Vr6 timing check

[maff 10]

Trying to get to the bottom of the lack of power over 5000rpm in my vr6, replaced the leads, maf, checked coil pack but I suspect the timing is not quite right, cars drives fine with loads of low down torque but feels noisy and breathless at high rpm.

 

We have the crank pulley lined up with the line on the block to the notch on the pulley, so if we take the rocker cover off to check the camshafts we should be able to slot the timing plate into the end of the slots in the camshafts which are horizontal, does this mean everything's timed up correctly?

 

Don't really want to take the gearbox out but if we have to we will!

 

Gonna be tackling this tomorrow morning:-)

[maff 10]

Update, we've just checked the camshafts and they do not line up.. so can we take off the top chain cover release the tension bolt for the guide, undo the camshaft sprockets to line up the camshafts to fit the tool with the bottom pulley at bottom lined up? Or do we have to align the intermediate sprocket as well?

 

Hoping some experts can help with this:-) my mate has his own garage and has built and timed his own vr6 mk1 but he's unsure whether we can re time the engine with out having to remove the gearbox?

[Jim Bowen 1]

The intermediate sprocket has to be correctly timed as well. Is possible to have that 180degrees out which can affect the engine

[Jim Bowen 1]

Step 21 or 22 on this guide shows the notch that should be visible with just the top cover removed.

 

http://forums.mwerks.com/showthread.php?1264409-DIY-Replacing-timing-chains-tensioners-and-guides-on-a-12v-VR6

[Jim 1]

Hmmm... seems to divide opinion having a read around on whether timing of the intermediate shaft / sprocket matters... see here:

 

http://forums.fourtitude.com/showthread.php?4361072-vr6-intermediate-shaft-timing#/topics/4361072?_k=muv09w

 

May help you make up your mind either way.

[Jim Bowen 1]

It was Vince that told me it does matter so i agreed with him.

[Jim 1]

He tends to know what he is talking about :)

[maff 10]

Expensive mistake if we ignore the intermediate shaft then?

[Jim Bowen 1]

No. It doesn't mean piston/valve contact, but can cause loss of power. Can't remember vinces explanation well enough to explain though

[Harrier 1]

The intermediate shaft can be checked with a mirror once the top chain cover is off, if you can't see the notches you might have to turn the crank 1 or 2 revolutions and look again .

I have heard of the cam pulleys not aligning perfectly before i.e half a tooth out or so. Possibly down to the head having been skimmed or wear, stretch in the chain.

[maff 10]

Ah that's good news harrier! I can't believe how torquey the engine is low down if the timing is incorrect? It's the like the top and bottom end have swap power characteristics?

 

That's the thing I used to love about my old vr's they needed driving g hard to enjoy them, a lot like the m3 I've just sold, but as it is now it feels like a turbo diesel/-)

[Dox 22]

On a 4 stroke engine the cams rotate at half the speed as the crank hence 2 rotations (720 degrees) for the 4 cycles (suck, squeeze, bang, blow or induction, compression, ignition, exhaust)

 

On the VR6 engine the gearing down is done by the intermediate shaft, one of the of the 2 sprockets has an odd number of teeth so you can be half a tooth out (cam timing advanced or retarded), because of this the ignition timing is also thrown out as the cam sensor picks up off the cam sprocket + lumpy running and low power.

[maff 10]

This is my mates take on it who is the expert, I'm just helping..

 

The way I see it,bottom pully goes to inter pully,then inter to the top,if the bottom crank pully mark is lined up then that is top dead centre,remove cam bolts,remove chain and sprockets move cams till

They lock in the plate,refit sprockets and chain,the inter sprocket may be out but the timing will still be correct,it only turns the oil pump,it could be that it's just the top that's out too and the bottom pully and intershaft may be correct to start with

[maff 10]

I think the reason why it's important for intermediate shaft to be timed is because it has different size cogs on inside and outside for crank and cams

[Jim Bowen 1]

When you disconnect the cams and then turn bottom end to the pulley mark, just cgeck that notch on the intermediate shaft is visible from above like the photo. If not, turn the crank again until and check the intermediate, shouldn't need to take gearbox off. Then do the rest as planned

[Dox 22]

You need to remove the cams completely (so that all 12 valves are closed) before rotating the crank, if you don't the moving pistons will hit the open valves

[Jim Bowen 1]

Oh yeah, that's quite important thing to mention :lol:

[maff 10]

All fixed!

 

Removed everything to expose cams and top chains, then checked the intermediate shaft (which luckily lined up) while the bottoms crank pulley was on tdc.

Then slackened off cam bolts to lift cams and turn them with the chain still attached untill we could slot the tool in. Retorque camshaft to correct spec refit guide tensioner bolt and reassemble.

 

Fired it up and sounded spot on, then took it for a test run, (waiting for the oil to get to temp) and then try WOT, which concluded there was no tailing off of power above 5000rpm:-) engine came on strong at 4500 and pulled hard to 6000rpm as I remembered how they should do.

 

Thanks for the help, so glad we got it sorted

 

 

Quick pic of the car

[seanl82 23]

Great news and well done for persevering! Hope you get to fully enjoy it now! :thumbleft:

[maff 10]

Cheers Sean, still got to fit the leather and heated loom, then get dent devil bloke to sort a few small bits, there was a pipe off on the brake circuit which made the 288 brakes horrendous which is sorted but new pads are needed so I'll order those in the new year, haven't even driven it yet as I was a passenger on the test run

[maff 10]

Oh and after going through all this and having a look at vr6 engine under the bench which is goosed, the intermediate shaft is free to spin which drives the oil pump so even if the timing marks were out on the intermediate shaft surely it doesn't matter if it doesn't line up?

[Dox 22]

Oh and after going through all this and having a look at vr6 engine under the bench which is goosed, the intermediate shaft is free to spin which drives the oil pump so even if the timing marks were out on the intermediate shaft surely it doesn't matter if it doesn't line up?

 

It does matter, can you post a pic of the sprocket please?

[maff 10]

This is the best pic I have as couldn't get it with the poxy phone flash, but it was the same as the vr6oc guide pic

 

 

Same as this

 

I was expecting the intermediate shaft to be out but luckily it wasn't, so all we had to do was get the cams cock on with the locking tools, pulls hard now so all good, that's a weight off!

Edited November 19, 2016 by maff

[Dox 22]

Oh, I thought you had a spare engine with the covers off?

 

Good result anyway :)

[maff 10]

Yes we have! I can get some pics if you want a look?