what does an opti do?

[6spdLT1Bird]

hi i'm new to my firebird, and i LOVE it so far. i've heard people talking about their opti's and trouble they've been having.. what exactly does it do?

[Christopherrr]

Opties (is that right, LOL) are LT1's ignition system.

Here's a quick write-up:

What is the Opti-Spark Distributor?


When GM introduced the LT1 engine in the 1992 Corvette, it was a major advance in V8 pushrod engine technology. Reverse-flow cooling helped it run higher compression ratios on pump gas than ever before. Multi-port fuel injection with a newly designed intake allowed the engine to get incredible fuel economy while maintaining good top end power. Best of all, when GM started installing these engines in the 1993 Camaro/Firebird platform and the 1994 Caprice/Impala SS platform, true high-performance small block power was made available to the masses. For the most part, the LT1 earned every bit of the praise it received.

After people put some mileage on their LT1-powered cars, Opti-Spark Ignitions began to fail at a fairly high rate. Vehicles operated in wet climates were even more susceptible to problems. What was causing problems with the Opti-Spark?

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.

[Nightrage]

Don't worry. People make it sound like your optispark is going to crap out every other week. I'm at nearly 90K miles and to the best of my knowledge, my optispark has never been replaced. Steve93Z has 130K+ miles on his car and still has his original optispark as well, and his is the non- ventilated version which is supposed to be more of a problem than the ventilated optispark which were installed from 95+.

[Z Ya Later]

You just need to make sure you replace a failed Opti with a quality unit, whether OEM or aftermarket (like the DynaSpark or MSD units). Inferior replacements can cause a lot of headaches for you. But, if yours isn't broken, don't worry about it

[Injuneer]

You also need to make sure you do not get it wet. Do not spray your engine down with water. Do not steam clean it. Avoid car washes that spray under your car. Keep on eye on the water pump weep holes. If you get a drip there, it goes right down on the Opti harness connector, which is one of the most vulnerable places for leaks.

Make sure your "vent" system is connected properly and working. Shoebox has photos of all the connections on his website.

And I'm sure someone is going to respond by saying they pressure wash the front of their engine every week and never had a problem, but after owning one of these engines for 12 years, and working these forums for 8 years, I've seen too many horror stories from people that have had a simple drip, splash of coolant or a car wash ruin the Opti.

[6spdLT1Bird]

oh ok!! that really clears everything up for me.. thanks everyone. yeah i havent had any problems to my knowledge of my opti. if it does its a chance to upgrade

[casey02ws6]

what exactly does it do?

It breaks and leaves you stranded.....

[Jay 02 TA ws6]

It breaks and leaves you stranded.....

LOL... I was going to say the same thing

[thenuge876]

It breaks and leaves you stranded.....

hahahaha i was waitin for it