After Market Ignitions (MSD/Crane etc)

[Lorenfb]

You should leave your cars stock, if they have a good Bosch CDI. The MSD
and all the klug add-ons are a total waste. Plus, they make a good Porsche
look like a high school autoshop project.

Read the many posts about the MSD on this board over the last few months.
The multiple spark system at low RPMs is a marketing gimimck. Check out this
website (systemsc.com) on the Technical page under Ignition Systems for
some additional info.

Have Fun
Loren
'88 3.2

[SprintStar]

Originally posted by jluetjen
Been there -- done that -- did you get the email?

Nope, John. Didn't get no mail. You got my address in the PM, right? sprintstar@worldwidewerkz.com

Thanks!!!

Sprint.

[pwd72s]

I love you guys... MSD

Schwepco.
And don't let anybody disagree!

[Lorenfb]

For those that want to look at the numbers and see why the MSD has no
real added benefit:

An engine at an idle of 1000 RPMs equals;

1. 16.7 revs per second or,
2. 60 ms (milleseconds) per rev for 360 degrees or,
3. 1 ms equals 6 degrees of engine rotation.

The power stroke is 90 degrees. Since MSD ignition pulses can only
be produced at a maximum of every 2 - 2.5 ms, the piston will have
moved 12 to 15 degrees after the first spark occurs. How much
real benefit is there for this late of an additional spark? The obvious
lack of benefit becomes more real as the RPMs increase.

For those that have doubts, use an o-scope and view the ignition
pulses at the coil on the MSD system.

Have Fun
Loren
'88 3.2

[SprintStar]

Originally posted by Lorenfb
You should leave your cars stock, if they have a good Bosch CDI. The MSD
and all the klug add-ons are a total waste. Plus, they make a good Porsche
look like a high school autoshop project.

Read the many posts about the MSD on this board over the last few months.
The multiple spark system at low RPMs is a marketing gimimck. Check out this
website (systemsc.com) on the Technical page under Ignition Systems for
some additional info.

Have Fun
Loren
'88 3.2

Loren, my car, a '67S, has no factory CDI. What should I do? Install a Bosch or MSD?

Thanks.

Sprint.

[jluetjen]

Loren;
Trust me, the ignition requirements of the older cars are different then the later EFI'd cars like yours. Your car has accurate fuel delivery across the board, especially at idle and that is considerably more difficult to achieve with the earlier cars. Most of our cars also have considerably more overlap then your car, which makes the balancing act even more difficult.

I can tell you for a fact that the installation of the MSD onto my '69E (with 9.9:1 S pistons) made a very noticable improvement in the idle and low RPM running around town. While the second spark is 12 degrees after the first, keep in mind that our pistons have significant domes in which intrude into the cumbustion chambers. In a nutshell, the combustion quality at low rev's (when off-cam) is pretty bad and the multiple sparks are effective. Basically rather then a cylinder mis-firing due to the spark not igniting the mixture, it now fires 12 degrees retarded which is a lot better then nothing.

With a modern engine with a better optimised cumbustion chamber, I agree that an MSD won't provide much benefit.

If you're ever out in the Boston area, let me know and I'll show you.

[Lorenfb]

Typo correction: The power stroke is 180 degrees and not 90 degrees.

The effect of additional spark pulses would be like retarding the engine
12 to 15 degrees with an extremely lean mixture at idle. The MSD does
make an improvement over a points & coil ignition, but not the Bosch CDI.

Sorry for the error.

Loren
'88 3.2

[Lorenfb]

A good test for how effective the MSD is in firing a very rich mixture
would be to use a gas analyzer. You could measure the HC (hydrocarbons),
a measure of unburned fuel, with a Bosch and then with the MSD. If the
multiple sparks are effective, the HCs should be reduced.

Good Luck
Loren
'88 3.2

[CamB]

Loren,

What should SprintStar do, as he currently has nothing - 30 year old Bosch or new MSD (for less $$$)

You know we've been down this path before.

Cam

[CamB]

A good test for how effective the MSD is in firing a very rich mixture
would be to use a gas analyzer.

I dunno about whether it actually burns more fuel, but I watched my BMW idle at >10% CO for about 15 minutes with the MSD. It didn't foul the plugs.

[911pcars]

"The power stroke is 90 (180) degrees. Since MSD ignition pulses can only be produced at a maximum of every 2 - 2.5 ms, the piston will have moved 12 to 15 degrees after the first spark occurs. How much real benefit is there for this late of an additional spark? The obvious lack of benefit becomes more real as the RPMs increase."

I'm slightly familiar with the ignition system used in MB's modular engines. If I remember, each of the twin plugs fires approx. 12 crankshaft degrees apart. In addition, they fire alternately on each power stroke; i.e. a-b, b-a, a-b, b-a, etc.

Coincidently, this 12 deg. difference is the same spread you calculated for the MSD. My guesstimate is for emission purposes.

Most, if not all of these ignition boxes, cease multiple sparking above ~3000 rpm.

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

[Eugene at Pelican Parts]

Installing a Crane HI-6 seemed to worsen my already poor idle due to a maladjusted mixture. I have no factual data since I don't know if it was too rich or too lean at the time, but there was a slight noticeable difference in the manner by which it surged. Since then, I've tuned my mixture and the motor purrs smoothly again.

Anyway, I switched to the aftermarket box b/c my original coil was on it's way out and the HI-6 was a cost effective way to remedy the situation while gaining a reliable rev limiter too. I tested the limiter by setting it to 4500 and pegging the needle. Interesting how there is no 'limit bounce' at all with the new box. Anyway, I like the security of that feature and no longer feel uneasy about those 20 year old 'go at any time' electronics.

[Lorenfb]

If you need a good Bosch CDI, call Tom Gould at Pelican.
He's still got some in stock.

The M/B system is not a good comparision to the MSD, since it's
a twin plug system and a different process is occurring. In response
to my post about the pulse delay of 12 degrees, I assumed that the
MSD could "recover" from the first spark in 2 to 2.5 ms. It might be
much more or less. I doubt that they (MSD) have found the optimum
delay for emissions. They just run their pulses at a max rate and
the number is reduced as the RPM increases.

Let's get those MSD and Bosch units on a gas analyzer!

Have Fun
Loren
'88 3.2

[ideola]

Originally posted by jluetjen
I've got the Crane XR700 and an MSD6AL in my car and they work great. Incidentaly, the Crane XR700 replaces the stock points and the MSD6 replaces the ignition box. I believe that one of the big differences between the different MSD6 boxes is the inclusion of a rev limiter or not. I got it for my car for future use, but right now it's redundant with the stock rev limiter in the distributor. If you go with the Crane and MSD6, you will need to use a ballast resister for the Crane and a tach adaptor for the MSD.

This set-up gets my endorsement. I bought the car with the Crane equipment on it so I have no comparison for that. I added the MSD and compared to running without it, the MSD smooths out the idle and the engine pulls better below 3000 RPM. It also never seems to foul the plugs.

I realize this is an OLD post. However, I'm research the Crane as a possible replacement for the aging Hall-effect setup on the late model 924 2.0L cars. I am unclear as to why the MSD6A and the XR700 are required. Are you simply using the distributor modification pieces from the Crane stuff, and using the MSD for the ignition? Or have you somehow wired the Fireball box in with the MSD, and if so, could you elaborate on how?

[WydRyd]

I had no choice in the matter really. My OEM ignition system would not fire reliably under boost at heavy loads. Once I installed the Crane HI-6 unit, I get reliable ignition performance, even at 1.25bar of boost. Couldn't be happier. It even allows me to run a larger than stock plug gap. Stock is 0.024", whilst I now run ~0.030"-0.032" with the Crane CDI unit

[jluetjen]

Originally posted by ideola
I realize this is an OLD post. However, I'm research the Crane as a possible replacement for the aging Hall-effect setup on the late model 924 2.0L cars. I am unclear as to why the MSD6A and the XR700 are required. Are you simply using the distributor modification pieces from the Crane stuff, and using the MSD for the ignition? Or have you somehow wired the Fireball box in with the MSD, and if so, could you elaborate on how?

My car can run fine on just the Crane XR700. The previous owner added it to take advantage of the optical ignition trigger. But because of the combustion chamber design of my early 2.0 911, combined with the high dome 9.9:1 S pistons and cams with a fair amount of overlap, it was still a little rough below 3000 RPM -- for example when idling around town it was prone to popping and bucking. Once you got above 3000 RPM things would clear out and pull strong to 7000 RPM.

Adding the MSD system helped the <3000 RPM running considerably. Basically it's less prone to a complete mis-fire which is what was causing the other issues. The 2nd or 3rd sparks, even though they are retarded compared to the initial spark help to ensure that the mixture gets lit off for each cylinder.

Now a 924 2.0 is a completely differant animal and I would expect to not need the MSD.

1) The 924 has a Haron combustion chamber design where the head is flat and the combustion chamber is in a bowl of the piston -- similar to a diesel arrangement. This is quite different from the Hemi 911 head where the piston has a large dome sticking up into the head. In a 911 2.0 with a high-CR piston, the combustion chamber winds up being shaped like an upside down cereal bowl -- with a very long and contorted path to the edge of the combustion chamber, and poor squash performance. The 924 design on the other hand has a very compact combustion chamber design with the spark plug near the center and a good squash zone around the paremeter to promote turbulance in the combustion chamber.

2) I don't know what sort of cam profile you're running, but if you're still using the stock CIS injection system, chances are it doesn't have a lot of overlap to it.

In situations where combustion chamber is compact and there isn't a lot of valve overlap, I really don't think that the MSD will get you much of an improvement since the combustion quality will generally be pretty good. When it comes to performance improvements, the Haron design gets good marks for chamber design, but suffers from poor thermal performance (getting combustion chamber heat out through the piston) and restricted valve size and duration.

So I wouldn't bother with an MSD box in a 924 2.0.

[fred cook]

I put an MSD 6A in my SC 3 years ago. The car has run well ever since, even with the CO set at about 3% (pulls better on the top end). The plugs last a year without any fouling problems. I do a full service (plugs, dizzy cap and rotor, filters and valve adjustment) once each 12 months. My car is not a garage queen, but is used as a daily driver. It always starts instantly in hot or cold weather and maintains a nice steady idle. It even gets pretty good fuel mileage!

So, let's see....starts well, runs strong, good mileage, no twiddling between tuneups. Oh yes, for the price of a REBUILT Bosch CDI I got a NEW MSD AND a set of Magnecor wires. And it was easy to install!

Yep, I think the MSD is a keeper!