How to read compressor maps

[AWDxBOOST]

^ good stuff right there!

 

glad to see people chiming in with nice info

[2005garnetGT]

yeah, I was thinking of injectors.

 

but still, look at a green's dyno chart, they make ~400whp at 6500rpms.

 

heres an example on an 04 sti.

 

http://i138.photobucket.com/albums/q241/CarQz17/dynograph.jpg

 

It's pessimistic because its for target boost at redline. In practice, we would expect full boost by what? 4000 rpm? So if we substitute 4000 rpm in place of the 6500, you can see we would only need 30.7 lb/min.

 

Edit: you say lb/hr... I believe it's lb/min.

[Underdog]

Thank you AWDxBOOST for putting this thread together!

 

Below are the AVO380 and 450 compressor maps (420 excluded since its the same compressor as the 380 with a different housing & A/R). As you can see both turbos are capable of producing the desired boost/flow at >70% efficiency (good job AVO folks!). Now, deciding between the 380 & 420 is easy. The 380 has a lower A/R which means it is designed for a lower boost threshold and low/mid rpm grunt. The 420 has a larger A/R ratio which is better suited towards higher-rpm performance.

 

When it comes down to choosing between the 450 and the 420 is where more ambiguities pop up. To keep some constraints on this project I will specify my goals. A) I want to stay TMIC because it is a part of the Legacy's character. There is nothing that annoys me more than a non-functional hood scoop, and I don't want to swap. B) I'd rather run a larger turbo conservatively then a small one at the fringes of it's performance in order to reduce heat and vibrational stresses on the turbo, but only as long as efficiency isn't sacrificed.

 

You can see that the plot on the AVO450 is operating within 72% efficiency all the way to max load whereas the 420 efficiency falls off up at the limits. However, since I'm running a TMIC, anything over 40lb/min will probably be pushing the limits of IC efficiency. Therefore I would chose the 450 because the overall efficiency will be better. Actually, if we delayed the boost rise a bit more, we could have the compressor running at optimum efficiency throughout the bulk of the rev range but the difference would be academic.

 

2005garnetGT: I'm not all to familiar with green turbochargers so if you could point me to some compressor maps, I'd appreciate it. If it can flow 50lb/min and we have all the bolt-ons/supporting mods and an appropriate tune, I don't see why 400whp is out of the question according to my info. Also, I would need to know what the boost map looks like to see the complete picture. Remember, nothing here is gospel, it's merely a tool to be used.

[LittleBlueGT]

Thank you AWDxBOOST for putting this thread together!

 

Below are the AVO380 and 450 compressor maps (420 excluded since its the same compressor as the 380 with a different housing & A/R). As you can see both turbos are capable of producing the desired boost/flow at >70% efficiency (good job AVO folks!). Now, deciding between the 380 & 420 is easy. The 380 has a lower A/R which means it is designed for a lower boost threshold and low/mid rpm grunt. The 420 has a larger A/R ratio which is better suited towards higher-rpm performance.

 

When it comes down to choosing between the 450 and the 420 is where more ambiguities pop up. To keep some constraints on this project I will specify my goals. A) I want to stay TMIC because it is a part of the Legacy's character. There is nothing that annoys me more than a non-functional hood scoop, and I don't want to swap. B) I'd rather run a larger turbo conservatively then a small one at the fringes of it's performance in order to reduce heat and vibrational stresses on the turbo, but only as long as efficiency isn't sacrificed.

 

You can see that the plot on the AVO450 is operating within 72% efficiency all the way to max load whereas the 420 efficiency falls off up at the limits. However, since I'm running a TMIC, anything over 40lb/min will probably be pushing the limits of IC efficiency. Therefore I would chose the 450 because the overall efficiency will be better. Actually, if we delayed the boost rise a bit more, we could have the compressor running at optimum efficiency throughout the bulk of the rev range but the difference would be academic.

 

2005garnetGT: I'm not all to familiar with green turbochargers so if you could point me to some compressor maps, I'd appreciate it. If it can flow 50lb/min and we have all the bolt-ons/supporting mods and an appropriate tune, I don't see why 400whp is out of the question according to my info. Also, I would need to know what the boost map looks like to see the complete picture. Remember, nothing here is gospel, it's merely a tool to be used.

 

Bigger turbo will always be more efficient, doesn't mean you should pick it!

 

AVO420 or bigger IMO should only be used if you have a FMIC or are planning one in the future.

[Underdog]

Bigger turbo will always be more efficient, doesn't mean you should pick it!

 

AVO420 or bigger IMO should only be used if you have a FMIC or are planning one in the future.

 

 

Bigger turbo always more efficient? Hmm, I'm not sure what you're saying here. I don't think many turbos get above 80% efficiency. I don't think I indicated that you should always go with a larger turbo just that the 450 would be my choice over the 420 in the situation I had laid out. Below is an example where the turbocharger is WAY too big for our engine. This turbo will never build boost on our car. Next to it is a turbo that is still way too big but will still build boost, however it is so big that we won't see anything north of 70% efficiency until redline.

 

Right, anything more than 40lb/min will be choked by the TMIC, which is why the 450 is a better choice. Assuming the same IC efficiency (lets say 70%) the 450 will be (.72x.7= .504) and the 420 will be (.65x.7 = .455) So the 450 would be about 5% more efficient at redline (the point of concern).

[mickeyd2005]

Bigger turbo will always be more efficient, doesn't mean you should pick it!

 

I disagree with the word always. The peak efficiency on most compressors is around 77% regardless of size. The right size turbo has to be matched to the rpm that the car is driven at.

 

Underdog's charts are really good at showing that.

[AWDxBOOST]

. Below is an example where the turbocharger is WAY too big for our engine. This turbo will never build boost on our car. Next to it is a turbo that is still way too big but will still build boost, however it is so big that we won't see anything north of 70% efficiency until redline.

 

 

LOL at the 1.05 AR turbo

 

must be for a damn big rig:lol:

[Underdog]

Haha, it is a garrett gt60 turbo capable of supporting 1450-2000 HP on engine from 6.0-12.0 Liters, per the Garrett site.

 

[LittleBlueGT]

I meant a bigger turbo (relatively speaking) is more efficient.

 

If you are going with a TMIC I think almost everyone will agree that an AVO420 or 380 is by far the best choice.

 

You will end up with about the same overall hp but less spool. So you are trading spool for essentially nothing (or very little).

[mickeyd2005]

The efficiency shown on the compressor chart is how close the compressor gets to theoretical adiabatic compression. Every compressor wheel has a sweet spot regardless of size. I think you're thinking about something different when you are talking about efficiency.

 

Also, the compressor maps won't really tell the whole story about spool. For example, if the turbo had a super lightweight titanium or ceramic turbine blades with twin scroll and ball bearings, you'll get better spool but the compressor map really won't change that much. The surge line and choke line should remain the same.

[Underdog]

LBGT, this isn't a thread about me actually choosing a turbo... I have only laid out the graphs and used the AVO information because it was readily available. This is not a judgement on any of their products either, rather a way to interpret compressor maps.

 

As far as losing spool, we would need to look at the turbine maps in order to see how a turbo will spool in application. The line I plotted on the 380 and 450 graphs is the desired boost profile, but as you can see, these turbos are capable of producing a wide array of flow/pr profiles. The actual boost we see will be determined by the turbine and the boost-control management.

 

As far as my personal goals... I am no longer afraid to sacrifice a higher boost-threshold (or what you call "spool") for higher boost. The fact is, there are no viable twin-turbo or VNT options out there for the Legacy. Therefore, if you want more horsepower (more boost in the higher rpms) then you MUST sacrifice boost threshold.

 

The 450 has a larger "sweet spot" that would be where most of my daily driving actually takes place, so right off the bat we are dealing with less heat imparted to the air charge. The reason "everyone here" thinks that the 450 should only be used with FMIC is because the thought is that if you're getting a 450, you must want big numbers. If I was shooting for 24psi or much over 400cHp then I would certainly go the FMIC route.

 

Lastly, you shouldn't downplay the efficiency of the turbo. The 5% gain in efficiency will be akin to the slightly increased boost threshold, they are both small trade-offs. I could say that by going with the 380 (not even a consideration for me) you are trading efficiency for essentially nothing (or very little) because to me, if I want to drive fast/aggressive, I'll keep it in the powerband... not roll on from 1,500rpm. The rest of the time, I'll be happy with the non-boosted 2.5 for getting me to Dunkin' Donuts and back.

 

Aside: Am I the only one here who loves the feeling of a turbo spooling up? I don't understand why some people shy away from higher boost thresholds. Granted, you can take it too far where the car won't ever hit boost unless you are on the fringes of legality. But most of the time, feeling the torque as the boost builds just gives me such a rush... I wish the vf40 didn't fall on its face at the top-end!

[LittleBlueGT]

LBGT, this isn't a thread about me actually choosing a turbo... I have only laid out the graphs and used the AVO information because it was readily available. This is not a judgement on any of their products either, rather a way to interpret compressor maps.

 

As far as losing spool, we would need to look at the turbine maps in order to see how a turbo will spool in application. The line I plotted on the 380 and 450 graphs is the desired boost profile, but as you can see, these turbos are capable of producing a wide array of flow/pr profiles. The actual boost we see will be determined by the turbine and the boost-control management.

 

As far as my personal goals... I am no longer afraid to sacrifice a higher boost-threshold (or what you call "spool") for higher boost. The fact is, there are no viable twin-turbo or VNT options out there for the Legacy. Therefore, if you want more horsepower (more boost in the higher rpms) then you MUST sacrifice boost threshold.

 

The 450 has a larger "sweet spot" that would be where most of my daily driving actually takes place, so right off the bat we are dealing with less heat imparted to the air charge. The reason "everyone here" thinks that the 450 should only be used with FMIC is because the thought is that if you're getting a 450, you must want big numbers. If I was shooting for 24psi or much over 400cHp then I would certainly go the FMIC route.

 

Lastly, you shouldn't downplay the efficiency of the turbo. The 5% gain in efficiency will be akin to the slightly increased boost threshold, they are both small trade-offs. I could say that by going with the 380 (not even a consideration for me) you are trading efficiency for essentially nothing (or very little) because to me, if I want to drive fast/aggressive, I'll keep it in the powerband... not roll on from 1,500rpm. The rest of the time, I'll be happy with the non-boosted 2.5 for getting me to Dunkin' Donuts and back.

 

Aside: Am I the only one here who loves the feeling of a turbo spooling up? I don't understand why some people shy away from higher boost thresholds. Granted, you can take it too far where the car won't ever hit boost unless you are on the fringes of legality. But most of the time, feeling the torque as the boost builds just gives me such a rush... I wish the vf40 didn't fall on its face at the top-end!

 

I understand exactly what you are saying.

 

It just seems extremely odd to me that you would consider using a turbo like a 450 w/ a TMIC when the 380 is actually considered a farily efficient turbo when talking about hp in the 380-400 crankhp range.

 

It just seems like the trade-offs are not very even. In other words it does not seem like a matched system.

[Underdog]

I'm not considering using any other turbo besides the vf40 for the next ~5 years or 60k miles..

 

I wasn't saying that the 450 is the right turbo because we haven't looked at the turbine side at all. The AVO450 is a product, the compressor is merely a component. While the component may be what we are looking for (in that situation it would be) the product may not be right for our uses.

 

One last time: I'm not advocating one turbo or another for specific application. Just trying to inform people how to read the maps and to understand what the information means.

[edmundu]

....Am I the only one here who loves the feeling of a turbo spooling up? I don't understand why some people shy away from higher boost thresholds. Granted, you can take it too far where the car won't ever hit boost unless you are on the fringes of legality. But most of the time, feeling the torque as the boost builds just gives me such a rush... I wish the vf40 didn't fall on its face at the top-end!

 

..I agree!!! I love the spoolup of the Avo450, it is not the punchy feeling of a vfxx, but a build up/swell of power that doesn't letup til redline. Very, very sweet. Although not for everyone, it suits me just fine:)

[Underdog]

^ Thanks for chiming in!

 

Besides the lack of top end, the other thing I don't like about the vf40 is that "punchiness." It upsets the car's low-speed/cruising balance and makes throttle application "jerky."

 

In the words of Corky Bell: "If you have no lag, you have no turbo. You also have no huge torque increase to look forward to."

[rc0032]

I understand exactly what you are saying.

 

It just seems extremely odd to me that you would consider using a turbo like a 450 w/ a TMIC when the 380 is actually considered a farily efficient turbo when talking about hp in the 380-400 crankhp range.

 

It just seems like the trade-offs are not very even. In other words it does not seem like a matched system.

http://www.northamericanmotoring.com/forums/images/smilies/sly.gif

[Underdog]

^ Yeah, I'm confused too... I'm sure LBGT will be happy with the AVO380 w/ meth. I had absolutely no intent on undermining that. He simply has different goals for his car than I do. I mean, if I was bashing an AVO product for design, why would I "consider" another AVO product?

 

The only reason AVO was mentioned is because they are particularly helpful and informative when it comes to their product. (.pdf's)

[rc0032]

He would be happier if he gotten injectors

 

To each their own, I think he is just justifying heis purchase. A few months back he was insistent that the 420 needed a FMIC and WI was the devil.

Now get this thread back on topic…

[Underdog]

Here is my understanding of the AVO 380, 420 and 450 strictly from the .pdfs in front of me.

 

AVO380 and the AVO420 appear to share the same compressor wheel based on the compressor maps. However, the AVO420 is refered to as having "The high-flow AVO420LGT compressor housing..." which would indicate that the compressor A/R is tuned to improve high-speed flow at the expense of some low-speed response.

 

The AVO380 uses the 3-4 exhaust housing which likely has an exducer bore diameter and A/R ratio appropriate for low-speed response. The AVO420 uses the 4-5 exhaust housing which it shares with the AVO450. This exhaust housing must have a larger exducer bore diameter to accomodate the extra exhaust flow from the additional power. The A/R is also probably tuned for higher-rpm operation since that is where the highest exhaust flow energy exsists.

 

[The exducer bore is the bottleneck through which all non-wastegated exhaust gasses must flow. A bore too large will allow the gasses to escape without acting on the turbine. Conversely a bore that is too small will choke the exhaust flow. A/R ratio determines the speed and distance from centerline of the turbine that the exhaust gasses will act upon it. An A/R <1.15 will tend towards low-speed response, A/R >1.15 will be better suited for flow and power.]

 

The AVO450 uses a compressor that is more ideally suited to push the flow beyond 35 lb/min and pressure ratios greater than 2.5. If you look at the plots I had done you can see that both plots fall within a very efficient range when running the maximum boost and flow (the boost curve is determined by my excel chart and indicated on the maps by the red line). The AVO450 however has a larger peak efficiency "island" below and to the right or our maximum demand. This means that any time I'm running less than full boost, I will have a greater chance of being within the peak efficiency range of the AVO450. Also, the AVO450 does not drop below 70% efficiency when pushing it to the limits. (There is nothing less desirable than a ton of heat at maximum operating speed.... BOOOM!)

 

LBGT: If you want to, plot your expected boost curve in excel using the spreadsheet format. The formulas are simple! Then input the flow and pressure ratio points on the 380/420 compressor map and 450 compressor map. You will see why the 380 and 420 are much better than the 450 when it comes to low-speed and (relatively) low boost.

 

Edit: Please don't quote my entire posts. It's long enough having to view once.

[bosco]

enough of this my head hurts to much info to fast. btw will my soon to be AVO 380 w/v.2tmic,inj.,pump,up/dp/cbe and protune hit 300whp or not? bosco

[edmundu]

^^Yeah, it will:)

[Underdog]

Well Bosco since you asked so nicely...

 

Attached is my quick plot of what AVO tuned out of their AVO380. I merely took a snapshot of the boost map in the .pdf and dragged horizontal lines across to get the approximate boost value. Based on the conservative calculations, you should be hitting 380 chp and with an *edit: 20%* drivetrain loss that would be just north of 300 whp.

 

The green line on the compressor map indicates the efficiency of the turbo for that particular boost profile.

 

Edit: Made it a lot more accurate and simple by putting the compressor map in the background of the excel chart, the axes matched up and everything!

[bosco]

Well Bosco since you asked so nicely...

 

Attached is my quick plot of what AVO tuned out of their AVO380. I merely took a snapshot of the boost map in the .pdf and dragged horizontal lines across to get the approximate boost value. Based on the conservative calculations, you should be hitting 380 chp and with an 80% drivetrain loss that would be just north of 300 whp.

 

The green line on the compressor map indicates the efficiency of the turbo for that particular boost profile.

 

thanks thats all the power i want or really need. speed is based on cubic dollars not cubic inches and my $ are about gone. bosco

[LittleBlueGT]

I got this thread off topic, sorry.

 

What I meant before was: I understand the want for optimizing the turbo's compressor characteristics for the intended application. It just seems odd to me to base a turbo choice based almost solely on that info.

 

ie: an AVO450 with a TMIC seems like an absolute waste to me, and from Rallitek's testing you can see that. Why lose so much low end response just to optimize the turbo for the efficiency range you want when you are limited by the flow capacity of a TMIC? It is nice to have the whole package optimized to one another. Max out an IC so the turbo is running real efficient? I would rather run the turbo a little hotter (nothing crazy, nothing that will affect longevity) and have a system that as a whole is more balanced. All said and done it is about our power curve. Losing low end power to gain very little up top makes no sense to me.

 

Though I (like many people) tend to justify their purchases, that has noting to do with my replies. This time.

 

As far as plotting it out in excel, I really have no idea how to do that, never plotted anything in excel. I will have to try when I have more time on Monday.

 

I will not sidetrack this threa anymore as this is very good info.

[turbo2nr]

I got this thread off topic, sorry.

 

What I meant before was: I understand the want for optimizing the turbo's compressor characteristics for the intended application. It just seems odd to me to base a turbo choice based almost solely on that info.

 

ie: an AVO450 with a TMIC seems like an absolute waste to me, and from Rallitek's testing you can see that. Why lose so much low end response just to optimize the turbo for the efficiency range you want when you are limited by the flow capacity of a TMIC? It is nice to have the whole package optimized to one another. Max out an IC so the turbo is running real efficient? I would rather run the turbo a little hotter (nothing crazy, nothing that will affect longevity) and have a system that as a whole is more balanced. All said and done it is about our power curve. Losing low end power to gain very little up top makes no sense to me.

 

Though I (like many people) tend to justify their purchases, that has noting to do with my replies. This time.

 

As far as plotting it out in excel, I really have no idea how to do that, never plotted anything in excel. I will have to try when I have more time on Monday.

 

I will not sidetrack this threa anymore as this is very good info.

 

I have an AVO500 on my WRX with a TMIC.....ran 11.1 @126 with a little 50shot to get going:icon_wink As far as a TMIC not flowing past 400HP....ahhh.

 

 

The bigger the turbo....the less heat in the charge......the less need for a FMIC.....also way less volume to pressurize when using a FMIC, thus spool-up is about the same or even better than a small turbo/BIG FMIC.

 

I posted a link to info on intercoolers, showing the dramatic lag you get when stepping up to a FMIC too soon. I'll find it....

 

Intercooler Info...

 

http://www.are.com.au/techtalk/intecoolersMR.htm#Bar%20and%20Plate%20or%20Tube%20and%20Fin

 

Turbo Talk...

 

http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech103.html