Audi RS2 timing or belt question

[minim]

I've recently bought myself a Audi RS2 that has a problem with not going clean after I get turbo boost (3500-4000 revs and up) and I'm not sure if this is related but while looking for a oil leak I took the front off and did a check of the timing belt and I think it looks odd. I'm not sure if this is related to the issue of the engine not running good while under boost but I just wanted to check this before putting things back together. The owner did not say that this problem with the engine came after the cam belt change he did 8-9000km ago but he said it came recently but I always have a hard time to belive in all stories used car sellers has

Here are some pictures of how it looks like now.



And some thoughts that I've made myself.. The water pump that is on the vehicle now is a 26tooth 074 121 019C and not the original part number that should be mounted. According to a manual I found on S2central it says that the original coolant pump has 29teeth but on this forum I've found info about it beeing 26teeth and the regular S2 has a 29 teeth. If I had a 29teeth water pump I guess the cam would be closer to the mark since it is bigger and then the tensioner could be slackened off a bit. There is also some saying that the cam is mounted one tooth off from Audi factory but this I haven't been able to confirm.



My toothed belt has 150 teeth but I'm not able to get out the part number on it anymore as It was changed about 8-9000km ago.

[UrS4boy]

Your second photo looks close, if not spot on, for an RS2 with proper RS2 water pump and cam belt.

The RS2 ADU cam to crank timing is slightly different than the AAN and ABY timing because the RS2 uses a 26 tooth water pump instead of a 29 tooth water pump. THe RS2 timing belt has 150 teeth, not 151 like the AAN and ABY:

Timing belt info (with PNs)

http://forums.quattroworld.com/s4s6/msgs/131710.phtml

If you used the AAN 29 tooth water pump on the ADU, then you need the 151 tooth AAN timing belt.

AAN and ABY Timing info (use the flywheel mark and the window in the bell housing for best results):

http://forums.quattroworld.com/s4s6/msgs/136943.phtml

The RS2 ADU cam sprocket mark should be about 1/2 a tooth to the left (when facing the front of the engine), towards the exhaust manifold, when compared to the straight up mark to mark for the AAN and ABY

Reference photo: Post 12 in: http://www.s2forum.com/forum/showthread.php?t=64572

This is the correct RS2 cam timing (with the crank timing on its mark):




Hope that helps.

[minim]

Oh nice. Thanks for the info! I was going insane in my garage trying to figure out this thing. To me that looks like half a tooth out but if it should be like that I'm happy

[twoqu]

You should not be using the crank pulley mark for TDC as the pulley is known to deform. Use the flywheel mark.
The part number for the water pump quoted is because it looks like Audi use the 5 Cylinder TDi water pump casting with the RS2 pulley.
Looking at the pics it looks as though your cam pulley might have been replaced with perhaps an ordinary AAN/ABY one. Perhaps it was damaged or failed. Look closely and there is neither the big B or the hole at the top on the rotor in the TDC position. Might be worth investigating as the hall sensor wheel is in a different place on the RS2.
Are you getting any Camshaft hall sensor faults by chance?

[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?

[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]

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]

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

[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:

[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?

[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.

[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]

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]

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]

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?