CIS is a simple, but dated system.
It does compensate for pressure and air desity by measuring the mass of air past the sensor plate.
A modern day computerized fuel injection system is better because of the ability to map the mixture based on an almost infinite number of different conditions, and it does not have the sensor plate creating a "slight" restriction in the air flow. But, CIS systems make less HP on a N/A motor.
Having said that, i do like the CIS system when it is maintained correctly.
It is simple, bulletproof and cheaper to maintain, as long as the fuel is kept clean. You don't even need a laptop computer to work on it :-)
It has it's quirks, but that is part of the charm of my car, at least to me.
All the CIS systems on 911s are at least 28 years old and most are still functioning properly. We will have to wait to see if the motronic systems can match that reliability record without depleting the owner's bank account. Technology has come a long way, and shown great strides over the past 10 or 15 years. Maybe I am just too nostalgic?

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Gerald Gore II (Sam)
73 914 350 small block (sold)
80 911SC

[This message has been edited by sammyg2 (edited 11-05-2001).]

I'd certainly agree with sammyg2. My CIS system seems almost unstoppable despite major problems with my car's plugs, oil lines, vacuum hoses etc. But a system which could deliver a few more ponies and maybe improve mileage and emissions is very attractive (the emissions issue is actually pretty important to me). Carbs are clearly the "bolt-on" mod of choice, but they are very environmentally dirty. So in the search for a "bolt-on"-ish alternative to CIS, it seems this thread has revealed at least one scenario:

1) Intake: Natchamp's Beast has an intake manifold from a 3.2 bolted onto a 3.0 litre case. This is a very elegant solution. It uses an OEM part which provides Porsche quality assurance plus it incorporates an intake manifold which is already designed for EFI. Very smart. I notice that an inch had to be removed from the runners. Was this because of the intercooler? One wonders if a 3.2 litre intake manifold could be bolted directly onto a 3.0 litre engine. If so, then that would be sweet.
2) Injectors: I am guessing that Matter's SDS system used regular Bosch injectors when he says the systems uses a "standard bosch style injector harness." If this means one could use another OEM part, then that would rock.
3) Engine Management System: Everyone seems to have a favorite. The Beast has a Haltech E6K. Matter uses SDS. Matt Smith mentioned MoTec - obviously Porsche agrees. I've never heard of anyone adding it on after the fact. But why not?


So the big question is: What would this cost and how hard would it be to install? In other words, how would it compare to carbs? Honestly, if it came within a grand or two of the price of carbs, then I'd go for it if only to avoid the emissions hit.



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Janus Cole
1980 911SC & 1987 944

Janus, I used a 3.2L manifold for the reasons you stated. I lowered it by 1" for clearence purposes for the intercooler which would not be needed. However, to mate the manifold to the 3.0L heads I did have to add some material to the heads where the manifold seals/bolts on. I'm not sure if this would be needed with all 3.2L manifolds or not and it wasn't that much work.

The fuel injectors used are the standard double o-ring type. If you buy a 3.2L manifold you might get the fuel rails too which would work great. Or you could fabricate your own like I did. What is important about the injectors is to match their size accordingly to the engine configeration. I am not referring to physical size here, but their amount of fuel they spew. There are simple calculations for this.

You will get numerous opinions about EMS as you mentioned. One point of clarification in your note: Porsche uses Motronic which is not the same as Motec. Engine management systems are a whole topic of their own.



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Mark
The Beast
mark@hargett.com

Hey guys, nice discussion on the topic.

Just wondering. Has anyone used Webers as simple throttle bodies (delete fuel inlet and storage), then using an adapter under the carbs (possibly replacing the existing intake manifold to support/hold a fuel rail and injector for each intake port)?

I've got MFI heads (w/Webers) with plugs in the factory ports. Is there an EFI injector that fits, perhaps bore out to fit?

Sherwood Lee
http://members.rennlist.org/911pcars

One point of clarification in your note: Porsche uses Motronic which is not the same as Motec.
Oops ! My mistake. I was having a total brain fart when I typed that. Thanks for straightening that out. Since the 3.2 litre intake manifold and (possibly) fuel rails might be somewhat "bolt-able" to a 3.0 litre CIS engine, has anyone ever tried going the extra step and throwing in the OEM Motronic components? If salvaged from a wreck, then that might be a very cost-effective upgrade. Or maybe I'm pushing my luck.


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Janus Cole
1980 911SC & 1987 944

Sherwood, I have a freind that was going to try and do just that, use the carbs for the function of the throttle bodies only and out the injectors into the manifold below them. I think its a great idea and would look cool too. I also like the idea of having individual butterflys closer to the cylinders.



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Mark
The Beast
mark@hargett.com

I don't have a huge amount of details (ie I have never seen it in person) but this engine has MFI throttle bodies bored out to 40mm and adapted for use with electronic injectors (MoTeC controlled). I have no idea how tricky this was but I bet it was cheaper than a set of TWM bodies. You would just need to find a set from someone who has given up on MFI (ie if the pump is shot).

Actually, I am probably going to buy it, but won't get it for a couple of months http://www.pelicanparts.com/ultimate/biggrin.gif

http://www.pelicanparts.com/ultimate...LM911%203L.jpg

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Cameron Baudinet
1975 911S (in bits)
1969 911T

Since I can't stand the looks or the upgrade restrictions of CIS I've been doing some research on this. I very much like he idea of using the 3.2 intake setup. The throttle body approach is attractive but very expensive. Clewett engineering offers a fairly complete kit for the SC using the 3.2 intakes etc, for about $2,500 ( In the ball park with PMOs) with after market EMS. Check out Http://www.clewett.com go to Catalogue and engine management systems. I haven't contacted them for details yet.

Jeff C
81 SC

I have done business with Richard, he's a stand up guy. When you talk to him, ask him why he cut and welded the 3.2L manifold to have the inlet point in the other direction as seen on his website. The 3.2L manifols will fit in either direction. I was contimplating cutting mine to do the same thing until I realized it fit both ways.



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Mark
The Beast
mark@hargett.com

I just received my SDS system two days ago, for my '83 SC. I will be using Jenvey throttle bodies (www.jenvey.co.uk), which I expect to get sometime next week.

IMG SRC="http://www.pelicanparts.com/ultimate/image_uploads/sdsefi1.jpg"

II6:

Yummy! Tell us how it's working out for you! I'm also taking SDS-path as soon as my wallet allows it.

I'm thinking about using later Carrera-style intake with injectors and rails.

Are you going to lower fuel-pressure to 3-bar??

II6,

Please post some more pics when you get some I am VERY interested in trying this myself. I am thinking of trying to get a DME manifold instead of TB's. Also what comes on the ecu as far as mappings? Do you have to set the whole thing up from scratch?

Ben in SC

What type of sensors do you have to add as inputs to the brain.

head temp? position sensors? Is a MAF used?

I'm interested in this topic, but skeptical. Cause "real Porsches don't have computers" http://www.pelicanparts.com/ultimate/smile.gif



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Bill Krause
'79 911SC Euro
MY PELICAN GALLERY

I did a CIS to EFI conversion on a 78 3.0 a while back and used components off an 85 Chevy 2.8 V6.

What I ended up with was a very responsive, powerful and fuel efficient 3.0 that included all the "on board diagnostics", hot film mass air flow sensor, head temp sensor, throttle position sensor, computer controlled HEI ignition, Bosch injectors, complete wire harness, etc. all for less than $150 from the local boneyard.

I'll post some pictures of my modified intake manifold and air box later.

Fun winter project.

Joe Garcia
86 Carrera
Redwood PCA since 1976

[This message has been edited by stlrj (edited 11-07-2001).]

I'm thinking about using later Carrera-style intake with injectors and rails.

BeepBeep, I was thinking of exactly the same plan on the theory that "Real Porsches use Porsche parts." http://www.pelicanparts.com/support/smileys/lol2.gif Has anyone ever tried using that setup on a 3.0 using the OEM Motronic brain (maybe with 3.2 litre cylinders bolted on)? I am thinking that taking the entire air/fuel injection system from a wrecked 3.2 and "bolting" it on to my 3.0 could be cost effective and OEM. Is there any reason why I am way off base?


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Janus Cole
1980 911SC & 1987 944

What I ended up with was a very responsive, powerful and fuel efficient 3.0 ... for less than $150 from the local boneyard.

STRLJ: I stand corrected !! If you can tell us how you did this conversion, then I'll gladly give it a try. Sounds great! I'll have to modify my mantra to "Real Porsches go REAL fast."


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Janus Cole
1980 911SC & 1987 944

Here's my manifold, not as pretty as a 3.2 setup, but it's functional and cost effective.

http://www.pelicanparts.com/ultimate..._0014.JPG1.jpg

http://www.pelicanparts.com/ultimate..._0015.JPG1.jpg

http://www.pelicanparts.com/ultimate..._0016.JPG1.jpg

Joe

Joe,

Any more info on the model of FI that you used? I thought most of the GM FI was of the TBI type where the injectors sat on top of a central throttle body? Any pics of the setup after installation...

As you can tell many of us are VERY interested...

Ben in SC

Glad to see that picture, because now I know that intake manifolds can have curves in all directions. I guess all the intake manifolds for all cylinders must be same length though.

Wonder how this kinda setup (curved "pipes") will work for example with Holley which has this "central" for jets.

Joe, Can you elaborate on that a little bit? Is that just the CIS Airbox with the top cut off?

Tom
Curious as hell.

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82 911SC Coupe