Bosch Distributor Mechanical Advance Limiting Screws

['76mintgrün'02]

Today I had a go at making a spring loop bending tool, using a crusty old pair of pliers. 

 

They're an interesting design that are made of stamped/folded sheet steel.  That made slotting one jaw for the plunger adjustment pretty easy.  I started with that part and then added the second screw as a depth stop.  The anvil side was a little trickier to figure out; trying to get the angles right, based on photos of the tool in that video I posted above.  It is just clamped in place to be able to give the tool a try... quick and dirty like.

I had a  little  success after a  lot  of fiddling with it, but there is room for improvement.  It definitely needs a hardened screw for the plunger.  This one is just soft stainless steel.  That lower anvil piece should be hardened too.  The top one needs to be an adjustable sliding stop, with a slightly steeper angle on both pieces.

It's fussy work, trying to get the same length spring cut off the piece, with the cuts done symmetrically on each end.  There is the option of a half turn of wire variation in length, in order to get loops bent on the same plane. 

 

This one is quite close to one of the originals I have here.  Repeating it is not easy, yet.

The darker spring in that photo is the thickest 'spare' I have on hand and the bulk-length-stock is a little bit thicker.  It makes a much stronger spring, unfortunately. 

 

I compared those two springs on the Bausch & Lomb scale, with the weights set at 60 on the ruler.  The new spring measured 8.8mm and the other one dropped clear down to 10.2mm.  

It will be interesting to see how well this tool works on the little tiny springs in the early style distributors.  

 

Tom

['76mintgrün'02]

Speaking of springs... @uai and I have gotten into a discussion about how the springs in a late style distributor work together to affect the curve, but it is a tangent in another thread that has to do with the early style distributor; so I am going to pull a quote, hoping we can continue in this thread.

 

This is the thread that the following quotes came from

https://www.bmw2002faq.com/forums/topic/264521-another-weber-dcoe-post/#comments

 

uai offered this nice graph of our curves--

 

So red is about yours, and blue is for for engines with more compression and more cam.

So when you have it at 10° btdc at idle <1000 you'll end up with 32° at 3200 rpm.
As the 292 is still mild and I don't know the compression you should end up in between but do not have advance below 1000 rpm and a steep curve at the beginning

 

 

To which I replied --

 

I was getting some pinging in the low rpm range when the curve was close to the one you drew in red, so I brought the looped spring in sooner, which flattened it out, as seen in green (approximately) and that fixed the problem.

 

 

uai-- 

 

"Tom, there is also a part where the first weight Touches the second and helps to move the second weight. When limiting travel on the first weight it will flatten the curve too. But you surely figured that out already."

 

------------------------------------------------------------------------

 

.... and here we are, discussing this type of weights/springs

 

When I limit weight travel, I try to do it as symmetrically as possible, to keep things in balance and that will also keep them both pressed up against the center post.

 

 

The way I see it, both weights are doing the same job all the time.  Meaning, they both swing out simultaneously, working against the foot at the bottom of the center post; while the springs act independently, to vary the tension between the shaft's plate and the center post.

 

I refer to the springs as the "loop spring" and "idle spring". 

 

I see two ways to vary the tension they provide.  One is to modify the length of the spring itself and the other is to change the position of the outer attachment point.  It is at this point that I would like to include the photo that uai shared in the other thread that shows his beautiful post bending tools.   

 

 

It makes me happy knowing I am not the only one having this kind of fun.  

 

Tom

 

[dlacey]

I learned a lot from this thread on how to dismantle & service these Bosch distributors, I also bought a bunch of small springs on AliExpress to try to recover the advance curve... But how to test? I couldn't find a SUN distributor tester here in Malaysia (there must be, but I can't find) ... So I thought I should try to make something to test centrifugal advance and vac advance... 

Here's my creation, made out of some scrap bits of steel, a few bits of AliExpress robotics pulleys, bearings and belt -  plus some old ignition components. 

The cam timing degree wheel spins at twice dizzy speed so with a strobe I can read engine advance directly off the scale. Initial setup of 'TDC' is done by sliding the magnetic pointer around on the base to point at zero while the dizzy is turning at 500rpm....after that I can use the variable speed controller to record the advance curve.

In the vid you can't see the strobe because the digital camera doesn't like flashes...but with the human eye the degree wheel is easy to see with very little scatter. It's got a V8 dizzy under test there, but works well with Bosch units too.

 

 

['76mintgrün'02]

On 2/28/2021 at 1:42 AM, dlacey said:

I learned a lot from this thread on how to dismantle & service these Bosch distributors, I also bought a bunch of small springs on AliExpress to try to recover the advance curve...

 

This was such an awesome post.  Thank you for sharing it in this thread.

 

Would you mind sharing which springs you bought and how they worked out for you?

I'd be excited to read more about your tester and how you brought the distributor back into spec. 

Which distributor model did the TURBO have?

 

 

I've looked through the McMaster Carr catalog and they have a few sizes that might be applicable, but I only looked at the bulk spring section; figuring I'd need to customize the length.

 

I tried adjusting the spring loop bending tool I made to do the little ones that come inside the early style distributors, but I need to make a new tip for the pusher.  I used a stainless steel screw and it is not hard enough to stand up to the forces involved on the large springs and not pointy enough for the small ones. 

 

I'll make a new one and try to harden the screw once it has been shaped.  I think I'll make another tool, so I have one set for the small springs and another for the larger ones in the late style distributors.

 

I really want to get back into messing with distributors and your post was very inspiring.

 

Thanks again,

Tom

[dlacey]

Hey Tom,

 

The smallest springs I can find are these: 

 

I bought the 2 & 3mm OD, 10 & 15 mm long ones, i must admit I havent tried to use them yet on a Bosch, but I have been successful in 'recurving' a Lucas 20D8 with slightly heavier springs.

 

I bought one 123ignition dizzy and, as many others report, it transformed my tii... rock solid idle and pull up to redline without pre-ignition....this was an eye-opener on how bad my Bosch dizzys were.

 

On my tester with a 008 tii dizzy I found the advance coming-in far too early I used pliers to bend the spring posts outwards to the limit of clearance on the body, that shifted the advance curve back closer to the the factory spec...i am currently running that and its better but not perfect...next step will be the above springs.

 

The turbo 014/026 is a weird thing, it has vacuum retard ....the advance curve is completely illogical given all I have learnt about turbocharging... I use the 123ignition dizzy here, programmed same as I used when fitted in my tii, but with the addition of boost retard (1 degree retard for every 2psi boost). The turbo runs very nicely, and using the 'PerfExpert' app on my cellphone it estimates 185HP at flywheel.... we discussed timing for turbos over in turboland here : 

 Still learning here, and I truly believe its possible to revive our Bosch dizzys to get good performance at a fraction of the cost of a 123 - I know Bluetooth app programability is nice now, but I worry that in 10 years time no device is gonna be backward compatible.... and the 123s become useless bricks...but our mechanical Bosch units will go-on for another 50 years. Parts for the bosch units are getting harder to find, the fibre washers are available and the 'sliding plates' can still be found at a few specialists in europe, but the Bosch rebuild/shim kits have gone stratospheric ... I hope we can find an Aliexpress spring combination that economically revives factory advance.

[dlacey]

Whilst idly googling BMW part numbers, I stumbled on a Singapore parts site offering Bosch dizzy advance springs for $0.87 each...so I bought 6 pieces..they turned up today...they look pukka:

So now I can compare old vs new and maybe identity an AliExpress spring with similar properties...

[ray_]

6 hours ago, dlacey said:

Whilst idly googling BMW part numbers, I stumbled on a Singapore parts site offering Bosch dizzy advance springs for $0.87 each...so I bought 6 pieces..they turned up today...they look pukka:

So now I can compare old vs new and maybe identity an AliExpress spring with similar properties...

I hope those springs stabilize your idle googling!

 

???

['76mintgrün'02]

 

 

This came up for sale on Facebook marketplace yesterday.  I saw it this morning and expressed interest, but that was eighteen hours after it posted.  Someone beat me to it and got a heck of a deal at $150.

 

Unfortunately there was an error in the closeup photo of the gauges.  The one on the left is an Acroset Volt/Amp meter, the one next to it is a Trouble-Shooter condenser tester.  In the middle there is a Coil Master.  Next to that is the Dwell meter / Tachometer and on the far right is a Mixture Master combustion indicator.

 

There would have been a scroll here with information for various vehicles.  Wouldn't it be cool to make a new one that covers all the 2002s?!

 

 

It's probably good that I did not get it.  It was way over in Toby's neck of the woods, in Carnation.  Maybe he's the one that bought it! 

Tom

 

Edited July 5, 2021 by '76mintgrün'02
Damn text eating glitch.  That was painful to retype. I need to remember to copy, then post, so I can edit back in easily. Slow learner, I guess.

[Lorin]

New purchase?

 

 

 

EDIT:  Your post makes a lot more sense with the text added back in !

Edited July 5, 2021 by Lorin

['76mintgrün'02]

"New purchase?

EDIT:  Your post makes a lot more sense with the text added back in !"

 

Ironically, the glitch did it to me again.  I thought maybe the problem went away with the recent site changes.  Unfortunately, not.  Time to re-type the text.

 

I brought these home yesterday.

 

 

I had left them in the store when I saw them the first time, in part, because they were missing the cords.  When I got them home, I discovered that they only use two wires and a standard wall plug fits perfectly. 

 

 

I will just cut the end off and add a couple of clips.  (The person who put the price tags on them thought it would be a good idea to put clear packing tape over them.  I used a heat gun to soften the tape, trying to avoid pulling paint off.  It worked well on the first two, but not this one.  That was a bummer).

 

 

This cord is from an old boom-box and the other end almost fits the power supply pins.  The original plug must have had a tab that fit the slot, to orient +/-.  I don't know which is which yet.

 

 

I opened them up to see the pretty-bits inside.  They don't make them like this anymore.

 

 

 

 

The clear-backed vacuum/pressure gauges are fun.

 

 

The vacuum gauge works.

 

 

Tom

 

Edited October 23, 2021 by '76mintgrün'02
the GLITCH is alive and well, after the recent site changes

[ray_]

Look at all those leaky condensers 

 

?

 

 

 

 

 

['76mintgrün'02]

1 hour ago, ray_ said:

Look at all those leaky condensers 

 

?

 

They're not leaky.  They're just moist!

 

This is the kind of wiring I can sort of understand. 

 

 

I just need to figure out which pin is positive, so I can make some power cords.

 

  It'll be fun to see them lit up.

 

Tom

[ray_]

Well I bet that equipment harkens back to the time before polarized plugs, so I'd wager it makes no difference.

 

['76mintgrün'02]

I think they require 12V input.  I suppose the bulbs would light up either way, but the other fancy bits might have a +/- preference.

 

They did not come with instructions.

 

 

[ray_]

Well. That's a horse of a different feather! 

 

;-)