Kadron Solex Duels, Has anyone tried this setup? Options

[Nozzle]

Just read a thread comparing the virtues of different carb setups and came across a link for a company selling duel single Kadron carb kits for the type 4 engines.

http://www.shop.kaddieshack.com/BRAND-NEW-...20L-43-4520.htm

I'd never really heard anyone on this board talk much about the duel single-choke carbs as a viable option. It sounds like a nice compromise between the efficiency of a stock D-jet and power of duel twin-choke Webers or Dells.

Has anyone used this setup for a 2.0 engine before and if so what cam did you use?

Thanks,

John

[ChrisFoley]

There's an inherent problem with dual singles on a flat four engine.
The intake pulses aren't timed properly for good balance of the air/fuel charge.
This becomes really apparent if any sort of performance camshaft is installed.

The engine firing order, being 4,3, 2,1 means one carb does 2 intake pulses sequentially and then waits one full crank revolution for the other carb to do its 2 intake pulses.
The result is that the forward cylinders (2 & 4) run at one mixture and the two rear cylinders (1 & 3) at a very different mixture.
This is exacerbated by reversion from any cam overlap which will further screw up the second pulse on both carbs.

Combined with the rather short intake runners typical of a dual carb installation, an engine with a performance cam and dual singles can not be tuned to run well.

[DBCooper]

There's an inherent problem with dual singles on a flat four engine.
The intake pulses aren't timed properly for good balance of the air/fuel charge.
This becomes really apparent if any sort of performance camshaft is installed.

The engine firing order, being 4,3, 2,1 means one carb does 2 intake pulses sequentially and then waits one full crank revolution for the other carb to do its 2 intake pulses.
The result is that the forward cylinders (2 & 4) run at one mixture and the two rear cylinders (1 & 3) at a very different mixture.
This is exacerbated by reversion from any cam overlap which will further screw up the second pulse on both carbs.

Combined with the rather short intake runners typical of a dual carb installation, an engine with a performance cam and dual singles can not be tuned to run well.

That's called the "Kadron Syndrome" and is spooky, you can pull off the either 2 or 4 spark plug wires and the engine keeps idling the same, doesn't seem to notice. Not just Kadrons, it happens with any dual-single setup, even the OEM. It's an odd phenomenon, but happens only at idle, at anything above idle the mixture velocity is higher and it disappears.

On T1 engines Kadron/Solex/Bocar/Brosol equipped cars perform nearly as well as IDF cars on the dyno, are equal through mid-rpms, but don't flow quite as well at high-rpms so give up a few horsepower. If you look on The Samba or google you should be able to find some comparison dyno charts. Kadrons do much better than centermount carbs and are much more driveable day-to-day, though neither compares with the driveability of stock fuel injection or Weber IDF's. If you're at all dubious about high performance Kadrons look at AJ Sims (Lowbugget), who's famous in VW circles for building giant killer Kadron drag race cars that are often faster than the IDF/IDA competition. There are a lot of T1 people who could afford anything that are very happy with AJ's products, simple and fast. That's relevant because acceleration is kind of like a moving dyno, a relatively pure measure of horsepower.

There's a lot more variety in carburetor combinations available for T1 engines, and a good summary comparison from John Connolly of Aircooled.net at http://www.aircooled.net/vw-carburetor-opt...-selection-101/. Not all those options are available for 914's, so you need to keep that in mind as you read. What complicates things is that there were an awful lot of slow VW buses built with T4 engines, lots more than 914's. Unfortunately that means the bus T4 engines get more attention than 914's but they're generally less performance oriented.

With all that being said it seems to me the best combination for a stock car is the stock fuel injection. No question. For a modified car it's IDF's or Dellortos. If you're hugely budget restrained and can't go the few hundred extra dollars for the IDF's then there are the Kadron/Solexes. And in last a two-barrel centermount, but only when you've found one for free that your brother left in a box in the garage and it's the only way you can get your car running. OK, I may be opinionated about the centermounts, but it's a free country.