83 3.0 replacing 2.7 in a 76 car....lambda questions

[speedo]

Couple questions too vague to do a search....Motor came without a lambda cable, so I had to source a cable. Motor is in car and running...but rough. Have a few questions...

1) where do I pull my tach signal, from the CDI?

2) my o2 sensor is a one wire sensor. The cable to the Lambda unit has what looks like a thick green wire, which ends up when opened up looking like a coaxial cable with an outer wire and a "sheathed "inner wire. Is the inner wire the one that should be connected to the single wire off my o2 sensor?

3) I have 2 red wires...(one red solid and one red with a white stripe... which I presume to be switched hot). The PO of the cable said these wires went to the fuse panel in the trunck and were not "live". I want to run these to the fuse panel on the CDI console. I can pick up a hot red, but if the red/white wire needs to be a "switched hot", where do I get that?

4) the motor surges at idle, runs smooth to about 2000 rpm...remember that I have no tach reading yet...and then has no power...seems to run rich ....exhaust looks to be blackish.

Thoughts? Thanks for your help.

[Jim Williams]

Speedo,

Seeing as how no one answered, thought I would......

Questions:

What lambda cable are you referring to in the first paragraph? The one from the control unit under the seat, or the one from the O2 sensor to the control unit?

1) The tach signal will come from the CDI, I think is a black/purple wire. I can check a wiring diagram to make sure of the color.

2) Yes, the inner wire of the coax goes from the sensor to the control unit.

3) Where are the these two red wires located, what cable?

4) Are you running the engine without the Contol Unit connected? I am having a hard time visualizing what you have connected to what. The factory wiring diagram should go a long way in helping you figure out what needs to be connected to what: A diagram from the '76, and one for the '83. Does the frequency valve of the CIS now get a signal from the control unit? If it gets none, the CIS will be running lean, unless the mixture has been manually adjusted rich.

Since the '76 tach took a signal from the points, and the '78 and later took the signal from the CDI, I think the two year model tachs are not compatible.

[speedo]

Jim,

In all my discussions, I am refering to the cable that goes from the Lambda unit into the engine compartment. For the time being, the cable is connected to the car/motor, although in appears to be inoperative.

I leaned the car tonight using the mixture screw in the CIS and the idle smoothed out nicely. I still get a balk at somewhere near 2000 rpm..., but the black smoke is gone. The idle did increase, and I tried the idle adjustment screw, but it seemed to "bottom" before doing any good. Motor starts and revs great to 2000 then loses power.

The two wires I was referring to are the red and red/white wires that should be connected to the trunk mounted fuse panels. One appears to need hot, (red) and one switched hot (red/white).

The tach in the car is a stock 76 tach...do I need a later(78-83) tach, or can I pull a blk/prpl wire off the 6 pin and get the info to the tach?

Thoughts? Thanks for the help...it is getting better!

[Jim Williams]

For starters, a wiring diagram which may be of some use to you is one on my website. Click here.
(Scroll down to the second diagram.)

The small box "III 9" is connected to the power source -- red wire. This source, wherever you pick it up, is "hot" all the time, and preferably fused.

The other box, "I 13" is the red/white, going to the switched power source.

I don't recall where these connections are physically made into the cable.

As far as the performance issues with the engine, a Lambda equipped engine will never perform "right" with the Lambda electronics disconnected, *unless* other mods are made to the CIS to help compensate. It sounds like you are on the right track getting the Lambda system connected.

Hope this diagram helps.

On the tach issue, just connect the black/purple wire from the 6- pin CDI to the black/purple on your '76 harness and see if the tach works, if it does, you're home free, if it doesn't you won't have damaged anything, and you'll need to find a tach from a '78 or later SC.

(Edit to repair link)

[pookie]

I can't help on the other wiring because I think I would only screw you up more, but I have an 81 motor in my 76 and the tach issue took me forever to sort out. The tach wire like Jim said is the blk/purple wire. Like Jim said you can connect directly to that and see what happens. I ended up putting an MSD ignition on my car which gave me more tach issues. Eventually I ended up getting an Autometer Tach and running a wire directly from the tach to the MSD, not converter or adapter, straight to the box, and everything works. Did you switch to the SC fuel pump or keep the one from the 2.7? My car was bogging down really bad once I did the swap, but after trying everything else I switched the fuel pump and it worked. Not really sure if any of that helps, but I feel your frustration with the swap. I've got an old article on it somewhere if you'd like me to send you a copy.

[Jim Williams]

I noticed the link I posted to the web page was not working. I repaired it, so it opens now to the wiring diagram.

[dd74]

For what it's worth - and I'm just going to throw this out - but I replaced my 2.7 with an '83 3.0, and in doing so, bypassed the lambda system altogether. Also, we used the OEM tachometer with the 3.0. How it was done - I don't know? But if interested, PM me, and I'll give you the name of the shop that did the swap.

The most I know about lamda is it's used for smog reasons. If that's the case, isn't this year the last year cars from 1976 have to be smog tested?

[pookie]

I forgot, like dd74 I don't have the lambada either.

[Jim Williams]

dd74,

Since I see this question of eliminating the Lambda system from the '80 to '83 SC's, and don't ever seem to see what has been done to the CIS on these conversions, I would appreciate hearing what those such as yourself have done (or have had done).

Some people apparently just remove it expecting no negative effects on performance. Since the Lambda engines depended on the Lambda system to do acceleration enrichment, and to aid in warmup enrichment, some changes and adjustments are obviously necessary.

Perhaps you could find out in general terms what the shop did to your car, and post it on this thread. I know that there are others like myself that would be interested.

[speedo]

Spent 3 hours today on the clock trying to "dial in" my Lambda system and I'm right back where I started. Either there was a ghost in the control unit, or I'm going nuts. WE tested the Lambda control unit, the O2 sensor, the frequency valve and found that at times everything was operational...then the frequency vlave would not operate at all. We replaced the relay on the control unit and it would operate the frequency valve...then not. We would lean the mixture and then the lambda unit would stop working. This O2 sensor is a result of the DOT restrictions placed on Porsche to meet emission restrictions. Driving back up the mountain tonight....$250 poorer...the car ran terribly...with black smoke pouring out of it's exhaust!!

Plan B. I have heard that if you replace the mixture control with the same from a 2.7 (1977) you can remove the frequency valve, and the entire Lambda system. Well, the motor that died in the car was a 76 2.7 that ran great till it grenaded...so I have the replacement mixture control unit.

If I pull off the mixture control....and replace with a 76...and remove all the Lambda stuff...the car will operate with the same CIS capabilities as a CIS 2.7.

Will the fittings on top of the mixture control unit bolt up?Can I replace just the mixture control, or does it need the throttle body to be replaced also. The 2.7 had banjo fittings, and the 3.0 does not. Also, the 2.7 line (horizontal) from the warmup regulator looks like it goes to the return line instead of back to the mixture control.


The motor is so unhappy...It's killing me not to be able to exocise his evils...and frustrating that the shop could not either. It's a bummer when you start to think that you are smarter than the technician....or at least as dumb!!

[dd74]

Speedo and Jim, I'll call the shop that did the 3.0 for 2.7 swap for me, and see how it was installed without the lambda system. One thing I can confirm, was my '83 3.0 w/o lambda and with the '74 exhaust was putting out over 190 horsepower, and ran very well. So expect (hopefully good) news...

[Jim Williams]

Speedo,

Waiting on dd74 would be the best move at this point. I could suggest some things to do, but they would be untested.

I can suggest some things that are *likely*to work, but is for some reason they didn't provide a decent running engine right off the bat, and needed some refinements, you wouldn't be happy with me, and we'd be wasting the time that might have been better spent finding out from dd74 what actually worked for his conversion.

You may be able to block off the line from the fuel distributor that leads to the frequency valve. This would be the equivalent of the frequency valve trying to lean out the mixture, only more so. Then you would have to manually set the mixture back richer with the 3 mm allen wrench. Then replace the WUR with one that provides vacuum enrichment. All the above would be possible in theory, but I have no first-hand info that says how well this works, and if so, which WUR would be best in the this application. And trying changes like this might prove futile if your existing Lambda components are working only intermittently.

All that being said, let's use the same terminology for the CIS suff. It's OK to call the parts whatever one would like, but here's the terms most folks use for mixture control unit, etc.

Device that sits on the air box containing the air flapper: air flow sensor (housing).
Device that sits on the airflow sensor: fuel distributor.
I think somefolks call these two components when bolted together, the mixture control unit.

The throttle body for the 2.7 has a 56 mm butterfly, and the 3.0 a larger 63 mm butterfly.

On the other hand the airflow sensor for the 2.7 has a 80 mm sensor plate, and the 3.0 has a smaller 76 mm plate. Also, the venturi shape for the air flow sensor is slightly different between the two units.

So a reasonble guess, IMO, would be to use the 3.0 AFS and fuel distributor from a '78 or '79 and a '78 or '79 WUR if you were to mix and match parts.

The WUR return line for the '76 did go directly to the main return line back to the gas tank. The '78 and later return lines did go through the fuel distributor, but the return path for the gas was still back to the return to the tank. This method allowed the system to retain pressure better when the engine was shut down.

I hope dd74 can provide more insight as to what has apparently worked for him.

[speedo]

I moved my o2 sensor closer to the intersection of the three headers, and found a switched red for the harness. Motor starts easily then runs rough and dies. I tried leaning the mixture and it ...unlike before...got rougher and died. I tried enriching the mixture and it backfire all over the place. I think I am way too rich....and I need to just continue to lean it untill the rpms start to come back up. I found a misplaced wire in my engine-car 14 pin....my red-white was in pin 12 (tach) vs pin 10 (red/white motor). I corrected this and as soon as I did, the frequency valve came on and only shut down after I removed the 14 pin console plug in the rear. I am starting to dislike the frequency valve....tomorrow I replace the tach with a 3.0 tach and see if I need to re-do some more wiring....I love this electrical stuff...not! I miss my 2.7S motor....RIP

[fintstone]

No O2, lambda, etc on my Henry Schmidt prepped engine from Supertec. I think he sold DD 74 his engine too. Pehaps if you email Henry he could point yopu in the right direction. He only posts on the engine rebuild thread, but as far as I am concerned...he is the best there is.

[dd74]

Jim and Speedo - yes, Henry at Supertec installed the 3.0 in lieu of my old 2.7. I called him, and he told me, essentially, to install the motor without the lambda unit, you have to:

1) Replace the warm-up regulator with an older one - suggests an early SC WUR or possibly the one from your '76.

2) Block off the freqency valve.

3 Plug up any remaining lines/holes.

4) adjust your mixture.

This may or may not allow the car to pass smog, so keep that factor in mind.

If you have any more questions, this is Supertec's website.

All the best, and good luck!

[Jim Williams]

Speedo,

It sounds like my suggestions in my second post above and Henry's guidance are in agreement, so I'd think this would be a safe bet at this point.

I'd think an 033 or an 045 WUR would work. Remember to check which port is which on these two WURs, as the vacuum connections are reversed between the two.

If you replace the FV with a plugged piece of hose, you take care of plugging all the holes associated with FV removal.

Let us know how this works out.

[speedo]

I had a talk with John Walker who graciously spent some time discouraging me from dumping the lambda and bolting on my 2.7 fuel distributor.... Thanks John. I decided to forget everything the "pros" told me about the lambda system and the o2 sensor and how rich the car was running. I started by moving the o2 sensor forward to the hottest part of my SSIs ( I hated to drill into them and weld an o2 bung...). I then work VERRRY slowly and actually started to richen the mixture....and increase the idle. I finally got it to the point where it would not stall at idle. I kept increasing the mixture (over a full turn) and idle to the point where it would rev and sustain idle. The car runs great! It pulls from low rpm like the 2.7 did...but really picks up torque at 3000 rpm. Come to think of it...the car must have been ridiculously lean...as it was an east coast motor before I bought it! So...moral of story...don't believe what they tell you! DIY and get smarter than the shop...I know the shop didn't intend to take advantage of me...but he was in over his head. Upgrading motors is not something the average shop mechanic is used to....and as a lot of us have found out...we are kind of out there on our own. So, for the time being, I'll run the lambda.

Thanks seriously... to all the contributors.

If anyone has similar problems...I'll share what I have learned

[Jim Williams]

Runs like stink...but not because of the shop's help

Speedo,

Of course, you could have made the swap with parts from an earlier engine (expensive), but since you had the perseverance to keep looking for the answers to why your present system wasn't set up right, you came out a lot cheaper, and still have the good-performing engine the factory gave the car.

Many people don't understand the Lambda system, and won't take the time to learn it. Your post should serve as some encouragement for those who get frustrated with their Lambda CIS, that it can work right. And kudos to John Walker for taking the time to walk you through the problems.

And, just out of curiosity, I'm still waiting to hear what had to be done to those other Lambda CIS engines to remove the Lamda ECU, etc, and still have them run right.

[dd74]

Originally posted by Jim Williams


And, just out of curiosity, I'm still waiting to hear what had to be done to those other Lambda CIS engines to remove the Lamda ECU, etc, and still have them run right.

Did you read my post above?

[Jim Williams]

dd74,

I did read it. And I guess although I did apparently have a brain-f@rt that I had done so () , I was thinking that some more "been-there, done-thats" would chime in. I am still wondering if the Lambda fuel distributor, having been designed to properly meter fuel with the bottom pressure chamber bleeding off pressure at its normal 50% duty cycle, still does a proper job when it is blocked off completely. Perhaps it does.

Anyway, thanks for reminding me to read back through the thread. No intent to snub your post.