TheSamba.com :: View topic - What is the main difference between IDF and IDA?!

Mon Oct 22, 2007 7:22 pm

Can some1 answer me this question?! :?
I know that the IDAs are more expensive but is it only?! Or there is something else?!

Thanks

Mon Oct 22, 2007 7:31 pm

Good description of all the differences here
http://www.redlineweber.com/html/Types/making_the_right_choice.htm

Basically IDFs are smoother and streetable but make less power than the IDAs of the same size. IDAs can be smoothed out with more progression holes, etc... but IDFs are what most people use.

Mon Oct 22, 2007 7:33 pm

I find IDAs with a 3rd progression hole work as smoothly as my old Dellorto DRLA carbs.

Mon Oct 22, 2007 8:03 pm

IDAs can put bigger venturis than DRLA or IDF...45mm??

their size also make them look badassss

Mon Oct 22, 2007 8:04 pm

pupjoint wrote: their size also make them look badassss
They are huge and a tight fit under a closed decklid.

Mon Oct 22, 2007 8:06 pm

48IDF vs. 48IDA's?

IDF's have 4 progression holes.
IDA's come with two, but can be drilled for a third.

Both IDF's and IDA's have 48mm throttle plates.

IDA's have a wider bore spacing than IDF's. This allows IDF's to fit in an engine compartment easier with air filters (not $$$ filters anyway).

Now here's the big difference that I wonder if many people really know:
IDA's open up to about 50.5-ish mm at the top before the velocity stack. IDF's open up to about 46.5-ish mm at the top before the velocity stack.

BUT, that doesn't mean IDA's will make more power in all cases. They will only make more power IF the IDF's are choking it down. IIRC Jake Raby made roughly 250hp with IDF's a few years ago. The IDF's will support a LOT of power, but it's "kewl" to have those IDA's, so people just have to have them. Doesn't mean they are making more power with those than a properly sized carburetor though.

I am yet to see ANY back to back testing to show if and how much more power an IDA makes compared to an IDF. I would be VERY interested to see where the difference is and by how much, but in order to be reliable info, both would have to be dyno'd at the same A/F ratio and venturi size so all else is equal.

As for modifications, IDA venturi's can be machined out larger than IDF venturi's. I believe the largest an IDF vent can go is 42mm-ish, while I had some IDA venturi's machined out to 46.3mm. Though I have seen a set of IDF's run without the venturi all together (and it actually ran well). Both carbs can be opened up. 51.5mm is common for IDA's, and i've seen a set of IDF's opened up to 50mm.

Street car (true daily driven street car) I would say IDF's are the way to go. Weekend driver (or what a lot of people in the VW community try to pass off as "Daily Driver"), will work fine with IDA's.

Either way EFI knocks the socks off both of them. :P

Mon Oct 22, 2007 8:19 pm

For a daily driver i'd go with Dellorto DRLAs. I put 350,000 daily miles on them with never a clogged jet or breakdown related to the carbs.

Mon Oct 22, 2007 8:33 pm

Amen to that. A good set of DRLAs, man, you can't go wrong, if sized right.

Tue Oct 23, 2007 6:47 am

nah, i'd still go EFI over Dells. :wink: