driving downhill - fuel consumption

In message , PCPaul writes

Shouldn't do it though.. It can be damaging to the cat etc...

Because if you suddenly need drive, you ain't got it.

You'd fail a driving test.

Bump starting while in motion in a warmed up car is probably not that bad, if done skilfully. Perhaps no worse on the drivetrain than heavy braking.

I've coasted along when gradients allow, or when I see red traffic lights in the distance for the last 30 years, I've never ended up in a ditch as many here would suggest.

Many of the two-stroke cars had freewheels - Wartburgs and the like - if you went down a steep hill in gear you could seize the engine up due to lack of lubrication. (petroil system)

Julian.

They also had crap brakes & didn't go very fast. The world moves on.

I'd have thought a steering lock could cause a slilght problem?

Pretty much for the reverse reason actually.

If you have ever ridden a two stroke petroil motorcycle you will know that they over-oil on the over run. When you open the throttle after such an event, the infamous clouds of smoke ensue!

If you have ever attended a motorcycle trial, where two stroke petroil engines are commonly used, you will have seen the riders rev the nuts out of their machine after waiting their turn to start the section. This again is because whilst waiting with the engine ticking over, massive over oiling occurs which degrades the engine's performance.

Because of this, the plugs would foul if the tickover was not maintained on the over run. This produces a characteristic jerkiness that is a feature of such motorcycles, but would be uncomfortably unacceptable in a larger vehicle.

Chris

Would be the wrong answer.

Overrun down a long downhill section with a closed throttle (ie very little petrol/oil admitted to engine) with high engine revs (wheels driving engine) then lack of lubrication must ensue. We're not talking little motorbikes that overrun for a few seconds as they approach a bend on a circuit or tickover in the paddocks where the low revs allow oil to accumulate in the crankcase.

You need to give the matter more thought.

Julian.

Twit, I think we all know that. I wish you would do something similar!

I think he's already passed one, dont you?

Take your foot off the clutch?

Quite. You are only doing this if you can see you will not need to brake in the near future, so the chance of anything unexpected happening is slim, and if something does happen the chance of the correct responce NOT being emergency braking is slim. I really do not see the risk here.

I've had 50 years of tinkering with two strokes, including building and maintaining motocross engines, and working on two strokes in four wheeled vehicles; I've thought about them more than I need to thanks.

Chris

In that case, he's incorrect when he says he's *always* coasted...

Chris

The UK isn't a state in the USA, it's more than possible that the Jeep system isn't fitted to the vehicles sold in those states.

Considering the way they deliver lubrication to the engine, where is the extra oil coming from?

True enough, how would they legislate against someone moving a vehicle over a border, I wonder?

Fairly easily, they have limits on axle spacing that varies from state to state & you have to move the axles on semis when you cross the border.

You are obviously one of those dumbasses that knows better than anyone else - or indeed the manufacturers themselves!

From

Julian.