|
|
Mar 29, 2015 16:36:56 GMT
|
the later MX5 with the variable valve timing doesn't bother with the dual length intake. valve timing has an affect on chosen length.
seems like a lot of work for probable very minium gains. you may find a long inlet length works well enough without the complications of varying the length. seems like a fun project to try to get it to work. there are some videos on utube with variable length trumpets working. anything under full throttle wont have an affect through length though, just where the butterfly is positioned may have some affect on ram tuning.
|
|
|
|
|
pork
Posted a lot
Posts: 1,655
|
|
Mar 29, 2015 17:14:53 GMT
|
This is what I'm thinking lol
|
|
|
|
pork
Posted a lot
Posts: 1,655
|
|
Mar 29, 2015 19:06:08 GMT
|
|
|
|
|
|
|
Mar 29, 2015 19:28:30 GMT
|
I've always fancied doing variable length runners but there are two big issues that i have: 1, no car i have ever owned has had enough room to fit them in the engine bay. 2, i don't have my own dyno where i can really dial in the tuning of the engine and at what rate the length changes. Linear actuators could be used to control the length, I think that these can be set to any given extension, but i'm not sure how fast they extend. No particular reason they need to be straight though AFAIK. (You see banana shaped ones on bikes.) If you were to double up on seals you could make them like a trombone slide and halve the protrusion from the side of the engine. Or you could do a 90 degree bend and poke them up though the hood. I'd be interested to found out how flared ends affects things. Intuition suggests a radiused edge to keep turbulence at bay at the mouth, and an otherwise straight length of tube. Bass speaker ports tend to have sharp cut-off edges. Actual musical instrument trumpets have a huge bell to improve volume. The speaker has zero overall flow rate and the trumpet has a person exhaling hard though it. I wonder if an engine wants something in between.
|
|
|
|
pork
Posted a lot
Posts: 1,655
|
|
Mar 29, 2015 19:30:24 GMT
|
That emerald article earlier on in the thread said that trumpets or straight tubes had no difference
|
|
|
|
|
|
Mar 29, 2015 19:58:44 GMT
|
i think there is a small confusion between trumpet and taperd. there was no measurable difference in air flow between a tapered or straight tube. the trumpet (curved bit on the end) is quite important. air does not go straight in from the front of the tube but also comes around from the back. there is a theory that a full radius trumpet works better than a part radius. also any race engine with a plenum the trumpet will go into the plenum where as road cars are usually just a flush runner for ease of making. and, a straight runner will flow better than a curved runner BUT a curved runner fitted for convenience to clear inner wings etc will benifit more for pulse tuning than a straight runner that is too short
|
|
|
|
pork
Posted a lot
Posts: 1,655
|
|
Mar 29, 2015 20:05:00 GMT
|
I will try and make a trumpet type runner, and will have going inside the plenum.
Regarding the plenum, does it matter if it's a round or square tube? just thinking along the lines of ease of construction and available materials.
|
|
|
|
|
|
Mar 31, 2015 21:41:34 GMT
|
Having the throttle pre-trumpets in a plenum makes sealing the (variable) runners much more important. Having ITBs with variable lenght trumpets will still require some sealing, but I guess a slight leakage is not all that important since we're aiming for resonance Just a thought. Tge more seals, the more friction needs to be overcome and te more power & guides you'll need to shift a whole plenum chamber with 4(?) runners...
|
|
|
|
|
|
|
agreed with TDW - keep the TBs between the head and the runners.
If you ended up with an engine that can make a lot of vacuum at idle, and the actuators you use aren't that strong, it may end up trying to suck the trumpets down, and breaking your setup. Which would be heartbreaking if it was mine.
The power gains will be utterly minimal on a road car - so no need to try to make it a piece of engineering beauty. Four pipes that move, with nice trumpets, and a filter on the end of each. Job jobbed (kinda)
|
|
You're like a crazy backyard genius!
|
|
|
|
Apr 23, 2015 15:31:07 GMT
|
Its a lot easier to just do it as a 2 stage trumpet length. So you have a set of shorter trumpets sized for top end power, with bellmouth ends Above these you have a plate holding 4 longer trumpets which is attached to your linear actuator (And preferably some separate linear bearings for it to slide on - don't expect the actuator to do both jobs) The upper end of the trumpets has a bellmouth, the lower end is shaped to seal on the top of the lower trumpets. So Low speed, you have full length trumpets, and at your pre determined switchover point, the actuator lifts the top trumpets 20mm or so out of the way and the air short circuits underneath them. Ideally all this sits inside a nice volume airbox, fed by a remote filter In my experience, I doubt the gains will be worth the hassle. Id size the runner length for Torque and run a nicely ducted, sealed airbox with a feed from a high pressure area at the front of the car (Actually measured high pressure rather than "That looks about right" ) which will help as engine speed / vehicle speed rises. Hope that helps Dom
|
|
|
|
|
pork
Posted a lot
Posts: 1,655
|
|
Jul 14, 2017 19:00:14 GMT
|
Been a while But I've finnaly got round to scratching that itch lol I'm using some itbs from a Yamaha r6 yzf, which has variable length inlets 👍 Here it is all mounted to a micra engine, it's in a k11 until I can find a affordable pao to bolt it too 😎😎😎 And here it is running ........need some help though, need to convert from maf to map, any suggestions Also I think th tps that comes from these itbs, won't work with my ecu, anything above 1500 rpm, and it sounds like it's hitting a rev limiter 😕
|
|
|
|
fad
Posted a lot
Posts: 1,781
|
|
Jul 15, 2017 10:37:01 GMT
|
Aw I wanted to see them move!
|
|
|
|
|
|
Jul 15, 2017 10:50:12 GMT
|
tps should work fine but pinout may well be different.
what ecu are you using?
|
|
|
|
pork
Posted a lot
Posts: 1,655
|
|
Jul 15, 2017 15:00:28 GMT
|
Aw I wanted to see them move! There you go
|
|
|
|
pork
Posted a lot
Posts: 1,655
|
|
Jul 15, 2017 15:02:17 GMT
|
tps should work fine but pinout may well be different. what ecu are you using? The micra tps has 3 pins......but the itbs have 4 I've tried every combination I can think of, I'm using the standard micra ecu.....but may change it, just wanted to see whether it would work with what I've got
|
|
|
|
pork
Posted a lot
Posts: 1,655
|
|
Jul 15, 2017 15:54:42 GMT
|
I did try the micra tps on these but they open in reverse to the micra throttle
So gunna have to mount it on the opposite side, on the cable pulley somewhere
|
|
|
|
|
|
Jul 15, 2017 18:55:28 GMT
|
just swap the wires about.
|
|
|
|
pork
Posted a lot
Posts: 1,655
|
|
Jul 15, 2017 18:57:59 GMT
|
I have been 😔
|
|
|
|
|
|
Jul 15, 2017 18:59:04 GMT
|
4 wires? hmm.
can the Micra ecu be mapped?
|
|
|
|
pork
Posted a lot
Posts: 1,655
|
|
Jul 15, 2017 18:59:57 GMT
|
These itbs have 2 tps which talk to each other apparently
It was a fly by wire set up (I've just removed the servo motor and operating via cable now)
|
|
|
|
|