Weber tuning tutorial
 

I've been working on this tutorial as I have been tuning my car. As little information as there is out there about tuning IDAs, I though I would try to give back and increase the knowledge base a bit. I would appreciate any feedback and particularly anything that appears to be in error.

It's not done yet, but getting close. Any feedback is appreciated.

Tim

Hello Tim,

Hats off to you for putting this in writing in a manner in which (in layman’s terms) ordinary folks can understand the workings of the Weber 48 IDA carburetor. Your writing has put my thoughts into black and white as a comprehensive piece. Very well done in my opinion and very much needed for people struggling.

I did however find (I think a typo) a needed correction. I’m not trying to be a critic:

"For the size 55 jet, the area is 0.238 mm2. The size 55 jet is therefore 21.4% larger than the 55 jet and will therefore flow 21.4% more fuel."

Shouldn’t that read 50 jet? Again I’m not criticizing at all, just a correction.

Also I know you are refining this wonderful piece. The (4) illustrations (towards the end) of the emulsion tubes and gas flow; could show the Main Jet against the body. It currently illustrates gas going up the Main Stack Well as opposed to flowing through the jet.

Lastly here is a photo on my Main Jet stack with fuel flow stains on my emulsion tubes, you can use the image if it helps any.

http://www.clubcobra.com/photopost/d...s/DSCN7487.JPG

Best Regards,
Earl

Earl:

Thanks so much for the comments. I appreciate any input. Yes, that is a typo with the jet sizes. I'll fix that. That's also a good point about the crappy drawings at the end. I'll see if I can improve them. I appreciate the pics too. I'll p[ut it in my library and work it in if I can.

Tim

Tim,
That's going to be one very informative and brilliant website once its fully finished. I haven't had a chance to read it all, but I'm far from qualified to correct your work :o so apologies for not being able to contribute. :CRY:
I've book-marked it for future use, and look forward to seeing your build and website evolve. Thanks for sharing!!

Dimis:

Thanks. There won't be much more evolution of the build site, since the cars is done. I will keep working on the tutorial, though.

Tim

weber article
 

Hi Tim. I hope you got the reprint of my magazine article I sent you. You have a wonderful website, as I said directly over the telephone. Your car came out great in addition. I sent the link to the Weber guy in Chicago who has worked on the 48's and 58's on my engines for almost 30 years. You used an O2 sensor for your testing. His dynomometer is a T bucket with a weber carbureted small block and another with a Weber big block, for ease of service/tuning. He calls it his seat of the pants dyno. He has spent over 40 years running the devil out of that car trying combinations , recording data, and making changes after change after change. Thousands of hours. His combinations have eliminated popping, smoking, fouled plugs. That never happened on the engine dyno with my engine, with his intial set up, and never in the car. The horsepower numbers just got better and better as he continued with minute changes on the engine dyno for days. There is no progression cross over stumble at all. Pulls straight through in third gear from 1200 to 7000. Not much load though, as the tires are spinning most of the way through. The best idle with a four barrel that we could get was 1300 rpm, before he arrived. After manifold change and adding the Webers, idling was now at 900rpm with 280 @ .050 cam and right at .700 lift. As soon as he saw your idle fuel jet / idle holder discussion he knew you were closing in on correct concepts. I'd like to arrange a three way telephone conversation to discuss your progress, and probably expedite your end point .Thank you again for adding and helping so much to the Weber lunatics here in the Cobra world.

Nice work! I breezed over it. I'll give it a full read layer today. Glad to see someone put forth the effort!

patty442:

Yes, I got the article. Thanks so much. It's truly incredible.

I have learned that the use of an O2 sensor is only one tool and nowhere near as helpful as it is for tuning EFI. It is virtually useless for idle and progression, particularly with a cam with a lot of overlap. It will typically show too ruch, even when actual combustion chamber conditions are too lean. It can be very helpful in tuning the main circuit, though, at least help to make sure that conditions aren't dangerously lean. I intend to revise the tutorial to reflect the good and bad of using a wideband sensor based on my experience. What I am finding is that the "old school" techniques (plug cuts, sniff test, "butt dyno", etc.) seem to be the most effective when combined with some knowledge of how the carbs and their components work.

I would be delighted to participate in a conference call to discuss further. I think you have my e-mail. If not, you can use the e-mail feature here to drop me a line.

Thanks for your comments.

Tim

I noticed a few typos from "high-speed range" paragraph through to the end. Other than that a great read! I learned a few things. I always wondered if the Inglese tutorial was more of a joke than actual fact. I've read through that thing so many times & it always left me with more questions than answers. Your read is not for the faint of heart but, it's more like a semester course, everything is there.
About half way through, I was wondering if there was any way to shorten it. On the other hand, my initial thoughts were that this writing should be kept hidden away. After all, tuning of your weber setup is sort of a "right of passage". Many give up. In the end, I feel that it's a pretty tough read with a lot of concepts to grasp. If you don't have a pretty decent understanding of carbureton, you likely won't drop a set of Ida's on your motor, with this in hand & end up with a perfectly tuned set of carbs. Not that the info isn't there. It is! & it's probably better than any Weber guide I've ever read. It just takes a lot of patience(a lot of time also, in my case) to work your way through, the first time.
It is a great piece! Thank you for putting it together!

Tim,

A few days ago I read the latest and greatest addition to your excellent tutorial. So my natural question is: how much further do you intend to take it, and do you have any timeframe in mind for completion?

Great work.

Tim,
Awesome job on your Weber insite. Would the tuning procedure be similar for $$IDF's?
Thank you very much, Russ

OOPS, I meant 44IDF'S. Sorry

I'm pretty close. I still have some work to do on the main circuit and I intended to add a section on synchronization, and maybe a summary section. The timeframe is anyone's guess. I had intended to be done long ago, so who knows. I have had a lot of distractions at home and work in recent weeks, so I haven't had much opportunity to work on it. Hopefully I'll have it done in the next month or so.

Thanks.

Tim

Russ:

Tuning the IDFs will indeed be similar, though a bit simpler. Syncronization is, of course, the same. IDFs have a different idle circuit and control idle air with a bleed screw instead of a jet holder, so adjusting the idle circuit is simpler. The IDFs also use a diaphragm pump that is adjustable, so the pump shot is much easier to adjust too, though getting all 4 to have the same diaphragm adjustment can be tricky. Everything else - mains, air corrector, emulsion tube and venturi - follow the same principles as the IDAs.

Tim

Thank you very much, Tim.
Russ

Hi Tim,
Thanks for the great tutorial.
Speaking of IDF's, would you consider adding a section on them at some point?

Tim, you have obviously invested a lot of time learning the many nuances of the 48 IDA and put a lot of time and effort in sharing your knowledge. An excellent tutorial and my compliments on your logical writing style.

Very understandable, and thanks for your efforts!

I'll give that some thought. The only reason for any reluctance is that I have never actually tuned IDFs, I've only read about them. I'm not sure if I can give good advice without hands-on experience.

Tim