Solex air flow

[Jerry C]

What is the Solex on a 73 GT rated at in CFM? Is it rated?

[oldopelguy]

A (very) little forum searching yielded these #'s from RallyBob:

"A Solex flows 190 cfm, a 32/36 Weber flows 270 cfm, and the 38 DGAS flows 330 cfm."

[tekenaar]

Originally posted by oldopelguy A (very) little forum searching yielded these #'s from RallyBob: "A Solex flows 190 cfm, a 32/36 Weber flows 270 cfm, and the 38 DGAS flows 330 cfm."

Thought I read somewhere that the '68-'70 Solex (HC engine) flowed 220cfm?

Bob???

[tekenaar]

Originally posted by oldopelguy A (very) little forum searching yielded these #'s from RallyBob: "A Solex flows 190 cfm, a 32/36 Weber flows 270 cfm, and the 38 DGAS flows 330 cfm."

So, kinda makes me wonder what a 40DFAV flows . . . you know, the other synchronous carb that fits our stock manifold?!

[GoinManta]

Originally Posted by oldopelguy A (very) little forum searching yielded these #'s from RallyBob: "A Solex flows 190 cfm, a 32/36 Weber flows 270 cfm, and the 38 DGAS flows 330 cfm."

A BMW article I found online (see attached) said this:

Solex : 205
32/36 : 265
38 DGAS: 295
40 DFAV: 335

That said these were tests done on a 76' 2002 BMW, so different intakes, etc..

Assuming Bob did his own tests and the results he mentioned were from an Opel.

First we ignore the Solex (since it may not have been the same one).

He got about 2% more out of a 32/36

He got almost 12% more out of the 38DGAS.

So using the same 12% number, you could make an educated guess that on a ported Opel intake, the 40DFAV would be in the 375 cfm range.

Charles

[RallyBob]

The flow numbers I mentioned for the 32/36 and 38 DGAS were published numbers from a book...can't recall the title offhand. The Solex was from my own flow bench, but that was the bare carb on an adapter, no intake manifold. The manifold would alter the numbers drastically, which is probably why the BMW numbers differ.

Bob

[RallyBob]

Originally Posted by tekenaar So, kinda makes me wonder what a 40DFAV flows . . . you know, the other synchronous carb that fits our stock manifold?!

I was told by my old Weber supplier (Interco parts in NY) that the 40 barely flowed better than the 38, the reason being the venturis were almost the same size. I suspect that on a sub-130 hp engine you'd never notice the difference, since at that power level you can't truly utilize all the airflow a DGAS has anyway, so a DFAV is a moot point. Probably all you'd see is better throttle tip-in response, and a hair more top end speed.

But if the engine's cam, headwork and compression can support it, the bigger carb would make a difference. Like when I used to bore out 38 DGAS venturi's to 31 mm (from 27mm). This mod is too much for a normal street engine, but on a tweaked engine it makes a big difference in the mid-to-top rpm range. Works well with high compression especially,and allowed me to see 155 hp (flywheel) from a 2.0 litre streetable engine.

Bob

[GoinManta]

All the articles I read (and a frew with tests they had done) was that the 2.0L BMW 2002, had a noticeable difference between the 38DGAS and the 40DFAV.

I guess I will never know though, since i never owned a 38DGAS to compare it too.. Would be interesting to run the two seperately on the dyno at Carlilse. If someone had a gasket kit and 38DGAS to spare..

Charles