Crankshaft Sprocket and CPS 'star' pickup

Heard a number of folks referring to the 'huge damage' that can occur if the star slips.

Just curious really as the what actually happens to cause the damage?

The star is held in place by the crank pulley isnt it? Fairly high torque on that bolt if it is!

The star is basically clipped on the back of the timing belt "cog", its function is to trigger the crank sensor as it rotates, ive never heard of any damage being caused from it coming off other than the car runs crap or even cuts out, it could be the crank pulley you`re thinking of.

Ryan mentioned it at SRR, and now i have seen Paul Whiffin mentioned it in M5W TT's build thread.

Mine will be tig welded for sure!

Pretty sure Michel welded mine too when mine was being put together, pm him he will know

yep Paul has welded mine this was on the advise of Whifbitz due to personal experience with a failure.

http://www.mkivsupra.net/vbb/showpost.php?p=2369564&postcount=111

How can it slip? Is it a seperate part or is it riveted to the pulley or something?

If it is a seperate part it will be dowelled or keyed to the crank somehow. The crank position wheel is the engine' primary indicator of where the engine is in the four-stroke cycle. It is used as a reference for fuel and ignition timing.

Im guessing its pressed onto the crank cog, which has the keyway

IIRC (from 2 months ago when i replaced the crank pulley) it has a woodruff keyway itself.

Was looking for a pic, but its keyed to the back of the crank pulley (timing belt) and is jammed between the shoulder on the crankshaft and the pulley and shouldn't come loose unless the location tabs break, and if that happens in theory it should just be free to rotate, so it shouldn't do more than just stop the engine, as the reference signal would be lost.

It doesn't slip it just first starts to wobble around and then falls off.

The wobbling part is the worse bit though as incorrect timing info can be given to the ecu where the air gap is changing rapidly

So, perhaps not critical damage, more a chance the car will run rough.

Wonder what happened on Pauls car then. Could it get so bad that the car would go lean and det and thus damage?

I would imagine that the little wobble at 7,000RPM and 1.6 bar is all it takes:(

So, perhaps not critical damage, more a chance the car will run rough.

 

Wonder what happened on Pauls car then. Could it get so bad that the car would go lean and det and thus damage?

TBH its hard to say but the worse i have seen happen is one fall off at 7k and just cause a massive backfire and then a 1.5 tonne paper weight

Ryan

I have seen this a couple times now. The star pickup seperates from the sprocket.

You can weld it on or what I do is go round with a centre punch where it joins. That stops it from coming off and handy if you dont have a welder.

One thing it does damage when it comes off is the crank postion sensor, puts a nice dink in the end of it.

TBH its hard to say but the worse i have seen happen is one fall off at 7k and just cause a massive backfire and then a 1.5 tonne paper weight

 

Ryan

Ouch Glad Paul sugested it now.

This is the first I have heard of this, interesting stuff.

Michel Lane has been doing it for years after he experienced it a few times of a few customer cars. Definatly worth doing IMO

when i first did my front oil seal i didnt remove the alloy tab that bolts on the oil pump using a 10m head. s i refitted the cog with timing star on i had to knock the cog on so didnt realise that the star was being bent (1 tooth) put it all back together and it started just but was really missfiring, then my new cambelt started to chafe onthe inside edge and i mean enought to scrap it, so took it all apart and saw the tooth bent, still not realising how or why, so took it off the timing cog and knocked it back striaght, refitted it and bent again lol. by this time i was like what the hell then niticed this little alloy tag and this was causing the problem so if you ever take the cambelt pully off remove the little alloy tag. Bottom right as your looking at the engine.