i was just wondering what is the difference bettween a downdraught and sidedraught carbie in performance terms? ive beeen told sidedrought are better?

because i have the oppurtunity to get a 40mm (i think it might be bigger?) sidedraught weber for my datto instead of the a 32/36 DGV downdraught

is the side draught "overkill"? would the 32/36 be better? (i have a standard A12)

sideie!!!!!!!

someone else will give tech reasons, but i reckon they are better, just look at flow path

yeah but is the big side draught weber over kill for my standard A12 like will it run #### down low rpm? or will it give heaps of go?

nup, if you get the proper size choke (venturi bit) then itll be fine, unless your motor is stuffed, then thats a diffrent story

it should run quite similar down low but scream up high, thats if you get a mechanic to tune it up for you unless you have a fair idea on jetting and chokes ect.

I would go with the sidedraught carbie for sure if you are chasing performance. DCOE webers and Delortos, Solex, for that matter are very versiltile carbs and can be setup to suit almost any application.

The stand out difference between the DCOE sidedraught weber and the DGV downdraught, is that the DCOE has syncronous butterflies (both throats open at the same time) whereas the DGV has a primary and secondary (cant remember if DGV has machanical or vacuum secondaries).

If you are wanting a daily driver that is easy to drive, i would go with the DGV weber. Im not saying DCOE's cant be used for a daily driver, they just can be a bit trickier to setup, tune and expensive to buy jets / venturies / emulsion tubes. On the otherhand, there is nothing quite like driving a car with an engine with a pair of sidedraught webers. You have to experience it to know what i mean.

Just to confuse the issue, you cant forget the IDA and IDF downdraught Webers (i think there are a few other models as well). These carbs have are very similar to the DCOE sidedraught in their functionality, but stand upright like a downdraught.

At the end of the day i would give the sidedraught a go. If you have all the bits (manifold, linkages etc). Your car may run better than ever. If you are chasing indepth info on weber tuning and performance, buy or borrow a book on weber carbs. They can explain better than i ever could..

Hope this helps

Cheers

Funny thing is the 2001 160hp r1 motorbike uses downdraught mikunis!! not sidedraughs
and the semi sidedraughs downdraugh mikuni set available through pitroad in japan and nismo in the states are stated to produce 20% more than webers.
There is a chart showing two identical 1400 a14s worked by www.Matsuoka-ts.com that when tuned with either miks and webs the miks setup produced around 174hp and the web only 150 odd! But dam those miks are pricey lol ;0

Quote: I suspect they also have near vertical inlet ports that point directly at the back of the inlet valves...

www.Matsuoka-ts.com didn't work for me. did the solex-mikunis have the same size chokes as the webers they used in the test? Do Matsuoka happen to sell Mikunis? Let's face it, these carbs are fundamentally the same design. sure they have some minor differences, but I cannot understand such a huge power difference at WOT.

unless you are talking about motorbike mikuni carbs with the slide throttle? They may have a slight advantage but once again 16% extra power on the same motor is incredible!

speaking of carbs i have four single linked carbs off a 750 CB motorbike sitting in my shed all polished . at one point was really really keen to put them on my datto because it was sometihng different, these motorbike carbs are mechanical injection as well

has anyone played around with motorbike carbs on thier A series?????

Sidedraughts are not technically better just cause they are on their side.

But with most inline engines they are better because the air/fuel mixture goes more straightly into the cylinder, it doesn't have to go down the carb, then make a 90 degree turn in the manifold to get into the cylinder. This help the airflow, but more importantly the fuel doesn't turn as fast as the air, which can cause mixture distribution problems when the path isn't straight. But on a motorbike with the engine at an angle, the downdraught might have the advantage of a straighter path. Ditto for V8s or flat engines.

Plus, with dual-sidedrafts on a four cylinder, you get the extra advantage of a tuned-port intake path for each intake port. This is just like the individual tuned-port runners used in fuel injection. On a Porsche six, dual-triple Webers can be used for the same reason. Most practical manifolds have short runners ... which is better for (very) high-rpm rather than low.

Now there is some more technical differences between variable-venturi carb design (mostly used in sidedrafts) and standard venturi carbs, but I'm not sure which is better in that respect.

speaking of carbs i have four single linked carbs off a 750 CB motorbike sitting in my shed all polished . at one point was really really keen to put them on my datto because it was sometihng different, these motorbike carbs are mechanical injection as well

has anyone played around with motorbike carbs on thier A series?????