PhilipGB

You're confusing consumption with efficiency. At a given rpm the engine won't be using significantly different amounts of fuel to any other contemporary engine, in fact I'd wager less thanks to the variable valve timing and light weight internals.

But at a given rpm it's not traveling as fast as most cars because the gearing is designed for speed not economy. Add to that the losses from being rwd rather than fwd and fairly wide high grip tyres and that's where you're low mpg comes from. The same things that make an engine economical make it fast. Honda built an efficient engine but that is also capable of burning a lot of fuel to give a lot of performance when needed.

Dembo

Energy only comes from consuming petrol, so they have to be the same thing. And all wasted energy ends up as heat; so if one car produces more heat than another then it can only be because it's using more fuel. There's nowhere else for the heat to come from.

I don't see the S is any different to any other car in this regard, but if it is, it must be down to the thermostat, the heater matrix, and the mass of the engine. Diesel engines made from the kind of wrought iron they used to build ships out of (not really) weigh a tonne and will take longer to heat up.

PhilipGB

Consumption and efficiency are two entirely different matters though. An Arctic explorer consumes 4 times as many calories a day than a normal person. Their metabolism isn't less efficient, they are just doing more work.

My point is the S2000 doesn't produce proportionately more heat from it's consumption than another engine thus it's efficiency is no less. The engine being less efficient would counter it's purpose in making power which is why it uses lightweight internals and low friction synthetic oil to make it more efficient and thus more powerful. It can consume more though which means it proportionately creates more heat to dissipate. But that only applies when pushing the engine hard. Even the initial start up and pootling along in commuting traffic see's the heater act quicker and hotter than a typical car.

A typical car doesn't produce hot air from it's vents that is painfully hot like the S2000, you still wouldn't touch it's engine when it's warmed up though so there is a greater delta between the vent heat and engine heat on a normal car.

And iron is not as good a conductor of heat as the aluminium used in the S2000 block, so there is more resistance conducting that wasted heat energy from the combustion chamber to the coolant.

954chris

Could it be a Japanese car thing? I was surprised how quickly the warm air comes through - usually before the heated seats get hot - but its not as quick as a friends Toyota Previa people carrier, thats almost instant even in frosty conditions

CHIPPO

Now i thought the reason Derv engines take longer to warm up was due to the calorific value of derv and the efficient way in which it burns , also most derv engines are long stroke so making the most of each bang , whereas the F20C is an over square short stroke engine in which the expansion of gases is not fully utilized making it less efficient, albeit powerful at high revs .

There are plenty of Ali block derv engines , i would guess most small ones now are.

Dembo

Because he's doing more work. Two different cars idling at rest, or trundling along at 30mph are doing the same work. If one's using double the petrol to do the same thing, then one has both double the consumption and half the efficiency. Same thing.

Which is down to the size of the heater matrix. All cars run at more or less the same temperature - i.e. a bit less than the boiling point of water. How hot the air gets therefore only depends on the heater matrix.

I assume you mean "more resistance to conducting that wasted heat" - so yes, it'll take even longer to warm up.

PhilipGB

The lack of efficiency though is in the gearing not the engine. The S2000's ratios are close which is great for acceleration but not economy.

If I trunlde at 30mph in 6th gear in the S2000 which it is very capable of doing, I probably have the same power/torque available as my mothers 1.6 Focus does in 4th, and any difference in fuel economy can be attributed to transmission losses from being RWD and the wider stickier tyres not the engines lack of efficiency.

But we don't drive these cars like that because it's not fun

CHIPPO

30 mph in 6th means the engine is, or about to "labour" not good for it especially the big ends and mains , its needs to be spinning , now correct me if i am wrong but the old grey cells seem to remember Mr Honda saying this in the handbook , nothing under 2000rpm i think

Si2k

It warms up fast as the heater is on the coolant loop separate to the rad and contains a small mass of water to heat.

Also the cabin is tiny.

The gfs 2.2D civic takes forever to warm up. This is usual on diesels though as. They are thermally more efficient and less heat makes it to the coolant per g of fuel burnt. This is an Ali block too

cheshire_carper

As said, diesels are terrible. They should have an electric heater to 'help' it in the early stages then switch it off when the main is warmed.