 2.7 CIS to Carbs - how much HP loss? |
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| Scott S |
 Jul 2 2009, 03:15 PM
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#1
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Small Member  Group: Members Posts: 1,698 Joined: 30-April 03 From: Colorado Member No.: 633  |
Hi All -
Got a line on a rebuilt 2.7 out of a 1977 911S. It is 100% complete including the full CIS system. What kind of power loss would I experience if I stripped off the CIS and went with carbs? The motor is only 165hp to begin with... Thanks! Scott S |
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| IronHillRestorations |
Jul 5 2009, 11:18 AM
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#2
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I. I. R. C. Group: Members Posts: 6,813 Joined: 18-March 03 From: West TN Member No.: 439 Region Association: None 
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As long as the carbs are optimized for the engine, you shouldn't give up too much or any HP over the CIS.
The CIS engine you've got is by comparison, low compression, and cams with virtually no overlap. It works well, but it's not the highest performance branch on the tree. CIS is a decent system for a street car, and doesn't have idle jets to clog up. CIS and MFI have been lumped together, which from a performance perspective isn't correct. CIS and MFI are totally different systems. With MFI you can run a high compression engine, and cams with more overlap. The MFI pump puts out about 240psi at the injector which gives you killer throttle response, but the lack of any vacuum or intake pressure sensing can result in surging throttle response, ie part throttle down hill (low load) compared to part throttle up hill (load). |
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Posts in this topic
Scott Schroeder 2.7 CIS to Carbs - how much HP loss? Jul 2 2009, 03:15 PM
brant Scott,
I heard about that motor
seemed like a re... Jul 2 2009, 03:20 PM Cupomeat I cannot support the following with empirical evid... Jul 2 2009, 03:21 PM turboman808 From what I have seen on graphs you get peaks and ... Jul 2 2009, 03:46 PM carr914 I would think that you would H.P. & Torque wit... Jul 2 2009, 04:43 PM 9146986 Why not just keep the CIS? Jul 2 2009, 10:11 PM pcar916 When I bought my car it had a 2.7L motor built up ... Jul 2 2009, 11:13 PM GeorgeRud If you don't have it, I would get Bruce Anders... Jul 2 2009, 11:29 PM ahdoman If the CIS is intact and working stick with it. Yo... Jul 3 2009, 12:10 AM carr914
When I bought my car it had a 2.7L motor built up... Jul 3 2009, 06:15 AM
pcar916
[quote name='pcar916' post='1188039' date='Jul 3 ... Jul 3 2009, 07:45 AM Project 6 Wayne at Pelican claims to have installed a CIS mo... Jul 3 2009, 07:50 AM J P Stein I know a few folks that run Webers on an otherwise... Jul 3 2009, 08:51 AM Gint I'd probably just use the CIS. But if you buy... Jul 3 2009, 08:53 AM scotty
I know a few folks that run Webers on an otherwis... Jul 3 2009, 10:28 AM naro914 I have a 2.7 in Huey at the moment, with Webers. I... Jul 4 2009, 10:56 AM Mountain914 Just want to throw this out there - since the titl... Jul 4 2009, 11:44 AM J P Stein
Just want to throw this out there - since the tit... Jul 4 2009, 01:38 PM ArtechnikA
A good illustration of the possibilities of the 2... Jul 4 2009, 02:02 PM J P Stein
A good illustration of the possibilities of the ... Jul 4 2009, 04:02 PM ArtechnikA
Yeah,yeah, some folks go all gaga over the MFI se... Jul 4 2009, 05:31 PM naro914 This is a good discussion....
I have carbs. I lik... Jul 4 2009, 04:14 PM J P Stein
This is a good discussion....
I have carbs. I li... Jul 4 2009, 07:12 PM |
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