Thread: variable length intake manifold & exup

Maybe the whole ITB's being too long only affects motors that rev past 10k? Thus they need to be shortened by lifting the top part of the ITB up?

Looks like a short set of velocity stacks with a long set that moves into and out of the short set. When the engine revs, the long set lift up out of the short stacks and let air bypass them, effectively shorting the intake tract.

its actually oen piece iirc, it had an accordian looking thing on it that moved when the bike revved up...i have to get a hold of an R1 and take the airbox apart again, its been so long and i cant remember how exactly it worked...that intake was LOUUD

Our very own company has been already using this technology. On the 240sx's with the Ka24de engine. They utilize a similar setup like this with in the intake manifold. The secondary flaps were operated with a vacuum system. This maybe part of the reason why the torque is so good with those engines. I don't know why they did not incorperate this design into the sr20 manifolds though. Team this up with variable compression system and you would have so many variables for tuning that it would be crazy.

to my knowledge the KA had no such thing, my altimas intake manifold was quite basic and didnt have any secondary runners, same engine setup

the QR25 however did

The ka in the Altimas is redesigned 1 being there is TONS... TONS less vacuum lines. Maybe this is true for the Altimas, the vehicle I was referring to was the (S13) Nissan 240sx with the high port style runners.

Yah, the RWD DOHC KA24 Dan and I took apart really surprised us with the dual length intake runner design. I'd forgotten about it.

ahab fails....any way whats your opinion on the exhaust valve?

The way you described it in your first post, it sounds like a scam. I know it works though, so there's got to be more to it than that.

This is pretty much the same system as used on the original FZR1000 EXUP ...It's a small electric motor which activates a butterfly valve at the back end of the collector box. Its moved by cables and these must be kept lubricated or the valve seizes up.

The valve is shut during low to middle RPM and gives you more midrange power from the engine and less noise from the exhaust.

At higher RPM the EXUP valve opens and allows the exhaust gasses to exit quicker, giving the effect of a race pipe.

If you want to change your exhaust, just do the endcan or you will lose the exup valve and the midrange it provides.