BigJls1

mike and myself are much like a ford vs chevy or turbo vs blower
and I connot disagree with mike cause it is true what he says
so mike how bout this just for kicks :

which makes more power
The right wheel in the wrong housing or....
the wrong wheel in the right housing

my vote goes to the right housing because the housing is flow match to the engine, I personaly have never seen a wheel get flow matched to an engine where as turbo cal. can flow match a housin to your motor.

6techniques

iTrader: (7)

I know this was pointed towards Mike but Ill put my little bit of change in anyway ...

I think thats a double sided question, and there are way too many variables to properly say which would be better.
On the right housing, yes the housing can be flow matched to the engine but lets say youre running a 57mm wheel with a 1.32 a/r on a 408cid engine with the RIGHT housing? But lets say you have a 88mm wheel in an engine with the same cubes but the housing is at .76 a/r...
Id have to go with the bigger wheel in a crappy housing and just limit myself in rpm's... BUT thats only in a street car where Ill be the master of stop light to stop light action!

engineermike

I compared the PT67GTQ .96 to the PT76GTQ .96. These turbo's have the exact same exhaust wheel and exhaust housing. 175 hp difference due solely to the compressor size.

Mike

gametech

iTrader: (1)

I love how this thread tries to distill complex multi variable fluid flow dynamics calculus into "see spot run".

SS4Matt

iTrader: (4)

otherwhitemeat

iTrader: (3)

huh ok?............so basically,....go back to the second post

sampson

iTrader: (1)

You are comparing two different compressors. You would have to keep a consisant compressor.

BigJls1

we need a mule to juST TRY A bunch of combos and quit bench racing . It is fun to
though.

obZidian

iTrader: (2)

i believe the point mike is trying to make that, since it is insinuated (spelling!) that the a/r of a given turbine has a larger role in turbo performance ona given platform, mike, on the other hand, has pointed out that there are other factors in turbo selection thta will yeild larger forms of power.

...and i agree. Though the a/r of your turbo selection is crucial to HOW a turbo will produce its power, the wheels/trims configurations will dictate HOW MUCH a turbo can yield. NOW, lower the a/r on a gt76 and you will have a faster spooling, less overall power turbo package on a particular engine package. HOWEVER, we all know that by going to a larger a/r, you change the way the turbo produces its or flow characteristics, thus exhibiting a change in its power productivity... aka, slower boost response, more overall power on the same engine.

That is why racers that want to net more power, they go to a larger turbo in itself. If all we needed is to just keep making the a/r turbine housing larger, than there would be a need for an evo, for example, to run a gt42R to make 900awhp on c16, instead, he would just needed to go to a larger a/r on a gt28R.

engineermike

No kidding. That was the whole point of my comparison. Early in the thread, it was said by BigJls1 that the turbine A/R was the most important aspect of turbo selection, even more important than the compressor size. My example was an attempt to show otherwise.

Mike

sampson

iTrader: (1)

Sorry, I read that wrong. You are right, a/r is not as important as a compressor.

BigJls1

the a/r on the compressor is not a critical as the wheels trim: true

the a/r of the turbine housing is more critcal than the wheel trim: true

Mike I agree with you but the original question was about turbine housing a/r we are debating apples and oranges. the exhaust housing a/r is more critical to your hp threshold than the exhaust wheel. IMHO

BigJls1

obzidian

well said

engineermike

Okay, I'll shift gears and drop the compressor bit.

However, once again, I dissagree with you. Lets look at some more turbocharger spec's. . .

PT-76GTQ, .96 AR: max hp = 975
PT-76GTS, .96 AR: max hp = 1100

The "Q" and the "S" designates the size of the exhaust wheel. See how the exhaust wheel size can change the hp rating of the turbo by 125 hp? Adjusting the AR will not have that large of an affect.

Now, lets look at two other turbo's. . .

PT-88, .96 AR: max hp = 1250
PT-91.5 G-trim, .92 AR: max hp = 1550

In these two, the compressor size is very similar and the AR is very similar. The big difference is the size of the exhaust wheel. The 91's exhaust wheel is a full 1.27" larger than the 88's wheel and so it's capable of 300 hp more with a smaller AR. Get my drift?

Most turbo people will choose the compressor size and turbine wheel size based on the hp goals, then adjust the AR to tweak the powerband and spool up characteristics. Again, playing with the AR will not dramatically affect the power output of a combination unless the combination is way outta' whack. For instance, if you put a PT61 with a .58 AR on a 383, then switching to a .96 will probably pick you up 50 or 100 hp. But, install a T88 on it, and it'll pick up a few hundred.

Mike

BigJls1

Damit mike, I'm almost convinced. One thing that I have to belive is that if you can add 200 hp with a wheel change you have to be giving up some down low. It has to take more flow to get a bigger wheel offset or more agressive wheel to spin, Once the wheel is spinnig boost must ramp up at an out of site rate.
If a person is looking to purchase a used or rebuild turbo should they buy it based on the size of the wheel or the sze of the housing. Housing sizing will be much easiers to get closer to your combo as you can easly to math to figure you motors flow and your hp goals. maybe not your boost levels as the wheel can really change the the housings boost output.