READ BEFORE YOU FLAME.

Ok so your probably thinking "V-tech uses a cam and a wankel doest work that way" bla bla bla... BUT I am more interested in the THEORY behind V-tech and how the same operating THEORY could be applied to a rotary engine.

This thread could also be called, a periphreal port street motor :P
I had this idea today as I was thinking about different ways to port a 13B, I was thinking about using a long port runner and a short one to better help with flow and high end power while retaining enough low end to keep idle as well as drivability/noise levels. I concluded that you would still need to seperate the two port lengths on different throttles or your high flow ports would still screw with timing on the low end and would provide no benifit. I thougt about old school double carb setups where the linkage for the second carb was conneted to the opposing side of the linkage to the first carb to make the care more managable.
Then I thought, what the hell, you could also set this thing up to run hydrolically off of oil pressure from the motor or an external pump like V-tech cams use to crossover.

If your not following I will explain exactly what I am thinking, small periphreal ports (Spelling) with a throttle plate installed just past the port. This throttle is closed untill X rpm when it is pushed open either by a secondary throttle linkage or by oil pressure. You can keep the stock or even smaller ports for the low end and then open the secondary peripreal port for a major kick in the *** (4,000 rpm?)
I hope this makes sence as i am not always the best at explaining idea's verbally (Thats why I use solidworks) and dont have the time to model this up right now.

You could also drastically alter top end timing by pushing the peripheal ports further up the housing.

You could theoretically drive this thing around town like a jentleman untill some ahole wants to rev on you :P

 

right... or you could just have a N/a 13b and have the 5th and 6th ports open up...

 

l
o
l

fail.

LOLhonda.com, please dont post again.

 

Ugh...

 

Don't forget the VDI for the S5's.

The RX-8 also has 5/6 ports that open up at a certain rpm, as well as a 3 stage (IIRC) intake manifold that makes it act like it's getting progressively shorter. This is how it makes such decent high rpm power while still having decent street manners.

 

OIC, I was unaware mazda already designed such a system into the motor.

I dont see why someone has not done this with peripheal ports as a three stage.

 

It's because peripheral ports are in the realm of pure race cars where low end torque, emissions, a good, low idle and stuff like that is pretty irrelevant. It would also take some significant R&D to design a system like that to work well and be worth the weight and complexity.

 

ah thank you I knew I was forgetting something

 

What i am talking about is not that complex (At least not for me but I am a ME) You looking at maybe 12lbs or so... Thats after you remove a big chunk of material from the case for the port. Also, if you read my post and you think about it the PP wont be used until higher rpm's anyhow so its not going to affect the low end. That's the entire point of this post.

 

Semi-PP info
You tube of one such beast with gay music.
no real info just pics
its one of two porting options the get tagged as a Semi-PP. you need to be careful using that term as some will assume you are talking about a J / monster port that uses the stock runners but is such a large bridge port that they cut well into the housings. Then there is side fed PP but i will not go into that at this time as there popularity is **** poor and thats for the best.

If it sounds like an incredible new i idea. I put money on it some one from Australia or NZ have done it already. they are all crazy "in the best way" and don't give a damn if it blows up, and thats why we love'em.

 

So, how do the 5th & 6th Ports currently open? What i mean is how are they actuated?

 

vacuum, the ecu opens a vacuum solenoid at a given rpm to allow the vac pot to open the ports.

 

Only since 1981.

 

Not always, the air pump activates the aux ports on the S5's operate. I think the RX-8 is done the same way.

 

Obviously if you had a semi-p port, you would have a standalone. You could easily wire it up so that it would move an actuator depending on anything you want; RPM, load, how many spice girls are still alive, ect. I fear that you are a little out of your league trying to do an actuated semi-p port before you even know how past / present rotary engines work.

 

The first rule of engineeering/research.

Before you want to make something new you need to understand what has been done before you.

 

Ahh. never had one my self and only worked on a turbo. good to know though

 

Take a leaf from the 787b, it used variable intake runners which changed length as the RPM increased, same sort of thing you are talking about but means you get the correct runner lengths for the revs right through the rev range. Also means all your ports are open rather then shutting some off.

 

From an engineering stand point you are off with your statement. A V-tec changes the intake timing via duration and lift, In a 7 this would be port timing and not runner length. The S5 has a variable runner length from Mazda "VDI", The mx6 V6 has three intake lengths and lots of other cars have some kind of VLIM. The 787b uses a Webber TB style intake and has a motor to move the velocity stacks depending on rpm, engine load and other things. It would cost a lot of cash to design and build a computer to figure out the proper stack length and control a servo/stepper motor for this to work as well as the 787b. if you don't give a damn about peak performance just make a dual path intake with two different diameters and length runners.

youtube vid with intake @ 4:50 odd. but still cool.

 

No, i think you'll find i wasnt off with my statement. No where did i relate the variable intake runner length to being like a v-tec motor, "same sort of thing you are talking about" refers to the different intake runner lengths *Nemisis* was talking about. Read it properly!!
As for the rest of the actual variable intake runner length, no it wouldnt cost alot of cash, ever heard of google? Ok its probably not gonna give you completely acurate lengths but im sure there will be a couple of sites that could give you the maximum and minimum lengths you should use, then use a webber carb or injection setup, all you need is the very end of the trumpet to go from the minimum length to the max length so have the trumpet inside another pipe, sealled with a o-ring between the 2, this allows for the extension between max and min, and have a throttle cable linkage which could easily be designed to pull the trumpet out as the revs increase, and have it sprung to return it as the tension on the pedal is realeased and the revs drop. Might not be perfect, but i reckon it'd work, and depending on *Nemisis* level of engineering skill, would be pretty cheap to.

 

did you not read the name of the thread? don't get defensive for not clearly stating what you are talking about. The OP never had a single post asking about VLIM's. As for read it properly, good advice.
OMG i said to work as well as the 787b . There are others out there that have done this off rpm, The best one I've seen had 5 steps. The biggest problem is to make a system that will work better than a dual runner intake a lot of work is needed and the cost will not justify the power gain. If you want to prove me wrong please do I love being wrong about cost effective ways to make power. Till you have a dyno chart I will still say the ends don’t justify the means.
I have designed intakes using the proper length runners. the way I cheat the system is the primary runners are tuned for 54xx rpm the secondarys are 78xx rpm. Tuning is not just length diameter will come into play as well. There is also primary harmonics and sub harmonics.
for one example this is the data for one of the runners
Runner Diameter = 1.5" = Torque = 5448 RPM tuning
Length = 15"
Input length is 15 inches
For 2nd harmonic, RPM range is from 7832 to 9504 with a pulse strength of 10 percent
For 3rd harmonic, RPM range is from 5885 to 6725 with a pulse strength of 7 percent
For 4th harmonic, RPM range is from 4588 to 5131 with a pulse strength of 4 percent
simple online calc
http://www.wallaceracing.com/runnertorquecalc.php

 

Ok, everyone calm down!
I have actually thought about a system similar to what DefYet is desribing. Problem is that throttle angle/position does not determine engine rpm. Furthermore you would need one hell of a range of movement to accomplish a proper tune (look at the intakes in the video) Your much better off using oil pressure for this as well, its also much more reliable and accurate (even more so than using a vacuum like Mazda did with 5th/6th ports) than using a mechanical means to try to actuate a very long sleeve.

I still like the idea of using a three stage oil pressure activated system.

This actually brought about another thought. Do we have conclusive evidence why people lose apex seals?
I was thinking its probably because of the exhaust port location and the seal probably "dips" into the exhaust port and "catches" on the way up, bye bye seal...
Couldn't you just weld in a center piece "spine" into the center to support the apex seal as it travels over this area? Anyone done this? Sorry for all the questions, still learing about these motors.

 

There is plenty of area on the sides of the exhaust port, detonation makes quick work of the OEM cast seals. The RX8 has side port exhaust and they can still pop an apex.

The guys out there that have used adjustable stacks use rpm swithes for the most part. A lot of them feel that the biggest pluss when they where done was cool factor as the power gain is not as big as they thought it would be. The biggest gain from runner length is from an intake with a plennum and i have yet to see a set up like this with plennum.

 

It is not hard to design a variable intake manifold that would work properly. It's not even hard to build it. Mazda used a 2nd gen headlight motor for actuation. The hard part would be fitting it under the hood. You don't need crazy computer programs or even difficult calculations. That part is actually quite simple.

Since the 6 port system changes port timing and increases port area (the equivalent of lift), it is absolutely the equivalent of vtek on a rotary.