Turbonetics T3/T04E Hybrid Turbo

My previous turbocharger upgrade worked well, but I soon began setting my sights a little higher.  My previous upgraded turbo is now known as the Turbonetics Stage I Turbo upgrade.  It was a T3 turbocharger with an upgraded GN compressor wheel.  According to Turbonetics, this turbo could flow enough to support around 310HP.  After doing some research, I decided that I wanted to upgrade a step further to a Turbonetics T3/T4 turbocharger.  I carefully studied the compressor maps and chose the T04E 50 trim wheel.  It seemed to be an unusual wheel in that it could actually flow more air than some of the bigger T04E compressor wheels AND it had much less tendency to surge than those bigger wheels.  In other words, the 50 trim compressor wheel seemed to defy the normal rules!  After discovering this, it became clear that I would specify a T04E 50 trim compressor section. In addition, I asked to have the 3" inlet instead of the standard 2.75" compressor inlet.  I wanted the bigger 3" inlet to match the BIG Vane Air Meter that I would be using.

I sold my other Stage I Turbo and also my Spearco 2-252 Intercooler core so that I could pay for the new turbocharger.  In effect, by giving up my intercooler, I was taking one step back in my engine development so that I could take 2 or 3 steps forward down the road.  I'm glad I did, because the results of the new turbo have been encouraging!  More on this later...

Below is a photo of the complete T3/T4 hybrid turbo assembly.  This turbo will flow enough air to support over 400HP (probably closer to 450HP).  If you look closely at the inlet of the compressor and turbine housings, you will notice that they are polished.  I pulled both housings off and carefully ported the castings.  On the compressor housing, I was very careful not to port into the area where the compressor blades sit within the inlet opening (inducer diameter).  The clearances here are carefully set, and I didn't want to mess with this.  I marked this area and stayed in front of this while doing the porting and shaping.  I shaped the inlet into a nozzle shape - turned out to be like a short velocity stack.  On the turbine housing, in addition to polishing the inlet, I also opened up the wastegate actuator port to allow some additional flow through the stock T3 wastegate setup.

Turbonetics T3/T4 Hybrid turbo with exhaust elbow attached

The T04E 50 trim compressor wheel is significantly larger than the stock T3 60 trim wheel.  Below is a photo showing the size comparison between the different compressor wheels.

T04E 50 trim compressor wheel compared to stock T3 wheel

In addition, below is a chart showing the acutal size dimensions of the compressor wheels.  The "inducer diameter" is the smaller diameter on the front of the compressor wheel.  The "major diameter" is the larger, overall diameter of the compressor wheel.

                                       Compressor Wheel    Inducer Dia. (inches)  Major Dia. (inches)

In addition to having a larger compressor wheel, the Stage III T3 turbine wheel is also larger than the stock T3 turbine wheel.  Below is a photo showing the comparison between the different turbine wheels.

Turbonetics Stage III T3 turbine wheel compared to stock T3 wheel

Below is another chart showing the size difference between the Stage III and stock T3 turbine wheels.  In this case, the "exducer diameter" is the smaller diameter that fits into the outlet hole of the turbine housing.  The "major diameter" is the larger, overall size of the turbine wheel.  As a side note... I specified the 0.63 A/R Stage III turbine housing.

                         Turbine Wheel                  Exducer Dia. (inches)      Major Dia. (inches)

The exducer diameter is supposed to be a major restriction on the stock T3 housing at higher flow rates.  That is the major benefit of the Stage III turbine section... it has a larger exducer diameter which permits more flow.  On some "upgraded" turbos, the stock T3 turbine wheel is clipped 10 degrees.  This helps by allowing more exhaust gases to escape around the turbine wheel.  It effectively increases the flow out of the stock turbine housing, but wheel clipping has limitations.  The stock exducer diameter is still the same.  The Turbonetics Stage III (there are also Stage II & V turbines) are true turbine upgrades with new wheels that have larger exducer & major diameters.

One of the challenges of the T3/T4 turbocharger installation was the wastegate actuator (WGA) mounting.  At first, I modified the WGA bracket so that it would bolt up to the larger T04E compressor bar clamp bolt pattern.  I did this so that the WGA arm had acceptable geometry in relation to the WG flap/valve attachment point.  Then I tried to see how the bigger turbo would fit.  I mounted it.. or should I say, I "tried" to mount it to the exhaust manifold.  NO WAY it would fit!  The WGA hung down too far and hit the aluminum motor mount arm.  The motor mount arm wasn't going anywhere, so I knew I needed to try and tuck the WGA up closer to the compressor housing.  This wasn't a quick process.  After a couple hours of modifying and trial fitting, I was able to get the WGA tucked up far enough to permit the turbo to mount up to the exhaust manifold.  In addition, I was able to retain acceptable geometry with the actuator rod so that the WGA operated properly.  I verified this by using a small air compressor to actuate the WG while the turbo was sitting on a table.  It's best to do this BEFORE installing and bolting everything together and later discovering that the WGA linkage does not work properly!  Below is a photo comparing my modified WGA bracket compared to a stock bracket.

WGA bracket modifications (stock on right)

In addition to modifying the WGA, there was plenty of custom working plumbing in the new turbo.  On the inlet side, I used a short section of wire reinforced silicone hose along with a 45 deg section of 3" truck radiator hose.  I put a couple short sections of thin walled 3" aluminum tubing into the radiator hose to prevent it from collapsing under vacuum conditions.  I also plumbed in my bypass valve return line and an oil breather line.  On the turbo outlet side, I used a 2-3/8th inch diameter 90 deg mandrel bend along with an industrial plumbing fitting that nicely transitioned from around 2-3/8th inch OD to 3" OD.  After this, I used 3" truck radiator hose to the TB.  Spliced into this was a piece of 3" tubing with a 1" aluminum tube that I brazed on for the feed line to the bypass valve.  Below is a photo showing the setup.  I was "clamp happy"!  I double clamped all the 3" diameter tubing connections because I didn't want connections to start popping off under high boost.  Since I didn't have ridges/barbs on the ends of the tubing, and since I have had connections pop off in the past, I decided to go with the double clamping arrangement.

Final installation of the T3/T4 hybrid turbocharger

It's hard to see, but in the 2-3/8" to 3" industrial copper fitting, I mounted a NOS Fogger nozzle.  This will be used a little bit later to give a small shot of nitrous and fuel.  In addition, not visible in this photo, I mounted a misting nozzle in the same copper fitting for my water/alcohol injection.

So far, I have been very pleased with the new turbo!  The turbo response is comparable to the Stage 1 turbocharger (with 0.63 A/R turbine housing) that I had before.  I was expecting more turbo lag, but was pleasantly surprised that it wasn't really there.  Maybe boost starts 100 RPM later or so, but the difference is negligible.  At 12psi with NO intercooler, the engine almost felt as strong as 20+psi on the old turbo (with an intercooler)!  At 18psi (with water/alcohol injection), the engine feels very strong.  I still need to do some G-Tech testing to get some actual HP estimates, but the car is now a blast to drive with the new turbo.  Should really be a blast with a small shot of nitrous (as long as I don't "blast" my stock short block all over the road)!

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