7 replies to this topic

[yorkshirechris]

I've never been taught how to use the Choke properly... but here's when and how I'm using it...

First thing on a morning I usually need to pull out the choke about halfway to start the car first time, and as it never stays out (not even if i twist it) I put a clothes peg around the stick to act as a spacer and keep it out slightly... Generally I keep it there for the whole 7 mile round trip, and often do the same on an evening when I pick her up.

If I have the choke out, even halfway, constantly, will it eat up more petrol than normal? If we're going on a long journey (I'd consider long to be more than 10 miles - something we don't do frequently) I'd push the choke in after about 10-15 mins of driving when the engine has warmed up... but on the short daily journeys that I make I keep the choke out because it gives me better acceleration meaning I can usually get to work on time after I've dropped the other half off

Am I using it efficiently or should I give it less choke & push it in when the engine's warmed up to save on fuel? As a guide we're putting in about £10-12 a week and we travel probably.. let me add it up... between 40 and 50 miles a week urban driving?

Cheers

[day101]

I thought a choke is used when the engine is cold to help it start, once the engine is warm you put the choke in, if you leave it out i think it can flood the engine because i have done it before.

[yorkshirechris]

I thought a choke is used when the engine is cold to help it start, once the engine is warm you put the choke in, if you leave it out i think it can flood the engine because i have done it before.

What would happen if the engine got flooded?

[Dan]

Over use of the choke results in a rich mixture. This acts to strip the oil off the cylinder walls and can seriously reduce the engine's lifespan.

In theory you are supposed to pull the choke fully on to start the engine and then push it fully back home immediately the engine is running. I have never had a Mini that worked like this and I suspect it's because of the design of the SU carb.

On an SU the first 1/4" of choke travel is simply used to raise the idle speed, it does nothing to the mixture. This is the portion that it is fine to use as long as you want. All it does is give a fast idle and keep the car running while your foot is off the gas as the engine comes up to temperature. It's won't seriously affect the fuel consumption or the engine. All the rest of the choke travel alters the mixture strength, this section of the choke control is only to be used for starting the engine or in really cold conditions when the air is much more dense than the carb and inlet system can normally cope with.

If you cannot run your car, in mid summer without using a considerable amount of choke then it is seriously out of tune. It should not be needed. A clothes peg (it is traditional in a Mini to use such a device but I'm sure there's a better technical name for it that will embarrass you less) is OK for staring but as soon as the gauge starts to register a temperature it is too thick. It is not simply using fast idle if there is a clothes peg (mixture control manual adjustment limiting device) fitted.

[yorkshirechris]

Over use of the choke results in a rich mixture. This acts to strip the oil off the cylinder walls and can seriously reduce the engine's lifespan.

In theory you are supposed to pull the choke fully on to start the engine and then push it fully back home immediately the engine is running. I have never had a Mini that worked like this and I suspect it's because of the design of the SU carb.

On an SU the first 1/4" of choke travel is simply used to raise the idle speed, it does nothing to the mixture. This is the portion that it is fine to use as long as you want. All it does is give a fast idle and keep the car running while your foot is off the gas as the engine comes up to temperature. It's won't seriously affect the fuel consumption or the engine. All the rest of the choke travel alters the mixture strength, this section of the choke control is only to be used for starting the engine or in really cold conditions when the air is much more dense than the carb and inlet system can normally cope with.

If you cannot run your car, in mid summer without using a considerable amount of choke then it is seriously out of tune. It should not be needed. A clothes peg (it is traditional in a Mini to use such a device but I'm sure there's a better technical name for it that will embarrass you less) is OK for staring but as soon as the gauge starts to register a temperature it is too thick. It is not simply using fast idle if there is a clothes peg (mixture control manual adjustment limiting device) fitted.

Dan,

I can run the car, it's just early on a morning (7am ish) it makes it a LOT easier to drive with the choke out for the first 5-10 minutes at least. The engine was only tuned a month or so ago and it was fully serviced etc. I'll start just using the choke to start it and maybe just let the engine run for about 5 minutes for it to warm up a bit before I drive off, do you think this is a better idea than driving for 5-10mins with the choke out?

Like the new technical term (mixture control manual adjustment limiting device), LOL. Think I'll start using that when anyone asks what it's for

Cheers

[yorkshirechris]

Oh and also the first 1/4" of the choke doesn't really do anything to be honest, I don't think the handle actually starts to pull on the choke cable until about 1/4" - it only makes a difference to the revs when I pull out the choke handle, and I can see the silve metal rod as opposed to the black plastic covering. Will this make a difference to the 1.4" rule?

[Dan]

Yes, definitely. There's too much slack in the choke cable. I wouldn't adjust it until you get a new cable though because the slack is allowing you to use the specialist device without overfuelling as much. It should be the black section of the cable that only adjusts idle speed.

It is better for the engine to warm it up by driving it than by leaving it idling, it will warm up much faster when loaded. Don't worry too much, just don't leave loads of choke on for too long.

[yorkshirechris]

Yes, definitely. There's too much slack in the choke cable. I wouldn't adjust it until you get a new cable though because the slack is allowing you to use the specialist device without overfuelling as much. It should be the black section of the cable that only adjusts idle speed.

It is better for the engine to warm it up by driving it than by leaving it idling, it will warm up much faster when loaded. Don't worry too much, just don't leave loads of choke on for too long.

Will I need a new choke cable then? And are they easy for the novice to install or better left to a garage, and how much are they with fitting usually?