Noob Question - Variable Valve Timing Equivalent?
 

I know rotaries don't have pistons and valves (duh), but I'm curious if there's anything in a rotary motor (or anything that could be done to or added to one) to have the same effect of variable valve timing?

While I was aware that VVT is used to keep the engine at optimal performance throughout the rev range, I was watching a Best Motoring video on the HKS R-34 GT-R (http://videos.streetfire.net/search/...B545DC5535.htm), and it was interesting b/c HKS developed an electonic variable valve timing system for the RB26, advertising that:

1) Low to mid-range power and speed is retained while still increasing power with cams and bigger turbines.
2) Even with high profile cams the engine maintains smooth idle and good emissions.

I guess I never thought of VVT being used to compensate for loss of low-end power/torque when using a large single turbo etc. So I'm wondering if there's anything we can do on a rotary that would have the same effect...help salvage some low end power/torque in the face of a large single? (Other than the "run a properly sized turbo" answer ;))

Thanks
~Ramy

variable valve timing usually is just that, we have ports, you cant vary the speed of the rotor as it passes them really to my knowledge. next down the line in the intact tract and the closest possible plausible option for this effect would be adjusting the second and third throttle plates, which we already have, and i believe they are cam driven ala throttle cam.
now i have yet to really tear into my throttle body on my fc, i am rotary newb at this point. but id suggest looking into how that actuates and go from there...although i believe it's already built in to some extent.

you want more power? port your engine, upgrade your turbos, upgrade your airbox and exhuast. if you want variable timing go buy a honda!

Actually the rotary community used variable "valve" timing before the piston community. On the N/A 13bs the 5th and 6th ports are controled by a pnumaticly actuated sleeve At about 3500+ RPM. When this sleeve rotates this opens up the larger (size and timing) ports. By doing this it accomplishes the same as the V-Tech. Increase of charge velocity, more overlap: which all equates to a phrase coined as enertial supercharing. Long story short more power over high RPM Range and more torque down low.

Please leave the ignorant comments to yourself. I don't need you telling me how to mod my FD. If you have something useful to contribute, by all means, do so. Otherwise, curb the sidecomments.

Marek...wow...you're right. :) I remember hearing about the 5th and 6th ports on the 13Bs. But as you mentioned, those were the NA's. Is there a specific reason why Mazda ditched that design on the 13B-REW? Is it something that could still be used in a FI application?

Thanks
~Ramy

Turbo doesn't need it. :D


-Ted

Ted, assuming the turbo is properly sized, yes. But for example, lots of these high hp FDs have literally NO low end. I'd think that would be a great application for them, no?

~Ramy

There's a discussion at the end of this thread over in rx8club, where rotarygod explains how a variable intake works. kinda similar..

http://www.rx8club.com/showthread.php?t=83752&page=4

http://www.rx8club.com/attachment.ph...chmentid=73024

Aseras, thanks for the link :) I dropped RG a PM :)

~Ramy

If you put it that way, then it would make sense...
I can't imagine the R&D costs though... :(


-Ted

Variable length intake?
If so, this really has nothing to do with the thread.

VVT (Honda VTEC / Mitsubishi MIVEC) has to do with intake and exhaust (valve) timing.
Mazda's 6-port system on the FC's were about as close as you can get to an equivalent.


-Ted

yes, but the factory didnt do that, you did.

having played with the system for years, it basically adds power under 2000rpm, and who cares about that?

to gain something you must lose something.

1) *I* didn't do anything. I have stock twins. 2) And your point?

While that may be what the stockers do, I'm talking about using the *concept* to engineer something to give power for say, under 3,500 - 4,000 rpm.

If everyone thought like that, HKS wouldn't have developed the electronic variable valve timing for the RB26, now would they? I think they beg to differ w/ you on that point ;)

~Ramy

Ramy, I'll e-mail you soon. I haven't forgotten about you. I've just been really busy.

Thanks RG :)