variable length intake with ITB's

[Guest TeamNissan]

telescoping intake manifolds???

Just look through the FSAE web sites for much less leaky designs...

There are ways to make a manifold variable than having the runners actually extend and shorten.

If you have a long and a short manifold going to the same cylinder you can creat any length in-between the two lengths by modulating the butterfly on the short runners. Much more reiable/less leaky and it can actually work with boost...

 

I may try to rig something up with my LD28 manifold to be a variable intake for my L26.

 

 

We have been talking about the other set up options already. For the rt your going I think the LD28 mani is a great start to work off of. I cant wait to see.....

 

I'm thinking by this point all the designs are sound, we all just have to pick one for our own application. Me personally, if I try its going to be telescoping. Use the dizzy for the rpm signal and w/e motor is suitable. Mazda enclosed the entire slide assembly on the 787b so I don't think leaking is a issue. How much it leaks from 0+ is up to the builders skills really......

 

I'll tell you though if I ever find one off a stock I6 (maybe bmw or benz diesels?) its getting retroed in lol. So long as I'M building it though I prefer teli .

[Nizm0Zed]

yes you can, nobody is saying that you cant.

 

but what id say people are looking at here, is to keep the straight intake path, which flows way better than a curved track of the same diameter.

 

that, and telescoping runners would look fukn cool when you pop your bonnet for all the ricers to explain why you thrash them everytime.:cool:

[Guest TeamNissan]

Look at this nice inline set up from Volvo.

 

 

 

VIS (Variable Intake System)

VIS has been equipped with two throttle flap valves which adjust the intake manifold volume to suit the current driving situation. This results in a uniformly high and broad torque curve.

 

“Through precise interplay with the flap valves we actually get three different torque curves that are integrated with one another,” says Derek Crabb. “Consequently, we can exploit the engine’s capacity to the maximum and extract the highest possible power throughout the rev range. The result is alert response to the accelerator pedal at both low and high speeds, with both generous power and good driveability.”

 

[Careless]

are 3 different torque curves enough?! LOL.

 

honestly, the Variable ITR's might be the easiest route for my setup, seeing as I'm going to be running stacks directly from the ITB's... making all these curvey boxes with flaps will just make it uglier and weight a lot more.

[Guest TeamNissan]

Ya thats my point, I was already going itb so its not exactly a big stretch to get a set up like the 787b going, same with you and your monster rb30. If I was going l28et or something though I would def go the other rt and maybe a LD like OTM.

[Flexicoker]

A little bit of information...

 

Intake runner length (and exhaust primary/steps length) is based soley on RPM. Not manifold pressure, throttle position, airflow or anything other than RPM. Its called resonance tuning. Basically theres a pressure wave travelling from the valve, back up your runner, bouncing off the end, and back down to the valve. The goal is to get this wave to hit the intake valve again when its open during the next intake stroke.

 

Here's some info:

http://www.chrysler300club.com/uniq/allaboutrams/ramtheory.htm

 

When Formula 1 allowed variable length intakes they would get shorter and shorter as the RPM's increased, then all of a sudden snap all the way long again, then repeat the process several times over the entire RPM range. What it was doing when it snapped open again was changing harmonics from say the 6th order harmonic to the 5th order harmonic. Which is basically the number of times the pressure wave has bounced back and forth. They also would make sure that each bank snapped long again at different times so that they didn't have all of the cylinders 'untuned' at the same time.

 

Having say... 2 seperate runners that you can switch between will accomplish sort of the same thing, but you'll have two (or more) distinct bumps on your torque curve.

[Nizm0Zed]

so, basically from what you have mentioned of the Formula 1 days,

Ideally on the zed engine (or whatever engine is in there) you would have the 6 runners, all individually controlled (maybe spring loaded to snap back out?)

and each one pulled into a set length per RPM position, in the same order as the firing order.

all that could be controlled with some circuitry, perhaps a purpose built PIC micro controller with a RPM lookup table in the software, and outputs into controlling seperate motors.

 

In practice, i dont think that theoretical setup would show much power gain at all, once you factor in the weight and complexity of the system, as compared to controlling all the runners as one unit.

 

but i guess you would need a very quick reacting system, if you were to step over say 3 stages (maybe 4?) in the whole powerband, once applied to how fast the engine can rev up, especially in the lower gears.

 

i would imagine in practice, that you would limit the system to only work in the higher gears? and perhaps over a certain RPM? to reduce any lag in the system.

[BobbyZ]

A little bit of information...

When Formula 1 allowed variable length intakes they would get shorter and shorter as the RPM's increased, then all of a sudden snap all the way long again, then repeat the process several times over the entire RPM range. What it was doing when it snapped open again was changing harmonics from say the 6th order harmonic to the 5th order harmonic.

 

I didnt think of scaling back the design to use some of the later harmonics for the lower RPM's. I like the idea of doing that but maybe using a valving system that allows you to switch from one harmonic to the next without changing the length of the runner too quickly.

 

I dont see this as being a practical or cheap way of making more power from an L28 but it sure is fun to talk about. I think this would be a very fun design project if I can ever find the time.

[Careless]

A little bit of information...

 

Intake runner length (and exhaust primary/steps length) is based soley on RPM. Not manifold pressure, throttle position, airflow or anything other than RPM. Its called resonance tuning. Basically theres a pressure wave travelling from the valve, back up your runner, bouncing off the end, and back down to the valve. The goal is to get this wave to hit the intake valve again when its open during the next intake stroke.

 

Here's some info:

http://www.chrysler300club.com/uniq/allaboutrams/ramtheory.htm

 

When Formula 1 allowed variable length intakes they would get shorter and shorter as the RPM's increased, then all of a sudden snap all the way long again, then repeat the process several times over the entire RPM range. What it was doing when it snapped open again was changing harmonics from say the 6th order harmonic to the 5th order harmonic. Which is basically the number of times the pressure wave has bounced back and forth. They also would make sure that each bank snapped long again at different times so that they didn't have all of the cylinders 'untuned' at the same time.

 

Having say... 2 seperate runners that you can switch between will accomplish sort of the same thing, but you'll have two (or more) distinct bumps on your torque curve.

 

This is stuff I've already take into account, but the problem is tuning for the 6th wave.... I mean, I could get the runner to be tuned for the 6th wave, but by that time, the air has lost a lot of it's momentum.

 

Tuning for the 3rd or 4th wave is more ideal, but the length becomes so great that it's almost impossible if I were to have a straight set of stacks.

 

Tuning for the 2nd wave would be awesome. I've read of testing labs building up as much as 3psi over atmo at the valve head because of such a strong wave reversion. A supercharging effect indeed.

 

I'm up for actually doing it, but I'm not sure if it will work the way I want it to =/

 

I think my best option is to wait until my RB26 head gets in, so I can measure up the length with the throttle bodies and short-manifolds so I can accurately establish the needed sweep distance from full long to full short.

 

Another problem I can see coming is the fact that the runners are going to have to be the same length (at least) as the distance which they can fully extend... or else the runners themselves would not be able to retract into the tube, or it would hit the throttle plates.

 

Then the driving control begins to come into play.... I'm wondering what kind of slap-back system I can use, and I have to find a motor that can move the units as fast as the engine makes its way up the range... I can vary that with voltage, but the initial power has to be enough so that I can have some to spare in case it starts to stress the motor due to weight of the assembly.

[Nizm0Zed]

"Another problem I can see coming is the fact that the runners are going to have to be the same length (at least) as the distance which they can fully extend... or else the runners themselves would not be able to retract into the tube, or it would hit the throttle plates."

 

If your getting that far into the development of it, and it really is looking like a viable option, then i would suggest using a compound design for the runner, say 3? sections. so it'd collapse into (almost)1/3rd of its full length.

 

shame you wouldn't be able to line the inside of the runner with an elastic compound, that'd withstand the stresses of an enginebay, along with the constant stretch and compression.

would solve your sealing issues, and any potential flow problems at the slide joints.

 

Q? what about an airbox?

would you have seperate airfilters for each runner? or an airbox assembly for it all? then, if there was a box, would it move on the runners too? or just have an outer sleeve that encompasses the whole thing, and 'seals' the telescopic runners inside? that'd solve the sealing issues within the runner itself, and allow you to use one large filter on the front, with a cold air feed directly from the front of the car.

[Flexicoker]

You can definatly make power that way. For example... two of our autocross cars, F05 and F07, each with a CBR600, and almost the exact same intake. The only differences being a slightly different plenum volume and a stepped exhaust on the F07 car (designed using Ricardo Wave) I tuned each of these cars on the same day, both doing 3rd gear pulls from idle until redline. The F05 car just poked along until it hit around 7-8k, then made some major power. It took about 2/3-3/4 of the length of the parking lot to hit redline. The F07 car, took off right from idle, pulled all the way until redline, and it only took 1/2 the length of the parking lot, and we later discovered it had left rubber... all the way through 3rd gear, on fresh R25's. Good harmonic tuning makes a very noticable difference.

[Flexicoker]

I don't think you'd need each one individually controlled, while that would be ideal, I think that 2 alternating banks would be enough to eliminate a significant power drop while the runners were moving to the next harmonic.

 

so, basically from what you have mentioned of the Formula 1 days,

Ideally on the zed engine (or whatever engine is in there) you would have the 6 runners, all individually controlled (maybe spring loaded to snap back out?)

and each one pulled into a set length per RPM position, in the same order as the firing order.

all that could be controlled with some circuitry, perhaps a purpose built PIC micro controller with a RPM lookup table in the software, and outputs into controlling seperate motors.

 

In practice, i dont think that theoretical setup would show much power gain at all, once you factor in the weight and complexity of the system, as compared to controlling all the runners as one unit.

 

but i guess you would need a very quick reacting system, if you were to step over say 3 stages (maybe 4?) in the whole powerband, once applied to how fast the engine can rev up, especially in the lower gears.

 

i would imagine in practice, that you would limit the system to only work in the higher gears? and perhaps over a certain RPM? to reduce any lag in the system.

[Guest TeamNissan]

I don't understand why people keep imagining problems that have already been solved by manufactures. Not only that but have been mentioned in this very thread already. We are not inventing a single thing here, all been done.

[BobbyZ]

I don't understand why people keep imagining problems that have already been solved by manufactures. Not only that but have been mentioned in this very thread already. We are not inventing a single thing here, all been done.

 

None of us think that we are reinventing something that has never been done before. I think it would be fun to design and build a variable intake system on an L28, not because it is the most cost effective way to make power but because it has not been done before (on this engine) and it presents some fun design challenges.

 

All of the ideas that have been brought to the table here are ideas from existing technologies, we all know that. We just want to adapt them to our own little engines. Does 1fastz think he is inventing the DOHC head???

[Nizm0Zed]

fark, he's going to be rich on royalties, look at all the manufacturers that have copied his idea:biggrin:

 

yea, so what, its been done by other manufacturers, thats a good thing, means we can learn from their mistakes.

I reckon it would be a kickass thing to plan out and build as a one off piece of auto porn for the engine bay of a zed

[Guest TeamNissan]

My entire response was about the "problems" that people keep bringing up not the idea itself, read before you hit that quote button bobby or try and feed off someone else that did nizmo.

 

I really don't want this thread to get off track. How about we get back to being constructive? Anyone been able to dig up any more info, pics, stats?

[Careless]

Q? what about an airbox?

would you have seperate airfilters for each runner? or an airbox assembly for it all? then, if there was a box, would it move on the runners too? or just have an outer sleeve that encompasses the whole thing, and 'seals' the telescopic runners inside? that'd solve the sealing issues within the runner itself, and allow you to use one large filter on the front, with a cold air feed directly from the front of the car.

 

airbox is a no go..

i found someone with filters on ebay, i think i saved his name.. I haven't bought the filters cause i haven't got the head or the intake system to buy them for yet.

 

but they are snap on filters with a membrane in between two layers of wire mesh and has a radius on the ID.

 

as for the compound design, it's an option, but it adds another level of instability and room for error. If i need it, i'll use it, but for all intensive purposes, i'd like to keep it down to one runner for my own setup.

 

sounds like other people here wanna have some vITB's too, but not all with the same idea, so this could get quite interesting

 

I got some power window motors in the garage that I'm going to study this week. I'll see what kind of speeds I can get from them and what kind of weight they can move.

[Nizm0Zed]

 

I got some power window motors in the garage that I'm going to study this week. I'll see what kind of speeds I can get from them and what kind of weight they can move.

 

 

Not very fast, but they will carry a bit of weight.

 

its all in the gearing, usually a worm drive setup.

as im sure you can understand, changing the ratio for higher speed would reduce the total load of the motor.

a tough compromise to get it right, however the whole runner setup could be pretty light.

 

as for all the different ideas, it'd be awesome if several people make them all in different ways, and we see the pro's and cons of each design.

[Nizm0Zed]

My entire response was about the "problems" that people keep bringing up not the idea itself, read before you hit that quote button bobby or try and feed off someone else that did nizmo.

 

 

so your raggin on me for having an opinion? or suggesting something? or posing a question that could have been a potential issue to solve??

 

Fuckit. I'll keep my opinion and ideas to myself. and i'll just build it myself.

FYI, there are a surprisingly large amount of innovative ideas (both past AND present) that have originated from Australian sheds, just that most of them get sold to large companies before they gain any recognition.

 

not like being an original American and sticking 26 inch chromies on a busa...

 

[/end rant]

[Careless]

i dunno what any of what you two are bickering about has to do with vITB's, so both of you women stop pullin' hair

 

Nizm0Zed

 

I figured the power window motors wouldn't be the quickest. I found some stepper motors that use screw drive spindles and nylon slide bushings that are self lubricating and go up and down with the screw.

 

I'm having trouble finding one that would be the proper amperage, and gearing... (i think 10:1 might work ), but I think I can use the help of my father to do this.

 

He is a retired college professor with 32 years in the AC and DC motors / Electrical department of a well known college.