Turbine Maps

[Z24O]

being easter's a boring time

anyone got a few minutes to explain to me how to read/interpret turbine maps (now that i understand compressor maps!!)

http://www.turbobygarrett.com/turbobygarre...T40/GT4088R.htm

most info i've read says worry more about the compressor side,however i am interested in understanding spool/boost threshold as it applies to turbine maps and just as there are 2 sides to every coin and story,i know there are definately 2 sides to a turbo.....compressor AND turbine.

cheers,paul

[Z24O]

bump

[discopotato03]

Paul turbine maps are a graph of exhaust gas flow in pounds per minute vs exhaust manifold pressure in pressure ratio/atmospheres/Bar . 1 pressure ratio is equal to 1 atmosphere or 1 bar meaning atmospheric pressure at sea level . The coloured line tells you how many pounds of gas the turbine/housing combination will flow as the turbine inlet pressure rises . Note that when it reaches its peak generally the rising turbine inlet pressure doesn't increase its flow rating . Also note that higher AR turbine housings do increase total flow .

Most people tend to spend more time thinking about the world beating compressor that what drives it . The very best compressor is useless without something to support it and spin it .

Spooling or accelerating a radial compressor is all about bringing it up to a high enough speed to make it pass enough gas to provide positive pressure in this case into an expanding volume (accelerating piston pump) . Turbine and housing design are critical to how a compressor performs . The turbine ideally weighs nothing , absorbs heaps of velocity energy from the hot expanding exhaust gasses and creates no resistance to exhaust gas flow .

The turbine needs to be large enough to adequately drive the compressor ie enough vane sail area to take maximum advantage of the exhaust gas energy .

Choise of compressor is very important as well as the turbine in the spool stakes . The rule of thumb is that the more blades and thicker section these blades are , more turbine energy is required to accelerate the compressor . The bottom line is that the easier you make it for the turbine load wise the more likley it will rip the compressor up to boosting revs . In other words the turbines with the least work to do will accelerate much faster than those with high work loads given the same exhaust gas velocity .

Turbine blades are like levers so the longer they are the more axial force (shaft torque) they generate . The greater shaft torque you have the greater power you have to drive the compressor .

Rule 1) Spec your compressor to have a little more (10-15%) than you flow requirements . This way you put a reasonable work load ceiling on the turbine , not major overload through wanting an extra 200 DHP (dream horsepower) somewhere between next week and never . Lag is free so if you want it go for it .

Rule 2) The 15% rule (keep compressor and turbine within 15% of each other diametre wise) is valid . It keeps the Gemini graduates from wanting to put 102mm GT42 compressors on 56mm T25 turbines . Actually it keeps the tips speeds manageable and ensures the turbines "levers" are long enough to drive the compressor .

Wheel trim sizes . The smaller the compressor trim size is the less air it will pump . The less air pumping capacity also means less workload for the turbine to shoulder . Ever wonder why Garrett turbos use big trim compressors while the HKS equivilent uses a smaller trim and spools earlier/faster - now you know .

Turbine trim size . The major or basic turbine diametre size dictates how much torque it developes . The trim size (and housing AR) dictates its maximum flow and velocity . With all else being equal reducing turbine trim increases the gas speed and trades gas speed for mass flow volume . So the response is increased but the flow limit is reached sooner . Garret have done this with the GT4082 which is also on that turbobygarrett site . Note the turbine is 77mm like the GT4088 and 4088R but its trim is 73 rather than 78 or 84 . Also its 82mm 50T compressor is of a smaller lower flow design that the 88 or 88R's different 88mm wheel designs . They obviously wanted more response and less airflow possibly for a smaller engine or lower power (airflow) requirement .

As I mentioned yesterday Garrett is beginning to come down a little on turbine trim size so it could allow them to go up a turbine family for each compressor wheel family and maintain response via the slightly smaller trim number . This could assist spool and lower turbine inlet pressure at the same time . It may be like a 3071 rather than a 2871 , a 3576 rather than a 3076 , 3782 instead of 3582 and so on .

Everyones snoring for some reason ? Night all ......

Edited April 16, 2006 by discopotato03

[Craved]

taught me alot .. nice info there Disco

[discopotato03]

Want more ?

There is a bit more dogma to add about turbine trims and turbine housing AR ratios .

A couple of different approaches can be taken to "tune" the turbine/housing combination around desired shaft torque , shaft speed and mass flow vs gas speed which ultimately means turbine inlet pressure (TIP) .

Because of production costs the turbo manufacturer may decide to cast only one turbine housing in a fixed AR ratio . To be able to vary the turbine speed for different applications they would need to make several trim sizes of the basic turbine and profile machine the housing to suit . Or the other way round , make only one size and trim of turbine and cast several different AR ratio turbine housings .

In the past plan B has generally been the case and makes economic sense when you remember that for example Garrett uses say the GT30 turbine in heaps of different turbo cartridge options , so the three basic AR size housings covers the whole range of turbos that use this turbine . The best situation would be if we had different trim turbine (and compressor) options and a choise of turbine housing AR ratios but the spare parts side gets more involved and expensive . And besides mobs like HKS need a bit of latitude to change things and charge a premium for their technological magnificence/thermonuclear protection and titanium show off tag .

Cheers A .

[Z24O]

Paul turbine maps are a graph of exhaust gas flow in pounds per minute vs exhaust manifold pressure in pressure ratio/atmospheres/Bar . 1 pressure ratio is equal to 1 atmosphere or 1 bar meaning atmospheric pressure at sea level . The coloured line tells you how many pounds of gas the turbine/housing combination will flow as the turbine inlet pressure rises . Note that when it reaches its peak generally the rising turbine inlet pressure doesn't increase its flow rating . Also note that higher AR turbine housings do increase total flow .

Most people tend to spend more time thinking about the world beating compressor that what drives it . The very best compressor is useless without something to support it and spin it .

Spooling or accelerating a radial compressor is all about bringing it up to a high enough speed to make it pass enough gas to provide positive pressure in this case into an expanding volume (accelerating piston pump) . Turbine and housing design are critical to how a compressor performs . The turbine ideally weighs nothing , absorbs heaps of velocity energy from the hot expanding exhaust gasses and creates no resistance to exhaust gas flow .

The turbine needs to be large enough to adequately drive the compressor ie enough vane sail area to take maximum advantage of the exhaust gas energy .

Choise of compressor is very important as well as the turbine in the spool stakes . The rule of thumb is that the more blades and thicker section these blades are , more turbine energy is required to accelerate the compressor . The bottom line is that the easier you make it for the turbine load wise the more likley it will rip the compressor up to boosting revs . In other words the turbines with the least work to do will accelerate much faster than those with high work loads given the same exhaust gas velocity .

Turbine blades are like levers so the longer they are the more axial force (shaft torque) they generate . The greater shaft torque you have the greater power you have to drive the compressor .

Rule 1) Spec your compressor to have a little more (10-15%) than you flow requirements . This way you put a reasonable work load ceiling on the turbine , not major overload through wanting an extra 200 DHP (dream horsepower) somewhere between next week and never . Lag is free so if you want it go for it .

Rule 2) The 15% rule (keep compressor and turbine within 15% of each other diametre wise) is valid . It keeps the Gemini graduates from wanting to put 102mm GT42 compressors on 56mm T25 turbines . Actually it keeps the tips speeds manageable and ensures the turbines "levers" are long enough to drive the compressor .

Wheel trim sizes . The smaller the compressor trim size is the less air it will pump . The less air pumping capacity also means less workload for the turbine to shoulder . Ever wonder why Garrett turbos use big trim compressors while the HKS equivilent uses a smaller trim and spools earlier/faster - now you know .

Turbine trim size . The major or basic turbine diametre size dictates how much torque it developes . The trim size (and housing AR) dictates its maximum flow and velocity . With all else being equal reducing turbine trim increases the gas speed and trades gas speed for mass flow volume . So the response is increased but the flow limit is reached sooner . Garret have done this with the GT4082 which is also on that turbobygarrett site . Note the turbine is 77mm like the GT4088 and 4088R but its trim is 73 rather than 78 or 84 . Also its 82mm 50T compressor is of a smaller lower flow design that the 88 or 88R's different 88mm wheel designs . They obviously wanted more response and less airflow possibly for a smaller engine or lower power (airflow) requirement .

As I mentioned yesterday Garrett is beginning to come down a little on turbine trim size so it could allow them to go up a turbine family for each compressor wheel family and maintain response via the slightly smaller trim number . This could assist spool and lower turbine inlet pressure at the same time . It may be like a 3071 rather than a 2871 , a 3576 rather than a 3076 , 3782 instead of 3582 and so on .

Everyones snoring for some reason ? Night all ......

thanks for that dicopotato,great post

so am i to assume that the turbine flow(lbs/min)=exhaust flow=compressor flow=roughly 1lb/min for every 10HP measured at the flywheel???

what i am trying to work out is which BB turbo i should use on my rb30et for around 250+ rwkw whilst maintaining a low(1500-2000 rpm) boost threshold and redline of 5500 rpm......or is this pie in the sky??

at this stage i am leaning towards the garrett gt3037 500 HP variant with the .63 internal wastegate....what do you think?.......or would i be choking the top end(if so would a larger external gate solve this?) or be better with the .82 external wastegate?

thanks again

paul.

ps hks 2530 and garrett gt3071 (600 hp) have also been recommended for my purpose

[discopotato03]

thanks for that dicopotato,great post

so am i to assume that the turbine flow(lbs/min)=exhaust flow=compressor flow=roughly 1lb/min for every 10HP measured at the flywheel???

what i am trying to work out is which BB turbo i should use on my rb30et for around 250+ rwkw whilst maintaining a low(1500-2000 rpm) boost threshold and redline of 5500 rpm......or is this pie in the sky??

at this stage i am leaning towards the garrett gt3037 500 HP variant with the .63 internal wastegate....what do you think?.......or would i be choking the top end(if so would a larger external gate solve this?) or be better with the .82 external wastegate?

thanks again

paul.

ps hks 2530 and garrett gt3071 (600 hp) have also been recommended for my purpose

A lot of this is going to depend on how much + you want on that 250 RWKW . I would have though the 1500-2000 rpm boost threshold is way too low for an RB30 - any RB30 . For 250Kw you could get that NA if everything was spec'd to achieve it ie CR cams and no loss throttling .

For turbo I would keep the CR up in the 9:1 region , cams could be std for that power level . I would size the turbo to come in around 3000 minium and you wont need a lot of boost for 250 Kw .

I guess I would look at Garretts GT30R (unit no 700382-12 specifically) and have a think about their .82 or 1.06 AR turbine housings . The .82 should be availabe soon with an integral wastegate and maybe a 1.06 as well .

I have to say that this would be a very expensive 340Hp , its probably easily done with an RB25 Neo or the 33 version if everything is well thought out and applied . In those cases I would run the real GT3071R or the 52 compressor trim HKS GT3037 . Both of these run out of air at about 42 odd lbs so more than enough for 340 Hp .

Cheers A .

[paulr33]

the hks 2530 i think would be too small for a 3 litre.

it would run out of puff real quick, but the again the rb30et head doesnt flow as much as the rb25 so it may be ok. but still very small, the standard turbocharger hiflowed would be better than the 2530

[Z24O]

A lot of this is going to depend on how much + you want on that 250 RWKW . I would have though the 1500-2000 rpm boost threshold is way too low for an RB30 - any RB30 . For 250Kw you could get that NA if everything was spec'd to achieve it ie CR cams and no loss throttling .

For turbo I would keep the CR up in the 9:1 region , cams could be std for that power level . I would size the turbo to come in around 3000 minium and you wont need a lot of boost for 250 Kw .

I guess I would look at Garretts GT30R (unit no 700382-12 specifically) and have a think about their .82 or 1.06 AR turbine housings . The .82 should be availabe soon with an integral wastegate and maybe a 1.06 as well .

I have to say that this would be a very expensive 340Hp , its probably easily done with an RB25 Neo or the 33 version if everything is well thought out and applied . In those cases I would run the real GT3071R or the 52 compressor trim HKS GT3037 . Both of these run out of air at about 42 odd lbs so more than enough for 340 Hp .

Cheers A .

thanks adrian,

how soon will the int wg be available for the .82 housing..........have they given a date?(do you supply them?)

not sure what you mean by very expensive 340HP....at this stage all i'm hoping to change is the turbo(less than $2000) to achieve my goal??if i was starting afresh i'd probably go rb30/26

with regard to my question re corrected turbine gas flow......how do you work out what that value is for a given engine(presuming you somehow need to match exhaust flow to turbine characteristics??)

the specs for the gt3071 look like it is a smaller turbo(faster spooling?) what reason are you recommending the gt3076 for the rb30 and the 3071 for the rb25(r33)?

cheers,paul.