CFM Calculations
11-07-2006, 03:14 PM
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Originally Posted by JETPILOT
I double checked my calculations. I still get this....
My lb/min calculations are 33.7 lbs/min @ 15psi @ 6600rpm with a pressure ratio of 2.0
I calculated 80%.... so my calculations are in the ballpark of yours.
JET
My lb/min calculations are 33.7 lbs/min @ 15psi @ 6600rpm with a pressure ratio of 2.0
I calculated 80%.... so my calculations are in the ballpark of yours.
JET
11-07-2006, 03:18 PM
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Originally Posted by atlsupdawg#2
Cool, I added a bit to the efficiency because you're running a turbo which bumps that percentage up anyway compared to N/A..
11-07-2006, 03:22 PM
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Originally Posted by JETPILOT
OK.... I see we are in the 42 lb/min range now. 
JET
JET
11-07-2006, 03:26 PM
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Originally Posted by JETPILOT
You.... are a pimp!!!! All this and your probably still not yet at full brain calculating capacity seeing that pic of you in the car in Vegas!!! I wish you well in your journey to recovery.
JET
JET
11-07-2006, 03:26 PM
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Originally Posted by MIAPLAYA
Exactly and keep in mind both that boost is being added so the CFM output will increase AND think about it this way. On most compressor maps with a 100% Ve motor you can calculate CHP worth of air by multiplying the Mass flow by 10. So if you are saying its 33 lb/min you are telling me at 15 PSI and 6600 rpms the turbo is only producing 330 HP worth of air. Which is WAY low.
Good thread!!!
Last edited by atlsupdawg#2; 11-07-2006 at 03:29 PM.
11-07-2006, 03:40 PM
#33
Well let me try and explain surging with a wastegate. To small of a waste gate on a large turbo at low psi will cause boost spikes ( what i call surging correct me if i am wrong). This is why you need a larger gate on a turbo like this. If you are in the 10psi range with a 38mm gate it will spike, if you go up too say 20psi or so with the same turbo the same 38mm gate can controll it without it spiking. Its kind of wierd how it works but that as much i can get out of the research i have done on it.
The hx40 flows around 49-55 lb/min
The hx40 flows around 49-55 lb/min
11-07-2006, 03:48 PM
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Originally Posted by rocks
Well let me try and explain surging with a wastegate. To small of a waste gate on a large turbo at low psi will cause boost spikes ( what i call surging correct me if i am wrong). This is why you need a larger gate on a turbo like this. If you are in the 10psi range with a 38mm gate it will spike, if you go up too say 20psi or so with the same turbo the same 38mm gate can controll it without it spiking. Its kind of wierd how it works but that as much i can get out of the research i have done on it.
The hx40 flows around 49-55 lb/min
The hx40 flows around 49-55 lb/min
11-07-2006, 03:53 PM
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As an aside I don't think the compressor is as much the culprit for him as the turbine is. I'm sure the 60-1 or 62-1 for that matter will flow more then enough for his power needs. The key is finding a turbine size, trim, and housing A/R that will be capable of flowing the amount of CFM being produced while still mainting a decent boost threshold (spool up time). Hence my suggestion for a T4 P Trim turbine wheel. I just don't know what size A/R would work best. No one will without dyno time to be honest. I guess he could go with a 62-1 compressor (fits into a 60-1 housing with ease) and a T4 P trim turbine and just get three different A/Rs. it comes with a .68, .81, and .96 as standard sizes. i would give those a shot if it must be done immediately.. Of course moving to a T4 will require some pipe changes to be mad. Different inlet flange for sure...You could even get the turbine housings with a v band discharge and just make the downpipe a v band flange and it would be easier to switch between them...
Last edited by MIAPLAYA; 11-07-2006 at 03:56 PM.
11-07-2006, 04:26 PM
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Originally Posted by rocks
Well let me try and explain surging with a wastegate. To small of a waste gate on a large turbo at low psi will cause boost spikes ( what i call surging correct me if i am wrong). This is why you need a larger gate on a turbo like this. If you are in the 10psi range with a 38mm gate it will spike, if you go up too say 20psi or so with the same turbo the same 38mm gate can controll it without it spiking. Its kind of wierd how it works but that as much i can get out of the research i have done on it.
The first is the size of the turbo and it's ability to produce max boost rather low in the rpm range. As boost is increased so is exhaust pressure, sometimes 3 times as much. This can prevent the wastegate valve from fully opening thus you run into boost spikes. This is very common on engines where the intake efficiency is far greater than the exhaust.
The second occurs when boost is so high that when the wastegate valve does open it's held there, or rather floats, bleeding off and not able to hold the preset limit. I saw/read about a lot of Supra guys running into this problem when they pushed the 30+ psi mark. The exhaust pressure and flow rate were so high that the spring simply couldn't modulate the valve efficiently to control boost.
Surging simply put is, the motor can not injest the mass flow the turbo is producing at that given RPM. This is where volumetric efficiency comes into play.
11-07-2006, 06:19 PM
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Originally Posted by atlsupdawg#2
There are 2 inherent problems with improper wastegate selection, aside from size and location.
The first is the size of the turbo and it's ability to produce max boost rather low in the rpm range. As boost is increased so is exhaust pressure, sometimes 3 times as much. This can prevent the wastegate valve from fully opening thus you run into boost spikes. This is very common on engines where the intake efficiency is far greater than the exhaust.
The second occurs when boost is so high that when the wastegate valve does open it's held there, or rather floats, bleeding off and not able to hold the preset limit. I saw/read about a lot of Supra guys running into this problem when they pushed the 30+ psi mark. The exhaust pressure and flow rate were so high that the spring simply couldn't modulate the valve efficiently to control boost.
Surging simply put is, the motor can not injest the mass flow the turbo is producing at that given RPM. This is where volumetric efficiency comes into play.
The first is the size of the turbo and it's ability to produce max boost rather low in the rpm range. As boost is increased so is exhaust pressure, sometimes 3 times as much. This can prevent the wastegate valve from fully opening thus you run into boost spikes. This is very common on engines where the intake efficiency is far greater than the exhaust.
The second occurs when boost is so high that when the wastegate valve does open it's held there, or rather floats, bleeding off and not able to hold the preset limit. I saw/read about a lot of Supra guys running into this problem when they pushed the 30+ psi mark. The exhaust pressure and flow rate were so high that the spring simply couldn't modulate the valve efficiently to control boost.
Surging simply put is, the motor can not injest the mass flow the turbo is producing at that given RPM. This is where volumetric efficiency comes into play.
Will the GT-K bolt up to the piping installed now?
11-07-2006, 07:08 PM
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http://www.turbobygarrett.com/turbob...o_tech103.html
This is very well written and when done right comes out with very usable numbers, although you might already be using it.
This is very well written and when done right comes out with very usable numbers, although you might already be using it.