The seats are open - you need to dissemble the tachometer.

The trick is to check with a re-builder if you can get their trade secret on what viscosity oil they are using when they do it. I once tried it on my 74 and it didn't work out. I eventually got a replacement tachometer. I since upgraded to 993 gauges along with the 3.6 and these tachometers have magnets to dampen the needle, they don't become bouncy.

I don't remember what oil I used but I believe it was too light.

SC Plots
 

Hey SC Fans, it has taken a while to make sense of the data from a few runs on the dyno we did a few weeks ago. I went back and asked for the raw data and pieced these plots together so I could do the overlays properly.

It turns out that sometimes the dyno operators don't engage the dyno quick enough in the power runs which can result in a oddities at the bottom end. This is what we are seeing in the green trace. So please ignore the lack of pick up low down on the green trace.

This is the results of three runs:

Torque (top traces):

Green - Standard SC with Bosch CDI
Orange - Same car as above with CDI+ Ignition (still using standard distributor advance)
Blue - SC with 964 cams, SSIs and custom ignition map (locked distributor).

Red, Purple and Cyan are the HP curves in the same order.

http://www.classicretrofit.com/images/Powerruns.jpg

From idle to 4400 sees a step change in torque on the standard SC. The improvement is similar in effect to fitting a set of SSI heat exchangers. It fills in the mid range, bringing the SC 'whoosh' in sooner.

The car with 964 cams, SSIs and mapping really benefits in the drive. Despite only 10 HP more at max output, the big chunk of torque in the middle puts the car in different league.

These runs are obviously done at WOT. What you can't measure is the throttle response which is greatly improved.

Oha, I can see the negative nancys already sharpening their pens so I'll say it first: From the data it looks like the 964 cams make a more signifnant difference while the CDI+ adds are more subtle. However, I do see the torque benefit in the 3.5k - 4k range (kind of where it matters most) and that is significant, too. All in all I agree there are benefits and you have shown lots of data to prove it. Nice job.

Ingo

Here's the plot for the standard US Spec 1975 2.7. Different dyno this time.

Bold is CDI+, feint is Bosch

http://www.classicretrofit.com/image...no1975US27.png

Big difference in the drive on this one - different car....

Note: Same dyno operator issue engaging with the low end!

Jonny, do you have any data on tail pipe emissions and fuel economy. I would want the CDI+ even more if I knew that it would help me pass California emissions testing. Thanks.

Interesting question. I do remember the last dyno operator commenting that my car was running nice and clean but our focus was on power output that day so I didn't think to get a back to back measurement for emissions. We do know that more fuel is getting burnt so it follows that the engine efficiency is up and hence emissions should be lower. It will try to gather some data when we're next testing.

Now, we do have the tacho calibration feature. This is meant to be used to trim your tacho for accuracy. Let's just say that it is possible for the engine to be turning at, say, 3000 RPM but the tacho to be showing 4000 RPM. The smog tester or the track noise level guy doesn't need to know....:)

Most emissions RPM measurement is done by monitoring the battery charging waveform, test device plugged into the cigarette lighter.

California inspects engine/systems for factory authenticity.

And of if you get caught?

California uses a pickup on the engine...I would assume on one of the spark plug wires but I am not sure. It does not use alternator output.

^ Shame. It was just an idea.

The 'decoupled' tacho signal has its uses though, both in fine tuning the tacho and also in limiting overshoot. As a previous poster pointed out, the oil dries up in the older units and then damping is lost. It can't cure hopeless cases but it is an improvement. We also use the tacho as a display for adjusting settings like the rev limiters.

The other use is for a custom range tacho. You can now convert any tacho to be, say, a 10K tacho just with a face change. The CDI+ can be setup to drive this correctly without having to send the tacho off for recalibration.

Wwest, piss off. I have not done much posting here lately but your every post makes me wanna ...argh.. 1 2 3..all good =)

Johny H. CDI+ seems to be a good product, replacement for old and much more. One day when i get enough cash I will surely upgrade my car with your CDI+

Keep up the good work :)

doubt it
Poosheys with 6 phase alternators rev twice as high.

We sent a couple of CDI+ units out to the States a few months ago now. One to Dave at TRE Motorsport and another to Steve Weiner at RennsportSystems.

Dave ended up sending a unit on to Loren Beggs of 911Design in Montclair, CA. Home Page 911 Design - 911 Design as he had a '69S being restored with a fresh MFI engine. The engine is rebuilt but totally stock.

http://www.classicretrofit.com/images/dyno/1969S_1.JPG

I got the impression that Loren is a busy chap so five months later (two days ago) I received an email from Loren:

We ran the car on the dyno and tuned it 1 degree at a time for maximum power with the old CD box. We then installed the Classis Retrofit box. We installed and we did not advance the timing and it would not accelerate past 3000 RPM as the timing was too retarded (as you stated it would be) I just wanted to check it right from the beginning. In the end I think we added 6 or 8 degrees (I’ll find out for sure) and low and behold it added 5-7 HP and 5-7 foot pounds of torque all the way up to 6800 RPM’s at that point it looks and felt like a rev limiter kicked in. I am going to take the instructions home tonight and read some more. Then I’ll get the software loaded on my laptop so I can see what is happening at that RPM point. So needless to say I am pretty excited about the unit. I’ll follow up after doing a little more programing.

So he did some bedtime reading, next day did a few timing tweaks and came back with a whole load of plots. I have overlayed them all in photoshop to the best of my abilities:

With the stock timing:

Thin green and thin blue are Bosch CDI.
Thick green and thick blue are Classic Retrofit CDI+.

Red and purple are CDI+ with the ignition mapped:

http://www.classicretrofit.com/image...S_Combined.jpg

He's going to report back after he's driven it.

Jonny

If you are still taking input for suggested developments to the CDI+ perhaps it might be possible to add a feature to retard the advance in response to an input from a knock sensor.

Would be a nice safety feature against over advance settings.

Tim

The dyno charts are not opening for me....are they there?

Links are broken for me too.

^. Sorry guys, website reshuffle. Will have a look and repost.

It's not a simple system design to do knock control, e.g. the 964 DME ECM had three processors,
2 - ignition/fuel, 1 - knock. It can typically be done using FFT (Fast Fourier Transform) to analyze
the engine knock signal in the frequency domain. The algorithm used once the signal is transformed
requires a more powerful processor than the typical PIC processor used in simple aftermarket
fuel/ignition ECMs.

Quoted and edited to fix pictures!

I was not thinking of dynamic knock control.

I was thinking much simpler. If it detected a knock, it would simply retard the spark via the overlay by a degree (repeat in degrees till knock goes away) and that retard override remains until the ignition is turned off. If it could also provide some form of visual warning that the override was activated via the shift light even better.

More about tuning aid and engine preservation. Would not be such a load on the cpu compared to dynamic systems like you describe, as found in a lot of more modern cars.

Sure, we have thought about this. A bit snowed under right now but knock and MAP are on the cards at some point.

The STM32 processors we use in our products are more than capable of handling the signal processing for a knock sensor. Haven't done a PIC design for at least 10 years now, thank goodness!