My Pertronix Experience...and engine timing - PeachParts Mercedes-Benz Forum

nhdoc · #1 10-21-2005, 11:15 AM

I installed the ignitor module and "flamethrower" coil in the '72 280 SEL 4.5. The install was fairly straighforward and, with the exception of having to splice in extensions to the wires provided by Pertronix on the module it went more or less by the book. After the install was complete I checked the timing and noticed it was somewhat retarded past where it was running on the old "points system" (It was reading about 10 degrees ATDC)...there was a change expected so I started to adjust the timing back to "spec" which is 5 degrees ATDC with the vacuum retard attached. At 5 degrees ATDC the engine seemed a bit sluggish and idle was a bit rough, but then it always has been since I owned it.

Then I noticed some prior tech had inscribed 0 BTDC on the valve cover and the timing mark at TDC was enlarged and painted, so, I thought to myself, why not try setting it at TDC instead of 5 ATDC? After I reset it the idle was somewhat faster, so I adjusted it back down to about 750. Now, the engine has more power, idles smooth as glass and has a seamless power curve with no dead spots and more power than it has ever had since I have owned it. It does not seem to run "hot" or ping or diesel after shutdown, in fact there are no adverse conditions created by advancing the timing 5 degrees so I will leave it there for now. I would be curious to see what effect it has on the fuel economy - combined with the electronic ignition I cannot imagine it would do any WORSE than the 11-12 MPG I was getting on it before (mostly around town).

I'll report back in a couple of weeks, but for now I am very happy with both the Pertronix conversion and slightly advanced timing mods.

page62 · #2 10-21-2005, 11:46 AM

The timing is retarded so far back for one reason only: emissions. That goofy vacuum retard is also there for one reason: emissions. My vacuum retard line "fell off" and improved the idle significantly.

It's a well-known fact among muscle-car owners that you can tune for performance...or tune for emissions.

Peoria Benz · #3 10-21-2005, 11:53 AM

Thanks for the post! I put a Crane conversion on my 280SL after the "ignition module" gave up the ghost. It significantly improved performance and drivability. My 280SE 4.5 runs reasonably well, excepting hot starts, but I am still interested in making it run as well as it can. I would love for others to share their experiences with any brand conversions for purely selfish reasons, though I am sure that many others would also appreciate.

JMela · #4 10-21-2005, 12:01 PM

Hey Marty. Did you get the hotter Pertronix coil as well? Some people have had trouble with the pointless setup and stock coil - sounds like you're doing ok. I've been a big fan of my Pertronix setup.

nhdoc · #5 10-21-2005, 01:14 PM

Quote:

Originally Posted by JMela

Hey Marty. Did you get the hotter Pertronix coil as well? Some people have had trouble with the pointless setup and stock coil - sounds like you're doing ok. I've been a big fan of my Pertronix setup.

Yes, as mentioned above, in addition to the ignitor module I went for the flamethrower coil. I'm not sure if it is any better than what MB used 30 years ago, but it works fine and this system seems to have a lot fewer components to go bad and no moving parts like points to wear out.

I removed the "stock" transistor box, 2 ballast resistors, coil and wire harness in addition to the old points. I'll probably keep the points and pick up a condensor so if the Pertronix fails one day I can revert back to 1930's technology again and get home.

I figured out that a second 12V "feed" wire for the old MB system came off the starter circuit so that during cranking the first ballast resistor was bypassed. Having the schematics helped out A LOT. I had to "cut and cap" that wire to keep it from causing trouble but other than that everything else stock came right out.

billrei · #6 10-21-2005, 10:30 PM

I have a Crane system in my W109. I bought a MSD 6A a capacitive discharge multiple spark ignition unit on eBay a while back. I'm going to use the crane system to trigger the MSD 6A. I also have a MSD Blaster 2 coil to complete the setup. The MSD 6A fires multiple sparks over 20 degs. of crank rotation up to 3,000 rpm. My hope is that this will yield better idle and improved gas mileage.

My commute to work is less than 2 miles so the engine bearly gets up to temp by the time arrive. I think I'm getting some oil dilution because of this. Hopefully this setup will allow better combustion during warmup to help with the problem.