3.6 Conversion DME and Wiring Questions

[William Miller]

1991 964 intake / montronics going into a 1981 SC.


I was on vacation last week and while my wife read 2 books I studied wiring diagrams.

My plan was to confirm a lot of information that I've seen here and on other sites and try to really understand my conversion plan before I build my own conversion harness from pieces scavenged off the doner car.

My overall plan is to build a street / DE car.
I want all the bells and whistles including Air Conditioning.

I have almost all the plans sorted out except for some details on the harness.
I could possibly spend a week searching thru all the threads I've read over the last few months, but most were not specific enough to this conversion.
I thought i would combine my questions into one thread.
Please respond to a specific question or to a group if you wish.

1. On Timmins site it mentions something about modifying the A/C compressor bracket. (Making it shorter, I think) Is this so the engine lid will close? I have some 1" spacers for the rear engine mounts which will lower the engine. (I assume this is so it will work with the 3.6 engine tin.) Can anyone add some clarification?

2. Does anyone know the correct gap for the flywheel sensor? I'm using a 89 C4 flywheel that was machined for the SC Presure plate and I do have the correct sensor bracket.

3. Is there any reason not to backdate the oil temp and pressure gauges to the numerical type. I have a matched set (gauge and sensor) from a '74. Will it just screw into the breather cover where the other one is located? (I haven't really looked closely so this may be a dubm question.)

4. Wiring Diagram questions: (911 C 2/4 Model 91 Sheet 5 )
There are 3 interesting things on the disgaram that I'd like some history or explanation on. (I've seen some related discussion regarding a 3.2 DME)

a. 2 pin Map Alteration Switch: (Located G42 on the diagram)
(This is really just a connector near the DME.

b. Variant Identifikation Switch: (located next to above on the diagram)

c. Oxygen Sensor Bridge: (located B49 on the diagram) The note for the O2 sensor shows that is for Cat. Conv, only. The part number for the bridge is 944.612.422.00

These items raise the question that is it possible that the 91 DME has different maps which are switched based on if and how these conectors are handled? I believe that they are all truely present on the harness. I just need to double check.

Clarification: Although this is a street car I have it registered Historic in Maryland and thus there are no inspections or emissions tests. (I also think this possibly will run cleaner than the MD requirements for emissions even though it will not have a Cat.

d. How do the "k" and "L" dignostic circuits work? There is a wire linked to the following items and a lead to the diagnostics connector: DME; Alarm/Lock Controler; Speed Sensor; ABS Controler; A/C, Heat Controler.

5. I will be wiring a Check engine light per Ingo's diagram.
6. I will be wiring a v-belt light per Ingo's diagram
7. What would be the best way to disable the car using an aftermarket alarm similar to a VIPER. (I assume something connected to the DME relay?)
8. Ingo mentioned somewhere that one of the DME terminals was used to sense if the A/C was on. Thus it adjusts the idle? Can anyone elaborate? I see 3 terminals that mention A/C (40,41 and 50) I'd pick 50 , but what do I do with it?

9. I'm going replace the rear fuse/relay panel during the conversion. I'm going to mount the coil packs in front just like on the 964. Will there be enough room for fuel filter on that side or should I put it on the other side like on the 964?

Thanks for any help!

[Porsche84]

Bill

I have done 4 or 5 3.6 conversions The coils fit next to the fuel filter on the left just fine. Take off the rear fuse box, you will not need it and it cleans up the install.

Do not use the 1 inch spacers, you'll hate the look. Take the time to modify the tins and make it fit properly.

Be careful on the temp gauges. I'd take the sender and put it in boiling water to see what the gauge indicates. The 964 senders might not be compatable with the 74 gauge

Cutting the 964 A/c bracket just makes the engine look cleaner, assuming you are not using AC. I think I have a photo if you want to see what to do.

I have many notes on wiring so e-mail me anytime you get to that and I'see if I can help

Good luck with the conversion

[johnsjmc]

I,ve done one and without a kit. The space between the flywheel and sensor should be about .8 mm. I think you may need to alter the sensor mount to achieve this with the 1989 flywheel..
My AC compressor seems to fit OK but isn,t in yet as I need to make up adapter hoses from the body.I used a 1/2 in" rear spacer.
I am eventually going to add a check eng. light and a RS alt pulley will negate the need for a belt light.
My oil pressure guage is low at high revs and I am going to replace the sender with a new SC type to hopefully fix it.
I am using a single O2 sender and a Steve Wong chip for a 964 with 993 exhaust and light flywheel.I think a O2 sender can give you better drivability and mileage.Chip tuning is done with the knowledge the sensor is active.

[William Miller]

First I wanted to say thanks for the support!

Confirming 0.8mm gap on the flywheel sensor. (I do have the correct bracket for the 89C4 which is the flywheel I'm using. It's all mounted and just waiting for adjustment.)

On the fuel filter, I bought an assortment of AN fittings from BAT in Florida, but haven't located an adapter that will simply screw into the SC hard fuel lines. They are metric female fittings. I have 2 fittings that will weld onto the hard lines converting them to AN fittings. (I'm willing to do this if I can't find a simpler solution). I read somewhere that Timmins supplies a barbed fitting for the return and you just cut the existing return hose and insert the barbed end with clamp. I also have the 964 fuel filter and mounting bracket off the donor car and can mount it behind behind the oil filler pipe where it was located on the 964.
What do you guys use for these adapters?

On the A/C hoses. Griffiths sells a manifold that bolts on the side of the 964 compressor. I bought this along with 2 conversion hoses and a new dryer. I'll be converting to 134 at the same time. one of the hoses has a dual pressure switch. In Maryland it's not that hot and I if I need to upgrade other stuff later that's no big deal because the 134 refrigerant is relativly cheap.


Can you guy's explain a little about the engine tin modification?
(BTW, the block on this engine is a 993 which doesn't have the balancer on the pulley.) I'm using the aluminum engine cradle mount that was on the engine and I cut the ends off the steel cross bar. I then took an old SC cross bar and cut about 10" off each and and welded those ends onto the foreward side of the 964 cross bar. This sort of creates a box section enclosing the area where the 964 cross bar is had the top and bottom formed going forward. The SC ends have the threads in them which will make it easier to work with in the future. (I keep anti-seize on them!) I have not bent the bar foreward yet, but the ends are about 1/4-1/2" farther forward than on the 964 set up.

The engine had the 964 tin on it. I already cut the heat sheild that sticks back off there rear piece. (I'm also using the 993 aluminum heat cross tube and 993 heat exchangers. This is all finished including adapters reducing the heat outlets and the flexible SCAT or SCEET hose. On the front, I cut the Power steering pump bracket flush with the top of the 964 tin at the corner and caped the opening at the top with sheet metal.
So what other Tin modifications should I consider? I'm especially intrested in what is needed to be able to eliminate or reduce the engine mount spacers.

On the oil temp and P gauges. (To clarify, I have a complete matching set from the 73.5 / 74 should I assume they should work if I'm not missing something. I have noticed since I wrote yesterday (I looked at a picture I had) It looks like the pressure and pressure switch are combined on the 964 and the temp sender looks like a typical sender. They are all mounted on the top of the engine thermostat. It looks like the Pressure sender and switch have a big base (threaded connection) simulat in size to the SC, but I think the sender from the 74 is smaller. Can anyone confirm this? is there an adapter for this?

Can you guys expand on the use of an O2 sensor?
I am not going to be running a cat.
Anybody know about the 964 DME and the map alteration switch?

[FenderGuy]

Bill

you are using 993 exchangers and what muffler are you using?

I've been emailing Steve and he says I can use a pair of Carrera exchangers I have but need to fab a muffler?

[Joeaksa]

Frank,

We need to have lunch when I get back to Phoenix. I have Bill Verburg's old 1992 964 3.6 in my 911 and have had sooo many exhaust systems on the car that I am tried of hassling with it.

Now am looking at using some 993 HE's (with flipped flanges on one side) so that it will give me heat as many of the conversion guys are doing.

You can use SSI's, B&B's or the 993 setup, as well as plain headers (with no heat) on this engine. Do a search and you will come up with lots of info.

My problem is that I have backdated my 85 911 to look like a 73 RS and the exhaust that works well with a standard 911 and a 3.6 are in many cases too close to the bodywork in the back on my car.

Considering that Patrick Motorsports is right in town with us you should talk to him as well. I did and he saved my buns while doing my conversion after a less than good experience with Timmins. Do a search on this character and sure you will come up with lots of interesting comments. For many years Timmins used Patricks parts on his conversions, so Patrick knows what he is doing with the 3.6 conversion.

One thing to remember is that what works in one place may not work in others. Frank and I live in Arizona and there is a sniffer test every two years and if your car had a Cat on it from the factory, its supposed to have one now. Many people have taken their 911 into the station to be checked and passed as the examiners do not know a heat exchanger from a Cat, and the engine runs clean if tuned well.

Several of the guys in SoCal have very interesting exhaust setup's that are well worth looking at as well. Might do a search on that.

[William Miller]

I'm slowly working with Ben McFarland (MB911) on a prototype. Ben has a few sucessfull 3.6 mufflers out there, but not with the setup that I have. I'm keeping the stock engine mounts and crank pulley along with using the aluminum 993 heat cross over tube and no Cats.
I recall only 2 other (bolt-on) options out there:
1. Timmins Happy Crab
2. Triad

There are many variations on fab-ed up mufflers including set-ups with Cat's.

I'm using a 915 transmission and I understand that the Carrera and 964 heat exchangers won't work because the cross over tube interfears with the 915 clutch shaft /arm mechanism.

[Joeaksa]

Bill,

I have emailed with Ben in the past about his making a muffler or muffler/Cat that would bolt onto a 964 with 993 HE's. At the time he was not ready to make one but hope he is now.

His quality is excellent and its hard to beat one of Ben's exhaust systems.

There are many other options out there, like SSI's with a stock banana muffler, or B&B's that will fit. Just depends on what you want. Some have trade-off's and some are bloody expensive. Wish Ben would rig something up for us conversion types!

Joe

[William Miller]

Joe, they are also very lite!
Ben has been very easy to work with and has been very patient with me.
Because I'm using the stock aluminum engine carrier and the aluminum cross over tube, the cylindrical shape of Ben's Muffler is not exactly the best for the space provided. Timmins uses a oval shaped muffler as his base which is an easier fit. (I wonder what muffler it is?).
I have faith that we will get something to work. It would be much easier with the engine actually in the car. We could then mount the muffler where it fits best and then run the tubes to it.

[Joeaksa]

Bill,

You are doing what I did, get it in and go from there. Personally I feel that Ben's product would be best if it will fit in your car. Let me get MikeZ in the thread and see what he is doing now. He has fabbed up several 3.6 exhaust systems in the past.

Joe

[DW SD]

Joe,
I run Ben's 993 Heat Exchanger in an early car. My engine is a 993 derivative. I have dual exhaust outlets, but the outlets are movable. I do not run the heat X-over pipe, though I will run heat. I'm working on the heat solution, now. I'm actually planning to run heat only through one Heat Exchanger. I believe that will be plenty for me in Southern California. Defrost is really my only need.

Ben has the jig for the 993 Heat Exchangers and it fits well. Search on the 3.6 exhaust thread for some pictures of my setup. I'm on vacation and don't have all of the pictures on my travel computer.

William,
Without an O2 sensor, the engine has no feedback with which to adjust air fuel ratios. This is called closed loop and will gain you mileage. At WOT, the air fuel map is set as is timing, so it shouldn't effect performance. In open loop mode (no feedback from O2 sensor) the engine will always light the Check engine Light. If you plan to run this, you need to make sure it runs in closed loop.

Talk to Patrick Motorsports about the fuel line adaptors. I'm pretty sure he has them. I actually converted at the outlet of my fuel filter to AN. From there, I have a barbed fitting which was swaged onto -6 AN to adapt to the 993 fuel rail. Except for the braided stainless on the hose, it looks factory and is robust.

The combination sender on the 964 / 993 is oil pressure idiot light and oil pressure sender. The individual sender is the temp sender.

My understanding on the gauges is that Carrera gauges work with the later senders. Earlier gauges don't work. You can setup a test jig (easily) to dunk the sender in water. I also setup a test jig to confirm pressure using a regulator and my air compressor. Those worked for me. YOu could also have one of the speedo shops modify to suit your needs.

As a simple solution, I think you can find a Carrera oil pressure gauge and install it. The idiot light simply offers continuity below 12 psi, so the light itself if you consider it a gauge is as simple as it gets. Finally, you can use the temp sender compatible with your gauge (buy it here) and you should be good to go. The threads are the same in the sender block. Just use new crush washers.

Doug

[Joe Bob]

911 C1 - 3.6 engine. Exhaust/Heat questions???

Go here....

[Joe Bob]

My 02 sensor is on the right side in the middle...can't see it, but it gets the mixed gases from both sides.

[William Miller]

Doug, yours is simular to what Bem sent, but the aluminum engine carrier is deeper than the one you are using. The 1st one Ben sent me didn't fit because of that. I put a big dent in it to clear the mount, but denting it in pulled the flanges in so they no longer mated with the heat exchanger flanges.
I sent if back and have a second one that he put the depression in and it's not quite right. I think we need to go back and do it the way you did, have ben ship the pieces and I can tack weld it.
This will wait until the winter because I'm still driving the car while I sort out the last few things.

[FenderGuy]

Originally posted by Joeaksa
Frank,

We need to have lunch when I get back to Phoenix. I have Bill Verburg's old 1992 964 3.6 in my 911 and have had sooo many exhaust systems on the car that I am tried of hassling with it.

Now am looking at using some 993 HE's (with flipped flanges on one side) so that it will give me heat as many of the conversion guys are doing.

You can use SSI's, B&B's or the 993 setup, as well as plain headers (with no heat) on this engine. Do a search and you will come up with lots of info.

My problem is that I have backdated my 85 911 to look like a 73 RS and the exhaust that works well with a standard 911 and a 3.6 are in many cases too close to the bodywork in the back on my car.

Considering that Patrick Motorsports is right in town with us you should talk to him as well. I did and he saved my buns while doing my conversion after a less than good experience with Timmins. Do a search on this character and sure you will come up with lots of interesting comments. For many years Timmins used Patricks parts on his conversions, so Patrick knows what he is doing with the 3.6 conversion.

One thing to remember is that what works in one place may not work in others. Frank and I live in Arizona and there is a sniffer test every two years and if your car had a Cat on it from the factory, its supposed to have one now. Many people have taken their 911 into the station to be checked and passed as the examiners do not know a heat exchanger from a Cat, and the engine runs clean if tuned well.

Several of the guys in SoCal have very interesting exhaust setup's that are well worth looking at as well. Might do a search on that.

Joe

I am waiting a call back and quote from Jim, I had emailed Steve before to get some basic info...so far its been imformative...I won't make a decision untill i am sure its the right way to go

When you heading back into town?

[William Miller]

complied this diagram from a bunch of places.
Somewhat benchmarked off of the one Ingo had on his site.
The one mystery is if the green/black wire on T16 is the one that I use to increase the idle. If so, how should it be hooked up?

I hope this comes out so it's readable!

EDIT:::::::
I eliminated the diagram because it has been updated below..

[Porsche84]

Here is a 993 exhaust I installed on a 3.6 (964 engine)conversion using a Flowmaster muffler. I have done a bunch of exhausts using this muffler (88 Firebird, twin 2.5 in and twin 2.5 out). This is the only 993 header exhaust I've built. I actually capped one out pipe and made a tailpipe to come out of the stock SC location
. .

This picture shows the way I bring the exhaust out with my headers. The Flowmaster fits perfectly behind the 911 engine

[FenderGuy]

Jerry

Thanks for the pics

[William Miller]

These are the '91 964 to 81 sc engine to car and engine to DME harness conectors:

[William Miller]

Jerry, Nice work on the exhaust!