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Old 10-03-2012, 03:33 AM
The Chemist The Chemist is offline
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MSD Street Fire CDI Ignition

Fellow Hot Rodders,

I have a 1976 Mercedes Benz 450SL Roadster. I Know, not your conventional "Hot Rod". The engine is a 4.5L OHC Mercedes Benz V-8. There arent a lot of OEM performance parts, so I've had to fabricate most everything. I took tke intake, cut it in half laterally and reworked the runners, polished all the ports and built vortex generators into the runners. I also custom built the entire exhaust including headers. I worked over the heads, porting and polishing the intake and exhaust. Because this is a factory high performance engine from MB (The 450Sl is the little Hardtop/Convertable) the valves were as big as they could be made. Fuel delivery is via a nearly 40 year old Bosch "Jet-Tronic" Direct port injection. Its a hybrid electronic/mechanical injection unit. I massaged that by modifying and installing injectors from a 5.0L Mustang GT engine. I had 2 cams custom ground because you cant buy aftermarket cams for this engine. Its an old 3 speed automatic, so I designed the cams to have good low end torque and power, but mostly to perform over a wide RPM range. This car has a passing gear that will put you in the seat from 40 MPH all the way to 120 MPH. The tranny is geared for a long 2nd gear like this, so I gave the cams a wide RPM range...

Now to the subject... The original ignition was an old electronic single spark Bosch electronic ignition which worked pretty good. Almost good enough that I left it on there for quite some time. However, I recently installed a MSD Street Fire CDI Multi Spark Ignition and I can describe the performance increase in ONE WORD... WOW!!!!!

WOW!!!!
WOW!!!!

This little car weighs in at nearly 5000 Pounds, so it never was a quarter-miler, and still isn't. However this ignition increased the low end UNBELIEVABLY. The most demanding part for this engine always has been to get the lead sled moving from a standing start. Its a small displacement engine, so you don't think of a lot of low-end 0-30 MPH pulling power. However, this car is capable of top end speeds in excess of 170 MPH. While the MSD didnt increase the top end top speed, it did DEFINITELY shorten the amount of time it took to get there. Also, in 1st gear, from 3500 RPMs to 5500 RPMs this little (5000 Pound) car absolutely tears #*@& (butt). When it hits the power at about 3500 RPMs the *** end will absolutely dance. But the real difference is in that LOOOONG passing gear. From 70 MPH, you floor it and it shifts down to 2nd gear. By the time you look from the road to the speedo, you're doing 100+. If you hold it in second, it will still shift to 3rd at 6250 RPM and when it does shift to 3rd at 6250, you're doing over 130 and when it shifts it LURCHES forward and again, you look from the road to the speedo and its at 140+ at 4500 revs and the tach is just a blur. The speedo only reads 160 and at this point I don't take my eyes off the road, but at 5500 revs the speedo is pegged out and the car is STILL rocked back on its hind quarters. Unbelievable!!!

The increased performance I got when I swapped the ignition to the multi spark is truly unbelievable.

You havent truly lived until you've been 160+ MPH in a nearly 40 year old car!!
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