Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > Porsche 911 Technical Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered
 
flat6rs's Avatar
 
Join Date: Feb 2007
Posts: 21
Intake stacks

What are the advantages of building an engine with racing stacks for the intake as oppose to a plastic intake manifold or a varioram manifold. From my knowledge the varioram manifold would provide better torque because of the multi stage intake length.

I have observed many race engines use the intake stacks instead of using a manifold. What are the advantages of using them?

Old 07-23-2007, 12:38 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Moderator
 
Bill Verburg's Avatar
 
Join Date: Dec 2000
Posts: 26,436
Garage
Individual throttle body type intakes like TWM will give improved throttle response but are tuned to a specific rpm range.

The v-ram type intake improves mid range while still giving decent top end by varying the length of the intake tract.

Which is better depends on lots of things.

For street use w/ relatively tall, widely spaced gearing the v-ram will likely be the better choice

For track use w/ lower, closer gearing and relatively little part throttle use, the individuals will likely be better.
__________________
Bill Verburg
'76 Carrera 3.6RS(nee C3/hotrod), '95 993RS/CS(clone)
| Pelican Home |Rennlist Wheels |Rennlist Brakes |
Old 07-23-2007, 03:17 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered
 
flat6rs's Avatar
 
Join Date: Feb 2007
Posts: 21
thanks alot Bill
Old 07-23-2007, 08:04 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Registered
 
petevb's Avatar
 
Join Date: Nov 2003
Location: Bay Area, CA
Posts: 1,072
I'd add that a single throttle body manifold requires a relatively mild cam in order to maintain any kind of idle. Individual throttle body intakes work well with much more aggressive, race-only type cams. These cams would never pass smog, but using one allows a properly set up race motor to make much more peak power than the milder cam options available with a stock intake manifold. The power difference between the these cams can be more than 30 hp, with the gains mostly coming at very high rpms- another big reason you'll see these intakes on race cars.
__________________
69 w 997 GT3 3.6L
Old 07-23-2007, 08:22 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
AutoBahned
 
RWebb's Avatar
 
Join Date: Jul 2007
Location: Greater Metropolitan Nimrod, Orygun
Posts: 55,993
Garage
hmmm, well, in general, but BMW has/does use[d] ITB's on some production cars...
Old 07-23-2007, 11:59 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered
 
Grady Clay's Avatar
 
Join Date: Dec 2003
Location: Arapahoe County, Colorado, USA
Posts: 9,032
flat6rs,

The important fact is your application.

Carburetors are great period.

Same with MFI but greater performance.

CIS is period correct with some performance compromise.

DME improved performance while better emissions and economy.


If I were to build a performance engine today, it would still be MFI. A close second is an aftermarket EFI. I suspect the order will change in the next few years.

Best,
Grady
__________________
ANSWER PRICE LIST (as seen in someone's shop)
Answers - - - - - - - - - - - - - - - - $0.75
Answers (requiring thought) - - - - $1.25
Answers (correct) - - - - - - - - - - $12.50
Old 07-23-2007, 12:26 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
Registered
 
flat6rs's Avatar
 
Join Date: Feb 2007
Posts: 21
I am very sorry but I do not know much technical terms. I know that EFI is electronic fuel injection which you can setup with aftermarket ECUs like motec, etc. But what is MFI and DME and also CIS? And why are carburetors good? Aren't that for older cars?

Thanks in advance
Old 07-25-2007, 03:49 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Moderator
 
Bill Verburg's Avatar
 
Join Date: Dec 2000
Posts: 26,436
Garage
Quote:
Originally Posted by flat6rs View Post
I am very sorry but I do not know much technical terms. I know that EFI is electronic fuel injection which you can setup with aftermarket ECUs like motec, etc. But what is MFI and DME and also CIS? And why are carburetors good? Aren't that for older cars?

Thanks in advance
Motec and DTA et al are aftermarket EFI setups

Carburators were the original throttle bodies, as used on Porsche they were ITB, 1 throttle/ cylinder, very crude metering and control but not sensitive to intake fluctuations from happy cams

MFI is mechanical fuel injection, an archaic 60s and 70s diesel system adapted for gas engines, very crude control but not sensitive to intake fluctuations from happy cams


DME is digital motor electroncs, the control unit used by the Porsche factory in it's Motronic systems, used on 911 form '84 to today, very precise control, drawback is the single throttle body and sensitivity to intake pulsations w/ happy cams

CIS is continuous injection system, another archaic FI system that let a continous stream of gas dribble into the intake ports, used for "73 to '83 on 911s, drawback is single throttle body and sensitivity to intake pulsations w/ happy cams
__________________
Bill Verburg
'76 Carrera 3.6RS(nee C3/hotrod), '95 993RS/CS(clone)
| Pelican Home |Rennlist Wheels |Rennlist Brakes |

Last edited by Bill Verburg; 07-25-2007 at 04:53 AM..
Old 07-25-2007, 04:03 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Registered
 
flat6rs's Avatar
 
Join Date: Feb 2007
Posts: 21
Thanks again for your prompt reply, Bill

Cheers!

Old 07-25-2007, 04:17 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Reply


 


All times are GMT -8. The time now is 04:19 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2025, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2025 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.