If your only getting one side of the VTG modded, which would yeild better results? I see some upgraded VTG only modify the exducer, and others modify only the inducer. So, which is better and why?

 

Our modified VTG's use custom profile billet wheels, both the inducer and exducer are modified. Contact me for pricing.

 

you should get the one's that has the both sides modified.. otherwise(unmodified exhaust side) more air comes from the front means more choking up on the exhaust side and dramatically raised EGT's. And that means a lot of power lose..

 

some rebuild the complete turbo others only change the compressor wheel... better? that is a subjective question... I think too many other factors play a roll.
What if I can run 134 mph in a 1/4 mile on stock turbos... does that mean stock turbos are better then the Hybrids? Or are the Hybrids not as good as they say?
Better yet, why aren't the Hybrids running better?
My point is that other factors like ICs, plenums, exhaust, Tuning, etc also play a big roll... thus the result is a culmination of parts rather then just a mere turbo upgrade with a flash. Also, Prices dramatically differ between the two... you need to ask yourself how much your willing to pay for "better". Because if that is not a concern then I have a direct replacement turbo that produces 700rwhp...

 

Mandatory reading:

http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech102.html

 

I don't understand what you mean by "side." The only "sides" are the compressor (air inlet) and turbine (exhaust outlet.) Each side has a wheel.

There is a inducer/exducer for the compressor wheel and inducer/exducer for the turbine wheel. The inducer is defined as the diameter where the air enters the wheel...compressor or turbine side. The exducer diameter is defined as the diameter where the air exits the wheel...compressor or turbine side. You'll note that the inducer is smaller in diameter on the compressor, and larger on the turbine.

 

A tuner that modifies the inducer/exducer is changing the trim ratio, defined as (inducer^2)/(exducer^2.) The trim of a wheel (compressor or turbine) will shift the airflow capacity. In very general terms, a higher trim wheel will flow more than a smaller trim wheel.

 

You understood correct. That's what I meant by "side"

If the compressor wheel has been modified and the turbine wheel not, that means more air will enter from the compressor side and also more air will try to go out from the same size turbine side. So, there will be more ''choking'' and heat.

 

Okay...I see what you are saying.

 

On another note, several tuners have billet wheels that have significantly larger inducer/exducer diameters compared to the GT2, producing massive power. However, the A/R (area/radius) ratio is still limited on the turbine housing side. This is still the rate limiting step to big power on the VTGs.

Turbine housing 997TT v GT2




The A/R on the turbine housing has a greater impact on velocity and flow of exhaust gases (ie a smaller A/R will increase the exhaust gas velocity into the turbine wheel, resulting in a quicker boost rise but with a reduced flow capacity...conversely, bigger A/R = more flow at the expense of more lag and larger boost threshold.)

I do not believe GT2 turbine housing and wheels are available separately. If they were, you could assemble (for a significantly lower cost) a larger turbine housing - hence improved A/R ratio on the turbine side - and produce a turbocharger that had significantly greater flow capacity...which is why the GT2 turbos are still very desirable for big power...but it comes at a financial price as well as greater lag.

So to the OP...it's not a simple matter comparing inducer/exducers. Most tuners here are changing the compressor wheel (altering the inducer and exducer sizes) and clipping the turbine wheel to improve outflow to the exhaust. By keeping the turbine housing smaller (ie 997TT size) you improve boost response but limit maximum flow. If you modify a GT2 turbo (which has a larger turbine housing) you potentially get improved flow and power, but may sacrifice boost response.

 

thanks for the link

 

I did that too.. The main difference I have experienced between modded GT2 turbos vs 997tt turbos is the throttle response. the gt2 turbos kick in around 1 second later. But it made better power up top, no doubt. Also no sacrificed power down low.

 

okay, the way that it was explained to me, there are people that are only modifying the HOT side (which i erroneously referred to as exducer) and there are others that modify only the COLD side (which i erroneously referred to as the inducer). (by HOT side, i mean the part of the turbo that touches the exhaust gasses, by COLD side, i mean the side that forces in the fresh air)

so, to put my question in a different way, if you had to choose between modification of either side (not both) which would produce better results. This question does not ask for any other variable, such as intercoolers or anything else that may be pontificated about. It only asks about which one would result in faster spool and/or more air flow.

 

Most modified VTG Turbo Vendors swap out the compressor wheel and machine the the housing to accommodate the bigger compressor wheel.
This increases the VTG Turbos HP potential on 997.1TT from around 550 hp to 680/700hp mark.


On the hot side some vendors clip the turbine wheel to decrease resistance and back pressure at high exhaust flow rates, this extends the A/R
more flow at the expense of more lag and larger boost threshold.

I did not go with the clipped turbine wheel as this would decrease my bottom end due to less surface area exposed to exhaust gases at low to mid rpm range.

 

Nice thread & excellent info.

Bob/Venka., what exactly does "clipping the turbine wheel" involve? Literally cut or machine the wheel to make it smaller?