Downside to upgraded VTGs?
Former Vendor
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There is some controversy about the advantages of billet versus cast turbocharger upgrades. Billet compressor wheel technology is NOT new. It’s been around since the 80s. The material does not necessarily make a billet wheel produce more power, rather it is the ability to use CAD/CAM to design a billet wheel.
From a technical perspective, a billet compressor wheel is CNC’ed out of a solid piece of billet aluminum where as a traditional wheel is cast out of molten aluminum. The theory is a CNC'ed billet compressor wheel can be created with “less bulk” and less actual material, and CAD designs can take advantage of the new found “space” within the turbocharger inlet by redesigning the compressor aerodynamics to produce greater CFM with the same size inducer.
If the design of the compressor wheel is the same (billet versus cast) there should be no significant performance difference (aside from actual weight of the wheel and the physics of weight reduction.)
As far as strength of the material is concerned, here is a quote from Garrett:
"in OE applications, fully-machined wheels can withstand higher centrifugal stresses due to differences in the base material. Forgings are inherently stronger than the typical casting in this respect. However, when Honeywell engineers choose a fully-machined wheel over a cast wheel, they are only doing so to prolong the wheel's life in extreme duty-cycle OE applications where the turbo speed is constantly cycled. A typical example is a city bus, in which the turbo is frequently subjected to rapid transitions between high-load (full throttle) and low-load (idle). Compressor wheels can fail in low-cycle fatigue (LCF) in these applications, which is where fully-machined wheels offer an advantage in strength and lifetime. However, the typical aftermarket turbocharger will not be subjected to such extreme cycling."
From a technical perspective, a billet compressor wheel is CNC’ed out of a solid piece of billet aluminum where as a traditional wheel is cast out of molten aluminum. The theory is a CNC'ed billet compressor wheel can be created with “less bulk” and less actual material, and CAD designs can take advantage of the new found “space” within the turbocharger inlet by redesigning the compressor aerodynamics to produce greater CFM with the same size inducer.
If the design of the compressor wheel is the same (billet versus cast) there should be no significant performance difference (aside from actual weight of the wheel and the physics of weight reduction.)
As far as strength of the material is concerned, here is a quote from Garrett:
"in OE applications, fully-machined wheels can withstand higher centrifugal stresses due to differences in the base material. Forgings are inherently stronger than the typical casting in this respect. However, when Honeywell engineers choose a fully-machined wheel over a cast wheel, they are only doing so to prolong the wheel's life in extreme duty-cycle OE applications where the turbo speed is constantly cycled. A typical example is a city bus, in which the turbo is frequently subjected to rapid transitions between high-load (full throttle) and low-load (idle). Compressor wheels can fail in low-cycle fatigue (LCF) in these applications, which is where fully-machined wheels offer an advantage in strength and lifetime. However, the typical aftermarket turbocharger will not be subjected to such extreme cycling."
The billet wheel when set up properly with different Aeros picks up big HP.. By having less weight the center of wheel can be downsized which will allow for more surface area of the blades.. If you measure a 59mm surface area in Billet vs. a 61mm in Cast the 59mm has larger blade surface.. Along with the new Aero Technology thats where the power is made..
I can give an example of a turbo made by the same company and tested on our car in cast vs. billet.. The billet 67mm turbo made 740hp at 44psi and the billet made 920 @ 44psi.. 180whp was unbelievable to us.. Not only does it make more power it holds it too.. The 67cast would drop to 35psi by redline while the billet would hold 44psi to 9500..
Pics Below...
Mike
Last edited by AWD Motorsports; May 18, 2010 at 11:26 PM.
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There is some controversy about the advantages of billet versus cast turbocharger upgrades. Billet compressor wheel technology is NOT new. It’s been around since the 80s. The material does not necessarily make a billet wheel produce more power, rather it is the ability to use CAD/CAM to design a billet wheel.
From a technical perspective, a billet compressor wheel is CNC’ed out of a solid piece of billet aluminum where as a traditional wheel is cast out of molten aluminum. The theory is a CNC'ed billet compressor wheel can be created with “less bulk” and less actual material, and CAD designs can take advantage of the new found “space” within the turbocharger inlet by redesigning the compressor aerodynamics to produce greater CFM with the same size inducer.
You are dead-on...If the design of the compressor wheel is the same (billet versus cast) there should be no significant performance difference (aside from actual weight of the wheel and the physics of weight reduction.)
As far as strength of the material is concerned, here is a quote from Garrett:
"in OE applications, fully-machined wheels can withstand higher centrifugal stresses due to differences in the base material. Forgings are inherently stronger than the typical casting in this respect. However, when Honeywell engineers choose a fully-machined wheel over a cast wheel, they are only doing so to prolong the wheel's life in extreme duty-cycle OE applications where the turbo speed is constantly cycled. A typical example is a city bus, in which the turbo is frequently subjected to rapid transitions between high-load (full throttle) and low-load (idle). Compressor wheels can fail in low-cycle fatigue (LCF) in these applications, which is where fully-machined wheels offer an advantage in strength and lifetime. However, the typical aftermarket turbocharger will not be subjected to such extreme cycling."
From a technical perspective, a billet compressor wheel is CNC’ed out of a solid piece of billet aluminum where as a traditional wheel is cast out of molten aluminum. The theory is a CNC'ed billet compressor wheel can be created with “less bulk” and less actual material, and CAD designs can take advantage of the new found “space” within the turbocharger inlet by redesigning the compressor aerodynamics to produce greater CFM with the same size inducer.
You are dead-on...If the design of the compressor wheel is the same (billet versus cast) there should be no significant performance difference (aside from actual weight of the wheel and the physics of weight reduction.)
As far as strength of the material is concerned, here is a quote from Garrett:
"in OE applications, fully-machined wheels can withstand higher centrifugal stresses due to differences in the base material. Forgings are inherently stronger than the typical casting in this respect. However, when Honeywell engineers choose a fully-machined wheel over a cast wheel, they are only doing so to prolong the wheel's life in extreme duty-cycle OE applications where the turbo speed is constantly cycled. A typical example is a city bus, in which the turbo is frequently subjected to rapid transitions between high-load (full throttle) and low-load (idle). Compressor wheels can fail in low-cycle fatigue (LCF) in these applications, which is where fully-machined wheels offer an advantage in strength and lifetime. However, the typical aftermarket turbocharger will not be subjected to such extreme cycling."
Former Vendor
Joined: Mar 2010
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From: Pompano Beach, FL
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First let me say that I think there has been some confusion in the loose usage of the words “BILLET TURBO” recently. Champion Motorsport has been doing 63.5mm and 65mm billet compressor wheel upgrades on VTG turbochargers for several years now, as have other tuners. Now recently for 2010 we have introduced both our 68mm compressor for 2010 cars, and our line of “BILLET COMPRESSOR HOUSINGS”. These billet housings used in conjunction with our billet compressor wheels have yielded some impressive results for our own press cars, as well as our customers cars. If you are buying a “BILLET TURBO” ask what exactly you are getting as there are variables.
In regard to just the compressor wheel, IE: Billet vs Cast, these statements that I quoted below are 100% correct as I read them. Once you switch to Billet and CAD design, the window of performance opens wide up. Yes, there are aerodynamic gains possible, as well as the addition of blades, IE: our 7 blade wheels vs the cast 6 blade wheels, etc… Many of the recent performance gains that have been achieved with CAD designed billet wheels are possible now with cast or forged wheels, but for very limited production runs like Upgraded Porsche VTG’s, I don’t see that it will ever be realistic or cost effective to produce them this way.
“There is some controversy about the advantages of billet versus cast turbocharger upgrades. Billet compressor wheel technology is NOT new. It’s been around since the 80s. The material does not necessarily make a billet wheel produce more power, rather it is the ability to use CAD/CAM to design a billet wheel.
From a technical perspective, a billet compressor wheel is CNC’ed out of a solid piece of billet aluminum where as a traditional wheel is cast out of molten aluminum. The theory is a CNC'ed billet compressor wheel can be created with “less bulk” and less actual material, and CAD designs can take advantage of the new found “space” within the turbocharger inlet by redesigning the compressor aerodynamics to produce greater CFM with the same size inducer”.
“If the design of the compressor wheel is the same (billet versus cast) there should be no significant performance difference (aside from actual weight of the wheel and the physics of weight reduction.”
And finally the Garrett Quote:
"in OE applications, fully-machined wheels can withstand higher centrifugal stresses due to differences in the base material. Forgings are inherently stronger than the typical casting in this respect. However, when Honeywell engineers choose a fully-machined wheel over a cast wheel, they are only doing so to prolong the wheel's life in extreme duty-cycle OE applications where the turbo speed is constantly cycled. A typical example is a city bus, in which the turbo is frequently subjected to rapid transitions between high-load (full throttle) and low-load (idle). Compressor wheels can fail in low-cycle fatigue (LCF) in these applications, which is where fully-machined wheels offer an advantage in strength and lifetime. However, the typical aftermarket turbocharger will not be subjected to such extreme cycling."
Now when it comes to the Billet housing, we did it for similar reasons to the usage of Billet on the compressor wheels. Versatility is the key. We can machine this housing to take several different wheels, 2 different variants of VTG CHRA’s and the internal dimensions as well as the volute sections can be machined for many different AR’s and configurations. Most of these changes were made and developed during our own internal testing, and the end result has been streamlined to only a few different configurations that we will offer for sale. Now in regard to sizing, you cannot just continue to increase the size of the compressor in the hopes that the VTG controlled Turbine ratio can keep up, to a point it certainly can. I can tell you that the window is not infinite by any means. You can quickly exceed the usable vane frequency, which results in uncontrolled boost, in addition to over-speeding the shaft. Through our extensive VTG testing we explored the limits of the VTG, but realized quickly that there was an optimal speed for the turbine, as well as an optimal range for the VTG vanes to work within, etc… What we did to correct the effect of a large compressor coupled with a standard VTG turbine, was we added various levels of clipping to the turbine wheel. This is a tricky procedure, and way more harm can be done that good, if not done by a professional. In the end result, it is possible to increase turbine flow, lower the shaft speed, and decrease vane frequency. A positive side effect is that provided you have the rest of the “setup” to push the limits, increased turbine flow has the ability to decrease pre-turbine backpressure, and lower EGT.
Again, ALL factors are setup sensitive, and I only have specifics on the components that we have tested and tuned around.
Last, in regard to lag. Again, setup sensitive, it is not only possible, but probable, that with upgraded VTG’s you will see a faster boost response than standard. If anyone followed along on the progress of the CMS press car “War Admiral” (you can search for the threads here) the zero to 60 time dropped to an impressive 2.6 seconds, and even with a 68mm compressor, the boost response far exceeds standard.
I cannot go into any more specific details as the information is propriatary.
In regard to just the compressor wheel, IE: Billet vs Cast, these statements that I quoted below are 100% correct as I read them. Once you switch to Billet and CAD design, the window of performance opens wide up. Yes, there are aerodynamic gains possible, as well as the addition of blades, IE: our 7 blade wheels vs the cast 6 blade wheels, etc… Many of the recent performance gains that have been achieved with CAD designed billet wheels are possible now with cast or forged wheels, but for very limited production runs like Upgraded Porsche VTG’s, I don’t see that it will ever be realistic or cost effective to produce them this way.
“There is some controversy about the advantages of billet versus cast turbocharger upgrades. Billet compressor wheel technology is NOT new. It’s been around since the 80s. The material does not necessarily make a billet wheel produce more power, rather it is the ability to use CAD/CAM to design a billet wheel.
From a technical perspective, a billet compressor wheel is CNC’ed out of a solid piece of billet aluminum where as a traditional wheel is cast out of molten aluminum. The theory is a CNC'ed billet compressor wheel can be created with “less bulk” and less actual material, and CAD designs can take advantage of the new found “space” within the turbocharger inlet by redesigning the compressor aerodynamics to produce greater CFM with the same size inducer”.
“If the design of the compressor wheel is the same (billet versus cast) there should be no significant performance difference (aside from actual weight of the wheel and the physics of weight reduction.”
And finally the Garrett Quote:
"in OE applications, fully-machined wheels can withstand higher centrifugal stresses due to differences in the base material. Forgings are inherently stronger than the typical casting in this respect. However, when Honeywell engineers choose a fully-machined wheel over a cast wheel, they are only doing so to prolong the wheel's life in extreme duty-cycle OE applications where the turbo speed is constantly cycled. A typical example is a city bus, in which the turbo is frequently subjected to rapid transitions between high-load (full throttle) and low-load (idle). Compressor wheels can fail in low-cycle fatigue (LCF) in these applications, which is where fully-machined wheels offer an advantage in strength and lifetime. However, the typical aftermarket turbocharger will not be subjected to such extreme cycling."
Now when it comes to the Billet housing, we did it for similar reasons to the usage of Billet on the compressor wheels. Versatility is the key. We can machine this housing to take several different wheels, 2 different variants of VTG CHRA’s and the internal dimensions as well as the volute sections can be machined for many different AR’s and configurations. Most of these changes were made and developed during our own internal testing, and the end result has been streamlined to only a few different configurations that we will offer for sale. Now in regard to sizing, you cannot just continue to increase the size of the compressor in the hopes that the VTG controlled Turbine ratio can keep up, to a point it certainly can. I can tell you that the window is not infinite by any means. You can quickly exceed the usable vane frequency, which results in uncontrolled boost, in addition to over-speeding the shaft. Through our extensive VTG testing we explored the limits of the VTG, but realized quickly that there was an optimal speed for the turbine, as well as an optimal range for the VTG vanes to work within, etc… What we did to correct the effect of a large compressor coupled with a standard VTG turbine, was we added various levels of clipping to the turbine wheel. This is a tricky procedure, and way more harm can be done that good, if not done by a professional. In the end result, it is possible to increase turbine flow, lower the shaft speed, and decrease vane frequency. A positive side effect is that provided you have the rest of the “setup” to push the limits, increased turbine flow has the ability to decrease pre-turbine backpressure, and lower EGT.
Again, ALL factors are setup sensitive, and I only have specifics on the components that we have tested and tuned around.
Last, in regard to lag. Again, setup sensitive, it is not only possible, but probable, that with upgraded VTG’s you will see a faster boost response than standard. If anyone followed along on the progress of the CMS press car “War Admiral” (you can search for the threads here) the zero to 60 time dropped to an impressive 2.6 seconds, and even with a 68mm compressor, the boost response far exceeds standard.
I cannot go into any more specific details as the information is propriatary.
+1
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Regarding Louis's response though, I do have a question: Does a faster 0-60 time, such as that of the War Admiral, necessarily mean there is less "lag"?
A car with more power AND more lag could *still* have a faster 0-60 time, no? The initial lag compensated by the great power increase.
A car with more power AND more lag could *still* have a faster 0-60 time, no? The initial lag compensated by the great power increase.
Former Vendor
Joined: Mar 2010
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From: Pompano Beach, FL
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Regarding Louis's response though, I do have a question: Does a faster 0-60 time, such as that of the War Admiral, necessarily mean there is less "lag"?
A car with more power AND more lag could *still* have a faster 0-60 time, no? The initial lag compensated by the great power increase.
A car with more power AND more lag could *still* have a faster 0-60 time, no? The initial lag compensated by the great power increase.
Just wait until PDK development is done. We are working on it around the clock, and it will be worth the wait.
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Louis at Champion and Mike at AWDsports THANK YOU so much for your posts. I feel like my brain has been filled with useful data (which will disappear after a couple of beers unfortunately) and I'm looking forward to future upgrades.
Let me see if I can dumb down some of the info and get a clear understanding of the turbo thing: As the exhaust flow increases (when turbo boost is "requested") the angles of the vanes change in response to the rpm of the engine. The turbine (driven by the directed exhaust) is fixed in size in all of the modded vtgs, and is the main determinant of turbo-lag. ie. if you increase the size of the turbine then there would be more lag. The compressor side of the turbo can be increased in size b/c it is the bottleneck since there can be more power gained by keeping the turbine side the same size while enlarging the compressor side. The air output from the turbo then goes through the intercooler and into the combustion chamber, right?
The key here is to have a system that targets the bottlenecks in the stock vtg turbo, and obviously there are a few brands of modifiers and a fairly large difference in price between the different systems suggesting that there is a range of performance available for modded vtgs.
Is that about right?
Let me see if I can dumb down some of the info and get a clear understanding of the turbo thing: As the exhaust flow increases (when turbo boost is "requested") the angles of the vanes change in response to the rpm of the engine. The turbine (driven by the directed exhaust) is fixed in size in all of the modded vtgs, and is the main determinant of turbo-lag. ie. if you increase the size of the turbine then there would be more lag. The compressor side of the turbo can be increased in size b/c it is the bottleneck since there can be more power gained by keeping the turbine side the same size while enlarging the compressor side. The air output from the turbo then goes through the intercooler and into the combustion chamber, right?
The key here is to have a system that targets the bottlenecks in the stock vtg turbo, and obviously there are a few brands of modifiers and a fairly large difference in price between the different systems suggesting that there is a range of performance available for modded vtgs.
Is that about right?
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