ignition options for efi ITBs

[Pfitz911]

Hi gents
Just in the process of installing Als ITB EFI kit. Its a 2.7 stock engine, that will be a 2.8 with moderate cams in the next year or two
Lets just say Als getting some interesting questions!! All good, its a fun expensive way to learn mechanical skills, but actually pretty straightforward.
That being said, I haven't got to the tuning bit yet!!

Anyway, Ill get fuelling underway first with my dizzy based ignition, then I have to think about spark control. Initially I was going to go with EDIS (my MS2 wont support COP without mods), but I have heard a CDI based approach could yield the most power due to the more intense spark. I would like to keep it single plug, but not definite. Performance develpments suggest M&W here in Oz (take a look at their tech articles)

Replacement Upgrade Ignition – performancedevelopments.com

My thinking was the ECU would more accurately control the spark, but Neils article is pretty pro CDI

How would the M&W compare to the retrofit CDI that Johnny in the UK makes?

Thoughts?

[Jonny H]

Neil at Performance Developments and myself are definitely on the same page regarding CDI. COP is great for modern engines but CDI always wins out with the 911 combustion chamber designs. Give Neil a ring and he'll put some more detail on that statement.

We have CDI+ systems on the way to PD shortly.

(P.s. The main advantage of CDI+ over MW is the double spark)

Edit: Forgot to say CDI+ is also fully mapable for ignition advance.

[Pfitz911]

Double spark?
Can you elaborate?
Still have your fuse panel sitting in my shed Johnny. Might need to pm you with some questions. My cars a bastard!!

I've just bought new leads (beru?). Will that be ok with either your cdi or MWs? How about the coil?

[Tippy]

Originally Posted by Jonny H

Neil at Performance Developments and myself are definitely on the same page regarding CDI. COP is great for modern engines but CDI always wins out with the 911 combustion chamber designs. Give Neil a ring and he'll put some more detail on that statement.

We have CDI+ systems on the way to PD shortly.

(P.s. The main advantage of CDI+ over MW is the double spark)

Other than multi spark, what are you seeing advantages with CDI over COP?

I know of 1 member who's done over 700whp with standard OEM COP on a boosted motor obviously without flame-out.

[Raceboy]

I would like to know what is the relation between CDI and 911 combustion chamber design?

CDI has advantage with distributor where available dwell time for coil is very short but with EFI any direct ignition system (wasted spark or COP) already has advantage of overlapping dwell and very high spark energy. Plus spark of inductive system lasts longer than CDI.

Besides, cylinder pressures on normally aspirated 911 engines are so low (compared to boosted cars) that there's no danger of spark being blown out.

For my 2.4S build (w/ 2.2S pistons, drive-by-wire ITB's, twin-plug, big port heads etc) I opted for 12plug distributor that is controlled by VEMS ECU over regular two inductive coils, simple system. Even cheaper and simpler would be to use two Bosch 3x2 wasted spark coilpacks but I wanted retro look

3.2 Carrera, 964 and 993 have regular inductive ignition systems, they work well.

[mysocal911]

Originally Posted by Raceboy

I would like to know what is the relation between CDI and 911 combustion chamber design?

Good question!

Originally Posted by Raceboy

CDI has advantage with distributor where available dwell time for coil is very short but with EFI any direct ignition system (wasted spark or COP) already has advantage of overlapping dwell and very high spark energy. Plus spark of inductive system lasts longer than CDI. 3.2 Carrera, 964 and 993 have regular inductive ignition systems, they work well.

That sums it up!!!!!!!!!!

[Jonny H]

Originally Posted by Tippy

Other than multi spark, what are you seeing advantages with CDI over COP?

Read the link that the OP posted.

[Raceboy]

I have yet to see any measurable advantages with CDI over inductive system in torque gains. At least that what they state in the article. And there are no solid points with regards specifically to 911 combustion chamber design.
You need higher spark energy in case you have spark blowout but really, it is the fuel that creates energy in the combustion chamber, not spark plug. The latter just ignites it, that's all. And flame front still moves at more or less constant speed (it mostly depends on fuel itself and mixture).

And with high boost cars inductive system actually has advantage over CDI with its longer lasting spark.

[Jonny H]

Originally Posted by Raceboy

I have yet to see any measurable advantages with CDI over inductive system in torque gains. At least that what they state in the article. And there are no solid points with regards specifically to 911 combustion chamber design.
You need higher spark energy in case you have spark blowout but really, it is the fuel that creates energy in the combustion chamber, not spark plug. The latter just ignites it, that's all. And flame front still moves at more or less constant speed (it mostly depends on fuel itself and mixture).

And with high boost cars inductive system actually has advantage over CDI with its longer lasting spark.

Engine builders 'measure' these gains all the time on the dyno. I really think you should have a read of Neil's background in F1 on the About page and the engines he has built over the years. He has tried COP and CDI back to back.

Can you explain why, where rules allow, pretty much every 'pre-CDI' 911 race car is converted to CDI? And I am talking cars that have already ran an ignition amplifier with an inductive system to solve the dwell time problem with points. Some teams go to great lengths to hide the CDI box too! It's not just because they are high revving either - the gains are seen in the low to mid range too.

p.s. Someone asked about our 'double spark'. Well, we discharge two sparks back to back, typically with a 200-400us interval. This gives us the equivalent of the inductive long spark but with the punch of CDI. The scheme typically yields 7 to 10 ft lbs on a single plug 2 litre car.

[pampadori]

I'd suggest running the AEM EPM puck kit from Rasant along with the smart coils they offer.
I ended up running this setup and after spending sometime getting the crank/cam sync setup (user error) its been reliable and looks like it was OE.

From my reading and digesting what i can find online about EFI tuning, timing is where the power is made. Being able to fine tune the ignition timing based on load is very important if power or MPG is a goal of yours. You can run the cruise AFR very lean so long as you can adjust the timing to support it (way more advance than you'd have with WOT). So it goes hand in hand for trying to get increases in MPG.

With my setup I can trim each cylinder independently, while I haven't exactly figured out way I might need to do that yet, knowing that I can is valuable. Also adjusting the dwell and being able to incorporate some ign retard that tappers off after I go from decel fuel cut to back on throttle is a benefit for preventing drivetrain shock (or so says AEM). Its also integral for advanced knock control where you might want to only retard a few degrees on the cylinder that is knocking and not all 6 cylinders at once.

I also use the timing to maintain idle so without control of it there you'd be missing out on that ability. If my idle is higher than my target i retard a degree or 2 or 4 or 6 depending how far above target it is. Same thing but I advance if idle is lower than target. So EDIS at the least, but you are going to want to go full on controllable ignition once you start to tune it. I suggest you start with it from the beginning.

[Raceboy]

Originally Posted by Jonny H

Engine builders 'measure' these gains all the time on the dyno. I really think you should have a read of Neil's background in F1 on the About page and the engines he has built over the years. He has tried COP and CDI back to back.

Can you explain why, where rules allow, pretty much every 'pre-CDI' 911 race car is converted to CDI? And I am talking cars that have already ran an ignition amplifier with an inductive system to solve the dwell time problem with points. Some teams go to great lengths to hide the CDI box too! It's not just because they are high revving either - the gains are seen in the low to mid range too.

p.s. Someone asked about our 'double spark'. Well, we discharge two sparks back to back, typically with a 200-400us interval. This gives us the equivalent of the inductive long spark but with the punch of CDI. The scheme typically yields 7 to 10 ft lbs on a single plug 2 litre car.

I tune engines on the dyno all the time. And have been doing so for last 15 years.
And no, not everyone is trying to use CDI.
Please show me back to back results, I would like to be proven wrong.
With the CDI double-spark you pretty much proved that inductive system is actually better in many areas, for example with spark duration as I mentioned above.
I have yet to see the benefit of stronger spark energy (with lower duration) unless one has spark blow-out problems. Leaving the distributor ignition case (where there's no overlapping dwell possibility) aside.

[Jonny H]

^ The Rasant system is pretty nice and agree that ignition timing is where more power can be made. CDI+ is fully mapable too and does the idle adjust thing.

Further to the Inductive vs CDI debate:

In 1967 Porsche produced the 911R. It had a twin plugged engine and ran inductive ignition with two ignition amplifiers. It didn't have points, it had a distributor with two variable reluctors stacked. The early 917 also had inductive igntion with a similar arrangement.

Post the introduction of the Bosch CDI unit, ALL subsequent Porsche race cars, whether twin plug or not used CDI. None of them used inductive anymore, even though they had the amplifier technology available since the R. The road cars could easily have had an inductive igntion with amplifier (which would have been a much cheaper solution) but they all went to CDI.

[mysocal911]

Originally Posted by Jonny H

Post the introduction of the Bosch CDI unit, ALL subsequent Porsche race cars, whether twin plug or not used CDI. None of them used inductive anymore, even though they had the amplifier technology available since the R. The road cars could easily have had an inductive igntion with amplifier (which would have been a much cheaper solution) but they all went to CDI.

That's an incomplete history and why that was the case prior to the late '70s and early '80s.
It was the lack of fast switching and high power semiconductors that necessitated the use
of the CDI design. Those devices of that era could not achieve the desired spark energy at the
very high RPMs with the short dwell times.

Presently, no OEM auto manufacturer, e.g. Porsche, uses a CDI system including with their race engines.
A CDI system is inherently less reliable, more complex, and more costly than an inductive discharge
ignition (IDI) design, e.g. COP, and with a sud-optimal spark both for emissions and performance.

A CDI with a second spark (200 - 400us later) is a marginal at best improvement over a single CDI spark,
i.e. both sparks less than 100us, where the typical IDI produces a spark about 1ms
(10X the CDI's single), thereby delivering less energy initially to fully ignite the fuel charge
than the IDI.

[Jonny H]

^ Theorising is one thing but dyno results and racing tell a different story.

[Raceboy]

I was asking for a dyno sheet where there are back to back results of inductive vs CDI on the same engine and on the same dyno.

If you claim differences, please show proof.

[Pfitz911]

Ok, so its pretty divided. Neil seems to have some pretty heavy experience in motorsport. I'm thinking CDI, but still open to suggestions
I have points at the moment. Any mods for the distributor, or would you leave it as is

[merlinfe]

Few options for the original poster:

1. Edis. It's easy enough and there are multiple crank wheels available from various vendors as well as a plethora of parts availablity. Wiring diagrams are pretty easy to find as well.

2. Dual EDIS. With two ignition modules you can split signals and run coil on plug. There is at least one member on this forum who's done it. I have it bookmarked at home. Toyota, Audi/VW, Honda coils have been used with success.

3. Aftermarket Ignition system. Reasearch SDS, Haltech, AEM to see what will work best with what you have already, but you'll likely be looking at getting rid of the Megasquirt at that point for something else.

Bottom line as I read it now is that you have an MS2 for your ECU. If you're going to stick with that EDIS is your cheapest best option right now. If you sell it and go with something else, then the skies the limit. I wouldn't worry so much about spark output unless you are going well above 6500rpm. Keep it simple to start out and get your project running, then do more reasearch and bring out your big guns later.

Also, many of the points and counter points on this thread are being presented by individuals trying to SELL a product. Do what works best for you and your situation. Personally, I'd try to get a map from Al for your Megasquirt and see what he recommends to get the car started and running.

-Steve

[Raceboy]

With MS2 just use ANY wasted spark 6cyl coilpack and fire it directly from MS2, no need for EDIS module at all. Your MS2 should have several IGBT high-power outputs available.

[trond]

run coilpacks directly from MS2 really ? I am running dual EDIS modules&coil packs from MS2 and not that I am not happy with the setup I would not mind simplifying. how do I go about to hook up the two coilpacks to the MS2 directly ? Happy for any advice !

[lvporschepilot]

Smart coils (coil on plug) run directly from the system running your EFI is the best solution as everyone is run under one program. Smart coils triggered via the falling edge of the trigger wheel seems to be what AEM infinity works with. Lots of options for those.