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  #1  
Old 07-08-2014, 06:41 PM
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Bosch ignition for S159 double distributor setups

Early 308 GT4/GTB/GTS cars with a double S159 distributor ignition setup are difficult to maintain as wear and age changes the advance curve of each distributor individually, e.g. both banks run with a slightly different advance which reduces a bit of power and smoothness of the engine.

To fix this i did an installation of a Pertronix MR-183 setup with two pickups in one distributor (the second distributor just distributes the spark in such a setup), as a result the advance curve for both banks is controlled by just one advance curve.
The engine ran a lot better but still not as smoothly as expected, so i benchmarked the S159 Pertronix setup on a distributor tester and found out that the difference in advance between the cylinders was up to 4-5. Bought another unit but had similar results, apparently the position of the magnets in the sleeve is not precise enough to yield better results.

After that i decided to adapt the Bosch high performance ignition setup i did for the Dino 246 some years ago, this setup uses a Lumenition Optronics OS50 optical pickup and a Bosch 0227100137 high power ignition module combined with the matching Bosch 0221122334 coil.

For the S159 setup, a full setup is required for each bank and both Lumenition pickups are installed in one distributor (i opted for the front one). The Lumenition #262 chopper wheel required for the optical pickup fits nicely on the S159 cam after a bit of sanding. The first Lumenition pickup has been installed in the position for the front bank (0), the second one for the rear bank is installed at 135 (a multiple of 45) starting from the first pickup, so with the #262 four cylinder chopper wheel each pickup serves one bank.

Testing the converted S159 distributor on the distributor tester yielded a cylinder difference of less than 1 :-) The engine ran very smooth after the installation and hot and cold starts were much easier compared with the old points setup. I also installed a fresh set of NGK BPR8EIX for best results.

This setup has a similar approach and precision as the very effective Marelli AEI200/Magnetic pickup setup in late GT4/GTB/GTS cars, but delivers 33% more power due to the higher coil current (and 100% more power compared to the factory points setup). It's a bit of work machining the adapter plate and wiring up the parts but it's quite worth the time from my experience. Also it looks quite original.

See below for pictures and the wiring diagram of the new ignition setup.
Attached Images
File Type: jpg 308 GT4 S159 Lumenition Conversion 3 small.jpg (214.4 KB, 285 views)
File Type: jpg S159 Double Lumenition Conversion.jpg (203.4 KB, 285 views)
File Type: png Bosch Setup Double S159.png (95.3 KB, 284 views)
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  #2  
Old 07-08-2014, 07:15 PM
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This is brilliant! Wonderful job Adrian.
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Old 07-08-2014, 07:20 PM
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Looks good- having access to a distributor machine is a definite plus.
Was adapting the Petronix base plate not a practical option?
Also, are the power stages out of something common? (answered my own question-1987 Saab 900, amongst others I suspect)

Cheers,
Tom

Last edited by tomberlin; 07-08-2014 at 07:25 PM.
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Old 07-08-2014, 08:16 PM
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Quote:
Originally Posted by tomberlin View Post
Was adapting the Petronix base plate not a practical option?
I was thinking the same thing.

I remember reading an early pertronix thread where people were making their own dual trigger setups and someone made one of the triggers in slotted groves to adjust for the very problem you are trying to solve.

Wouldn't it just be easier to do that? Maybe Fchat could get pertronix to build it that way. From the early pertronix threads it looks like Fchat got them to build the dual pickup model when they were just offering single pickups.

Not to take anything away from you but in terms of work load for a home mechanic, your solutions looks like a lot more than a simple mod to the pertronix.
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Old 07-09-2014, 01:16 AM
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Quote:
Originally Posted by tomberlin View Post
Looks good- having access to a distributor machine is a definite plus.
Was adapting the Petronix base plate not a practical option?
Also, are the power stages out of something common? (answered my own question-1987 Saab 900, amongst others I suspect)
The Pertronix base plate has different positions for the pickup screw posts so decided to start fresh and design a custom one.

The power stages have indeed been used for the Saab as you posted, as well as for a range of other cars (Audi Quattro and 200 Turbo, Volvo, VW) so they are easily available as spare. They are inexpensive, deliver up to 8 ampere to the coil (resulting in a nice long spark), have an electronic dwell management and automatically switch off if there are no incoming pulses, so no overheating of the coil as with the Ignitor I or points.

Quote:
Originally Posted by scowman View Post
I was thinking the same thing.

I remember reading an early pertronix thread where people were making their own dual trigger setups and someone made one of the triggers in slotted groves to adjust for the very problem you are trying to solve.

Wouldn't it just be easier to do that? Maybe Fchat could get pertronix to build it that way. From the early pertronix threads it looks like Fchat got them to build the dual pickup model when they were just offering single pickups.

Not to take anything away from you but in terms of work load for a home mechanic, your solutions looks like a lot more than a simple mod to the pertronix.
I fully agree, the Pertronix setup is much easier to install than the setup above (and half the price) but if you have to design a better magnetic sleeve to get the timing variance down to 1-2 it gets a bit tedious again. With the magnetic sensor design used in the Ignitor you have to fabricate a sleeve where the distance of the magnets to each other and to the pickup is within the fraction of a millimeter, so that might be difficult to achieve. In that perspective, an optical IR switch with a chopper wheel is a simpler to manufacture and more precise approach.

I wouldn't mind if a shop or manufacturer would adopt the design shown above and manufacture ready to install and prewired conversion sets, then it's really plug&play and you don't need access to a distributor tester. With the amount of double dist points based 308's there might be a market for this i guess.
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Old 07-09-2014, 01:39 AM
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Quote:
Originally Posted by alhbln View Post
Early 308 GT4/GTB/GTS cars with a double S159 distributor ignition setup are difficult to maintain as wear and age changes the advance curve of each distributor individually, e.g. both banks run with a slightly different advance which reduces a bit of power and smoothness of the engine.
This setup looks fantastic, however I disagree with your statement above.
After testing my dizzys on a machine, I found that they both advanced EXACTLY the same. The problem is the points and the dwell changes from age/miles which then changes the ignition timing, not the advance curve for a specific RPM.
So your single source of firing would definitely be an advantage to keep the two banks sync'd, and then of course, smoothness and HP is maintained.
Keep up the good work!
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  #7  
Old 07-09-2014, 01:55 AM
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Quote:
Originally Posted by GT4 Joe View Post
This setup looks fantastic, however I disagree with your statement above.
After testing my dizzys on a machine, I found that they both advanced EXACTLY the same. The problem is the points and the dwell changes from age/miles which then changes the ignition timing, not the advance curve for a specific RPM.
So your single source of firing would definitely be an advantage to keep the two banks sync'd, and then of course, smoothness and HP is maintained.
Keep up the good work!
True, it all depends on the condition of your S159 distributors, if they are in very good shape (how many are? :-) they should align well, but i was looking for a difference of not more than 1-2. Points are also a factor as you said. See below how my distributors looked like after i bought my (otherwise well cared) GT4, the engine was feeling gritty at higher RPMs and was not very smooth when revving up so the first thing i did was to check out the advance curves on the distributor tester, with the curves shown below it's no wonder the engine was unhappy. All fixed now :-)
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File Type: jpg curves.jpg (70.0 KB, 249 views)
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