New Member! & Question

Polariscsl

Polariscsl

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Hi All,

I have been a long time visitor to this forum but decided it was time to introduce myself. Firstly though I have to compliment the forum because it certainly is a wealth of knowledge run by true enthusiasts.

I am the proud owner of an early CSL that was the lucky and needy recipient of a 5 year ground up restoration. (I will post some pics when I figure out how).

My key issue at the moment results from me converting it to triple webbers recently. The linkage side is bespoke and perfect in its operation but I am struggling with what I should do on the igniton/ distributor side. Currently the car runs quite rough on part throttle and pops quite a lot. I am running the stock vac advance distributor, lumention electronics and magnecor leads. The vacuum advance is currently not connected. I have searched the forum and found many solutions to this - basically I wan to sort this with the best solution possible and want to be sure before i throw money at the problem as always seems to be the case with CSL's.
Do i need a fixed advance distributor like a mallory with some form of electronic ignition? or would it be better to just fit a mapped ignition like an emerald or omex?

The key problem that i face is a lack of expertise setting up webbers - I know more about mapping modern ecu's.... [/img]
 
I don't have any experience setting up tri-Webbers but popping is usually an indication of a lean condition. Ignition timing can also cause popping but it has to be out a lot to get that. Cross firing could also be a possibility but not likely if it only happens at part throttle.

Since it only happens at part throttle I suspect the carbs are going lean. I hope someone that has experience with your set up comes along to give some better specific advice.
 
Cheers, you may be right there...

I have had a couple of 'experts' look at it and each have failed to set these up properly - I just want to make sure that all the right parts are in situe just in case I am asking the impossible of a specialist that doesn't specifically know how this conversion works. If the concensus on here is that setup is basically ok it is just a question of finding the right person to set it up properly on a dyno - which is another problem......
 
You need a real pro to help. Many think they can handle weber dcoes, but very few really can. Also, getting tripple webers to run well is a lot more difficult than a dual weber setup on a 4cylinder engine (for a number of reasons that I won´t get into)

The only company in ths US I know of that seams to have real experience with tripple webers on the M30 is korman (kormanfastbmw.com). They sell a complete kit and probably have some advice on jetting.
To get the carbs to run really well though, you usually have to get to a rolling road and an expert for the jetting. There just are too many variables...

As for the ignition, tripple webers don´t work with the vac advance, so having it disconnted is right. make sure to leave the vac line open at the distributor side.

Also, a tripple weber setup usually requires a higher idle speed (about 1000rpm) and a different advance. static 18deg and about 20deg advance at idle would be right. your standard distributor will probably be closer to 10deg at idle. Important: if you forward the static advance though to 18 deg, you will get too much advance at higher revs and therefore pinking. So the mechanical advance of your distributor will have to be modified (limited).

Of course, a fully electronic ignition that is mappable is very nice, but keep your money, you´ll need it for other bits. The M30 is a very robust and simple engine. A slightly modded standard distributor will work fine, even with points. If you don´t like points, the pertronics ignitor wll work fine and is cheap.

You didn´t mention what webers you are running 40s or 45s. For road use, the 40s are usually better.

Other questions:
was your CSL a carb or a D-jet motor? (different compression). have you done other mods to the engine (cam, compression, exhaust)?

What size chokes are the webers on, whats the jetting?

Some books to get into the subject of the weber dcoe:

http://www.amazon.de/Build-Power-Tu...ie=UTF8&s=books-intl-de&qid=1215710222&sr=8-1

And igntion on carbd cars:

http://www.amazon.de/Build-Distribu...e=UTF8&s=books-intl-de&qid=1215710312&sr=1-20
 
Sorry, didn´t see you were in the UK. So korman is probably not of much help to you.

There should be plenty of dcoe experts in the UK. Popular with the classic car crowd on MG´s, Triumphs, Jags and even Rover V8s. But very few BMs.

If all else fails, there´s a company in germany, in Cologne that´s been in the business for 50 years and has lots of experience with Weber setups. I have a manifold on my m30 for 3 40dcoe that was made by them in the 70s for the 2800. I´ll be on their rolling road at the end of august to have my jetting tuned. If that goes well, I´ll post and maybe a hop to germany might be worth your while. Have your CSL tweaked and then have a run in it´s natural habitat...

The company is called viktor günther (vgs) and really, whenever you mention webers to anyone handling classic cars in germany, they all reply: you´ve got to go to Viktor Günther, only he nows...

http://www.vgs-tuning.com/
 
Polariscsl:

You might read Dave Andrews' excellent write-up on Weber jetting at: http://members.aol.com/dvandrews/webers.htm

Dave's tables all pertain to 4 cyl engines with one choke/cylinder, so you'll need to multiply your BMW's displacement by 2/3 - that is, if your engine displaces exactly 3.0 liters, then you effectively have one-and-a-half 4 cyl, 2.0 liter engines.

As others have written, your problem probably stems from carburetor jetting and not ignition. For starters, leave your distributor alone with the vacuum line disconnected, and concentrate on carb jetting. Your symptoms are a pretty classic problem with Webers - the carbs transition from the idle jets to the main jets at 3,000 - 3,500 rpm, and stumbling often occurs at that point.

Make a note of all of your jet sizes, as well as the chokes and aux venturis. Go through Dave Andrews' methodology, and see how closely your current jets correspond to the recommendations from his charts and formulae. A little off is OK (I have found his recommendations to result in rich jetting), but you want your jets to at least be consistent - if some jets are on the rich side of his recommendation and others on the lean side, then you will definitely have problems. Of course, you also need to ensure that all 6 barrels have the same sized chokes & jets!

Fine tuning needs to take place on a rolling road with an exhaust gas sensor. No book or computer program can figure out the correct jetting for a specific engine/car.
 
Thanks guys - thats a great help. As it happens I have spoken to Korman and they are helpfull but there is only so much they can advise over the phone!! They say the Mallory distributor is the best by miles but far from cheap at $650 plus

These are the current settings - where the last 'expert' got to before I took the car back:

45 Webers
Fuel pressure 3psi
34mm chokes
Idles: 55F8
Main:160
60mm trumpets (currently open - but 83mm deep K&N's have been advised)

The engine was originally injected - it has been completely rebuilt - and has about 3000 miles on it so far


one problem they were having was a slight timing variation between cylinders circa 1/2 degrees - i would have thought this was down to a physical distributor issue....

One they wanted to do was to reconnect the vacuum advance with a throttle mounted switch so that the vacuum retard is cut the moment the throttle is opened (like aston DB6's)

Any thoughts on this information
 
The main jet seems very much on the big side. With 34 chokes (which would have fit in the 40DCOE btw), I´ve run 130 and 140 jets on the 3.0 Liter. 55F8 für the idle jet is rich as well. You may just as well be running too rich as too lean. What do the spark plugs look like?

Do you know the procedure of spark plug cutting? Cheapest rolling road there is...

The throttle switch thing sounds clever, but since the vacuum advance is ONLY for fuel economy, I´d wait to play around with that until I´ve fixed the basic running issues. Till then you can just leave the vac advance disconnected.
Keep it simple...
 
Thanks again - i will be keeping it simple at this stage!! I don't know about spark plug cutting though?!

As it happens the garage tried 135, 145 main jets and said it popped worse but have said that smaller air correctors may be necessary...... but i have little faith in them....
 
Without previous experience I was lucky to reach a fairly good result with Dellortos (DHLA45) on a 3.5 Alpina engine, after initial problems looking very similar to yours.

This did not require that I reduce the total advance.
But I may have been helped by the fully hemispheric head, which can take more total advance than a stock head.

Poping while having apparently rich jets could indicate a problem somewhere else. For example:

Are you sure your setup is 100% leak free ?
Your problem could be the result of air being sucked between carbs and manifold (or between manifold and head), resulting in a lean mixture.

What fuel pump and regulator are you using ?
A fuel pump delivering too little volume (starvation) is another possible cause.
In my setup I was initially unable to get rid of pops without using very very rich jets (180 main instead of 160 !!!), until I realized that one Facet Red Top was simply not enough.

Now I am using two Red Tops in parallel and everything is OK.

I hope this helps.
 
Hi chaps,

The car is running a lot better now I have swapped the idle jets and rebalanced them- could anyone that is running these carbs on a 3.0 engine please let me know what size jets/ venturis you are running? It would be usefull as a comparison.

Thanks very much for your help so far
 
What did you rejet to? Leaner or richer?

For comparison watch this space. I´ve got a rolling road appointment for rejetting my 3.0 Liter on tripple 40DCOEs next Thursday. I´ll post the resluts if my gearbox doesn´t blow up on the run (it´s been very noisly lately and getting worse...)
 
Take your car to Jaymic or Munich Legends, they will fix it.

Now I hope you are not "offended when you read the follwing:

Pay whatever they charge (it'll be fair market, they are reputable and bona fide experts in the setup you need.)

If it hurts, maybe it will be a lesson in monkeying with your car in a way thats outside of your (stated) expertise....
 
Thanks Tierfreund - they ended up marginally leaner at idle - I forget the size but it will come back to me!

@ dp - I understand your point and I have not taken offence at your somewhat blunt comment. I would like to point out that in an early post I did mention that I had already consulted alledged 'experts'. 99.9% of the work done to the car has been carried out professionally and very expensively and I would normally pay what is required to make it perfect - as numerous members of the car club will vouch! Now I am not about to name names, but my experiences thus far have made me very sceptical about some of the specialists.

Thus for my own amusement, and to expand my knowledge I wish to learn about this myself. Contrary to this I have had a place recommended to me that I will be investigating but I will still be trying to get my head around these carbs!!
 
Timing variation between cylinders?

Polariscsl said:
The engine was originally injected - it has been completely rebuilt - and has about 3000 miles on it so far one problem they were having was a slight timing variation between cylinders circa 1/2 degrees - i would have thought this was down to a physical distributor issue.... One they wanted to do was to reconnect the vacuum advance with a throttle mounted switch so that the vacuum retard is cut the moment the throttle is opened (like aston DB6's) Any thoughts on this information
Click to expand...

Your comment is puzzling. Do you have an oblong distributor cap? Did someone use an oscilloscope to determine timing variation between cylinders? If, on the other hand, you are referring to an erratic timing mark, that is something entirely different. Yes, a worn distributor or one with a points plate that is very sloppy can make for a less-than-rock-steady timing mark and an engine that runs poorly. But the same symptoms can arise by other ignition woes, including leaky secondary wiring, worn and/or misgapped plugs, a leaky condenser/coil. Same holds true for vacuum leaks, worn carburettors, poorly calibrated/jetted carbs, poorly set carb floats.

Maybe I have misinterpreted your distributor issue and if this is the case, read no further. I have used a mallory dual point distributor on an E3 with dual sidedrafts. There was no particular magic there. It performed well, but not much better than my re-curved bosch distributor. Before proceeding much further on your quest for perfect carburetion, I would want to start with a reliable ignition system - that affords a regular spark at each cylinder - notwithstanding your apparent need for a different advance curve. Again, I am not sure why you can't use the Csi distributor for starters. I cannot recall that distributor's stock advance curve specs, so I am not in a position to opine on its suitability for your sidedrafts. I do recall however, that mine had a simple vacuum retard that was fed by manifold vacuum. I would presume this vacuum, is available (even with the webers) considering you are likely using the same vacuum to feed your brake servo. I may be wrong, but I have a distinct recollection of seeing a 3X duce setup using that same bigger distributor. (Look at DP's posted picture which looks like a setup utilizing the bigger Csi distributor: http://www.e9coupe.com/forum/viewtopic.php?t=4018&sid=859b02e437e6d4d58cfb43a0287f0316 )

Unfortunately, too many experts affords each expert an opportunity to point the finger at the others, thus creating the need for work that may be otherwise unnecessary. Under the circumstances, I would stick with a reputable one and hold your breath. That being said, I would expect that anyone with general experience successfully setting up Weber side drafts, could be up to the job. Of course it can be very helpful to have previously performed the work on the same model so that the notes/experience provide a baseline and abbreviate the learning or relearning curve. Previous experience with an E9 is helpful, but not essential, if the party in charge knows what they are doing.

Good luck!
 
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