today I removed my opti from my 93. one thing I noticed is that the vacuum hose on the opti near the coil wire was run to and just lying along the injectors on the drivers side under the fuel rail cover. sure seems that this should of been hooked up somewhere but I don't even see where it would go. this cant be right?? where does this go?

 

Unless the previous owner installed a replacement opti with the
vacuum feature, the '93 did not come with a vacuum hose to/from the opti.

 

On a 95 Corvette it goes here.

 

interesting... the original opti on this car failed back in 2009 and I replaced it with a dynaspark. that unit failed after about 500 miles on it. sent it back to dynaspark and they fixed/replaced it, which is the unit in the picture below. this unit then failed after about 4000 miles on it. obviously dynaspark is not on my list of approved vendors. 4500 miles for a unit that cost $795 I did not do the work on it at that time as I was too busy so I had a shop replace the unit both times using the dynaspark that I had purchased.

as you can see from the photo the dynaspark unit has two vacuum hose locations. one near the coil wire input and the other with the blue fitting. the one with the blue fitting did have a hose hooked to it which ran with the plug wires on the drivers side of the engine. don't know where it goes or came from as I didn't look. I suspect it runs up the back of the motor to the top somewhere.

obviously makes me wonder if the open vacuum line that just sat in under the rail cover sucked stuff inside the unit which help cause the failure.

I will purchase a new unit from SAC City and hopefully it will last. they should warranty the opti for mileage not time. some of us just don't drive our cars much so mileage is a better reflection of wear then time is.

 

Dynaspark in its design updated their units to a second generation style with positive vacuum. The bottom hose runs to the drivers side of the intake manifold for vacuum and the top hose in the photo with the 90 degree connector runs to the intake tube as shown in the photo by MRPVette.

 

Here's a link to the Dynaspark installation instructions. The photo captioned figure A shows the location of the vacuum connection on the drivers side of the intake manifold.

http://www.dynaspark.net/support/Dynaspark_GEN_I.pdf

 

thanks for the info and perhaps the shop that installed this needed it more than I. but this thing lasted only 4500 miles so it is being replaced. I am not installing a dynaspark.

 

On a vented opti system. That bottom hose (blue fitting) is connected to the intake manifold, where there would be a fitting for it. There would also be two check valves in that area.

The venting system runs on vacuum from the intake, and gets it's air from the hose on the air intake coupler. A 93 intake would have that fitting for the hose, and probably why they just left it as they did. You would have to get that fitting and install it in tha manifold for the vent system to operate correctly. This could have aided in the early demise of these units.

 

if I run a non vented opti can I just plug the bottom hose off sense it wont be used?

 

The "gen 1" optis ('92 to '94) have (if I remember correctly) three holes at the bottom of the opti to allow condensation to escape and air exchange. So there is no bottom fitting for a hose to be plugged. I read that the original design actually had larger holes but to save money the size of the holes was reduced (I guess to save machining costs). This led to problems and was addressed in the updated design ('95-'96) which was vented.

I recommend you vent the unit as you already have the hoses (I believe they are $75.00 on Ebay) and it will make the unit more reliable. Here's a link to an article in Super Chevy showing exactly how to vent it with photos and detailed descriptions.

http://www.superchevy.com/how-to/16758/

 

let me be more clear. the replacement opti that I have is non vented for 1993 and does not have any holes for venting. I will not be venting this unit even though as you suggest it might help. I am just going to install it as is for right now. I might have purchased a vented unit had I known then what I know now. the opti that I took out was vented, although improperly which probably lead to its failure.

now having said that, there is a bottom vacuum hose that needs to be plugged as it is not going to be used. do you see a problem with just plugging it?

 

Plug it on the intake manifold.