So i've been pickering around with Variable length intakes and have a few questions. I know that the 787 had a design for it which was really bulky and I can't find great pictures of how that worked anyways.

1) If an injector was mounted in such a way to move with the intake would that distrupt the fuel spray pattern?

2) With a varibale intake such as that, would the resulting torque curve be more flat or be like declining line?

3) In intake difference (forgetting about variable stuff right now) say between an IDA, and a sidedraft style on the same engine with the exact same carb being used, what and where would be the difference inbetween the 2 intakes as far as HP, torque, and what rpm bands. I understand the side would provide more torque down low but less HP in the top, and visa versa, but how much more and less?

4) If making the intake length increase increase/decrease fast (say something like mechanically hooked with the gas pedal) would that fast action distrupt the air flow/ slow it down?

Just trying to see if its really worth pursuing this. I might be able to use the local university's faculty to do some testing but thats just a might.

 

The Norton NRV-588 racing bike uses a continuously adjusted Variable Length Intake on a Rotory engine. Being fully fly by wire, it looks like the intake length is adjusted using a lead screw type linear actuator.




Sorry I can't help answer any of your questions.

 

The variable length intake trumpets would probably be a lot less effective on a side port, and probably not worth the time and money required to attain them. If you had a peripheral port (do you?) then that's a different story.

 

Intake runner length is important on any engine regardless of porting style. VDI on the S5 and Renesis intake manifolds makes the engine think that there is a different length intake manifold. A valve opens to shorten the return pulse at different points. This simulates different runner lengths even though physically they don't change. Of course they only have 2 positions but this is far simpler to fit in a small space than trumpets. I don't see where you can get them and still have enough room for them to get long enough. Too many people have a tendency to make runners far too short.

 

Rotarygod ... anyways you can try to help me out with my specific questions above? I know how good your intake theories are.

 

http://www.deanq.com/stuff/rotary/r26b_paper.doc
http://cp_www.tripod.com/rotary/pg03.htm

Yes

Oscillating with higher valleys but lower peaks than a fixed intake. The R26B lost about 30 peak hp with the variable intake.

Sorry, I don't know.

Yes, due to relative motion.

 

So what the point of people using variable length intake then from those points? If it was mechanically hooked to the pedal it would when ever its at WOT, it would basically have to act as its shortest length (unless you base it by load value ie. hook up a map sensor or something and have that control a motor of sort to base lenght by load on engine which I guess would make more sense) but even then its if you're not going to gain much usuable hp if at all?

Now i know I asked about peak HP and r26b lost 30 peak Hp, how much did it gain in the midrange? ... would be nice to see a dyno graph of such thing. Or atleast a comparision of 2.

 

The first question I have before we get too far into this is what engine, engine management combination are you wanting to try this on? Fuel injection, carburation, street engine, race engine?

 

i tried it myself using step motors, i am still having problems with it, i cant get them to react quick enough to rpm changes so t is not as efficient during gear changes.

 

The engine itself I'm not sure what it will be but probably not a P-Port ... maybe Bridge or large street. More street/track engine more towards track.

It will be fuel injection with a standalone ecu. So FI it will be for simplicity of control.

BlueM - What are you using to control the Stepper Motor for it? I would image if you can add a simple program to a megasquirt or such to have it based on RPM, load, and TPS position like you control injectors you might be able to pull it off like that. Just a thought though.