Stage 2: Custom 2.5” Discharge Tubing

For the straight Throttle Body cars (1999+ model years) it very easy and affordable to ditch the cone filter than comes with your RKSport kit and integrate the stock air box into the Super Charger intake. This yields two major results. The first thing that happens is your super charger will no longer be drawing hotter engine compartment air but rather colder air from outside the engine compartment. The second benefit is that there is no further a risk of getting water into the low riding cone filter.

Parts Required: Two FEET of 3.5” diameter Flexible Intake Tubing from www.powerdyne .com You can not order it online but go to the website and get their phone number and call them. It is about $17 per foot. It may look like plain old flexible tubing but it is actually very strong and built to stand up the engine compartment temperatures. You will need less than a foot of 3” (BLACK) PVC pipe and a 3” (black) PVC coupler. (two female ends for joining two lengths of PVC pipe.) Any hardware store has these things. You will also need three large clamps. (normal radiator/furnace ducting clamps work fine.) A little RTV silicone or PVC pipe dope as insurance.

Stage One: 3.5” Powerdyne Flex Hose used to integrate stock air box/air lid on ‘99+ cars.

I already had the PVC piping and coupler as they are what I used to perform the smooth air lid/smooth air bellows mod. All I did was trim down the ‘coupler’ portion of the smooth air bellows to the minimum length required to make the connection from the air lid to the flexible intake tubing. Below are some before and after pics of the ‘smooth air bellows.’ After I cut down the ‘PVC Coupler’ section of the bellows to about 2” worth of coupler it was good to go. The reason I use a coupler AND a 4” piece of 3” PVC pipe is because the stock flexible rubber ‘accordion’ coupler on the air box is slightly larger than 3” ID. It fits perfectly over the 3” coupler, however, as the couplers ‘OD’ is greater than 3”. (In order to connect two sections of 3” PVC tubing.) The 3.5” Flexible intake tubing you are getting from pwerdyne.com has a 3.5” ID that fits perfectly over 3” (black) PVC straight pipe. What you are making is a tight and pretty smooth transition from the FEMALE end of the stock rubber air lid accordion and the FEMALE end of the Powerdyne flexible intake tubing.

Before (PVC smooth air bellows) After (Sawed off PVC smooth bellows)

From the above pic you can see what remains of the 3” PVC coupler after it has been sawed down to 2”. The COUPLER is has an outside diameter that mates perfectly with the rubber accordion on the stock air box lid. The 3” PVC pipe has an outside diameter that mates perfectly with the 3.5” Powerdyne flexible intake tubing. You can use a thin layer of RTV Blue silicone or PVC dope to ‘glue’ the two pieces together. You only need about 2” for either end for a total of about 4”.

Here are a few more pics of the ‘stubby bellows.’

After you make the cuts in the PVC tubing and the PVC coupler don’t forget to burr the edges smooth and you need to WASH THE SETIONS of PVC pipe and the COUPLER several times in warm soapy water to remove dirt and debris and shavings before you install them on the car.

When you have done this much you should test fit the Powerdyne flexible intake tubing and the air lid and your new PVC transition section. If all is good to go you can now use some RTV Blue Silicone (a very thin layer) to ‘glue’ the PVC COUPLER and the short section of PVC pipe together or you can also use plumbers PVC pipe dope. Let the section dry while you continue on to the next step.

Connecting the 3.5” Flexible Intake Tubing to the Super Charger:

Two feet of the 3.5” Powerdyne Flex tubing is long enough to go from the air lid to the Super Charger. I did not feel comfortable doing so, however. The Powerdyne flex tubing is pretty sturdy stuff, but it is difficult to bend it at very sharp 90 degree bends if there is not enough clearance. When you are stuffing the flex tube down between the radiator fans and the blower intake port the flex tubing ends up getting jammed up into the radiator shroud/radiator fans. This very tight fit could easily cause the flex tube to suffer rips and tears just during the INSTALL of the flex hose let alone after a few days of rubbing against the fans while driving the car. You will see what I mean. My solution to this problem was to use the HEAVY RUBBER 90 degree Elbow that comes with the RKSport kit that is used for connecting the cone filter. You already have a clamp for it and it is sized for connecting to the blower units intake port. It is also VERY strong and soft and flexible as well. It will readily fit down between the Blower Unit and the radiator fans with just a little compressing/squeezing. Take about 4” of BLACK 3” diameter PVC pipe and use it as a male coupler between the 90 degree rubber elbow and the 3.5” Powerdyne flexible intake tubing. You will need two clamps for this connection as well. Voila.

Check it out:

Do a pre fit of the entire new intake system and then trim down the Powerdyne flex tubing as required. I ended up cutting about 4” off of the two feet I ordered from powerdyne. It looks in the picture above like there might be some clearance issues with the hood and the tubing everything fits just fine.

Here is a pic of an aftermarket smooth air lid and stock air box integrated into a 1993-1998 angled throttle body car. I don’t think an aftermarket ‘v6’ air lid will work if you have a straight throttle body car. There may not be enough room between the end of the air lid and the discharge tubing. But, a ‘v8’ aftermarket air lid has the exit port in the ‘center’ of the air lid rather than off toward the drivers side. This will yield greater clearance. Thanks for the pic MT.

Parts in order: Blower Unit, 90 degree rubber intake elbow (rksport), 90 degree steel elbow (rksport-cone filter rig), about 1 foot of 3” Powerdyne flexible intake tubing, after market air lid.

If you are interested in integrating the stock air box with the discharge tubing from a 1999-2002 RKSport kit you will have to either get all new discharge tubing similar to what I detail below or you will have to cut up and use sections of your rksport discharge tubing along with a combination of silicone couplers and/or some sort of flexible section of tubing or some cutting and re welding. Take a look at this pic of the discharge tubing comes with 1999+ kits. To use it you have to totally remove the air box lid and the cone filter is a MUST USE unless you do some serious modification. Look at the pics below and you will see what I mean.

Side View: Note that there is a fat TB spacer in use between the TB and the Intake Manifold. This pushes the discharge tubing further out over the air box. If the TB spacer was not there you can see how the tubing could possibly be cut and changed along with the use of some type of silicone couplers and/or high pressure flex tubing. Thanks for the pics ‘uncharged.’

Note: Quite a bit of material in the rear of the air box frame can be cut away and ‘clearanced’ to make for better fitment of whatever discharge routing you come up with. So to can the fan shrouds be cut and clearanced. Just make sure you don’t cut too much of the fan shroud away and thereby cause the fans to get stuck on the intake or discharge tubing.

Here is an example of a ‘V8’ air lid. Notice that the discharge port is centered rather than off to one side as with the ‘V6’ air lids. The V8 air lid mounts perfectly on a v6 air box.

Stage Two: Modifying a 1993-1997 RKSport kit (angled throttle body car) to a 1999-2002 (straight throttle body car)

As well as modifying a 1999-2002 RKSport kit to work with the above ‘stock air box integration mod.’

If you want to save some considerable money by buying a used RKSport super charger kit you can easily adapt the different ‘throttle body’ model year kits to fit your specific year vehicle. For instance, I modified a 1993-1997 (angled throttle body) kit to fit my 2001 straight throttle body car for just a few dollars worth of silicon couplers.

For those who have a ‘99+ car and also have a ‘99+ kit but want to integrate the stock air box into the super charger intake system you can do something very similar to what I will describe bellow. You can choose to cut up and integrate your ‘stock rksport’ 3” discharge tubing or you can easily and affordable use all new tubing and silicon couplers. The choice is up to you.

(I chose to leave the ‘stock’ rksport discharge tubing alone. It is still sitting in a box, ready to go, un-changed and ‘whole’ if I ever sell the kit. If I do sell the kit, however, it now supports 1993-2002 vehicles with no further modification.)

Brief Disclaimer about the 2.5” discharge tubing: I know…using 3” tubing would be better. I did not want to cut up the stock rksport piping (for whatever reason) and I simply could not find a 3.5” to 3” high temp silicone reducer elbow. (at least not for less than 60 bucks or so.) I also got a very good price on a few feet of the ‘McMaster’ 2.5” high pressure flex tubing. If I could (in the future) find such a reducer I could easily use 3” pipes and some high pressure 3” silicone lined flex hose to make a ‘3” discharge system.” However, the 2.5” diameter discharge tubing system I built works very well. It is strong, does not leak and delivers 6psi to the intake manifold at 6000 rpm with an ASP Racing Grooved 6 psi pulley. I couldn’t ask for more. Besides, the discharge port on the blower has an ID of approximately 2.5”.

Parts Required: (In order from the blower unit to the throttle body) One 3” to 2.5” silicone reducing sleeve, a 4” long section of 2.5” ID intercooler pipe, about 14” of 2.5” ID high strength bronze wire wrapped silicone lined high pressure flexible discharge tubing, about an 8” long section of 2.5 inch intercooler pipe, a grommet for the IAT sensor, (I used an IAT sensor grommet from a V8 air lid), a 3.5” to 2.5” silicone reducer elbow, and enough clamps to make all of the connections. I was able to find all the assorted silicone reducers, elbows and aluminum intercooler pipes on ebay in the turbo/intercooler parts section. High temp/high pressure REINFORCED silicone couplers should be used rather than the cheaper ‘non reinforced’ types of couplers.

Before I get started detailing the custom discharge tubing take a look at these pics. The first pic is easier to see what is going on. It is what I did to ‘get the thing going’ but have since modified the routing and the piping further to shorten the overall length of the discharge tubing. It is harder to see the current system, however, so that is why I am including the pic earlier system.

You can see in this picture that the throttle body intake is ‘forward’ of the blower unit discharge port by a few inches. This is why some form of flexible hose is required to make the ‘Z’ bends from the blower unit to the throttle body. You can also see all the separate components as listed above in the ‘required parts’ list, with the exception being that in this pic I had used a section of mandrel bent 90 degree 2.5” ID intercooler pipe. The 3.5” to 2.5” silicon reducing elbow is also pointed at a 45 degree angle towards the drivers side of the car in order to make the connection as all I had at the time was the 2.5” ID 90 degree intercooler elbow.

Below are some pics of the updated and ‘finished’ 2.5” discharge tubing. The 90 degree aluminum intercooler elbow has been replaced with about an 8” long section of 2.5” aluminum intercooler pipe and the main 3.5” to 2.5” silicon reducer elbow has been turned straight down. The coiled wire silicone lined flex hose has been bent into a slight ‘Z’ shape after the blower and then it turns up at 90 degrees to make the connection with the section of straight 2.5” tubing. You can still see the IAT sensor mounted in the grommet that has been placed in the section of solid 2.5” tubing. It works great. “BAAWAAAAAAA!”

(The ‘ugly orange’ silicone lined industrial flex tubing has been wrapped in black radiator hose repair tape for cosmetic reasons.)

Here are a couple more pics of the set up from different angles.

About the only component you can’t actually see in the above pics of my custom 2.5” discharge tubing is the 4” long section of 2.5” diameter aluminum tube that mates between the 3” to 2.5” reinforced silicon reducer that mounts directly to the blower units discharge port. The outside diameter of the Powerdyne BD11A blower unit discharge spool port is approximately 3”. Its inside diameter is approximately 2.5”. The silicone 3” to 2.5” reducer attaches to the blower unit discharge port. The 2.5” side of the silicone reducer mounts to the 4” section of 2.5” aluminum tubing which in turn mates with the FLEXIBLE bronze wire coiled 2.5” tubing. (I could have skipped all the above had I been able to find a 3.5” to 3” reducing elbow and just used 3” flexible tubing for the main section…but I also did not want to cut up the rksport metal tubing. Also, a 3.5” ID ELBOW is VERY BIG. It would be very difficult to say the least to mount such a monster on the straight TB and still be able to fit the stock air box not to mention clearing the radiator fans. So, to keep from buying parts that might not work I went with a 2.5” discharge system to ensure fitment.)

I wrote above that you should ‘take a look at these pics’ before I detail the custom tubing. Well, these pictures tell it all. I can’t really explain it any further. Just clean off any metal shavings, etc. from any parts you cut or modify before installing them. Make sure and tighten down all clamps. It is suggested to use ‘steel T-Bolt band clamps’ with silicon hoses. They give a more complete seal and they also do not have ‘holes’ in the steel clamp portion like normal ‘radiator hose’ style clamps which can sometimes TEAR silicone.

Regardless of what year of 4^th generation v6 f body you have you can quite easily and affordably adapt either of the RKSport Powerdyne kits to fit your car. In many instances this yields a better system when you are able to integrate the stock air box. The benefits of this being colder outside air feeding the blower intake as well as no chance of sucking up water as can happen with the ‘low slung’ cone filter.

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