A friend recently told me to "stop living in the last century" (with 8v technology) and that, coupled with the fact that I've just bought a 32v v8 got me thinking...

how do you like your power delivery for the following 4 areas

Town Driving

B Road Blasts

Motorway Cruising

Track Use

?

Low down torque every time, topped of with max power at the red line!

Most effective for the purpose it's put to.

There are theoretically some benefits to having 4 x smaller/lighter valves from an emmisions/performance perspective as they can be moved quicker/easier and don't knacker the cam so quickly.

I'd argue that VVT of some form is more useful than "nn" valves on the engine.

I like my power delivery to be there when I hit the go pedal. A good supply of torque distributed over a wide rev. range. After that it's down to the sensory experience. At which point the Fabia gets left on the drive and the Impreza is taken out for a gallop.

Now if someone made a very quiet exhaust for the Fabia that let off a bit of a scream after around 3.5K rpm, I might be persuaded to drive it even more.

J. (Spent over a year so far trying to make a Fabia VRS's handling "agile". Previous 2nd car was an AX GT).

Sudden, brutal and peaky.

Sudden, brutal and peaky.

Like my women

I like my women like I like my coffee.

Pale, weak and full of sugar.

Torquey and at low revs. Need something that can pull straight away in the same gear when I need a sudden wobbly HGV induced lane change. I like the revtastic petrol engines too, but in the day to day grind i find the torquey diesel power delivery more useful, if untimately less fun.

A friend recently told me to "stop living in the last century" (with 8v technology) and that, coupled with the fact that I've just bought a 32v v8 got me thinking...

how do you like your power delivery for the following 4 areas

Town Driving

B Road Blasts

Motorway Cruising

Track Use

?

Town Driving Lots of torque from idle upwards, good broad power band but not too high revving, basically so you can just chuck it in a gear and leave it there (apart from traffic lights of course!)

B Road Blasts As above

Motorway Cruising As above

Track Use As above

I like my women like I like my coffee.

In a plastic cup?

(lifted from an Eddie Izzard sketch on Bee-Keepers)

However, power delivery - I don't like turbo lag - when I prod the loud pedal, I want it to feel like I've just engaged the hyperdrive on the Millenium Falcon etc etc.

320d is just so lazy in it's delivery to the point i feel i'll be pensionable before it hits NSL....remapped pd130 takes off like a scalded cat.

Biiiiiig slab of torque at low revs, PD130 style.

Not so great in a PD140 but it's sufficient

lots of easy revving with a large slab of torque, i'd call 3500-6500 a nice sized slab so i'm quite happy with mine thanks

this is how i would like my power delivery , brutal

Click here to see Video

Plenty of torque for pootling about in....

Decent rev-range when im feeling the need....

oooh, that leave a V8 then

Altho i do love the PD130+ engines.. they have a certian "revvy" and grunty characteristic about them and i always smile after driving other cars then getting back into my own

There are theoretically some benefits to having 4 x smaller/lighter valves from an emmisions/performance perspective as they can be moved quicker/easier and don't knacker the cam so quickly.

but bear in mind that 2x camshafts and 16 valves and lifters makes more reciprocating inertia inside the engine, and as for emissions, it's mainly to do with the shape of the comustion chamber, and not the number of valves, plus on many modern 16v heads they have a wider squish band, and as for performance 16vengines normally have a wider power band because they have shorter duration cam profiles. and they will 'knacker' cams just as quick as 8v engines will, the hyraulic lifter is the most heavily loaded part in the whole engine...

so in real terms 8 or 16 valve!!! it makes no real difference, it all comes down to valve timing, the shape of the combustion chamber, and the shapeof the ports.

I don't do track days, so loads of drivable torque from idle up to about 4_000 rpm; oh, look, I have a turbo-diesel!

Lots of torque across a nice big rev-range

Chris

but bear in mind that 2x camshafts and 16 valves and lifters makes more reciprocating inertia inside the engine, and as for emissions, it's mainly to do with the shape of the comustion chamber, and not the number of valves, plus on many modern 16v heads they have a wider squish band, and as for performance 16vengines normally have a wider power band because they have shorter duration cam profiles. and they will 'knacker' cams just as quick as 8v engines will, the hyraulic lifter is the most heavily loaded part in the whole engine...

so in real terms 8 or 16 valve!!! it makes no real difference, it all comes down to valve timing, the shape of the combustion chamber, and the shapeof the ports.

I understand that overlap and emissions don't agree with each other. So the ability to snap the valves open and shut quickly is a benefit. A smaller, lighter valve is likely to settle quicker and without bouncing as much into the seat.

Agree about the combustion chamber shapes and squish etc.

Point I was trying to make about knackering cams is you need higher lift, shorter duration to avoid higher emissions but trying to lift bigger valves quickly increases the mechanical stresses involved and is likely to reduce the life of the valvetrain components.

Biggest benefit for having a twin-cam arrangement in a modern is IMO the ability to vary the timing of the cam(s).

J.

Biggest benefit for having a twin-cam arrangement in a modern is IMO the ability to vary the timing of the cam(s).

i would have said that the biggest benifit is having inclined valves which aren't as shrouded as 2 valve head and have a striaighter flow path, plus the spark plug is right in the centre...... it all adds up to better economy/emmisions

Of course, you could consider alternate methods of valve actuation, say Desmodromic valve gear for example.

Of course, you could consider alternate methods of valve actuation, say Desmodromic valve gear for example.

i must say, i've never come across them in cars before, but some of the 5 cylinder yamaha motorcyle engines have them......

how about pneumatic valve operation like f1 engines have, the best of both worlds, no friction, infinately varible lift and duration

Used in the 1950s Mercedes straight-8 (W196GP, 300SLR sports racer and Uhlenhaut (sp) coupe).

Wouldn't pneumatic actuation require a compressor and an air tank (for first thing to get the engine started)?

Weren't MG Rover developing a piezo-based injector/valve system thing where each valve had its own actuator, no camshaft needed?

Used in the 1950s Mercedes straight-8 (W196GP, 300SLR sports racer and Uhlenhaut (sp) coupe).

also used in the rolls-royce merlin aviation engines

Wouldn't pneumatic actuation require a compressor and an air tank (for first thing to get the engine started)?

yes it does, but the gain in performance is huge, plus also bear in mind these babies run at like 16,000 rpm...... a valve spring will only last about 5 mins at that speed

Show me a real road car (not a bike-engined Locaterfield type toy thingie) that runs at 16_000 or so (never mind the 18_000 to 20_000 that F1 engines actually used before the FIA capped the rev limit).

Progressive build of torque from reasonably low revs, with a consistant increase in power to the red line (and beyond ideally ).

Of the petrols I've driven my old mk2 Astra 1.6 8v came very close to that description! Remarkably torquey and had a good smooth power delivery, was just a bit out of steam as it approached the red line.

Of diesels, my Fabia 1.9TDi was leagues ahead of my Octy's PD140 engine, in everything other than the top 500rpm really. The PD140 just has too much lag and no power at all below 2000rpm. Have to drive it more like a petrol when trying to get power out of it!