The GM opti is still the best unit out there in my option. Over the past few years we've had lots of problems with the MSD units more then any other.
Quote:
Originally Posted by Shownomercy
(Post 521716)
Why the LT1 hating... :|
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People hate the LT1/Opti becuase they just don't understand it.
The opti has two sides, the optical part, which is nothing more then a wheel with holes that are optically scanned to tell the EMC the position of the cam (Low Res), the other side in the cap/rotor ( High Res).
When left stock the units are not bad at all, the problems are heat and wear, same as any distributor.
Upgrading of the ignition system (MSD blaster coil) can cause them to wear faster, as well as additional heat in the unit which leads to failure. But most failures are simply from none service. you see allot of opti failures after cam swaps becuase people doing cam swaps and not checking the cam drive pin, it must be exact! Too short or long even by less then a 1/4" can result in catastrophic failure.
People are reporting 150+K miles on a stock unit. But think about, if you had a car with a traditional cap/rotor wouldn't you replace it every tune up/ xx amount of miles? So people complaining their opti went at 80K miles would be like anyone complaining they needed plugs and wires after allot of miles. Thing wear out! The cap/rotor on an opti need to be replaced just like any other cap/rotor. But few it because it's such a PITA!
The optical side is actually a well designed piece by itself, mating it with distributor was the bad idea! What happens in that the spark (or High Res) side results is heat that cause damage or moisture build up and also the sparking results in corrosive gases that can eventually effect the optical site (GM adding venting in 95 only helps slightly). Then they mounted down low under the water pump, with the weep hole right above it. So it can be splashed on or dripped on. Excess vacuum or boost bleeding back into it can distort the degree wheel causing it to make contact with the sensor. And one touch and the optical side it toast. (Ever see a DASD crash before?).
The cap/rotor is the real point or cause of failure, first it's large compared to a conventional rotor, high RPMs (above say 6800) and the rotors tend to tear themselves apart. Unlike a standard cap/rotor, people tend to not service the opti, and they wear and the voltage has further to jump from the rotor to the cap, results in more loose heat and erratic spark - which will eventually kill the Opti side, This heat and loose spark is what ends up killing the electronics.
Of course once you plan to start spinning above 7,000 you’re now into EMC problems as well. People using aftermarket computers can eliminate the cap/rotor and just use the optical part with great success. Once you've eliminated the spark side you've removed most of the units points of failure. Lots of people are spinning their engines over 8000 RPMs with no problem using only the opti side and remove coils/aftermarket DFI.
I have the Electromotive designed for the LT1 (they only made about 100 of these) which has a module that will convert the opti signal for the DFI. It uses a 4 coil pack (wasted spark system, it fires two cylinders at once, so one spark is wasted as it's firing against a cylinder with an open exhaust valve). Actually with some systems like mine you really only need to know where the cam is once, if you have that, you can determine everything elsewhere. With mine there is a crank position sensor, so once the ECM has stored the crank and cam positions, it can determine which injector to pulse and which coil to fire and reference RPM from the crank wheel. I plan to go a step further and get my cam signal via a standard distributor sensor (Rear mounted dist, but instead of a cap/rotor, it will just be a small signal wheel.
There is also a company that is very close to completing a system to use the LS1 system on the LT1. They appear to have designed a new timing cover that will house a cam sensor; they are just working on improving the crank sensor before it's approved from production. This system should solve all the issues with the LT1 ign system, Longevity and high RPM performance
