I started to crack open this subject on a prior thread:

[corvaircenter.com]

but I thought I'd start a whole new thread here to capture the lengthy discussion that this message might generate.


What's motivating this inquiry is my consideration of replacing my existing stock distributor with either:

(1) CB Performance Black Box + replacement distributor: allows for arbitrarily complicated advance function based on rpm and manifold pressure

(2) 123 Ignition Products distributor: replicates, in a tunable fashion, the simple Advance = Function1(rpm) + Function2(pressure) of the original distributor

I don't have a "complicated" Corvair engine. No turbo. Just a 140PG.


Yes, I know that the complete flexibility of programming of the Black Box sounds good on paper. kmart365 was kind enough to offer a 3-D programming table as a start in the other thread, but this table is essentially a 3-D representation of the simple traditional mechanical advance + vacuum advance of the original distributor. The same control scheme could be implemented with the 123 distributor.

I don't have access to a dyno to try to systematically improve on kmart365's simple table.

So, let me boil this down to a few questions:

(1) For a "simple" carbureted engine like my 140, is the flexibility of a 3-D table even worthwhile or necessary (I mean are there any advantages beyond the simple one of being able to separately set the base and all-in timing, which you can already do with a 123 distributor, or equivalent).

(2) If a 3-D table is of value, how should a simple transcription of a traditional mechanical+vacuum curve be tweaked? What parts of kmart365's table would be worth looking at more closely? And how would I figure out how to modify without a dyno?


Terry

1966 140 Monza PG convertible
Ventura County, CA

programmable timing is worth any frustrations you may encounter. you do not need a dyno you do need good hearing tho , I have tinnitus constant ring tone and can no longer hear ping so a dyno or a friend with good hearing is nessesary for me. what you can do is start with 365 map and then use a stop watch on country road. the first thing you must do is get base line tests before black box install and make sure it is fully warmed up. make small changes like 2 degrees at a time , I would do 0 to 60 for max power , then steady cruize with some gentle excelleration like going up a hill not a mountain. try to duplicate all of your driving conditions

Roger R
Madison Wi
63 greenbriar
65intercooled 180 4sp,autocrosser
62 Rampy

Terry, does 123 have a distributor that would work with a Corvair?

vairTer Wrote:
-------------------------------------------------------
> I started to crack open this subject on a prior thread:
>
> [corvaircenter.com]
>
> but I thought I'd start a whole new thread here to capture the lengthy discussion that this message might generate.
>
>
> What's motivating this inquiry is my consideration of replacing my existing stock distributor with either:
>
> (1) CB Performance Black Box + replacement distributor: allows for arbitrarily complicated advance function based on rpm and manifold pressure
>
> (2) 123 Ignition Products distributor: replicates, in a tunable fashion, the simple Advance = Function1(rpm) + Function2(pressure) of the original distributor
>
> I don't have a "complicated" Corvair engine. No turbo. Just a 140PG.
>
>
> Yes, I know that the complete flexibility of programming of the Black Box sounds good on paper. kmart365 was kind enough to offer a 3-D programming table as a start in the other thread, but this table is essentially a 3-D representation of the simple traditional mechanical advance + vacuum advance of the original distributor. The same control scheme could be implemented with the 123 distributor.
>
> I don't have access to a dyno to try to systematically improve on kmart365's simple table.
>
> So, let me boil this down to a few questions:
>
> (1) For a "simple" carbureted engine like my 140, is the flexibility of a 3-D table even worthwhile or necessary (I mean are there any advantages beyond the simple one of being able to separately set the base and all-in timing, which you can already do with a 123 distributor, or equivalent).
>
> (2) If a 3-D table is of value, how should a simple transcription of a traditional mechanical+vacuum curve be tweaked? What parts of kmart365's table would be worth looking at more closely? And how would I figure out how to modify without a dyno?
>
>
> Terry

'66 Monza coupe
4 speed
140hp
Gardner, KS

Heart of America Corvair Owners Association

chris-

No, 123 does not have a distributor yet that has been successfully demonstrated for the Corvair.

You can read about the challenges I faced with trying to install a Gen 1.0 version about 10 months ago:

[corvaircenter.com]


The main issue was their approach of trying to supply a new hold-down bracket, which didn't do a good job of securely holding the distributor.

They have just shipped a Gen 2.0 version to me that uses the original Corvair hold-down bracket instead. I will report on this one in an upcoming thread. Stay tuned...

1966 140 Monza PG convertible
Ventura County, CA

An important advantage with the CB performance Blackbox is that ANY Corvair distributor can be used, you just lock the advance mechanism. With the 123 approach, it looks like you have to use one of their distributors. A 3D approach to ignition timing is better than a 2D approach, although you can get pretty close
with a programmable 2D set-up. To get the most out of a programmable 2D set-up, your base timing that is standing in for the mechanical advance will not be a straight line, it will have an outward "bow" or curve to it. This gives different advance rates depending on the rpm. With a straight line advance, the advance rate is the same for all rpms until the max advance. The result of the variable slope is that the engine will tend to accelerate harder from low speed, this is because you are getting the vacuum advance timing to act differently at certain rpms than at others. A 3D timing approach gives the effect of each rpm its own vacuum advance curve and will further enhance the acceleration from low rpms. Carburetor or not! Its extremely difficult to manipulate the stock vacuum advance can in a way that makes power. This is because for it to work well at light loads to give good fuel economy and good throttle response, it has to add way too much timing in one situation (part throttle cruise) and take it all out, too quickly to avoid pinging when slamming the throttle. The other bug with stock mechanical VA is that it was developed in the 1960's using leaded gas.

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

Kevin Nash
Friday Harbor Washington
63 Spyder, Daily driver, EFI read about my project here: [corvaircenter.com]
first test start on EFI here:[www.youtube.com]
first official EFI boost test here:[www.youtube.com]
My new fan! [corvaircenter.com]
engine less 62 Spyder
Canadian 64 Monza Parts car
Test Start#2 [www.youtube.com]

What type of pulse output does the "123 distributor" supply? What does the CB performance Black Box expect - or what does it prefer? Doesn't the Black Box have a MAP input?

Seth Emerson

Check my new Performance Corvair Web site: [www.perfvair.com]

Located in lovely San Jose, California

Gotcha Terry; good luck with version 2.0! Seth, I think you're correct that the Black Box has a MAP input (if my memory serves me correctly).

'66 Monza coupe
4 speed
140hp
Gardner, KS

Heart of America Corvair Owners Association

Just to be clear here: I'm not looking to mate a CB Black Box to a 123 distributor. The choices are either: (1)the 123 distributor alone as a complete drop-in replacement for the original distributor, or (2) the Black Box mated to a non-programmable, locked-out distributor.

What I'm probing at is whether the more comprehensive programmability of (2) gives much of a usable advantage over (1).

Kevin has pointed out nicely that the improvement in low-rpm acceleration that can be obtained by using a non-linear rpm-advance gives more advance at lower rpm's and then tapers off when maximum advance is reached. But, as he mentions, this programming advantage can be obtained with either (1) or (2). The 123 distributor can be programmed with a non-linear rpm-advance, just like the Black Box.

Kevin is hinting that the full 3-D programmability effectively lets you have a different vacuum-advance curve for different rpms. Sounds good in principle but I don't have a good sense of: (a) how much better performance can be realized, (b) under what driving conditions the improved performance will show up, and (c) how to figure out (short of semi-blind trial and error) how to modify the 3-D timing table to achieve specific performance improvements.

I need someone to chime in with specific tangible performance improvements that can be obtained (is the only place for improvement during low-rpm acceleration?) with 3D programming and how to figure out how to tweak the 3D table.

Otherwise, the 3D programming sounds like it provides an unrealizable benefit of uncertain value (to a user with a non-turbo engine)...

1966 140 Monza PG convertible
Ventura County, CA

The realizable tangible benefit with 3D timing is that at higher rpms and speeds is that if you were to stand on it, that super trick programmble 2D VA curve that was optimized for best acceleration is going to be a ping monster, and to solve that the VA curve needs to be a flatter slope. If you do something to the 2D to fix that, the engine wont accelerate as hard as it can, the 3D curve will be flatter so wont ping from hard acceleration but will still be adding some timing as long as theres vacuum. Theres other ways to do this... in the past before 3D timing, some manufactures had a big outward bow to the timing below the torque peak timing, but then retarded the timing from there. And the vacuum advance would either add or retard. Which is silly, and likely to have a flat spot feeling as the throttle is slowly opened. Which is why they don't do that anymore!!
In summary, 3D timing gives fuel injection like responsiveness by giving the engine the timing it needs in the vacuum area, and does stuff that cannot be done well with a 2D approach. It is NOT "just for turbos".

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

Kevin Nash
Friday Harbor Washington
63 Spyder, Daily driver, EFI read about my project here: [corvaircenter.com]
first test start on EFI here:[www.youtube.com]
first official EFI boost test here:[www.youtube.com]
My new fan! [corvaircenter.com]
engine less 62 Spyder
Canadian 64 Monza Parts car
Test Start#2 [www.youtube.com]

Kevin-

Thanks for providing that example. It makes perfect sense. It would be nice to be able to back off on vacuum advance at high rpm.

I wonder if anyone has ever compiled a history of ignition timing approaches over the past 80 years. Then newbies like me wouldn't have to try to unearth it with the help of sages like you.

Terry

1966 140 Monza PG convertible
Ventura County, CA

vairTer Wrote:
-------------------------------------------------------
> Kevin-
>
> Thanks for providing that example. It makes perfect sense. It would be nice to be able to back off on vacuum advance at high rpm.
>
> I wonder if anyone has ever compiled a history of ignition timing approaches over the past 80 years. Then newbies like me wouldn't have to try to unearth it with the help of sages like you.
>
> Terry

This is the best I have been able to find [www.motorera.com]

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

Kevin Nash
Friday Harbor Washington
63 Spyder, Daily driver, EFI read about my project here: [corvaircenter.com]
first test start on EFI here:[www.youtube.com]
first official EFI boost test here:[www.youtube.com]
My new fan! [corvaircenter.com]
engine less 62 Spyder
Canadian 64 Monza Parts car
Test Start#2 [www.youtube.com]