[Thumper3]

Overall - this behavior of having to start the car in order to turn it off with the bypass installed, while it does sound like a PITA, I think it's probably worth it in the end, considering that the car can be started without loading the thrust bearing. I'm sure peplsuk would agree.

Well............this topic has been done to death so didn't want to rehash it here as you seemed interested in HOW this defeat works more than the WHY. But since you brought it up.....

Are you having strange clutch issues? Are you having...

Crank walk due to thrust bearing failure. This is happening to tons of people right now, it is a known issue, I see two people that have posted here this month with symptoms, don't be me, I spend $13,000 having clutches in and out several times and eventually buying a new motor from VW....

www.vwvortex.com

Lots of back and forth in that thread, lots of good information and valid questions many wish to ignore.

I would say to your specific point, unlike the thrust bearing issue it is well documented that the majority of engine damage is done at start up, increasing the number of times the engine is started is increasing that damage. I dunno, doing damage to my engine to avoid doing damage to my engine seems at the very least counterintuitive. And start up damage affects all moving parts in an engine; piston rings, cylinder walls, camshaft, cam follower, all crank bearings. But that's the beauty of it, it's my car and if my oil samples are somehow wrong (currently testing shear strength of a few oils and should have the newest sample back soon), if somehow metal is being removed from my bearings and being beamed out of my oil with no trace, eliminating the very purpose, design, and reason for oil samples, and if by some chance in 7k miles my thrust bearing grenades than I am happy to provide a real data point for the community. Stg 3 car, 68k on the clock with 45k or so on the Stg 3 clutch driven hard and tracked.

Until then, tearing apart my engine with no signs of trouble is like going to the doctor and after having a normal EKG and blood pressure test having him cut me open "just to check".

Regardless, I'll get you photos of the bypass unwrapped tomorrow.

 

[Imua]

I guess that makes sense but I start my car maybe once or twice a day. When driving I may shift 10 or 20 times. Seems like a lot of work for little savings. But heck, when do any of our mods make sense? I always keep the car in neutral whenever at a traffic light to save the thrust bearing. I also skip gears all the time when shifting which also saves wear and tear on the bearing.

^^^ this . . and those shifts are happening at greater bearing velocities than at start-up as well. To each his own, but I have never understood the benefit. Is there really evidence that depressing the clutch to start the engine causing TOB failure or is this just imagined? (EDIT: I see the link in Thumper's post above) I mean, starting your car at all causes the most wear on the engine so perhaps avoid that too?

 

[GTIVRon]

^^^ this . . and those shifts are happening at greater bearing velocities than at start-up as well. To each his own, but I have never understood the benefit.

There is actually oil pressure in the system then preventing metal-to-metal contact. Just because you can't grasp/understand something doesn't mean it's not valid.

Is there really evidence that depressing the clutch to start the engine causing TOB failure or is this just imagined?

No, but it will reduce wear on the thrust washers.

I mean, starting your car at all causes the most wear on the engine so perhaps avoid that too?

... that's just asinine thinking.

 

[Imua]

I didn't say it wasn't valid, did I Ron? I was quite clear in saying I never understood it . . thanks for the education.

. . . and I don't really care if you think my clear attempt at humor is asinine--it is supposed to be

 

[ecirwin]

Maybe some people don't understand what the thrust bearing is and what it does and that it is different than the clutches TOB (throw out bearing)?

The crank shaft has a bearing (just a flat piece of metal, that some would call a bushing) on the end. When you push on the clutch pedal, the force to separate the clutch from the flywheel is transferred through the crankshaft to this bearing. An aftermarket clutch with a higher clamping force that keeps the clutch from slipping on a tuned car with more than stock power/torque, puts more force on the crankshaft and then the bearing.

Before the engine is started, there is little/no oil essentially in all bearing surfaces and definitely no oil pressure. Because this thrust bearing is not designed to carry the load of a stiffer clutch, it is being put under a load that is higher than it was designed to take during startup, which increases the wear.

Once the engine is started and oil pressure is attained, when you push on the clutch pedal the crankshaft is pushing toward the thrust bearing but the oil pressure is keeping any metal/metal contact from occurring. Now there could be some extreme example where the clutch pressure is very high and maybe the area of the bearing is small enough that the force from the clutch would push all the oil out from between the crankshaft and the thrust bearing, but that is a very extreme and highly unlikely scenario.

 

[r53matt]

Well............this topic has been done to death so didn't want to rehash it here as you seemed interested in HOW this defeat works more than the WHY. But since you brought it up.....

Are you having strange clutch issues? Are you having...

Crank walk due to thrust bearing failure. This is happening to tons of people right now, it is a known issue, I see two people that have posted here this month with symptoms, don't be me, I spend $13,000 having clutches in and out several times and eventually buying a new motor from VW....

www.vwvortex.com

Lots of back and forth in that thread, lots of good information and valid questions many wish to ignore.

I would say to your specific point, unlike the thrust bearing issue it is well documented that the majority of engine damage is done at start up, increasing the number of times the engine is started is increasing that damage. I dunno, doing damage to my engine to avoid doing damage to my engine seems at the very least counterintuitive. And start up damage affects all moving parts in an engine; piston rings, cylinder walls, camshaft, cam follower, all crank bearings. But that's the beauty of it, it's my car and if my oil samples are somehow wrong (currently testing shear strength of a few oils and should have the newest sample back soon), if somehow metal is being removed from my bearings and being beamed out of my oil with no trace, eliminating the very purpose, design, and reason for oil samples, and if by some chance in 7k miles my thrust bearing grenades than I am happy to provide a real data point for the community. Stg 3 car, 68k on the clock with 45k or so on the Stg 3 clutch driven hard and tracked.

Until then, tearing apart my engine with no signs of trouble is like going to the doctor and after having a normal EKG and blood pressure test having him cut me open "just to check".

Regardless, I'll get you photos of the bypass unwrapped tomorrow.

Hey Thumper,

Yes, I'm definitely interested in how the bypass works, and I appreciate everyone's thoughts and comments as to the HOW. I'm an engineer, I like knowing the mechanics of how things work (or in this case, the electronics).

Regarding the WHY, I can't say I'm an expert on the thrust bearing failure mechanisms, but I've briefed through other threads, like the one you shared (which I should probably re-read for my own benefit) and can conceivably reason how the thrust bearing failure manifests, as ecirwin has depicted. Whether it'll happen to my engine or not, with my recent clutch upgrade to stage 2, who knows. Quite honestly, I'd just rather not find out. So if I can take a step in the right direction to prolonging the life of my car as much as possible, hell I'll do it, but before doing it, it'd just be nice to know HOW what I'm doing is going to make a difference (or not).

All that being said, I agree, no reason to tear open an engine "just to check," unless its a hobby, you have a spare engine, the time, money, etc., right? Oil sampling and trending results over the life of the car is undoubtedly one of the best things you could do, especially on highly modified engines.

Looking forward to the photos! Thanks again!

 

[Imua]

Maybe some people don't understand what the thrust bearing is and what it does and that it is different than the clutches TOB (throw out bearing)?

Thanks for the patient explanation and speaking for myself, I thought the concern was over the TOB.

 

[Cooper993]

I bought 2 of these by-pass harnesses when there was a group by a while back. I have only installed one, the other one is here on my desk still in the envelope. I have it installed on my R with kessy and the only drawback I have seen so far is that if for some reason I hit the start button to just turn on the ignition I can't turn the ignition back off unless I start the car. Not that big of a deal but it does get annoying sometimes to have to start the car to just shut it back off. It kind of defeats the purpose of installing it. My other R is a base non-kessy car and I don't plan on modding this car past stage 1 because it is my daily driver with no plans to go with a heavy duty clutch. I am thinking I will even remove it from my kessy car as well. So if anyone wants I will sell both of them for $60 plus shipping and pay pal fees or $30 each plus shipping and pay pal fees in the U.S.

I also have Kessy and the bypass switch from the group buy a couple of years ago.

At the time I couldn't turn off the ignition without starting the car.

What I learned, is that you have to double tap the start button at a very specific speed/frequency. It's rather picky. if you do it right, the ignition will shut off.

The issue is if you don't do it often, it's difficult to get the timing right

 

[GTIZRX]

Yea well that is too much messing around. I am just going to remove it and sell it along with the spare one I have.

 

[Thumper3]

Hey Thumper,

All that being said, I agree, no reason to tear open an engine "just to check," unless its a hobby, you have a spare engine, the time, money, etc., right? Oil sampling and trending results over the life of the car is undoubtedly one of the best things you could do, especially on highly modified engines.

Exactly, like I said I have no interest in starting or participating in another flaming thread where things like "Oil samples don't work" are said with a straight face. Everyone is free to make their own decisions about their own cars as I do with mine. I am happy to provide information and facts to those interested in logical conclusions.

Here's the unwrap, let me know if you need something specific on the connectors? Looks like 2 wires (if you number the wires 1-4 starting on the left it is wire #2 and #4) from the side with male pins in the connector (bottom in the photo) are spliced to a single wire on the side with female pins in the connector (upper in the photo)

 

[peplsuk]

OUCH. But very much appreciate your feedback. Were you on a stock clutch? or a stronger aftermarket one?

car details

APR STAGE 2
RSR CLUTCH

 

[r53matt]

Exactly, like I said I have no interest in starting or participating in another flaming thread where things like "Oil samples don't work" are said with a straight face. Everyone is free to make their own decisions about their own cars as I do with mine. I am happy to provide information and facts to those interested in logical conclusions.

Here's the unwrap, let me know if you need something specific on the connectors? Looks like 2 wires (if you number the wires 1-4 starting on the left it is wire #2 and #4) from the side with male pins in the connector (bottom in the photo) are spliced to a single wire on the side with female pins in the connector (upper in the photo)

Thanks again Thumper!

So with this pic, I'm able to tell exactly what's going on now. Originally, I believed one of the ECM signal wires was being jumpered to the +12V DC power supply wire. This is not true according to this picture.

Instead, one of the ECM signal wires is being jumpered to the ground wire.

I made the below drawing to demonstrate what's going on. I used the exact color-coding and connector-pin numbering as can be found in the Erwin diagrams.

So again, normally, voltage is applied across G476 via pins 5 and 1. When a magnet is brought into proximity, the current across the sensor from pin 5 to 1 "bends", resulting in electrons building up on one side (e.g. the left side) of G476. This results in a voltage drop, or "Hall voltage," felt across the left and right side of the sensor. This Hall voltage is sensed by the ECU via pins 2 and 4.

With the bypass harness installed, one of the ECU signal wires is always grounded. Not entirely sure how yet, but this must result in a constant voltage drop across pins 2 and 4 (if my theory about how the ECU senses the Hall voltage in order to determine if clutch is in or out is correct).

If I have in fact depicted the sensor and bypass configuration correctly, can anyone try to explain in better detail how it works?

 

[GTIVRon]

I guess you'd need to know how the hall signal relates to pedal travel. Perhaps rather than "fail safe" the signal is such that if it's missing the car can still be started. Signal high means clutch is not depressed, signal low safe to start. If you ground the signal it shows low potential.

 

[r53matt]

I guess you'd need to know how the hall signal relates to pedal travel. Perhaps rather than "fail safe" the signal is such that if it's missing the car can still be started. Signal high means clutch is not depressed, signal low safe to start. If you ground the signal it shows low potential.

Good point. So perhaps, with clutch pedal out, magnet is in proximity of sensor, causing hall voltage drop, i.e. 1, i.e. signal high. With pedal depressed, magnet moves away from sensor, causing zero hall voltage drop, i.e. 0, i.e. signal low.

As I mentioned in a previous post if/when I find some time, I may test these theories, really try to understand it. But do appreciate the insights regardless!

 

[ftillier]

If you have a multimeter, with the sensor receiving +12V to pin 5, ground to pin 1, measure the voltage at pin 2 and 4. You can also measure resistance between ping 2 and ground, and pin 4 and ground, for the pedal in different positions. It's possible that pin 2 would provide either some positive voltage, vs. just being normally open and closing to ground.

 

[r53matt]

If you have a multimeter, with the sensor receiving +12V to pin 5, ground to pin 1, measure the voltage at pin 2 and 4. You can also measure resistance between ping 2 and ground, and pin 4 and ground, for the pedal in different positions. It's possible that pin 2 would provide either some positive voltage, vs. just being normally open and closing to ground.

Thanks! The only problem with taking measurements at pins 2 and 4 is location. Pin 5 is easy because I know what fuse its coming from and obviously pin 1 is easy because easy access to the battery negative terminal.

Pins 2 and 4 I'd need to remove the battery to even access the G476. In an earlier post, I came up with a way to take readings at 2 & 4 with a spare 5 pin connector I have, only thing keeping me back is motivation.

Thanks again for the feedback!

 

[r53matt]

I guess you'd need to know how the hall signal relates to pedal travel. Perhaps rather than "fail safe" the signal is such that if it's missing the car can still be started. Signal high means clutch is not depressed, signal low safe to start. If you ground the signal it shows low potential.

Good point. So perhaps, with clutch pedal out, magnet is in proximity of sensor, causing hall voltage drop, i.e. 1, i.e. signal high. With pedal depressed, magnet moves away from sensor, causing zero hall voltage drop, i.e. 0, i.e. signal low.

As I mentioned in a previous post if/when I find some time, I may test these theories, really try to understand it. But do appreciate the insights regardless!

Well, come to find out, this may not be entirely true. In the VCDS measuring block for brake and clutch position (066), when the clutch pedal is not pressed, you see a 0, when the clutch pedal is depressed, you see a 1. This doesn't necessarily invalidate the discussion above; however, still need some more confirmation as to exactly how the hall sensor relates to pedal travel. Just thought I'd add this in the discussion for doc purposes.

 

[GTIVRon]

Yeah that 1 and 0 is likely just an internal bit for true/false. Or the schematic has been overly simplified and doesn't show an actual switch being manipulated by the hall sensor.

 

[imabigdipper]

Well, come to find out, this may not be entirely true. In the VCDS measuring block for brake and clutch position (066), when the clutch pedal is not pressed, you see a 0, when the clutch pedal is depressed, you see a 1. This doesn't necessarily invalidate the discussion above; however, still need some more confirmation as to exactly how the hall sensor relates to pedal travel. Just thought I'd add this in the discussion for doc purposes.

I agree with Ron, I'm pretty sure the VCDS values are just a true/false bit representing whether the pedal is pressed (1) or not (0) based on the reading of the sensor. Seems to be more intuitive that way.

However we could be wrong, did you ever get a chance to confirm the voltages?

 

[r53matt]

I agree with Ron, I'm pretty sure the VCDS values are just a true/false bit representing whether the pedal is pressed (1) or not (0) based on the reading of the sensor. Seems to be more intuitive that way.

However we could be wrong, did you ever get a chance to confirm the voltages?

Yep yep, this could very well make sense. Perhaps the hall voltage signal high/signal low is converted in the ECU to a true/false representation to be used for diagnostic purposes, meaning signal high could be converted to a false bit representation, etc.

Have not been able to confirm voltages. Been traveling a lot lately, and still need to fab up the "test" connector to install on the sensor in order to run leads out to the battery, which'll be sitting on the ground, and of course also to the dmm, sitting inside the car, so I can see what happens when I push that pedal.