weber dcnf 40 vs idf 4

i put idf 40. more torgue for very lor rpm. and i think more hp. i go dyno to chec them to tell for sure the diferent. but really is very better than dcnf. is like ijection now. dcnf 40 dont job good for 128.
 
Hmm... well, if the IDF's are running better and producing more power, then the DCNF's; what point or question is the purpose of this thread? Some applications may necessitate one over the other, but it probably comes down to personal preference?? I think if each type is tuned properly, the differences would be negligible as you can only flow X amount of air and meter Y amount of fuel effectively. How efficiently a carburetor does this, will vary model to model, but once again; if tuned properly, they will both do the exact same thing. One might be more difficult or easy to dial in, is all. In sure some very minor differences in TQ/HP at a givin rpm will vary from side draught to down draught. Really beginning to split hairs though.
 
I think Jim is just sharing his experience with the IDF 40's he now has, compared to the 36DCNF's and 40DCNF's he had before, and asking what opinions others have on Weber options (DCNF vs IDF). Maybe a little bit of language barrier but his posts on other threads help tell the story.

Jim, what other modifications do you have? Can you post pictures of your engine? Let us know the dyno results...did you dyno it with the DCNF's for comparison?
 
The big question is whether the two types of carbs are jetted the same an maybe if they have different velocity stacks on them.
 
Dr.Jeff said:
asking what opinions others have on Weber options (DCNF vs IDF). Maybe a little bit of language barrier
Click to expand...

Certainly a possibility. I read it as broken English originally, and I still couldn't decipher if it was a statement or question.

Jim: I could be wrong, but I believe the consensus is that; for the Fiat SOHC: Down draft carbs provide the best all around increase in performance. Side draft carbs, such as the DCOE are better for WOT top end performance. I would imagine IDF vs DCNF would come down to manifold style and tuning. If all things are equal such as venturi size, throttle plate size, etc.. they should be flowing similar amounts of air. Do not read this as a DCNF will perform the same as an IDF and vise versa, if they are both jetted the same (for example: both using #150 main jets and #30 tubes, etc. ), as that wont be the case. However, if both carbs are fine tuned to the same degree, and both are producing the same stochiometric A/F levels, at the same rpm; then the carbs are effectively equal, and similar or like performance would be expected. Beyond this, I think its a matter of personal preference & familiarity; cost & availability, and ease of installation/fabrication of linkage assemblies. Space and/or class rules may apply here as well, if racing.
 
hi! my engine is 1500cc. catcams 278,biger port head, 1mm cut head for compresion, ansa 4-2-1, electronic ignition, weber doubles dcnf 36. i do all setting the best is : 30 venturi,45 indle,130full,f36,200air,40bump. 104hp. 13,5nm
i change and i put dcnf 40: dyno 107hp 14nm. 30venturi,130full, f22 or f36 the same i chec at dyno. 185air,55indle. i lost at low rpm 4hp. only up 5000rpm i take extra 3+hp. 1500rpm -2400rpm dont job perfect. i chec and i found all with dcnf 40 is the same at this rpm. have problem to job indle with full at this rpm.
i change and i put idf 40 from 124fiat. the best tunning at road is : 32venturi,f11,180air,138full,50 indle. this setting job perfect. have more more more power at low rpm. nothing problem. and i am sure extra hp 2-5hp. but more more more torgue! i go dyno to do perfect setup. and i tell what power diferent have. i have old dynometer with dcnf 36 and 40.
12080097_10153317701382800_805880898492203681_o.jpg
 
Good description of what you have done. And nice to see you did a dyno session; often people report results without any data to base it on. Am I correct that "Run 1" was the 36 DCNF's and "Run 2" with the 40 DCNF's?
It does not surprise me the 40 DCNF's offered a little less "low end" response compared to the 36 DCNF's. But I am surprised the 40 IDF's feel like they have more low end. It will be interesting to see the dyno results with these (IDF) carbs, let us know what happens.
Thanks for posting. What part of Greece are in you? Lots of older Fiats?
 
no is dcnf 36. 1h and second with dcnf 36. i put this days the dcnf 40 to see. for low rpm is very faster idf than dcnf. up rpm i am not sure.
 
I really wanna follow this thread, but its too painful. Is there a translation program or something we can offer?
 
To be honest this one is a little harder to translate: I believe he's either saying this dyno result is only for the DCNF 36 (not 40), or that I got it backward and 1st run was with DCNF 40 and 2nd with DCNF 36. But he feels the currently installed IDF's offer greater low RPM results (compared to either DCNF), and he can't really tell if the upper RPM range is better or worse with the IDF's. Earlier he stated the IDF's have yet to be dyno'ed for verification.

I applaud him for participating, especially in a foreign language...hell, I can barely speak English let alone any other languages. Clearly he is an enthusiast of the cars and enjoys modifying and testing his, as do we. Recently I spent a couple weeks around the Greek islands and it was very interesting to see how their car culture compares to ours. Frankly there is a lot less BS than here, just old fashion gear heads doing it for the passion rather than trying to impress or attract attention (not saying everyone here does that, but you get my point). Also have to say the people were extremely friendly and very down to earth...good times, cool cars.
 
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I agree whole heartedly. I think in general terms; this forum (being a world wide enthusiast page) would benifit from a translation feature. It would make life easier for those of use, who only speak English, and for those who don't speak Engilsh as well. I use google translate, when I shop eBay De., as I cant speak German. The translator is supposed to be for a word or phrase, but Ive typed/ had translated full message's. Maybe a feature similar, at the text box heading would be useful??
 
Funny, now that you mention it. When you consider the international nature of any internet based forum, its odd they don't have a "translation" feature built in as a basic part of the structure. We've had several different languages interact on here and I'm sure it would be a benefit to all of them. Like you, I also use Google translate on things like eBay Italy or Germany. But sometimes its a bit difficult because every time I change the page I have to ask it to translate again. Or sometimes it only translates a portion of the page. I'm sure it has to do with the technical aspects of how sites are built but I would think translating on a forum should be fairly straight forward due to it primarily being text content. Good idea. Maybe it could even help me with English :)
 
hi friends. the first run and the second run is with dcnf 36. the first run with 4 gear and the second with 5 gear. i put foto with 40 dcnf later. idf carbs at 1000rpm if you put the gas at the floor the car go very very faster than dcnf 36 and dcnf 40.
 
Thank you Jim, now I understand.
Our "translation" comments above are aimed at finding ways to make it easier for everyone to enjoy the forum. We think a "translate button" feature would allow anyone to join the discussions without the difficulty of language barriers. But for now we will do our best to share with you. We appreciate the help you've given to explain things. Hope you are able to understand us as well. When I was in Greece the language seemed impossible to me, just trying to read street names was very crazy! But I loved it there.

It's great that you have access to a dyno unit. I believe it is the best way to get carbs dialed in.
The IDF's seem to work well for you. It's good that you have great response from 1000 rpm, especially with dual 40's. Often that much carb tends to bog a bit off idle. Your jetting and all related parts must be good.

There is another member that has done a lot of testing with heads, intake manifolds, carbs, etc. The Fiat SOHC engine is one of his specialties, plus he really knows about Webers. He has a flow bench at his shop and is very skilled at understanding it. I think you will enjoy reading what he has to say and see the work he has done (look at the link below).

We look forward to your other dyno results. Maybe send us a picture of your engine also.

Here is the link [see section "6" for carburetor discussion]:
https://xwebforums.com/forum/index.php?threads/ultimate-sohc-engine.22546/#post-183740
 
Jimgkioulis said:
hi friends. the first run and the second run is with dcnf 36. the first run with 4 gear and the second with 5 gear. i put foto with 40 dcnf later. idf carbs at 1000rpm if you put the gas at the floor the car go very very faster than dcnf 36 and dcnf 40.
Click to expand...
This is very interesting, to me. Have you taken to time to dial in the car, optimally, for each carb? I know this can be time consuming and a pain, but it is really the only way to determine what the best carb setup is, for the SOHC. Thanks for the info youve shared. I will use your base line when I set up my dual 36's.
 
Photos of you engine and carb set ups would greatly help also. That's for my and other newer members, benefit mostly as it seems you really know what you are doing. Another thing that would be cool would be a video of a dyno run; lets see this work in action!!!
 
for everything setup dcnf 36 tell me i know everything to tell you. i send dynometer with dcnf 40.the best and i go dyno to chec is idf 40. i think i am now 110hp. my false is only gearbox. 17 64 5 gear. very long. i think because peoples tell me 13 53 is very faster than and i go faster. 1 day i must do this.
dyna-sheet-1976 dcnf 49.jpg
 
Jim,
Comparing the dyno results shown here (with DCNF 40) and the results earlier (with DCNF 36), it looks like the 36's offer more HP up to about 5000 rpm, above that the 40's do better until they peak at 6500 rpm. So I guess it depends on what you use the car for...what kind of driving. Is more time spent steady above 5000 or more time spent accelerating from idle/low rpm? Either way those are pretty good numbers.

Regarding the transmission final ratio; 17:64 or 13:53, it also depends on what the main use is for. For drag race where getting off the line / acceleration is very important, then you want the 4.08 (13 53). But for driving on the freeway then you want the 3.76 (17 64).

Everything is always a trade-off; better in one respect means worse in another, and the other way around.
I think I've seen that you sell parts on eBay? You seem to do a lot of work on cars, do you have a automotive service business there?
Thanks, Jeff
 
Hello jimkgioulis
I am also running 40 IDF's from a 124. My engine is a standard x1/9 1500 with a 284 duration camshaft from dbilas. My jetting is 32 venturi, 125 mains, 175 air correctors, f11 emulsion and 50 idle jets. I had to close the accelerator pump return jet to stop the engine bogging at sudden throttle.
I am interested in what you think gives you the better low rpm torque is it the extra compression? I find I don't have much until about 3000 rpm.
 
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