I hate my Carbs Much Less, Chris Foley is a God! |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
I hate my Carbs Much Less, Chris Foley is a God! |
Mblizzard |
Oct 30 2013, 12:13 PM
Post
#1
|
Advanced Member Group: Members Posts: 3,033 Joined: 28-January 13 From: Knoxville Tn Member No.: 15,438 Region Association: South East States |
Well after much playing and changing I have to say I hate my carbs. I have done every jet size and I can't really get it to run well on anything but 70 idle jets and that is way to rich. With 60s it runs not quite as rich but the hesitation on the initial throttle is huge.
Have played with the adjustments and I think I have it running well but it never performs well. 2056 just built, 44 IDFs, 60 idle jets, 28 vents, 135 mains, F-11 emulsion tubs, 175 air correction jets. Timing at 27 to 30. SVDA Dizzy with electronic ignition. Valves recent set and rechecked. Synced at idle and 1500 rpm. Runs well at higher rev and pulls strong but I can't get rid of that hesitation. I know there will always be some but at times from a dead stop it almost stalls. What am I missing? (IMG:style_emoticons/default/headbang.gif) (IMG:style_emoticons/default/headbang.gif) Gone through all of the Weber tech trouble shooting steps and I can't find anything that says I have something wrong. Is there an adjustment on the accelerator pump? Or do I need to up the accelerator jet? I will be going back to FI at some point but these carbs should work better than they do. Taking it to Eurohaus tomorrow maybe they will have better luck. Suggestions? |
DBCooper |
Oct 31 2013, 11:48 AM
Post
#2
|
14's in the 13's with ATTITUDE Group: Members Posts: 3,079 Joined: 25-August 04 From: Dazed and Confused Member No.: 2,618 Region Association: Northern California |
Yeah, I don't think it's the barrel size, at least not in my experience. Think about it. The job of the carburetor is to atomize fuel, and that happens because of the vacuum created under the venturis. On 40 and 44 IDF's the bowls, jets and passages are identical, so with the same venturi size they create the same vacuum and work, mixing fuel, exactly the same way. Volume/velocities going through the venturis are determined by the engine, the heads, displacement, runner size and cam, not by the throttle plates. Size of throttle plates does make a difference at full throttle, but in every other instance when throttle plates are only partially opened so their overall diameter is mostly irrelevant.
I've used 44's with 28mm venturis on a nearly stock 1.6 engine, used 48 IDF's with home made 30mm venturis on a 1776cc engine, worked great. The hot VW guys all run 48 IDA's on 2 liter engines, standard practice. I've also used 36 DRLA's on stock 2 liter engines. Not exact comparisons, sure, but barrel size (and throttle plate diameter) isn't the determining variable in atomizing fuel, it's venturi size and then sizing everything else accordingly. I agree with that Painted Guy, everything depends on everything else, so if anything's out of whack it seems everything's off. What you have will work, and it will work well, so you just need to go through it to get everything set up in balance. Unfortunately when you find something that's out that means you need to go through the whole list again, since everything depends on everything else. When you have more experience you can jump over steps, but until then you just have to grind it out. As a hint, look long and hard at the linkage and synchronization, because that usually ends up being the problem when multiple carbs run sour. |
Lo-Fi Version | Time is now: 2nd June 2024 - 11:05 AM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |