What Happens When The Police Impound Your Car?

[Steve Walker]

The cam-in-cam stuff is an ingenious way of getting variable exhaust valve timing on a pushrod engine, but I can't help but think that the solutions for OHC engines are more elegant. Honda's VTEC system only used to be able to vary intake timing on SOHC engines, but they now have a system which varies exhaust timing too. On a performance engine, a DOHC system with variable timing on intake and exhaust must be a more sensible direction than seeing how far you can develop a dinosaur.

 

Cam-in-cam

 

Youtube Video ->

[Worms]

The cam-in-cam stuff is an ingenious way of getting variable exhaust valve timing on a pushrod engine, but I can't help but think that the solutions for OHC engines are more elegant. Honda's VTEC system only used to be able to vary intake timing on SOHC engines, but they now have a system which varies exhaust timing too. On a performance engine, a DOHC system with variable timing on intake and exhaust must be a more sensible direction than seeing how far you can develop a dinosaur.

 

Cam-in-cam

 

Youtube Video ->

 

 

Yes I agree with you, I suppose the problem is the cost of re-tooling to make a new DOHC engine.

 

Personally If I had a choice I'd prefer a 4 valve DOHC engine with fixed valve timing with some wide overlap than a concentric variable cam system stuck in the 'v' if I was racing flat out on the American ovals, which is what I assume this car has been built for (proddy racing). I suppose the concentric single cam design has been designed to allow the road driver to drive to the shops without popping and banging and throwing neat fuel all over the street!

 

Still, neat and tidy and they are claiming long service life so good luck to them (wonder if I can squeeze a shortened one in my 4.6 v8?)

[Angly]

Veering slightly off topic, seeing as we have some engine fans here, anyone ever know what happened to the starter-motor-less start idea? The idea was that, in these times of electronic engine management, that the starting circuit would detect which cylinder was after TDC on the firing stoke, squirt a charge of fuel in, and ignite it. Obviously this would be easier to achieve, and smoother, the more cylinders one had to play with, and perhaps testing would show the lower limit might be 5 or 6 pot.

[Worms]

Veering slightly off topic, seeing as we have some engine fans here, anyone ever know what happened to the starter-motor-less start idea? The idea was that, in these times of electronic engine management, that the starting circuit would detect which cylinder was after TDC on the firing stoke, squirt a charge of fuel in, and ignite it. Obviously this would be easier to achieve, and smoother, the more cylinders one had to play with, and perhaps testing would show the lower limit might be 5 or 6 pot.

 

I don't know of the precise system you mean, any ideas who thought of it?

 

I suppose the problem there is getting a charge to ignite without compression without causing engine damage. My guess is that the complexity of such a system would be so expensive to develop and produce that a starter motor is a much more efficient option.

 

Problems to overcome would be guaranteeing that one cylinder at least is at the right place, or varying the amount of fuel and spark intensity for a piston somewhere near the optimal position. As you say the more pots the better for that, but then you have a lot more mass to get moving from the initial charge.

 

Computer systems to manage the starting variables and appropriate sensors would add to the complexity but, no doubt this is possible.

 

Might be easier to achieve using LPG as a fuel!

[Steve Walker]

That kind of thing might also be easier to achieve in the next generation of direct injection, camless engines, I suppose. Losing the weight and complexity of an electric starting system might be a good thing, although integrated starter/alternator/mild hybrid drive systems may make the move redundant.

[Angly]

I'm sure it was originally mentioned on Tomorrows World, no idea who the manufacturer was unfortunately.

[Worms]

I'm sure it was originally mentioned on Tomorrows World, no idea who the manufacturer was unfortunately.

Bosch have nearly done it!

 

Click here!

[Angly]

Bosch have nearly done it!

 

Click here!

 

Oh well found!

 

 

Interesting that it's not a total solution, and they still need a starter motor some of the time. I imagine the first market will be in hybrids, does anyone else switch of the engine at the lights as mentioned?

Edited February 11, 2009 by Angly

[Steve Walker]

I think BMW's Efficient Dynamics package turns the engine off whenever the car is stopped. VW's Umwelt system fitted to early 90's Golfs did something similar (though Efficient Dynamics includes loads of other detail changes, and some clever management of the alternator so that where possible it only adds a parasitic loss on the overrun).