OT: Question on diesel engines

Yes, that's pretty much it. More fuel in = bigger bang = goes faster.

There's a little more complication on modern engines - the extra fuel causes more exhaust, which makes the turbo spin faster, so more air gets pushed in, but that just means more fuel can be injected and burned.

For a petrol, opening the throttle lets more fuel/air mix into the engine, hence bigger bang, etc. The throttle is so called because it restricts the amount of air going in.

(if it's a direct injection petrol, it's just letting more air in, and the computer will then open the injectors the correct amount to get the right mix)

My now nearly 14 year old injected petrol car is basically fly by wire. The computer just knows the position of the accelerator pedal.

It'll still have a throttle to meter the air as well as fuel.

It almost certainly still has a throttle body with the throttle operated by a servo motor - rather than cable.

I think that is about it.

If its a turbo there may be some other s*it going on.

You increase air AND fuel

Interesting. So with diesel you just squirt more fuel in and the air volume looks after itself, then!

Usually yes, which is why you can have problems if the engine starts to burn its own lubricating oil, there is nothing to stop it carrying on at high speed except detonation or seizure. The only way to stop it is to plug the air intake with something solid and you may only have moments to do so, while the risk of death by being hit by engine parts is very real.

Yes. The air is always 'as much as we can get' - the fuel however is burnt in a small area round the injector where it's rich enough, and the overall mixture is always way too lean to really burn the air completely (is that stoichiometric?). That's why diesels end up making NOx, because there is still plenty of oxygen in the air to oxidise nitrogen with.

Or letting in the clutch and braking it to a stop...

The only way to stop it is to

Something may *SNAP* if you do that, but it'll doubtless be cheaper than a new engine.

High gear as you can get will strain almost nothing. You are almost braking the engine direct...

It might be better than driving under the back of a lorry as somebody did near here - according to a report of an inquest.

You're more likely to sheer the teeth of that top gear, though, and still have a racing engine to contend with. Reverse might be best.

AIUI putting it in top, dropping the clutch and leaning on the brakes is worth a go.

Or you can feed it from a CO2 extinguisher if you have one handy!

Andy

That's a good aspect of the Land Rover Defender design: you have access to the air intake without having to open the bonnet even, so you don't have to risk life and limb in the process. If you don't have a fire extinguisher you can just block the air intake with the palm of your hand.