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MG MGB Technical - How much does the choke affect gas mileage?

It's been rather cold the past week here in New England. My office is less than 2 miles from my home. I drive back and forth at least 2 or 3 times a day. With the cold weather I'm barely getting the choke pushed back in before parking my 73B roadster at one place or the other.

My gas mileage (not that I'm all THAT concerned) has dropped way down. That brings up the question of just how much an engaged choke will lower your mileage. Has to be some I would think due to the enriched mixture.

Any thoughts?

Thanks,
BH
BH Davis

BH - Probably driving with an engine that is not up to operating temperature is doing as much damage to the mileage as having the choke on. I hope that on the weekends you get the car out for a good long run to get it up to temperature to drive off all the condensed moisture that has collected in the sump. Cheers - Dave
David DuBois

With an electric fan quarter of a mile is what I need in winter, may have to tweak it in traffic up to half a mile.
Of course with it costing £6 a gallon it does concern me.
c cummins

Dave,

Yes, it does get longer rides. Just during the week it gets a lot of this short stuff.

Thanks,
BH
BH Davis

By blocking off the oil cooler the engine will reach operating temperature much faster. When I installed an oil thermostat, in the lines going to the oil cooler, it cut the warm up time in half. RAY
rjm RAY

Ray,

Can you tell me more about the oil cooler thermostat? What did you use.......where did you get it?

Thanks,
BH
BH Davis

I purchased the thermostat and lines from Moss several years ago. It is listed in their catalog. RAY
rjm RAY

Choke will easily double fuel consumption, but it's OK since it will also halve engine life or worse! A good bit of the excess fuel is just going to dilution of oil. It takes about 20 minutes operation under load (not idle or traffic lights) to get engine oil/metal temps normalized at hot, and possibly much longer ('til summer!) with a cooler in cold weather. Wrap the cooler in insulation 8 months of the year.

Learn to get the car moving then push the choke in until it is just acting as fast idle, which should be the first half inch of choke travel. At anything above 20F, fast idle should be all that is required after the first mile; this will eliminate the oil dilution, and will only increase fuel consumption slightly. You can verify that the fast idle is set correctly by watching when the jets start to move as someone else pulls the choke out slowly. There should be no jet movement in the first half inch, but the idle should go up to about 13-1500.

And I just realized that you probably have HIF on 73, so can't see the jets! But you still need to ensure that the idle starts to increase as soon as the cable moves, otherwise you are moving the enrichment device without the fast idle, same as having the jets move on earlier carbs.

Where in CT? I will be up there later this week/weekend.

FRM
Fletcher R Millmore

Thanks Fletcher. That is exactly the type of info I was hoping to get.

Yes.........HIF4 carbs and I think I have them set up pretty well.

I'm in the northeast corner of CT about an hour to Boston, MA. and 20 minutes south of Worcester, MA.

Where are you going to be. It would be nice to meet.

BH Davis
BH Davis

Find a longer route to work, 2 miles each way is very bad for the car even in summer, let alone winter.
Paul Hunt 2010

BH

have you though of using a Kenlowe Hotstart ?
This may warm your engine before you start it.

More practical if you have a big garage with cheap electricity and have the time to connect/unconnect before your journeys

Dave
dave bignell

This thread was discussed between 11/05/2010 and 12/05/2010

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