Articles -- Turbo Inlet Duct mods

material's needed == cost:
1 - 3" 90 or 45 deg mandrel bent exhaust piping, preferably polished. looks 'BADASS' == $YMMV, mine was free
1 - 3" ID silicone connector == $6
1 - 3"-to-2.5" silicone reducer (BLUE OF COURSE!) == $6
1 - 2" long section of reinforced (Purosil) 2 1/4" silicone hose == $YMMV, free here.
xx - various screw clamps, 2 or 3 is good enuf, old $say 5 total ones are completely reuseable

1.   you are using an cone intake.
2.   you have aftermarket BOV (Greddy Type S here)/non-stock open vented BOV.
3.   you like blue silicone hoses. HOSES i said.
    -you do NOT need to remove air pump/shroud/fan for this operation
    -there's a 2" black hose thingie that you may have to trim/relocate

1. take electric jig saw, cut pipe to fit
     a. if you have a 90deg bend, cut the pipe in half.
     b. if you have 45 deg bend, cut the arms shorter.
     c. if you have NO piping, email me, i have some left for trade w/ $
2. take out AFM + T.I.D.
3. fit section of 2 1/4" silicone hose over turbo inlet
4. fit 2.5" end of 3"-2.5" silicone reducer over turbo inlet opening
5. insert 3" metal piping into 3" end of silicone reducer
6. if you can't figure it out from here, you're more mechanically uninclined than I...
7. tighten things down
8. clean hands
9. drink beer
10. etc.

This weekend, in addition to FINALLY getting around to cleaning the car (it was NASTY) and
putting a clutch in an '88 GXL, I did the turbo inlet duct mod.

You'll need:

- a 3" 45 degree bend piece of PVC (I got some in black - looks good)
- a 3" coupler (basically a rubber piece of hose with 2 hose clamps)
- a 3" to 2" reducer
- a 2" 90 degree bend
- a 2" coupler w/2 hose clamps
- a 3/4 inch barb fitting
- a 1/4 inch barb fitting

OK, here's how it all goes together. The mass air flow meter's outlet is 3" ID (internal diameter) and the turbo side of the duct is about 2.5" ID. There are 2 things that plumb into the duct - the compressor bypass valve and the PCV breather tube.

The 45 degree bend is the main part of the assembly. I plumbed the CBV and PCV tubes into that part of it. For the CBV tube. I found a 3/4 inch barb fitting that had a threaded female end on it. I also got a brass male threaded fitting that is about 1/2 inch long with a nut end on one side. This screws into the barbed fitting nicely. I cut a hole that the male end could fit through in the 45 degree bend, stuck the male end through, then tightened the barb onto it. Exact same principle for the PCV breather, just smaller fittings. I got a 1/8th inch barb and used standard 1/8th inch (3mm) vacuum tube - it will work, but it's a VERY tight fit. 1/4 inch fits a lot better. Coming off the metal pipe that the breather is connected to, I attached some vacuum hose, ran it to the one-way check valve, then ran another short piece of vacuum hose to the barb fitting. For the CBV, I used the tubing I removed for the air relief silencer for the air control valve - it's the perfect size, and I gots tons of it :). Basically, it's tubing from the turbo outlet pipe to the CBV, then tubing from that to the barb.

OK, so you got all this plumbed into the 45 degree bend. The bend I got had one end with a male end, one with a female. I attached the airflow meter with the coupler to the male end of the bend. On the female end, I attached the reducer. Make sure to totally shove the PVC piping together. Then, I shoved the male end (aww yeah...:) of the 2" 90 degree bend into the reducer. I used a hacksaw to cut the female end off, and reduce the radius of the bend slightly. I put all the components together loosely, and turned and twisted each section until I found a position where they all fit into the right place and put the intake in the right spot. Used the smaller rubber coupler to attach the duct
to the turbo. Ta-da! Done.

Went for a test drive - HOLY CRAP. *Easy* 15 extra horsepower. I had to turn the boost controller down - I was generating *2* extra pounds of boost! 1 extra pound with the boost controller off!

Right now, I have a small vacuum leak somewhere. I think it might be around the barbed fittings - tomorrow I'm going to get some neoprene washers to put in there to get a better seal.

BTW, this is only possible with a cone intake. This will NOT work with the stock airbox - the cone is now at an angle at the front of the car. It will not line up to the stock airbox.

Total cost? About $20 or so in parts, and about 1 hour of goofing around with it. After I had the duct all done, I saw the stock duct sitting over to the side - man, that thing is WIMPY in comparison!

In the future, I'd like to find some silicon rubber to replace the coupler on the turbo side. This would make this a lot more durable.

Be prepared to spend some time in the hardware store - it took me a while to find the exact pieces I wanted.

Problem 1 - the highway I normally do the runs at is now a "construction zone", and speeding fines are DOUBLED in Florida for a construction zone! No sense speedin' around there!

Problem 2 - running a bit lean with the vacuum leak. I don't feel like a blown motor, thanks :).

BTW, my best 40-70 average right now is 4.5. Not too shabby with a stock catback :).

Try it!

Dale

| Dale Clark - 2nd Gen Bad-Ass
| '88 10th Anniversary (awww yeah!)
| RX-7 Club of Florida, Pensacola, Florida
| Mazda RX-7: The Ultimate Page! http://rx7.freeservers.com

Last Updated: April. 22, 1999, by: Mike McLeish

RX7 Articles -Turbo Inlet Duct

RX7 Articles -Turbo Inlet Duct