Just spent an hour reading the post from Liam. Anyone care to explain to me in simplified terms
09-25-2003, 11:41 PM
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Just spent an hour reading the post from Liam. Anyone care to explain to me in simplified terms
What the hell was explained in those charts. I understand VE, and that is about it.
What is a MAP?
Sorry for all the boot *** n00b questions...
What is a MAP?
Sorry for all the boot *** n00b questions...
09-26-2003, 05:48 AM
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ok here goes....
MAP = Manifold Absolute Pressure sensor. Measures the pressure inside your intake.
Basically the charts are compressor maps. By doing out some equations (check out my link in that post to the WRX forum), you can see if your turbo is efficiently operating where you want it to...that is a REALLY REALLY short version
Basically the charts are compressor maps. By doing out some equations (check out my link in that post to the WRX forum), you can see if your turbo is efficiently operating where you want it to...that is a REALLY REALLY short version
09-26-2003, 08:12 AM
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Here is a bit of info;
The (PR) Pressure Ratio is the ratio of absolute outlet pressure divided by the absolute inlet pressure. The formula to determine this ratio is
detailed in those posts. You want to know this ratio as that is one of the functions that determines how much air you are going to ask the turbo to pass. The amount of air the turbo must deliver helps determine the appropriate sizing of the turbo.
You want to know the corrected airflow (corrected mass of air which takes into account the temperature and density of the air, i.e., temp and relative pressure) of the engine as this helps determine the flow the turbo is expected to make.
The maps that were posted are 'Efficiency Contours'. The efficiency contours show the regional efficiency of the compressor set. The efficiency is basically the percentage of turbo shaft power that converts to actual air compression.
When you select a turbo you want to select one that maintains the demand in the high efficiency range on its map.
The points that were plotted on the maps are located by calculating the PR and the air mass the engine will demand at rpm. The results of these calculations are located on the compressor map for the selected turbo. If the plotted points hit in within the efficiency range you are good to go. If not a different "size" turbo should be selected.
Quotes lifted from Garrett ..
"The surge region, located on the left-hand side of the compressor map, is an area of flow instability typically caused by compressor inducer stall. The turbo should be sized so that the engine does not operate in the surge range. When turbochargers operate in surge for long periods of time, bearing failures may occur.
The choke line is on the right hand side of the compressor map and represents the flow limit. When a turbocharger is run deep into choke, turbo speeds will increase dramatically while compressor efficiency will plunge (very high compressor outlet temps), and turbo durability will be compromised."
What they don't add is that the high temperatures will contribute to detonation and will have a dramatic impact on engine life along with turbo life.
Some folks clip the turbine to decrease the flow restriction on the exhaust and to 'slow' the shaft at rpm (less blade for the exhaust gas to press against .. or more gas escaping without pressing on a blade depending on how you want to look at it). The trade off is a few hundred rpm increase in spool up speed .. less efficiency. Here is what Garrett says about clipping
" Clipped Turbine Wheels
When an angle is machined on the turbine wheel exducer (outlet side), the wheel is said to be `clipped'. Clipping causes a minor increase in the wheel's flow capability, however, it dramatically lowers the turbo efficiency. This reduction causes the turbo to come up on boost at a later engine speed (increased turbo lag). High performance applications should never use a clipped turbine wheel. All Garrett GT turbos use modern unclipped turbine wheels."
detailed in those posts. You want to know this ratio as that is one of the functions that determines how much air you are going to ask the turbo to pass. The amount of air the turbo must deliver helps determine the appropriate sizing of the turbo.
You want to know the corrected airflow (corrected mass of air which takes into account the temperature and density of the air, i.e., temp and relative pressure) of the engine as this helps determine the flow the turbo is expected to make.
The maps that were posted are 'Efficiency Contours'. The efficiency contours show the regional efficiency of the compressor set. The efficiency is basically the percentage of turbo shaft power that converts to actual air compression.
When you select a turbo you want to select one that maintains the demand in the high efficiency range on its map.
The points that were plotted on the maps are located by calculating the PR and the air mass the engine will demand at rpm. The results of these calculations are located on the compressor map for the selected turbo. If the plotted points hit in within the efficiency range you are good to go. If not a different "size" turbo should be selected.
Quotes lifted from Garrett ..
"The surge region, located on the left-hand side of the compressor map, is an area of flow instability typically caused by compressor inducer stall. The turbo should be sized so that the engine does not operate in the surge range. When turbochargers operate in surge for long periods of time, bearing failures may occur.
The choke line is on the right hand side of the compressor map and represents the flow limit. When a turbocharger is run deep into choke, turbo speeds will increase dramatically while compressor efficiency will plunge (very high compressor outlet temps), and turbo durability will be compromised."
What they don't add is that the high temperatures will contribute to detonation and will have a dramatic impact on engine life along with turbo life.
Some folks clip the turbine to decrease the flow restriction on the exhaust and to 'slow' the shaft at rpm (less blade for the exhaust gas to press against .. or more gas escaping without pressing on a blade depending on how you want to look at it). The trade off is a few hundred rpm increase in spool up speed .. less efficiency. Here is what Garrett says about clipping
" Clipped Turbine Wheels
When an angle is machined on the turbine wheel exducer (outlet side), the wheel is said to be `clipped'. Clipping causes a minor increase in the wheel's flow capability, however, it dramatically lowers the turbo efficiency. This reduction causes the turbo to come up on boost at a later engine speed (increased turbo lag). High performance applications should never use a clipped turbine wheel. All Garrett GT turbos use modern unclipped turbine wheels."
09-26-2003, 10:46 AM
#4
adding a link to the previous post, this series of discussions will be a great reference later.
<ul><li><a href="https://forums.audiworld.com/performance/msgs/57103.phtml">to liam's post</a></li></ul>
09-26-2003, 03:03 PM
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When you are back in town...
I'll let you borrow a book with all the details.
You should see a K03 compressor map and how far past the choke limit a standard chip runs. Not optimal by any means..just a big heat pump.
Unfortunately our cars seem to deal with it using complex engine management, but that doesn't mean the car is going to run well. You end up with an engine full of carbon from the detonation and resultant timing pull and fuel dumpage in the software.
-Brent
You should see a K03 compressor map and how far past the choke limit a standard chip runs. Not optimal by any means..just a big heat pump.
Unfortunately our cars seem to deal with it using complex engine management, but that doesn't mean the car is going to run well. You end up with an engine full of carbon from the detonation and resultant timing pull and fuel dumpage in the software.
-Brent
09-26-2003, 05:39 PM
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sweet Brent... another question
I read this last night in a quote from ADAM H discussing the GT-25 vs T-28:
at 19psi your 1.8l engine would be operating at 78% compressor efficiency...and at 50% rpm is far enough away from the surge line to not be an issue...
compare that with the crappy t28 that would be running in the 65% or lower compressor efficiency range...and you just netted yourself 13% increase in compressor efficiency at the same boost level......
If this is true wouldn't picking up the GT-25 instead of the T-28 make more sense because of it's increased efficiency at the same psi?
or did I miss something completely?
here is the thread so you don't have to looking around for it.<ul><li><a href="https://forums.audiworld.com/performance/msgs/57187.phtml">link</a></li></ul>
at 19psi your 1.8l engine would be operating at 78% compressor efficiency...and at 50% rpm is far enough away from the surge line to not be an issue...
compare that with the crappy t28 that would be running in the 65% or lower compressor efficiency range...and you just netted yourself 13% increase in compressor efficiency at the same boost level......
If this is true wouldn't picking up the GT-25 instead of the T-28 make more sense because of it's increased efficiency at the same psi?
or did I miss something completely?
here is the thread so you don't have to looking around for it.<ul><li><a href="https://forums.audiworld.com/performance/msgs/57187.phtml">link</a></li></ul>
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09-30-2003, 10:08 PM
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half of it turned into petty arguement crap... but take these points from it...
where people were comparing 2 different objectives in this not real medium of arguement....
Take from this... different cars get tuned to different levels with different end goals in mind... and we can compare them all day, and argue this or that... but ALL MODDING is a compromise in an attempt to attain a specific goal...
audi tuners tend to go for overall smooth, linear power with increased driveability. Is it the highest possible horsepower? nope. Is it easier to drive to work everyday? heck yeah. I remember a car review in european car or something years ago... an E30 with a huge forced induction setup.... the author said it was the SCARIEST car he had ever driven, becuase it was quite slow... until about 4800rpm, when the car would nail you to the seat with a force that he had never seen. He said you would have to mentally prepare for the gear shift before the boost hit or you would bounce the rev limiter. Fast? Yup. High peak power? hellz yeah. driveable? Nope. that is one end of the spectrum. The APR kit is linear, easy to drive, and a very nice compromise. I prefer teh kick of the T28... more like that e30, but still driveable.
The whole deal with compressor maps? Good info to know, I would suggest buying a book or 2 and getting the basics from a non automotive forum (less biased to a degree). I enjoyed the corky bell book, even though people don't always agree with him, it is good to know. <A HREF="http://www.amazon.com/exec/obidos/tg/detail/-/0837601606/qid=1064988354/sr=8-1/ref=sr_8_1/103-5781175-4949454?v=glance&s=books&n=507846">find the book here at amazon</A>.... it was an interesting read.
there were also tidbits in that thread about the average disposable income levels of owners of cars of different vintages, target markets, and original inflation adjusted dollars. yeah....
Nothing AMAZINGLY new in the thread IMHO.
Take from this... different cars get tuned to different levels with different end goals in mind... and we can compare them all day, and argue this or that... but ALL MODDING is a compromise in an attempt to attain a specific goal...
audi tuners tend to go for overall smooth, linear power with increased driveability. Is it the highest possible horsepower? nope. Is it easier to drive to work everyday? heck yeah. I remember a car review in european car or something years ago... an E30 with a huge forced induction setup.... the author said it was the SCARIEST car he had ever driven, becuase it was quite slow... until about 4800rpm, when the car would nail you to the seat with a force that he had never seen. He said you would have to mentally prepare for the gear shift before the boost hit or you would bounce the rev limiter. Fast? Yup. High peak power? hellz yeah. driveable? Nope. that is one end of the spectrum. The APR kit is linear, easy to drive, and a very nice compromise. I prefer teh kick of the T28... more like that e30, but still driveable.
The whole deal with compressor maps? Good info to know, I would suggest buying a book or 2 and getting the basics from a non automotive forum (less biased to a degree). I enjoyed the corky bell book, even though people don't always agree with him, it is good to know. <A HREF="http://www.amazon.com/exec/obidos/tg/detail/-/0837601606/qid=1064988354/sr=8-1/ref=sr_8_1/103-5781175-4949454?v=glance&s=books&n=507846">find the book here at amazon</A>.... it was an interesting read.
there were also tidbits in that thread about the average disposable income levels of owners of cars of different vintages, target markets, and original inflation adjusted dollars. yeah....
Nothing AMAZINGLY new in the thread IMHO.
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