Lotus Elan

Weber Mainstack

PostPost by: type26owner » Tue Jun 28, 2005 3:43 am

Hi Sarto,
Unfortunately, I'm already committed to a family reunion up at Eagle Lake that Saturday of July 16. How about the next one Mike has though. The process takes about four hours if we haul ass. The time is consumed doing the swapping and sucking crud. I'm getting good at it though since I understand this stuff with an insight no one else has every had before. You're on! Suggest you call Pierce Manifolds and buy the Weber tuning manual for $25 and do some homework. I will use that manual as the foundation and explain how this stuff works in real terms. They also made a few gross errors I found.

On another note. My (gross pulluter) brother called a little while ago to tell me had passed the rolling road California Smog test today with flying colors with his 95 Caterham. Every item was a factor of ten less than the allowable except the HC (hydrocarbons). He was allowed 400+ and it was worst case measured at 25 mph at 115. Good enough! Now I've got Jon Rosner (Jon drove my car on Sunday) and my younger brother that now know I'm not full of it. My creditability has quickly expanded to two! :D
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PostPost by: type26owner » Tue Jun 28, 2005 2:52 pm

Sarto,
Hopefully your car has the stumble coming off idle, the flatspot at 3000 rpms and it runs out of power before reaching the redline. Am I close?

I have an optical fuel level gauge which I made this weekend in about an hour's worth of development time. It's simple to use and extremely accurate. If I can get it to you before the tech seminar then you could set the float bowl height and save us at least an hour of boring time. It's the very first adjustment that needs to be done. Maybe you could just make your own tool too once you see it.

When the bottom end of the acrylic rod gets slowly pushed down and wets to the fuel then top end turns slightly darker and that's your clue it's there. The split nylon sleeve slids along and marks the length for you. Just measure the distance from the sleeve to the end of the acrylic rod. The distance needs to be .98"+/-.03 (25mm). This gauge is a lot easier to use then the pipette. Come to think of it I've got several special tools I've developed to do this stuff. I wonder if there's any demand for tuning tools that make sense?

http://www-eng.lbl.gov/~franck/Car_Stuf ... n_Well.jpg
http://www-eng.lbl.gov/~franck/Car_Stuf ... _Gauge.jpg
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PostPost by: type26owner » Wed Jun 29, 2005 1:47 pm

Sarto,
Let's not wait for the next tech seminar that Mike's going to put on. I'm busy until after the GGLC Trackday on July 27 though. How about some Saturday after that?

Let me know which Webers you have. In order to establish the idle so it's perfectly smooth the airflow volume past the imperfect components must be balanced to a knat's ass. The early carbies don't have a way to do this other than drilling a bleed hole through the throttle plate. This is painful and from personal experience I know it takes two man days of hard work to do it. The obvious way to overcome this shortcoming is to provide an additional air bleed for each cylinder which has a needle valve arrangement just like the idle jets do. The place to do this is to build them into the o-ring carriers which compliantly mount the carbies. Since the amount of bleed air is tiny, the aperture is liable to get clogged with debris so a 5 micron air filter is also required. I'm planning on attaching the supplied air to a tap in the side of the air trumpets in someway which I've entirely figured out yet. Otherwise the air bleeding in can't be measured along with the flow going straight through. I'm going to make up a set of these for my own use. If you want a set too let me know and I'll double the quantity. They will not be free though but then again the cost will be quite reasonable. Four ~1/4" diameter holes will have to be drilled through the backplate of the airbox to allow for rubber hoses to connect the new manifold arrangement.

Come to the trackday with a helmet and ride along as my passenger. Then you'll know before I touch your carbies I've not overstated the tuning performance capable of the DCOEs.
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PostPost by: mac5777 » Thu Jun 30, 2005 12:30 am

Keith, this is what has happen today. Rich Kamp is rebuilding my differential with a new 3.55 R/P, replacing my new donuts with a CV axles and finally replacing my original 40 DCOE 18 with new 40 DCOE 151. I assume your technique will be effective even with new webers.
I would still be happy to video the process on new webers and maybe a second video with someone running the 40 DCOE 18.
From an old time inventor, I see a couple of videos, a book and a line of tools. Make money the old fashion way, marketing your knowledge.
Let's talk 707-481-6700
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PostPost by: mac5777 » Thu Jun 30, 2005 12:44 am

sorry for the duplication
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PostPost by: type26owner » Thu Jun 30, 2005 2:04 pm

I spoke to Sarto and have made arrangements to tune his Webers. The 151 type has the air bleeds built-in to correct the airflow balance at idle. The DCOEs on my brothers Caterham were also that type. Don't hesitate to tweak on those air bleed by-pass screws if necessary inspite of the dumb advice posted out there allover the web to not touch them or worse yet to close them all off completely. That's what they are there for, duh! The factory set those intially for the required idle speed that particular carburetor is to operate at only. Be nice if they told you what that idle speed was. :twisted:

Here's a clue. At least one air bleed will be completely closed if you've done the adjustment correctly. The point is you don't want to move the throttle plates even further away than necessary from the first progressive hole and be forced to get rid of the stumble off idle by using an even higher idling rpm. That really sucks!
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