At work recently I overhauled a 6.5 GMC Turbo Diesel. The wastegate shaft was siezed solid in the turbine housing, and I needed to send it out for repairs, since I didn't want to blow up my fresh rebuild (an engine overhaul in these trucks flat rates at 32.8hours, it took me over 40hrs- you don't want to do it twice!). Anyway, I'm so glad this happened, as our local diesel expert recommended a turbo shop, about 45minutes away from my work, called Blouch Turbo in Lebanon, PA. These guys are amazing! Bob really knows his stuff, and they have turbos laying everywhere! Very neat, clean facility too. He showed me some of the big turbos the drag racers use- I was so excited I could hardly leave the place!

ANYHOW,
The reason for this post is that they are setup to machine the compressor and exhaust housings to fit in larger wheels. He showed me a stock WRX turbo that they machined to fit a TO4e 57 trim compressor wheel and a big turbine wheel (dont remember those specs). The inlet pipe on the compressor was machined very thin (.060") to allow clearance for the larger wheel! It looked amazing to see a wheel that size in such a small housing!

Anyone else heard of doing this? How is the performance compared to swapping the entire turbo (with larger wheels and housings)? I seen BBSD recommended doing this if you needed to upgrade his turbos on his latest TT set-up, as there is not room for the larger housings in that system. Just wanted to let you all know that this process is out there. Of course, maybe you all knew that already.

 

Mhmm.. popular modification for the Toyota CT-26 I'm running is a T60 compressor wheel. Housing gets majorly overhauled in the process.

 

It's definately the way to go if you can't fit bigger housings or just want to keep the turbo's you have. Obviously bigger wheels can flow more air, but so do bigger housings. On the turbine side bigger housings 'generally' mean higher top end flow at the cost of extra lag because the pressure differential between the header and downpipe is less. From what I understand, the compressor housing doesn't affect this quite as bad, although it still makes a difference.
At any rate, if you're stuck with smallish housings like in the BBSDesigns street/strip TT kit, bigger wheels are definately a worthwhile investment IMO.

 

opening up housings to fit bigger wheels has been around for years. Used to do that to cheat at the races!

 

Like everyone else has said, it’s been around for years and works. Not as efficient as running the correct housing since you never end up with a sufficient diffuser size and the inlets and outlets are small, but it’s better then nothing. Some interesting surgery could be done to some housings to compensate for some of this, but basically what works depends on how much spare aluminum you’ve got to work with.

 

89JY,
Perhaps you have, before and after, compressor maps,
of that mod?
I would be especially interested if that mod resulted in
-->more flow<-- (cuz most turbos have more than
enough pressure boost in their efficient zone)
.
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