Jet-A-Vator carb grid.

[Isaac Zackary]

Well I finally got the Bug running after all these years, with Jet-A-Vator and all!

I have an AFR meter I'm going to be tuning the engine with, as well as a CB performance digital ignition system.

[BLSTIC]

Proper programmable ignition with maps and all? I'd be very curious to see the results of just that, separate from the jet-a-vator. What carb do you run and can you post any pics of the venturis in it?

[freebeard]

I'm actually more interested in the Jet-a-vator. I wonder if would have application to the throttle body in my Dasher diesel.

Is it the CB Magna-spark? Keep an eye out for corrosion inside the billet housing. Mine lasted 2-3 years.

[BLSTIC]

Throttle body in a diesel? I know of only one system like that, and the throttle was only just restrictive enough to provide a variable vacuum signal for the pump as a load input

[Angel And The Wolf]

My ex-brother-in-law went into business with a friend. The friend had built a plate to fit between the carburetor and the manifold. screwed into the plate, at three points from the sides, were three ultrasonic vibrators from a dishwasher.The theory was to pulverize the fuel, and tests on a 390 Galaxie produced 50 mpg. they were blocked at every turn from manufacturing the plate, and ended up selling the rights to Texaco. Someone should give it a try.

[BLSTIC]

I wonder what results that same Galaxie would have got with modern 50-micron fuel injectors?

[Isaac Zackary]

Originally Posted by BLSTIC

Proper programmable ignition with maps and all? I'd be very curious to see the results of just that, separate from the jet-a-vator. What carb do you run and can you post any pics of the venturis in it?

I'm using what's known in the VW world as a Solex 34-4 carburetor, which is practically the same as the very common 34-3 carburetor, both used on 1600cc aircooled VW engines, except the 34-4 has a thermostatic two step accelerator pump. The one and only venturi in it is 26mm in diameter. You can find pics all over the internet of the Solex and other brand 34-3 carburetors.



First I'm setting the ignition timing map to match that of the original that went with this engine. I couldn't find the exact match but this one seems close enough:



After that I'm working on AFR's first before diving into tuning the timing map. This is because the AFR will affect the proper timing since the AFR changes the flame speed. (It's very common for to hear of guys that bought a mechanical advance distributor without any vacuum advance that end up having to enrich the AFR to make the car drivable due to the lack of ignition timing.) I already ordered a smaller pilot (idle) jet, a 50 instead of the 55. I'm sure I'll have to go even smaller, but I thought I'd start there. Basically I'm aiming for a 17:1 AFR at low loads and want that to jump to 13:1 at high loads. Supposedly the Jet-A-Vator will also cause a leaning effect.

After the AFR's are dialed in it will be time to set the timing map for best torque and efficiency at any moment while not causing any pinging.

This is how one VW expert puts it:

What is needed is to find the timing point at EVERY RPM point where you are around 4 degrees retarded from detonation under full throttle, since this is the “ideal” time for our spark to occur.

From:

VW Distributor Options « VW Parts - Aircooled.Net

[freebeard]

I've got a new 34-3. I'm looking in thrift shops for a bell jar about 8x8" so I can put it on a wooden base and inside the bell jar, for display purposes.

BLSTIC — This is all new to me (the Dasher has a 'brake servo exhauster'). I thought diesels divide into throttle body or port injection. I check the manual and it appears to have port injectors. So... question answered.

[sser2]

Flow restrictor of this kind will worsen fuel economy because it will reduce air flow speed where it matters most: at carburettors Venturi. Economy can be improved by fitting carburettor with smaller bore, but of course at the expense of performance at high engine speed.

Two-barrel carburettors combine the advantages of small bore at low speeds and large bore at high speed.

If gadgets like this were really effective, they would have been standard on all carburettors 70 years ago.

[Isaac Zackary]

Originally Posted by sser2

Flow restrictor of this kind will worsen fuel economy because it will reduce air flow speed where it matters most: at carburettors Venturi. Economy can be improved by fitting carburettor with smaller bore, but of course at the expense of performance at high engine speed.

Two-barrel carburettors combine the advantages of small bore at low speeds and large bore at high speed.

If gadgets like this were really effective, they would have been standard on all carburettors 70 years ago.

Many late model carbureted cars did get grids under their carburetors for emissions purposes.

I don't see how it slows the air speed through the venturi, except at high RPMs and throttle. If it slowed it at cruise it would not be able to keep the same speed. It can slow the air speed around the throttle plate, but the grid should make up for that.