Discussion on the Future of CDI Boxes

[VFR750]

This thread: cdi-msd-done-thanks,was very informative, but got me thinking on what is the future of our 911s when it comes to electronics. I did not want to hijack his thread, so I started a separate one.

Most here are familiar with the red MSD CDI boxes. The referenced thread discussed the installation of a MSD Streefire. A good one, too. There are many other threads that discuss who to do it, and the modifications needed. Plus, he availability of reproduction plugs from Timmy2 makes the wiring that much easier.

Plus there are some spectacular options for street & racing listed here for sale at Pelican Parts. Including the beautiful twin-plug distributors. There are multiple re-builders of the Bosch units available via Pelican Parts. Factory refurbished too.

But now there is Classic Retrofit and their direct drop in, modern CDI.
Per "911 & Porsche World" December 2015, pages 106-109, there is a great write up on Jonny Hart and Classic Retrofit. A lot of thought went into the cdi+ box.


But, I have to think, as my 911 transitions from a track car to a truely historic car, and the value goes up, retaining a stock looking interior and hardware becomes more important. And the originality drives the value. The double edged sword of affordability and value; Can I afford a valuable car?

Msd might be the near term solution, but I think perhaps the cdi+ will be one of the long term solutions as it will enhance the perceived originality.

A MSD programmable costs $375. But a $150 streetfire does most of what I want. The Electromotive XDi makes sense too, especially for EFI conversions. But it is not even close to stock looking.

The ~$1400 (995 pounds sterling) CDI+ does it all and is "stock" in all the critical aspects except internal modernness. It compares cost-wise very well with a factory refurbished CDI box, and frankly the newer electronic design and programability make it function better than NOS.

Is $1400 now, a better investment, compared to $150 to $375 now (plus the cost/time of the required modifications), and then change to something else 6 years from now, when my SC turns 40 and I want to undo it all and go back to stock?

[gamin]

CDI+ is not the only game in town. ************ makes new fully modern CDI boxes and ignition transformers for significantly less than $1400. Their CDI box for your SC is about $800. I have their 3 pin box and transformer in the 70 and it works fine. Check it out.

[Jonny H]

Originally Posted by gamin

CDI+ is not the only game in town. ************ makes new fully modern CDI boxes and ignition transformers for significantly less than $1400. Their CDI box for your SC is about $800. I have their 3 pin box and transformer in the 70 and it works fine. Check it out.

We have to be careful comparing these solutions. Yes, the Parts Klassic unit is cheaper than ours but is also basic in comparison. It doesn't appear to be microprocessor controlled, doesn't have a programmable advance curve and has to be bought with a preset RPM limit which I would guess is a 'hard ignition cut' limiter.

It is my belief that nearly all 911s can be made to run better with timing adjustments than when they were new. Why? Well, it is mostly down to fuel quality which is much better these days. Also, if you have changed anything on your engine (fuelling, cams, headers, exhaust) you are definitely missing a trick not having the timing setup on a dyno.

I perhaps haven't made this clear but our cheaper 'basic' unit is exactly the same as the 'advanced' unit. Microprocessor accuracy with input delay compensation, hard, soft and launch rev limiters, tacho cal, shift light, dual spark etc. It just doesn't come with the diagnostic cable or software support. You can, however, still have a curve setup by an approved shop that has our kit. You can also have the diag cable fitted at a later date which makes the same as the 'advanced'.

Click here for full technical manual

It is our hope that once we have enough dyno feedback, we can ship our basic unit pre programmed with an optimum timing curve for your 911 dependent on engine spec.

Oh, and yes, our unit is still half the price of an original unit from Porsche which are on six month back order last time I checked!

[mysocal911]

Originally Posted by VFR750

The ~$1400 (995 pounds sterling) CDI+ does it all and is "stock" in all the critical aspects except internal modernness. It compares cost-wise very well with a factory refurbished CDI box, and frankly the newer electronic design and programability make it function better than NOS.

Really? And what is the basis for that statement, i.e. "make it function better than NOS"?

[wwest]

Originally Posted by Jonny H

We have to be careful comparing these solutions. Yes, the Parts Klassic unit is cheaper than ours but is also basic in comparison.

It doesn't appear to be microprocessor controlled,

And the advantage to this is....????


doesn't have a programmable advance curve

Again, the advantage is...??

and has to be bought with a preset RPM limit which I would guess is a 'hard ignition cut' limiter.

[B] "Our" cars use a fuel cut technique to limit RPM, inherently easier on the engine vs ignition cut with HIGH fuel flow remaining..

It is my belief that nearly all 911s can be made to run better with timing adjustments than when they were new. Why? Well, it is mostly down to fuel quality which is much better these days. Also, if you have changed anything on your engine (fuelling, cams, headers, exhaust) you are definitely missing a trick not having the timing setup on a dyno.

I perhaps haven't made this clear but our cheaper 'basic' unit is exactly the same as the 'advanced' unit. Microprocessor accuracy with input delay compensation, hard, soft and launch rev limiters, tacho cal, shift light, dual spark etc. It just doesn't come with the diagnostic cable or software support. You can, however, still have a curve setup by an approved shop that has our kit. You can also have the diag cable fitted at a later date which makes the same as the 'advanced'.

Click here for full technical manual

It is our hope that once we have enough dyno feedback, we can ship our basic unit pre programmed with an optimum timing curve for your 911 dependent on engine spec.

Oh, and yes, our unit is still half the price of an original unit from Porsche which are on six month back order last time I checked!

My '78's factory CDI is bought and paid for already, has been repaired once, $150... And I see/have little reason to buy a $1400.00 item, or even one at 1/3 that price, with doubtful performance advantage.

[wwest]

On the other hand, I see a real opportunity...

A modern day implementation of the Kettering inductive ignition system to be housed in the factory CDI box, marketed as kit including ad E & I core transformer type coil.

It's pretty obvious to me upon reading, and as a participant in, Jonny's post series, that the inductive system, using modern circuit design, will provide a much hotter, longer duration spark.

So, Jonny, why not go back to the drawing board..??

Could an E & T core coil/transformer be designed having the factory coil "look"..??

[Jonny H]

Originally Posted by wwest

It doesn't appear to be microprocessor controlled,
And the advantage to this is....????

The zero crossing detect in the original Bosch design introduces a timing delay as you go up the rev range. This equates to about 3 degrees in lost advance @ 7000 RPM. If you were to adjust +3 on the dizzy in the traditional manner to get the advance back, your idle would be stupidly high.

The microprocessor compensates for this inaccuracy over the rev range which results in an accuracy better than 0.1 deg @ 10000 RPM.

Originally Posted by wwest

doesn't have a programmable advance curve
Again, the advantage is...??

1) The 911 (and hence its advance curve) was designed against the fuel of the day which was very poor. Today we have high octane fuel and we also like to tune our engines. Ask any tuner, it is common knowledge that fuel mixture and timing are key to the performance of any engine. This should not be brought into question on this thread, it is a given for any device that offers a programmable timing curve.

2) Some timing curves are physically impossible to achieve. We had a highly strung race car that would not return to idle nicely. Mixture adjustment didn't help. The tuner put in a little sine wave dip just above idle and the issue was resolved.

Originally Posted by wwest

My '78's factory CDI is bought and paid for already, has been repaired once, $150... And I see/have little reason to buy a $1400.00 item, or even one at 1/3 that price, with doubtful performance advantage.

Yep, the last two boxes we had in for gut and upgrade were 'repaired' so YMMV.

Here you go, see the 'repair', just waiting for the next 40 year old component to fail:



In this case the customer didn't want his Bosch case refurbed, so we left it warts and all:

[VFR750]

I proposed a discussion on the future of 911 electronics as we move from daily drivers and low cost replacements to rare/valuable/collector cars and the higher cost but stock like equivalents. Not a technical attack on a particular manufacturer with whom you disagree with.

In response to a direct question: I made my statement on "function" vs NOS based on the ability to program a rev limiter and to tweak the advance curve. Two significant improvements (functions) not available in the stock box. IMHO that's a huge benefit that can be used in the real world.

My reasoning:
I'm currently running with a rotor rev limiter. It's a little bit of a wildcard as to when it really kicks in. I also could use some more advance but the cost is $500 to get a rebuilt distributor, (which I don't need) I'd prefer programming it as it gives me control and the ability to change it.

So, for me, there is a strong case to start putting a $ value on looking stock, yet have modern performance enhancing features.

Anyone else starting to think this way?

[Jonny H]

Originally Posted by mysocal911

Really? And what is the basis for that statement, i.e. "make it function better than NOS"?

Answers above and in our technical manual. Dyno plots have also been posted and more to come. Have you tried finding a NOS CDI box?

I don't think we have re-invented the wheel here. People fit igntions with programmable advance all the time to 911s. Others fit standard looking boxes that have no timing adjust. We are offering a product that is the best of both worlds - it costs a bit more.

I welcome new products with open arms from the likes of Wevo, Elephant etc. They are expensive because of the time invested in development. It is the same for us, we haven't just knocked this up overnight, we've got two man years of development in this product.

Folks regularly spend around $2500 converting to SSIs. They last a lifetime and release a few more ponies. I'd like to think our product will do the same!

You are a tough crowd!

[wwest]

Originally Posted by Jonny H

The zero crossing detect in the original Bosch design introduces a timing delay as you go up the rev range. This equates to about 3 degrees in lost advance @ 7000 RPM. If you were to adjust +3 on the dizzy in the traditional manner to get the advance back, your idle would be stupidly high.

Why do you surmise that the OEM product design engineers weren't aware of this and thus compensated for some with the mechanical and/or vacuum advance?

The microprocessor compensates for this inaccuracy over the rev range which results in an accuracy better than 0.1 deg @ 10000 RPM.

On what basis did you determine that "compensation" was needed/required..??

1) The 911 (and hence its advance curve) was designed against the fuel of the day which was very poor.

You have that a bit backwards! Our cars were designed during the period werein LEADED gasoline was the standard. Much more "kind" to engines of our era vs the non-leaded fuels, much less prone to detonation, of today.

Today we have high octane fuel and we also like to tune our engines. Ask any tuner, it is common knowledge that fuel mixture and timing are key to the performance of any engine.

Yes, and I took note of the fact many of those tuners resorted to purchasing 100 octane LL aviation fuel.... once leaded pump gas was outlawed.

This should not be brought into question on this thread, it is a given for any device that offers a programmable timing curve.

But I strongly suspect that the clear majority of owners at not "tuners"

2) Some timing curves are physically impossible to achieve. We had a highly strung race car that would not return to idle nicely. Mixture adjustment didn't help. The tuner put in a little sine wave dip just above idle and the issue was resolved.

Assuming your market is "race cars", fine.

Yep, the last two boxes we had in for gut and upgrade were 'repaired' so YMMV.

Here you go, see the 'repair', just waiting for the next 40 year old component to fail:

Sorry, you are simply pissing up wind, looks aren't everything. I would readily rely on a Porsche CDI that has endured 40 years of operation vs risking the infant failures of a complex CDI+. Have you calculated the MTBF of your CDI+..?

In this case the customer didn't want his Bosch case refurbed, so we left it warts and all:

Warts..?? Beauty is truly in the eyes of..

My suggestion stands... Go back to the drawing board and give us a true break-through design, More simplistic, fewer components, higher MTBF.

There is a solid foundation for Porsche's move from CDI to Kettering.

[Jonny H]

Originally Posted by VFR750

I proposed a discussion on the future of 911 electronics as we move from daily drivers and low cost replacements to rare/valuable/collector cars and the higher cost but stock like equivalents. Not a technical attack on a particular manufacturer with whom you disagree with.

In response to a direct question: I made my statement on "function" vs NOS based on the ability to program a rev limiter and to tweak the advance curve. Two significant improvements (functions) not available in the stock box. IMHO that's a huge benefit that can be used in the real world.

My reasoning:
I'm currently running with a rotor rev limiter. It's a little bit of a wildcard as to when it really kicks in. I also could use some more advance but the cost is $500 to get a rebuilt distributor, (which I don't need) I'd prefer programming it as it gives me control and the ability to change it.

So, for me, there is a strong case to start putting a $ value on looking stock, yet have modern performance enhancing features.

Anyone else starting to think this way?

^ Yes, most of our customers! They want originality but they also don't want to run 40 year old electronics. Many keep their original CDI for when they sell the car and run ours day to day. You just don't need the hassle of a breakdown on a road trip. One guy fitted our unit and set off to Italy the next day, 3000 miles there and back.

It is a fact that any CDI box Porsche '69 to '83 (and Turbos beyond that) is a valuable item that will be judged on a)originality and b) the quality of its parts when sold. We know for example that SSIs are not penalized when it comes to value. Why? They are good quality and fit just like standard parts. Same with Wevo etc. Often the stock parts are kept to go with the car.

You hit the nail on the head in that you have to consider the true cost of the upgrade and like many the distributor is an unknown. As long as the main shaft bearings are ok, you can lock your dizzy and not have to worry that the weights are gummed up so no rebuild is necessary. You will also enjoy the 'soft limiter'. A noticeable reduction of power (by backing off the advance) rather than putting your head though the windshield!

We all have older parts in our cars and if you're not careful you end up having to replace everything. Our CDI+ is designed to work with the older parts. It is not a vehicle for selling you a new coil, leads and distributor!

[Jonny H]

Everything i state here is a result of REAL WORLD testing over the last couple of years.

[Jonny H]

Mr West, this thread is about the FUTURE of the CDI box.

You are clearly happy with the original CDI so this thread should really be of no concern to you.

[1100sport]

Thanks Jonny H for taking the time to answer and educate us.
For mapping the advance curve of a Turbo, it is crucial to be able to dial in retard based on manifold boost pressure. I have not seen that feature mentioned on your site. Can your unit do it? Thanks!

[mysocal911]

Originally Posted by VFR750

I proposed a discussion on the future of 911 electronics as we move from daily drivers and low cost replacements to rare/valuable/collector cars and the higher cost but stock like equivalents. Not a technical attack on a particular manufacturer with whom you disagree with.

Pelican Parts provides a rebuilding service as do others who have been referenced
on Pelican Parts in many threads, i.e. at rebuilding prices less than half of these
so-called "modern technology" units.

Originally Posted by VFR750

In response to a direct question: I made my statement on "function" vs NOS based on the ability to program a rev limiter and to tweak the advance curve. Two significant improvements (functions) not available in the stock box. IMHO that's a huge benefit that can be used in the real world.

I'm currently running with a rotor rev limiter. It's a little bit of a wildcard as to when it really kicks in. I also could use some more advance but the cost is $500 to get a rebuilt distributor, (which I don't need) I'd prefer programming it as it gives me control and the ability to change it.

A rev limiter function in an ignition unit is NOT an appropriate implementation, given
that the fuel system still functions flooding the engine and exhaust system once the
rev limit is reached.

Do you have a problem using a 13mm wrench to tweak your 911 timing if necessary,
i.e. if you really think Porsche's timing spec was inadequate?

Originally Posted by VFR750

So, for me, there is a strong case to start putting a $ value on looking stock, yet have modern performance enhancing features.

So where are that data to indicate a performance enhancement that one couldn't
achieve using a 13mm wrench if need be to advance the timing? Besides, today the
octane values are less than what was available when the pre-knock control engines
were designed, resulting in potentially a higher probability of detonation deviating
from the Porsche timing specs.

The key point, though, is that with the conventional ignition signals, i.e. points and
a magnetic pickup in the distributor, little to no benefit can result in timing accuracy
utilizing a microprocessor controlled timing function. The designs proposed are an
over-kill with reduced reliability given the overall part count and complexity!

[manbridge 74]

The future is in repairing CDIs as it is relatively easy with non-potted units.

Or avoid the need altogether by using best practices. Keeping all connections clean, tight, and bright. Maintaining point and plug gap and change intervals to keep from stressing components. Using dialectric grease where necessary, etc.

[Quickstep192]

So, I'm wondering: Does the quality of the spark from a stock CDI box degrade over time? Should I consider swapping my 43 year old CDI unit for a more modern one? Is this a thing where advances in technology in the last 4 decades can result in improved performance, or is it a "if it ain't broke don't fix it" thing?

[mysocal911]

Originally Posted by Quickstep192

So, I'm wondering: Does the quality of the spark from a stock CDI box degrade over time? Should I consider swapping my 43 year old CDI unit for a more modern one? Is this a thing where advances in technology in the last 4 decades can result in improved performance, or is it a "if it ain't broke don't fix it" thing?

1. The Bosch CDI's spark does not inherently degrade over time.
2. If your CDI unit is functioning properly, there's really no benefit in a so-called updated CDI designs.
3. There's really been no real advances in a CDI type of an ignition system and that's
why all "modern" ignition systems no longer use a CDI system for automotive applications.
4. Yes, "if it ain't broke don't fix it"!

[VFR750]

I'm running modified zenith carburetors right now with a NOS 79 distributor. I have no means to do a fuel shutoff rev limiter. And I am using a Porsche rev limiting rotor, just like the factory carbureted engines. There is no means to do a fuel cutoff rev limiter. So sucking fuel on the overrun happens. Just like every stock carbureted Porsche of the vintage. Not going to lose sleep on that one.

I could tweak the 79 distributor weights and learn how to change the advance. I have managed a 13mm wrench once or twice before. I just don't want to.

Right now I run 10 degrees BTDC idle, and the 79 has enough natural advance to get to ~28 BTDC by 3000 rpm. I think 33-35 BTDC might be closer to optimal. It would be nice to experiment, faster, with a programmable system.

Or, I could sell the. 79, reinstall the 82 distributor, pin the weights and play with the advance. Then, in 6 years go back to CIS, take the rotor pinning out or leave it. My choice.

[mysocal911]

Originally Posted by VFR750

Right now I run 10 degrees BTDC idle, and the 79 has enough natural advance to get to ~28 BTDC by 3000 rpm. I think 33-35 BTDC might be closer to optimal. It would be nice to experiment, faster, with a programmable system.

Hopefully, you have a spare set of pistons or have a way to monitor and avoid detonation, right?

Now that brings up another point about digitally controlled timing; What happens when the
electronics controlling the timing fails, resulting in detonation? That is very unlikely with a simple
distributor providing the overall timing. Remember, all the late Bosch ECU controlled ignition
and fuel, e.g. DME units, do not operate in the high temp environment of the engine compartment
as does the CDI unit.