Tuning Variable Intake

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Tuning Variable Intake

nedge2k

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Has anyone experimented with this?

The theory goes:

A long, narrow inlet tact will create more torque at low RPMs but at high RPMs will restrict flow, impeding power.

A short, fat inlet tract with a large throttle body will increase top end power but low down torque will suffer.

So surely, if you stuck a dual length inlet tract onto a large throttle body, with some kind of internal flap directing the flow between the two, based on load/rpm, you'd be onto a winner?

I don't know how viable it is but if you took a vacuum feed off the inlet manifold and hooked it up to one of those cold start flaps*, it should work, right?

*had one on a 106 once, on cold start the flap would open up to a pipe over the exhaust manifold, blocking off the cold intake.
 
fiat have done this to the starjet
DSCF3781.JPG

DSCF3780.JPG

they stuck lums in the middle of inlet ports though
DSCF3782.JPG
 
Oh yeah I know it's about for more "modern" engines, my Bravo has it :)

...or is the point you're making that the inlet manifold could be nicked from the starjet? :D

I think my DIY method would make a better noise on full chat :p
 
DIY it is then :D

It's more the inlet plenum vacuum I'm looking for clarification on - the vacuum increases with load right? So the more load, the more it closes the flap, the more torque it'll have due to the restricted tract increasing air velocity. As you move up the rev range and there's less load, flap opens, powaaaaaaa :D
 
I don't know how viable it is but if you took a vacuum feed off the inlet manifold and hooked it up to one of those cold start flaps*, it should work, right?

*had one on a 106 once, on cold start the flap would open up to a pipe over the exhaust manifold, blocking off the cold intake.

DIY it is then :D

It's more the inlet plenum vacuum I'm looking for clarification on - the vacuum increases with load right? So the more load, the more it closes the flap

^^
 
starjet does not employ a variable geometry inlet, it just closes off half the port at lower RPM to help swirl into the combustion chamber.

can't think of any FIAT enignes that use a variable geometry inlet off hand, but know the Rover KV6 as found in the ZS180 does.
 
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DIY it is then :D

It's more the inlet plenum vacuum I'm looking for clarification on - the vacuum increases with load right? So the more load, the more it closes the flap, the more torque it'll have due to the restricted tract increasing air velocity. As you move up the rev range and there's less load, flap opens, powaaaaaaa :D

vacuum increases with higher RPM and smaller throttle opening. So full throttle pretty much always equals no vacuum (unless you have inlet restriction issues)
 
vacuum increases with higher RPM and smaller throttle opening. So full throttle pretty much always equals no vacuum (unless you have inlet restriction issues)

Sorry, thats what i meant, had it the wrong way round :eek:

Also, my Bravo has variable inlet in the tract - although I'm not sure it's anything more than a restrictor valve.
 
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The more I think about it, the more I think it's gonna have to be electronic, based on map, rpm and maybe tps.all doable tho!
 
if you get a set of throttle bodies from a a suzuki gsxr 650 or 750 they have twin butterflies in each body and are used to create more torque a lower rpm and they can be controlled by something like megasquirt ect and you end up with the best of both worlds.

paul
 
" can't think of any FIAT enignes that use a variable geometry inlet off hand, but know the Rover KV6 as found in the ZS180 does."

The 20v VIS found in the later bravo and the later 20v maria, as well as the 20v VIS coupe

Adds 7 bhp to official numbers over fixed length induction path. Its vacuum driven as well
 
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