Compressor Surge
03-03-2006, 07:47 PM
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Compressor Surge
When using a blow off Valve do I have to worry as much about compressor surge? If one of my calculated points falls to the left of the surge limit line when plotted on a compressor map will this be a big problem. I'm having trouble determining what compressor trim (50,54,57,60) will be best suited for my 99 Teg LS. Some help. Thanx.
03-03-2006, 08:56 PM
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Re: Compressor Surge (StephenSadowski)
First of all your hp goals would be required so that you can determine what pr you would be running at, or what pr's do you intend to run? This will tell you (or more importantly us, because you are asking for our opinions) how efficient the compressor will be @ a given flow and pressure ratio.
So what are your hp goals, is it a street car, strip car? This will give a better idea of the type of response that you are looking for as well as what turbo will be one of your better overall choices......that being said:
The cookie cutter t3/to4e 50, 54, 57, 60 trims are what many many people are using on thier lst's, b16's and gsr's and d-series engines. They seem to be a very practical turbo for the 250-400whp range. If I were you I'd go with the 50 or 60 trim. Remember the larger the trim the higher the boost threshold (more "lag") and these also come in two main turbine housing choices, you have the .48 a/r and the .63 a/r. Many opt for the .63 a/r as it is more efficient @ higher flows and allows for a bit more traction as it takes a bit longer to spool (though it would be better to choose not based on traction, but what you will be requiring of the turbo). From what I have noticed from the comp map the 50 trim goes to ~48lbs/min, the 54 trim to ~45lbs/min, the 57 to ~42lbs/min and the 60 to ~50lbs/min. These values are of course the assuming that you would be maxing out the compressor. Now I am NO turbo guru so don't take my words as the law, but when I get a chance I will do the simple plot (cause of course that's all I know how to do
) of your ls on the 50 and 60 trim maps. I will assume you will be revvin' into the low 7k range, but your hp goals are needed to determine what boost levels you will be running (for me to figure it out anyway). Hope that helped a little bit. I know I tend to write a lot and probably messed up most of what I was trying to convey from my menial understanding of the subject.
So what are your hp goals, is it a street car, strip car? This will give a better idea of the type of response that you are looking for as well as what turbo will be one of your better overall choices......that being said:
The cookie cutter t3/to4e 50, 54, 57, 60 trims are what many many people are using on thier lst's, b16's and gsr's and d-series engines. They seem to be a very practical turbo for the 250-400whp range. If I were you I'd go with the 50 or 60 trim. Remember the larger the trim the higher the boost threshold (more "lag") and these also come in two main turbine housing choices, you have the .48 a/r and the .63 a/r. Many opt for the .63 a/r as it is more efficient @ higher flows and allows for a bit more traction as it takes a bit longer to spool (though it would be better to choose not based on traction, but what you will be requiring of the turbo). From what I have noticed from the comp map the 50 trim goes to ~48lbs/min, the 54 trim to ~45lbs/min, the 57 to ~42lbs/min and the 60 to ~50lbs/min. These values are of course the assuming that you would be maxing out the compressor. Now I am NO turbo guru so don't take my words as the law, but when I get a chance I will do the simple plot (cause of course that's all I know how to do
) of your ls on the 50 and 60 trim maps. I will assume you will be revvin' into the low 7k range, but your hp goals are needed to determine what boost levels you will be running (for me to figure it out anyway). Hope that helped a little bit. I know I tend to write a lot and probably messed up most of what I was trying to convey from my menial understanding of the subject.
03-04-2006, 05:37 AM
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Re: Compressor Surge (KeyserSoze)
Thanxs for your help...Sorry I didin't include more info before so here goes. I'm looking to make a minimum of 200hp per liter at the wheels which is about 360hp and keep it my daily driver. And yes the T3/T04E .63a/r turbo with a stage 3 (76 Trim?) turbine is what I was looking at. I've been doing my own calculations over here with variouse boost numbers (8psi - 20psi) and am still falling to the left of the surge line at lower rpm (~3500). Is this rpm point on the compressor map too low. I'de like boost to hit around then...I think? In addition, perhaps you could clarify the proper figures in the calculation for me. I got the calculation off a post here a year ago or so.
cid X rpm X 0.5 X VE% <U></U> = CFM (no boost)
1728
CFM X PR = CFM under boost
cid - (cubic inches disp.) 1.834Liter (B18B1) X 61 = 112cid
Volumetric Efficiency - I've been using 90% (too much ,too little ?)
Now to convert CFM to lbs/min at sea level I was told to multiply CFM by the factor of 0.070318
Do you have anything different here that I should reconsider using?
When comparing maps of the 50 and 60 Trims the PR threshold of the 60 Trim appears to be ~2.85 where as the 50 Trim peaks at 3.4. Considering that both compressors can handle max flow between 48-50 lbs/min does the 50 Trim have the ability to handle more boost? Or am I way off?
And going back to my original post, will having a BOV reduce the affect of compressor surge to a minimum.? Thanx.
cid X rpm X 0.5 X VE% <U></U> = CFM (no boost)
1728
CFM X PR = CFM under boost
cid - (cubic inches disp.) 1.834Liter (B18B1) X 61 = 112cid
Volumetric Efficiency - I've been using 90% (too much ,too little ?)
Now to convert CFM to lbs/min at sea level I was told to multiply CFM by the factor of 0.070318
Do you have anything different here that I should reconsider using?
When comparing maps of the 50 and 60 Trims the PR threshold of the 60 Trim appears to be ~2.85 where as the 50 Trim peaks at 3.4. Considering that both compressors can handle max flow between 48-50 lbs/min does the 50 Trim have the ability to handle more boost? Or am I way off?
And going back to my original post, will having a BOV reduce the affect of compressor surge to a minimum.? Thanx.
03-04-2006, 06:23 PM
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Re: Compressor Surge (TheShodan)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by StephenSadowski »</TD></TR><TR><TD CLASS="quote">When comparing maps of the 50 and 60 Trims the PR threshold of the 60 Trim appears to be ~2.85 where as the 50 Trim peaks at 3.4. Considering that both compressors can handle max flow between 48-50 lbs/min does the 50 Trim have the ability to handle more boost? Or am I way off?
And going back to my original post, will having a BOV reduce the affect of compressor surge to a minimum.? Thanx. </TD></TR></TABLE>
Well, from what I understand the reason the 60 trim flows the same (and actually a bit higher) as the 50 trim @ a lower pressure ratio is because it is a more efficient wheel so it takes less boost to acheive relatively the same flow.
As for the Ev of 90%, that is what I would guesstimate for an ls engine as well. And I have actually heard mixed reviews about running a bov and not running one. I have yet to make up my mind as to whether one is needed or not, but I will be running one anyway until I get the time to actually read some empirical data that supports one side or the other. Better safe than sorry.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TheShodan »</TD></TR><TR><TD CLASS="quote">Hmmmm.......Interesting.</TD></TR></TABLE>
Cmon' Mac, don't tease us with vague statements.......
If we (or more than likely me) are confused then educate us nubz a bit will ya?
And going back to my original post, will having a BOV reduce the affect of compressor surge to a minimum.? Thanx. </TD></TR></TABLE>
Well, from what I understand the reason the 60 trim flows the same (and actually a bit higher) as the 50 trim @ a lower pressure ratio is because it is a more efficient wheel so it takes less boost to acheive relatively the same flow.
As for the Ev of 90%, that is what I would guesstimate for an ls engine as well. And I have actually heard mixed reviews about running a bov and not running one. I have yet to make up my mind as to whether one is needed or not, but I will be running one anyway until I get the time to actually read some empirical data that supports one side or the other. Better safe than sorry.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TheShodan »</TD></TR><TR><TD CLASS="quote">Hmmmm.......Interesting.</TD></TR></TABLE>
Cmon' Mac, don't tease us with vague statements.......
If we (or more than likely me) are confused then educate us nubz a bit will ya?
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