Variable intake to lift torque dip

[Hemp Bike]

Thinking about the infamous torque dip. Has anyone had any success with a variable intake manifold?

[Turdinator]

I haven't seen one being sold anywhere but i have a vague memory of there being one on a show car or race car somewhere.

[gramicci101]

Why not just get a header and a tune?

[Captain Snooze]

Have you seen the amount of work that Velox has done so far on their static intake? http://www.ft86club.com/forums/showthread.php?t=82479 As much as I hope it comes to market I wonder about their roi. (Which is none of our business.)
I don't see a variable intake as being commercially viable when a turbo would eliminate the dip and has a known cost & benefit. I mention a turbo because I am guessing a variable inlet would cost more. As @gramicci101 said headers and a tune can alleviate the dip.

[cdrazic93]

the problem is, well theres a few things.

The R&D would be enormous, I'm not sure if there's options on this platform to tune for that variation in manifold length.

Its like using a Variable Geometry Turbo, sure it would give you full boost at idle, but the vanes, cost of the turbo and complexity would make it not worth the amount of time and cost for something that's kind of marginally better than a well designed system.

[troek]

ive seen a hks system over here for our cars that has two inlets, not real sure what its all about though.

[WesleyG]

Originally Posted by gramicci101

Why not just get a header and a tune?

Im with this guy, why complicate things.

And the intake lengths and diameters would have to be carefully selected or calculated using some rocket science

[rx3]

You shouldn't worry too much about the torque dip, since one can almost always avoid it. (I hardly get the engine to fall into the torque dip at a slalom/autocross event).

I'd rather have shorter intake runners to get more torque and power above 5000 rpm (and a shorter final drive with it).
Like this Renault Clio:

[serialk11r]

Lol, a Camry has variable length intake. In principle it's not that hard, but adding valves and piping is pretty annoying for the gain you get.

You could connect the pairs of intake runners some length down from the plenum and put a butterfly valve in between that switches at 3500rpm. That would increase the resonant frequency of the pipes and move the powerband up a little.

[Jesse36m3]

My previous e46 330Ci zhp had a variable intake system using some type of solenoid with a flap to block off part of the intake runners below a certain rpm, then open up above that specified rpm. Maybe I got that backwards. I don't know. All I know is that it broke, I fixed it, and it was money wasted to even have in the first place IMO. No need to complicate things on an already simple engine. Like previously mentioned, a nice header and tune will get that TQ dip out.

[Andrew025]

Originally Posted by Jesse36m3

My previous e46 330Ci zhp had a variable intake system using some type of solenoid with a flap to block off part of the intake runners below a certain rpm, then open up above that specified rpm. Maybe I got that backwards. I don't know. All I know is that it broke, I fixed it, and it was money wasted to even have in the first place IMO. No need to complicate things on an already simple engine. Like previously mentioned, a nice header and tune will get that TQ dip out.

The Prelude had one as well.
This guy is taking about a manifold though.

[Jesse36m3]

Originally Posted by Andrew025

The Prelude had one as well.
This guy is taking about a manifold though.

It was built into the manifold.

[burdickjp]

Variable length intakes were made mostly redundant with the implementation of continuously variable intake can timing.
Our cars have variable cam timing on intake and exhaust, so a variable length intake probably wouldn't offer much benefit.

[serialk11r]

Originally Posted by bur****jp

Variable length intakes were made mostly redundant with the implementation of continuously variable intake can timing.
Our cars have variable cam timing on intake and exhaust, so a variable length intake probably wouldn't offer much benefit.

Not true at all. Being able to time intake valve closure precisely lets you capture the maximum pressure (and thus mass) of air in the cylinder, but tuning runner length is what maximizes the amount of air entering the cylinder in the first place at any speed. Both VVT and variable length intake are commonly found on engines.

Think of it as a sprocket pulling a chain back and forth (representing the waves in the intake). Tuned VVT is like putting a ratchet mechanism on it, but the runners control the amplitude of the sprocket's movement.

The engine's breathing is a system that works together, all the pieces have influence.