Which Ignition System?

[Yellowbird RS]

Which one would you choose: Crane XR735 VS Petronix to use whit a MSD 6AL wiht RPM and timing adj switch.
my car 1974 911 2.7lts. CIS


VS

[Lorenfb]

You forgot the "standard" and the most reliable, the stock Bosch unit.
Why would you waste money on something that provides no REAL
benefits? If need be, waste it on a carbon fiber shift knob!

Also, you're not happy with the Porsche timing map in the distributor?

[pwd72s]

Hooboy...here come the flames! But yeah, me too...running the stock and original CD unit....I recently did cheat a bit on the dizzy tho...from stock "S" with it's backwards point to a 2.7 RS dizzy, pertronix ignitior. Bottom end seems a bit better with the RS curve.

[araine901]

I say the MSD with the pertronix. I have that set up on my car. its been there for 7 years no problems and works much better than the purmatune that was on there when I got it and the new one I replaced it with.

I have heard many people that like the Crane, But I have no personal experiance.

The guys at Andail turned me on the the MSD. they were recomending it for carb cars that were hard to tune(not sure about CIS). The pertronix works great as a trigger. At the time they did not make a unit for my distributor. So I sent my core into them before I sent it back to the shop and for $20 they custom made the set up for my distributor. Not bad.

Cost may be an issue too. Why would you spend more for the Bosch when it provides no REAL benefits? Jegs sells the MSD 6AL for $195.99, the pertonix ingnitor is like $75 and Performance sells the Bosch for $1695 new or $695 Reman.

But, all things being equal, If I had more money than brains I would to the Bosch. But since I have not very much of either, I did the MSD.

[Lorenfb]

Some people get sucked into the marketing hype without any REAL technical
backup or fail to understand the technicals. Read the Technical page on this
web site (www.systemsc.com) about Ignition Systems.

Bottomline: There's NO technical theory and/or data which supports the
marketing hype of the multiple spark ignitions. As I've said many times;
"If the MSD types were that great, why hasn't Porsche and others adopted
this approach?" The answer is that it has NO merit/benefits.

Furthermore, many of my customers have had problems with these
ignition systems, i.e. the R.F. noise generated affecting internal voltage
regulator type alternators.

From the cost standpoint, Pelican provides Bosch rebuilts for $350
which eliminates all the mickey mouse drilling, wiring, and ugly non-
stock engine compartment. The MSD installation makes the Porsche
engine compartment look as if it's waiting for a Chevy 350 installation!

Marketing Hype: "Always tell the consumer two or more for the price
of one is always better."

[araine901]

Loren:

I apologize if I hurt you feelings. I completely agree, the multiple spark theory is a dodgy one at best. In reality it can only be a multiple spark at a very low RPM. Over just a few thousand RPM the multiple thing becomes irrelevant (stuff happening too fast to really act like a multiple spark). Therefore acting like any other CDI (big fat spark). In fact I would be surprised if it really even did discharge in multiple sparks. Like you I never bought into the muiltiple spark aspect of the MSD, i just got it because it was a CDI under $200 and the guys at Andial had had good luck using them on carb and MFI cars that were having a hard time passing smog with the Bosch units.

I am not sure your going to find any data that will justify a performance difference worth the 850% cost differential, but I could be wrong again. I suppose it is possible that the bosch unit works 850% better.

As to why aren’t they using it? Let’s face it; Porsche is not always on the cutting edge of technology. They tend to stick with a design much longer than they should. (Rear engine sports car, hello) Don’t get me wrong I love mine. I am reminded of a composites engineer I used to work with. He went from Arrows F1 to Porsche to develop the composite chassis on the GT1. He was a cocky British/German bloke and when he walked into the race shop at Porsche on his first day and saw the prototype he said “Well at least they got the engine in the right place this time”. Not knowing that Norbert Singer was standing behind him. Well, that went over like a fart in church and as soon as he was done with his projects he was working in our shop, now shares his opinion freely at BAR F1.

Is there an advantage to the multiple spark? I doubt it. To me its just another CDI. Is there a justifiable reason to spend $1695 on a new bosch unit? I doubt it. unless it a concorse thing.

[Lorenfb]

As I said, you don't have to spend $1700 for a Bosch unit.
Besides Pelican, there are many sources here in the U.S.
for rebuilt units which are as good as new ones. For the
additional $100 cost for a rebuilt versus a MSD, is it really
worth all the extra work and parts (tach interfaces)?

The multiple spark system is very simple to design-in and
would not cost much for any OEM car manufacturer, besides
Porsche, if it had benefits.

[araine901]

Go Bosch!!! Taste great and less filling. Does Bosch Still make that Unit? Why 1700 new? That has to be a supply and demand thing. It cant cost them that much to make after all of these years. The tooling must have been paid for years ago.

[jluetjen]

I've got the crane unit on my car and it has been absolutely trouble free. I can't speak to the Petronix.

I also installed an MSD on my engine and below 3000 RPM it has significantly cleaned up the idle and smoothed out the pulling -- in both cases I suspect due to fewer mis-fires. It really is a night and day difference below 3000 RPM. Before the car wouldn't pull from below 2000 RPM without bucking, now it pulls smoothly from below 2000 RPM. Above 3000 RPM, the MSD doesn't seem to make a difference. Hopefully I'll be able to get the car on a dyno this summer and do a quick before and after with the MSD to quantify the difference.

[fred cook]

Hey Lorenfb,

Your record is stuck!


Respectfully,

Fred Cook
'80 911SC coupe (currently (pun intended) running with an MSD system)

[chuckw951]

You might also consider the electromotive HPX ignition system. It allows you to set custom ignition curves.

http://www.clewett.com/products/ignit.htm#single

Easily upgradable if should decide to twin plug the motor down the road.

[dean]

I liked the rev limiter on the MSD unit better than stock.