VDI Help

[89fc3s]

I am just entertaining the idea on the wheels. Will they fit under stock fenders? And what would cause the VDI to not work?

[NoDOHC]

The VDI (the actuator on the intake manifold) requires the car to be driving to operate. IT is controlled by the ecu using a solenoid valve. If this valve fails or the air pump that supplies the pressure to operate the VDI fails, you have no VDI. A lot of emissions removal schemes end up going awry and costing 25ish Hp by making the ports and VDI disfunctional.

There are several fitment threads in the wheel and tire section, but the short story is that you will have to roll the fenders to run 17X9s, the 17X8s fit ok.

[Rotary Related]

Originally Posted by 89fc3s

my VDI doesnt work emissions are intact. How do i narrow down the problem?

and i know 17x9 will fit just will it fit with the offset?

First check the vacuum hose that supplies pressurized air from the ACV to the 6PI and VDI solenoids. It is located on a nipple just behind the main large hose from the airpump and comes out perpendicular.

Follow that hose. When you get to the rear of the engine where the smog racks are bridged by vacuum hose that's where a hose is probably broken or fallen off.

Next move to the solenoid side of the engine. If the ignition is on and engine not running you can use a probe and ground the colored wire (Not the black wire that is a power wire. It has a white or yellow stripe.) of the VDI solenoid and you should hear an audible click when it opens. If no click then you either didn't get a good ground or your not getting power from the ECU to the black wire on the solenoid. Check for 12V on the black wire if this happens.

Check all the hoses you can get to. Basically the air travels out of the nipple at the ACV through the rack then splits and feeds both the VDI and 6PI solenoids. then out of the solenoids and to their respective diaphrams to open the ports or VDI.

[TitaniumTT]

Good info here, apologies to the thread starter for the drifting sidetrack

[89fc3s]

it happens. If i take my uim off to check all the pipes under it will i need a new gasket??

[Rotary Related]

Originally Posted by 89fc3s

it happens. If i take my uim off to check all the pipes under it will i need a new gasket??

In theory yes! Sometimes you get lucky and it stays stuck to one or the other manifollds intact. In that case you might be ok. Buy the reusable ones available on ebay. I've had mine for 3+ years no problems. I'll warn you that you need to actually torque the manifolds to spec if you over tighten the reusable gaskets you will smash them rendering them not reusable. They cost like $30 or something like that. One for the lower intake manifold to the keg and one from the LIM to the middle manifold. sometimes called the upper maniolfd. When taking it apart the middle "s" manifold stays attached to the upper with the plenum and throttle body. All comes off as one piece. It keeps you from purchasing gaskets everytime you take something apart!

They sell tham as heatsheild gaskets or something like the Hondata heatsheild gaskets for Honda engines. That part is negligable. You are after them because they can be reused over and over, but only if you use a torque wrench!!!

I went through this whole proccess years ago. Nobody knows how to make S5 NA motors work correctly. I've seen it all from backwards one way valves to all the hoses switched all around where they jump across to the smaller smog rack on the manifold side of the engine. BTW the factory manual picture is wrong so use it as a guide not as an exact picture of where you need to be. I've been thinking about doing a write up on this topic for some time now as there is so much mis information out there on S5 NA motors.

Most people have no idea that their engine is missiing about 25hp or so due to incorrect vaccum line hook up.

Also buy some good hose like verosious motorsports sells on ebay. "platinum cured silicon" is the best hose for the money hands down. Not that cheap silicon hose everyone else sells. This stuff can be bent at 180 degress and wont collapse. I have had mine on my car for years and everytime I unplug a hose it "pops" right back to the shape it was before I put it on the engine. My car sees maximum abuse from drifting. If I can't break it then no one else will be able to either.

I'll think about a write up......adds to my list of a million things to do.

[NoDOHC]

/\ good post!

I use the reusable gaskets too, it sure is handy.

You can use Aviation gasket sealer or some equivalent when you assemble it with the old gaskets.