pork
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Mar 27, 2015 19:33:51 GMT
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I'm thinking of making a variable length intake manifold for a n/a build
Idea is to have telescopic trumpets on a linear actuator
My question is how would I control the length? Purely rpm based? Vacuum?
Also, once I've figured what signal controls the length, what method of automation would work? Stepper motor, vacuum actuator?
Cheers
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Mar 27, 2015 20:02:01 GMT
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how would you ensure a seal on the telescopic part?
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pork
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Mar 27, 2015 20:04:53 GMT
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o-ring in a recess somewhere
All at plannig stage, it's the control side I'm struggling to think of
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Mar 27, 2015 20:21:49 GMT
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Ok, I've bitten, found my research project for the evening. I assume you're familiar with the Mazda 787B, I found this pretty awesome document about the engine. It's detailed but concise and among other things shows that the manifold length was solely controlled by engine speed: SAE Document on 787B EngineIt also explains the trumpets are actuated by cable (like a throttle/bicycle brake cable), driven by a dc motor with a potentiometer on the motor for position feedback. Got a few pics too: This one kind of shows the winding gear... and this one the motors (which look like MX5 headlamp motors):
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I've got Rovers.
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Mar 27, 2015 20:34:32 GMT
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I've got Rovers.
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pork
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Mar 27, 2015 20:48:17 GMT
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Yeah, seem s few bits on this. Cheers for article link
I would of thought it would of been controlled on engine vacuum/load, rather than just rpm
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Mar 27, 2015 21:30:09 GMT
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I suppose it's a bit different for a racing car, it's more than likely to be at full load pretty much all of the time. Maybe on a road car, vac/load/throttle position is more important. Saying that... if you're after improving the power band perhaps it's not that important until near full throttle anyway. I can't find much research on inlet manifold tuning at part throttle. I don't know enough about fluid dynamics unfortunately at part throttle does the 'pulse' slow down or is it just reduced in pressure? I'll continue reading...
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I've got Rovers.
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Mar 27, 2015 21:34:50 GMT
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The 306 s16 ran something similair only that was done via two inlet tracts per cylinder
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pork
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Mar 27, 2015 21:37:12 GMT
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Quite a few models have 2 inlet tracts, with a butterfly valve opening between the long and short runners. This idea is for infinitely varying runners
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ChasR
RR Helper
motivation
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Mar 27, 2015 21:38:22 GMT
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Ford Duratec 2.5 V6 can also be added to this list. With both runners open they were fairly flat below 3.5kRPM.
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pork
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Mar 27, 2015 22:09:34 GMT
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It would also be easier to construct if the runners were inside a plenum and the throttle pre plenum.....or would it not work, and need to be more like itb's
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Mar 28, 2015 11:55:10 GMT
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the only time you would ever need the increases from a variable intake are when you are driving at what which is why they are all driven from the engine speed Adding the vacuum to the equation would make it considerably more complex to set up ( as well as there is almost no vacuum on an ITB setup after about 20-30% throttle) . Some engines such as the mx5 1.8 with the BP4w head and the bmw M44 engine both have effectively 2 intakes which it switches between at a given RPM.
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.
James
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Too many projects, not enough time.
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pork
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Mar 28, 2015 12:11:18 GMT
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Would this all work inside a plenum? With the throttle pre plenum?
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Mar 28, 2015 12:39:51 GMT
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^ sam - interesting article by Emerald (brings back memories of pulse lenght tuning and wave harmonics), thanks for that Once upon a time ... Yamaha bikes (in the 70s / 80s ?) used a resonance chamber in the intake, it might be more practical to add a chamber to each of your intakes and open/close them with a butterfly valve www.thumpertalk.com/topic/854539-rt-180-intake-air-chamber-what-is-the-purpose/Should be an interesting project no matter how you decide to do it, pics when done pleeze
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sowen
Club Retro Rides Member
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Mar 28, 2015 12:55:35 GMT
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If it's of any use I found these when researching my Audi V8 with variable intake This is what's actually inside the plenum behind the throttle The flaps are controlled by vacuum actuators on the front side, with what look like electrically controlled solenoids to trigger at different rpms
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pork
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Mar 28, 2015 16:25:36 GMT
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Cool, looks mad, So it's ok to have trumpet inside the plenum
Il draw some pics of what I have in mind
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pork
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Mar 28, 2015 17:26:26 GMT
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pork
Posted a lot
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Mar 28, 2015 17:26:53 GMT
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pork
Posted a lot
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Mar 28, 2015 20:28:51 GMT
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Also what about injector reposition? Like this?
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Mar 29, 2015 15:59:26 GMT
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the only problem with this is the space in the engine bay. also, i cant remember the angle, but there is a specific angle to get the best performance from the trumpets, so you couldn't just have straight trumpets that slide,
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