Float Bowl Orientation

dllubin said:
Perhaps that is why Fiat switched from the Michelin XAS to the Pirelli Cinturato in the summer of 74. The Pirellis wore like iron but we're pretty low on grip compared to the Michelins. The guy I was renting a house with at the time got an X about a month after me and was surprised at the difference having driven my X previously.
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One of my favourite X19 pictures, probably XAS shod, check out the sidewall deflection on the rear tyre!
fiat-x1-9-2.jpg

note: this is probably right about the time the engine stumbles...

@EricH read the PBS book.

SteveC
 
Steve, I don't mind trying those vent caps but I'm not clear on why the open vent might be the source of the stutter.

In further discussion of odd intake manifolds, what about manifolds to mount dual DGV carbs, which are two barrel progressive carbs....how odd.
 
carl said:
Steve, I don't mind trying those vent caps but I'm not clear on why the open vent might be the source of the stutter.

In further discussion of odd intake manifolds, what about manifolds to mount dual DGV carbs, which are two barrel progressive carbs....how odd.
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rather than the vent caps. I'd be inclined to try the E tube extenders you find on more current versions of the IDF... I never tried those when trying to tune out the stumble from my IDF's ... which was back in the early 1990's and I'd never seen them then. but they now seem to be quite common

Dual two barrel progressives.... I recall a friend (a long time ago) had a Toyota KE10 Sprinter, which had a setup like that, two x dual throat progressive carbs, each one feeding two cylinders of the 1200cc K series engine

SteveC
 
@Steve Thomas I just thought of another example of correct fitment / orientation...

recall the days of the Group C touring cars? For the uninitiated, Australian tin top racing in the 1980's were real production racecars, and even our home grown Holden and ford Cleveland V8's were making well over 100hp/litre back in the 1980's on pump fuel.

The rules limited the engine to the original inlet manifold, and like most racing classes any cylinder head and manifold prep could only involve the removal of metal, not adding any.

Carburettion was free, so the "go to" setup was a pair of 48IDA's mounted atop the original iron manifold with an adaptor plate. Now you would think perhaps this application could favour mounting of the carbs transversely, allowing the linkage to operate the carbs from one side... but no, the preferred (and really only) method used was to mount the carbies longitudinally, but facing each other, so the throttle blades tipped in opposite directions towards the centre, and the idle jets were positioned to the outside of the engine on both sides. Made for an interesting bell cranked linkage to make them operate that way, but mixture distribution was much better in this configuration than any other.
groupC torana.jpg



3 x IDF's on the 130 V6, well quite simply that's full of compromises. difficult access to the mixture screws as they face rearwards, and I'm sure balancing them is a bit of a chore, in fact in the video they don't sound terribly well balanced to me, with far too much of a bop/bop/bop sound and sounds quite flat, well tuned IDF's have a distinct "chip/chip/chip note when they are set just right.

A far better result could probably be had with a pair of IDL carbs, or a trio of DCNF's and then use a proper air filter from a Fiat Dino, rather than the nasty looking chrome jobbies. Someone mentioned a modified Ferrari manifold... where did that notion come from? The Dino V6 is completely different architecture and bears no relation to the V6 in the Fiat 130...they are not the same width / height or even the same angle of V... and the only Ferrari V6 with IDF's is a Stratos, and they are mounted longitudinally as the engine is transverse.

SteveC
 
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carl said:
open vent might be the source of the stutter
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my very limited understanding [have not had one of these carbs in my hands] is that G produces float bowl slop/surge and fuel splash around places it shouldn't oughta. Some finds its way into the air correction jets via the emulsion tubes. The vent is supposed to allow the air jet to still see air but be protected from stray fuel. SteveC suggestion on longer emulsion tubes is the same kind of thinking, I think :)
 
carl said:
Steve, I don't mind trying those vent caps but I'm not clear on why the open vent might be the source of the stutter.
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Carl, not sure if that is what your are talking about, but I ran 4 snug fitting tubes on top of my air correctors on my DCNFs for years.
The idea is that under hard cornering, the flue sloshes out of the vent and goes down into the hole in the top of the air corrector. The hole is supposed to allow the ingress of air that mixes with fuel. Replace that air with fuel and the mix goes very rich in an instant.

But I am sure that for this to occur, one needs a race track and race tires.
 
carl said:
I wonder if that's why modern IDFs have extended jet stack ends.
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I think they just fit them as standard equipment now to save any possible issues when people (like you) mount them in the incorrect orientation ... or onto vehicles that can generate relatively high G forces when cornering.

Personally, I've never had an issue with G related hiccups when I've used 40 / 44 IDF of 48IDA's on a 124/131 fitted twin cam engines, which would number in the dozens of times,. and quite a few track day cars in among them

plenty of standard equipment IDF's on other makes/models don't come fitted standard with extended E tube holders, like Ford RS Escorts, though the humble Alfa Sud sprint has twin 36IDF's on some models and they do have extended E tube holders (but they also came fitted with quite sticky tyres)

for under $50 you can get a set of 4 and try them, and see if the stumble on that tight right hander goes away...

SteveC
 
Like you, I never had a problem with IDFs on my spiders at track days. I may get those extended stacks just to make the forum happy.
 
Ferrari Dino [an object of desire] has a transverse V6 with 3 DCNF. They are mounted in the V so each carb serves one cylinder in each bank and when in the Ferrari - the carbs have their barrel pairs aligned north south [the engine is transverse = east west]. The same engine in a FIAT Dino is aligned longitudinally [north south] and the carb installation is unchanged which means the barrel pairs are aligned east west. Now, I have not driven either and I expect, never will - but one of them has its float bowls oriented "wrong"......
 
Steve Thomas said:
Ferrari Dino [an object of desire] has a transverse V6 with 3 DCNF. They are mounted in the V so each carb serves one cylinder in each bank and when in the Ferrari - the carbs have their barrel pairs aligned north south [the engine is transverse = east west]. The same engine in a FIAT Dino is aligned longitudinally [north south] and the carb installation is unchanged which means the barrel pairs are aligned east west. Now, I have not driven either and I expect, never will - but one of them has its float bowls oriented "wrong"......
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In the Fiat Dino the orientation is correct, the Dino 246 has the "wrong" orientation, Id guess they made more Fiats than they did Ferraris. I have driven both and I prefer the Fiat coupe.

Why, well we all know Ferrari's are for posers and Fiats are for drivers....

the same V6 in the Strato's uses IDF's carbs, which are supposed to mount with the throttle shaft in the direction of travel.

the 308 carbed version also uses 4 x DCNF's, and they mount them correctly...

SteveC
 
If you look at period Italian anything - DCNFs are oriented everywhichway. Lambo V12 right but their V8 wrong etc.. I suspect that the DCNF is not sensitive in this regard.
 
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