the smart people at camaroz28.com all put their heads together for a while (some insanly huge thread I gave up, I couldn't even keep up with it)

anyway, its fairly priced and uses LS1 coilpacks, looks cool as hell and $700 isn't that bad. Especially concidering they are supposedly discontinueing the non vented opt- the vented opti swap will cost your around $4-450 anyway.
enough chat-
http://web.camaross.com/forums/showt...threadid=25146

dont say us F-bod guys never did anything for ya ;)
:steering:

pardon me if its a repost

 

dang, with the responce the billet opti got :rolleyes: , i thought this would be10x more popular

 

Trey, I read part of the post and it talked about people still using the optical trigger for the crank position. Has anyone looked at using a magnetically triggered Hall effect sensor? Since they both (in the end) trip transistors to signal crank location, I would think that one could use the magnetic sensor which shouldn't have the problems the optical triggers did...or was the issue just with the high voltage components in the module?

 

Some of us read both forums :yesnod:

 

the optical part has 2 tone rings on it... an inner with a low res signal for the injection and an outer for the engine timing.

thats always been the killer with the opti.

there is a school of thought that indicates once you remove the high voltage from the opti, it will last longer - no carbon tracing.

 

I talked at length to the engineer at Electromotive about the now defunct "Opti-Eliminator." One of the big problems in using another triggering methods is how to have a home "Do-it-yourselfer" find top-dead-center accurately on the LT1/LT4. Since the hub is not keyed, you can't depend on it being accurate even if you find top-dead-center; and, finding top-dead-center is not easy. Since the LT1/LT4 use aluminum heads and a piston-stop in the spark plug hole would be at almost a right angle to the axis of the cylinder, the piston stop will flex and move in the soft aluminum enough that finding top-dead-center is not accurate (keep in mind, we are talking less than 1 degree accuracy here). The engineer said he tried many different methods and didn't find one that worked. I suggested finding a dial-indicator that had an elongated tip that would go into the spark plug hole and reach the top of the piston at TDC. I never heard if he tried that.
When I had my heads off, I marked my flywheel, using a positive stop piston-stop, at TDC in case I ever need it.

Tom Piper


[Modified by Tom Piper, 9:39 AM 2/27/2003]

 

tom, i don't think that level of accuracy is necessary. the way tolerances stack up between timing chains, cam dowels, and opti, not too many LT1/4 engines are perfectly timed to begin with. especially if you have software to tune it, then all that matters is results (and staying out of detonation). getting TDC within one degree is more than i would hope for. (on engines with timing marks, i see 2 degrees off all the time, and that's just the tolerance between keyways, balancer, and pointer!)

as for injector timing, i've played with injector firing +- 5 degrees, and never saw a difference on the dyno (at WOT). so i don't think the timing there is ultra critical either.

 

One of the main reasons for moving the ignition trigger from the camshaft to the crankshaft is to get more accuracy and eliminate the timing chain slop.
As a previous post mentions, the Opti-Spark has two optical signals: low-resolution and high-resolution.
The low-res signal is used for fuel injection timing and "rough" ignition timing -- the engine will actually run with only this signal (no high-res signal), but at reduced performance. That is because all basic requirements are met.
The high-res signal is for more accurate ignition timing, it consists of 720 pulses (there are only 360 slots for the high-res optical sensor, but each slot creates a pulse for the leading and trailing edge) per camshaft rotation, which is 360 pulses per crankshaft rotation -- this is supposedly one degree of accuracy. Accordiing to literature I have read (I think the article was written by Ray Bohacz), the Opti-Spark is dynamically adjusting the ignition timing of each cylinder individually and is therefore supposed to be extremely accurate even with the timing chain slop.

By the way, here is a link to the description of the now defunct Electromotive Opti-Eliminator: http://members.aol.com/InjuneerZZ/Emotive.htm

Tom Piper


[Modified by Tom Piper, 9:39 AM 2/27/2003]

 

As far as ways to find TDC with the heads on, we have an old spark plug that we have welded up, adding enough material so that it acts as a stop. We then install a degree wheel, and rotate the engine in each direction until it hits the stop. Note the two measurements on the wheel and find the centerpoint between those two stop measurements....that's TDC. Since it's a differential thing, it doesn't matter how you install the degree wheel.