The Electromotive SDI (Super Direct Ignition) for the LT1 engine is a two-part system that totally eliminates Opti-Spark and provides a true 'distributorless' ignition. It can be controlled by the stock ECM (computer), or timing can be programmed (somewhat crudely) in the SDI.

(I have heard Electromotive has a hold on the total system until they can get the controller to work with the OBD-II computers. Estimated release is 2 months.)

The following description is offered for information only. The author assumes no responsibility for the consequences of any actions by the reader. You should be aware that Electromotive has applied for CARB-EO approval, but does not have approval at this time. Hence, this system may only be used "off road". (PITA - but I want to protect my P.E. license.......). I have no connection whatsoever to Electromotive, except as a customer!

Opti-Eliminator (O-E) is 1/2 of the Electromotive Super Direct Ignition System (SDI). It includes a toothed timing wheel that mounts on the crank damper/hub, a magnetic sensor, and a small processor. The O-E replaces the optical portion of Opti-Spark (O-S). Note that if you only install O-E, you are still using the rotor/cap portion of O-S, and will still have the problems inherent to that portion of O-S. In reality, I think that there are more O-S failures with the cap/rotor section, since that is the part that gets wet first. The optical portion is under an inside cover, and better protected. Maybe grease/dirt gets in from the back??? I have never looked inside my O-S, and I will never have to..... :o).

SDI, the second 1/2 of the system, is a 4-coil pack with electronic controls, that looks very similar to the setup used on the Buick GNX, 89 T/A Turbo, and later GM V-6's. Each coil fires two plugs, one on each bank of the engine ("lost spark" method. One cylinder is on the compression stroke and fires, the other is on the exhaust stroke and does nothing when the plug sparks). New plug wires are required (this is the only hard part of SDI)

The price for the complete system, including O-E = $799 + shipping (shipping to NJ was $7)

Check the f-body forum message board. DaveW has a group purchase that may get it down to $600.

The unit is available directly from Electromotive at these prices. There are also "authorized" dealer/installers. For a complete insight into the installation of Opti-Eliminator and the rest of the SDI system, go to the Electromotive website at:

www.electromotive-inc.com (NOTE: Electromotive is still there, but the SDI page is GONE!!…I do not know why!!)

click on the "site map", click on "new products", click on "LT1 Camaro install...".

(NOTE - If you do not know a lot about what is in the OEM Opti-Spark, go to www.f-body.org, and look at the "Opti-Spark Dissection Page".)

There are also some good explanations of what SDI is on the Electromotive website. With the simplest SDI, you can choose between using your factory ECM timing (or HPP+, or other reprogrammed ECM timing) or a simple timing curve set by the SDI. The three dials on the SDI can set 1) initial advance, 2) advance slope from idle to 3000 rpm, and 3) advance slope from 3000 rpm to 8000 rpm. There is a fourth dial that serves as a soft rev limiter. Note that if you switch to the SDI-set curve, you will be bypassing the knock sensor/module in the stock ECM setup. As long as you stay with the stock ECM, you will have the benefits that the stock knock sensor and knock module provides. You actually have to unplug the connection at the OEM coil module to switch between timing methods, but I think I can wire it so I can choose from the driver's seat. I can use the "normal" ECM program, which in my case is actually the HPP+ map, for "normal" driving, then switch to the SDI set curve when I hit the nitrous. Switching to SDI-set timing may set a diagnostic code, however.

I completed the O-E install in September 1998. The system operated fine. The rest of the SDI was installed March 1999.

The instructions shown on the Electromotive website are the ones actually used to do the installation. This is a relatively simple project for anyone who has a basic set of tools and some mechanical inclination - for the O-E, 1 hour if you work normally, 2 hours max if you double check and insist on perfection. Installing the wheel on the damper is easy, unless you have an aftermarket under drive pulley. I have the ASP pulley/damper and it did not interfere with the installation of the toothed wheel. It is just a bit thicker at the bolts (to the crank hub), which moves the wheel forward, but that is compensated by the mounting of the probe.

When you install the wheel, there are three dual-threaded stud bolts that replace the factory bolts. The studs have one thread for the crank hub on one end, and a different thread for the wheel attaching nuts on the other. The hub threads are crimped to stop them from going to far into the hub. Watch out here! If the studs extend beyond the back surface of the hub, they could hit the Opti-Spark case and shatter it. The crimp in the threads is not real deep and too much torque will put the ends of the studs out the back of the damper.

I have seen the wheel on one S/C installation (Unstable Bob, 12# ATI), and the wheel sandwiched neatly between the damper and the S/C pulley. Some rework of the spacers was required. I suspect each S/C installation must be reviewed for suitability, but it should be possible with some creative thinking. For help with the S/C install, Bob Gable (unstablest@aol.com)

Installing the probe bracket on a couple of the water pump cover bolts is also easy. With the ASP pulley, I had to put a washer under each probe mounting bolt to move the probe forward, and get the probe centered exactly over the wheel - no big deal. Check the clearance between the probe bracket and the wheel. It is tight. I ground the pointy end of the probe slightly to match the contour of the wheel better. In the S/C installation, machining of the probe bracket was also required.

The electrical connections are simple. Just a couple of plugs - 1) probe to the control unit, 2) control unit to plug where the O-S output normally connects midpoint on the passenger side of the intake plenum. The control unit is credit card size, about 3/8" thick, and can be double-face taped to the intake plenum surface just behind the throttle body cover plate. There is a third wire/connection for the SDI coil pack if and when it is installed. The control unit has a couple of LED's on it, strictly for entertainment value. Helpful Hint: The control unit has an Electromotive label on it. If you want to keep your engine looking nice, cover the label with some clear tape. Other wise, as dampness gets to the label it starts to crinkle up.

Note that the wheel - to be precise - needs to be referenced to TDC. If your engine is running, you can approximate this with a timing light and a scanner. Normal timing at idle for the LT1 is 18-21 degrees (M6 at 800rpm, mine scanned 20-22 deg.) advanced. Put a mark (I used a small piece of tape, because you will need to move it) on your damper, fire up the timing light, and move the mark until it is directly under the probe while running on Opti-Spark. Then mount the toothed wheel so that the corresponding advance is located over the damper mark - there are 60 teeth and 60 spaces, so each tooth and each space is 3 degrees. I took a waterproof marker and marked the 'degrees' on the toothed wheel, up to about 30 deg advanced (not needed, but it helps). This should be checked with the timing light before you disconnect the O-S and hook up the O-E. Once you make the switch, the readings are meaningless, unless you have the wheel set right.

(The above steps work fine if your car is running - do not get worried about the paragraph that follows - TDC is only important in certain situations - my O-E works fine based on the above steps only)

An alternate to the above, and the more exact method, is to locate TDC by rotating the engine until #1 piston stops on the compression stroke. This is easy if your heads are off, but a bit more difficult if they are still on. I "think" this should be possible - put a stop in #1 plug hole, rotate the engine in both directions until the piston stops. (Use care, this is aluminum we are dealing with!!) The midpoint is TDC. Or....get a dial indicator in the #1 hole and try and measure it..... Or a third option suggested by a guy who builds engines. Get #1 Piston near the top of its stroke. Drop a valve on the piston (better be sure its near TDC!!). Then put the dial indicator on the valve, and move the crank back and forth to identify the points in both directions where the piston drops 0.100". TDC is ½ way between these points.

When you have accomplished this, you mark TDC on your wheel/damper. BUT....the stock damper hub is not keyed to the crank, and they have been known to slip when HP exceeds 400 HP, or when you attach a blower pulley. I bought a keyed steel hub from IRS and will install it when I do all the other stuff. The keyway already exists in the crank, GM was just too cheap to put a slot in the hub and install a key!!

(Back to the 'normal' install procedures)

Setting the clearance between the probe and the wheel was easy, but the recommended 0.032" did not work. The engine ran fine, but I was still getting DTC 16, low resolution pulse. The chief engineer at Electromotive told me to just keep opening up the gap until the problem went away. I set mine at 0.060" and have only had the trouble code occasionally since. I suspect under some abusive high rpm shifts the wheel might jerk around just enough, or that there is a brief period during startup where the control module is trying to synch to the wheel pulses. In any case, it synchs and the car runs fine. The only 'problem' is you have a 'stored' trouble code (not a current code).

The balance of SDI install takes some planning. The base (a gold toned billet 6061-T6 aluminum plate - very sharp) mounts on the valve cover bolts on the driver's side. This takes some adjusting - I moved my throttle cables above the fuel lines, and flipped the brake booster vacuum line up above the fuel lines, also - to make room. The holes in the mounting plate also need to be relocated to get the final location as far forward as possible, without going under the A.I.R. tubing to the manifold. Otherwise, you will have the coil packs so deep under the cowl that it will be hard to wire or to put in the rear bolts/spacers that mount the top coil plat to the mounting plate. I ended up with the base plate exactly centered on the valve cover, held on by the two center bolts. I put washers under the mounting plate, to simulate the washers that are normally under the valve cover bolts. Then you mount the coils/controller plate, also a gold tone billet plate, to the base plate. This puts the "control" end of the system very close and maybe even interfering with the AIR pipe/check valve. Gently pull the piping toward the fender. This will give you a 1/4" of clearance to the SDI.

If you have ASR, this location may not be possible, and you will have to look up front by the air intake box. If you have an aftermarket cold air setup, there may be some space available. If you have an S/C you will need to work on locating the unit. I think George, 30th Anniv. SS has a similar (Motec, not Electromotive) coil setup under the lower radiator support, because his Y-trim Vortech and after-cooler leave very little space under the hood.

You will need a universal set of plug wires, with HEI terminals, NOT the O-S type distributor end terminals. I bought Taylor 409's (in red!! - man, they’re fat). I also bought a set of eight braided fire-sleeves to keep the wires away from the JBA headers that I put in at the same time. Now you have to manage to route the four wires to the drivers side (1-3-5-7) - not too hard - and get 2-4-6-8 completely around the engine to the passenger side - this could be a challenge. I installed headers at the same time, so I can not comment on how to wire the unit with the factory manifolds. And, you probably can not use larger than 8mm plug wires if you use any of the factory routing.

With headers, do the passenger side wires first. Route them off the coil terminals toward the rear of the engine, go over the rear of the intake manifold, or even behind it, then split into two pairs, #2/#4 and #6/#8. Route each pair to the centerline of the space between the corresponding header tubes, then flare one wire forward and one wire backward to the plugs. For #6/#8, you will have to contend with the oil dipstick. Just work around it. To set up my routing, I got a bunch of nylon electrical tie straps, and made my own temporary "looms". For four wire packs, flatten the wires, wrap them with a long tie (11" or 14"), then get three small ties (4") and put them between the wires, wrapped completely outside the top and bottom of the long tie strip. You end up with a fairly rigid bundle. Do this several places along the wires, similarly when you go to the two wire groups, and you can "dress" the wires neatly and clear of the headers, etc. I plan to get the Taylor rigid plastic "clamp" type looms, made for the 409's, eventually.

On the driver's side, it is more awkward. The easiest way to come off the coils is to route the wires forward. You just have to juggle them past the AIR piping. Start with a group of 4, turn back and split into two groups of two, #1/#3 and #5/#7, and it should all work out. Actually, the universal wire sets come with the plug boots already in place, so you connect them first, route the wires, then crimp on the coil-end boots and terminals. If you want to use the woven fire boots at the plug ends, put them on before you crimp the coil-ends on.

DO NOT HOOK UP THE POWER UNTIL YOU HAVE HOOKED UP THE SPARK PLUG WIRES. The wiring connections are simple. I ran the red +12V power wire and the black ground wire all the way to the battery area, connecting the red one to the positive battery connection inside the little red plastic box, and the ground to the chassis ground in the same location. It is necessary to extend the wires by about 30" to accomplish this. Use the same color wire, at least the same gauge, and use a quality crimper to make the splices. The unit wiring appears to be 12-gauge. I bought lenths of red and black 10-gauge wire and ran the wire as close to the control unit as possible, then cut the control unit wires to the appropriate length. A clean power supply appears to be very important.

There are two connectors. The 3-pin Packard connector plugs to the matching 3-wire connector from the Opti-Eliminator controller. These wires are all way too long, but I'll trim them "later". The last connection is made by pulling the factory 4-wire connector off of the coil driver module sand plugging it to the corresponding 4-wire yellow connector/"box" from the SDI. This small box needs to be mounted somewhere, and I put it in the side of the throttle spring cover. Use very short self tapping screws, making sure they do not interfere with the throttle linkage through its full range of motion.

You must leave the dual connector on the OEM coil. In this mode, the PCM timing curve will be used, through the SDI coils. If you remove the connectors from the OEM coil, the timing will be set by the three dials on the SDI contoller. And...important....you will not have your knock sensor in the circuit.

You are now ready to fire it up. It may take a turn or two of the crank, but when it starts, you will not notice any difference between the factory Opti-Spark and the SDI, except that the SDI works!!!!

One might be tempted to ask, "why spend 800 bucks on this system - I could get my Opti-Spark replaced for less than that?" Good question - I'll try to answer it. The best price I have seen on a 'new' GM O-S is $250, from Dal at Lambert Buick-Pontiac-GMC. Ahhh, some people will say, "I can get a rebuild kit from NAPA for way less." True, but you will only have 1/2 of the parts you need - this is ONLY the cap and rotor, NOT the optical section. (If you are doing O-S, in spite of my warped logic, do it right and get the full O-S from GM.) Back to the question - you've spent $250 for the O-S, now you need to get it installed - you are looking at about 6 hours of labor. At shop or dealer prices we're up to 250+~400 labor, or more = $650-700. So what's the problem? You could even do-it-yourself and save the labor - but I've seen it take up to eight hours, and the people who do it still have problems when they are done. Getting the Opti drive aligned with the cam is way more difficult than it should be. One guy took three tries to get the cam pin (93-94 only) lined up correctly. Another had the two little Torx screws that hold the rotor on come loose.

Well, you now have a brand new Opti-Spark that will deteriorate and fail just like the one you just replaced. As Electromotive states - "there are only two kinds of O-S - those that have failed and those that are going to fail." With O-E and SDI you will have a super high performance, bulletproof ignition. You can play with the timing. You will NOT need an MSD (or Accel, or whatever...) box. If you've got an S/C or are using nitrous, the only thing better is DFI, and I think Electromotive can fix you up with that if you want.

regards,

Fred Forsythe

fredrick.forsythe@kvaerner.com