03-06-2017, 05:16 PM
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#1
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Registered User
Join Date: Feb 2015
Location: QC
Posts: 412
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Intake manifold movement?
Noticed what appears to be the manifolds moving away from each other as throttle is given. Or am I just seeing the throttle body moving upwards , (being held by intake tube), as the engine rotates to the passenger side in response to the torque?
Did I miss a passage about variable intake lengths that require manifold movement?
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03-06-2017, 06:27 PM
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#2
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Registered User
Join Date: May 2014
Location: S.California
Posts: 2,029
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If the engine is moving like that - have you checked the engine mounts?
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03-07-2017, 01:53 AM
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#3
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Registered User
Join Date: Feb 2015
Location: QC
Posts: 412
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Engine mount only has a few thousand miles on it. It's the normal amount of movement that I would expect to see on any rubber mounted engine and less than what you normally get with a v8. Are the manifolds flexible?
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03-07-2017, 05:37 AM
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#4
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01101
Join Date: Jul 2015
Location: CT
Posts: 587
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This happens on mine. The boots between the manifolds are rubber, and under vacuum they will contract.
Last edited by alm001; 03-07-2017 at 05:46 AM.
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03-07-2017, 05:42 AM
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#5
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Registered User
Join Date: Dec 2009
Location: Orange County, CA
Posts: 1,958
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Will is saying that the intake manifolds are moving away from each other ?, this means that one of them could be loose, but if you have a worn engine/tranny mount both manifolds will move along with the throttle body (and engine..)
Last edited by Gilles; 03-07-2017 at 05:45 AM.
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03-07-2017, 05:48 AM
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#6
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01101
Join Date: Jul 2015
Location: CT
Posts: 587
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Quote:
Originally Posted by Gilles
Will is saying that the intake manifolds are moving away from each other ?, this means that one of them could be loose, but if you have a worn engine/tranny mount both manifolds will move along with the throttle body (and engine..)
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Right, moving away from each other under throttle. So as he presses the throttle manifold vacuum level goes down, and the manifolds move apart.
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03-07-2017, 01:58 PM
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#7
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Registered User
Join Date: Feb 2015
Location: QC
Posts: 412
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https://youtu.be/8_ADUbIiaP0
Sorry I can't embed for some reason...
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03-08-2017, 02:51 AM
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#8
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Registered User
Join Date: Feb 2015
Location: QC
Posts: 412
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I'll find the torque value for the manifold bolts and give them a check on Friday. I would assume that if they were that loose to allow movement that it would throw a code...
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03-08-2017, 02:53 PM
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#9
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Registered User
Join Date: Feb 2015
Location: QC
Posts: 412
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Quote:
Originally Posted by alm001
This happens on mine. The boots between the manifolds are rubber, and under vacuum they will contract.
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So does yours react the same as my video? Can't figure out if this is trompe l'oeil or if there is an issue here. I'll take measurements at rest and under vacuum...
Friday or Saturday morning...
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03-08-2017, 03:34 PM
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#10
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Ben-Auto-Design
Join Date: Oct 2014
Location: French Riviera
Posts: 827
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It's normal.
At idle you're at 26inHg of vaccum inside the manifold, and when you open the throttle, you have almost atmospheric pressure.
This difference of pressure added with the design of the manifold (distance between manifold mounting flange and plenum) makes the whole thing move.
That's why the guys that went with forced induction have to strap the manifolds together 
And also why Porsche is using a plenum with spin-locks and tie bar on all the last generation 911 with turbos!
IMGP3367.jpg Photo by caseyparkin | Photobucket
__________________
ASE certified Automotive Master Technician.
Porsche Tech in France.
www.benautodesign.fr
Ben-Auto-Design : Performance parts for 9X6 / 9X7
1982 928 S Euro
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03-08-2017, 03:55 PM
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#11
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Registered User
Join Date: Feb 2015
Location: QC
Posts: 412
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Quote:
Originally Posted by Ben006
It's normal.
At idle you're at 26inHg of vaccum inside the manifold, and when you open the throttle, you have almost atmospheric pressure.
This difference of pressure added with the design of the manifold (distance between manifold mounting flange and plenum) makes the whole thing move.
That's why the guys that went with forced induction have to strap the manifolds together
And also why Porsche is using a plenum with spin-locks and tie bar on all the last generation 911 with turbos!
IMGP3367.jpg Photo by caseyparkin | Photobucket |
Many thanks Ben 
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