Why timing BELTS and not timing CHAINS!?

[weltweit]

a 10 year old car isnt worth much ( IYKWIM ) but worth more to me as a decent way of lugging shit around, so hopefully the belt change will be a sensible move

Indeed. I just changed (a garage did it) the belt on my 14 year old Rover.

Its worth at the most £600 so its worth less than the cost of replacing all four tyres on a BMW X5 !

To me, it is transport and fine enough.

 

[Sigmund Fraud]

So, about F1.. they rev pretty high RPMs... how do their valve trains work?

http://scarbsf1.com/valves.html

Though Honda had a 4 cylinder 4 stroke racer in 1979 that could rev to 22,000 and had 32 valves - with conventional cams.

http://world.honda.com/MotoGP/history/NR500/

 

[weltweit]

http://scarbsf1.com/valves.html

Though Honda had a 4 cylinder 4 stroke racer in 1979 that could rev to 22,000 and had 32 valves - with conventional cams.

http://world.honda.com/MotoGP/history/NR500/

Thanks for the link, that is interesting, especially the Renault cam less system.

Yamaha have gone to 5 valves per cylinder since the FZ750, three input and two exaust.

While we are about it some small Toyota's on the market have variable valve timing VVTi its called. Sounds clever.

 

[Juice Terry]

Early V twin dukes had the bevel drive shafts too, you can see them here runnign up the sides of the cylinder heads.

 

[DownwardDog]

So, there are:

1) crancase located cams with pushrods a la Triumph & BSA motorcycles.

2) Vertical shafts and bevel gears a la Ducati single motorcycles.

3) Cam chains integral to engine casings a la OHC & DOHC motorcycles from Japan.

4) Cam / timing belts a la motor cars of today, most of them but some like Volvo have chains.

5) Gear driven overhead cams a la Honda RC30-RC45-VFR

Is that about it, or are there other ways to drive camshafts / actuate valves (excluding desmo as its just a way to do away with valve springs and mechanically open and close valves from a cam shaft.

Yes, there is the Ultramax system on NSU motorbikes of two reciprocating con rods driven by eccentrics on a reduction gear and driving eccentrics on the end of the camshaft. This was far better than the chain technology in the 50s as it could reliably rev higher. The whole system was forgotten about when NSU stopped bike production in 1963.

Massive diagram of it here for those interested.

 

[berniedicters]

didnt the CX500 slug have similar chain probs ? Im sure the tensioners didnt work too well

"Knock knock"

"Who's there?"

"Honda camchain tensioner"

Well-known '80s joke to be told in earshot of Honda-owning mates at every opportunity.

 

[weltweit]

Yes, there is the Ultramax system on NSU motorbikes of two reciprocating con rods driven by eccentrics on a reduction gear and driving eccentrics on the end of the camshaft. This was far better than the chain technology in the 50s as it could reliably rev higher. The whole system was forgotten about when NSU stopped bike production in 1963.

Massive diagram of it here for those interested.

That's interesting. I had to look at the diagram to see how it worked, I have never seen that system before.

 

[DownwardDog]

That's interesting. I had to look at the diagram to see how it worked, I have never seen that system before.

Honda also have a ton of patents on 'camless' electromagnetic valve actuation but I guess that's not ready for prime time yet.

I've often pondered why a manufacturer doesn't do an SOHC motor with the camshaft directly driven by an electric motor. I think the control technology is now good enough to match 50% crankshaft speed almost instantly and it would make the engine lighter, cheaper to build, more reliable and easier to maintain.

 

[weltweit]

I've often pondered why a manufacturer doesn't do an SOHC motor with the camshaft directly driven by an electric motor. I think the control technology is now good enough to match 50% crankshaft speed almost instantly and it would make the engine lighter, cheaper to build, more reliable and easier to maintain.

Yea, but if your battery went flat (for any reason) your engine would be f**ked!

 

[not-bono-ever]

Honda also have a ton of patents on 'camless' electromagnetic valve actuation but I guess that's not ready for prime time yet.

I've often pondered why a manufacturer doesn't do an SOHC motor with the camshaft directly driven by an electric motor. I think the control technology is now good enough to match 50% crankshaft speed almost instantly and it would make the engine lighter, cheaper to build, more reliable and easier to maintain.

patent the fucker ..quick!

 

[cybertect]

Yes, there is the Ultramax system on NSU motorbikes of two reciprocating con rods driven by eccentrics on a reduction gear and driving eccentrics on the end of the camshaft. This was far better than the chain technology in the 50s as it could reliably rev higher. The whole system was forgotten about when NSU stopped bike production in 1963.

Coincidence that NSU also produced the first Wankel engined car (which also allowed high revs up to 17,000 rpm and I think inherently is devoid of a timing chain/belt)?

 

[DownwardDog]

Yea, but if your battery went flat (for any reason) your engine would be f**ked!

The engine wouldn't start anyway if the battery were flat. What I envisaged was a closed loop system with seperate crankshaft and camshaft speed sensors. If, for whatever reason, the camshaft couldn't maintain 50% crankshaft speed to within an acceptable tolerance then the ECU would shut the engine down. I also anticipated that the ECU would run diagnostics and a calibration test on the camshaft motor before the engine starts.

There are already patents for electrically driven camshafts but they all rely on mechanical speed control; I think technology is now good enough to do this electronically.

 

[weltweit]

The engine wouldn't start anyway if the battery were flat. What I envisaged was a closed loop system with seperate crankshaft and camshaft speed sensors. If, for whatever reason, the camshaft couldn't maintain 50% crankshaft speed to within an acceptable tolerance then the ECU would shut the engine down. I also anticipated that the ECU would run diagnostics and a calibration test on the camshaft motor before the engine starts.

It does seem fraught with risk to me, risk of valves hitting pistons. Of course if you did it on a safe motor - my old 2l Cavalier was safe, the belt snapped and nothing happenned, just the engine stopped, the AA repaired it (fitted a new belt) at the side of the road.

But why even have a camshaft, why not have solenoid operated valves?

 

[weltweit]

How do injectors work?

Do they have any moving parts?

 

[DownwardDog]

It does seem fraught with risk to me, risk of valves hitting pistons. Of course if you did it on a safe motor - my old 2l Cavalier was safe, the belt snapped and nothing happenned, just the engine stopped, the AA repaired it (fitted a new belt) at the side of the road.

I'm just thinking aloud really. I'm not actually building this in my shed! There are probably some very good reasons why it's not yet feasible.

But why even have a camshaft, why not have solenoid operated valves?

Cost, I think. Imagine you've got say, 15mm valve lift and the engine revs to 8,000rpm. That's 4,000 times a second you've got move the valve 15mm up and 15mm down. It's going to take a pretty flash solenoid to do that operation in 2.5*10^-4 seconds, do it accurately and repeatedly for the 10 years of the car's life. Then multiply that cost by 16 or 32 for the whole engine...

 

[DownwardDog]

How do injectors work?

Do they have any moving parts?

Sure, solenoids, springs and valves.

http://en.wikipedia.org/wiki/Fuel_injection#Functional_description