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Intake plenum-throttle angle
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Author:  ferrarist75 [ August 6, 2016, 3:25 pm ]
Post subject:  Intake plenum-throttle angle

Kind of weird question....
I builded an Locost two years ago and now i'm changing V6 engine with 20VTurbo one(mid-engined project).
In order to use as short turbo piping as possible and due to FMIC fitting issues(actually it will be RMIC because the cooler will be fitted behind me) it will be great if i can point the throttle in different angle. I plan to cut the yellow marked section(picture below), reweld it and move it away from the head.......
But......the pressured air makes 90 degree turn when pass the throttle and into the plenum. I'm sure that manufacturer did make some calculation when designing turbo intake system.
Will change in this angle make any difference in air quantity for 5th cylinder for example?
It will be even better for me if i turn TB 90 degree to point straight into the plenum. But will i mess the air flow badly?

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Author:  TRX [ August 8, 2016, 11:15 pm ]
Post subject:  Re: Intake plenum-throttle angle

ferrarist75 wrote:
Will change in this angle make any difference in air quantity for 5th cylinder for example? ...
It will be even better for me if i turn TB 90 degree to point straight into the plenum. But will i mess the air flow badly?


Shouldn't make much difference.

Author:  1055 [ August 8, 2016, 11:48 pm ]
Post subject:  Re: Intake plenum-throttle angle

Thats the great part about forced induction, you may loose some efficiency, but the extra pressure makes up for it! subaru uses way more restrictive bends on their oem applications, you'll be fine.

Author:  ferrarist75 [ August 9, 2016, 1:22 am ]
Post subject:  Re: Intake plenum-throttle angle

Great news thanks....

Author:  wrightcomputing [ August 9, 2016, 7:19 am ]
Post subject:  Re: Intake plenum-throttle angle

Yeah Turbo's are great if you do something that causes you to lose power then just turn up the boost to get is back. I doubt changing the angle would make it worse. When originally designed it was probably made to be as compact as possible.

Author:  Bent Wrench [ August 9, 2016, 9:01 am ]
Post subject:  Re: Intake plenum-throttle angle

Since I first saw that pic this has been bugging me.

Can you really call something that small a plenum?

When I hear the term plenum it implies to me a volume, that has no volume.

I would guess that in no/low boost that airflow is compromised.

Air flows into a runner like water goes down a drain, from the sides.

I would want at least a runner diameter clearance on all sides.

Given it's design changing the inlet angle should not change much as long as it does not create a Venturi.

Is that a specialized race part that was built to minimize turbo lag on a motor that is operated constantly in (high)boost?

Author:  1055 [ August 10, 2016, 2:00 pm ]
Post subject:  Re: Intake plenum-throttle angle

Bent,

IIRC - most older fiat turbo models ( and newer ones, the 1.4 multi air for example) Used a compressor wheel that was about half the size for what most of us would usually call 'adequately sized'. Because of this, they operated similarly to a diesel, starting to spool at idle and creating boost as low as 2200 rpm. now, it was minimal levels, but when combined with a tight engine bay (as most fiats contain.) It made intake manifolds like this viable.

Author:  ferrarist75 [ August 10, 2016, 5:30 pm ]
Post subject:  Re: Intake plenum-throttle angle

Bent Wrench wrote:
Is that a specialized race part that was built to minimize turbo lag on a motor that is operated constantly in (high)boost?

It's stock Fiat Coupe 2.0 20VT intake manifold......i'm running Garret GT28RS with all supporting mod's....stock engine internals.......there is tons of dyno results showing 290 - 370bhp on various boost levels.......never dynoed mine......
IMHO that's solid and cheap engine to run on track(or at least in Europe), if you know how to manage it.......
Yes - plenum looks really small to me as well, but i don't want to mess with manufacturer's calculated intake flows.......
If i have time, maybe i'll try to make manifold as on my old 3.0V6.......at least all pots will be less unequally away from the TB.....

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