WEBER choke type?...TURTCEL

[TURTCEL]

So I am getting ready to order my WEBER carb kit but I am unsure on which direction to go with on the choke set up. I have friends that run manual chokes set ups on their WEBER because of preference but it seems that most members here run electric.

Here is where my thought comes in. I live at 350 feet above sea level a stay at that altitude regularly, but also love to go hiking in the mountains at higher elevations. In May my wife has to drive the car to Twin Falls, Idaho to pick up the last of our belongings as well as stay for a couple week visit. Twin Falls is 4300 feet ASL and the trip there will include driving up and over a few mountain passes that are high altitude ranges. The WEBER comes jetted for altitudes ranging from sea level to 2500 feet and then you can get a re-jet kit for high altitudes ranging from 2500 to 10,000 feet ASL. What will be the symptoms and issues she could have driving the car with a carb jetted for lower altitudes? Would this be a bad thing? I want to change the carb so I can eliminate all the vacuum systems and components since I continually have issues with them and the carb. I am only getting 20 MPG and that won't cut it for her trip and our bank account.

I have heard of people installing WEBER carb and using their manual choke when driving in higher altitudes to help compensate for the leaner air. I guess they just slightly set the choke in order to richen the mixture a little so that the car doesn't run as lean. Is this something anyone else has heard of or done themselves?

I like the simplicity of the electric choke for not having to deal with a cable install but if it would help with my mountain travels to have a manual choke then I would consider it.

Peace

[irowiki]

I thought the cars naturally ran rich at high altitude (because of less air) and that was the point of the High Altitude Compensator, it provides more air to the fast/slow circuits of the stock carb at 4000 feet and above!

[TURTCEL]

That is a great point. This is why I am fishing for some extra help on my decision.

Peace

[irowiki]

I'd go automatic all the way.

[dlb]

if you are primarily using the car near sea level, i would stick with the electric choke. it is automatic and reliable which is well-suited to the majority of the time you will be using it at sea level, and it is also adjustable so you could play with it to run slightly richer when the car would be staying at higher elevations for a while. i actually doubt you would see much difference in fuel economy even without adjusting the choke but it might be a neat experiment to try.

[Petros]

I grew up with manual chokes, and just got used to them. They give you some control over the mixture from the driver's seat. Emissions regulations deleted them because if you drive with the choke on too long you waste fuel and put out a lot of pollution. It is easy to forget to push it in all the way.

the choke makes the mixture more rich, which it needs to run cold. but once warm you want a properly balanced mixture. At high altitudes there is less oxygen so you need less fuel or it runs too rich, using the choke would make it even more rich. I do not see how that can help. The HAC leans the mixture by bleeding air under the carb and it advances the spark timing (a low density charge burns slower, to have to advance the spark to keep the peak pressure at the optimum point in the piston cycle). You will not be able to lean the mixture out with a manual choke.

The only way a manual choke might be helpful is in extreme cold climates you keep the mixture rich longer and delay pushing in the choke knob until it will run without flat spots with the choke fully open.

[TURTCEL]

[quote="Petros"] At high altitudes there is less oxygen so you need less fuel or it runs too rich, using the choke would make it even more rich. I do not see how that can help. The HAC leans the mixture by bleeding air under the carb and it advances the spark timing (a low density charge burns slower, to have to advance the spark to keep the peak pressure at the optimum point in the piston cycle). You will not be able to lean the mixture out with a manual choke."

So why couldn't I drill a hole and thread a small brass nipple into my EGR block off plate and keep my HAC operable by connecting a vacuum line to it so it could still lean the fuel/air mixture at higher altitudes? It would also advance the timing slightly if still all connected right? I know the air inlet at the EGR plate is lower than the port being under the carb, could this cause the mixture not to lean properly because it isn't closer to the fuel spray?

These are the custom tricks that would be nice to figure out so that WEBER carbs can be a little more accommodating to varied driving conditions.

Peace

[dlb]

peter's right, sorry. i got mixed up about lean/rich at high altitudes.

i also wondered if the HAC could be made to work with the weber, turtcel, but it appears to work in conjunction with the EBCV so it would be necessary to retain that as well. probably not worth it.

[irowiki]

On the first gen tercel the HAC worked without the EBCV.

On the second gen it just tees into the same lines the EBCV uses, so the HAC works independently of the EBCV.

You'd probably only need to use one of the HAC lines, or maybe tee it and use both.

So you'd have one line going to the vacuum advance and 1-2 going to your EGR block.

[TURTCEL]

irowiki...I had the same thoughts as you on the HAC. I have my EBCV disconnected and everything else in that system seems to be unaffected by its removal. This could be an experiment worth trying since an EGR block off plate can easily be remade if it doesn't work out as planned.

Peace

[teranfirbt]

I drove my Weber set up for Portland (near sea level) to Texas, through Flagstaff (~8000 ft). It was pissed and ran rich, but mileage didn't really suffer.

[Petros]

it would not be difficult to rig the HAC to work with the weber, the EBCV is not necessary. You just want the bleed air to come in at the central plenum to get proper mixing. Or you could just do a manual bleed valve that you can meter the amount you lean the mixture. As for spark timing just set it at 10 or 12 deg BTDC and live with it.

Also, running premium fuel at high altitude should reduce the tendency to ping when running lean, and the extra fuel economy should more than off set the higher cost of the fuel. That is what I have found in both my built-up 3ac and the newer 4ac, spend an extra $2 on the fill up and get 30 or so more miles per tank, well worth it.