Audi RS2 timing or belt question

[twoqu]

Without a direct comparsion its all theory on my behalf I am afraid.
Personally I think that the cam pulleys are identical with just the hall sender rotor repositioned. Thats why the mark does not line up. Had they made a dedicated pulley surely they would have made the mark in the correct place to prevent confusion. In fact they could even have got someone to scribe a line on it.
I think the RS2 exhaust cam is a completely different grind taking into account that Porsche also wanted to alter the inlet by the advertised 10 degrees. Rather than grind new inlets they used the cam pulley position to alter the installed position of the inlet in conjunction with the waterpump and the 150 tooth cambelt. Thats why the inlets are the same p/n but differ in the advertised (installed) timing. So its the relative position of the cam pulley that accounts for the installed timing change. If the hall sensor rotor was not then repositioned the ecu would see it in the wrong position. So Audi or Porsche redesigned/repositioned the rotor onto existing cam pulley blanks to save a few Deutschmarks. The cam pulley position altered the installed inlet timing of the otherwise stock inlet and the repositioned hall sensor rotor satisfied the Motronic that the position relative to the firing stroke was correct. The only downside was the incorrect timing mark. Thats my theory but without a direct pulley comparsion its just that - a theory!
All we can say is that that the correct RS2 pulley appears to have the B on the rotor. If you accept my theory it also accounts for the fact that both pulleys have the same part number stamped on them. It is evident that Porsche or Audi raided the parts bins and either used off the shelf Porsche components of uncertain origin, like the injectors, MAF, FPR even the turbo perhaps which I think has exotic origins (968 Turbo?) and on things like the brake discs (and cam pulley/water pump) modified existing parts.
I don't want you to buy unecessary and undoubtedly expensive replacements parts but it does appear the pulley is incorrect. We have established the head is at least the ADU one and the exhaust cam appears to have the right lift. As the inlets cams are all the same, the cambelt has the correct number of teeth and the water pump is correct in terms of its teeth, the only suspect item is the pulley. If we accept that the physical relationship is the same with both pulleys and we know the rotor position is not, we can theorise that that is the issue. If its backed up with an historic hall sensor fault code (00515 I think) then I would argue that not a coincidence. It will only ever be right with all the correct components fitted in the correct position in my opinion. Let see what Vagcom says.

[minim]

Correct me if I'm wrong now as English is not my first language but when they key position is different how can everything be mechanically in the right place? If the key is in a different position won't the cam change it's position to the crank then?

I checked the package tracing of my cable now and It's expected on Tuesday so I will check for hall faults then. However I don't get to delete fault codes, start the engine and then check if the hall fault came back as the car is dissembled now during these checks.

The belt and crank pulley was changed for about 8-9000km ago but I will order new parts if you think it is smart to change belt and crank pulley at the same time as changing the upper sprocket. I just hope the crank sprocket is possible to get trough Audi :X I guess I will know tomorrow when I call my dealer.

Yes I understand the part about the water pump. It all made more sense now that I got to know that the crank sprocket should be about half a tooth off the mark

Thanks for all the superb info guys! This knowledge saved me from hours of research if I ever would have found it out by myself!

[twoqu]

My theory is that mechanically everything is in the right place unless there is a difference in the key position of the two different pullies. We know there is a different rotor position but that is to put it back to the correct position so that the ecu see it when it expects to.
Might be worthwhile to wait for the cable and see if there are any hall sender fault codes stored. If there is I think that adds weight to our incorrect pulley theory.
If it was my vehicle I would replace the camshaft belt and the crank pulley if changing the pulley. You might even consider using a stronger version of the crank pulley that are available as that also is a known weak spot. There is no danger in it being out if you are using all the correct components. It just looks from the pictures that the pulley is incorrect and this may be confusing the ecu hence the performance is degraded.
By the way I hope you understood what I meant about the water pump. It looks as though the exchange version uses the TDi casting. Presumably there are no original casting left to exchange.

[minim]

Oh I just contacted the previous owner and asked him about the problem on WOT. He said that this was something that came now recently (this summer) just after the fuel pump was replaced on the car. He didn't think it was related to the sprocket as the rebuild was done in 2011 and the car was working fine until recently this summer. This makes me even more scared of changing to the original sprocket with a 10 degrees change in case I put something out 10 degrees.

[minim]

That makes sense So there is nothing wrong I can do with getting the original sprocket from RS2 and putting it on? They can't have done any crazy mods so that this sprocket fits and runs like it should so that by mounting a original one I will get things 10 degrees off again and ruin valves or something like that?

[twoqu]

Yes but effectively the engine ecu is expecting the rotor to be in the correct position which it will not be. It is claimed that the hall sensor has no function other than to determine the firing stroke for starting. When the RS2 is timed incorrectly, that is to say all the marks are aligned this is usually accompanied by a hall sensor fault even when there is no issue with the hall sensor itself but the position of the rotor. It usually results in boost problems as well.
I guess it was damaged during the cambelt replacement and the incorrect replacement used. Unfortunately whithout having seing them side by side is difficult to be certain. The only thing we can say is that there are two versions and you appear not to have the RS2 one. If it wasn't necessary Audi would not have done it.

[minim]

The cylinderhead was marked with ADU stamped in the front where you described it. I didn't look for a part number after I saw the ADU stamp tho.

I did the measurement you described and It looks like it's the correct cam installed for the ADU engine.

I don't know if it's the wrong rotor but it sure looks like it since the "B" is missing. If I'm able to locate one I will take measurements and a lot of pictures to compare. I'm really not sure if I should just do the swap tho in case I put something 10 degrees out again since the engine is indeed running now it's just lacking power with WOT after turbo pressure kicks in. This could be a lot of other things like coils/air measure and so on also.

[twoqu]

It might depend on how much damage was done when the belt went. If the engine was running its may have damaged valves/combustion chamber etc. If the pulley key was snapped during a cambelt change then perhaps nothing was damaged. The only issue would have been the lack of a readily available RS2 cam pulley hence perhaps why they may have used the easier to obtain AAN/ABY one.
Does the cylinderhead have its correct ADU part number on it? Its stamped on the front of the cylinder head on the left looking from the front? If not then the head itself has been replaced. A rough estimate of the valve lift would be to attempt to measure the total height of the lobe and then subtract the measurement from the basecircle (basically the round bit not the lobe). The lobe has a taper so its not as easy as its sounds. If its nearer one than the other that may help in identifying it. Can use a dial caliper to get that measurement perhaps.
I am not certain whether the RS2 cam pulley has its key in a different position to the AAN/ABY pulley or whether the installed physical position is in effect the quoted difference in cam timing. It would appear the timing rotor position is adjusted to put the relationship back in the correct orientation for the hall sensor. If it is indeed the wrong pulley and you will be replacing it with the correct one it would be a good opportunity to compare the two and post the relevant positions. From memory I believe the rotor wheel is in a different position and the actual slot is a different size.

[minim]

Ok then I've done some measuring on the exhaust cam. It was not accurate with the tool I've used (Vernier caliper) and I did the measurement with the cam inside the car but since the difference on lift is 0.9mm I think it should be accurate enough to see that it was the right cam. I measured the full lobe height to be 47,55mm and the base circle to be 38,10mm. This should give a lift of 9,45mm and is very close to 9.5mm that it should be (not that exact measure with a oldschool vernier caliper..).

It's just the sprocket that needs to be changed then? But one question, should the car run this fine with 10 degrees wrong on the sprocket? I mean I can get a quick acceleration on 1st gear and on the 2. gear i notice some halting/loss of power on the engine when getting turbo boost but if I increase the throttle slowly I can mange to get it running fine up to the red mark.

[minim]

Thanks. That was not so good Hobby mechanics here so got no clue how to measure the lobes properly..

However the intake cams on AAN/ABY/ADU are the same with just the sprockets with 10 degrees offset in difference so I would just have to measure the lift on the exhaust camshaft to see if it is 8.6 or 9.5mm lift on it. This should not be to hard to do with the cams still mounted in the vehicle should it?

[UrS4boy]

On a side note, that little black thing with "08 02" marked on it, at the "5 o'clock" position in your photo, is the G40 Hall Effects Cam Position sensor. It appears to be touching the shutter wheel. Not a good thing. There needs to be some clearance between the shutter wheel and the cam sensor.

More G40 Hall Effects Cam Position Sensor info here:

http://forums.quattroworld.com/s4s6/msgs/22580.phtml

This photo shows proper clearance between the sensor and the shutter wheel:

[UrS4boy]

My cam sprocket def. doesn't have this B marked in. I was just outside looking for it on the car and here is the picture. Is there any way to check that I don't have the wrong cam/top also? The whole top was rebuilt due to a failure of the belt back in 2011 so I fear that they might have used some wrong parts now that I see this.

Definitely NOT an ADU exhaust cam sprocket. So that is an issue right there. Unfortunately, figuring out what the exhaust cam is will be a bit of work because Audi did not fully stamp/cast the PN into the cam casting so you will have to figure out how to measure the lift and duration and compare it to an AAN/ABY exhaust cam.

AAN, ABY, 3B PN 034109022D
Opens 42° BBDC, closes 9° BTDC, duration 213°, lift 8.6mm

ADU PN 034109022G (originally 034109022F, but the G replaced it Sept 30/97)
Opens 24° BBDC, closes 1° ATDC, duration 205°, lift 9.5mm

More camshaft info here:

http://forums.quattroworld.com/s4s6/msgs/87524.phtml

[minim]

My cam sprocket def. doesn't have this B marked in. I was just outside looking for it on the car and here is the picture. Is there any way to check that I don't have the wrong cam/top also? The whole top was rebuilt due to a failure of the belt back in 2011 so I fear that they might have used some wrong parts now that I see this.

[UrS4boy]

To follow up on Twoqu's (Robin's) comment, the ADU exhaust cam lobe timing is 10 degrees different than the AAN and ABY. To compensate for this, on the ADU exhaust cam sprocket, its G40 Hall sender shutter wheel is rotated 10 degs in the opposite direction than the cam lobes were rotated. As a result, the ADU exhaust cam sprocket has the letter "B" stamped on the shutter wheel to distinquish it from the AAN and ABY exhaust cam sprockets. The shutter wheel is not a seperate item.

ADU exhaust cam sprocket:

[minim]

I don't know yet but I will look into that. I've ordered a ODB2->ODB1 plug for my ross tech cable and expecting that to be delivered in a few days. If that is changed won't the exhaust cam be a bit off since it doesn't have the same offset as on AAN/ABY engines? I know that the previous owner had the top rebuilt a few years ago but I didn't check what parts they changed (might show in the receipts).

I took a picture using the mark on the flywheel also but I had struggles lining it up correct using that mark. In a guide i found on the s2central it said that I should put the mark slightly behind the edge of the housing and then nothing matched up in the front but now that I see that the crank should be a half tooth out it's not so bad. Should I open the sparkplug on the most front cylinder just to check that it's on TDC with a rubber hose or something or is this "safe as the bank" method to use the marks?