TheSamba.com Forums
 
  View original topic: To choke or not to choke.....that is my question Page: 1, 2  Next
jimdickerson77 Wed Oct 22, 2014 12:56 pm

I apologize if this is listed elsewhere. my search skills on this site are awful. ok...im running a weber clone progressive on my type 4. all summer i ran it in the cali desert with the choke fixed "wide open" it ran fine but with a slight bog and fall on its face when i put the pedal to the floor. at that point i averaged 16 mpg. i came home to southern oregon a month ago. i cleaned my carb and hooked my choke up and adjusted it to where it fires right up on a cold morning. It now accelerates SO much better. the bog/fall on its face is gone :) it seems to be such a smoother running bus bus until i averaged my MPG it has dropped to around 10 MPG. i cant understand why. My carb is properly jetted air/fuel damn near spot on as well as my idle screw ( idles at 1k ) why is my mileage suffering so badly ??

aeromech Wed Oct 22, 2014 1:06 pm

once warmed up can you verify that the choke is fully open?

Danwvw Wed Oct 22, 2014 1:19 pm

It should be getting around 20 22 mpg on the highway! The type 4 engines may do a little worse. I used to drive my 1971 VW bus about 10 miles to work everyday to Ashland and it was getting 21 MPG but then the Milage dropped to 11 mpgs so on inspection I found the heater element in the choke had burned out. Replaced the element and it went right back to 21 mpg!
But if your running IDF's? (Sounds like the jetting or tune may be a little off!)I would try to get along without chokes! Rebuilt the engine in the 1971 Bus and installed Dual Dellortos with no chokes and am doing fine and still getting 19-22 MPG Daily driving.

Wildthings Wed Oct 22, 2014 1:48 pm

You have to set the choke on the lean side to get it to work well with a Type 4. This may cause problems with a bog after start up.

The problem is is that the carb body gets so cold without any kind of manifold heat or preheat that the choke may no open fully and may actually start closing again as the engine is run for an extended time at highway speeds.

I use both the stock 72-74 preheat stove and have some manifold heat and still must set my choke to the lean side to get it to open quickly and stay open.

SGKent Wed Oct 22, 2014 1:50 pm

if you told me it was getting 16 - 18 MPH I would consent it is tuned properly. Most engines won't start cold well without a choke when they are tuned properly unless you pump the heck out of them and then manually hold the throttle open until the engine warms up a little. Without a choke they will also puke terribly until the engine is warm. You have enriched the mixture until it will run cold. It is wasting fuel, washing oil off the cylinder walls leading to premature wear, and costing you horsepower.

Joey Wed Oct 22, 2014 2:02 pm

I don't think the dis-armed choke had anything to do with the slight bog. After a few minutes a properly adjusted choke would of been wide open as if it was dis-armed so the bog was carb adjustment related.

As for your poor mpgs... is your choke fully opening once warmed up?

jimdickerson77 Wed Oct 22, 2014 5:20 pm

aeromech wrote: once warmed up can you verify that the choke is fully open?

From what i see it appears the choke is not fully opening. Its only opening a fraction. but this seems to be what is the cause for its smoother no lag acceleration. When i view the carb from above i see the choke plates open more as throttle is applied. but yet if i manually hold the choke plate wide open and accelerate the lag comes back. :?:

jimdickerson77 Wed Oct 22, 2014 5:25 pm

SGKent wrote: if you told me it was getting 16 - 18 MPH I would consent it is tuned properly. Most engines won't start cold well without a choke when they are tuned properly unless you pump the heck out of them and then manually hold the throttle open until the engine warms up a little. Without a choke they will also puke terribly until the engine is warm. You have enriched the mixture until it will run cold. It is wasting fuel, washing oil off the cylinder walls leading to premature wear, and costing you horsepower.

yea i must have a problem. Because even with my choke managing to fire my engine on a cold morning i still have to manually hold the throttle open (anti theft device propped on my gas pedal)

aeromech Wed Oct 22, 2014 5:42 pm

I'm thinking that your choke being closed is causing the poor gas mileage. The fact that it runs better means it's jetted too lean or you have a vacuum leak.

jimdickerson77 Wed Oct 22, 2014 6:24 pm

aeromech wrote: I'm thinking that your choke being closed is causing the poor gas mileage. The fact that it runs better means it's jetted too lean or you have a vacuum leak.

You are probably correct. As far as jetted too lean, are you referring to the idle jet? My mixture screw sits at 2 turns out and i thought that would mean the main jet is sized correctly ?

aeromech Wed Oct 22, 2014 6:43 pm

Think about it. How much gas is being used by the idle circuit (jet)? What matters for fuel economy is the main jets. The way to check that without expensive tools is to do a 10 mile freeway run and then immediately shut down and check the plugs for color

The idle mixture adjustment controls how smoothly the engine accelerates from idle to part power.

SGKent Wed Oct 22, 2014 6:48 pm

you guys crack me up. Doesn't anyone here except really old timers know how to clean, adjust and tune carbs? Reading the comments is like watching first time fathers to be explain to each other how to handle a baby crying all night.

When a carb is adjusted right it will run well 99 - 100% of the time. The only carbs I have seen not do that are the original carbs on 1967 California cars which was a transition year to smog here.

Wildthings Wed Oct 22, 2014 8:55 pm

aeromech wrote: Think about it. How much gas is being used by the idle circuit (jet)? What matters for fuel economy is the main jets. The way to check that without expensive tools is to do a 10 mile freeway run and then immediately shut down and check the plugs for color

The idle mixture adjustment controls how smoothly the engine accelerates from idle to part power.

On a progressive you are on to the main jet almost immediately as you begin to open the throttle. The bog is the delay in the fuel flow as the system transitions to the mains, with for a 1/2 second or more the engine needing more fuel than the combined main and accelerator pump flow. It takes a bit for the power valve to open and enrichen the mixture and from then on the system tends to run overly rich.

Combine this rich running with the lack of carburetor heat and the gas mileage is apt to s*ck.

jimdickerson77 Wed Oct 22, 2014 9:30 pm

Wildthings wrote: aeromech wrote: Think about it. How much gas is being used by the idle circuit (jet)? What matters for fuel economy is the main jets. The way to check that without expensive tools is to do a 10 mile freeway run and then immediately shut down and check the plugs for color

The idle mixture adjustment controls how smoothly the engine accelerates from idle to part power.

On a progressive you are on to the main jet almost immediately as you begin to open the throttle. The bog is the delay in the fuel flow as the system transitions to the mains, with for a 1/2 second or more the engine needing more fuel than the combined main and accelerator pump flow. It takes a bit for the power valve to open and enrichen the mixture and from then on the system tends to run overly rich.

Combine this rich running with the lack of carburetor heat and the gas mileage is apt to s*ck.

working on the heating issue is simple enough but id love to hear your recommendations for fixing this rich running problem?

Wildthings Wed Oct 22, 2014 11:10 pm

My belief is that both the notorious stumble and rich running of the progressive are tied to the power valve. The power valve isn't necessarily open when you need it coming off idle and are beginning to put a goodly load on the engine, but is often open at cruise when you do not need it. I have posted about this in the Progressives Suck thread.

http://www.thesamba.com/vw/forum/viewtopic.php?t=217070

jimdickerson77 Thu Oct 23, 2014 2:37 pm

Wildthings wrote: My belief is that both the notorious stumble and rich running of the progressive are tied to the power valve. The power valve isn't necessarily open when you need it coming off idle and are beginning to put a goodly load on the engine, but is often open at cruise when you do not need it. I have posted about this in the Progressives Suck thread.

http://www.thesamba.com/vw/forum/viewtopic.php?t=217070

Thank you.

SGKent Thu Oct 23, 2014 3:00 pm

SOME progressives have a well that the emulsion tubes sit in. On the side of the throttle bore below the venturi there are a series of holes.

Blow each out with compressed air from inside the next time you have the progressive completely apart. Have the emulsion tubes out when you do this. Blow them out to be sure the passages are open.

When done before assembling hold the body up to the light and adjust the butterflies until they are as even as possible when closed. Light should look as even as possible. Do not take the screws all the way out as they are usually staked or peened.

With the throttle plates adjusted to be closed to the factory idle settings, see how where the throttle plates sit in comparison to the highest transition hole. The plate should be even or close that hole, and only expose it as the throttle is gently opened. The farther the throttle plate(s) must move to expose that first hole is a period where the throttle will be lean. I try to set it up so that the first hole is immediately exposed when the throttle is cracked open. This way the mixture will not go lean. If the holes are exposed in ANY way at idle, the wells are partially or fully drained, and one must pull additional fuel from the mains instead of the reservoir(s) created to keep that bog away.

Also make sure that the mechanical ignition timing advances immediately when the engine RPM begins to rise.

Yarkle Wed Sep 12, 2018 6:12 pm

For those carbs that dont come with a choke, like IDFs or ICTs, would there be any benefit (or way) to fabricate the stock solex electric choke elements so they warm up the carbs when its cold? I dunno, maybe JB weld them to the bottom of the air cleaners?

Has anyone already tried this?

I dunno, or maybe something like this, stick the little electric disc that comes from the coil (IIRC) onto where ive circled n yellow.


busdaddy Wed Sep 12, 2018 6:40 pm

Yarkle wrote: For those carbs that dont come with a choke, like IDFs or ICTs, would there be any benefit (or way) to fabricate the stock solex electric choke elements so they warm up the carbs when its cold? I dunno, maybe JB weld them to the bottom of the air cleaners?

Has anyone already tried this?

I dunno, or maybe something like this, stick the little electric disc that comes from the coil (IIRC) onto where ive circled n yellow.

[pic]
Nope, it won't help at all. Buy the enrichment valves and install a cable in the cab to operate them, there's no other alternative, sorry.

Yarkle Wed Sep 12, 2018 7:17 pm

Bummer. from what lore ive poured over, it looks like most people who have IDFs and ICT's either block that part off if it had it, or the newer ones may not even be machined for it

http://shoptalkforums.com/viewtopic.php?t=145329

https://www.thesamba.com/vw/forum/archive/index.php/o-t--t-73306--.html

John at Aircooled claims that you can start an IDF with no problem at 40 below.

My 72 setup hit a snag, so im considering the IDFs.

I guess worst case i can always just stick a droplight in the engine bay like the old timers did



Powered by phpBB © 2001, 2005 phpBB Group