TURBO, WASTEGATE, AND ANCILLARIES

ABOVE: Stock K26 fitted with an Audi compressor housing, bored & polished with a larger compressor wheel.

Earlier photos:

This configuration is hitting 11psi at ~3200rpm. I start hitting positive boost pressure at 2200rpm.

The plumbing runs as follows:

Fresh air into turbo:
- 6" long tapered, 2.25" opening, S & B air filter
- 2.25" to 2" reducing silicone hose
- Turbo: 2" inlet

Compressed air out of turbo / into intercooler:
- Turbo: 2" outlet
- 2" 45 degree silicone hose on turbo out
- 8" length of 2" aluminum straight pipe
- 2" to 2.25" 90 degree silicone hose into intercooler
- Intercooler: 2.375" inlet

Cooled air out of intercooler / into throttle body:
- Intercooler: 2.375" outlet
- 2.375" silicone hose with 1" BOV tee
- 2.25" flared end pipe, 5" length
- 2.25" to 3" 90 degree silicone hose
- 3" throttle body inlet

Sounds complicated, but's really very elegant plumbing. The pipe diameters are on the small side, but they're big enough to avoid being a restriction and small enough to keep the volume down that the turbo has to fill. Everything looks like it's supposed to be there - the ultimate goal!

Here's the Forge Motorsports Blow Off Valve that sits between the intercooler and intake manifold:

The wastegate is a 930 (911 Turbo) part. The rubber diaphragm had a few cuts in it when I first opened it up. Andial carries replacement diaphragms. As you can see in the pic the support bracket is cracked. This seems to be a common failure and likely led to the broken J-pipe I found while pulling apart the exhaust. I found a replacement J-pipe through (gasp) AutoAtlanta. The bracket was replaced with a used piece from a parted 931.

The addition of the intercooler proved a little tricky. I finally decided on placing it between the engine and nose. The 931 nose panel vents will work great to force cool air through it. A sheet metal shroud will provide the duct-work.

The big trick is that the IC inlet is at a terrible angle. So... off to the friendly cast aluminum weld shop. Cut the old inlet off, and relocate it.

The intake manifold is the other big trick. The stock throttle body faces the completely opposite direction that I need it to. My solution is to cut the plenum off the runners and weld a new one in its place. The new throttle body will be facing the driver's side fender. This will only require a 90* turn to plumb from the intercooler. A vast improvement over all the turns and bends the stock intake charge is required to make.

The new plenum will be tapped for the pressure line going to the MAP sensor (inside the MS controller), a vacuum line going to the brake booster, a vacuum line going to the blow off valve (BOV), and for the intake air temperature (IAT) sensor.

The turbo gets fed from a cone filter located next to the oil cooler. The vents in the front valence will provide cool fresh air to the intake. Some more shrouding work ensures that air from the vent will be split partially to the intake and partially to the oil cooler. As it is, the oil cooler just picks up whatever air happens to be pushed through it.

The throttle body itself is a 60mm unit from an '86-93 5.0L Mustang. It comes with a throttle position switch (TPS) that will easily interface with the MegaSquirt EFI. In addition, I'll use the fast idle circuit that mounts to the side of the TB. This is also controlled by the MS and helps to keep the idle up when the engine is cool.

For the hot side of the turbo I managed to find a perfect non-cracked exhaust manifold - which is a rarity. I cleaned the manifold up and sprayed it with a super-hi-temp silver paint then cured it according to the directions using my gas grill (worked great!). I like to paint engine bay items lighter colors so I can easily see any leaks or problems. While I had some down-time I polished as much of the inside of the manifold that I could reach with a flexi-dremmel attachment. It smoothed out the runners quite a bit.

I also had the exhaust manifold drilled for the EGT probe.

The stock wastegate spring is set to 0.43 bar (6 psi) for the US market. I'll be matching the 0.65 bar (9.5 psi) boost pressures the RoW models used by adding a simple boost controller. I opted for Boostscience's Reliaboost II. It's just a simple Grainger valve that cuts the signal to the wastegate until the preset boost level is reached. This should keep the wastegate from creeping open until max boost is reached.

*Note about ReliaboostII fitment. The stock wastegate line is a 3/8" inner diameter and the Reliaboost uses 1/4" fittings. You need two 3/8" to 1/4" male-male barbs to plumb in this controller.

Old Results (3/04)
The turbo whine is music to my ears! I get a full 11psi at about 3100 RPM (stock is 6psi @ 3500 RPM). The exhaust has a great sounding rumble at idle that quites down at speed. The boost controller really seems to be doing its job!

(pics of JE build turbo)
The original K26/6 turbo was rebuilt by a small shop in Southeast MA (508-234-9615). I sourced the rebuild kit from PartWerks of Chicago (sometimes pricey, but they find obscure parts) for a bit over $100. The rebuild came in at $350 which included welding a small crack in the cast iron hot side. This turbo has a larger compressor wheel than that in the '81-'82 models and builds more boost than the later models. The drawback is that the boost comes on a bit later.

Here is a shot of the welded manifold I was using. This weld actually cracked too (likely from the extreme heat from detonation). Be sure to look check for cracks if/when you pull your manifold off!

These old KKK's have historically short lifespans. Much of this is due to the fact that this technology was relatively new back in 1980 and proper cool-down procedures and oil change schedules weren't met. Plus these turbos were oil-cooled only, which certainly doesn't help their longevity even though a proper oil cooler is fitted to them by the factory. With proper maintenance and healthy Mobil 1 oil changes I'm looking forward to getting some good mileage out of this one.