LT1 MSD Ignition Coil

[karr95]

Anyone have any expierience with the MSD Ignition Coil?

I have 95 TA and recently replaced the Opti, Plugs and Wires and would like to change out the coil as well.

Does the car driver smoother, a little stronger, easy to install, etc.

Thanks

[Squirrel]

i have a blaster in my car, dont really think it improved anything...but cant hurt to replace a decade old more than likely stock coil with a little hotter new one

[Fasterthanyou]

The coil almost never increases anything. The only time a higher voltage coil will help is if you are running large gaps on your spark plugs. Other than that there isn't any improved spark energy going into the plugs because the ignition module is the limiting factor. The ignition module controls the switching of the coil on but inside it has resistance to limit the current going to the coil. Most are like 8amps so no amount of coil will increase spark energy, only jump larger gaps (what higher voltage coils do).
Also the "modern" e-field coils like the ones that were used on the GM HEI setups don't go bad. They are nothing more than metal wrapped into a form. A coil can only go bad when the windings get damaged but that takes dedicated effort. Fire won't even destroy one, you'd have to short it out until it's welded itself into a solid copper ball for it to be damaged. Trust me, these things are robust and if your coil goes "bad" you'll usually find that it was actually the ignition module shorting out or loose wire connections. For this reason I always make it a point to clean every mechanical wire connector during a tune up!
The real ignition upgrades come from upgrading the ignition module to something that can handle more amps. Even that is usually pointless when the REAL bottle neck in a single coil setup is just that, it's a single coil setup. DIS wasted spark and CNP/COP ignition setups are REAL upgrades with REAL results. Also the CDI ignitions do help increase gas milage and low speed throttle responce by using multiple sparks but really they only do the multi spark to make up for the fact that they can't spark long durations like stock HEI inductive setups :) . Trust me, a coil isn't worth it, upgrade to CNP and you'll have an ignition system that'll never need upgrading and you can run gaps of nearly .065 compared to .045.

[ar0ck]

http://www.delteq.com/products_opti.htm

LT1 OPTI-DIRECT IGNITION SYSTEMS

In order to understand the problems with the Opti-Spark Ignition, a brief description of the system is necessary. Quite simply, the Opti-Spark was a new distributor design that debuted on the 1992 Chevrolet Corvette LT1 V8. All LT1 (5.7L) and L99 (4.3L) V8 engines made between 1992 and 1997 were equipped with the Opti-Spark distributor. This would include all 1992-1996 Corvette, 1993-1997 Z28 and Trans Am/Formula Firebird, and 1994-1996 Caprice, Impala SS, Buick Roadmaster, and Cadillac Fleetwood applications. The Opti-Spark distributor was driven directly off the front of the camshaft. Consequently, the LT1 and L99 engines featured many design changes from the "old-style" small block to accommodate the new "front-mount" distributor location.

The term "Opti-Spark" describes the two functions of this distributor: optical ("Opti") engine speed and position sensing, and high voltage ignition distribution to the eight spark plugs ("Spark"). To perform these tasks, the Opti-Spark distributor contains a high-resolution engine speed encoder, a low-resolution engine position encoder, and a standard distributor cap and rotor assembly.

The high-resolution encoding is done with a 360-tooth trigger wheel spinning at camshaft speed. An optical sensor reads these spinning teeth, and creates a simple 0 or 5 volt signal, depending on whether an opening in the teeth is or is not present. As the trigger wheel spins with the engine, this 0 or 5 volt signal becomes a square-shaped voltage signal, or "square wave" in technical terms. This signal is then sent to the engine management computer to determine engine speed.

Once the computer knows the speed of the engine, it needs to calculate the engine position in order to establish spark timing. To accomplish this task, the low-resolution engine position encoder disk is utilized. The low-resolution sensor itself is essentially identical to the high-resolution sensor. However, the low-resolution encoder disk only contains 8 teeth. Four of the teeth are of the same size, and occur at 90-degree reference intervals (these four teeth help to give quick synchronization during start-up cranking). The other four teeth have varying tooth widths. From these variable-sized teeth, the computer uses a fairly simple algorithm to determine engine position.

The data created by the high- and low-resolution sensing system is ultimately used by the engine computer to generate one thing: ignition timing. The timing signal is sent from the computer to the ignition module, which is located next to the coil on LT1 and L99 engines. The ignition module then sends a high current “charge� signal directly to the ignition coil. Once the ignition coil is charged, it fires a high voltage electrical charge to the Opti-Spark distributor cap. The rotor inside the Opti-Spark distributor then distributes the spark to the appropriate cylinder via the distributor cap.

There are two slightly different versions of the Opti-Spark distributor manufactured by GM. The first design version was made between 1992 and 1994. Other than some small vent holes, the first design Opti-Spark had no provision for evacuating built-up moisture. Also, the caustic ozone gases created by the ignition process were also left inside the distributor with no vacuum removal. This design was replaced in 1995 with a vacuum-vented Opti-Spark (1994 B-Body cars received the updated Opti-Spark before the F-and Y-Body cars). Along with the new venting provision, the second design featured a redesigned cam drive and a different electrical connector.

In theory, the Opti-Spark design is good. In fact, high-resolution engine speed sensing leads to extremely accurate ignition timing, and was a rare occurrence even on high-dollar sports cars back in 1992. In practice however, quite a few things are problematic with GM's execution of the Opti-Spark distributor.

First and foremost, there are the typical wear, heat, and moisture problems associated with a distributor cap and rotor. Since most Chevrolet V8 engines feature an easily accessible rear-mounted distributor, it is not a big deal to change the cap and rotor every 50,000 miles (or sooner in high performance applications). Plus, the availability of standard-style cap and rotor assemblies makes them extremely cheap. These facts do NOT hold true for engines with the Opti-Spark distributor.

From an accessibility standpoint, both the water pump and the crank pulley need to be removed in order to gain access to a failed Opti-Spark distributor. On Camaros and Firebirds in particular, this is not a quick (or fun) job.

From a reliability standpoint, the environment at the front of the engine is notoriously harsh for things like heat, water, and debris (not to mention other variables like leaky front crank seals and worn, leaking water pumps!), but the Opti-Spark distributor is not even sealed on 1992-1994 models! Later versions of the Opti-Spark incorporate a seal and venting provision, but are by no means free of problems.

From a cost standpoint, the Opti-Spark units can retail for well over $400, depending on model year. Dealers have been heard to quote over $1000 (parts and labor) to replace this item!

To add insult to injury, the Opti-Spark distributor uses a "Correct-a-Cap" design that places the spark plug wire terminals on the proper side of the engine for easy spark plug wire routing. To do this, the terminal traces molded into the distributor cap must come extremely close to one another, which leads to premature arc-over in high-load applications and applications using constant high-voltage (Capacitive Discharge) ignitions. Not good.

But not all is defective on the Opti-Spark distributor. Inherently, the optical sensors are fairly robust. For most applications, the sensors are not the cause of most problems. To prove this fact, Mitsubishi manufactures the Opti-Spark sensors, and variations on these same sensors can be found on most late model Mitsubishi and Nissan applications. Reliability problems with the optical sensors on the Nissan and Mitsubishi vehicles are simply not present in anywhere near the same quantity as the LT1 and L99 engines. This would suggest that the main problems with the Opti-Spark distributor are not the sensors, but the cap and rotor.



http://www.delteq.com/New%20Images/vette_coils_lg.jpg

Im doing this very soon. Â*I have a feeling my Opti is knocking on heavens door, due to a not so quick start up. Â*This system blows away any LT-1 Opti Ignition systems on the planet!