TCS Choke / Starting Mechanism

[3929R]

This question is for my federal TCS with Strombergs.
I believe Trevor previously commented that he disconnected his choke cable because he never used it, even for cold starts.  I used to use my choke for all cold starts and some not so cold starts.  After replacing the diaphragms in my carbs I think I've flooded the car two or three times by using the choke.  Now I'm not using it at all. 
So do you use the choke to the start the car? and when?

Thanks,
Mark

[jbcollier]

Do you still have the extra throttle plates and tubes hooked up?

Where do you live?  As in, what's "cold" for you?

[pboedker]

My Federal TCS had the crossover pipes removed by the PO. The 'choke' cable was changed to work on both carbs. In the beginning of my ownership, I rarely used the starter mechanism. But I only drive in the 3 warmest seasons, i.e. 5-25°C where I live.

After a rebuild of the carbs (needles, tubes and diaphragms) I had the car on a dynomometer, and the engine now runs much stronger and (they told me) not so rich as it apparently did before. But now I have to use the starter mechanism almost every time. Full pull when engine is cold going down to no pull when the engine has just been started and is warm.

I guess what I'm trying to say is, that if the carbs are adjusted on the rich side, the starter mechanism is not much needed.

[3929R]

My cross over tubes are long gone.  I'm not sure what "extra throttle plates" are?  I'm in Salt Lake City, Utah, USA.  We've been experiencing spring since early February (not normal).  I think it was maybe 40s or 50sF/ (~5 to 11C) when I think I flooded it by using the choke.

Maybe it is running rich?  I have been wondering, previously the car was run at sea level but here we are about 4,400 feet/ 1350 meters.  Is that enough elevation to make much difference?  I'm guessing no but am unsure.


So I take it choke = starting mechanism? Does "flooded" have a translation?

[jbcollier]

Going to 4000 feet would definitely make it rich.  If your shop dialled in the Strombergs then you would certainly need to use the "choke" to start it in cooler temps.  If you are also occasionally flooding it, then adjust the "chokes" so they don't come fully on (older Strombergs actually had a winter/summer setting on how far the "choke" lever would travel).  Keep an eye on your temp gauge, Lotus twin-cams like to run a wee bit fatter mix than normal.

[jbcollier]

... and, if it will start without the "choke", you shouldn't use it.  Error on the side of caution, and try without first.  Pumping the throttle while cranking allows the Strombergs to simulate having an accelerator pump.

[Roger]

I have converted my TC to (almost) UK specification for S4 Elans, so no crossover pipes, no vacuum retard, and a high-level balance pipe inlet manifold. The choke cable is connected to the front carburetter only; I tried connecting to the rear as well, but the pull was too heavy. I need choke to start from cold, even Texas summer cold, but it can be pushed in within half a minute or so.

I don't think pumping the throttle on Stromberg cars achieves anything useful other than ankle exercise. I am supported in this view by Lotus themselves, who say:
"Zenith-Stromberg carburetters are not fitted with accelerator pumps, hence pumping the accelerator pedal will not aid starting.
Pumping the pedal, particularly with the choke out, will in fact cancel the action of the choke."

YMMV

[jbcollier]

True that opening the throttle will cancel the enrichment circuit so you shouldn't pump if you are using the "choke".  However, pumping while cranking with no "choke" will give "bursts" of a richer mixture.  The carb piston in both the SU and Stromberg carbs is restricted in its movement by the dampening oil.  Restricting the movement of the piston provides the same enrichment as an accelerator pump, albeit only while the engine is turning.  Try it, it works, been doing it for, Sweet Mother of Pearl, 35 years now.

[Roger]

Utterly unanswerable.