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944S2 DME Coding Plug (California/Japan) Power Difference?

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Old 01-05-2011, 11:44 AM
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Eric_Oz_S2
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Default 944S2 DME Coding Plug (California/Japan) Power Difference?

My S2's DME has a 928.607.421.00 coding plug installed (variant switch). The FWSM states this is for California and Japan (although it is an Australian delivered car).

Has anyone pulled out one of these and and noticed a difference in performance? If the Cal and US/ROW cars state the same power, why wouldn't the rest of the world run the Cal maps, which presumably are tailored for lower grade fuel and/or lower emissions?
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Old 01-05-2011, 09:11 PM
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Anyone?
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Old 01-05-2011, 09:30 PM
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Hi Eric, see my post on the other thread.

Cheers,
Mike
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Old 01-13-2011, 12:17 AM
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Found this on the interweb:

"California and Japan cars jumpered the pin 10 brown wires by the DME reducing overall ignition timing by an additional 3 degrees in addition to further leaning part throttle fuel enrichment, lowering emissions further with a corresponding reduction in performance (California versions at 200 hp and 6.7 seconds)."

This is in relation to the 911 3.2 Carreras, so it is not clear if Porsche used a similar approach for the 944. The 944 coding plug certainly jumpers pin 10 on the ecu as well though.
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Old 01-14-2011, 03:21 AM
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Pulled the plug - no noticeable difference. My dyno-bumometer might not be properly calibrated though.
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Old 01-15-2011, 11:12 AM
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Eric -- I pulled my DME today to check my FQS setting/swap DME chips, and while I was in there, I checked for a plug. There are two sockets (one white, one black) where you suggested I'd find it if it was there -- both empty.
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Old 01-15-2011, 11:35 AM
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Mine was installed in the white plug. Maybe it was only installed in the MY89 cars?

Mark, while on the subject of DME and FI - suggest that you might check operation of your TPS. Yours may be OK, but from what I have read they tend to fail with age. Mine was full of coolant, but besides this there were a couple of dry joints inside. It is easy to test with a DMM using the continuity (buzzer) function. It is interesting that the car runs reasonably even with the TPS disconnected - so much so that it has taken me over a year to realise something wasn't quite right and fix it.

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Old 01-15-2011, 12:06 PM
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Originally Posted by Eric_Oz_S2 View Post
It is interesting that the car runs reasonably even with the TPS disconnected - so much so that it has taken me over a year to realise something wasn't quite right and fix it.

Eric
Remarkable. I'll test mine and let you know what I find.
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Old 01-17-2011, 03:02 AM
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I tested mine out, and it checked out as it should.

When I read up on how these work on the S2, I was less surpised you had been running an inop one without too many problems. On the S2, they only provide info on two special throttle positions: fully closed (i.e., idle), and fully open (i.e., WOT).

Just before the throttle closes you can hear a slight click from the TPS, and contacts 2 and 3 switch to closed (otherwise open). At just before full throttle, contacts 1 and 2 close (otherwise open). Didn't hear a click here though, but it registered on the MM. At all other partial throttle positions (where, of course, you spend 95% of the time), both sets of contacts are closed, and it would make no difference at all if the TPS was completely unplugged.

Turbos are different though, the DME needs continuous partial throttle position info from the TPS.
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Old 10-11-2011, 10:50 AM
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Just to cap this thread off. Using my Ostrich, the Japan/Cal coding plug only affects the PT ignition maps, PT fuel and WOT maps are not affected by having the Japan/Cal coding plug in.

The change to PT timing is only in the lower RPM ranges (under 3000) and lower loads. The timing reduction is up to about 3 degrees IIRC. So it would not affect power, but would slightly reduce throttle response. I wonder if this was done for emissions or fuel quality?

Last edited by Eric_Oz_S2; 10-11-2011 at 07:33 PM.
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Old 10-11-2011, 11:27 PM
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Eric,
What about the lambda tables?
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Originally Posted by Duke View Post
I whisper "Bob Norwood" in my engines intake before every startup. Instant boost of power!
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Old 10-12-2011, 12:48 AM
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I'll confirm this when I get a chance, but I recall that they both used the same lambda tables.

I'm also going to modify the plug and see what tables the "non catalytic" version has. Lastly, there is also an unused 2 pin coding plug (I presume a carry over from the earlier 944S) attached to the harness. Might short this plug and see what maps this uses.
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Old 12-06-2017, 11:19 PM
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Old thread, but:
I have a 91 944 S2 RHD drive race car, I believe originally a japanese market car. It has no O2 sensor (wires bridged) and no cat.
The two coding plugs are as shown - I'm still trying to find out what they actually mean:

2 brown wire black plug


3 wire plug
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Old 12-07-2017, 06:41 AM
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That's the M150 leaded gas (no o2 sensor) plug bridging white and brown. That's not the japan model plug which bridges the other 2 wires in that 3 pin plug.

The black plug is a characteristic switch which can be used to switch maps. The black plug was only used for Australia according to the workshop manual.
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Old 12-07-2017, 08:29 AM
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Hi floatingkiwi, I have a 1991 ex-Japan RHD S2 as well, in road trim. Let me know what you would like photos of.

Cheers,
Mike
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