worf928

I suspect that you are both correct. Last night I was thinking along the lines of something S.A.-specific that needed to be modified for import to the US. IIRC, SA cars are not required to have a Catalytic Converter. (Not allowed, actually, since IIRC (again) leaded gas is used in SA.) I know that was true recently.

On a 'normal' USA GT the air pump diverter valve is connected to vacuum via the port underneath the throttle body. In the pictures it looks like the line from that under-TB port is butt-connected at the diverter and then run to the gizmo. The gizmo's output is then routed back to the diverter valve's vacuum input.

From looking at PET the interesting items are:

M 317 'equipment for countries with dust-laden air'

317 is the dust-trap setup in the air tubes.

M 298 'catalyst together with manual transmission'

I would assume that the GT in question does NOT have this code on the tank sticker.

M 900 - 'tourist's cars'

This option plugged the air pump diverter vacuum port and plugged the diverter's down pipe.

And PET Illustration 108-05 - 'air injection for cars without catalytic converter' shows a very complicated system that injects air from the pump diverter valve into the exhaust manifold. A photo of the system is shown on page 25 (aka 1-13) of the "Service Info Tech 87 S4" bulletin (from Jim's CDs.)

It would be interesting to have the option codes from the tank sticker.

I suspect at this point, that when the car was imported from S.A. that it had no cats and the above-mentioned air injection system. Cat's had to be added and the air injection system removed/modified to get air to the second stage of the newly-added cat.

However, the mystery gizmo still stymies me. If my suspicion above is true, then why wouldn't the air pump system simply have been modified to a USA-configuration? Why add the gizmo?

Mike, does your GT show signs of the secondary injection system? Perhaps some plugs in the exhaust manifolds? Maybe it is still on the engine?

Maybe the importer's 'mechanics' didn't know enough about 928s to know to remove and plug the secondary injection system and came up with this 'gizmo hack' to get air into the cats from the air pump valve?

worf928

Maybe the PO thought that by flipping the diverter to send air into the airbox he could get a little 'forced induction.' It's as good a theory as any at the moment. Too bad he didn't realize that that's what happens anyway with the stock system once the car's under high load.

mcholdfast

Here's a copy of the build label from the hatch. I got the intake off today and everything looks OK as far as I can tell. I'm not sure where the vacuum leak was coming from but hopefully it will be gone after I put it back together. I noticed the plastic cap for one of the injectors is missing as well as the connector for the MAF so I've got some parts shopping to do. I'm still not sure if I'll be reinstalling the gizmo or not but I've got until next weekend to figure that part out.

worf928

Mike, I cannot make out some of the codes in the picture. What do your eyes tell you?

mcholdfast

Here's what I've figured out so far. I copied this from a previous post from shortly after I bought the car.
===
C32 - ?
XF2 - Leather Instrument Housing
XJ8 - ?
M150 - Without Catalyst
M330 - Radio, Blaupunkt Toronto SQR 46
M400 - Cast Aluminum Wheel, Club Sport (Design 90), 7.5 x16 front, 9 x 16 rear
M482 - Tire Pressure Gauge (RDK)
M570 - Air Conditioner with Improved Efficiency (Rear A/C)
M650 - Electrical Sliding Roof
M935 - Seat Cover, Rear - Draped Leather
M980 - Seat Cover - Draped Leather
I'm not sure what the 5 digit numbers represent but they appear to be 0031(?), 00321, 00341, 09531, 10022, 10081, 10141. Any ideas on these and the ones with ?s above?
===

worf928

According to PET M150 is "operates with leaded gas" which would be consistent with "Without Catalyst"

Nicole might be able to help with the others. I think the 5-digit codes are for 'exclusive' options.

In any case, the M150 code supports my theory that something to do with the air pump and exhaust manifold injection system was changed from S.A.-normal to meet USA regs.

Have you been under the car to see if the air pump 'stuff' looks normal?
Do you have Jim's CDs and the '87 technical supplement from the CDs so as to see a picture of the M150 air injection system?

It looks like the air pump system from pump through the diverter valve is the same for M150 and non-M150. So, I think the eventual solution is to rip out all the 'extra stuff' and make your GT's systems look like the S4's air pump and vacuum system. But, that's only going to work if you've got a 928 cat and don't have the rest of the injection system from M150. (Or, go three-way high flow cats that don't need air injection and remove and cap any remaining m150 stuff in the exhaust manifold that may or may not be there.)

Hilton

My car has the air pump and no cats from factory - hence it is possible to connect up the air pump and vacuum system, although its been disconnected (belt removed) on my car for 10 years (before the PO).

I keep wondering about reconnecting it and getting it working, but unless I'm forced to buy a catalytic converter by the government, don't see any point, so its looooowww on my list of things to do

With non-cat cars, the air pump injects air directly into the manifold, rather than the catalytic converter. Check PET for a diagram of the air injection system for non-cat cars - its all the same except for the injection point IIRC.

Mike - if the car has no cats, then there's not much point in getting the EGR working. Interesting puzzle however, especially with a "Made in USA" part chucked in there

If the car does have cats, then its time to figure out what's missing/wrong according to PET, as the air pump will help clean up emissions.

ColinB

Been trying to keep out of this discussion because my vac system has been interfered with so I don't know for certain what the original configuration was. My car is ROW/RHD and without cats. I can't shed any light on the USA-made device but FWIW my flappy solenoid has 3 ports . The third port has a loose-fitting cap through which, I believe, the vacuum is vented, (ie lost or displaced by atmosphere) when the solenoid closes. Without this vacuum would be trapped in the the flappy actuator so it could not close.

Colin 89GT

mcholdfast

I got everything back together Thursday and it's all good. No more sucking sound from under the intake and the S4 runs better than ever or at least since we've owned it. I reconnected the gizmo back the way it was. I figured I won't fix what ain't broken although I do need to check to be sure the flappy is working as it should.
While I was looking at the air pump on the GT for reference, I noticed that the coupling plate on the front of the AC compressor was coming off. The only thing holding it from falling off completely was one of the AC lines. My AC quit working at the end of the summer and I assumed it was the typical freon leak. I suppose I should have checked for other possible problems. I've got it bolted back on now. I might as well change the oil while the belly pan's off.......