lot of work but i cant recall the exact reason he took it off his pushpac

[Wayne Miller]

has anybody tried rigging up an exhaust power valve would there be any point any advantages

Hi Martin,

I haven't made my own powervalve cylinder as yet but I do have a rotax polini 153cc pv lc barrel on my smallframe and have been looking at a few barrels and thinking about converting one. I have a few rotax barrels too that use the blade type powervalve and think that this would be the easiet type to recreate on a TS/RB/Falc cylinder. You would need an ignitech powervavle control unit, an rd350 servo, an rs125 powerblade and a cylinder of your choice. It would require a skilled hand but it looks like it could be done quite easily. in simple terms : porting tools to cut a slot into the barrel, cnc a mounting plate, weld or bolt on plate, fit powerblade.

Advantages

Fixed height exhaust ports only produce power in a narrow powerband, If you raise the exhaust port on a road bike you can lose you bottom end power. This isnt a problem for someone who has raised the exhaust port and is sprinting or racing as there usually riding at max rpm and are always in the powerband. With a powerblade you can raise your exhaust port up high and then slot in the powerblade to fool the cylinder into thinking that you have a lower exhaust port height so that it still has power low down. You have your blade pushed in to create the low port height and use you low rpm power then once you start getting into the range where your raised port height starts to make power your slide your powerblade out, raise your exhaust port height/area and start to use the higher rpm power. basically you have the best of both worlds, low port height to get your low rpm power and then a raised port height to get your high rpm power.

Once you have your cylinder completed its time to set up your ignitech system. simply whack it on a dyno with the powerblade open so that your exhaust port is raised. open up the throttle and let her rip. Study that graph to find out where your power kicks in and note the rpm. Once you have your rpm set your power blade to open at the desired point. Simples

I think that makes sense but I have had a couple of glasses of vino tonight, best of luck and look forward to seeing pics of you having a crack at it

ps there are other types of powervalves I just thought that this was the easiest type to try first

[Muttley McLadd]

Isn't the main problem with doing it on a Lambretta the space to do it? ie, there's not much between the exhaust port on the barrel and the ground.

[RICSPEED]

http://www.facebook.com/#!/media/set/?s ... 4324108948

loooks like an aprilia one

[Stampede]

No, it´s a Rotax Rave.

[RICSPEED]

No, it´s a Rotax Rave.

yeah aprilia 125 rs ...ie .. rotax 122 engine

diddnt have time to re read marks fb right up but there was a bit about a melted piston

[Stampede]

[martinr]

does the valve have to be right at the exhaust port or could it be some how in the exhaust stub 10 or 20mm from the port

[sean brady scooters]

it really has to be right on the piston to control port timings ,one lower down say 10/20mm wouldnt control the exhaust port opening duration but would just restrict flow