Misconceptions on Turbocharger inducer sizes
01-12-2007, 05:05 PM
#1
Misconceptions on Turbocharger inducer sizes
Turbocharger inducer sizes
Lately I have seen a lot of turbo inducer sizes quoted on the forums, the size of the compressor inducer will not tell you the performance capabilities of the turbocharger.
To do this you will require more information on the compressor wheel and the compressor housing. There are a number of factors in compressor wheel design that can dramatically change the performance.
Compressor maps are the best way are the best way to determine a wheels performance capabilities. You must also keep in mind that the map is obtained using a specific compressor housing. Using a different housing will change the map. You should look for a map that best meets your performance goals and also meets the engines surge requirements. A good design will do this and still protect your turbo from off throttle surge or bark that will reduce the life of the turbo, (the BD Super B is a good example)
The wheel trim (difference between inlet to outlet size) a larger diameter wheel rotating at the same speed will produce a higher air velocity that converts to higher pressure.
Also the length of the inducer veins can be different a larger shaft diameter would require a larger compressor hub diameter so inducer vein length would be shorter. (I have seen examples of 20lbs/min differential with the same size inducer)
New casting methods and hardening processes allows manufacturers to design thinner veined and taller compressor wheel designs without sacrificing strength. This also makes extended tip designs possible on high speed compressor wheels. In the past this design was used only on very large slower speed turbochargers.
Keep in mind that if you have two wheels with the same inducer size that perform at the same efficiency but one has a lager overall diameter. Borg-Warner’s extended tip is a good example as it increases diameter without changing much of the total mass, at the same rotating speed the larger diameter wheel will produce a higher air velocity and static pressure in the engine inlet plenum. This will result in more air into the engine when the valves are opened.
And then there is the turbine.
Twin or compounding turbochargers.
There is a misconception that bigger is always better when it comes to the turbochargers used for the first stage of compounding turbochargers, this is not always true. The rule of thumb in compounding is that the inducer size of the second stage turbo should be the same size as the first stage outlet. If this is not done you will risk over speeding the first stage. Say the first stage has an outlet size of 3.1 ins as on the S400 and you are using a HX35 as the second stage that has an inducer size of about 2.2 ins, the match will not be very good. Yes you will produce boost in fact the first stage pressure will be high( 35-40lbs) and the temperature will be also be high. The reason this happens is a compressor wheel is an open rotating compressor and not positive like a piston compressor. When the air encounters a smaller diameter it will not compress to that size. Instead the flow becomes restricted, this reduction in flow reduces compressor wheel load and the turbocharger speeds up producing a higher boost at a lower flow. The second stage wastegate now has a problem controlling first stage air velocity and increased boost. Usually this is means the wastegate has to be opened almost fully instead of controlling overall boost levels. If the match was correct the overall boost level could be controlled with the second stage wastegate. The end result is running any turbo with the wastegate open all the time is very inefficient. A wastegate is designed to control the max boost level not to run open all the time.
When we built the BD compounding system we built so that it could be controlled this way. The only other factor that will increase boost is too much fueling. We developed our own wastgate that can be adjusted to 65lbs this has worked very well on 98-02 trucks. Our own truck produces 625HP and has run the quarter mile in 12,2 seconds and has been a daily driver for over 2 years. People who have made the change from twins using a larger first stage are surprised at the increased performance. They also thought bigger was better
John Todd
Lately I have seen a lot of turbo inducer sizes quoted on the forums, the size of the compressor inducer will not tell you the performance capabilities of the turbocharger.
To do this you will require more information on the compressor wheel and the compressor housing. There are a number of factors in compressor wheel design that can dramatically change the performance.
Compressor maps are the best way are the best way to determine a wheels performance capabilities. You must also keep in mind that the map is obtained using a specific compressor housing. Using a different housing will change the map. You should look for a map that best meets your performance goals and also meets the engines surge requirements. A good design will do this and still protect your turbo from off throttle surge or bark that will reduce the life of the turbo, (the BD Super B is a good example)
The wheel trim (difference between inlet to outlet size) a larger diameter wheel rotating at the same speed will produce a higher air velocity that converts to higher pressure.
Also the length of the inducer veins can be different a larger shaft diameter would require a larger compressor hub diameter so inducer vein length would be shorter. (I have seen examples of 20lbs/min differential with the same size inducer)
New casting methods and hardening processes allows manufacturers to design thinner veined and taller compressor wheel designs without sacrificing strength. This also makes extended tip designs possible on high speed compressor wheels. In the past this design was used only on very large slower speed turbochargers.
Keep in mind that if you have two wheels with the same inducer size that perform at the same efficiency but one has a lager overall diameter. Borg-Warner’s extended tip is a good example as it increases diameter without changing much of the total mass, at the same rotating speed the larger diameter wheel will produce a higher air velocity and static pressure in the engine inlet plenum. This will result in more air into the engine when the valves are opened.
And then there is the turbine.
Twin or compounding turbochargers.
There is a misconception that bigger is always better when it comes to the turbochargers used for the first stage of compounding turbochargers, this is not always true. The rule of thumb in compounding is that the inducer size of the second stage turbo should be the same size as the first stage outlet. If this is not done you will risk over speeding the first stage. Say the first stage has an outlet size of 3.1 ins as on the S400 and you are using a HX35 as the second stage that has an inducer size of about 2.2 ins, the match will not be very good. Yes you will produce boost in fact the first stage pressure will be high( 35-40lbs) and the temperature will be also be high. The reason this happens is a compressor wheel is an open rotating compressor and not positive like a piston compressor. When the air encounters a smaller diameter it will not compress to that size. Instead the flow becomes restricted, this reduction in flow reduces compressor wheel load and the turbocharger speeds up producing a higher boost at a lower flow. The second stage wastegate now has a problem controlling first stage air velocity and increased boost. Usually this is means the wastegate has to be opened almost fully instead of controlling overall boost levels. If the match was correct the overall boost level could be controlled with the second stage wastegate. The end result is running any turbo with the wastegate open all the time is very inefficient. A wastegate is designed to control the max boost level not to run open all the time.
When we built the BD compounding system we built so that it could be controlled this way. The only other factor that will increase boost is too much fueling. We developed our own wastgate that can be adjusted to 65lbs this has worked very well on 98-02 trucks. Our own truck produces 625HP and has run the quarter mile in 12,2 seconds and has been a daily driver for over 2 years. People who have made the change from twins using a larger first stage are surprised at the increased performance. They also thought bigger was better
John Todd
01-12-2007, 07:51 PM
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Ahhhhh......not everyone will know the different theories and science behind turbocharging a diesel engine true, however for some people the" hey lets bolt this on and see what happends" method, right or wrong is a very good way to learn. I'll admit I drag junk home from work and bolt it ,glue it, nail it or weld it onto my own junk in hopes of looking better or going faster.Sometimes it works and sometimes it leaves a oil shower all over the shop walls,does that mean I should trying. I'll take the first step and say Hi my name is Eric and i have a problem.
01-12-2007, 08:07 PM
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John Todd,
Last time I checked BORG WARNER manufactures the parts for your BD turbos.
Borg Warner also manufactures parts that go into the B1's, HTT's, II's, and parts for other performance turbos.
Of course rating turbo's by just wheel sizes is kind of basic but for the most part many of the aftermarket turbos today are using the SAME PARTS.
People often refer to wheel sizes because it is a good or even excellent reference point especially when dealing with the same kind of wheels that are basically coming from the SAME COMPANY!!!
I for one am pretty darn glad that people are asking more questions these days about which or what size wheels they are getting when they buy an aftermarket charger. Many vendors try to beat around the bush about what they are selling or dont want to say. It puzzles me that companies want to hide specs on their turbos.
The more people talk about turbo's be it housing sizes, model numbers, wheel sizes, OEM specifics, etc the more people will learn (which is nothing but GOOD!)
I think some vendors are trying to make a one size fits all turbo and that just doesnt work. That usually results in someone who is wanting to upgrade right after installing a turbo they just purchased.
I for one like to be able pick through sizing and specs to choose what I need. I can't blame vendors for naming by size....
A prime example would be someone who wants fast spool up and decent top end in the 450hp area would usually pick a 62mm inducer unit with a 60mm turbine wheel and a what equates to be a 14cm wastegated housing. That turbo can be had from several different vendors...
Now if the customer knew what sizes you guys were using they might be more willing to purchase one of your Special B's....
We can only guess what some vendors are trying to offer when they say "ours is great just trust us"...I for one do not support that kind of operation. I would rather know what size I am getting or be able to decide for myself what best fits my needs....
My .02
PS The misconception on turbo inducer size is not really a misconception!
Last time I checked BORG WARNER manufactures the parts for your BD turbos.
Borg Warner also manufactures parts that go into the B1's, HTT's, II's, and parts for other performance turbos.
Of course rating turbo's by just wheel sizes is kind of basic but for the most part many of the aftermarket turbos today are using the SAME PARTS.
People often refer to wheel sizes because it is a good or even excellent reference point especially when dealing with the same kind of wheels that are basically coming from the SAME COMPANY!!!
I for one am pretty darn glad that people are asking more questions these days about which or what size wheels they are getting when they buy an aftermarket charger. Many vendors try to beat around the bush about what they are selling or dont want to say. It puzzles me that companies want to hide specs on their turbos.
The more people talk about turbo's be it housing sizes, model numbers, wheel sizes, OEM specifics, etc the more people will learn (which is nothing but GOOD!)
I think some vendors are trying to make a one size fits all turbo and that just doesnt work. That usually results in someone who is wanting to upgrade right after installing a turbo they just purchased.
I for one like to be able pick through sizing and specs to choose what I need. I can't blame vendors for naming by size....
A prime example would be someone who wants fast spool up and decent top end in the 450hp area would usually pick a 62mm inducer unit with a 60mm turbine wheel and a what equates to be a 14cm wastegated housing. That turbo can be had from several different vendors...
Now if the customer knew what sizes you guys were using they might be more willing to purchase one of your Special B's....
We can only guess what some vendors are trying to offer when they say "ours is great just trust us"...I for one do not support that kind of operation. I would rather know what size I am getting or be able to decide for myself what best fits my needs....
My .02
PS The misconception on turbo inducer size is not really a misconception!
01-13-2007, 01:55 AM
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heh, funny how when a company man starts spouting science, its always in support of its product. If ya wanna be taken seriously, leave your company and products out of it. Otherwise, even a rittalin addicted 4th grader will dismiss it as advertising...
Other than that, I did leanr some stuff from ya, so danke.
Other than that, I did leanr some stuff from ya, so danke.
01-13-2007, 04:24 AM
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This lead post is informative, and I'm not as cynical as the Other Justin (nor as knowledgeable). That said, Justin (pourindiesel) makes some valid points.
While the lead post is technically correct, the real world circumstances mean that confusion he cites is mosly immaterial because all the variables he mentions essential are NOT variables-- the diesel buying public just doesn't have that many choices. It's either outdated Holset homebrew knockoffs or BW stuff.
jmo
While the lead post is technically correct, the real world circumstances mean that confusion he cites is mosly immaterial because all the variables he mentions essential are NOT variables-- the diesel buying public just doesn't have that many choices. It's either outdated Holset homebrew knockoffs or BW stuff.
jmo
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01-13-2007, 07:45 AM
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Doug Smith
01-13-2007, 09:27 AM
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heh, funny how when a company man starts spouting science, its always in support of its product. If ya wanna be taken seriously, leave your company and products out of it. Otherwise, even a rittalin addicted 4th grader will dismiss it as advertising...
Other than that, I did leanr some stuff from ya, so danke.
Other than that, I did leanr some stuff from ya, so danke.
01-13-2007, 09:55 AM
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TRIM values are expressed as 45, 50, 55, etc... and can only go from 0 to 100. A value of 100 means Dp = Dg
A large TRIM indicates a large turbine diameter.
A TRIM of 55, gives 10% more caudal than a TRIM of 50.
TRIM is used in the same way for turbine wheels as for compressor wheels.
TRIM is calculated through the following formula.
TRIM = ( Dp / Dg )² x 100
Si Dg = 50 mm y Dp = 35 mm
TRIM = ( 35/50 )² x 100 = 49
For trim here is a way to figure what u want or what it is , as maps go for the daily driver there good but for the guy who has big injectors, pumps and such and spin it say 60+ there probaly off the map anyways depends on charger to
I like how they want to tell u the turbo u need by usen the sceince but they dont tell u how to use the science ,,,its out there just have to find it
A large TRIM indicates a large turbine diameter.
A TRIM of 55, gives 10% more caudal than a TRIM of 50.
TRIM is used in the same way for turbine wheels as for compressor wheels.
TRIM is calculated through the following formula.
TRIM = ( Dp / Dg )² x 100
Si Dg = 50 mm y Dp = 35 mm
TRIM = ( 35/50 )² x 100 = 49
For trim here is a way to figure what u want or what it is , as maps go for the daily driver there good but for the guy who has big injectors, pumps and such and spin it say 60+ there probaly off the map anyways depends on charger to
I like how they want to tell u the turbo u need by usen the sceince but they dont tell u how to use the science ,,,its out there just have to find it
01-13-2007, 10:06 AM
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so, all you can do is go by word of mouth real world results... whose turbos are on the highest powered trucks? whose turbos offer great spool-up, good cooling, and low backpressure? etc.
it took me a long time to come around to that after spending years in the gas/turbo world where I just looked at maps till I found what I needed and bought it or had it built.
all I know is I don't hear people raving over the BD offerings all over the net like I see them doing about some of their competators... maybe that's what this sales pitch is all about
01-13-2007, 10:29 AM
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Informative post nevertheless..keep it up..makes us appreceiate the engineers that think this stuff up so we all can PLAY..PULL..DRAG..YAK..STRUT..BOMB..and look good doin' it...Never did like Math..to many moving parts...hmmm....
01-13-2007, 10:34 AM
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I'd noticed the lack of maps Forrest, and agree that all we have to go on is what guys with similar fuel have had sucess with. Seems to be the Phat Shaft variants for the most part, sizing the compressor wheel for their fuel/use.
I will freely admit that I am not as knowledgable on some things as others, but facts and data can teach a lot.
Can you share the maps? I for one would be very intersted to see them...
I will freely admit that I am not as knowledgable on some things as others, but facts and data can teach a lot.
Compressor maps are the best way are the best way to determine a wheels performance capabilities.
01-13-2007, 11:15 AM
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Some people have large exducers that blow hot air at high pressure ratios.
I have found that beans and cornbread, cabbage, beer, and Ben and Jerrys will produce a higher mass flow with the same compressor exducer than say: water, carrots, potatoes, and corn.
I have found that beans and cornbread, cabbage, beer, and Ben and Jerrys will produce a higher mass flow with the same compressor exducer than say: water, carrots, potatoes, and corn.