EXUP valves

[steviem]

I dunno why I just thought of this, but on Kawasaki sports bikes (and others probably), they have these EXUP valves that help change the way the engine performs at different throttle positions, so if your full throttle it completely unrestricts airflow out of the exhaust and performs better, but when you aren't booting it, the valve restrictes airflow a bit and quietens the exhaust down a bit.

Now what I want to know, is why hasn't this been implemented on cars?

Also there is another thing that works similar to this, but is for inlet air, where it effectively changes the length of the trumpets on throttle bodies, so at different revs it makes the engine better for torque or better for bhp, again, why doesnt this feature in cars?

God, i need to use my brain constructively, I really am thinking of stupid things at the mo...

[Thom89]

I think your taliking about Variable valve timing, and its been around for years! most manufactures have there own concept of this idea, and tends to be at the performance end of the market, look out for badges on cars.. V-tec, V V T, V V R... that sort of thing..
Tom

[steviem]

no, im not

its a valve in the exhaust system

it stands for 'Exhaust Ultimate Powervalve'

[Thom89]

Sorry mate, I posted, and then re-read what you were saying.. your dead right, it unrestricted the exhaust flow to give a broader power band, some cars do have this, BMW's, Aston Martins have a vacuum operated valve on the rear "box", Its probably down to economics that more cars aren't built with them, and also the cost of replacement, when they drop to bits.. not sure though, if the bike method is the same as the car method, but certainly in the same ball park!
Tom

[...joe]

i was going to say aston martin db9's have them. cars are always a compromise, they either are all out noise machines or economy driven eec crap things!

[>>Mart<<]

ferraris have a same sort of thing in the exhaust system somewhere when you push the race button all hell breaks loose