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993.986.'s Avatar
 
Join Date: Jan 2004
Location: West Des Moines, Iowa
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Question early 911 throttle response

I am still in the process of deciding on an early 911 to buy. Taking the advice of this board I talked to a local Porsche mechanic who specializes in 1989 or earlier models only. He said two things that surprised me: 1) the 2.7 motor once properly built is one of the best engines Porsche made (it might take over 10K build it this way), and 2) that a PMO carb set-up, on the earlier engines, would have much better throttle response than a fuel injected engine. I am still learning but I I have always thought just the opposite about those two things (especially the carbs). What's the consensus of your experience?

thanks, Lester

Old 02-02-2004, 08:58 PM
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There are two 2.7 motors. One was the one used in the 1973 Carrera RS and the Euro Carrera of 74 (and 75?). It's a 210 hp motor, with mechanical fuel injection, and is something of a legend among Porsche powerplants. Then there's also the 2.7-liter motor that was used in the US-market cars from 1974-1977. It had CIS injection (called K Jetronic), and produced less power (150, 165, or 175 hp, depending on the model) than its famous predecessor. After 1975, US emissions laws forced Porsche to put thermal reactors on the 2.7, which pushed the already-stressed magnesium toward overheating. Headstuds tended to pull out of the soft magnesium.

A properly rebuilt US 2.7 is a very good engine, but it's not the same as an RS-spec 2.7, which had a different case (I'm pretty sure), and a number of other unique features. Hopefully, someone with more knowledge about this will correct me if I'm wrong.

MFI is the fuel injection system famous for its throttle reponse. Later schemes were less crisp, generally, but more emissions-friendly.

Last edited by Jack Olsen; 02-02-2004 at 09:12 PM..
Old 02-02-2004, 09:07 PM
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Throttle response is somewhat subjective, but in my limited experience, MFI rules. Webers (incl PMO clones) are a close second and are perhaps superior in the auditory sensation aspect, which is a big part of the early car equation. Everything else i.e. CIS & Motronic just isn't quite the same....although I have never (yet) driven a high-end programmable EFI car such as Motec/Electromotive/Haltech. I suspect they are a different ballgame altogether.
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Old 02-02-2004, 11:13 PM
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Alpha-N driven EFI would give you near-instant throttle response and infinite tunability. It doesn't run as high injection pressure as MFI (altough nothing keeps you from using high system pressure and small injectors) but i doubt it's such an advantage...
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Old 02-03-2004, 05:18 AM
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PMO's and Webers (when properly set up) can have really good throttle response. But a properly set-up MFI will be better still! Trust me, I've driven both. I personally think that MFI sounds as good if not better then carbs.

As far as the 2.7 being one of the "Best" engines Porsche made, it sounds like a little bit of salesmanship to me. If you ask me, all of the air-cooled 911 motors are very much the same from the driver's seat. It's just that the larger ones have "more". This is especially true when you compare pre-CIS engines to each other or EFI engines together. From a reliability perspective, the answer is much more complex and is constantly being investigated further on this BBS.

Rather then take one person's opinion as gospel, I'd try to test drive as many different versions as possible to see what you like best within your price range. Some people love the reliability of the CIS and EFI'd engines, some people love the aural symphony of the carb'd and (better yet) MFI'd cars. Some people say "toMAHtoe" and some say "toMAEtoe"

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Old 02-03-2004, 05:30 AM
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