GCEZ28

I read the first dozen or so comments above so maybe this has been touched on already.
I like the idea of a positive pressure inside the optispark. I had the seal in the timing cover fail and oil got into my brand new MSD unit and destroyed it. I don't believe it would have if something like what divineprime above is describing. Would have saved me a lot of frustration.
Now maybe inverters and fish pumps is a little crude but I believe it would work.
just my 2 cents...

Kevin Blown 95 TA

No, inverters and fish tank pumps is retarded, and so is this whole thread. Sorry, but that is the truth. If something isn't right, then just fix it. Plenty of us have been running this '95 and later opti ignition forever without any problems, and doing crazy ****like that is just foolish. Granted the 94 and earlier ign needed some improvement, but '95 got it right. The system works if it is healthy, so just fix it the right way.

pgerst

Go on walkabout and miss a thread on one of my two "favorite" LT1 parts (oil pump drive being the other.)

My understanding of the GM design process was that the venting of the opti was done to mitigate the oil/water ingress. The high voltage and ozone in and of itself is not a problem, it becomes one when mixed with oil/water. So GM, rather than make it watertight, decided to negatively vent with engine vacuum.

The Dynaspark referred to earlier tries to solve the oil/water ingress problem by competely sealing the unit; in theory the vacuum vent is not needed. Seems to me the key to longetivity on a stock unit would be extra sealing on the cap and harness.

Skedaddle

I've seen it published, in a manual with a GM part #, that the vent was added to remove the ozone produced by the high voltage discharge. The ozone leads to rapid oxidation of the internals, rust get in the optical components, etc.

So far, no one has actually measured the vacuum level when the system is operating normally (no lines plugged up to contain vacuum). I suspect it's so low that the leakage becomes inconsequential.

As far as the vacuum leak through the shaft/bearing causing a rough idle, let's think that through. For air that enters through the vent hose, the MAF sensor has already accounted for it. For air that leaks into the case without having passed through the MAF sensor, there will be a BRIEF very slightly lean condition, that the PCM corrects by bumping up the long term fuel correction for each operating cell. Consider how many people substitute an breather for the closed PCV system air supply line, leaving that vacuum operated system totally open (3/4" hole in the valve cover) and introducing even more air that has not been through the MAF sensor. But no one complains of rough idle, because the PCM easily compensates using the LTFT's.

divineprime

Yep the ozone makes nitric acid when combined with moisture.

As far as the leak being inconsequential, negative.
My car has 105k, but the vacuum can vary from car to car with mileage etc.
So when I have the vacuum leaking, it really does make it idle rough and lack power. Perhaps not on your car. It's more like the computer is slower to adjust, because it is taking extra account of the difference. Immediately it clears right up when I plug off the two ports, intake and air inlet. My distrib holds no vacuum whatsoever so both ports are literally open when hooked up.

My manifold vacuum is steady at 19.9hg. When I simulate leak I get 19.7 sudden drop and stays. Repeated several times to confirm. Looks like the computer is adjusting to at least idle okay, but has **** poor performance.
A tigher motor may not even feel the difference, I agree.

BTC

I guess I'm glad I bought a '94 before the engineers went and screwed everything up.

Skedaddle

But you can't measure the vacuum on the Opti with the inlet plugged up. That produces a vacuum that is much higher than you will see with a correct, open line. All you have demonstrated so far is that there is a leak (on your specific Opti) when the vacuum AT THE OPTI is 19"HG. But how much does it leak at the actual vacuum operating level?

When the intake manifold has 19+"Hg of vacuum, the flow limiter causes sufficient pressure loss to reduce the vacuum level at the Opti. Remember, there is a pressure profile in the SYSTEM, ranging from full manifold vacuum at the intake manifold nipple, to very slightly under atmospheric pressure at the blue elbow on the intake elbow. The closer you get to the blue elbow, the less vacuum you will see.

bw_hunter

no, No, NO! That is not at all true and nitric acid is not the reactant the attacks the OPTI. Just because there is an O3 in the formula doesn't mean it got there from ozone.

Nitric Acid is formed from Nitrogen Dioxide reacting with water or Hydrogen Peroxide. There are other methods, sodium nitrate, etc but nothing with ozone.


What happens with ozone is an oxidation reaction. ozone oxidizes many inorganic materials, like the metals in the distributor cap terminals. ozone can also oxidize the plastic that the cap is mode from, ruining the dielectric properties and making it sensitive to moisture. The cap actual breaks down, chemically. The vent system was designed to simply reduce the concentration of ozone in the HV side of the distributor...there is no real need to eliminate it all.

divineprime

NO(2) + OH + M -> HNO(3) + M
Well this is a complex chemical reaction so picking part of it out to try and say it is wrong, is wrong. See 9:20-9:47[autostream]http://autostream.com/camaroz28/?page_type=firebirdplayerthumbnail&framepage=200&t ransactionid=1365219778-7118173127&posted_by=divineprime_www.camaroz28.com &youtube_video_id=lFCjaz6zHfc[/autostream]

bw_hunter

Believe me, I understand it is a complex reaction forming nitric acid. It simply doen't occur in the form that tech on the GM training video suggests.

If you don't mind, find another reference that shows the generation of Nitric acid from ozone. You'll see my point quickly.

Or, if you wish to look, don't. It doesn't matter to me.....

divineprime

Ozone does not create nitric acid itself. Nitrogen plays a very big part in the formation of ozone, and if water vapor gets stuck in the middle of ozone formation, various NOx compounds are formed.

divineprime

Now theoretically this is an additional advantage to an electrically vented optispark. Instead of pulling in moist outside air through the air inlet, the dry climate controlled air comes from inside the passenger cabin, under the dash for example.

shoebox

Cabin air in my car is not conditioned a high percentage of time. Unless the air is constantly controlled, I don't see it making much of a difference in the long haul.

divineprime

Generally we do control the climate as compared to under the hood on moist days. In rain or snow we have the windows closed, and defroster or heat on. In very hot humid weather generally speaking a fair number of AC users will be drying the air with AC. If my AC worked, I would lol.

shoebox

I put a gauge on the end of the opti fresh air vent line today. I used a tee, so it would not be a dead end, closed connection. No vacuum measurable. It will still build to ~9-10" if I close it off. This is with ~15-16" of vacuum at the intake manifold end. I alternated between open and closed connection at the opti vent line and saw no change in the manifold vacuum or idle. So it seems (at least on my car) that the opti vent system is not a cause for any issues with engine management.

I don't have a way to monitor actual flow of air through the vent system while in normal operation (maybe if I had a really small MAF... ).