Someone care to explain A/R housing ratios to me?

what all do you want to know? that is a broad question.

but the deffinition of A/R is area/radius. and USUALLY when people talk about A/R they are reffering to the exhaust housing although both compressor and exhaust housing have an A/R ratio.

"A" (area) is the cross sectional area of the scroll and "R"(radius) is the distance from the center of the scroll to the turbine shaft.

the smaller the area in relation to the radius means a smaller (or "tighter") A/R ratio....in the real world this means a high backpressure, fast spooling turbo!

the opposite, large A/R, typically means a slower spooling turbo with a better topend (lower back pressure).



you can think of the A/R ratio as "tuning" a particular turbine wheel.


the choice of a appropriate compressor wheel should be your first concern........the housings are cheap, you can have several around with different A/R ratios and just see which one you like.....you can have one for the street, one for the track...and one for the road course.

No.

what you are reffering to are turbonetics turbine wheels.
That is their proprietary designation of turbine wheel sizes.
Q is the largest they use on the T series as far as I know. (unless something has changed)

you can have a "N", "O", "P" or "Q" trim with any avaliable A/R you would like.

while there are a ton of compressor wheels, which they designate by the diameter of the compressor wheel measured in millimeters (i.e. a turbonetics T72 has a 72 mm wheel). You can get a T72 with one of the very few turbine wheels, the most commmonly used being the "P" and "Q" trim.

A properly matched turbo depends more on the compressor wheel more-so than the turbine wheel.

So first you choose the compressor wheel.... basically based on your desired upper HP limit.

after this you choose the turbine wheel that best suits your needs and "tune" it to fit your desired needs with an approprietly sized A/R ratio.


if you want to spool it on the street for instance and you have a T66, you could choose a "P" trim for a little faster spool and a .81 to enhance the midrange and topend.

Conversely, if all out power is your desire, and you dont mind getting the RPMs into stratospheric levels you can get a "Q" trim coupled with a .96 A/R ratio.......and well you are making a TON of power at the cost of major lag.


you get it?

the good news is that most vendors go through the trouble of finding out what works, and all you got to do is purchase it.....but knowing a little more about it helps you become an informed consumer.........and therefore a HAPPY consumer.



swapping exhaust housings is the easiest and cheapest thing to do to a turbo to alter the performance.
your best bet would be, getting the turbo you want.....with the wheels you want.... which is like tuning it to your needs.....then you can fine tune it using different exhaust housings.

badmuthrfkr said:

A guy in town, Nick, aka Turbo Prick on http://www.columbusracing.com has a T66 on his T-Type. He dynoed 386rwhp and 514rwtq.

T-Types and GNs are very similar from what I know.

Click to expand...

that has to be at very low boost.

I had a friend locally run 123 mph on pump gas with a P trim T-66. Thats at least 500rwhp on a car with a 3600lb race weight.
with some real boost he should be mid/low 10s.

386 just seems very low, That turbo should push over 400hp on pump gas


Grant:[/] Yes, alot of buick guys use them. Like I said I have a friend that uses the T66 on his stock block and is now using it on his stage motor. (he soon will be upgradeing to a innovative T72)

many of the Stage II guys use the turbonetics. T66 seem to be the hot ticket for a high power street GN, just be warned you are going to need to flow some air and have a ~3500 stall. There is someone on turbobuick.com that uses a T72 on a stock block, which is enough power to run 9s on a full weight car no Nitrous......weather or not the block can survive very long......well thats your call.



I plan on a T64 or T66 as my next turbo.