How difficult is it to...?

cruiksdr · 02-01-2005, 07:08 PM

How difficult is it to to adapt a 3.0SC engine to an older electircal system? I have a 914 six with a 2.2/Webers. I now have a complete 3.0 with wiring harness, computer, etc. I'm thinking of converting to carbs, but wonder if there would be advantages to keeping the CIS. Carbs are simpler and yield more power, but CIS might be more reliable??? If I'm starting with the complete system, I'm just wondering what I'll need to do to adapt the wiring to my existing system.

Any thoughts???

Thanks!

masraum · 02-01-2005, 08:08 PM

I don't think that sort of conversion is hard at all. a 3.0 doesn't really have a computer. The injection and ignition are electronic, but not computer controlled. If you really do have a computer then maybe you have a 3.2L engine. They were the first 911's to have computer controlled fuel and ignition.

Many people have converted newer larger engines to carbs, so there should be lots of info on what you need to do. Generally it's much easier to take electronics off than to put them on.

aigel · aigel's Garage

Steve:

The 3.0 has a brain, if it is the later one with the O2 sensor. Isn't it time for you to buy an SC? That Miata must start getting real old.

Daniel:

I have not done such a conversion, but I own a late SC. I can tell you that the engine electronics are contained in the engine compartment, except for a small connector that goes to the front. Likely it connects the brain (located under pass. seat) and other minor things like the tach, oil pressure gauge and oil light. The main power for the engine however is fed through a large harness that plugs into the side of the engine compartment. Recreatiing those connections (must all be basic stuff), will be key.

You can skip the brain and the O2 sensor if you use this car for track and spirited driving. Setting the mixture a little richer than stock and undoing the 02 sensor will hurt your fuel economy a bit, but will wake up the system considerably. That will take care of the entire front connector, since you can hook up tach, oil pressure etc. individually.

The CIS will be sufficient if you are staying with the CIS pistons and just upgrade to mild cams, like the 964. With decent exhaust, that's 200 horse at the flywheel, no problem.

All you will need is a friend with an SC, lending you his bentley manual, along with the option to check out his car to see how things are wired up. If you don't have such a friend close by, start posting pics and detailed questions, and I am sure the SC guys here can help you out.

George

Andras Nagy · 02-02-2005, 03:57 AM

Hi Dan,

Have you seen the article in this month's Excellence, in which they write in great detail about converting a 914 using a 3.0 SC engine? Might want to take a gander.

randywebb · 02-02-2005, 10:43 AM

issues - pinout in the 14 pin connector
- whether oil pressure sender matches gauge in car
- whether oil temp. sender matches gauge in car
- will ignition system drive tach

nothing major, as no DME in CIS 3L engines

emcon5 · emcon5's Garage

If it was me, I would dump the CIS on the 3.0 and put the carbs on it.

I think the hardest part of adapting CIS to a non FI car would be the fuel supply. CIS requires a higher volume pump, and a return line. I know the stock carb fuel pump isn't up to it, and I don't think they had the return line.

Carbs won't give you any more power over CIS (probably improved throttle response) with stock engine internals, but I think the swap would be easier in a car that already has carbs. Assuming the 3.0 has the stock 6 pin CDI, all you really need to do is move the induction from one engine to the other, re-jet the carbs and slap it in.

Tom

randywebb · 02-02-2005, 12:58 PM

I agree - the carbs will be sweet even w/ the CIS cams. Jet them a bit rich.

cruiksdr · 02-02-2005, 07:17 PM

Thanks to all of you for the input. Sounds like the adaptation of the 3.0 w/cis would not be a big deal. But it also sounds like there is a bit of a bias of oppinion toward carb.

This, BTW, is an 83SC if that makes a difference. I have a set of Webers on my current engine which only need to be rejetted, etc. I also have the euro spec distributor, which I understand takes care of the ignition issues.

I think I'll stick with my first plan of going with carbs and sell the cis on ebay

Thanks for all the input!

aigel · aigel's Garage

From the CIS money, have the cams reground 964 profile. Camgrinder will hook you up!

George

emcon5 · emcon5's Garage

Quote:

Originally posted by cruiksdr
I also have the euro spec distributor, which I understand takes care of the ignition issues.

A euro distributor will still use the same trigger as the US cars. I assume your 2.2 has points (or a pertronix) driving a 3 pin CDI box. The SCs all used a 6 pin CDI box. As I understand it, points won't trigger a 6 pin, and the SC trigger won't work with a 3 pin. You can't mix and match the Bosch parts. If you have the 6 pin from the 3.0L, this isn't an issue.

A MSD will work with either.

I wouldn't screw with a cam change at this point. If you have to take the engine apart, swap in some JE pistons (for valve clearance), get the intake ports done (enlarged to early SC specs) and then change the cam to an early "S" or similar.

In a 914 that would be a rocket.

Tom