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Changing of the distance sensor does not require draining of the clutch fluid. Even if it did, PIWIS oil fill mode or equivalent isn't required for the refill unless you remove the valve body for some reason doing other work. I'm not sure where the 'not recommended' comes from that is mentioned above with regard to this, but people have been now draining and filling clutch fluid since 2019 using the method I described without oil fill mode and the feedback has been 100% positive. Not a single person has come back and said 'that didn't work for me'. Maybe it's the workshops who want to continue the racket who are saying it's 'not recommended'. Or they just don't understand what is going on in the transmission. Having spoken to a few workshops, they have little clue how the transmission actually works. They 'follow the recipe' set out in the workshop manual with little knowledge of why the steps are there and if required or not. There is no motivation to change because they make a bunch of money from it and no-one is waving the BS flag at them.
For the 911 transmission only, the clutch fluid cooler and associated metal pipes need to be disconnected for rear casing removal. There are two non return valves (in and out) for the cooler inside the valve body that hold the fluid inside the transmission and associated oil paths and seem to be deliberately put there for this purpose. If you have seen my video on the valve body, these are the two big red spring loaded valves that can be seen when you split open the VB. When the clutch oil cooler is removed, a small amount of fluid will be drained from the cooler after it's removed. After installation, when you start the engine, the oil is immediately pumped though the cooler and the lubrication gallery to fill these with no intervention required. You will need a small top up of fluid for the amount drained from the cooler. Note that oil fill mode does nothing with the cooler (other than closing the coolant flow) or lube gallery. It's there to fill the shift actuators and clutch pistons, which haven't been drained.
My thoughts on leaving the 911 transmission in the car for the rear casing removal and distance sensor are as follows. If there was a 911 owner who had done work on this and might be able to answer the questions it would be appreciated.
- You should be able to easily lower the transmission sufficiently to remove both oil coolers.
- Lowering sufficiently and safely to remove the casing is my big concern.
- Can the transmission be lowered enough for the rear casing can be removed without the front face of the engine touching the engine bay wall or stressing coolant/fuel/other pipes and hoses?
- If able to be lowered enough, is it safe? What is the best way to support it? The engine/transmission assembly is about a 350kg pendulum swinging from the engine mounts at the rear. The more it's lowered, the more it wants to swing to the rear and gets dangerous because the supports under the transmission/engine aren't just pushing up, but also need to push forward. Anything more than about a 10 deg angle change I think would get a bit nasty.
Good comments @jjrichar though I would like to hear from @LynxStarAuto why he doesn't recommend the no-PIWIS procedure. As I mentioned above I changed my fluid using your procedure, then ran the PIWIS fill procedure afterwards. The level was exactly the same, no difference at all.
It is good to know other units are out there that support a PDK calibration other than a PIWIS. I had heard this before but had not seen the list.
One thing I've heard people say is that it's too risky to not follow any factory procedure on the PDK as if anything goes wrong it's $25k for a new PDK. Well, we've blown up that myth so hopefully we don't hear that anymore. People also say "the Porsche engineers must have had a good reason for saying to do it this way" which assumes the Porsche engineers are actually writing the service manuals. Much of what Porsche recommends or calls out doesn't seem to have a good rationale other to inflate service costs IMO. If you need a PIWIS to replace the fluid then that (at least used to) require a trip to the dealer along with inflated labor and material rates. I could see why Porsche bean counters would claim it's needed when it really isn't.
We share the same goal of making PDK work as simple and inexpensive as possible. Like I said, it's not to cut corners but to eliminate stuff that really is not needed and keep costs at a reasonable price. IMO, there is no reason to remove a PDK from a Boxster/Cayman for a distance sensor repair yet some shops insist on it. Why is that? I've not heard a good explanation.
Good comments on the cooling lines, plus there are some differences between the 9x7 and 9x1's that could require a little thought once in there. But I agree that a fill procedure should not be needed as the pump is running whenever the engine is on and it will push fluid through. The fill procedure simply exercises the solenoids so fluid is pumped through various paths as far as I can tell, it doesn't prime the pump or anything like that. Even if a small amount of air is in there it should be forced through the system once the transmission is operating.
Yeah, the service writer just another commissioned salesman. Every time I go to my local dealer I feel like I'm getting nickel'd and dimed except its not nickels and dimes. Like offering a service to check and remove leaves and debris from the radiators for $250. Yeah, no thanks, I already did that. Why wouldn't they do that anyways during the $400 oil change? They have one job when it comes down to it, separate you from your money. They're part of the same system that benefits when you need a $20,000 transmission. They have no incentive to be cost conscious for their customers. I think the funniest part of this whole venture is that their greed and hubris is what will now cost them market share. Just think, if they would have kept the price of a PDK around $10k, while still expensive, as an OEM transmission, probably would have kept this entire project from ever happening.
I'd like to remind or point out that if the cost of this sensor gets to 100 bucks plus or minus. Is it really that bothersome, having saved 24900 dollars on a new pdk or some other percentage vs other aftermarket sensors, to not just go ahead and purchase a Chinese PIWIS? You gain an additional tool in your tool box. Fill procedure or not, having a PIWIS is pretty handy. In my opinion.
Update:
I received the sensor from PV in the mail yesterday afternoon.
Spent today testing and installing. The results, nearly a 100% pass, I'd call it 90%. There was much educated speculation on our part about lots of things and it was really nice to find it was as predicted. The only part that didn't work exactly right was the sensitivity of the sensor. It's a little too sensitive, giving a greater distance than is desirable when a gear is selected.
I did a cal and it passed first time no issues. I then put into rolling test mode and ran through all the forward gears without issue. It doesn't like reverse though. I suspect the distance the TCU is being sent is too much and it says no. I can hear it doing something, but the distance moved stays at zero, making me think it's trying to select, gets the long indication and then puts it back to a neutral position.
I've taken some video footage and also learned a few more things about making the distance sensor replacement easier. When I find some time I'll get it out.
To be honest, for our first prototype we are super happy with the results. The sensitivity was something we knew was going to be a long shot to get right on the first go.
I take my hat off to PV. We have a few fellas in the group working on the project, but PV is the real smarts and driving force behind making this a reality. Cracking job my friend.
I may have missed it and as this thread is in the 997 Forum area can we add a post that profiles what cars/PDK's that this module will be appropriate for? Car's only or does this part get used in the Macan PDK for example?
Thanks guys, and thanks to @jjrichar for doing the heavy lifting on test.
As mentioned it seems to be a little too sensitive on channel 4 which is used for reverse. Channel 4 is the one where the magnet runs in front of the DS, the others run behind it. So its geometry is a little different than the others and it needs some fine-tuning.
The distance sensor puts out a PWM signal between 12-88% in normal operation, likely closer to 20-80% in most cases. If the DS output exceeds this range we think the TCU interprets that as a fault. So in this case the DS is set too sensitive and is probably sending out something like 92% for Reverse and that's what the TCU is flagging.
The good news is that this is simple to change as all it requires is a reduction in the programmable gain of the sensor. But as @jjrichar mentioned it's pretty darn good for a first crack as it was done on theory, with no trial and error yet. Despite this, 7 of 8 gears worked without issue so we got it awfully close. Plus we collected a wealth of test info we can use to adjust all four channels (if needed) to ensure we never inadvertently exceed the range and generate faults.
One thing I do want to mention is that it passed calibration on the first attempt without issue. Those who have followed this over in the PDK repair thread know there have been some issues with cal after DS replacement, often requiring it to be done multiple times before success. We think we figured out the cause of this and fixed it in the sensor design but time will tell.
Regarding Westcoast's question this only applies to Boxters, Caymans, and 911's with a PDK from 2009-2016. Other cars use a different distance sensor. It's not clear to me how it applies to 2017+ MY cars with the 8-speed PDK.
Last edited by PV997; 01-19-2023 at 04:09 PM.
Reason: typos
Good comments @jjrichar though I would like to hear from @LynxStarAuto why he doesn't recommend the no-PIWIS procedure. As I mentioned above I changed my fluid using your procedure, then ran the PIWIS fill procedure afterwards. The level was exactly the same, no difference at all.
It is good to know other units are out there that support a PDK calibration other than a PIWIS. I had heard this before but had not seen the list.
One thing I've heard people say is that it's too risky to not follow any factory procedure on the PDK as if anything goes wrong it's $25k for a new PDK. Well, we've blown up that myth so hopefully we don't hear that anymore. People also say "the Porsche engineers must have had a good reason for saying to do it this way" which assumes the Porsche engineers are actually writing the service manuals. Much of what Porsche recommends or calls out doesn't seem to have a good rationale other to inflate service costs IMO. If you need a PIWIS to replace the fluid then that (at least used to) require a trip to the dealer along with inflated labor and material rates. I could see why Porsche bean counters would claim it's needed when it really isn't.
We share the same goal of making PDK work as simple and inexpensive as possible. Like I said, it's not to cut corners but to eliminate stuff that really is not needed and keep costs at a reasonable price. IMO, there is no reason to remove a PDK from a Boxster/Cayman for a distance sensor repair yet some shops insist on it. Why is that? I've not heard a good explanation.
Good comments on the cooling lines, plus there are some differences between the 9x7 and 9x1's that could require a little thought once in there. But I agree that a fill procedure should not be needed as the pump is running whenever the engine is on and it will push fluid through. The fill procedure simply exercises the solenoids so fluid is pumped through various paths as far as I can tell, it doesn't prime the pump or anything like that. Even if a small amount of air is in there it should be forced through the system once the transmission is operating.
Hey guys, so you have to remember that my predicament is slightly different than a DIY. As an independent, I have a certain obligation and commitment to the customer. As such, the bare minimum is never in the best interests of the customer or the repair. I have the responsibility of helping the customer make an informed decision, and not leading them astray. As such, I WILL ALWAYS drop the pan on a unit before I do any internal work. Just to see if it is even worth it for the customer and if I want to take the calculated risk for my business. There are other issues that spring up with these units, not just the distance sensors. Mechatronics (valvebody) issues are also very common. From the solenoids, to the internal harness, to the valvebody itself. The oil pan is the crappy ZF favorite plastic pan with integrated filter, and disposable alloy bolts. Those have a service life and I like to cover all the angles, because the last thing I want is for the car to boomerang and the customer to have spent all that money in vain.
The other detail is that my experience as an indy is also different as I am usually the last resort after the car has been through hell and back, and the customer acquiesced and finally brings it in. By then I just can’t really trust anything anymore. I need to do my due diligence. I’ve seen so many crazy things in my years, you learn to doubt everything. How do I know the current fill in the vehicle is correct? How do I know another shop wasn’t already in there and messed with stuff? The fill procedure saves time, and gives me peace of mind as it’s the most thorough way to fill the unit since there is no traditional dipstick to base off of.
This isn’t my first time swapping one of these sensors, but it is my first time using the T design sensor. Usually the aftermarket approach is to go with a used sensor, and dump the car.
I put myself in the shoes of the customer. I just made them spend 2 grand on a part, you think I’m not going to drop the pan and mechatronics and make sure there are no other underlining issues with the vehicle? This is a 14, 991 with 67k. I just don’t operate that way. There is a reason I went independent. The franchise “guess and see” approach was not for me. I’m always going to go the route of maximum possible within the confines of the budget to get the best quality repair possible. It’s just a win win scenario for both parties.
There is also a couple of upgrades I like to do that I have experience with on personal vehicles I’ve used for testing purposes. One is converting to an aluminum pan with separate serviceable filter. The factory plastic combo pans suck. They tend to develop leaks, and also develop fissures and debris that just gets pumped all through the unit. There is an aftermarket aluminum pan, that uses a serviceable filter. Saves money in the long run, and I have yet to experience any negatives with it:
So that’s going to get done to this vehicle as well. In regards to the oil control valves, I haven’t really paid too much attention to their setup on these units, but I can tell you from previous experiences as a VW tech they are there to prevent bleed down back into the oil pan. On the transverse style units found on a plethora of VW cars (DQ200xxx) the oil cooler is mounted up top. On early models, after shutdown, the oil would drain from the cooler back down into the sump. Essentially emptying the feed to the pump causing cavitation of the fluid. This would cause cold start symptoms, and led to premature failure of the pumps. Later generations saw an oil control valve put in place to prevent that from happening. Same thing is done on the oil solenoids which feed VVT phasers on timing chains.
Anyway, here is the specimen which will see the T designs sensor:
Very valid perspective. When something goes wrong, you have to be able to defend your actions and judgement by telling the customer that you went by the book. Some customers will be savvy enough to understand and approve deviations -- and responsible enough to deal with any consequences, real or imagined -- but I imagine the majority aren't.
Thanks @LynxStarAuto and I get it. It's really easy to fall into the penny-wise pound foolish trap. The goal here is not to squeeze every last nickel out of the cost and a lot of what we throw out is just spitballing in hopes that knowledgeable people like yourself will chime in. That's how we all learn.
All that being said, the aftermarket parts are around $2k and I know for a fact they are about $100 in material and maybe two hours labor. On any other normal car it would be a $500 part.
Plus what's the reasonable labor to replace one of these things? Like I said we saw 28 hours quoted and that sounds crazy, maybe ten hours sounds about right to me. There's no book time on this so do shops just get to make it up? I know there's a lot of overhead in running a shop but that gets rolled into the burdened labor rate. Shops don't get to pad the hours on top of it.
You seem like a straight-shooter and I really appreciate your willingness to engage. None of us think it's fair to compare DIY to the costs of an honest shop. What we are poking at is why some people seem to be getting quoted really high hours and why the damn part is so expensive. Seems like the prices are being set compared to a PDK replacement rather than the actual cost plus a reasonable profit. That's what we want to change.
They claim the MSRP is $25,000 and that their price of only $2199 is 91% off.
This is pure, unadulterated BS. When you read the fine print, they are comparing the cost of their DS to a brand, new PDK and that's why they claim their sensor's MSRP is $25k. Maybe there are some people stupid enough to fall for this but I hope not. Again, this is a $500 part tops that costs maybe $250 - $300 to make in recurring material and labor costs. Not only are they gouging people, they are claiming it's somehow an unbelievable deal. Like I've said before, you can pee on my shoes but don't tell me it's raining.
You see enough of this stuff and it makes me skeptical of every claim when it comes to Porsches. We probably go overboard in the criticism but that's only because that's only because it's a target-rich environment.
@PV997 I think that you have hit the nail on the head, but it is not surprising that those first to market with these replacement sensors are trying to cash in, not saying it is right but until competition forces them to adjust pricing, they will take the order and smile!
Your efforts and @jjrichar are very much appreciated by those of us interested, don't get dragged down by the capitalist aspect of marketing, TBH I kind of laughed and thought it was a poorly attempted joke by Xemodex.
Thanks @Westcoast but my ranting and raving isn't going to fix the problem so I need to stay focused.
As @jjrichar noted above we had pretty decent results from the prototype sensor with calibration working on the first shot and seven gears working (all but reverse). In later tests we had third go a bit wonky on us but that wasn't too surprising as we kind of expected it. We knew that reverse was reading too high of a duty factor (~92%) and that caused to the TCU to fault. Well, third was the next highest and it was right on the cusp at around 88%. A little noise in the system and it bounced over the threshold and also faulted. It came back but later faulted again.
So we learned two important things: 1) the gain on the sensor was set too high so our duty factors were reading higher than they should have, and 2) the TCU will fault if the duty factor exceeds around 90%. I suspect it will also fault if it goes beneath 10% but we didn't have one of those. The TCU wants to see a range around 22-78% duty factor when things are working normally. Since I had programmed the sensor with a little too much gain instead of reading 78% it was reading 88-90% on two channels. This is very easily fixed with a programming update.
We also found that the sensor was much more sensitive to magnet height than we would have liked and that it did see some influence from the adjacent magnet. This didn't seem to be a problem as the gears worked just fine (aside from what I mentioned above) but we didn't like it. We traced both of these issues to the orientation of the Hall Effect sensors. Magnetic lines of flux curve and the shape of that curve is driven by the magnet dimensions. Hall Effect sensors are most sensitive when the lines of flux are perpendicular to the sensor surface.
Here's a pretty good simulation of the PDK magnet (10 mm radius by 6 mm length) with the flux direction shown, we need our sensor face to be perpendicular to those lines. If the angle is off it reduces the signal as a sine function (@jjrichar first realized this).
By orienting the sensor at a 70 degree tilt, we maximized flux from the desired magnet over its travel range while happily nulling flux from the adjacent magnet due to the housing geometry. It took a little trial and error as the orientation wasn't intuitive at first but made sense after some simulations. It's not perfect but it significantly improved both issues and will be incorporated into prototype #2.
Thanks also @stjoh who has a 997.2 PDK and pulled the case on it today and sent us some great photos. He's also confirming some key dimensions and will be doing a fit check for us soon. The 997/991 PDK is flipped side to side when compared to the 987/981 PDK and the distance sensor has to be flipped 180 degrees. All we've had so far is a 981 version so his info has been very helpful.
01-17-2023, 07:14 PM
