Remove electric choke?

[aussiebug]

The auto choke was one of Muir's pet hates and one of the things he is completely wrong about. His book is a very good read but has to be taken with a bit of skepticism - he also likes to shine up commutator sections in the generator with emery paper...shudder. The auto choke is in fact one of the most reliable parts of the fuel system, and when set correctly it is an important part of getting the car started in cold weather, whilst not interfering with warm starts.

[Jim Ed]

I have a 1973 Beetle.
I keep my choke set with the Idle step cam at the throttle lever on the lowest step.
When it is really cold, I let it idle until the tach reads about 800 to 900 rpm which, usually takes about two to three minutes.
I can hear it now. "idling is not the way to warm it up".
But it makes it more fun to drive with it warmed up.

[aussiebug]

I can hear it now. "idling is not the way to warm it up".

OK Ed - just for the record.

VW Owner's Manuals ALL have one of two phrases...

Early manuals say
"As soon as the engine starts...you can move off at once."

Later manuals say
"Do not try to warm the engine up by letting it idle with the vehicle stationary - drive off straight away."

There are several reasons for this.

1. The choke starts to open as soon as you turn on the ignition, so if you idle the engine, the choke will be fully open before the engine has warmed up properly - so you end up driving on a cool engine without the choke - makes for stumbles, especially since the heat riser is not hot yet (see No4).
2. Driving off immediately gets heat into the engine much faster than idling it. This reduces engine wear - about 80% of engine wear happens whilst the engine is cold, so 1 minute heating time is much better for engine life than idling and taking 3-4 minutes to warm it up.
3. The cabin heater will start working much sooner, as there is much more exhaust heat in the heat exchangers.
4. The heat riser under the carb sees exhaust heat much sooner. The VW engine NEEDS heat in the heat riser to prevent icing, but more importantly to keep the fuel atomised along that long induction manifold. If that's left cold for longer, you get fuel pooling and poor mixtures going into the engine. The engine can stumble, and excess fuel droplets inside the cylinders also dilutes the oil film on the cylinder walls - increasing engine wear.

Of course the Owner's Manuals also say "do not race the engine while it is still cold". So, drive off immediately but go easy on the throttle until the engine warms up a bit. That way you get the most driveable car, heat into the cabin sooner, and a better engine life.

But it's your car Ed - you drive it how you want.

[Jim Ed]

OK. I will re-set the choke and take off as soon as possible.

[aussiebug]

OK. I will re-set the choke and take off as soon as possible.

Great Ed,

Let us know if it makes a difference in drive-ability in the first few minutes after starting.

[Jim Ed]

I plan on adjusting my choke so I can drive off right after I start it but, here is why I thought I did not need one.
I got this from an old Gene Berg Parts & Technical Manual p. 74.
But I Have To Have A Choke!
Please be clear that no car has to have a choke to start or run in any type of weather. It is a convenience to keep your car idling when cold. Few dual throat carbs that come on factory cars have a choke as they start and run fine in the coldest of weather. All it takes is a few pumps on the accelerator pedal to squirt gas directly into the port, crank the engine and it will start. If it dies repeat the procedure. Normally, when the engine is tuned properly, it will idle and run after the first or second start up. If it does not you may be jetted too lean. Chokes on the carbs cause far more fuel to be burned, can wash down the cylinder if left on too long and that could be an expensive inconvenience. For years I have removed the stock choke plate(s) from my car's carbs. This left the fast idle cam without choking the engine, causing it to burn more fuel.
Jetting Information
A simple tip on what way to go with jetting is that if it runs crisp cold and sluggish when warm it is too rich and requires a smaller main jet. If the engine stalls and has bad flat spots when cold and they do not completely go away when the engine is at normal operating temperature, the engine is too lean and requires a larger main jet, more accelerator pump, and/or a larger idle jet.

http://images.thesamba.com/vw/gallery/pix/1170792.jpg

[Marc]

It depends upon the temperature (and even the humidity) as well as the efficacy of the preheat and thermostatically-controlled air cleaner systems.
Dual-carb setups don't require manifold heat since they're short and setting right atop the heads, but when the carb is as far distant from the engine as it is on a stock single-carb ACVW preheat becomes a vital concern. Gene Berg may have spent most of his life in Orange County California, but he was originally from Renton Washington and it amazes me that he seemed to manage to forget all about the cool/damp morning conditions that we live with in much of the rest of the country for many months of the year...I'm reasonably sure that he didn't sleep in 'til noon when he lived here ...GB's jetting guidelines are as a rule on the rich side of what most folks use, but still not enough to keep a cold motor lit on a chilly morning.
Cold engines need a richer mixture and more air - it's basic physics, even modern fuel injection systems must provide additional fuel and air to keep things going from "cold-iron" conditions.
When the throttle is opened, manifold vacuum is reduced (pressure trends towards atmospheric) which can cause the fuel in the mixture to fall out of suspension and condense on the cold walls of the intake tract. This causes a momentary lean condition which may or may not be successfully overcome by the additional fuel squirted in by the accelerator pump. The condensed fuel eventually does dribble down into the engine, but in the form of large droplets which are insufficiently atomized to support full combustion - ironically, raw fuel hydrocarbons come out the tailpipe even though conditions are too lean inside the engine to burn properly.
The choke serves two functions - one is to "strangle" the incoming air supply which raises the pressure differential between the outside world and the innards of the carb, so that more fuel gets pulled through the idle circuit; the other is to hold the throttle open a bit to lessen the resistance to pulling incoming air...needed to overcome the extra friction inherent when the engine is cold and the oil is thick. Automatic chokes nearly always incorporate a vacuum-actuated "pull-off" mechanism that will drive them off even when cold which prevents excess enrichment under load.
It's a basic razor of engineering that omitted parts cannot cause failure, and cost nothing either - if the choke was truly not needed, the factory never would've provided one. IF you live in a warm enough region, and don't mind occasionally needing to "nurse" a cold engine for a bit, the choke isn't really necessary and if it should fail to open it could cause fuel to dilute the oil - but in the majority of cases (for a stock single-carb ACVW engine at least) the convenience of having one outweighs the potential liabilities. Typically, the only attention required is to reset it once in the spring and once in the fall.

[andy198712]

i was using my beetle few times a day and getting mid 20mpg (uk)

i'm running my 1200sp on crank triggered ignition via megasquirt.

this, and disabling the choke got me to high 30mpg and a best tank of 42mpg

i can post a video of my tach with a cold start, no pumps or throttle if you fancy?

my idle is 800-850rpm at 11 degrees advance. but at 500rpm my advance is 34 degrees (if i remember right) this allow for not using a choke

[Marc]

...my idle is 800-850rpm at 11 degrees advance. but at 500rpm my advance is 34 degrees (if i remember right) this allow for not using a choke

If you had a conventional ignition system I would say that this indicates that you have your vacuum-advance line connected to manifold, rather than ported vacuum - even a DVDA can't retard the timing by more than about 12° so this would have to be a result of the advance mechanism being fed the wrong signal...if the timing stayed that far advanced under load, you would be beating the top ring lands of your pistons to death, that is FAR too much advance below ~2500+ RPM. You might not hear it, but the spark knock that would be going on inside is akin to smacking them with a hammer. It may be safe if you can achieve this type of curve using the electronic controls, but I certainly wouldn't recommend it.

No way in hell could a properly adjusted and functioning choke cause a 33% reduction in fuel economy. It should be fully off within no more than 3 minutes (well, maybe a little longer in sub-0°F environs) so your driving cycle would have to be a series of 4-minute trips (with an hour or so between for things to cool back down) for the mileage to suffer that much.

High 20s/low 30s (on a 4-quart gallon) isn't remarkable at all for a stone-stock 1200, but 42 certainly warrants some bragging. If that's per Imperial (5-qt) gallon, not so much

[aussiebug]

High 20s/low 30s (on a 4-quart gallon) isn't remarkable at all for a stone-stock 1200, but 42 certainly warrants some bragging. If that's per Imperial (5-qt) gallon, not so much

Marc, I'm curious - I've never heard of a 5 quart gallon! In Aus we used the imperial system until we went metric in 1972, and our imperial gallon still had 8 pints (4 quarts) but they were bigger than yours. 1 Imp gallon is 4.55 litres where your US gallon is about 3.7 litres.

A "5 quart gallon" using US quarts would be about 4.6 litres, larger than the Imp gallon.

The definition of an Imp gallon is a volume of water (at 62f if I remember right) which weighs 10lb. I don't know how the US gal is defined.

Or is that just a local US expression to indicate the larger size of the Imperial gallon?

My bug (like all standard bugs) hold 40 litres of fuel - that's 10.6 US gals or 8.8 Imp gals.

[Ol'fogasaurus]

http://en.wikipedia.org/wiki/Gallon

per the above: 4.54609 liters (Imp gal) is equal to 1.20 US gal.

[BAJA-IT]

8 oz. to the cup, 2 cups to the pint, 2 pints to the quart, 4 quarts to the gallon=128 oz.

[Marc]

...is that just a local US expression to indicate the larger size of the Imperial gallon?...

No, just a flippant term I used in an effort to emphasize the difference between a US gallon (128 oz) and an Imperial gallon (160 oz). I'm aware that the Imperial gallon also is divided into four "quarts", but they are 20-oz quarts rather than 16-oz. Sorry if I injected confusion into the subject, I thought everyone knew these things - in the '50s, it was taught in elementary school.


A US fluid ounce is slightly larger than an Imperial fluid ounce, and the official measurement temperature is slightly different. 5 US quarts would be about 1.04 Imperial gallons.

[FJCamper]

Hi

John Muir (apparently) was against the electric VW choke because it caused so much trouble. Think way back. An owner or friend or shadetree mechanic worked on the carb, misadjusted the choke, or something went wrong with it (pick from a long list) and from that time on the car ran badly. I remember it was one of the first things I learned to look for in troubleshooting.

If the choke plate seized up in the wrong slant, you ran on part throttle. I can't remember how many carbs I saw with the choke clamp screws missing, or the choke clamp loose. Or the choke wire missing or disconnected, even grounded (!) and burned.

I'm a believer in chokes, and at one time had a nice JC Whitney cable operated choke control on my '68 1500cc Bug. I think Muir missed the simplicity of the hand choke, and was disgusted by the complexity and opportunity for trouble of the electric choke. But I'd take an electric choke any day over one of those nasty water-heated US chokes.

We VW people put up with a lot back in the day, carbon-clogged manifold heaters, rusty, snapped heater cables, no windshield defogging, but we loved them. And still do.

FJC

[Weaponer]

I put a toggle switch on my dash. When I want the choke to stay on longer, I turn the switch off. That way the heating element doesn't get electricity and open the choke sooner than the engine likes. After I drive a few miles, then I turn the switch on so electricity goes to the heating element and opens the choke. I do run an after market exhaust header with the heat riser ports cheaply positioned. Maybe if my heat riser ports ducted in like stock, I wouldn't need my toggle switch.