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928 tiptronic?

 
Old 11-30-2001, 09:18 AM
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Art_Z
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Post 928 tiptronic?

Was it ever offered in the 928? I think it was in the 911 in early 90s. Just curious.
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Old 11-30-2001, 11:18 AM
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Ed Ruiz
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No. However, the AT can be made to behave like a Tiptronic. Read the owner's manual for the details.
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Old 11-30-2001, 03:42 PM
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You can probably make the 928s auto act like a tip. And remember, the tiptronic is a standerd automatic. Their is nothing special about it.
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Old 12-01-2001, 05:14 AM
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Nicole
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If you frequently hand shift your 928 automatic, you might want to check out the shift handles from Jager Engineering at http://www.jageng.com/auto_1.htm. This is probably the closest you can get to a tiptronic...
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Old 12-02-2001, 06:04 PM
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Steve Cattaneo
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Tiptronic, is an electronically controlled five speed AUTOMATIC TRANSMISSION, with a lockup torque converter. There are two shift programs, a dynamic shift programs, in this shift gate the transmission will upshift and downshift automatically. Just like the A22/A28 928 transmissions.

In the manual shift program {called one touch control, it’s an option model dependent] the transmission holds the gear sclected, the transmission can be shift to a lower or higher gear. No automatic up shift will occur in this mode. Will not fit a 928 would be a great upgrade.


Steve C
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Old 12-03-2001, 12:22 AM
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John Struthers
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Steve,
I defer, humbly, to your expertise RE: the tiptronic manual/one touch/gear hold program.
Pattycakes (3spd) will hold in 2nd, as far as I can determine, well into the mid/high 80mph range without overriding and shifting to 3rd -got to love that torque/HP curve-.
What I am wondering is; what's the difference between my 3spd and the tiptronic other than it won't (easily, if ever) hook up to the 928 drivetrain, it's a 5spd, electronically controlled. In spirit the 3spd
does the same thing ,albiet manually, that the Tip does in either the dynamic or lock-up
mode. Three other ?'s on the trans. topic.
I know you have answered this before, but does the 4spd auto. act the same as my 3spd?
Other than the obvious gear ratio changes, differences does the brain really need to be changed to a latter year/model? And if the change is required will that cause problems when the late model brain tries to manage a
4.5L engine? Yeah, I know, the effort/cost would be so high that the purchase of a 86 1/2, or later would be a better deal. I am curious though. You wouldn't know if the early Euro's (300HP)had any mods to their auto's I notice there is a .03,.05,.08 series to the G28 trans. there is no .04,.06, .07 thru the 85S models. There is a similar gap in the later years.
The .11's were mated up to the M28.43 and the .41 engines were mated to the .13's.
The .12 was mated to the M28.42/47 engines. Most of the 928 engine and transmission mod numbers are out of synch as the years marched on, do you know of the reason why?
Finally, how does one I.D. the manual and auto by trans numbers?
Thanks for ANY help on this .
Keep em' rolling.
John S. & Pattycakes
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Old 12-03-2001, 02:13 AM
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John,

I have no idea on why the numbering is what it is (but now that you have mentioned it, I'll perhaps try to understand the logic.)

As to the whole Tiptronic thing, one could modify the existing 4sp a/t to behave in much the same way as a Tip. As Steve pointed out the real Tip is electronically controlled. From an engineering standpoint it would be a major PITA and require a couple of blank checks. And don't even look at your statement the month they get cashed x(). No return on investment that I can see.

What could be done with relative ease (from an engineering standpoint, anyway) is to eliminate the auto functionality of the box, and make it fully manually controlled. That is, you - the driver - select the gears at ALL times. You want an upshift/downshift, it's up to you to pull the lever.

You still have no clutch to modulate, and you get the full power shifting/launch advantages of an a/t tc combo with the direct gear selection of a manual trans. (Yes, there are still the parasitic losses of the a/t as well.) There are several minor issues that also must be engineered (new shift gate, or a faux-Tip ratcheted mechanism) but it is just a matter of finding the time to do it. The only thing keeping me from the project is simply finding the time to spend on it. (I just don't have the encyclopedic knowledge that Steve does about MB valve body passages.)

Greg
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Old 12-03-2001, 11:00 PM
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John,

The Tip In the one touch mode will hold every gear (1-5) up shift and down shift with out exceeding the maximum engine speed. There are speed limits for each gear. Almost like the speed rely or tach. input on the 928’s, remember that topic. How it differs from a three speed. Two extra gears plus lock up torque converter, also has an adaptive memory feature. Just by the speed of accelerator pedal movement shift points are modified for, economical, average, and high performance driving style. The A-22/A-28 is hydraulically controlled. No brain ( is used). The three speed and the four-speed act the same except for one less gear and the four speed shift points are higher.

A quick overview on the trans ID:

A-22/01/12/168/0019, A-22= auto. Trans., G-28= five speed, 01= rest of the world and USA models 1980, 02= USA models 1978 and 79’, 12= 40% dif., 1= V8 engine version, 6= Trans. type, 6= auto, 1= five speed, 8 = model year 1978, 0019- serial number= modification- for example a unit may have had a lube system update after serial number 123456. So all units with a lower serial number would not have the update.

I’ll work on something more in depth for both models A-28’s and A-22’s.

Greg, I’ll have some information for you tomorrow, it’s 10 o’clock eastern standard time and my wife is telling me it’s time to go to bed.

Steve C., The Great White

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Old 12-04-2001, 09:01 PM
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Greg,

I drive me 928 manually all the time I love the torque and acceleration. It definitely has more torque than the automatic up shifts, converting the four-speed to a manual shift transmission is a plus.

Governor pressure is the road signal for up and down shifts. It moves the command valves (shift valves). By disabling the governor, the road signal is lost. The trans will not up shift, but the only problem is you just can’t remove the governor, it’s part of the working pressure (main line pressure) and governor pressure circuit. The trans will slip if you do. It has to be fooled. you have to make the governor think it’s not moving. The governor valve has to be blocked. Once that is done, you should have a manual shift auto trans. Not a tip, but the next best thing.

The existing shifter mechanism is not suitable for manual shifting. First it has no neutral safety lock out. If your in the D position, you can push the handle to neutral (not good for power shifting at 5000 rpm’s). Once you disable the governor you lose the hydraulic lock out shifts to reverse and park from all forward rangers. While the car is moving governor oil activates a lock out piston in the valve body, which prevents the shifter from being moved to reverse and park position from all forward gears while the car is moving.

The tip shifter cannot be used. The one touch control is electronic. The only other shifter suitable is B&M or Hurst automatic shifter. Let me know what you think, in the mean time I’m going to modify a governor and see how it works.

Steve C, The Great White
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Old 12-05-2001, 03:52 PM
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Steve,

Modifying the governor is definately a relatively easy way to go - are you just going to shave the weights, or is there as swap out with a different MB product?

I was actually thinking of doing the whole deal - making custom valve body for full manual control and set up a custom ratcheted shifter that allows 1-4 sequential shifting in a gate off the main. Or just set it up as electro-mechanical control - up/down paddles on the wheel, controlling a stepper motor or a couple of solenoids at the trans to do the rod actuation.

This may prove to be more annoying than just hunting and killing a new 7-series BMW to get hold of it's ZF 6-speed auto box.

Thanks as always for the info Steve. I have been doing my reading (and I took apart an a/t the other day) so I have a general idea of how working vs line vs modulating and such relates on this box. What would be really helpful to me now is a good reference for the shift valve assembly - I do have the factory power flow diagrams which are helpful, but it would be much easier if I had a full schematic of the valve body. Like a wiring diagram - which passage is which, which spring is which rate, etc.

Let me know how the gov mod goes, sounds like it could be rewarding.

Greg
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Old 12-05-2001, 03:53 PM
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Steve,

Modifying the governor is definately a relatively easy way to go - are you just going to shave the weights, or is there as swap out with a different MB product?

I was actually thinking of doing the whole deal - making custom valve body for full manual control and set up a custom ratcheted shifter that allows 1-4 sequential shifting in a gate off the main. Or just set it up as electro-mechanical control - up/down paddles on the wheel, controlling a stepper motor or a couple of solenoids at the trans to do the rod actuation.

This may prove to be more annoying than just hunting and killing a new 7-series BMW to get hold of it's ZF 6-speed auto box.

Thanks as always for the info Steve. I have been doing my reading (and I took apart an a/t the other day) so I have a general idea of how working vs line vs modulating and such relates on this box. What would be really helpful to me now is a good reference for the shift valve assembly - I do have the factory power flow diagrams which are helpful, but it would be much easier if I had a full schematic of the valve body. Like a wiring diagram - which passage is which, which spring is which rate, etc.

Let me know how the gov mod goes, sounds like it could be rewarding.

Greg
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Old 12-05-2001, 05:17 PM
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Tabor
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Originally posted by steve cattaneo:
<STRONG>Tiptronic, is an electronically controlled five speed AUTOMATIC TRANSMISSION, with a lockup torque converter.</STRONG>
Both the 964 and 968 came with a 4-speed tiptronic.
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