ignition systems euro/us

[todds]

Hi, I was wondering if it is possible to replicate or approximate the ignition curve of a Euro (carbed) 2000 engine that has the bosch distributor on a US 2000 engine with its marelli distributor. I've seen the tuneup specs for both and the two are obviously different due to differences in the engines, such as carbs/fi and cams.

The static timing on all euro bosch distributors is 2-4 BTDC
on the us marellis it's a mix of before, after and at top dead center. Since this is set simply by the marks on the engine pulley, it's easy to replicate the euro models. Dwell is 60 for both (although point gap spec is different)

My question involves the rest of the curve, the max advancement spec is 27-33@5000rpm for the us marelli models. For the euro bosch models its 37-40@4600rpm. That's quite a bit more advance at a lower rpm, which would make a difference in top end power I would assume.

Even more importantly (to me) is low rpm operation because that's where I spend most of my time in traffic. The euro distributor seems to have different characteristics than the us models in this respect also, such as at which rpm the advance starts coming in, and how quickly it goes up or back down. Does anyone know anything about the low rpm specs of the euro vs. the us distributors? Anybody got a curve mapped out? I guess the only way to change these things is with either different springs or different weights. The other option is to source an original untampered-with euro bosch distributor with its original springs, anybody got one to sell me?

[papajam]

Welcome, Todd!

There's a bit of a discussion on dist advance in this thread that sort of talks about the same thing.
Not only is the total advance between the Euro and US dists different but so are the curves. Off the top of my head, for example, the Marelli S 103 B, as fitted to early US Spica cars, provides only like 7 degrees primary advance at 1400-1700rpm while the Bosch 044 Euro version gives almost double the primary advance of the Marelli at a lower 1200-1500rpm (or something like that). I'll draw up and post a graph later tonight when I can see what the specs actually are.
What model Alfa are we talking about?

[papajam]

Here's a couple of graphs of advance curves for some late '60s to mid '70s Alfas that were fitted with Bosch distributors in the Euro versions (the 041 and 044 in particular although an 045 was also used but I have no curve for it) and Marellis in the US. The difference in the curves is astounding.
I would think that a dist specialist or a hotrod shop could recurve your Marelli to the Bosch specs without much trouble. Or, as you say, just get a Euro Bosch dist. Although 'un-tampered with' Bosch units are out there, the 30 or so year old springs inside could be somewhat ummm....fatigued - as well as the bushings.

[papajam]

....and some Bosch curves.

[todds]

Thanks papajam, that reply was excellent! Very useful information. I've attempted to recurve the marelli with a slight bit of success but I think the real solution is to just source the original alfa distributor with the correct curve for a euro-spec setup. Unfortunately these things seem to be pretty hard to find (understandably) in the US. I suppose another concievable setup would be the one from the later bosch injected spiders. I don't suppose you know the advance curve for those do you? I think the reason these might work is that as I understand it, they are totally seperate (seperate ECU controller) from the fuel injection. I'm thinking all that would be needed besides the dizzy and coil off a junker would be the silver (or is it the black) box and assoc wiring. These would be easier to find in the US. Then again, perhaps the advance curve on those isn't a whole lot more useful than the marellis. They must be a more powerful /longer serviced overall setup though.

[todds]

Actually, now that I think a little more about it, those Euro spiders had webers pretty late in the 80's. Did they retain the same bosch 041/044/045 type points distributors as they had in the 60's and 70's or did they too go electronic at some point? Same system as US bosch injected 80's spiders with different curves perhaps??? I guess a more simple question is, Did the 80's euro spiders with webers still have points?

[papajam]

Well, the short answer to all this would be to consider the electronic ignition system, part # ID405, sold by www.centerlinealfa.com. It's a new Bosch dist with a modified advance curve but the specs aren't listed. I think I'll contact Centerline to see if that info is available. There's a discussion on electronic dists in this thread that you may find helpful as well.
To start the long answer, I don't have the advance specs for the VSZ ignitioned L-jet cars close at hand but I'll do a little digging. I'll wager a guess though that the curve isn't as aggressive as you're hoping for. And the Motronic setup is out of the question with the spark advance and fuel management being controlled by one ECU.
I can't find when the Bosch 045 was last used in the Euro cars but there's no listing for it the 1984 ignition book #PA3469B. What the book does list for 4 cyl cars is no less than 7 different distributors; 4 Bosch, 2 Marelli and one Ducellier. Three have points, three are electronic and one is Motronic. Except for the Motronic dist, all were fitted with vacuum advance diaphrams and the max total advance listed is 33 degrees.

[DriverJon]

Uh, Papajam...

I was wondering how to tell which of the two curves are which on those graphs..

Got a Marelli S166B on the 77 Spider..

Anyone know what the "B" difference is?

--

OK, read the other thread, and that answered most of my other questions..

[GTV4EVR]

A previous owner installed a Marelli-Plex in my 74 GTV. Since this was a performance upgrade way back in the 20th century, I have always assumed it would have a more agressive curve. Does anyone have the actual specs?
Thanks..........

[turbolarespider]

If you can manage to find a copy of the Ricambi catalog, it has most of the distributors available for Alfas. They are the same as what Jim is posting...

The difference between an S 166A and S166B is enough that they shouldn't be called the similar numbers... Max advance on an A- 18 deg, B- 14. Adv at 1000 dis rpm(2000 engine)- A- ~9, B- ~7. Ok, perhaps not that much different, but different enough.

If we didn't just upgrade our computer system here at work, I would scan both pages and post them. Thanks to progress, we no longer have a working scanner...

Oh, the Marelli Plex is almost identical to the 166B.

If you had a distributor bench, some springs, and a good book on how to blueprint and tune distributor curves, you could easily do it youself.

But I would probably by the upgrade offered by Centerline or RML http://www.rmlautomotive.com/

Eric

[papajam]

Here's the S 166 B curve. It is, IMO, strictly for an emission engine and the least desirable distributor for a performance engine.
The two lines in each graph are the upper and lower tolerance range of the manufacturers specs. The actual spec is an imaginary line somewhere between the two.
I'll take a guess that the 166 A is a single point and the B is a dualpoint.

[todds]

Cool, these posts are great papajam! Where are you getting these graphs from anyway? It seems none of these older dist's had vacuum advances, the "curves" are strictly linear only varying when the heavier spring starts expanding along with the light. The dist's you described in the '84 book all had vacuum advance right? Is that desirable on an alfa engine? I know for ultimate bragging rights on HP and top-end accel all that really matters is total advance but I'm talking driveability and throttle response. I imagine a carefully planned out curve with vac advance would more closely match ideal engine requirements for regular driving, provided of course the full advance is still there for when my webers are opened wide and I'm enjoying that characteristic sound. (kind of like chewbacca except down a few octaves)

[turbolarespider]

Todds-
Interesting question. Although I should have know this, but it turns out that Jim is the AROC USA Technical Librarian, right Jim? I JUST noticed that in the "Owner" I recieved yesterday.


So, if you are a member of AROC USA, I'm fairly sure that for the cost of copying and mailing, you can have copies of any technical manuals that AROC owns. I think that is right- Jim, can you correct me?

Eric

[John M]

Just to second what Eric said of buying centerline or RML. I went with RML for my distributor in my 78. It came with the correct optical output for my MSD multispark 6AL. Very plug and chug so to speak. Starts out at 6 degrees advance at idle. Adds in another 30 degrees by 3000-3500rpm for total advance of 36. I cannot say that I have noticed a big difference in throttle response. I got the majority of that when I went to the MSD multispark box. But I can say...no ping on high compression pistons. Maybe starts a little easier. Seems to have a little more acceleration. But the real advantage is its supposed to be troublefree. No points to worry. And its fresh built as compared to the 25 year old marelli that was in there!

Best Regards,
John M

[todds]

Hmm, RML eh? Sounds alot like a bosch unit with an optical trigger.. I know their "low end" setup goes for more than $300 which includes the ignition box and coil. Did you strike up a deal with them for just the dizzy since you already had the MSD? I suppose I ought to ante up for the MSD at some point. My goal is to get the best possible curve going first, then add an MSD or equivalent. I wonder if a stock 80's bosch FI dizzy will run an MSD... hmmm (wheels turning)