Does ECU monitor cam chain, sprocket wear?

[Constant Mesh]

It would seem the FJR's ECU could monitor the cam chain's stretch and chain sprocket wear by comparing the inputs from the cylinder identification sensor located above the exhaust cam and the crankshaft's position sensor (pickup rotor).

As the chain stretched and the chain and sprockets wore over time the timing between the exhaust camshaft and the crankshaft would change in small, but detectable amounts.

If the ECU measured and stored this timing differential when the engine was first operated it could compare the initial reading with subsequent readings taken during the many hours of engine operation.

It might be feasible to generate a maintenance error code on the display to let the operator know when the chain and sprockets needed replacing or some timing anomaly was detected.

 

[wfooshee]

Since the ECU doesn't control cam timing it has no reason to monitor it.

Even if it did control it, like some variable valve system, it would monitor the actuator and not the actual physical timing.

 

[ionbeam]

Gone fishing:

 

[Fred W]

The ECU will show a fault condition when the chain breaks or comes off one of the sprockets. You'll recognize the alarm as a briefly occurring loud banging noise followed by an even louder silence. :blink:

 

[Silent]

The ECU will show a fault condition when the chain breaks or comes off one of the sprockets. You'll recognize the alarm as a briefly occurring loud banging noise followed by an even louder silence. :blink:

I heard that alarm once on an old 500 going about 70 :blink: Had no trouble at all hearing it over the locked up rear tire either :dribble:

 

[HaulinAshe]

Nice thought, but the cam chain "stretch" or wear is taken up by the tensioner mechanism. Therefore the relationship of exhaust cam timing to crankshaft timing really doesn't change.

However, the relationship of exhaust cam timing to INTAKE cam timing does change with chain wear/stretch, because there is no tensioning mechanism between the two cams. I doubt any kind of pressure sensor could detect that variation until it reached the critical alarm stage as so vividly described in an earlier post by FredW.

 

[Kevin Daly]

I see what your saying. you are proposing that there is a roughly linear relationship between timing and total stretch of the chain (pluse wear of the sprokets). if only you knew what that relationship was you could predict when the chain/tensioner was "done"

Interesting :dribble:

 

[Kevin Daly]

Nice thought, but the cam chain "stretch" or wear is taken up by the tensioner mechanism. Therefore the relationship of exhaust cam timing to crankshaft timing really doesn't change.
However, the relationship of exhaust cam timing to INTAKE cam timing does change with chain wear/stretch, because there is no tensioning mechanism between the two cams. I doubt any kind of pressure sensor could detect that variation until it reached the critical alarm stage as so vividly described in an earlier post by FredW.

No man I think he is right. the fact that there is a tensioner only means that the slack is to one side of the assembly. given that the number of links is not changing, the total ratio of chain to one sider versus the other will change and thus the relative position of the sprokets of the crank and exhaust cam will be slightly altered.

:dribble:

 

[HaulinAshe]

Fine, make me go pull the drawing and think hard. Yep, it might be feasible.

However, I bet that a travel (limit) sensor integrated into the tensioner mechanism would give a more reliable and predictable reading, perhaps for less development and production costs.

Biggest issue I see with sensing the timing differences between the crank and the exhaust cam, is all the cumulative play/backlash versus actual wear/stretch in the chain. I believe the changes in the chain would be too subtle to detect amongst all the other "activity" going on. You would need a lot of history stored for comparison and then generate the error based on historical averages.

With a cam chain tensioner travel sensor, you could simply say "Ooops! Your cam chain appears to be worn because I finally traveled to this point and stayed there for more than 10 seconds".

 

[Kevin Daly]

Fine, make me go pull the drawing and think hard. Yep, it might be feasible.
However, I bet that a travel (limit) sensor integrated into the tensioner mechanism would give a more reliable and predictable reading, perhaps for less development and production costs.

Biggest issue I see with sensing the timing differences between the crank and the exhaust cam, is all the cumulative play/backlash versus actual wear/stretch in the chain. I believe the changes in the chain would be too subtle to detect amongst all the other "activity" going on. You would need a lot of history stored for comparison and then generate the error based on historical averages.

With a cam chain tensioner travel sensor, you could simply say "Ooops! Your cam chain appears to be worn because I finally traveled to this point and stayed there for more than 10 seconds".

And you would think... given the cost of a failure there, that they would have some sort of indicator

 

[HaulinAshe]

I'm seriously considering replacing both the chain and tensioner this winter. That will be between 60,000 and 75,000 miles.

As much of a PITA it is to do, $90 worth of parts buys a lot of piece of mind, not to mention the performance gains.

 

[Kevin Daly]

seems like a wise choice if you can do it.

 

[ionbeam]

I see what your saying. you are proposing that there is a roughly linear relationship between timing and total stretch of the chain (pluse wear of the sprokets). if only you knew what that relationship was you could predict when the chain/tensioner was "done"
Interesting :dribble:

One way to measure the mechanical timing of the valve drive system is to directly measure the effect of the wear. This could be done by error measurements taken between the drive sprocket (on the crank shaft) and the exhaust cam action. As the chain wears the exhaust cam timing will become ******** and this can fairly easily be measured. This method will tell you when performance is being compromised but will not tell you when the cam chain is reaching the point of excessive wear.

Another way to measure the health of the valve drive system is to monitor the forces on the chain tensioner with a strain gauge. A strain gauge on the plunger shaft will show two things, one is the absolute force working on the chain slipper and another is the amount of force variation caused by 'chain snatch' due to lack of tension. The magnitude of force variation is probably the most important data. This will tell you when the chain has reached the end of service life, but will not tell you how much performance is being affected.

I believe my failure was in great part due to non-linear spring force of the tensioner. As the chain wore the tensioner had to extend to take up the slack. I can see wear marks on the tensioner plunger that shows plunger length when the chain was new and the wear mark extends to the point of failure. The spring in the tensioner was significantly stronger at the beginning of the wear mark than it was at the end of the wear mark. Ironically, the tensioner should have equal or stronger force as the chain wears but in fact it gets weaker as the chain wears. This is where a strain gauge would have provided very useful data from which to make a wear evaluation.

There are a lot of engine, chassis and electrical functions that could be monitored. In these days of advanced power train, drive train and chassis computers much of this could be done at very little cost. Heck, the ECU already monitors battery voltage as part of the fuel injection algorithm, how hard would it be for the ECU to tell you your battery voltage is getting low? Every engineering project has to have limits; every company decides what is important and sets targets based on these constraints and requirements.

 

[Aasland]

I think someone should make a kit to retro-fit our FJR's with gear-driven cams.

If I were a congressman (and not a libertarian) I would write a law to mandate that all motorcycles have gear driven cams. :assassin:

 

[ionbeam]

I think someone should make a kit to retro-fit our FJR's with gear-driven cams.
If I were a congressman (and not a libertarian) I would write a law to mandate that all motorcycles have gear driven cams. :assassin:

Ask Honda about their gear driven VFRs. I believe that Ducati would recommend you to take things a step further with desmodromic valves too.

 

[Fred W]

I think someone should make a kit to retro-fit our FJR's with gear-driven cams.
If I were a congressman (and not a libertarian) I would write a law to mandate that all motorcycles have gear driven cams. :assassin:

Ask Honda about their gear driven VFRs. I believe that Ducati would recommend you to take things a step further with desmodromic valves too.

[contributing to thread drift]

The gear driven VFR cam design has no issues that I am aware of other than the unique whining sound you get from it. It is considered a positive feature in VFR circles. It was ditched in 2002 in the 6th generation VFR when they went to VTEC variable valve timing, which was/is universally considered an abomination. The story I heard was Honda ditched the gear drive to make the bike quieter. :huh:

Desmo valve actuation is a thing of beauty, IMO. Separate overhead rockers for each valve (w/ adjustment shims) for opening and for closing. No traditional valve springs, you push the valve where you want it. No chance for valve float. The belt drive to the (later) cams, not so beautiful. High maintenance (replacement called for every 16k, but done @ 10k if you're smart) I'm not sure what the knock was with the bevel drive in the earlier models.

[/contributing to thread drift]

 

[radman]

Hell, lets go to these as long as we're at it

 

[skifrik]

Heck, why not just use solenoids to actuate the vales and do away with the cams completely.

 

[Fred W]

Heck, why not just use solenoids to actuate the vales and do away with the cams completely.

Believe is or not, traditional solenoids would not give the speed of actuation and degree of control over the rate of opening and timing that we get from the simple mechanical cam. It really is an elegant solution to valve actuation. Most of the problems that arise with cam actuated valves are in the area of driving the camshaft. It's either chains, belts, or gears. Of those three, gears are the most reliable.