Originally Posted by dr bob

Late to the discussion --
The vacuum you want to the modulator decreases as the throttle is opened and load increases.

The modulator (and the FPR...) need to see actual intake pressure downstream of both the throttle and the supercharger. Pretty much what the intake valves see. I don't know where the throttle body fits in your Keel installation, but if it's upstream of the kompressor you'll want to move the loa- sensing vacuum connections (FPR and AT modulator) so they see actual engine manifold pressure.
The entire 5-way, which includes the modulator, FPR and dampers get vacuum from the throttle. The system is configured:

Air filter -> MAf -> Throttle -> supercharger -> manifold

I understand having fuel pressure rise with load seems desirable, but I was informed by Andy that the 87+ FPR does not respond to positive pressure. I guess I should check that. Some people add Begi and other FPRs that do. I thought Sharktuning would obviate the need for a rising rate FPR. That's the way I ran my earlier kit. Also, I don't understand why the modulator needs to see manifold pressure. Once the vacuum is gone I think the modulator no longer reduces trans fluid pressure and that's it. What would exposing this vacuum device to positive pressure do? The throttle body vacuum port worked well for the modulator on my previous kit.

The dampers should be plumbed to a port that never exceeds atmospheric pressure; Those connections are only needed to support a leaking diaphragm.
I don't understand the second sentence above. Anyway the diaphragms are intact.

If you've been sharktuning with the FPR reading somewhere other than actual engine intake pressure, you'll want to take a new look at the higher-load cells, as the fuel pressure profile will now more closely follow load.

The vacuum system that used to include the little Venturi was there to maintain vacuum when the engine is under high load, so the vacuum-actuated HVAC, flappy, and cruise control functions can be maintained while full-throttle cruising. The system is plumbed to the brake booster, but that booster can reservoir has a check valve so there is initial vacuum maintained. This gets more important in supercharged and turbocharged cars. There's a far-out chance (same as 'always') that you would want to have full vacuum brake boost available while the engine is at full load, and it was an easy connection to make. Point being that the "load sensing" vacuum system is different from the brake booster and accessory system, and also different from the ported vacuum system that provides distributor vacuum advance based on charge velocity through the throttle body.
Andy included a port that could act as a venturi on an intake adapter just before the supercharger inlet. I never noticed any A/C or brake anomalies.

If this helps: FPR and transmission modulator should be plumbed to the same port where your boost gauge is connected.
Of course, the boost gauge is plumbed to the manifold. So, you think I should move the FPR and modulator there, leaving the dampers on the current throttle body source?

Originally Posted by FredR

Bill,

First of all the whole point of these forums is to work on the premise that many hands make light work- it is somewhat foolish to have issues and not discuss them.

My views on the Bowden cable [ I refer to it as the kick down cable assuming we are talking about the same thing] may not please everyone but as I am concerned the stock method for setting the Bowden cable is somewhat deficient. As I recall the stock setting is such that the cable should be set with the cable one turn slack after the cup aligns with the socket- I set mine about 3 to 4 turns tighter than the WSM procedure. I did this initially to facilitate first gear starts as I found the second gear starts somewhat awful. Nowadays I also run with the kick down bypassed as well. My adjustment criteria is set by what happens when rolling on at about 70mph. Gentle throttle pressure should allow to car to roll on without shifting but anything more than a gentle touch and it changes down instantly. As I am aware this does not change the shift points per se but it makes car feel much more alive.

Needless to say it is one thing ensuring first gear starts with ease every time but that does not mean one has to take off like a bat out of hell every time. As I am concerned if the box cannot handle first gear starts it should not be on the car- common sense being the order of the day. This mod coupled with the PSD system makes driving the thing effortless- just wish it had the 6 speed box in my Cayenne Turbo S [and its power delivery for that matter].

Originally Posted by worf928

What I know about automatic viscous-coupled transmissions in general and the 928’s automatic transaxle specifically might fill a thimble; 90+% of my clients are 5-speed owners.

With that caveat, I have had issues with the kickdown cable. But those issues translated into shifts at the wrong RPM not shift firmness IIRC. I can imagine that there might be a relationship between the two such that a messed up kickdown cable might cause your issue. But, 2mm is not, I think, sufficient mis-adjusment.

Your post helped jog my memory. And also - see above - that I needed to rethink for the kickdown cable.

The “fuel stuff” needs to see the external pressure at the injector. Thus they need to be plumbed after the supercharger as you wrote and not as I posted above.

The lines from the stock 5-way and the 4-way at the booster need to be plumbed differently on a positive displacement SC (like the Keel kit.) Everything but the ”fuel stuff” should get vacuum from between the throttle plate(s) and the supercharger inlet such that they see more-or-less the same vacuum behavior as they would in an N.A. engine (e.g. 17-18 vacuum at idle to ~0 at WOT.)

Originally Posted by Lizard928

I browsed through but not extremely thoroughly.

What is the level of vacuum that the modulator sees with the car at full operating temp idling? I think about 18 inches
I would recommend that you monitor the vacuum level with the car driving (at the transmission with a T fitting). If I continue to experience harsh 1-2 upshifts, I will do that.

I am working on rebuilding a Keel kit that was on an 87 and drove great and then didn't. The intake leaked more boost than it held and through everything out of whack.
The top plate is held to the surround with mostly just sealant. The bolts holding the IC to the top pate were all leaking as were IC pipe connections. The lower plate had some weld ground down and it was completely split left to right and would have leaked really badly.
I've welded the top plate to the surround as well as welded in new injector pieces and am in the process of redoing the IC mounting to ensure everything is as rigid as is needed.
I'm also making it so that the IC can be pulled off without pulling the entire intake off so assembly is MUCH easier.

My point with those comments is that it is likely that you have many vacuum and boost leaks which will vary drastically as you drive.
It is also possible that the seals and valve body in your old transmission had a slightly higher leak past rate which can also affect how the transmission shifts etc.

Originally Posted by Tony

Is the transmission warmed up at all.? Perhaps just some miles and normal heat buildup will put it right if it is stuck?

Originally Posted by Bill Ball

Originally Posted by worf928

If the current plumbing is identical to the old plumbing then surely everything should work now as it did then?

AFAIK the stock fuel stuff doesn’t do anything with positive pressure.

Last, it’s been 12 years (Holy Flying Time Bat Man) since I’ve thought about or touched my TwinScrew for anything other than scheduled stuff. I’d better go refresh my mental picture of its plumbing before commenting further.

Originally Posted by Bill Ball

It might be the air pump diverter valve. The 5 way is: 1. Vac source 2. FPR 3. Rear damper 4. Front damper 5. diverter valve.

Originally Posted by worf928

What Stan and Fred wrote.

So, if the A/P valve is plugged into the 5-way, where’s the transaxle modulator (TM) plumbed? Originally you posted that the TM was in the 5-way?

This S3 throttle body you’re using? Was it modified for the Keel kit? Or is it ‘stock?’

Originally Posted by Bill Ball

Sorry about the mistake in describing my configuration. Hope it is clearer now. The S3 throttle body is stock. Here's a photo of the overall installation.