123 Distributor Group Buy Thread, Replacement for NLA stock Dizzy's-Order 15 % Discount Options

[98101]

I think you're confusing a couple of things here. The stock dizzys, as I understand it, can have up to three forms of advance/retard, depending on your model.

1. Vacuum advance, which is just the initial advance to help with acceleration and throttle response at low engine speed. Not all 914 throttle bodies have a port for this, and I think the later 2.0 models actually did away with it.

2. Mechanical advance, which is the primary method of advance to "optimize" timing up to about 3000 RPM, when it maxes out.

3. Retard, to reduce emissions at idle.

You've got carbs and I don't know your setup, but the 1-2-3 does all this precisely based on a programmable advance curve because it "knows" the actual engine speed. The vacuum advance and mechanical advance were the engineers' best tools available back then to estimate engine speed and attempt to optimize timing at different engine speeds / conditions. They did an amazing job, but these tools wear out over time and become less accurate. This system is more accurate AND it can easily be changed based on your needs/preferences.

Hmm, point taken that the 123 can sense RPM more accurately than the centrifugal weights and springs in traditional distributors -- and this is a good thing by itself. But I don't see how manifold vacuum could be a proxy for RPM. What I'm reading elsewhere suggests manifold vacuum is related to engine load.

According to this GM engineer:

The key difference is that centrifugal advance (in the distributor autocam via weights and springs) is purely rpm-sensitive; nothing changes it except changes in rpm. Vacuum advance, on the other hand, responds to engine load and rapidly-changing operating conditions, providing the correct degree of spark advance at any point in time based on engine load, to deal with both lean and rich mixture conditions.

As I understand the article, manifold vacuum is higher when the throttle plates are closed, lower when they are open. (This effect is reduced somewhat by high-lift long-duration cams.) They will be closer to closed during lean conditions (at idle, or cruising at a steady speed). We need an earlier spark because lean mixtures burn more slowly. With the richer mixture at open throttle we need a later spark to get combustion happening at the ideal time. (Otherwise would we get pinging like my Bosch 009 914 tended to do in hot Phoenix years ago?) If I'm reading this right, we'll get closer to the ideal time to fire the sparkplug by combining vacuum information with RPM information, as the 123 is capable of doing... effectively a 3D map.

Example I in a 123 manual discusses how to emulate a "Bosch-distributor 0.231.170.034 for Volkswagen" which is sensitive both to RPM and vacuum. I'm just figuring this stuff out myself, but my guess is that lots of stock distributors for lots of cars used both RPM and vacuum.
http://www.123ignition.nl/files/manuals/12...al_TUNEPLUS.pdf

[BeatNavy]

You are correct in that manifold vacuum is lowest at wide open throttle, higher at part load, higher still at idle, and highest on overrun (high RPM, closed throttle). In a stock 914 (D-Jet anyway), the mixture is managed primarily by the MPS / ECU based on these conditions.

Someone else can do a better job of explaining how it's done with carbs, because that's more of an "art." Having said all that, you have to determine the best advance curve based on your specific setup. That means a combination of setting / jetting the carbs the way you want them and programming the advance curve on the 1-2-3 the way it makes the most sense for you for different engine speeds. Because I have D-Jet where mixture is controlled by other sensors, I have basically 4-preprogrammed options available to me.

The article you reference makes sense for understanding the theory of optimum advance, but primarily for non-electronic systems.

[914_teener]

You are correct in that manifold vacuum is lowest at wide open throttle, higher at part load, higher still at idle, and highest on overrun (high RPM, closed throttle). In a stock 914 (D-Jet anyway), the mixture is managed primarily by the MPS / ECU based on these conditions.

Someone else can do a better job of explaining how it's done with carbs, because that's more of an "art." Having said all that, you have to determine the best advance curve based on your specific setup. That means a combination of setting / jetting the carbs the way you want them and programming the advance curve on the 1-2-3 the way it makes the most sense for you for different engine speeds. Because I have D-Jet where mixture is controlled by other sensors, I have basically 4-preprogrammed options available to me.

The article you reference makes sense for understanding the theory of optimum advance, but primarily for non-electronic systems.

Almost makes the case to go back to fuel injection (IMG:style_emoticons/default/poke.gif) ... (IMG:style_emoticons/default/laugh.gif)

[echocanyons]

Almost? (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/stirthepot.gif)

[98101]

Almost makes the case to go back to fuel injection (IMG:style_emoticons/default/poke.gif) ... (IMG:style_emoticons/default/laugh.gif)

Trying to get the carbs to work seemed the cheaper option in my case... but I'm not sure that will turn out to be true in the long run.

[rhodyguy]

Aftermarket dual throttle body FI $ is going to make your head explode. (IMG:style_emoticons/default/blowup.gif) better make sure the cam in your engine supports fuel injection before you step over the cliff. You can tame the carbs for a lot less.

[Porschef]

Kevin, your comment is so true, and it's only for a lack of market (I do suppose) that a kit has not been created (to the best of my limited knowledge) for T1&4 engines. When I see some members here struggle to assemble/debug their aftermarket systems, it keeps me from taking the plunge (well, that, and the aforementioned $$ issue). Is there such a thing? I see Micro/Mega,SDI, maybe another out there, but as far as I can tell, there's no true soup to nuts, bolt on plug and play system out there...

I had to pass on the 123 group buy, I'd been wanting to start a thread on the satisfaction quotient for those who purchased them, but likewise, it seems that all bugs have not been worked out as yet. (IMG:style_emoticons/default/confused24.gif)

[BeatNavy]

I had to pass on the 123 group buy, I'd been wanting to start a thread on the satisfaction quotient for those who purchased them, but likewise, it seems that all bugs have not been worked out as yet. (IMG:style_emoticons/default/confused24.gif)

I'm very happy with mine at this point. My "bugs" were primarily from confusion about which advance curve to select. This was partly because my D-Jet setup was a little cobbled together previously (my original dizzy wasn't correct for my car, which I didn't even know at the time). I wouldn't hesitate to recommend it for someone who's looking at this product for their teener...

[StratPlayer]

Best replacement for the oem dizzy. I've been running mine well over a year now and its flawless. D-Jet 2056. Late model

[98101]

I had to pass on the 123 group buy, I'd been wanting to start a thread on the satisfaction quotient for those who purchased them, but likewise, it seems that all bugs have not been worked out as yet. (IMG:style_emoticons/default/confused24.gif)

I haven't heard of any bugs with it. I'm pretty excited about its advantages over the 009 it replaced in my car.

[Porschef]

Michael, I wasn't inferring bugs with the units themselves, just figuring out what curves to use. The Bluetooth is an awesome setup.

Are you satisfied with it's performance? I've got a 205A (I believe) dizzy and I'm sure it's the last foible in my tuning process... (IMG:style_emoticons/default/dry.gif)

[rhodyguy]

FWIW. That '205' can be misleading. Looking at the handy AA catalog, if your complete # is 039 905 '205A' that is for a 2.0 engine. Djet. A better dist for carbs is 022 905 205AB. Ljet.

[Millerwelds]

After running mine for awhile I noticed a few things. 2.0 FI. Car used to stumble when cold starting. It would start, start to increase rpm, hiccup and would stall if I did not goose the throttle a bit. Now it does not do that at all.

Idle seems a bit higher (I have yet to actually set the timing as it runs so good I am just going with it till I get a little more time to play around). I will likely adjust idle down a bit for now and really set it in summer when it 100+ again. In the past when at top of the heat range it would drop the idle very low and want to stall. Which meant idle at cold start was pretty high to over adjust for that. I suspect that will go away once all dialed in now too.

Pulls very good. Pulls higher into the rpm range with less effort.

So far very happy. (IMG:style_emoticons/default/beerchug.gif)

[914_teener]

Kevin, your comment is so true, and it's only for a lack of market (I do suppose) that a kit has not been created (to the best of my limited knowledge) for T1&4 engines. When I see some members here struggle to assemble/debug their aftermarket systems, it keeps me from taking the plunge (well, that, and the aforementioned $$ issue). Is there such a thing? I see Micro/Mega,SDI, maybe another out there, but as far as I can tell, there's no true soup to nuts, bolt on plug and play system out there...

I had to pass on the 123 group buy, I'd been wanting to start a thread on the satisfaction quotient for those who purchased them, but likewise, it seems that all bugs have not been worked out as yet. (IMG:style_emoticons/default/confused24.gif)

(IMG:style_emoticons/default/agree.gif)

No bugs.....no points....no problems so far....I have driven the snot out of my car since I have installed it....even it over 100 degree temps. My car is bone stock D.jet.

Wish I put it on the dyno before and after...but mine seems to pull faster as well into the higher rpm range.

[rhodyguy]

Are the 123 internals as delicate as the pertronix and like setups or the even the
Mallorys?

[914_teener]

Are the 123 internals as delicate as the pertronix and like setups or the even the
Mallorys?

They look more robust to me....I don.t know about Mallory.

[rhodyguy]

Maybe I should say forgiving.

[914_teener]

Maybe I should say forgiving.

You mean like leaving the key on due to Alheimers forgiving to see if the electeonics burns up?

Haven.t developed it yet. Just in case I kept thenstock dizzy in tje car for now.

[pete000]

Maybe I should say forgiving.

You mean like leaving the key on due to Alheimers forgiving to see if the electeonics burns up?

Haven.t developed it yet. Just in case I kept thenstock dizzy in tje car for now.

I don't think the 123 has a burn up problem if you leave the key on with out the engine running like the Pertronix and such. They make no mention of this anywhere.

[Porschef]

I'll have to check on that Kevin. I am running Ljet on a 2056 with a 9550 cam. I would like, no, really like to eliminate the pinging under hard acceleration at higher rpms.

This way, I could completely put my foot in it whenever... (IMG:style_emoticons/default/biggrin.gif)