Stretching the CIS envelope......
 

I am in the planning stages of and engine build for my SC. Right now, I am considering: 98mm 10:1 pistons and cylinders, 964 cams, Electromotive Tec3 engine management, 3.2 cylinder heads w/twin plugs and............................*CIS injection! The Tec3 would be used intially for the twin plug ignition with the option later to add the PMO ITBs. With the relatively mild 964 cams, is there any reason that the CIS would not work on this engine? The TEC3 would take care of all the timing advance, etc. and would provide for spark knock protection. The CIS that is currently on the engine is working well and makes reasonable fuel mileage. The increase in compression should help offset the increase in displacement such that I would anticipate the fuel mileage would stay about the same as is currently being delivered. The engine already has SSI exhausts and since the tubes would be slightly restrictive at higher revs, I am looking for good bottom end and mid range torque. What do you guys think?*Thanks in advance

I think you will be fine.

http://forums.pelicanparts.com/showthread.php?t=166093

http://forums.pelicanparts.com/porsche-911-technical-forum/158331-dyno-results.html

Que the doom & gloom CIS sucks bunch.

I run 100mm Ps/Cs (short-stroke 3.3 baby!) with CIS + digital warm-up regulator, single-plug big-port SC heads, stock everything else except for SSIs and 2-in, 1-out. No problems so far, tons of torque and great drivability. Go for it.

Not a bad plan but here are some alternatives.

How about a great single plug at 9.5/1 CR with more agressive cams and PMO carbs now?
Your twin plug money sould get you close to a set of new carbs.
Could be 250-270+hp, not have to go back in to do it again, and a lot easer to tune.

Compaired to CIS it would feel like 300hp.

Actually, if you are interested in racing someday it migh be worth concidering building a SP911 motor as that is a fast growing and fun class.

That is bassically a 3.0 w stock late SC or euro pistons and carbs. They make around 230-245HP. They are low stressed and fit the stock gears well. Then spend the saved money on making he car lighter and handle better.

Just a thought.

Good input !................
 

Thanks, I appreciate the great input here. Looks like the short stroke plan will work just fine. I might even go to the 102mm barrels for a 3.4-3.5 ltr engine.

The reason for using the CIS is to help keep the mileage up. By spending the $$$ on the internal bits and pieces now, it will be easy later on to swap over to ITBs or carbs. The ITBs would be my first choice since the system would run off the TEC3 already installed. While I would love to be able to do it all at once, economics do have to be considered. I think that I could build the engine with the new P&Cs, cams, twin plug 3.2 heads and the Tec3 for about $12-13k. The ITBs later would add about $3-4k to that total. And, of course once the engine gets done, there will be a need for a brake upgrade, etc.

I love it when a plan comes together! (A-team)

Or, what about this option? There's a claim of better fuel economy as well as more horsepower - the link --> http://forums.pelicanparts.com/porsche-911-technical-forum/139422-cis-efi-kit.html

Have a look at his website too.

This is what I'm planning for my SC rebuild sometime next year, I'm also planning to go to a 3.2 SS.

I was there...........
 

Emcon5,I just noticed your location (SF). My son and I were there a few weeks ago for a Skip Barber driving school at Laguna Seca. We spent a couple of days in SF being tourists and then drove down Hwy1 to Monterey for the school. One of the best weeks I have had in a long time!

Just did this it is a great setup, I went one step farther I added the MS-1 extra firmware to get more options and a 12x12 fuel map and added EDIS ignition controlled by the megasquirt computer and I couldn't be happier and all for many hundreds (maybe even thousands) less than the Tec3 stuff give it a look Fred I think you would like.

Can you tell me where to find more info on the SP911 motor build? You can send it off the thread if you wish.

Thanks