Just wondering what you guys do with the choke on a stripped down nikki? My car is stock (at the moment); rebuilding the carb to get it drivable, but have deleted the rats nest, emissions related stuff and most likely will remove the cruise control. Now I'm down to setting up the choke on the carb but can't find any info as to why keep it or not? On one hand it has function and purpose but on the other hand it is restricting the carb (somewhat). Sounds like people will tune the carb so it's not necessary to choke on a cold start. To me it makes sense to keep it AND get rid of it, but want to hear others opinions and what you've done for your vehicle.....

Now, I live in phoenix arizona which at the moment it's 112° out. Phoenix is about 1,100ft in elevation and winter here is 50 degrees at its coldest (during the day). Not sure if these are important factors or not for the choke but I thought I'd leave the info for the climate I live in....

 

My car starts just fine with two pumps of the pedal and then cranking. This is what most people do who have deleted the choke.

Personally, I would like to get my choke assembly working because I'm a little annoyed having to baby the throttle until it warms up enough to run on it's own.

There is a bit of performance to be gained with the butterfly and shaft removed. Some people just remove the butterfly, so they can utilize the "fast-idle" part of the assembly, which is all I really want, as well.

 

Okay, when your engine is warmed up the air/fuel feeding into the rotors (or piston cylinders) is vaporized and ready to burn. But when the engine is cold (or cool) the fuel doesn't vaporize well in the intake, and this makes a lot of gas vapor stick to the cool aluminum of the intake runners. Because a portion of the gas is liquifying and sticking to the walls of the intake tract, the fuel system (carb or efi) has to richen the mix, so that the air & fuel vapor entering the rotor housings is rich enough for combustion. The normal A/F ratio that your jets deliver wouldn't be rich enough, because 1/4 of it was sticking to the cool intake walls.

If you remove your choke, or get a carb without a choke, it makes the start-up mix too lean because it's lost it's ability to richen the mix on cold start. In a warm climate, like Arizona in the spring and summer, you'll probably be okay. In the winter (50 F) it will get harder to start, and you'll need to get the hang of feathering the gas pedal untill it's warmed up. This is the same hassle Webber guys have to deal with. In the Northern States in fall and winter, it would be very hard to start in winter.

Racers don't care too much about this, because the 1-2 hp gain is worth the hard starting issues for how little they drive it. But on a street car you might regret it. Others are going to chime in and tell you chokes are useless and over-rated. But look at their Location's. They will all be dessert guys or Florida guys. Very few cold-state guys will recommend going chokeless if you like to drive in early Spring and late Fall. Or Winter.

Note - All EFI systems have a cold-start enrichment. Sensors tell the system how cold the engine is and the computer richens the fuel mix until it's warm enough for the normal ratios. The carb uses the mechanical choke to do this same thing (in a dumb, mechanical way).

So, long story short..... In the summer your car will take a few more minutes to warm up and run smooth. In the Winter your car will run rough for 5 or 10 minutes longer than usual, every time you start it, until the intake manifold gets warm. Basically you're trading off driveability for a miniscule power increase that you probably won't feel.

 

Thanks for that!

 

Remove it and instaed hook the choke cable to the fast idle mechanism only. The fast idle can be set when cold so it doesn't stall out until warmed up and the choke cable mechanism will pull it off once it gets warm. Thats how I have mine setup here in NC. Works fine for our winters here.

 

i'm in California, and i don't use the choke much, i imagine in AZ you could get by without it at all. i've always had a couple of blocks before i get to the main road, so i can warm it up for ~30 seconds, and then i get ~2 blocks at ~2500rpm, and then its fine

 

Never used the choke, not even in a New Jersey winter. I have poured methanol (Heet yellow) straight down the carb when it won't start.

And nice explanation Maxwedge !

 

Could you post or pm me a pic of ur linkage if possible??

 

So this is a pic from rear of the carb. The top long arm is hooked to the fast idle cam and the choke cable goes into it. When you pull the choke it opens the primaries a bit to give you a higher idle. Hope this helps.

 

ahhhhhh I see now!! That's nifty, I am definitely going to try that!

 

The choke on my car was removed before I got the car, with the choke linkage setup for high idle. I live in Saskatchewan, the winters get down to -30°C every year, and -40° occasionally.

I don't drive my car in the the winter. If I do need to start it in the cold, I need to pump the gas 5-10 times, turn it over until it catches, attempt to rev the engine to about 2000 rpm and set the high idle. Repeat until it stays running. Most of the time it'll stall on the first and second attempts.

If you plan to run your car below freezing, I wouldn't remove the choke. It's the equivalent of running your engine super lean until its warmed up. Above freezing, it probably will warm up quick enough that you won't notice.