Which carb for me?

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The13bats
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Joined: Mon Dec 29, 2008 1:27 am

Which carb for me?

Post by The13bats » Thu Sep 13, 2012 7:47 pm

I want to get some scoop on what carb might be better for me and what I have and what I do with it,
The engine is a stock 1600 except it runs dual cannon exhaust and 034 dizzy, ( please do not try to sell me a 009 )
At the moment it runs a 34/3 carb, the engine is in a trike that I just ride I don't race it.

I have been building customs of all kinds wells over 30 years and feel I have the tune on the engine "as is" the best it can be, I really do not know carbs condition, besides PO bought it new in 09
It lacks pep, seems adding throttle doesn't give the kick it should, perhaps it's a tired engine or I am asking too much, it's a trike lighter than a VW car and in traffic I would have to really give it all it has just to keep up with normal take off traffic.

I bought a new in the box Empi ICT dual set up ( Please do not trash Empi it helps none, some of us have budgets )
I was thinking on the VW like if I was tuning a v8 in my vette, long intake runners kill low end torque, in most cases they are for adding RPM,
So the short intakes one gets with duals on a VW should add some pep just because the runners are so short, then the added fuel shouldn't hurt, ( within reason ) plus it would seem the ICT is a better carb than the PICT ( opinion )

But I just learned doing some reading on the carbs they will not fit on my trike due to the dual cannon exhaust...*%^&^*$)#......people dont want duals AND duals???

I really can't imagine the PICT carb is the best for the engine, they seem on the small side, but like I said when I started clue me it, I know the subject is loaded in an some cases is personal taste and opinion.
But please hit me with some ideas for which carb or carbs to use on this thing,

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Marc
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Re: Which carb for me?

Post by Marc » Thu Sep 13, 2012 9:33 pm

Another STF member with a trike has similar carb-related issues...to save a little typing time, let me show you the last advice I PM'ed him since much of it is relevant to you. After you've read/absorbed that, come back with remaining questions.
Dual-cannon style exhausts are horrid, offering zero performance gain and a sound that can be politely described as close to that of two out-of-tune Harleys idling side-by-side - the only reason they exist is for dunebuggy applications, where appearance seems to be more important than functional considerations. The "G-Down" system that's come on the market recently shares the same piss-poor configuration, where 2 cylinders which are not evenly separated in the firing order are paired together in a common muffler. STOOOPID ;)

<All single-carb ACVW engines are susceptible to more driveability problems (specifically a hesitation upon off-idle acceleration) than conventional engines because of the length of the intake tract. When the throttle's cracked open and manifold vacuum decreases, fuel tends to condense on the walls of the intake manifold so that for a moment the mixture arriving at the cylinders is too lean to fire. A few heartbeats later that condensed fuel dribbles down into the engine, but in the form of droplets which are too large to burn properly. The carburetor therefore has an accelerator pump to inject excess fuel when the throttle's cracked in order to cover up this temporary condition. The intake manifold is also kept warm by piping exhaust gasses up alongside it - that also reduces the condensation problem.
In addition, thermostatically-controlled aircleaners are employed to bring warmed air into the carburetor, and distributors are designed to add a little extra off-idle spark advance (lean mixtures stand a better chance of firing with early timing). That's why SVDA and DVDA distributors are favored over the centrifugal-only type (such as the "009") - they can manage that special trick if connected to a "ported" vacuum supply that surges as the throttle plate comes off idle.
Dualport engines gained a few horsepower from the same displacement by enlarging the size of the intake tract; the price for that is lower charge velocity at a given RPM (therefore lower manifold vacuum, which puts them closer to dew-point conditions than a singleport of the same displacement).
No aftermarket exhaust system provides heatriser flow comparable to that of a stock muffler; just "upgrading" from the stock muffler and thermostatic aircleaner is often enough to cause tuning headaches.
Weber once made a nice little 1-bbl (36DGV IIRC) that bolted right onto a stock manifold, but they're obsolete/hard to find parts for...and the accelerator pump design (a plunger down through the carb top) made maintenance a PITA so I wouldn't recommend that one.
The problem with almost all 2-bbl manifolds is that they're even larger in cross-section than the stock one, with piss-poor preheat passage design that barely transfers in enough exhaust heat even if there's plenty available from a stock muffler. There are "deluxe" manifolds available for a few 2-bbls (including the Holley/Weber progressive) which bathe a large portion of the intake runners in exhaust heat, but they don't come cheap. By the time you factor in the cost of such a manifold (which isn't a silver bullet, it only makes the best of a horrible situation) you may as well step up to a set of 34ICTs and be done with it.>

In your case, if you MUST stick with the dual-cannon exhaust system my advice would be to make the best you can out of the 34PICT-3/034 distributor combination. On such a light vehicle, it should perform acceptably even with no preheat, at least on warmer days. Personally I'd want to change the exhaust system and try the 34ICT clones (I have genuine 34ICTs on my daily-driver Beetle and couldn't be happier with them, even though they're "saddled" with a German 0 231 178 009 distributor).

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The13bats
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Re: Which carb for me?

Post by The13bats » Thu Sep 13, 2012 10:09 pm

Thanks for the reply,
I come from a background of "in most cases" we can do better than stock and many times tried and true VW fans will say stock is best, but lets face it, with trikes and buggies with the engine hanging out for all to see many things stock are not practical or the visual aesthetics just won't allow,
Do duals look better on buggies and trikes than Stingers?, ( I cant entertain stock exhaust here ) I guess it's personal taste, but I never liked the "stinger" look, rates up there with the coffee can exhaust tips import tuner kids run. my wife saw one and asked why the car was happy to see her.

I believe I need to look into the 4 into 1 that ends in say a sideways glass pack type muffler, I could live with that.
The sound...you cracked me up, for 30 years I have dealt with the silly putty putt putt of the VW engine, too many years of cool as hell kit cars ruined when they hear it and some wise ass yells out "It's just a VW" not our fault.

Okay,
So it doesn't get convoluted,
Which 4 into 1 would you suggest?

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Marc
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Re: Which carb for me?

Post by Marc » Thu Sep 13, 2012 10:23 pm

What do you think about the looks of something like this? Basically it's the classic "stinger" style header but with a turned-down muffler to avoid that priapristic look:
http://i19.photobucket.com/albums/b161/ ... C00014.jpg

It's hard to see the header in these pictures, but this is the A-1 Sidewinder that my son's using on his baja (with massive resonator/muffler combo of his own design): http://www.shoptalkforums.com/viewtopic ... 8&t=125993
His is extended back to make room for a Type III cooling system, so of course it would fit much tighter to the engine otherwise. The last couple of pictures show the sideswept merged collector pretty well - that type of collector is the best anyone's come up with for VW performance.

A-1 makes some truly nice systems, and will even custom-modify to suit your needs (we have another Sidewinder that he built wider to accommodate a big oil sump and stock thermostat0 for a reasonable surcharge. As a rule none of these systems have any provision for intake manifold heat since nearly everyone who can afford one already has dual carbs...but I suppose even that could be added if you needed it.

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