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Over the years I have posted various compressor wheel comparisons.. From Left to Right smallest to largest
Original K24 fitted in 996TT X50/GT2
K24/26 used in RUF550R and other Euro tuners, Ultimate Motorwerks Stage 2
Ultimate Motorwerks Newer Billet Stage 2 design includes slightly larger inducer, taller height and extended tip (larger diameter)
Original 991.2TTS compressor wheel Tuned while running 1.6 bar with a typical output of 650HP and 645lb ft
Last is Ultimate Motorwerks Stage 2C 50mm inducer, modern design, extended tip.
The very best turbochargers maximize compressor wheel efficiency..
There are 40 year old compressor wheels that Modern Performance turbocharger manufactures still use as base blueprints today..
Turbonetic started the Aftermarket Performance turbocharger market. Example the T66 compressor wheel had one of the most efficient compressor maps created.
The T66 wheel was actually a Garrett wheel used in a Detroit 6V92 (552 cubic inch) 2 cycle 550HP used in Fire engines.
I have used this same wheel on a 3.4 liter 930 engine producing 680HP (single turbo). Today this wheel is manufactured in Billet form with extended tip and is in many Performance turbochargers.
The 991.2TTS compressor wheel is very efficient, you can see similar design characteristics from the Stage 2C wheel
As years go on, we can "obtain" the latest in engineering and manufacturing to improve older Iron. That's the hot-rodder spirit.
All modern turbocharger that are built today rely on past proven designs/engineering. Over 30 years ago, we had 80% efficient compressor wheels.. Today we are at 80-81% Most fall in at 77 to 78%
Turbine wheel designs have also improved. I have 2 different K24 turbine wheels that I have manufactured.. One must also mention K16 turbine wheels with 9 blades and exducer almost matching the stock K24 turbine diameter
In the near future we will have "electric" variable drive/compressor (not exhaust driven) ie 992GT2RS. Amazing technology.
Isn't fast spool kind of a bad thing on stock motors with the k16 turbos?
I can understand trying to speed up the k24s spool time as they are larger and the bottom end torque created shouldn't bend rods but I cant imagine wanting to make k16s spool faster than they already do on a stock motor?
Yes the fast spool especially at low rpm can trash the stock rods. I've seen a few owners disappear from 6speedonline after this happened to them lol. Cars are probably still sitting in a barn somewhere.
Yes the fast spool especially at low rpm can trash the stock rods. I've seen a few owners disappear from 6speedonline after this happened to them lol. Cars are probably still sitting in a barn somewhere.
Yes, but can be managed with the proper tune by a knowledgwable tuner.
The Xona 1000 with the 60mm inlets are a direct bolt on no different from a K16 or K24. The only difference is adding the water cooling lines which is very simple on the difficulty scale for anyone moderately handy with basic auto maintenance.
I did believe that at the beginning of this exercise, but now, not so much.
Yes, but can be managed with the proper tune by a knowledgwable tuner.
Then you end up with a turbo that has a detuned mediocre low end / midrange combined with and weak top end. Basically a dud all around. I ran K16 hybrids years ago on a built engine which put down 720 ft.lbs at 3500. Top end fizzled out out above 6K. The restrictive turbine made for high IATs on track. I also snapped gearbox output flanges which this set up and cracked the case on a Guard LSD due to the high low end torque. If this was run on a stock engine the rods would have been pretzels in the blink of an eye.
A larger frame more progressive turbo even with 200hp extra at the wheels is a lot easier on all the gearbox and engine internals. K16s hybrids make little sense especially for a stock block engine.
Last edited by powdrhound; 08-14-2024 at 05:33 PM.
Yes the fast spool especially at low rpm can trash the stock rods. I've seen a few owners disappear from 6speedonline after this happened to them lol. Cars are probably still sitting in a barn somewhere.
Paul Harvey use to say "the Rest of the story" Sellinger engine tuning was capped because he was at elevation and running full emission in a race car application. All sensors and MAF were running with all OBD2 functions "on"
The K16 hybrid turbochargers in a 3.8 liter race engine ran to a 7200 RPM limier with a linear HP curve. Dyno sheets posted 638 Wheel HP and 7XX lb ft of torque..
The compressor wheel used in that series of hybrids developed a flat linear power curve. I governed the output of that engine to maintain full boost control and fueling within "limits" Limits that were defined by me.
Sellinger knows that I was not going to release the limits due to potential MAF limits at elevation.. IE a fully functional OBD2 running race engine. Mark can verify that conversation at the Columbia Tower.
With a 23 year old engine. The rods are failing with stock hardware (stock turbocharger) regardless of K16 and or K24. Rods have exited the engine case with stock and tuned X50 engines..
Paul Harvey use to say "the Rest of the story" Sellinger engine tuning was capped because he was at elevation and running full emission in a race car application. All sensors and MAF were running with all OBD2 functions "on"
The K16 hybrid turbochargers in a 3.8 liter race engine ran to a 7200 RPM limier with a linear HP curve. Dyno sheets posted 638 Wheel HP and 7XX lb ft of torque..
The compressor wheel used in that series of hybrids developed a flat linear power curve. I governed the output of that engine to maintain full boost control and fueling within "limits" Limits that were defined by me.
Sellinger knows that I was not going to release the limits due to potential MAF limits at elevation.. IE a fully functional OBD2 running race engine. Mark can verify that conversation at the Columbia Tower.
With a 23 year old engine. The rods are failing with stock hardware (stock turbocharger) regardless of K16 and or K24. Rods have exited the engine case with stock and tuned X50 engines..
And this is why my engine is getting rods and pistons before the 980s go on....
With a 23 year old engine. The rods are failing with stock hardware (stock turbocharger) regardless of K16 and or K24. Rods have exited the engine case with stock and tuned X50 engines..
Yes, but can be managed with the proper tune by a knowledgwable tuner.
What i don't understand is many of the popular tuners recommend 1 bar waste gates and if they are 14 lb springs..how can the n75 valve control the boost @ low rpm to modulate torque? I suppose you could pull timing but..
It just seems counter intuitive to put in stiffer wastegate springs and light weight compressor wheels that spool faster knowing these rods are soft.
I think the Motronic 7.8 ECU is pretty good and capable but how much control can these ecus provide with boost mapping compared to a standalone?
Or does it even matter and its more dependent on the boost control solenoid that is being used?
Then you end up with a turbo that has a detuned mediocre low end / midrange combined with and weak top end. Basically a dud all around. I ran K16 hybrids years ago on a built engine which put down 720 ft.lbs at 3500. Top end fizzled out out above 6K. The restrictive turbine made for high IATs on track. I also snapped gearbox output flanges which this set up and cracked the case on a Guard LSD due to the high low end torque. If this was run on a stock engine the rods would have been pretzels in the blink of an eye.
A larger frame more progressive turbo even with 200hp extra at the wheels is a lot easier on all the gearbox and engine internals. K16s hybrids make little sense especially for a stock block engine.
Sometimes I think I should just stick with the stock turbos for now and jut get a tune + exhaust and hold out for a big old set of turbos
08-14-2024, 04:53 AM
