MSD vs Crane

[ohecht]

I've read all the posts about MSD, and I agree that the multiple spark feature has value below 3000 rpm, even though the stock CDI unit is also fine.

I saw some info about the new Crane digital ignition unit, but not any opinions from anyone who has tried it.

The Crane info site says it is Inductive ignition, rather than capacitive discharge (more claims below).

Has anyone out there compared it to the MSD?

oh, and I just ran into the Accel 300+ unit during my research. Also digital, and much smaller unit to mount. Accel products have always seemed cheesy to me, though.

Olivier


From the Crane site:

Multi-Spark operation for clean low-speed firing and quicker, easier start-ups!

Improves throttle response!

Inductive ignition design (not a CD) produces longer duration spark for increased performance with stock or mildly modified engines!

Fully potted using new soft-urethane material. Resists dirt, moisture, heat and harmful vibration!

Surface-mount, robotic assembly technology and fully-digital design delivers far greater ignition reliability!

Can be triggered by points, magnetic input, or stock ignition module, for broad application coverage!

All new, low-cost, performance ignition with genuine Crane Cams quality and famous Crane Cams reliability!

Use Crane FireBall LX-91 high-output coil (Part Number 730-0091) for maximum ignition performance.

Tach output and on/off trigger signal status LED included!

Black anodized, extruded aluminum housing, finned for maximum heat dissipation!

CARB E.O. applied for and pending approval.

[jluetjen]

My sense is that the Crane is comparable to the MSD.

Inductive versus Capacitive Discharge:

Inductive: The system creates a magnetic field which is then collapsed. The (change in the) collapsing field creates a voltage which is stepped up by the coil. The voltage created is proportional to the the speed and total change of the collapsing field. This is how traditional ignition systems work. These systems are often gated at high RPM's by how fast the condensor (capacitor) in the system can be fully saturated. As RPM's go up, the amount of time to recharge the capacitor goes down. The good news is that inductive systems often have sparks that last over 1 millisecond (.001 seconds).

Capactitive Discharge: These systems work in the "opposite" direction by having the change in magnetic field be the creation of the field rather then the collapse. A series of capacitors (not to be confused with the condensor) in the system are charged and then dumped into the coil which creates a magnetic field. The downside is that the sparks that are created are very short: about 30 microseconds (.00003 seconds)

The thing with ignition systems is once they are "good enough", then more power or sparks really doesn't net you anything. What I've heard/read is that both systems are very good. And if the system does the following, you've most likely got all that you can from the ignition.

1) Resists Plug fouling
2) Optimum spark timing (or multiple sparks which kind of approximates by covering "all the bases".)
3) Adequate voltage at all RPM's to provide a spark that will jump the gap.
4) Holds it's settings (or rather doesn't need frequent tune-up adjustments)
5) Is reliable

Once you've resolved these problems, this system is optimum - isn't it?

[911pcars]

John,
Excellent response. I couldn't say it any better.

One factor not related to any performance issue is the physical size of the unit to install and still be able to access the rpm cutoff speed adjustment. The newer Crane ignitions and the Accel are on the smaller side to make this slightly less of an issue.

Sherwood Lee

[nhromyak]

I have also heard that if you get TOO much (too hot) a spark you can cause mis-fire. I think this is opposite of detonation.

Basically, the spark is so HOT and FAT it literally blows the fuel out of the way and does not ignite it at a consistent time. Similiar to oil rig fires. Using ALOT of dynamite BLOWS out the flame.

[911pcars]

"I have also heard that if you get TOO much (too hot) a spark you can cause mis-fire. I think this is opposite of detonation.

Basically, the spark is so HOT and FAT it literally blows the fuel out of the way and does not ignite it at a consistent time. Similiar to oil rig fires. Using ALOT of dynamite BLOWS out the flame."

I've never of that. I don't think a spark has a temperature. It's only electricity isn't it? You need 3 things for combusion: Air, Fuel and a Spark. A spark is a spark is a spark?

Sherwood Lee
http://members.rennlist.org/911pcars

[nhromyak]

Then a gap would be a gap would be a gap.... However, a better gap / spark provides better initial burn of the fuel.

You can take it for what it is... an ignition manufacturer touting why his is better....

The following is from www.jacobselectronics.com

""The increased spark plug gap is actually very important to getting the most out of our (or most any other) high performance ignition system. While the amount of energy needed to sustain the spark across a wider gap is actually not significantly more than a smaller one (within reason); the arc-over requirements vary substantially.

Arc-over is the period preceding the spark, when the electrical energy must create a plasma between the plugs electrodes for the spark to follow. Since conditions are not exactly favorable within a combustion chamber to allow this plasma trail to form (actually, it's a form of localized ionization) due to compression, fuel (which is not exactly conductive), and turbulence, substantially higher voltages are required.

First, the real business end of ignition, the part that really gets everything going, is the arc-over event. This is the part that really needs the higher voltages and where the most benefit from them will be derived. The remaining spark is (forgive the simplistic analogy) along for the ride on the already burned in plasma trail. In engines with very high cylinder pressures or specific outputs the turbulence associated with combustion can literally buffet or "put out" this remaining spark as it tries to sustain combustion. This is felt as a miss or stumble.

Hence part of the benefit of multiple sparking - repeated arc-over events that do not get "blown out" by the combustion event itself or the associated cylinder turbulence. Remember, capacitive discharge ignitions (like ours) have short spark duration compared to inductive systems, so there isn't much "trailing spark" to begin with to be buffeted about. The multi spark capacitive system keeps hammering away at the issue, throwing out multiple arc-over events.

Second, the larger gaps also provide more area for the arc-over and spark to take place, thereby exposing them to a greater amount of the fuel air charge and further ensuring more complete combustion. While .015 to .020 increases don't look like very much, the aerial profile or "surface" of the arc-over & spark changes dramatically. The benefit of this increased arc-over and spark area is well known. Multi-electrode plugs or weird geometry plugs have tried to capitalize on this using "stock" ignitions for years - some with great success. Indeed, some of these plugs can coax out substantially improved arc-over and spark characteristics at lower voltages. Although these plugs are easy to install, they are not really a complete answer.

For the record, we don't recommend multi-electrode or weird geometry plugs with our system. When really high voltages are pushed through them there is a real likelihood of isolated electrode melting and some measure of thermal unpredictability. We have extensively tested regular plugs and we have found them to perform very consistently with little or no change in the plugs ability to deal with heat. Besides, with a strong ignition system much of the benefit or need for their special shape or conductive alloys simply isn't needed.

We have had customer's experiment with some of these plugs, and we have done some testing ourselves. While the "official" recommendation still stands I am sure that as more and more testing occurs we may soon be able to recommend or provide some guidance on using these plugs with our system if additional performance is and compatibility are verified. "

[ohecht]

I agree that ignition can definitely be "good enough" if it meets the requirements listed above, especially on a daily driver.

I think size may be the determining factor, since everyone seems to complain about the MSD unit.

Here is an interesting shot of the internals from the MSD and Crane units. I have to admit the Crane unit looks more modern and sophisticated in its construction.
http://www.cranecams.com/whatsnew/compare.htm


Here is a good side-by-side comparison (see if you can guess which site it came from):
http://www.cranecams.com/whatsnew/hi6vsmsd.htm

Does anyone know the difference between the analog MSD 6A unit and the digital Crane and Accel units? Is it just in how they manage data?

Sorry to bother you, but there is very little objective information out there concerning this, and even less concerning our cars. Most companies I talk to immediately say "That has crank fired ignition, right?" as soon as I tell them the car is a Porsche. THe Autozone guys laughed when I asked about an ignition unit for a Porsche and then I pointed to the MSD 6AL on the shelf behind them. I trust the information on this board more than other sources.

What are the differences between the coil to use with one of these ignition systems versus the stock CDI system?

Also, I assume all of these have to replace the CDI box, rather than be triggered by it, which I assume would fry the new unit.

Olivier

[911pcars]

"Then a gap would be a gap would be a gap.... However, a better gap / spark provides better initial burn of the fuel. "

Multiple sparks are good to insure complete combustion. Notice that most systems only produce multiple sparks below 3000 rpm. The concept of "better" is relative.

The best gap is one which provides a space for the spark to jump to ground - wide enough to build up whatever secondary voltage is required to jump it (whether it's 3000 or 10,000 volts on a regular points/coil system) and to prevent deposits from bridging the space. Likewise, the gap has to be small enough so the spark can jump to ground. As compression increases, so does the spark requirement. Manufacturers have a recommended gap for their systems.

I didn't see where Jacobs discusses spark temperature. BTW, Jacobs has a reputation for slightly exaggerating the benefits of his systems. He even wrote a book about ignition, but it's decidely slanted toward using his systems.

Sherwood Lee

[Paul W]

I’ve been watching this thread with some interest, as I plan to do this conversion later in the year.

I spoke to a tech at Crane (Australia) yesterday, and one of the questions I asked was the real difference between their unit and the MSD. Distilling out the hype, the interesting issues were the Crane’s more modern design and the adjustable rev limiter(s). The Crane unit apparently has two rev-limiters which can be set up to 9900 RPM, compared to the MSD unit’s chip based system. The chips for the MSD unit have to be purchased separately (added expense) and according to this guy are moisture sensitive. He did concede that once both units are up and running there was probably little separating them. The one negative with the Crane he offered was that it was sensitive to the triggering device, that being it didn’t work with all after market optical points replacement units.

For any Australians interested I have been quoted $508 AUD for the supply of the Crane unit - $70 - $130 for a coil (depending on how upmarket) and $95 for a Tach adaptor (all prices incl GST). I’m having a lot of trouble finding anyone dealing in MSD units to do a cost comparison.

Regards

[ohecht]

The Accel 300+ unit seems appealing because of its size and features, but it just looks cheesy to me.

They officially say their universal model won't fit a 911, but I think that is because it is designed to be triggered by a stock ignition, like a Jacobs. That is a good way to hook it up, because you get built in redundancy (you can just bypass the unit and use the OEM box if something goes wrong).

However, I don't think these types of systems will work with our CDI OEM units.

I do think, though, that the Accel unit could work as a stand alone unit, just like the Crane and MSD units.

I think another feature of both the Crane and Accel units is the weatherpak connectors.

Olivier

[H20911]

I have commented on this stuff before......... so It comes down to extra features that you want or need.

stock is great and is fine for most app
old MSD6A great in it's day (anolog)
crane Hi6 (digital) better then old MSD
new MSD (also Digital) About the same as crane.

Crane " more current at the Plug"
MSD "more voltage at the plug"

I have had both the MSD 6AL box and the CRane Hi6 box
the only reason that I changed was that the crane has more features and the New MSD stuff was not avail. yet.

take your pick......... once the candle "lights it off" more spark in the form of current or voltage doesn't do a damn bit of good.

[ohecht]

What type of distributor is there on an 82 SC?

What do you use on your setup to trigger the new unit?

The wiring diagrams show 2 low-voltage wires (terminals 7 and 31d) leading from the distributor to the CDI unit, but I can only see one green wire leaving the base of my distributor.

Is that your new coil on the side of the engine compartment?

Olivier

[jluetjen]

Being a Marketer and having worked in Electronics for the last 16 years, I think (for once) that I'm qualified to respond to Crane's comments about their new Digital design versus MSD's analog design.

It's Good Marketing and Good Manufacturing! It shouldn't make much difference to the user except for the two different strategies for the rev. limiter. Crane's digital rev. limiter is cheaper, most likely more reliable and should be easier to use then MSD's (until it breaks!). If it breaks, you'll have to replace the whole system versus possibly only replacing MSD's "chicklet". MSD's system may also be less suseptable to ESD (Electrical Static Discharge) damage if it uses older technology electronics.

What's the benefit of Crane's digital design? DFM - "Design for manufacturability". I suspect that it is much cheaper to manufacture and has better yields at final inspection. Both of these are very important to Crane. After it passes final inspection, I doubt that it will be any more reliable then MSD's system, especially since both units are potted (conformally coated).

What about the "Spagetti Wires"? What about them? Both systems have hand soldered wire connections from the outside to the Printed Circuit board. MSD's older design appears to have had some updates (ECO's) resulting in the jumper wires. Crane's will get them too as time goes on unless they spin a new PCB revision which incorporates them.

Bottom Line: Both systems seem to provide lots of spark and should be "Good Enough".

[ohecht]

Does anyone know how to "describe" the distributor on an 82 SC USA as it relates to triggering aftermarket ignition systems?

I've read about compatability issues with different types of distributors and pickups, but I'm not sure which type I have.

Thanks,

Olivier