Max Q's Big Turbocharger
Last updated 2007-09-18 11:08 PDT

Turbonetics T04 Hybrid Turbocharger

Max Q's original KKK K26#6 turbocharger was replace by Graydon with a K27/K26#6 hybrid. After seizing the KKK, I purchased a hybrid turbocharger from Turbonetics. It has a Garrett T04E-50 cold side, a T04B center housing and a custom exhaust scroll with KKK dimensions and bolt patterns. The center housing has the Turbonetics ceramic ball bearings installed.

The dimensions are surprisingly similar between the KKK hybrid and the Turbonetics, with the new one having a significantly narrow exducer on the cold side and an very much larger exducer diameter on the hot side. My rough A/R measurements are approximately the same for both turbochargers.

Cold Side Dimensions K27 T04E-50
Impeller diameter 3.985 3.995
Inducer diameter 2.070 2.120
Exducer width 0.286 0.200
Blade count 12 12

All dimensions are in English, since I couldn't find my metric calipers at the time I wanted to measure these things. (Besides, all Turbonetics dimensions are given in English, too.)

Hot Side Dimensions K26#6? K26#8/T04B
Blade count 12 11
Exducer diameter 1.960 2.270
Nozzle diameter 1.46 1.50 crude measurement
-> A (sq. in.) 1.67 1.77   "
R 2.35 2.35   "
A/R 0.71 0.75   "

Other physical differences include the ceramic ball bearing on the new one and the cooling line connections. The T04B center housing has the cooling lines running through from side to side, rather than from top to bottom as in the KKK center housing. (I wonder how this is supposed to induce a thermal siphon?)

The cold side scroll is about 1" smaller in its outermost diameter on the T04, but the nozzles are the same size. This smaller housing is bad because the retaining bolts that hold the housing to the back plate protrude through into the air stream. I don't like this at all, and will grind the housing a bit to smooth the flow.

The T04E scroll also has a 1/8" pipe hole threaded into a boss on the outlet, all ready for the pressure tap to a boost controller.

Here you can clearly see the difference in the oil and water connections. The T04B body has the water connections on the side, plugged with the big red plugs, whereas the KKK has a hole above and to the right of the oil inlet.

The big difference that is apparent from the outside is the much larger exducer diameter on the Turbonetics exhaust housing on the right.

The nozzle inlets were identical in dimension, but that soon changed.

Since the new exhaust manifold had a much larger outlet, I port-matched the inlet on the exhaust scroll to match. This opened up the inlet about 1/8" more, and took off the casting roughness and ripples.

Here you can see the huge difference in the outlets on the two manifolds. I don't think Jeff took much metal off the two-piece to get it to this size, since there is still some raw-cast surface fairly near the outlets on the runner up to cylinder 1. Remember, too, that Graydon had already ported the old manifold and had done a really excellent job of smoothing it out and port matching it to the head.

Very rough measurements show that the 2-5 outlet (at the top) is about 25-35% bigger on the two-piece!

The body of the two-piece also shows some significant increases in size, some of which are apparent in this photo. Look at the bolt holes for cylinder 5, and notice the big bulge on the two-piece, which obscures the top hole. This translates to a fairly sizable restriction in the old one-piece, which looks much smoother in the new one.

I knew you were curious, so I included a picture of the connector accordion pieces for the exhaust manifold. There are two clamps and two little stub pipes in the complete assembly. All the bits appear to be made of stainless, so they should last a while.

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