How to read compressor maps

[Underdog]

Turbo2nr, any more details on the WRX? I couldn't find any compressor charts for the AVO500 and what kind of TMIC were you running?

 

LBGT: I see your point regarding maxing out the TMIC but I haven't seen anything concrete on IC efficiency and what sort of flow loses it would incur at varying boost pressures. If we could see that information then we would know exactly what trade-offs were being made. I believe that with a properly coated/wrapped turbo and high-flow exhaust we could push 1.5+bar on a mid-high rpm setup with a TMIC. We can't say what is properly matched or improperly matched unless we have the specs of the IC in question.

[LittleBlueGT]

Turbo2nr, any more details on the WRX? I couldn't find any compressor charts for the AVO500 and what kind of TMIC were you running?

 

LBGT: I see your point regarding maxing out the TMIC but I haven't seen anything concrete on IC efficiency and what sort of flow loses it would incur at varying boost pressures. If we could see that information then we would know exactly what trade-offs were being made. I believe that with a properly coated/wrapped turbo and high-flow exhaust we could push 1.5+bar on a mid-high rpm setup with a TMIC. We can't say what is properly matched or improperly matched unless we have the specs of the IC in question.

 

You definitely have my attention now (not for my set-up, but just for general info)!

 

In my talks with Sean I was under the impression that the AVO420 made within about 10 hp of the AVO450 when used with a TMIC.

 

I know the AVO V1 TMIC is too small for the AVO420 and limits the AVO380 a bit. The V2 TMIC does not flow limit as much but has less ability to extract heat.

 

 

Now it may be different on different cars, but for our cars I think anything that produces over about 400 chp is limited by the FLOW capability of our TMIC.

[turbo2nr]

I ran 30PSI thru a TMIC, it was a 2002 TXS style IC. The turbo was all done. I had the wastegate pretty much fully closed, running Red-Max #5 (116-117.5octane)

 

My turbine housing cracked, because to stuff such a large turbine wheel, the walls became too thin after machining......AVO re-released the AVO 500.....that was five years ago, or so......new turbine castings from the foundery in AU.

 

 

I got one for free. AVO is a decent company!

 

I don't see why 450-500HP is out of the question with a TMIC on a Legacy. Want me to prove it this summer? I am a little busy building a $20,000 engine package for my Buick for the 2007 season of drag racing, and still have to finish my WRX fuel system and safty crap to run over 135MPH, but I may find time to mess around with my wifes car a little more.

 

I also just bought and sold a house....YEAH!!! TWO CAR GARAGE!~! BIG Ceiling, going to get a lift!! SO HAPPY! I got wood, just thinking about it.

[Underdog]

Wow man, I'm pumped for you! I can't wait to have a garage space. It is a requirement for my next domicile.

 

I'm thinking the same thing in regards to the TMIC. It might not be a perrin or avo product if it comes to that but that's something that will be figured out. I'll have plenty of time to look into it over the next few years while the engine "seasons."

 

I've always had a special place in my heart for turbo Buicks so make a thread with some pics!

[turbo2nr]

My car will be near you getting the new engine installed @ www.cottonsperformance.com

Springfield MA

 

I have a stand alone ECU of course, Built turbo 400 pro-tranny with solonoid T-brake, manual valve body (have to shift it yourself) Spool, Moser 33spline axles, Racing aluminum heads and solid roller cam, etc....around 820-850HP and maybe 9.2-9.0 ? in the quarter I'm hoping.

 

My GN has the original paint and just over 20,000 miles. IT's a thing of beauty!

 

Here is a link to my old engine buildup....it ran an easy low 10 on a crapped out 200r4 tranny that wouldn't shift.

 

http://www.turbobuick.com/forums/turbo-videos-picture-library/200559-board-member-turbo2nr-feature-car-month-november.html

 

 

http://www.elisetalk.com/forums/showthread.php?t=20207&highlight=spectrum

[turbo2nr]

Ever pop a wheelie in a big car shaped like a brick?

 

It's FUN!

 

Who needs AWD at that level??

 

My other Subaru is also ready for RWD.....more later, shhhhh.

 

 

** In 1993, Subaru decided to only offer AWD on all it's models. True.

[LittleBlueGT]

I have yet to hear or see anybody run much higher then 340-350 whp on an available LGT fitment TMIC.

 

FLOW restricted.

 

If you can prove otherwise, go nuts, I would love to see it!

[2005garnetGT]

someone needs to make a topmount AWIC that doesn't leak/suck.

 

 

I have yet to hear or see anybody run much higher then 340-350 whp on an available LGT fitment TMIC.

 

FLOW restricted.

 

If you can prove otherwise, go nuts, I would love to see it!

[VTGT]

 

I don't see why 450-500HP is out of the question with a TMIC on a Legacy. Want me to prove it this summer?

 

Can't wait to see 500 whp in a 5eat legacy with a TMIC and stock tranny, you will be my hero . Unless your plan involves using a race tranny in the legacy?

[turbo2nr]

Hmmmm. I may have toi do something to help firm up the shifts

[Vimy101]

^ It all comes down to application, fellas. The right tool for the job.

 

Great thread.

 

BTW, I finally found this thread through a member wanting to do a quantitative reasoning paper. Isn't science grand?

[spacejunkiehsv]

Where can you get an engine demand curve for the engine in my 05 LGT? I'll take spreadsheet data if anyone has that.

[turbo2nr]

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.

 

 

 

Please read and re-read what the housing A/R number means. It has nothing to do with the exducer size at all. 3/4 is a .75 A/R housing.....4/5 is a .80 A/R or close to that. It has to do with the VOLUME inside the housing and the nozzle area. Different "trim" turbine wheels can fit in the exact same housing with the same A/R, but still have different exducers and the housing is machined to match.

 

If two turbos have the same turbine wheel (same trim).....then the exducer HAS to be the same and the bore in the housing will aslo be the same, regardless of the A/R of housing. ......and then you could stick that wheel into many different housings with different A/R

 

Some turbo companys use a decimal point and some use a fraction to describe the A/R.

 

I did not quote your whole post.....I deleted the last sentence.

 

All housings are machined to have about the exact same spaceing between the exducer and the housing. (trim of wheel matches machining of housing)

 

Velocity is lost in the larger housing...it has nothing to do with the bore of the housing for turbine. Just trying to get you to think of air speed going on.....not air slipping by the wheel because of a larger hole. That is wrong.

 

 

The larger turbos are absolutly more efficient, for whoever stated otherwise. You need to look at exhaust backpressure, heat added into the charge by tiny wheels spinning too fast, etc....to come up with an idea of what affects the turbos efficiency. You can't just say all centrifugal wheels are about the same. I think what you may be trying to say is, all centrifugal style wheels have the same compressor map SHAPE, almost.

[turbo2nr]

Ever hear of the term "crossover point" in regards to turbos?

 

It is possible to make more boost than exhaust backpressure....resulting in an engine with well over 100% Volumetric Efficiency. Even up to and over 150% efficiency.....Supras and GNs with BBBIIIIIIGGGGG turbos can reach this point. Who said 77%?? Hog wash! (I know I'm talking about the engine and not the turbo now, different subject, but they go hand and hand)

 

http://www.gdsdieselparts.com/ball_buster_product__details.htm

 

http://www.airpowersystems.com.au/350z/turbo_flow.htm

[Underdog]

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.

 

This a quick explanation of exducer bore size AND A/R ratio. I'm not saying that a larger A/R directly results in a larger exducer bore.

[turbo2nr]

Good stuff! Carry on.....

[BlackHole]

FWIW, for my modeling I've found that the following Garrett compressor maps work reasonably well vs. real-world data for calculating airflow and hp for the IHI VF series since IHI doesn't like sharing their compressor maps:

 

VF40 = T3-50

VF39 = T3-60

VF30/34 = T3-super 60 or GT2530

 

YMMV,

Kyle "BlackHole"

[hyteck9]

Now if we wanted to increase the output of the stock motor from 250chp to maybe 375chp for easy math (and close to 300 whp) we can determine the necessary boost required.

 

target chp/current chp = 375/250 = 1.5

 

If we multiply this ratio by the stock boost (13.5 psi) then we determine we will need approximately 21 psi of boost in order to reach our goal.

 

We can now use the new pressure ratio of (14.7+21)/(14.7) = 2.43 to determine how much flow we must spec. the turbo at.

 

CFM = ((Displacement(cid) * rpm * .5 * Ve (assume 90% or .9))/1,728) * Pressure ratio = ((150*6500*.5*.90)/1,728) * 2.43 = 617 CFM

 

So... in order to produce peak boost at redline we need a turbocharger capable of flowing 617 CFM (or ~50 lb/min) at a pressure ratio of 2.43.

 

Obviously a very simplistic example as it makes no note of losses and is based on only a single parameter (target hp at redline) but hopefully it helps someone.

1st, this thread is awesome!!! I'm learning a great deal.

 

That said, I have a few questions since I have absolutely no experience turbo matching:

 

In the formula above isn't the CID more like 153?

where did the divide by 1728 come from?

Ve of 90% is typical for NA engines, does it still apply with the GT's lower compression ratio?

 

Just trying to understand... I might try to put to gether a little java app. with some of the values hard coded specifically for LGT's.. fun stuff!

[Underdog]

I'm at work so I gotta answer quickly...

 

Displacement: 2,457cc -> 149.94 in^3 ~> 150CID

 

1,728 is the conversion factor from in^3 to ft^3 (12x12x12=1,728).

 

90% Ve was an educated guess based on the fact that we have a modern engine with variable cam lift/timing and 4 valves per cylinder. I would love it if someone could step up and give us a more solid value.

[BlackHole]

90% Ve was an educated guess based on the fact that we have a modern engine with variable cam lift/timing and 4 valves per cylinder. I would love it if someone could step up and give us a more solid value.

 

I wish I had real world data on VE but from my modeling it's not very pretty. But these values do seems to mimic real dyno results quite well, especially the bottom-heavy torque curve Subies are known for.

 

 

rpm VE

2000 85%

3000 92%

3500 90%

4000 91%

5000 94%

6000 82%

6500 77%

 

just my $.02,

Kyle "BlackHole"

[Underdog]

Kyle,

 

I would love to know how you are modeling Ve. I still think 90% is a good guestimate from the info you provided.

 

-Rick

[2005garnetGT]

I wish I had real world data on VE but from my modeling it's not very pretty. But these values do seems to mimic real dyno results quite well, especially the bottom-heavy torque curve Subies are known for.

 

 

rpm VE

2000 85%

3000 92%

3500 90%

4000 91%

5000 94%

6000 82%

6500 77%

 

just my $.02,

Kyle "BlackHole"

 

subaru heads aren't that great really.

[BlackHole]

Rick,

 

I would love to know how you are modeling Ve. I still think 90% is a good guestimate from the info you provided.

 

What I basically did is worked backwards from the AVO380 vs. stock dyno chart posted in the archives. That chart had actual data on boost level, AFR, whp and wtq. I assumed drivetrain efficiency at 76% (stock 250hp claimed, 190whp avg on dyno). Assuming that the Garrett T3-50 compressor map was close to the stock VF40 (similar dimensions) I worked backwards to adjust the VE to meet the known values from the AVO dyno.

 

While a bit crude, the projected whp and torque results were reasonably close to real dyno results for both stock and tuned VF40s and when recalculated with a VF39 (using a T3-60 compressor map) the data matched up well with published STi dyno results.

 

They are certainly not perfect numbers, but so far for my work they have mimicked real-world data well enough, even when TMICs and CAIs are factored in. And the loss of VE at higher rpm echoes what many tuners have said. When looking a bigger turbos, the projections are not quite as robust.

 

Two comments:

1. I suspect that when the stock exhaust + turbo + intake (including IC) parts are upgraded, the VE jumps a bit. That itty bitty stock turbine wheel and the three cats seem to be major restrictions.

2. Drivetrain loss is not a linear percentage, but I don't have any better data.

 

just my $.02,

Kyle "BlackHole"

[BlackHole]

Rick,

 

I would love to know how you are modeling Ve. I still think 90% is a good guestimate from the info you provided.

 

What I basically did is worked backwards from the AVO380 vs. stock dyno chart posted in the archives. That chart had actual data on boost level, AFR, whp and wtq. I assumed drivetrain efficiency at 76% (stock 250hp claimed, 190whp avg on dyno). Assuming that the Garrett T3-50 compressor map was close to the stock VF40 (similar dimensions) I worked backwards to adjust the VE to meet the known values from the AVO dyno.

 

While a bit crude, the projected whp and torque results were reasonably close to real dyno results for both stock and tuned VF40s and when recalculated with a VF39 (using a T3-60 compressor map) the data matched up well with published STi dyno results.

 

They are certainly not perfect numbers, but so far for my work they have mimicked real-world data well enough, even when TMICs and CAIs are factored in. And the loss of VE at higher rpm echoes what many tuners have said. When looking a bigger turbos, the projections are not quite as robust.

 

Two comments:

1. I suspect that when the stock exhaust + turbo + intake (including IC) parts are upgraded, the VE jumps a bit. That itty bitty stock turbine wheel and the three cats seem to be major restrictions.

2. Drivetrain loss is not a linear percentage, but I don't have any better data.

 

just my $.02,

Kyle "BlackHole"

[BlackHole]

Interesting tidbit about LGT efficiency from imprezarsx on osecuroms:

 

I compared these (LGT) logs to some STi logs. WOW, I couldnt believe my eyes. This car has a TON of flow restrictions. Not sure where they all are, but my guess is the exhaust and intercooler. For the same RPM, same boost, and same Cam Timing, this car is passing 203 g/sec vice (vs.) the STi's 260. That's almost 30% less airflow. The injector duty cycle is less than 85% where the sti hit 98% (woops).

 

Kyle "BlackHole"