 Good or bad- short Intake manifolds, For Dual Webers |
|
|
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
|
  |
| tornik550 |
 Nov 16 2011, 10:24 PM
Post
#1
|
|
Senior Member  Group: Members Posts: 1,248 Joined: 29-January 07 From: Ohio Member No.: 7,486 Region Association: None  |
Are there any advantages or disadvantages to using short intake manifolds for dual webers?
http://www.914world.com/bbs2/index.php?sho...p;#entry1573218 |
   |
 
|
| jaxdream |
Nov 16 2011, 10:36 PM
Post
#2
|
|
Senior Member Group: Members Posts: 974 Joined: 8-July 08 From: North Central Tennessee Member No.: 9,270 Region Association: South East States |
Off hand , I'd say incoming intake velocity would be shortened / reduced, heat soak more likely ( closer to head connection ) . Also linkage setup would be a little trickier......
The people that really know will probably chime in shortly.... my $.02.... Jack |
|
|
|
| Dave_Darling |
Nov 17 2011, 12:20 AM
Post
#3
|
|
914 Idiot Group: Members Posts: 15,204 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California 
|
Short manifolds are a Very Very Good Thing for the VW 411/412 and anyone putting a Type IV into a Type III body. Because even "baby Webers" don't hardly fit with regular manifolds.
In general, short and fat pipes have a greater flow capacity than skinny narrow pipes. But at lower flow rates, the short and fat pipes have worse velocity. So the shorter manifolds could help top-end power at the expense of mid-range torque and mixture quality. Depending on lots of other factors, of course. --DD |
|
|
|
| SirAndy |
Nov 17 2011, 12:54 AM
Post
#4
|
|
Resident German Group: Admin Posts: 42,257 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(Dave_Darling @ Nov 16 2011, 10:20 PM)  So the shorter manifolds could help top-end power at the expense of mid-range torque and mixture quality. (IMG:style_emoticons/default/agree.gif) In general, the longer the intake manifolds, the more low end torque you have. The shorter one tend to shift the power-band to the higher RPM range ... (IMG:style_emoticons/default/popcorn[1].gif) |
|
|
|
| messix |
Nov 17 2011, 01:38 AM
Post
#5
|
|
AKA "CLUTCH KILLER"! Group: Members Posts: 6,995 Joined: 14-April 05 From: between shit kickers and pinky lifters/ puget sound wa.north of Seattle south of Canada Member No.: 3,931 Region Association: Pacific Northwest |
This is a really complicated issue, you have volume and velocity to balence to the desired engine displacement and rpm range. Do some google searching on intake maniflod flow design.
|
|
|
|
| messix |
Nov 17 2011, 01:49 AM
Post
#6
|
|
AKA "CLUTCH KILLER"! Group: Members Posts: 6,995 Joined: 14-April 05 From: between shit kickers and pinky lifters/ puget sound wa.north of Seattle south of Canada Member No.: 3,931 Region Association: Pacific Northwest |
One more thing, on itakes that do not have a shared plenum you will get a stand off reversion if there is not enough volume in the intake at higher rpm. This means that there is a wave of intake charge that bounces off the closed valve and travels back thru the intake and out the carb then sucked backe down the.intake on valve opening. This can really eff will tuning the engine.
Try searching for video on it. |
|
|
|
| URY914 |
Nov 17 2011, 05:17 AM
Post
#7
|
|
I built the lightest 914 in the history of mankind. Group: Members Posts: 127,549 Joined: 3-February 03 From: Jacksonville, FL Member No.: 222 Region Association: None |
It all depends on the combo. Cam, carbs, CR, etc, etc, etc. And the differance will be small and only seen on a dyno.
|
|
|
|
| VaccaRabite |
Nov 17 2011, 07:59 AM
Post
#8
|
|
En Garde! Group: Admin Posts: 13,757 Joined: 15-December 03 From: Dallastown, PA Member No.: 1,435 Region Association: MidAtlantic Region
|
The heat soak issue is easily solved by using the phenolic spacer between the head and intake runner. That does require longer studs on the head, but those can be bought or made super easy!
You might get a little less torque but would be able to use a raintray again, which I think is a nice trade off. The sync issue is solved by using either one of the 2 cable sync options on the market - and you SHOULD do that no matter what manifolds you use! Zach |
|
|
|
| Mark Henry |
Nov 17 2011, 08:05 AM
Post
#9
|
|
that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
Torque is king in a type four, look at what Raby/HAM uses, they use the tallest manifolds out on the market.
(IMG:http://www.914world.com/bbs2/uploads_offsite/www.csp-shop.de-26-1321538955.1.jpg) |
|
|
|
| SGB |
Nov 17 2011, 09:13 AM
Post
#10
|
|
just visiting Group: Members Posts: 4,086 Joined: 8-March 03 From: Huntsville, AL Member No.: 404 Region Association: South East States |
Yep. Tall is best fore us. I used to have shorty bus manifolds and went to the one's pictured above. Night and day!
Jake can (used to?) build a motor that does take advantage of the short ones too, but it is on a high rpm config- probably roller cam, etc. Get tall manifolds and the tallest velocity stacks you can fit. My stuff came from Aircooled.net. |
|
|
|
| DBCooper |
Nov 17 2011, 09:41 AM
Post
#11
|
|
14's in the 13's with ATTITUDE Group: Members Posts: 3,079 Joined: 25-August 04 From: Dazed and Confused Member No.: 2,618 Region Association: Northern California |
QUOTE(SGB @ Nov 17 2011, 07:13 AM) My stuff came from Aircooled.net. YES! John's a great guy, one of that top circle of engine builders and parts suppliers, and absolutely no agenda. |
|
|
|
|
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:
|
Lo-Fi Version | Time is now: 16th July 2025 - 04:10 PM |
Invision Power Board
v9.1.4 © 2025 IPS, Inc.