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Thread: How To: Read Compressor Maps

  1. #26
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    Quote Originally Posted by M3TurboCa
    Jacob thanks for the information very helpfull.

    A question if Im running say 12 psi do I figure pr as .8 or pr of 2.0 for system loss as the compressor is actually flowing say 14.5 psi but getting 12 in the manifold.
    I addressed this "loss" earlier in the thread. I say use a PR of 1.8 and just realize that there will be losses in the system. How much, you can't really say without lots of measurements. Just do the calculation for the PR of what you want to run(or maybe even a bit higher to be more conservative) and then realize that there are some losses in the system that will make the PR go up, and probably the mass airflow to go down up top(lower VE). Without knowing the losses, you could actually get a more inaccurate final result if you grossly overestimate losses in a well optimized setup.

    Compressor maps are only a rough guide for picking a decent match of a compressor to your engine. There are alot of assumptions that go into calculating where the compressor will actually be on the map as your rev the engine up, so don't take the result as "hard data." They're a useful tool to compare different turbos and get a very rough idea on how they will perform though.


    Shame we don't have turbine maps available though...


    FYI.
    I noticed that your calculation of boost pressure is incorrect in the spreadsheet.

    I changed my to input boost and calculate pressure ratio - (boost + 14.7)/14.7

    p.s. thanks for the spreadsheet
    Really? It works fine on mine(assuming atmospheric is 14.7 psi). Maybe I uploaded an old version or something. I'll update it.

    I've also got a pretty hefty spreadsheet from a guy on a 240SX board that worked with a Grand National guy to put together a serious excel sheet on this kinda stuff. It's a bit much for the casual person though. I'll dig it up and post it later on.

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    I think what happend is that you used 1 instead of 14.7. This will change the results of the calculation.

    If you put this into the formula, it is more correct: =B6*14.7-14.7

    I admit that it doesn't change the results much ~ .25-.50 psi of boost.

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    Hi all,

    I'm new to the board and even though I don't own a BMW (I own a Porsche 930 turbo) I have learned alot about forced induction.

    As for the surge line too big of a turbo running too much boost with a small motor can cause surge too. It's all about the engine displacement, mods and boost level. What is hard to know is calculating the mods in the equation. Also like you guys mentioned the pressure drop in the system. That's why there is basic displacement range for a particular map. You can use a turbo calculator to get a good enough idea but one should figure out the pressure drop in the system. Just hook a gauge to the cold side and one at the intake manifold and test drive your car. My opinion on matching a compressor wheel to an engine is simple. Down load a turbo calculator and input the data of your motor and what your max boost will be. Then plot at what rpm you want full boost and then redline. Where you get full boost should be within the surge line and at redline no further to the right of the second island. Less power at less efficiency moving to the right of the map going more efficient as you run more power. I can't stress enough to stay as efficient as possible thus being within the first 2 middle islands.

    As for the turbine is commonly overlooked yet important. You need to size the turbine or trim for the power then pick an A/R that will give you the spool characteristics you want without too much exhaust pressure. Again what boost level your going to run will be critical in knowing how to decide this. You don't want more than a 2.5:1 exhaust:boost pressure ratio.

    Might be selling my car next spring to get a BMW since my goals are complete and I need another project.

    Brent

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    Quote Originally Posted by Brent 930
    Hi all,

    I'm new to the board and even though I don't own a BMW (I own a Porsche 930 turbo) I have learned alot about forced induction.

    As for the surge line too big of a turbo running too much boost with a small motor can cause surge too. It's all about the engine displacement, mods and boost level. What is hard to know is calculating the mods in the equation. Also like you guys mentioned the pressure drop in the system. That's why there is basic displacement range for a particular map. You can use a turbo calculator to get a good enough idea but one should figure out the pressure drop in the system. Just hook a gauge to the cold side and one at the intake manifold and test drive your car. My opinion on matching a compressor wheel to an engine is simple. Down load a turbo calculator and input the data of your motor and what your max boost will be. Then plot at what rpm you want full boost and then redline. Where you get full boost should be within the surge line and at redline no further to the right of the second island. Less power at less efficiency moving to the right of the map going more efficient as you run more power. I can't stress enough to stay as efficient as possible thus being within the first 2 middle islands.
    Most turbo calculators I've seen are ridiculously simplistic. They just look up Garrett's size recommendations and make sure the "estimated" power output is within Garrett's quoted claims. I had one recommending a GT25R for my 2.0L engine. Keep in mind, this is SMALLER than my stock T25 as far as power potential goes. It'd probably max out power at around 220rwhp, and be almost completely off the efficiency map. They're just simple little programs that do the most basic "turbo matching" possible in my experience.

    You don't want more than a 2.5:1 exhaust:boost pressure ratio.
    I agree, but find me an easy way to measure exhaust pressure before the turbine inlet and I'll be the first to buy you a cold beer!

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    Quote Originally Posted by Def
    Most turbo calculators I've seen are ridiculously simplistic. They just look up Garrett's size recommendations and make sure the "estimated" power output is within Garrett's quoted claims. I had one recommending a GT25R for my 2.0L engine. Keep in mind, this is SMALLER than my stock T25 as far as power potential goes. It'd probably max out power at around 220rwhp, and be almost completely off the efficiency map. They're just simple little programs that do the most basic "turbo matching" possible in my experience.



    I agree, but find me an easy way to measure exhaust pressure before the turbine inlet and I'll be the first to buy you a cold beer!
    You have to be smarter than the avg. bear when using the calculator. It's up to you to decide where on the compressor map you want to be thus deciding which wheel is best for your needs. Then matching the turbine for what you want. I can tell you to keep your exhaust pressure at approx. that ratio regardless of boost pressure you will need to size the A/R between .69-.82. If your going to get serious you need an engine dyno and have all kinds of gauges hooked up. When I bought and then had my turbo modified I spent countless hours studying turbo chargers and the exhaust components before doing so. I didn't try to understand how the air molecules are flowing through the cold side and the gases through the turbine but in depth otherwise. There is a balance and you can't have your cake and eat it too.

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    screw a long copper tube into your EGT bung, make sure its in some airflow to keep the tube as cool as possible then attach your pressure gage to the tube.

    where's my beer
    Originally posted by Beau
    the turbo is the perfect garbage can....

  7. #32
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    Quote Originally Posted by Brent 930
    You have to be smarter than the avg. bear when using the calculator. It's up to you to decide where on the compressor map you want to be thus deciding which wheel is best for your needs. Then matching the turbine for what you want. I can tell you to keep your exhaust pressure at approx. that ratio regardless of boost pressure you will need to size the A/R between .69-.82. If your going to get serious you need an engine dyno and have all kinds of gauges hooked up. When I bought and then had my turbo modified I spent countless hours studying turbo chargers and the exhaust components before doing so. I didn't try to understand how the air molecules are flowing through the cold side and the gases through the turbine but in depth otherwise. There is a balance and you can't have your cake and eat it too.
    I've just found a quick look at a compressor map and a back of the envelope calculation and some intuition giving you the turbine A/R and wheel works alot better than those blasted turbo calculators. They seem more like marketing material for a specific line of turbos more than real help IMO.

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    Quote Originally Posted by Def
    I've just found a quick look at a compressor map and a back of the envelope calculation and some intuition giving you the turbine A/R and wheel works alot better than those blasted turbo calculators. They seem more like marketing material for a specific line of turbos more than real help IMO.
    If you need any help matching a turbo to your motor let me know. By the way something else I figured out is just because the cold side of an inducer is larger doesn't mean it flows more air. There is a ratio between the inducer and exducer that will dictate both the flow and at what pressure level it's most efficient at while affecting the spool some but not nearly as much as the hot side. This ratio also changes the flow and spool rate on the turbine side. It can get complex but is fun as hell to learn about.

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    Quote Originally Posted by Brent 930
    If you need any help matching a turbo to your motor let me know. By the way something else I figured out is just because the cold side of an inducer is larger doesn't mean it flows more air. There is a ratio between the inducer and exducer that will dictate both the flow and at what pressure level it's most efficient at while affecting the spool some but not nearly as much as the hot side. This ratio also changes the flow and spool rate on the turbine side. It can get complex but is fun as hell to learn about.
    I need help.


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    Quote Originally Posted by Brent 930
    If you need any help matching a turbo to your motor let me know. By the way something else I figured out is just because the cold side of an inducer is larger doesn't mean it flows more air. There is a ratio between the inducer and exducer that will dictate both the flow and at what pressure level it's most efficient at while affecting the spool some but not nearly as much as the hot side. This ratio also changes the flow and spool rate on the turbine side. It can get complex but is fun as hell to learn about.
    Thanks, but no help needed here. I've already got my future turbo picked out.... Garrett GT2871R with a 0.64 A/R turbine housing. Decent spool and I've seen one put out 370rwhp at 18 psi. Should be enough for me.

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    Now that we have stickies going on which are super cool. I would like a thread for just a compressor map for each different turbo. Here there is only maps for the GT30R & GT35R. I am wondering how much more a Garrett T62 or T66 would flow compared to the GT35R. I need to make a choice for a new turbo & I like the GT35R...however I want something different & that possibly flows a little more. I would like to know if Turbonetics makes T3-style turbos & how they compare. They are also great turbos.

    Besides, I think it would be very beneficial to everyone.
    Where have I been? Astral projecting.

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    Here is a Garrett T66
    You can get it with a T3 .96 turbine housing I believe. I like the look of this.

    Where have I been? Astral projecting.

    Quote Originally Posted by jszy25 View Post
    Get drunk with Mike Radowski they said, it'll be fun they said...A broken toe, the worst hangover known to man, and bite marks in my arm said otherwise

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    T66's are a nice high HP turbo. They are used alot on smaller engines running really high boost as you can tell from the way the islands just keep going up and up wrt pressure ratio.

    I really wish there were turbine wheel maps, as it'd tell you if a T3 or a T04 wheel is a better speed match for that thing. At the very least you'd want a Stage5 T3 wheel in probably a 0.82 A/R housing. That'd be a pretty mean street turbo. You'd probably make more top end with a T04 housing slightly bigger and a T04 wheel though.

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    Quote Originally Posted by Def
    T66's are a nice high HP turbo. They are used alot on smaller engines running really high boost as you can tell from the way the islands just keep going up and up wrt pressure ratio.

    I really wish there were turbine wheel maps, as it'd tell you if a T3 or a T04 wheel is a better speed match for that thing. At the very least you'd want a Stage5 T3 wheel in probably a 0.82 A/R housing. That'd be a pretty mean street turbo. You'd probably make more top end with a T04 housing slightly bigger and a T04 wheel though.
    Thanks for answering. How does the T66 Turbonetics compare to the T66 Garrett? I see that Garrett is offered with a .84 T3 or .96 T3 turbine housing. I don't know about the wheel. I could contact them & see if I can order it with a Stage V wheel. So with that setup do you think there will be a lot of lag? Do you think that I could get it to spool full boost by 3500rpms? I can live with up to 3700rpm spool if I can get some killer top-end power. What do you think would be the best turbo for my application? I am about to buy one since my car is under the knife right now.
    Where have I been? Astral projecting.

    Quote Originally Posted by jszy25 View Post
    Get drunk with Mike Radowski they said, it'll be fun they said...A broken toe, the worst hangover known to man, and bite marks in my arm said otherwise

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    How much power do you want and what are the specs on your engine?


    The thing with spool is it's really hard to get a good handle until you see a bunch of similar engines with similar turbos then you can kinda "guesstimate." I think you could probably make around 600rwhp and still spool by around 3.5k RPM in 4th on a 3.2L engine. I know I've seen a 3.0L Supra running an SP67 that spooled around 4300 RPM I think and could make a bit over 700rwhp. So more displacement will spool up a turbo a bit faster. I don't think an SP67 would be for you though.


    I do really like the GT35R for engines about that big if it fits your intended usage and power requirements. You're using a GT30R now right? What A/R?

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    Quote Originally Posted by Def
    How much power do you want and what are the specs on your engine?


    The thing with spool is it's really hard to get a good handle until you see a bunch of similar engines with similar turbos then you can kinda "guesstimate." I think you could probably make around 600rwhp and still spool by around 3.5k RPM in 4th on a 3.2L engine. I know I've seen a 3.0L Supra running an SP67 that spooled around 4300 RPM I think and could make a bit over 700rwhp. So more displacement will spool up a turbo a bit faster. I don't think an SP67 would be for you though.


    I do really like the GT35R for engines about that big if it fits your intended usage and power requirements. You're using a GT30R now right? What A/R?
    Oh yeah...we've talked about my tiny little baby GT30R. It has .82 A/R. Anyway...I have decided on the GT35R now. I can achieve 600rwhp with that & hope to be at 3500 full boost in 4th gear. I might go with a 1.02 A/R...1.06 might add too much lag. But over the 1.~ will free up exhaust flow.

    Specs:
    Around 8.8:1CR
    3.2L engine
    Head ported
    dual valve springs
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    5-angle valve job
    3" DP all the way through to one Magnaflow
    working on custom large intake manifold with giant TB
    Where have I been? Astral projecting.

    Quote Originally Posted by jszy25 View Post
    Get drunk with Mike Radowski they said, it'll be fun they said...A broken toe, the worst hangover known to man, and bite marks in my arm said otherwise

  17. #42
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    A GT35R should get you close to your goals. If this is primarily a street car, I'd stick with the 0.82 A/R. Almost 600rwhp has been pushed through that .82 housing on little 2.0L engines, so I think you should be fine there, although it will be a restriction. If you really want to drag, go with the big A/R and realize you'll probably have an extra few hundred RPM to wait for spool if not even more.

    What about an M50 manifold? I would think it could flow quite a bit of power. The runners are long, but they are as large as you can feasibly make them with the head ports. Maybe a larger TB has some ponies, but try to port match the plenum.

    You might also look into going with a 3.25-3.5" exhaust, as I hear Supra guys around that power level have seen some decent gains when going to an even bigger exhaust size. Not a requirement, but gives you something to tinker with.

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    Quote Originally Posted by Def
    A GT35R should get you close to your goals. If this is primarily a street car, I'd stick with the 0.82 A/R. Almost 600rwhp has been pushed through that .82 housing on little 2.0L engines, so I think you should be fine there, although it will be a restriction. If you really want to drag, go with the big A/R and realize you'll probably have an extra few hundred RPM to wait for spool if not even more.

    What about an M50 manifold? I would think it could flow quite a bit of power. The runners are long, but they are as large as you can feasibly make them with the head ports. Maybe a larger TB has some ponies, but try to port match the plenum.

    You might also look into going with a 3.25-3.5" exhaust, as I hear Supra guys around that power level have seen some decent gains when going to an even bigger exhaust size. Not a requirement, but gives you something to tinker with.
    It is definitely a street car. I will drag it eventually just to see what kind of trap speed it will get though. So you think the .82 will suffice huh? That would be great news for lag time. One of the main things I love about my car now is full boost by 3K. So 3500 would be a big jump but closer to 4K won't work.

    I will go with the M50 manifold if I can't get my custom one finished soon. The guy hasn't returned my e-mails(not my tuner, different guy from this board) so I might have been scammed out of $500 deposit & a TB . If my car is about to be done soon, then I will snatch up an M50 manifold & throw that sucker on there.

    I agree with you on the exhaust. It might help. I'll just keep what I currently have for now until I have more money to do stuff that doesn't really have to be done this instant.

    Thanks for your help.
    Where have I been? Astral projecting.

    Quote Originally Posted by jszy25 View Post
    Get drunk with Mike Radowski they said, it'll be fun they said...A broken toe, the worst hangover known to man, and bite marks in my arm said otherwise

  19. #44
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    I think the 0.82 housing is the optimal one for your intended usage. People with little four bangers have pushed loads of power out of the housing, so it's doable to make near 600rwhp with it.

    I'd be surprised if the GT35R spooled more than just a few hundred RPM slower than a GT30R. We're not talking about a huge step up in wheel sizes... So I'd imagine it'll feel about the same on spoolup and keep pulling way after the GT30R gives up the ghost.

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    Quote Originally Posted by Def
    I think the 0.82 housing is the optimal one for your intended usage. People with little four bangers have pushed loads of power out of the housing, so it's doable to make near 600rwhp with it.

    I'd be surprised if the GT35R spooled more than just a few hundred RPM slower than a GT30R. We're not talking about a huge step up in wheel sizes... So I'd imagine it'll feel about the same on spoolup and keep pulling way after the GT30R gives up the ghost.
    You are a very knowledgable man!! I use the 35r as choice on turbo over many turbo's. I have a built motor (turbo) very extensive cylinder flow with 1.5 mm oversize valves. The compression is about 8.2.1, I use the 35r 1.06 housing and have made numerous run's over 600+whp. Im using on many street car build's the 35r with a .82 housing and find it to be a great turbo all around. I have a friend with an evo 8 and a built motor with a 35r .63 housing @ 35psi makes 667whp from 5-9k rpm. Please give me your thoughts.
    Last edited by ICS Performance; 11-21-2004 at 10:15 AM.

  21. #46
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    Quote Originally Posted by IMPORTEDCARS
    You are a very knowledgable man!! I use the 35r as choice on turbo over many turbo's. I have a built motor (turbo) very extensive cylinder flow with 1.5 mm oversize valves. The compression is about 8.2.1, I use the 35r 1.06 housing and have made numerous run's over 600+whp. Im using on many street car build's the 35r with a .82 housing and find it to be a great turbo all around. I have a friend with an evo 8 and a built motor with a 35r .63 housing @ 35psi makes 667whp from 5-9k rpm. Please give me your thoughts.
    hah - I just read everything I can get my hands on and have a thing for remembering numbers. I wish I had the $$$ to actually do half the things I'd like to with turbos!

    That EVO8 sounds pretty extreme - can you post up the dyno? I didn't know 4G63's were happy revving to 9k RPM. I know SR's really don't like that without some extensive valvetrain work, and even ~8.3k RPM requires things like solid lifters.

    That's a load of power out of the .63 A/R housing though - the most I've ever seen. Bigger wheels really do let the housings flow though without "biting" into the exhaust so much and causing a big restriction.


    I think this just proves how good the GT35R is though - it's an excellent speed match when looking at the major diameters of both wheels, and it's got really really fat efficiency islands on the compressor side. Reminds me of an updated T3/T04E 50 trim...

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    At what RPM would you guys expect a .63 GT35R to hit full boost? What kind of power do you think it would make at 25 PSI?


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    Quote Originally Posted by ParadigmGuy
    At what RPM would you guys expect a .63 GT35R to hit full boost? What kind of power do you think it would make at 25 PSI?
    Well on a .82 housing in 3rd or fourth I see full boost by 2900-3200 depending on load, the .63 wppild make quicker boost but, I havent tried ut.

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    Quote Originally Posted by IMPORTEDCARS
    Well on a .82 housing in 3rd or fourth I see full boost by 2900-3200 depending on load, the .63 wppild make quicker boost but, I havent tried ut.
    Power output estimations with .82 and .63?


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    Hey, I've seen a few people try to load up compressor map graphs of different Garrett turbos... did you guys know you can download Garretts catalog via PDF? It has every single turbo in it from a GT12 to a GT60, including all of the Ball Bearing 'R' series. Here's the link:

    http://www.turbobygarrett.com/turbob.../downloads.jsp
    Just go to this page and click on the Catalog picture, it'll open a new browser in Adobe Acrobat Reader.

    Also, I made a new spreadsheet based on Def's - it has a second table for calculating LBS/Min increases based on spool-up. You DO need to use a compressor map to make it work, or it's pointless. I'll attach it - I only did it in a couple hours so take it with a grain a salt!

    Oops.. I gotta change the format, coming up!

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