Pertronix Alfa Distributor ?? - Alfa Romeo Bulletin Board & Forums
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post #1 of 24 (permalink) Old 02-19-2011, 05:27 PM Thread Starter
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Pertronix Alfa Distributor ??

Hey, does anyone have experience with the Pertronix distributor ?
Any idea what max advance is and the curve ?

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post #2 of 24 (permalink) Old 02-21-2011, 04:06 PM Thread Starter
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Question

Here is the advance curve for the pertronix distributor.....
Doesn't really look right for an Alfa....
Attached Files
File Type: xls AB_curve.xls (21.5 KB, 389 views)

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post #3 of 24 (permalink) Old 02-21-2011, 04:24 PM
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Petronix Alfa Distributor

Quote:
Originally Posted by 101/105guy View Post
Hey, does anyone have experience with the Pertronix distributor ?
Any idea what max advance is and the curve ?
Randy,

Brian, Ossopedia, who no longer participates on the bb had experience with them and could probably answer your questions. I'm not sure if he still has an e-mail available through the bb or not.

HTH.

Cheryl
(Not an authority nor SME on anything, just PATSYF)
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post #4 of 24 (permalink) Old 02-21-2011, 04:28 PM Thread Starter
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I'm not sure that Brian used just the Pertronix trigger....
this is for the complete distriburor which is a new product from what I can tell.

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post #5 of 24 (permalink) Old 02-21-2011, 05:58 PM
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I had assumed that Petronix just made those little units that replace just the points in existing distributors. But a little surfing at pertronix.com got me to: Electronic Distributors for Alfa Romeos where the text reads:

"We are please to announce the release of Flame-Thrower plug n play distributors for Alfa Romeos. These cast distributors feature Ignitor technology and are a direct replacement for Lucas, Bosch, and Marelli original distributors. They are availble in both vacuum and non-vacuum advance style and are compatible with both carbuerated and Spica fuel injection only.

Applications are as follows: 1956- 1981 4-cylinder 1300, 1600, 1750, and 2.0 liter engines."


Their online store prices it at $297.95.

Randy: Where did you find the reference to the advance curve?

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post #6 of 24 (permalink) Old 02-21-2011, 06:18 PM
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I have plotted out alot of advance curves for 4 cylinder Alfas and I have not seen one anything like that. I think that it might be hard to get a consistent idle with that curve and Webers.

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post #7 of 24 (permalink) Old 02-21-2011, 07:19 PM Thread Starter
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Hi Jay,
I asked a dealer about the specs and he emailed the graph.
I tried to compare those listed in the Shankle cataloge to this one and it seems close to a V6 curve.
Maybe this is a curve for the vacume advance model ?????

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post #8 of 24 (permalink) Old 02-21-2011, 07:24 PM
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Pertronix "Alfa" Distributors

I do not really know what they have done or actually I sort of do know. As others have done an air cooled VW distributor, many possible version, will fit in a 4 cylinder Alfa engine if you swap out the drive cog for a custom made drive. So what most people have done, including Pertronix is take a VW distributor (Type 1) with 11 degrees distributor degrees (22 deg crank) advance maxing out at at 2500 rpms or the newer distributors with 12 degrees advance (distributor advance or about 24 or 25 degrees crank degrees) so that at about 10 degrees static you approach 36 degrees advance minimum needed for 2ltr Alfa to work very efficiently at anything near the maximum power range somewhere about 5000 rpms. Some of the older cars like a 1300 Veloce were quite different and a Marelli distribor from a 1972 car had a lot of advance starting at about 5 degree atdc and thenl running somewhere around 36 degrees for a total advance of over 40 degrees on the crank, this was to address a smog problem issue.

Using one of these distributors and starting at 10 def. btdc from the total advance aspect you approach the needed total. There is an issue in that old stock VWs only rev'd to about 4000 and the distributor is at full advance at about 2500 to 3000 rpms. So if you have some cams with some cam overlap on your Alfa it all may work ok on depending on the compression ratio and the gasoline. The reason the advance curve looks strange is because it is very different than an Alfa curve. I was curious to see if what people were doing with these things and if they were have pinging problems which is not a good thing for piston lands and rings or under a real load other problems. The hemi Alfa pistons are quite durable. So the distributor is fine, the problem is that the distributor only has one spring on it that allows the distributor to advance too quickly and then there is not enough mechanical travel to provide the need advance curve. It needs to be reworked to a good curve. Depending which distributor you have you need about 16 degrees in distributor (32 crank degrees ) so setting idle at at 4 to 8 degrees and the advance curve needs to slowed down a bit to a good broad power band and approach 38 degress. If you have a 2 liter car with a US stock 4.56 9/41 ring and pinion by the time you let the clutch out the and go anywhere in 1st gear the car is at 3000 rpms and these distributors are at full advance.

A 2 ltr will spin safely at 7000 for a short bursts and most Alfa distributors do not reach full advance until l around 5000 rpms. I am certain that the stock Alfa curves are conservative on the safe side so there is not too much advance too quickly to cause problems.
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post #9 of 24 (permalink) Old 02-21-2011, 08:08 PM
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Il Mito:

Yea, that explanation makes sense. Pertronix probably does a lot of volume in distributors for air-cooled VW's. So, just swapping the drive cog, and calling it an Alfa Romeo distributor is probably good business. The fact that the advance curve is totally unsuited to an Alfa doesn't seem to bother them.

Taking the spreadsheet & chart that 101/105 guy posted, and swapping the X and Y axes gives the kind of advance curve that we are used to seeing. That is, with RPM on the horizontal axis, and degrees advance on the vertical. See the excel file attached below.

If I were going to spend $300 on a new, electronic distributor, I'd get a Centerline IE405. Same price, and it is engineered for an Alfa - not a VW.
Attached Files
File Type: xls Pertronix Curve.xls (21.5 KB, 255 views)

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post #10 of 24 (permalink) Old 02-22-2011, 04:27 AM
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This curve is quite steep at normal idle rpm and that will most likely cause problems, at least with Webers. The Shankle curve has the same problem. A little increase in rpm cause an increase in advance which causes more rpm.... positive feedback. You end up with an engine that will idle at a very low rpm or one that is too high but will not settle down to any rpm inbetween. My enthusiasm for the 123gnition is fairly well known. The advance curves are digitally programmed and they do not depend upon springs and weights. The 10 or so unique selectable curves were all designed for different Alfa engines.

Ed Prytherch
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post #11 of 24 (permalink) Old 02-22-2011, 09:52 AM
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Quote:
Originally Posted by alfaparticle View Post
My enthusiasm for the 123gnition is fairly well known. The advance curves are digitally programmed and they do not depend upon springs and weights.
I agree with you 100% - in the 21st Century, relying on weights & springs to create an advance curve is pretty primitive. Heck, my watch has 10X the computing power necessary to generate an advance curve.

On the other hand, the 123 distributor does cost $120 more than the distributors from Pertronix and Centerline, and while the 123 offers the choice of several curves, they are all single input (just based on RPM), and they do not necessarily include the curve that the engine builder prefers. It would be great if 123 built a distributor that accepted a user-programmable curve, and used MAP or TPS as an additional input.

Megajolt is a better solution, though it is a bit of a "science fair project".

Jay Mackro
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'67 Duetto
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Last edited by Alfajay; 02-22-2011 at 09:57 AM.
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post #12 of 24 (permalink) Old 02-22-2011, 10:27 AM
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. . . It would be great if 123 built a distributor that accepted a user-programmable curve, and used MAP or TPS as an additional input. . . .
Half of your wish? (Latest Version of the 123 with USB input)
Appears to be able to switch between two preprogrammed curves on the fly through the control of a single input.

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post #13 of 24 (permalink) Old 02-22-2011, 04:03 PM Thread Starter
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If price were the only consideration, the Pertronix distributors are new on ebay for $190.
A nice price if they worked right.....

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post #14 of 24 (permalink) Old 02-22-2011, 04:42 PM
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Each one of these distributors has fans and detractors. I strongly recommend that prospective buyers spend half an hour searching the ABB threads about them.

Ed Prytherch
79 Spider
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2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #15 of 24 (permalink) Old 02-22-2011, 05:53 PM
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Quote:
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If price were the only consideration, the Pertronix distributors are new on ebay for $190.
A nice price if they worked right.....
Ah yes, I see that Ponderosa Mustang of Pensacola, Florida (honest - you can't make this stuff up!) is selling them on ebay for $190. Odd that they are priced $100 higher on Pertronix' own website.

See: Pertronix Distributor D185604 1956-81 Alfa Romeo - eBay (item 360345697182 end time Mar-20-11 16:46:27 PDT)

It's nice to see the mainstream suppliers of aftermarket parts, like Pertronix, offer items that fit Alfas. Prices can be more reasonable than parts from boutique suppliers, availability good, etc. It's a shame that Pertronix didn't take the trouble to tailor the advance curve.

Jay Mackro
San Juan Capistrano, CA

'65 Guilia Sprint GT
'67 Duetto
'91 164L

Last edited by Alfajay; 02-22-2011 at 06:24 PM.
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