| Author |
Message |
Alstrup
Samba Member
Joined: July 12, 2007
Posts: 7210
Location: Videbaek Denmark
|
 Posted: Fri May 16, 2014 11:18 am Post subject: |
 |
|
Hello.
The fact that a set of dual carbs can/will improve performance on a 1600 single or dual port VW engine has been known since VW started their production, and in general way before that. Among other things it has to do with the audience that the engines/cars are built for.
Why do you guys think there are several stages of hp for a given model (non VW that is) VW was attypical because they basically kept the same engine for the same car for a long time.
Now, already when Öttinger began making the Express kits around 1951, the twin carb solution was the chosen way.
VW themselves introduced the 1500S (type 3) in august ´63 if memory serves, which was a twin carb 1500, along with a raise in CR to 8,5-1. This improoved performance from 45 hp DIN to 54 hp DIN. (It was abandoned again because they had a tendency to "kill themselves" on the Autobahn because people did´nt know when to stop. So the oil system and valve train was suddenly inadequate.)
Looking at it from an isolated point of view, the stock 34 mm PICT carburettor is not under carbed on a 1600 engine, for the performance window that was aimed at. The intake system and the exhaust system together is what limits the engine. What makes it even worse is, that many of the aftermarket stock muffler replacements were/are so bad that they should never have reached production level. That fact alone contributes to the public opinion that the stock muffler is crap. - That is a modified truth, because if you take a REAL VW muffler (Which can also be a Leistritz, as they were one of the main external companies to deliver mufflers to the factory) the power difference AND the cylinderhead temperatures varies significantly LESS compared to a regular 1 3/8" header and appropriate muffler. (When I began to work with ACVW´s back in the late 80íes it also took me a couple of years, or 3, to realize this.)
As for the fuel efficiency point of view. The main reason for the gain in efficiency when switching to dual carbs is that then the engines are actually tuned every once in a while, instead of just running along so to speak. Back in the days when dual carbed type 3 and busses were new or had a few years on their back, they were considered fuel guzzlers, because mechanics and private people in general did´nt know how to adjust and tune them. Today we know a lot more, and have all sorts of means and tools to help us.
Back to the 34 mm PICT carb. - IF one would invest the same time it would take to swop to dual carbs, and look just a little into why the 34 mm carb runs bad (which I will admit they can do with all the crap crome airfilters, 009´s and shiat that people install on the engines) it is relatively easy to get the same fuel efficiency as can be obtained with dual carbs. But that´s no fun. It is much more fun to take half the engine apart and throw a set of twin carbs on and then also having the bragging advantage of "yeah, I have dual carbs".
When we have one of the 2 the annual dynodays where people bring what they have, we very often see these types of engines where the story is more or less exactly as written above, and they only barely produce metter numbers than a well trimmed stock engine would do. And it continues to be a major surprise to people. The phrase "But I have dual carburettors on now" is often heard those days.
In a slightly modified form though, the 34 mm PICT carburettor can supply 95 hp easy. A little more modified and we can pull 120 horses through it. So there is definitely room for the 50 hp and then some.
IF you have a bone stock engine, and you DO want a set of dual carburettors, and you chose a DECENT header/muffler, and then you get it PROPERLY trimmed afterwards, there is a general 25% improvement in HP and 15ish % gain in peak torque and typically pulls about 3-400 rpms wider.
Hope this helps.
T |
|
| Back to top |
|
 |
VWporscheGT3
Samba Member
Joined: September 01, 2006
Posts: 2076
Location: Gardnerville, NV
|
| Posted: Fri May 16, 2014 12:00 pm Post subject: |
|
|
^ very informative
_________________
Schnell, SCHNELL!
I like being wrong, Because, it is another opportunity to learn. If you stop learning from your mistakes than what is the point?
If you have any questions about Forged ICON 4032 VW pistons just shoot me a line. |
|
| Back to top |
|
|
MURZI
Samba Member
Joined: August 25, 2005
Posts: 5063
Location: Madisonville, La
|
| Posted: Fri May 16, 2014 12:33 pm Post subject: |
|
|
| Quokka42 wrote: |
| Neither have you Murzi - I have bolted other dual carbs to a stock engine and know that very little can be gained until a few other things are changed. If you were to bolt a set of 40IDFs to a stock engine you will find the exhaust chokes the thing off before the carbs can do anything. |
Really? This a bone stock 1600, with 40IDFS and a trimill hotdog. Pretty typical of what the average guy could do. This day I spanked a bunch of 1776's and 1835's with my "stock" engine. Its all in the tune.
Link
Link
_________________
62 vert
2276
Tim’s welded heads
45 Dells
A1 sidewinder
Fk44 cam |
|
| Back to top |
|
|
Juanito84
Samba Member
Joined: March 17, 2012
Posts: 2436
Location: Colorado Mountains
|
| Posted: Fri May 16, 2014 4:47 pm Post subject: |
|
|
| vugbug68 wrote: |
see ^^^ dual carbs are much more efficient.  |
The 34PICT-3 carb is a very accurate A/F ratio setting carburetor. But its fuel efficiency is affected by at least 4 major things.
1. The carb was designed to run stoichiometric, which is not the best for fuel economy. If you wantgood fuel economy you want around 16:1 at cruise, and 13:1 at higher throttle.
2. The stock distributor was underadvanced. All cars those days were underadvanced in case something happened, like a tank of bad fuel, in order to keep the engine from destroying itself. But you can see very notable gains advancing as much as possible, especially if you can adapt an advance can that pulls 15° advance instead of 10°.
3. Carbs wear out. I'd bet that if all VWs had came with dual carbs that many would be worn out and clogged up and someone would come along, put a nice new tuned single carb and see an increase in fuel mileage and people would be saying single carbs are so much more efficiend than duals.
4. Then you have owners that put on a 009 and then enriched the carb way past stoich. Richer and more retarded. Need I say more?
So then a guy puts on a nice new set of carbs and perhaps a better curved distributor and tells everyone how much better fuel mileage he's getting. But had he tuned up his original single carburetor he probably would have seen the same notable gains.
_________________
If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine? |
|
| Back to top |
|
|
Hotrodvw
Samba Member
Joined: July 06, 2004
Posts: 6327
Location: Orygun
|
| Posted: Fri May 16, 2014 5:22 pm Post subject: |
|
|
From my experience, dual carbs aren't added with fuel mileage as a priority. Single carb equals simplicity, don't kid yourself.
_________________
'67 Sunroof
Eric
78x94 with IDA's....oober fun
Horsepower is an addiction........Addictions cost
lots of money!
Hose & Fittings |
|
| Back to top |
|
|
Quokka42
Samba Member
Joined: December 02, 2010
Posts: 3117
Location: Melbourne, Australia
|
| Posted: Sat May 17, 2014 12:01 am Post subject: |
|
|
The Tri-Mil is not a stock exhaust, Murzi.
Is there a lot you can get out of a VW without opening the case - yes, that's what got this whole thing started. Is the stock carb inadequate for the stock engine - no, it does it's job admirably, combining simplicity, reliability, fuel economy and quiet operation (Sorry guys, but noise is one of the factors engineers have to take into account to sell to the common market.)
_________________
There has only ever been one man who was perfect, and they nailed Him to a cross. |
|
| Back to top |
|
|
FreeBug
Samba Member
Joined: March 12, 2012
Posts: 4278
Location: deepest, darkest Switzerland
|
| Posted: Sat May 17, 2014 12:57 am Post subject: |
|
|
| Don't forget packaging, ease of accessibility, and the access to the plugs it affords. Most maintenance schedules for small cars expect access to the plugs without removing carbs/ manifolds...(there are exceptions, I remember being surprised by a hyundai....) Remember, the production costs were kept as low as possible, anything that could be deleted was. Look at the windshield-washer setup. Some years, standard VWs didn't even have a sunvisor for the passenger, key entry on passenger side, etc... they were built cheap! But not Ford cheap... Their incredible quality was only possible through economies of scale. One carb for 4 or 6 cylinders was standard practice on euro sedans at the time, multiple carbs was reserved for sports cars, or at least an "S" model, really not VW's market then. The 1500S was a flop. |
|
| Back to top |
|
|
vwracerdave
Samba Member
Joined: November 11, 2004
Posts: 15302
Location: Deep in the 405
|
| Posted: Sat May 17, 2014 4:46 am Post subject: |
|
|
VW also used a single carb on a Bug for assembly line construction. VW lowered the body onto the complete chassis with the engine installed. It could not be done that way on a Bug with dual carbs. It would have been a major assembly line change and a huge increase in cost to install dual carbs after the body was put onto the chassis. The Type III's could still have the body lowered onto the chassis with the engine using dual carbs.
_________________
2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK
Featured in Dec. 2001 HOT VW's Magazine page 63
Watch my racing video's http://www.youtube.com/user/okvwracer/videos |
|
| Back to top |
|
|
Hotrodvw
Samba Member
Joined: July 06, 2004
Posts: 6327
Location: Orygun
|
| Posted: Sat May 17, 2014 8:03 am Post subject: |
|
|
Who mentioned mine dictated a stock exhaust in this??
_________________
'67 Sunroof
Eric
78x94 with IDA's....oober fun
Horsepower is an addiction........Addictions cost
lots of money!
Hose & Fittings
Last edited by Hotrodvw on Tue May 20, 2014 12:56 pm; edited 1 time in total |
|
| Back to top |
|
|
bugguy1967
Samba Member
Joined: January 16, 2008
Posts: 4341
Location: Los Angeles, CA 90016
|
| Posted: Sat May 17, 2014 9:05 am Post subject: |
|
|
| MURZI wrote: |
| Quokka42 wrote: |
| Neither have you Murzi - I have bolted other dual carbs to a stock engine and know that very little can be gained until a few other things are changed. If you were to bolt a set of 40IDFs to a stock engine you will find the exhaust chokes the thing off before the carbs can do anything. |
Really? This a bone stock 1600, with 40IDFS and a trimill hotdog. Pretty typical of what the average guy could do. This day I spanked a bunch of 1776's and 1835's with my "stock" engine. Its all in the tune.
Link
Link
|
Nice, but it's also in the gearing, tire size, driver skills, engine health. A larger engine (all things being equal) would have no problem pulling past a smaller engine. Hats off to your mouse kicking larger engine butt, but they must have been lazy from the start.
Also, Hotrod's original post was misleading. If I didn't know anything and read his post, I'd be led to believe that I could get a 20 something percent power increase just by swapping to duals, when in fact he had a 3.5ish percent larger engine (57ccs) with a free flowing exhaust. Bolting on an exhaust alone requires jet changes and could add a few HP alone. Members suggest going from a 2276 to a 2332 for the additional power increase for the same price and that's only a 2.7ish size increase, but it adds about 10 HP, all things being equally matched.
I believe the carb was undersized on that 1641, and may not have been tuned as well accompanied with that aftermarket exhaust as it would've been with the pea shooters. When the duals were bolted on and finely tuned, a bunch of power was then discovered.
I believe duals can really wake up a stock engine, provided that the entire combo is matched. More air in, more air out. That's the easiest way in the import world to make power since they have more restrictions. Bigger TB, better exhaust...if they have more $, a cam swap and adjust compression. |
|
| Back to top |
|
|
Hotrodvw
Samba Member
Joined: July 06, 2004
Posts: 6327
Location: Orygun
|
| Posted: Sat May 17, 2014 9:43 am Post subject: |
|
|
I believe. I believe. I believe
This is sounding like a Shrek movie...
_________________
'67 Sunroof
Eric
78x94 with IDA's....oober fun
Horsepower is an addiction........Addictions cost
lots of money!
Hose & Fittings |
|
| Back to top |
|
|
Matthew
Samba Member
Joined: January 29, 2004
Posts: 1760
Location: Eastern Tennessee
|
| Posted: Sat May 17, 2014 5:50 pm Post subject: |
|
|
Here we go with the 57ccs again. What's that worth, 3hp? Those that are wining about headers are ridiculous. The exhaust is the first thing you would change when looking for more power.
Take two DP 1600's with 1 3/8 header and single qp muffler. One has a 34 pict and matching distributor. The other has dual 40 idfs and appropriate distributor. Assume both are perfectly tuned. The one with the duals is going to be faster and get better highway mileage.
_________________
1965 Beetle sedan
Click to view image |
|
| Back to top |
|
|
vugbug68
Samba Member
Joined: June 25, 2006
Posts: 2696
Location: sacramento
|
| Posted: Sat May 17, 2014 6:40 pm Post subject: |
|
|
| Matthew wrote: |
Take two DP 1600's with 1 3/8 header and single qp muffler. One has a 34 pict and matching distributor. The other has dual 40 idfs and appropriate distributor. Assume both are perfectly tuned. The one with the duals is going to be faster and get better highway mileage. |
this guy might disagree lol
https://www.youtube.com/watch?v=Gh3KZsPpJGA
_________________
71 Super - Backroad Thrasher
66 Corvair - Weekend Cruiser
90 4 Runner - Muddin |
|
| Back to top |
|
|
Altema
Samba Member
Joined: June 20, 2010
Posts: 2904
Location: Lower Michigan
|
| Posted: Sun May 18, 2014 4:39 pm Post subject: |
|
|
| vugbug68 wrote: |
| Matthew wrote: |
Take two DP 1600's with 1 3/8 header and single qp muffler. One has a 34 pict and matching distributor. The other has dual 40 idfs and appropriate distributor. Assume both are perfectly tuned. The one with the duals is going to be faster and get better highway mileage. |
this guy might disagree lol
https://www.youtube.com/watch?v=Gh3KZsPpJGA |
Well yeah, Pete usually disagrees with everybody! (Just kidding).
Actually his problem in that video was cheap carbs, and when the carb is the issue, it doesn't matter how many you have. Just for giggles, check out the vid where he races his buddy Steve's Ghia  |
|
| Back to top |
|
|
Mr.Duncan
Samba Member
Joined: May 12, 2012
Posts: 3542
Location: Houston, TX
|
| Posted: Mon May 19, 2014 6:38 pm Post subject: |
|
|
didnt mean to start a fight here. lol
_________________
(Owner) www.vintagecarleds.com
Red 1971 Squareback Thread
Red 1966 Beetle Thread
---------------------------------------------------
1971 Green Super Beetle (sold)
1966 Ghia (sold)
1971 Blue Super Beetle (sold)
1966 Java Green Std Beetle (sold)
1971 Red Squareback (sold)
1966 Red Beetle |
|
| Back to top |
|
|
MURZI
Samba Member
Joined: August 25, 2005
Posts: 5063
Location: Madisonville, La
|
| Posted: Mon May 19, 2014 8:43 pm Post subject: |
|
|
And oh....my vert is probably about 200-300 lbs lighter than the sedans I was racing....right? 
I'll just say this. If you believe my car on this day would run the same with a single 34pict3...changing nothing else besides the carbs, then you are sadly mistaken.
_________________
62 vert
2276
Tim’s welded heads
45 Dells
A1 sidewinder
Fk44 cam |
|
| Back to top |
|
|
Juanito84
Samba Member
Joined: March 17, 2012
Posts: 2436
Location: Colorado Mountains
|
| Posted: Mon May 19, 2014 9:50 pm Post subject: |
|
|
| MURZI wrote: |
And oh....my vert is probably about 200-300 lbs lighter than the sedans I was racing....right?
I'll just say this. If you believe my car on this day would run the same with a single 34pict3...changing nothing else besides the carbs, then you are sadly mistaken. |
Well, probably not. But now we're going backwards!
However it does seem interesting to me that the 1600cc went up only 2hp when it went from a 30mm carb on single port to a 34mm carb on dual port. So the carb size increased 13% and the hp only 3%. Well maybe with a bigger duals you'll get a bit more with stock exhaust and cam and all.
_________________
If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine? |
|
| Back to top |
|
|
Altema
Samba Member
Joined: June 20, 2010
Posts: 2904
Location: Lower Michigan
|
| Posted: Tue May 20, 2014 7:51 am Post subject: |
|
|
| Mr.Duncan wrote: |
| didnt mean to start a fight here. lol |
Sometimes things just get taken over by a detour, and it turned into a single vs dual discussion because duals were mentioned in the original post
If you want to look at your original question, the answer is economics and need. Installing a larger carb or dual carbs requires several other changes as well, and none of those were necessary for the car to meet the target design goals.
And by the way, if you look at the engine system as a whole, the stock air cleaner and the exhaust are worse restriction points than the carb, and the intake manifold flow at the bottom of the vertical pipe is a mess. The rubber elbow between the carb and air cleaner? That actually helps flow, lol.
If you want to take a look at performance gains properly, you have to view the engine as a complete system, and do your upgrades so that they compliment and support each other.
Paul |
|
| Back to top |
|
|
Altema
Samba Member
Joined: June 20, 2010
Posts: 2904
Location: Lower Michigan
|
| Posted: Tue May 20, 2014 7:56 am Post subject: |
|
|
Nice run, sounds strong and clean. What was your ET on that one?
Link
|
|
| Back to top |
|
|
Quokka42
Samba Member
Joined: December 02, 2010
Posts: 3117
Location: Melbourne, Australia
|
| Posted: Tue May 20, 2014 9:27 pm Post subject: |
|
|
Sorry Mr Duncan - I think I started the fight because I pointed out that the stock engine wasn't undercarbed. My early experiences were a little like Torben's, but even earlier and in a land where the market for performance parts is a lot smaller, hence prices higher. Not having all the parts available, or a lot of money, guys like me liked to work with what we had. Most 1&3/8 exhausts were, and are, woeful - with a crappy merge into an undersized outlet feeding an undersized to non-existent collector, but at least you got reduced back pressure. I remember a magazine once published dyno tests to prove that a stock muffler without the baffles in the pea shooters outperformed a number of "performance exhausts." That was on an otherwise bone stock engine I believe. A stock carb with a home made velocity stack into a cheap foam filter, Mazda distributor and a bit of tweaking the carb and tuning and she'd really wake up, especially if you could get hold of some ratio rockers. About 25-30% increase over stock if it all came together, then you really needed bigger carbs and until the bugspray became available these were usually from the junkyard and intended for other engines.
I had a buggy at one point which came without an engine and when I first rebuilt the engine I bought for it I just ran the type 3 carbs that came with it. A 1600 with very little work and I'm sure it would have lifted the front wheels if my tyres had been stickier.
_________________
There has only ever been one man who was perfect, and they nailed Him to a cross. |
|
| Back to top |
|
|
|
