Effect Of Bigger Compressor Housing.

[Daboss]

Hey forum I just have a quick question about a turbo's compressor housing. What would be the effect of a bigger compressor housing on a turbo? For example you have a 35r you take the compressor cover off and machine it out a little bigger and put it back on that same turbo what would be the effect on spool, cfm and horsepower? A friend of mine has a 35r he wants to sell me and he says the compressor housing was machined a little bigger. I just wanted to know if it is a worthwhile investment or if that mod just made the turbo worst?

[34GeeTeeTee]

+1 interested to know...

[Lithium]

This is an area which I am curious about too and am not sure what to make of. Garrett don't seem to release different compressor maps for their different housing sizes for the same wheels - but in saying that I have definitely seen cases where people have made more power upgrading to different housings.

I know for sure that people have got power improvements with EVO 16Gs going up to a larger compressor housing size, the same applies to people with XR6 Turbos (going from the stock .50a/r unit to the .70a/r housing seen with aftermarket GT3582Rs) - but at the same time a guy I know did an experiment with a maxed out Garrett "T04Z". The turbo was totally maxed out on race fuel, 770hp @ hubs from memory. He got the compressor housing extrude honed and put it back on the dyno for another go, attempted a full retune to suit and no difference anywhere - it was like nothing at all had changed. They couldn't push the boost any higher, nothing.

At this stage I am playing with the idea that its a case of getting the smallest scroll (will call it tube) possible to flow the amount of air you need, a smaller tube may allow pressure to build a bit quicker but then there will be a point it may become a bottle neck. If your tube is big enough then going up a size may make no difference at all, but if the compressor flow is being restricted by it then I'm guessing an upgrade would be beneficial. Maybe someone like Stao @ Hypergear will have some insight, as he's probably used similar cores in different housing combinations.

[Daboss]

Not really talking about extrude honing but more machining the area where the compressor blade fits and making that bigger. Would it increase lag and cfm or do absolutely nothing?

[34GeeTeeTee]

Not really talking about extrude honing but more machining the area where the compressor blade fits and making that bigger. Would it increase lag and cfm or do absolutely nothing?

Yep, we are talking about the same sort of thing.... You would imagine some increased lag as there is more area to fill but possibly more flow up high? I'm not sure...

[Frosty]

▲ this is kinda on the money but its not just as simple as that. I think we should let Stao answer this properly

[hypergear]

Differences in power is almost no difference, unless a huge variance between sizes such as difference between a tinny VL .46 comp Vs a .70 comp used on a 82mm wheel. Other wise just like I managed to pull 349rwkws out of a stock nissan housing. How ever the cutting profile inside the housing makes a huge difference. that can affect response as well as discharging temp.

I personally prefer to work on large compressor housings as it has extra materials that I can work with, looks and sounds better.

Exhaust housing do make a huge difference.

[GTScotT]

How ever the cutting profile inside the housing makes a huge difference. that can affect response as well as discharging temp.

I'm guessing giving the compressor more clearance to the housing after the inducer area will increase lag but also raise power to boost threshold, with drops in charge temp due to fact there is less compression (in turn less friction on air particles) per unit of outright flow?

Possibly a reasonable option for high output setup's where lag isn't an issue and a drop in charge temps AND boost to power threshold would mean more accessible area of the available flow. IF my theory is correct, anyhow.

[Daboss]

Hmmmmm. So the general consensus is that it will increase lag a bit, but with the potential to raise horsepower and lower discharge temps? Also another quick question can your exhaust pipe/muffler affect your turbo spool? A friend of mine had his exhaust system replaced from the turbo to the catback and now car has picked up lag?

The first exhaust system he had was from the turbo all the way to the middle of the cat, one straight piece of pipe and the turbo spooled by 4400-4800 rpms, he now has a front pipe, dump pipe and decat pipe installed and that is the only change he made to the system and now he turbo spools by 5200-5600.

That is about 1000rpm's worth of lag picked up and we can not figure why. System has been checked for boost leaks, there are none and also no exhaust leaks pre-turbo.. Like I said only thing changed was the exhaust system from the turbo to the cat back. So could that have caused the lag he now experiences?

[hypergear]

Going for a larger exhaust can increase torque and power. it shouldn't have much affects in terms of turbo's response.