TheSamba.com :: View topic - Single, double barrel, and progressive carbs

Tue Jul 10, 2012 4:37 pm

Well here is my question.

How does the power output to gas mileage differ between these?

What made me think of this is I'm going to upgrade my carb. (not going dual, too much power on an old engine).
But here is the thing, lets say a single carb has an opening of 1. and the double barrel and progressive have two openings, each the size of 1.

So you have your single carb, you open it all the way. Now you have an opening of 1. On your double you open it half way, and you also get an opening of 1. Then on the progressive you open 1 barrel all the way, and you have an opening of 1.
Then you disregard the single barrel because it is small. Now progressive and double barrel with openings of 1. If you open the double all the way, you have an opening of 2. If you open the progressive all the way, you have an opening of 2.

Hows all this go together? If you want better gas mileage just dont open your double barrel all the way? if you want more power, just stomp on the throttle to get the same result? i dont get it.

Tue Jul 10, 2012 4:40 pm

:shock:

Tue Jul 10, 2012 4:45 pm

I think you forgot to carry a 1

Tue Jul 10, 2012 6:39 pm

All the 1s have been accounted for lol

Tue Jul 10, 2012 11:13 pm

yes your right.

With a stock carb you have a single venturi (1)

with a progressive you have a first venturi (1) and a secondary (1)

So you get economy driving half throttle on (1) and extra power when you open both (2)

Its not a massive upgrade in power on a stock engine however.

Wed Jul 11, 2012 8:16 am

krusher wrote: yes your right.

With a stock carb you have a single venturi (1)

with a progressive you have a first venturi (1) and a secondary (1)

So you get economy driving half throttle on (1) and extra power when you open both (2)

Its not a massive upgrade in power on a stock engine however.

Ah, kk.

I have a 1776cc engine, and currently it is being choked to death with a 34pict1. I was thinking about upgrading to a progressive, or a maybe 40idf weber?

Thoughts?

Wed Jul 11, 2012 9:31 am

Save your pennies for a while and put on a properly jetted set of Kads (budget choice) or Webers. Buy them from someone who will jet them to match your engine's configuration.

I know there are lots of folKs that have got single carb upgrades to work, but
IMHO it's always a compromise.

Wed Jul 11, 2012 9:39 am

theredbarn wrote: Save your pennies for a while and put on a properly jetted set of Kads (budget choice) or Webers. Buy them from someone who will jet them to match your engine's configuration.

I know there are lots of folKs that have got single carb upgrades to work, but
IMHO it's always a compromise.

I don't know of any shops around the L.A area that sell more performance carbs, let alone jet them. I only know of 2 shops and they are stock items mostly.

But sheeeeesh. I do have to save up a few more pretty pennies. I was hoping I could get myself a new larger carb/manifold for ~$400.

But a weber and kadron kits are going to run me more like $600 bucks.

Looks like its time to get some more scholarships lol.

Wed Jul 11, 2012 10:10 am

So far the types I'm looking at are these.

http://www.mooreparts.com/store/product/2803/KAD040/

http://www.jbugs.com/product/43-7316.html?Category_Code=vw-weber-carburetors-kits

http://www.jbugs.com/product/43-0622.html?Category_Code=vw-weber-carburetors-kits

http://www.jbugs.com/product/43-7315.html?Category_Code=vw-weber-carburetors-kits

Wed Jul 11, 2012 10:58 am

Looks like you need to read this article:

http://www.aircooled.net/vw-carburetor-options-selection-101/

IMO, for your 1776, the best choices would be dual Dellorto 36 DRLAs or dual Weber 40 IDFs. Neither is inexpensive, but sometimes you have to pay to get the best.

Wed Jul 11, 2012 11:14 am

I would have to agree with sactojesse. You can get up to 35mpg's if you drive it correctly. In the lower end they tend to increase the engine's torque but in the higher revs you drop off incredibly. A good set of dual 40 IDF's will open up your 1776 and if you drive the car moderately, you can get better than 35mpg's with increase in power and top end.

Wed Jul 11, 2012 11:21 am

Thats a very good article. I'm enjoying reading this.

Wed Jul 11, 2012 11:29 am

oolcu812 wrote: theredbarn wrote: Save your pennies for a while and put on a properly jetted set of Kads (budget choice) or Webers. Buy them from someone who will jet them to match your engine's configuration.

I know there are lots of folKs that have got single carb upgrades to work, but
IMHO it's always a compromise.

I don't know of any shops around the L.A area that sell more performance carbs, let alone jet them. I only know of 2 shops and they are stock items mostly.

But sheeeeesh. I do have to save up a few more pretty pennies. I was hoping I could get myself a new larger carb/manifold for ~$400.

But a weber and kadron kits are going to run me more like $600 bucks.

Looks like its time to get some more scholarships lol.

umm a kadron kit doesn't have to cost $600..

here is a nice kit that i believe would be a nice match for your engine...

http://www.shop.kaddieshack.com/TURN-KEY-Kaddie-Sh...-KAD-1.htm

$450.... but would advise the upgrade on the linkage...

Wed Jul 11, 2012 11:39 am

I should mention, this is currently built as a class 11 prerunner.

I am keeping all the stock parts, but as of now it is being used as a daily driver. If I ever was to race it I would revert to stock.

But it is offroad capable, and after I get a truck, it will become my toy.

Wed Jul 11, 2012 11:46 am

"Off roaders, should opt for a centermount progressive for smaller engines, and the centermount IDF/DRLA for larger. Choose the 40 IDF for <2000 cc"

Taken from the article. That seems very adequate.

Wed Jul 11, 2012 2:37 pm

as an offroader the 40 IDF will work well, just make sure you have good preheat

Wed Jul 11, 2012 2:37 pm

Get lots of heat to the manifold if you want to run a single centered 1/2 barrel carb.

Wed Jul 11, 2012 2:49 pm

What is the deal with the preheat? I recognize that it is needed to keep the gas from condensing. And you need the preheat tubes. But how do I get "better" preheat to the manifold?

I'm assuming if I got the centered double barrel kit, the manifold + preheat tubes that came with it would be good

Wed Jul 11, 2012 2:59 pm

you are assuming all intakes are the same (they are NOT). There are $)*#&)& ones, and nice ones. Most stores sell the #$)(*#&)(*& ones because customers assume they are all the same, so they buy the "inexpensive" ones (CHEAP).

If you buy a center mount, you will spend the same $ as duals. This is because the $ you save on the 2nd carb, you'll spend on modifying the exhaust to provide the PROPER pre heat to the intake. Flanges on #2 and #4 primaries are NOT GOING TO DO IT. You have to route the exit to the exhaust collector, for a good flow of hot exhaust through the system.

Wed Jul 11, 2012 3:27 pm

[email protected] wrote: you are assuming all intakes are the same (they are NOT). There are $)*#&)& ones, and nice ones. Most stores sell the #$)(*#&)(*& ones because customers assume they are all the same, so they buy the "inexpensive" ones (CHEAP).

If you buy a center mount, you will spend the same $ as duals. This is because the $ you save on the 2nd carb, you'll spend on modifying the exhaust to provide the PROPER pre heat to the intake. Flanges on #2 and #4 primaries are NOT GOING TO DO IT. You have to route the exit to the exhaust collector, for a good flow of hot exhaust through the system.

Could you perhaps provide a link on how that could be done? Or maybe go in to some more detail please.