Best advance curve for SC 180 HP ROW full stock?

[mysocal911]

Why hasn't anyone provided their own comparative dyno tests of the stock Bosch CDI vs CDI+?
When a comparative dyno test is done at the same max advance and RPM, the torque & HP differences will negligible.

[Alex_92]

Originally Posted by mysocal911

Here's an abstract from a research paper which evaluates ignitions that produce multiple sparks with the conclusion that the second pulse has little to no value:








Hopefully, you are aware that the second pulse from CDI+ is about 100us, right?

The goal of this thread is to talk about personalized ignition timing for SCs with a CDI+ or which any another system.
The debat is not dual sparks or other ignition topics… sorry…

[Alex_92]

Originally Posted by Jonny H

Hi Alex, for a stock motor, I think your most likely improvements will simply be from multi spark. You can usually richen the mixture a little to produce more power (but remember it may already be rich).

Generally, it is fairly safe to add a little bit more advance (say 3 degrees) when the engine comes on cam around 4000 RPM but make sure to take it out again by 5500 to avoid detonation.

The kick back Jonny042 is referring too is when you have too much advance for starting. Generally speaking, engines start better with less advance.

Hi Jonny H,

I would like to keep the 31 degrees max advance recommended by Porsche. And not to go higher.
When I have a look at the Porsche curve in the workshop manual (see picture in my first message), I see that the 31 degrees max advance is met at 6000 rpm and there is 20 degrees at 3000 rpm.

So that my question is the following: is it possible to have a flat 31 degrees advance from 3000 to 6000 rpm?

Thanks

[Jonny042]

Thought I'd pop in the pics of my test rig to illustrate how I checked/and adjusted the rotor phasing:

Originally Posted by Jonny042

I set up a makeshift test rig for the ignition - the CDI+ ignition is in the car and powered from the battery. Temporarily terminated the two pickup wires and the two coil wires to the car. When I turn the distributor with the drill, I get spark because the CDI+ thinks the engine is running.



The timing light allows you to "see" the position of the components of the distributor when the spark occurs. I made some rough marks to note where the trigger wheel was distributor rotor were and used these to make the decision to alter the rotor phasing.



Here is the key to all of this - drilling a hole in a spare cap and double checking the rotor position in relation to the wire connector, at all possible spark timings.



Again, the standard rotor phasing is fine for use in a "basic" installation of the CDI+ and all of this ins't necessary if you don't want to play around with it.

With my new rotor phasing I am able to play with the trigger angle setting in the software. I loaded a very basic map for testing the advance and I will use this for initial startup - I played around with the trigger angle until the rotor alignment was exactly mid point at mid-advance and chose the 40 degree trigger angle.

You can see in the software the red-shaded "adjust room" limit - this is the range of max allowable advance based on trigger angle and changes with the trigger angle setting. As you can see I have plenty of room to dial in more timing if I wish.



Here is the final installation of the wideband and data logger - the O2 sensor plugs into the black plastic plug fixed to the relay board and the data logger is velcro'd to the vertical portion of the electrical panel. I'm considering both of them temporary.

[Jonny042]

Jonny N here I'll asnwer for now since Jonny H is probably still sleeping.

I am pretty sure he will agree, the stock SC curve is pretty lazy, it is very common for people to modify the advance curve so that full advance comes on much sooner. If you search "distributor re-curve" or the like you'll probably find lots of reading material.

Originally Posted by Alex_92

Hi Jonny H,

I would like to keep the 31 degrees max advance recommended by Porsche. And not to go higher.
When I have a look at the Porsche curve in the workshop manual (see picture in my first message), I see that the 31 degrees max advance is met at 6000 rpm and there is 20 degrees at 3000 rpm.

So that my question is the following: is it possible to have a flat 31 degrees advance from 3000 to 6000 rpm?

Thanks

[Alex_92]

Very interesting, thank you for sharing.
I notice you do not use the rotor with the RPM limiter. Which rotor model do you use?
I would like aloso to remove the RPM limiter from the rotor and entrust that to the CDI+ which is able to limit the engine.

Originally Posted by Jonny042

Thought I'd pop in the pics of my test rig to illustrate how I checked/and adjusted the rotor phasing:

[Jonny042]

Originally Posted by Alex_92

Very interesting, thank you for sharing.
I notice you do not use the rotor with the RPM limiter. Which rotor model do you use?
I would like aloso to remove the RPM limiter from the rotor and entrust that to the CDI+ which is able to limit the engine.

The rotor is from the 3.2 carrera. 84-89.

[Jonny H]

Originally Posted by Jonny042

The rotor is from the 3.2 carrera. 84-89.

Or you can just take the spring and plastic plunger out of the SC rotor. See my video here:

https://youtu.be/GK-gD9_gziU

[Alex_92]

Hi all,

I think everything is clear now except the "Trigger point" parameter I have to enter in the configuration screen. Sometime people enter 30 degrees or 40 degrees!
How can I determine the value I have to enter for my car?

Thank you
Alex

[Jonny H]

Originally Posted by Alex_92

Hi all,

I think everything is clear now except the "Trigger point" parameter I have to enter in the configuration screen. Sometime people enter 30 degrees or 40 degrees!
How can I determine the value I have to enter for my car?

Thank you
Alex

You want the smallest number that will put your graph under the red 'keep out' zone.

[Hx911]

is the trigger point the number that you have set your static trigger to - by positioning the dizzy?
I feel its not an arbitrary number - but really have not seen it explained - or have I missed something in the documentation?

[Alex_92]

Hi Jonny,

Does it mean the number is not linked with the distributor configuration.
So that I just have first to enter my curve and second to enter the smallest "trigger point" number that will put my curve under the red 'keep out' zone?

Thank you
Alex

Originally Posted by Jonny H

You want the smallest number that will put your graph under the red 'keep out' zone.

[mysocal911]

Originally Posted by Alex_92

Hi Jonny,

Does it mean the number is not linked with the distributor configuration.
So that I just have first to enter my curve and second to enter the smallest "trigger point" number that will put my curve under the red 'keep out' zone?

Thank you
Alex

Maybe time to go back to a stock 911SC ignition system with a Bosch CDI, right?

[Glenfield]

Bosch CDI is the Levi 501s of ignition, mysocal911. Great gear, and dependable, but it’s what you throw on with sneakers when you just can’t be bothered to be your best.

It’s all about timing on SCs. There really aren’t too many more levers to pull given CIS quirks and the cars respond so well to advance. The difference between 25 and ~30 on my car is staggering. The ability to bring that advance in sooner and customize the curve is worth whatever troubleshooting it entails. Better yet, to dial the timing back when you’re crossing into a state with crap gas.

As a compromise, you can do all that while wearing 501s and sneakers in your 911 running classic retrofit.

[mysocal911]

Originally Posted by Glenfield

The difference between 25 and ~30 on my car is staggering. The ability to bring that advance in sooner and customize the curve is worth whatever troubleshooting it entails. Better yet, to dial the timing back when you’re crossing into a state with crap gas.

Again, where're the dyno runs to backup the seat-of-pants "feelings"?

You're aware that using a 13mm wrench to adjust a few more degrees of timing is a simple process,
and doesn't require spending over $750 and hours tweaking, right?

And how about the long term reliability with its overall additional parts count and complexity verse the Bosch CDI?
Hopefully, you carry a Bosch CDI as a backup ignition, right?

By the way, have you viewed the spark signal with a scope at the coil and compared it to the Bosch CDI?

[Glenfield]

This isn’t the thread to debate the pros / cons of double spark. I think the debate there is interesting, but you’d only be hijacking the OPs thread to have it. The question on optimum timing curve for an SC is a good one and should be left unmolested (for everyone’s benefit). That CDI+ allows you to do that (vs recurve your dizzy) represents competing value, which we each have to weigh up.

To answer your other question, I am running a stock Bosch CDI unit. I used said 13mm wrench to advance my ignition to ~30 and there was a very pronounced difference (vs stock). I’m running richer and have a different cam. Could feel it through the seat of my Levi 501s. I have a classic retrofit unit that I bought and shoved in my frunk for a cross-country road trip as insurance (should my Bosch CDI kick the bucket). I will swap the two and give the Bosch CDI bench duty for the way back.

[Jonny H]

Originally Posted by mysocal911

Again, where're the dyno runs to backup the seat-of-pants "feelings"?

You're aware that using a 13mm wrench to adjust a few more degrees of timing is a simple process,
and doesn't require spending over $750 and hours tweaking, right?

And how about the long term reliability with its overall additional parts count and complexity verse the Bosch CDI?
Hopefully, you carry a Bosch CDI as a backup ignition, right?

By the way, have you viewed the spark signal with a scope at the coil and compared it to the Bosch CDI?

There are 1000+ units in the field now. We supply many high regarded Porsche shops Worldwide, e.g. Tuthill's, Maxted Page, Rothsport, Patrick Motorsports etc. These are professional shops who depend on reliable equipment. The box on my own car has clocked up 40,000 miles. There are tons of guys in the UK running CDI+ and many of them are friends of mine. Do you really think I would put myself in a position where their cars would run worse or break down? Can you imagine how embarrassing that would be? Think about it.

If there was an issue with the design of the CDI+ unit we would be inundated with returns which we are not. We have had a couple of isolated manufacturing issues - nobody is perfect, but no issues due to design. None.

The notion that you can achieve the same tuning results by turning the distributor and increasing advance across the board is pretty 'basic'. These engines (early cars in particular), respond to increased advance in the mid range as they generally have a flat spot in the power band BUT they cannot sustain increased advance at high RPM without risk of detonation. This kind of curve CANNOT be achieved by bob weights and springs.

Part of the enjoyment of owning these cars is discovering new ways to make them better. That's what I do and first and foremost I am a Porsche guy. I have absolutely no interest in producing substandard equipment. What would be the point?

For years now, you have been on a mission to derail any thread which has positive feedback about CDI+. I find this completely baffling as I get on just fine with the other CDI rebuild guys. In fact, I just sent a French rebuilder 50 sets of original Bosch internals for his rebuilds.

I expect you will requote and pick apart this response in your usual fashion. I won't respond further.

[Jonny H]

Originally Posted by Alex_92

Hi Jonny,

Does it mean the number is not linked with the distributor configuration.
So that I just have first to enter my curve and second to enter the smallest "trigger point" number that will put my curve under the red 'keep out' zone?

Thank you
Alex

That number is the crank angle BTDC at which the box needs to see the distributor signal in order to deliver the timing described by your graph. The unit is applying a delay to the spark beyond this point based on the current RPM and the related advance. The reason for keeping the number small is to minimise error in the time delay calculation.

Whatever number you set it to, the engine advance should always be validated with a timing strobe as a method of 'dialling in' the settings. For this reason it is not necessary to set it up super accurately static, just get it in the ballpark, start the engine and do the validation in a flat portion of the curve....

I typically make a flat section 'test curve' between 2000 and 4000 rpm - say at 20 deg. Adjust distributor so your timing light reads 20 across this range and you are 'dialled in'. Now put in whatever graph you want.

If you change the 'trigger adv' number, you must dial in again.

Hope that helps.

[Jonny042]

Originally Posted by Alex_92

Hi all,

I think everything is clear now except the "Trigger point" parameter I have to enter in the configuration screen. Sometime people enter 30 degrees or 40 degrees!
How can I determine the value I have to enter for my car?

Thank you
Alex

I should chime in here and explain - my number is set to a different value because I "reclocked" the trigger wheel in my distributor to allow great flexibility in adjusting the rotor phasing. I tried to explain this well in my build thread (an excerpt of which I posted). Don't get too thrown off by what I did, for a normal installation like yours it would be totally unnecessary to get so tricky.

I would say go back and thoroughly and carefully re-read the excellent instructions that Classic Retrofit has provided, and like Jonny says, play around a bit but always double check your settings with a timing light.

One of the reasons my curve is flat from 800-1200 is for that very reason - I know at any reasonable idle speed my MFI system is in the mood for that day, I can check the timing to confirm it.

[Jonny042]

Originally Posted by Jonny H

For years now, you have been on a mission to derail any thread which has positive feedback about CDI+.

Maybe we should just agree to ignore him. He's been littering this forum with his crap for years. It used to be all about bashing Steve Wong, now it's CDI+. Take it as a compliment.

At least he doesn't seem to have an interest in air conditioning??? LOL.

Cheers, Jon