Any way to check if knock sensors are being too paranoid? VR

[Funkster 0]

'lo all,

 

I fitted a new cam sensor last night as that was the only fault code showing, but I still don't have all my horsepower back. Is there any way (using VAG-COM or otherwise) to check if the ECU is retarding the ignition for any other reason? That's what it feels like it's doing, no torque anywhere really and it gets hotter than it should I'm sure, plus it uses more fuel than it really has any right to.

 

Just to give you the full story... tore the engine to bits (at 161K) and rebored +0.5mm, lovely new OE pistons and shells, had a very slight head skim and lapped the valves back in, fitted new chains. It's run in now (1700 miles) but it's not been properly right horsepower-wise since it went back together, plus to be honest it's still quite rattly - I'm thinking (hoping?) tappets.

 

However, I *think* I have breifly seen all the torque while the cam sensor was dicking around, it was just very sporadic. Now it's fairly rubbish all the time.

 

Pretty fed up with it as you might imagine - the performance is the only thing that justifies all the bloomin' expense!

 

Cheers in advance for any ideas,

--

Olly

[dr_mat 0]

I assume you reset the ECU after swapping the cam sensor .. ?

[Funkster 0]

I cleared the fault codes, is that the same thing?

 

Cheers,

--

Olly

[plateletboy 0]

if it has stored lots of 'innapropriate' adapted values over the 1700 miles it may take time for the ECU to relearn more suitable ones...

Disconnect battery for 5 mins and then follow the ECU reset procedure in wiki and the vagcom basic settings...

 

I doubt it is this though if you can really feel a major loss of power....

 

pb

[Kevin Bacon 5]

Is there any way (using VAG-COM or otherwise) to check if the ECU is retarding the ignition for any other reason?

 

Yeah you can use VAG-COM to creat a nice log for you.

 

You want to fire up the rpm, lambda, throttle angle, knock, intake temp, ignition advance and injector duty Measuring blocks. The MAF block would be nice too but OBD1 is schitt and doesn't tell you the air mass.

 

Once you have those blocks up on screen (i can't remember the block numbers, but scroll through them and you'll soon see them, there's only 8 or so usable ones on OBD1), hit the log button and take it for a drive to induce pinking.

 

Get back and stop the log. It will save it as a Microsoft Excel (xls) file in the log directory.

 

Open up the spreadsheet and you should have some columns representing your measuring blocks - rpm, lambda, throttle angle, injector, knock regulation, ignition advance, etc etc

 

If there are any minus numbers in the knock regulation column, look at the rpm, throttle angle and injector duty time to form a snap shot.

 

For instance, if you're showing -4 knock reg at 3000rpm, throttle 95%, ignition 27 deg, injector time 8ms, intake temp 50 deg C, then a touch of knock is to be expected.

 

If you're showing say, -6 knock at 2000rpm, 30% throttle, ignition 33 deg, Intake temp 30 deg, injector time 5ms, then that's a problem!

 

Ideally, knock reg should stay at 0, but don't panic if you see -6, that's only a couple of degrees. VW use units of retard, not actual degrees.

 

If all looks OK in there, I'd guess you might have got the cam timing wrong, which affects the sequential injection aswell as the cam's advance and retard.

[Funkster 0]

Thanks for a very informative post! I'll do exactly that on the journey home, and try taking the battery off this evening to see if it makes any difference.

 

cam timing wrong

 

That's my next thing to check, I thought I lined it all up as per the manual but it might be half a tooth out or something. Think I'll get a set of tappets and check the timing at the same time as changing them.

 

Cheers again,

--

Olly

[Funkster 0]

Had a crack at this on the way home, but couldn't see a measuring block with knock in it. Blocks stopped existing at ~10 and I got bored of clicking 'up' after 100 or so and not finding any others.

 

I'm only running 640x480 on the pooter in the car, so can only see four elements in each block... are there more, with the knock one off the right hand side? If so I'll just do a log and read it back from the .xls later.

 

Cheers,

--

Olly

[andy 0]

Valve timing, its so important and so easy to get wrong.

[dr_mat 0]

Have to say, I don't recall seeing a knock retard in the measuring blocks on my VR either. Ignition timing yes, but no knock retard.

[Funkster 0]

Indeed, tried a battery-off reset this morning and it hasn't majikally restored my power.

 

Urgh, cam timing... am I right in thinking that if the idler is out of position with respect to the crank, there's no way to correct it without taking the engine out / flywheel off etc.?

 

B@$!@£€ Corrado! Why must you taunt me so?

 

Cheers all,

--

Olly

[Kevin Bacon 5]

Ah, my bad. It's only OBD2 that gives you knock data. Sorry, it's been a while since I've been anywhere near the Jurassic OBD1.

 

You can buy 'knock link' kits though, which splice into your knock sensor wires (at the ECU end) and light up LEDs on the dash when it's knocking.

 

If the intermediate shaft is in the wrong position, it's a gearbox off job, yeah :( I would speak to Vince at Stealth first because there is some confusion surrounding the intermediate shaft and it's affect on the timing. In theory it just turns the oil pump, but it also some a relationship with the timing and I can never remember what it is!

[Funkster 0]

tbh I might just take the car to stealth and get them to sort it, it needs new front wheel bearings anyway and I really can't be bothered with taking the engine out again. I want to get on with sorting my MG out in time for the good weather!

 

Cheers,

--

Olly

[Kevin Bacon 5]

Don't blame you!

 

It does get to a point where you think, "Can I really be arsed? Nope, off to Stealth with it".

 

Sort the MG? Your 300hp Morris sounds fun :lol:

[Funkster 0]

Need to sort the morris too - the diff exploded while doing this:

 

 

That was well over a year ago and it's been languishing in the garage ever since.

 

Funnily enough, the diff pinion bearings failed in the MG due to one too many enthusiastic departures from traffic lights.

 

Old hot rods in garage: two

Working axles in garage: zero!

 

ttfn,

--

Olly

[Kevin Bacon 5]

Smart 8)

 

You don't see many 1930s cars doing that from the traffic lights :lol:

 

Hope you get all your beasts sorted!

[NormanCoal 0]

If the intermediate shaft is in the wrong position, it's a gearbox off job, yeah :( I would speak to Vince at Stealth first because there is some confusion surrounding the intermediate shaft and it's affect on the timing. In theory it just turns the oil pump, but it also some a relationship with the timing and I can never remember what it is!

 

 

If you follow the described timing procedures, then there are two positions for the intermediate shaft, but considering that the only job that shaft does is drive the oil pump, I fail to see any reason why it would make any difference at all in where it is when doing the timing. To the best of my knowledge, as long as the bottom and top end are timed correctly, there will be no difference - the cam(s) to crank timing is either correct or wrong.

It can easily be checked though, and without the gearbox coming off

[dr_mat 0]

The above post makes perfect sense, but for some reason I've been told the opposite - you must get the alignment of the middle sprocket right too..

I have no idea why, can't explain it.

[Funkster 0]

I can explain it - the two gears on the intermediate shaft (obviously) have different numbers of teeth, I forget the math now (it's late) but for the sake of argument let's assume that they don't divide into each other at all. Thus, to get any given tooth of the inner gear to line up with some imaginary reference position, the outer gear can only be in one of its n (n = number of teeth) possible positions. Every other position will cause the inner gear to be out by 1/n teeth.

 

In actual fact the ratio of teeth between inner and outer gears on the idler is 2:1 (right?) so moving the outer gear one tooth moves the inner by a half - so the idler is in an acceptable position once every two outer teeth.

 

Or, something.

 

I could've sworn I got it lined up when I put it together, though.

 

I reckon I'll check the timing myself and if it's wrong, ship it off to Vince.

 

ttfn,

--

Olly

[NormanCoal 0]

I know this is at a slight tangent to your original post, but I'm now curious about this.

 

Regarding what is written above, to which I can understand perfectly, I can see where you are coming from, but I'm pretty certain that isnt true - be interesting to see whether it is or not though

[Funkster 0]

I suppose it depends how far off the cams have to be before performance is affected. If they can be out half a tooth at the cam gear with no measureable ill effect then you're absolutely right.

 

Cheers,

--

Olly

[Kevin Bacon 5]

If you follow the described timing procedures, then there are two positions for the intermediate shaft, but considering that the only job that shaft does is drive the oil pump, I fail to see any reason why it would make any difference at all in where it is when doing the timing. To the best of my knowledge, as long as the bottom and top end are timed correctly, there will be no difference - the cam(s) to crank timing is either correct or wrong.

It can easily be checked though, and without the gearbox coming off

 

Yes, the marker on the int shaft should point north. If it's 180 degs out, it causes problems. And yes, you can inspect the shaft's position with a dental mirror and a light, but as I say, if it's in the wrong position, you can't realign it without dropping the box.

There's no ryhme or reason to this, other than VW purposefully giving the intermediate shaft timing marks (why would they bother if it makes no difference?) and every single VR6 stealth have seen that's down on power has had timing issues.....usually the int shaft 180 deg out (pointing south). I think it's something along the lines of what Funkster described.

[NormanCoal 0]

With regards to the timing being out 180 degrees on that timing mark, I'm pretty certain that the Bentley states it can be in one of two positions, being 180 degrees from each other. Pity its at home cos I'd like to see what it says.

 

I'd like to see a definitive answer to this from somewhere, v curious now

[Funkster 0]

Both Bentley and the wiki here state that it doesn't matter whether you use the top or bottom mark. There must be an even number of teeth on the outer part of the gear so in theory it should make no difference... but theory and practice are often quite difference!

 

*edit* scratch that... if there are an odd number of teeth on the inner gear then putting round 180

[NormanCoal 0]

I have an outer chain wheel (the small one) at home I can check, but prob wont be till tonight

[Funkster 0]

Just had a look at the wiki, outer has 32 teeth inner has 18, so rotating it 180