How do you read a compressor map?

[DakotaKid]

Sorry if this has been covered before, but you can not search 3 letter words!

So what does the map tell you?

[scott]

here's a start for what they explain:

http://www.turbomustangs.com/index2.htm

but the map tells you how much a turbo can flow...w/ this you can see how much air your engine can take and at what boost level you'll be at to take in that air to see what efficiency your at.

--scott

[gasketmaster]

Bryan,
The numbers going down the side are the pressure ratio numbers.
To get your pressure ratio use this formula:

boost+14.7
-------------- = pressure ratio
14.7

Yours :)

34 + 14.7
------------ = 3.31
14.7

The numbers along the bottom are lbs. per minute of air flow.

It takes @ 10 lbs. of air flow per 100 hp at the flywheel

Trace your pressure ratio over until it intersects with the air flow required to achieve your flywheel hp.At this point you are looking at the efficiency percentage at which your turbo is currently working :)
It should be above 60% minimum...........the higher the better "thumbs up

You can shoot me a pm if you have any question :)

Keep up the good work ;)

[DakotaKid]

Thanks Terry!

So 10 lbs for every 100 at the flywheel.

Should I add 5% to my dyno number? Or something else?

By the looks of that It would look like this picture (Right?)

Am I done with this Turbo?

34 PSI @ 337 WHP

[gasketmaster]

IMHO..........yes......you are because this is a drag race only car and you are on the edge of the map.

You don't really ever intend to turn the boost down and run it at a lower setting....correct?

With this in mind you should shoot for the center island of efficiency.

One problem is.........you may start to encounter spool up problems as you step up in turbo size which sometimes can require a restall on your converter ;)

Another thing not to do is cross over the surge line along the left side of the graph.

You need to do some exhaust back pressure testing with your current setup to help steer you to the answer that you are looking for ;)

[DakotaKid]

I have no plans to turn boost down.

But I do have plans for a ported head.

For sake of conversation, let's say that with a ported head, I will only need 27 psi to make 337 HP, then the turbo becomes better for the application, correct?

It is directly related to the amount of boost needed to create the given horsepower I guess.

27 PSI @ 337 WHP Picture:

[gasketmaster]

Quote:

Originally posted by TrboVan I have no plans to turn boost down. But I do have plans for a ported head. For sake of conversation, let's say that with a ported head, I will only need 27 psi to make 337 HP, then the turbo becomes better for the application, correct? It is directly related to the amount of boost needed to create the given horsepower I guess. 27 PSI @ 337 WHP Picture:

Yes..........you are correct but............you know your not putting the ported head on so you can turn the boost back down......right? :big grin:

The ported head will require more air flow at the same pressure ratio normally ;)

If the ported head adds 50hp at the 3.31 pressure ratio you'll be off of the map with your current turbo :)

[4sfed4]

Quote:

Originally posted by gasketmaster You need to do some exhaust back pressure testing with your current setup to help steer you to the answer that you are looking for ;)

Yes! Defintely do as Terry suggests. The turbine backpressure readings will tell you quite a bit about how the turbo is fairing on your application.

My first question is---

Do you get any anti-creep (i.e. does the boost pressure drop with rpm) or are you able to hold the desired 34 psi all the way to redline?

[4sfed4]

An interesting test would be to try to the TO4E "Super" 50 trim wheel over what you have now (the "regular" 50 trim).

According to the maps, it is much better suited to high PR applications.




According to this map, at a 3.31 PR and 390 crank hp, the compressor will be well within the 76% efficiency island and will also be spinning at about 115,000 rpm, versus the 123,000 rpm the "regular" 50 trim is spinning to move the same mass of air. The slower compressor wheel will drop turbine backpressure.

I had the Super 50 on my car before and really liked it. In my experience, it will crap out around 390-400 whp (simply cant move anymore air than that...power will flatline on dyno). In my conversations with Turbonetics and Precision Turbo, both suggested an absolute maximum 450 crank hp rating for the TO4E 50, so that matches well with my dyno results. The "Super" and "regular" 50's both use the same inducer size, so they are both going to be capable of the same maximum airflow. In my current case (all relatively low boost pressures planned), the regular 50 is probably a better match.

[glhsken]

Terry, that 50 hp would put him in the 74% island barely... but spinning hard.

There is a lot to do with set-up.. I've seen a car with the same turbo make 340+ hp on 25 psi of bost.

[Frank]

Quote:

Originally posted by TrboVan [B]Thanks Terry! So 10 lbs for every 100 at the flywheel. Should I add 5% to my dyno number? Or something else? By the looks of that It would look like this picture (Right?) Am I done with this Turbo? 34 PSI @ 337 WHP

I dont know if you are quite done with that turbo. i roughed in some VE numbers into my garrett spreadsheet and i came up with this for your turbo... lines represent your demand lines from 2k - 6k rpms respectively from left to right.

it is not always obvious, but really your power comes from extending those lines to the right. one of those ways to do this is to increase your VE. this is achieved through work on the manifolds, heads, etc. this is kind of convoluted because if you increase flow, you would directly expect shift a shift to the right. well its really indirectly because it directly effects VE.

so no you are not done with this turbo in the respect of power through that thought process, but yes you are done in the aspect of pressure ratio.... you cant spin faster.

but now lets factor in how much VE you can achieve through a lot of work. so best case senerio on these crappy heads would be that you have increased it 2-3% up high and 4-6% down low. how does this help you? not much. you will probably see a shift to the left of the low end demand lines of around 7-9lbs/min at your 34psi. because of this you might be done with this turbo, but looking at my other maps, you might be better off with this one.

attached is your deman lines for a non ported head... yes they are assumed VE, but they are real close.

[Frank]

Quote:

Originally posted by 4sfed4 An interesting test would be to try to the TO4E "Super" 50 trim wheel over what you have now (the "regular" 50 trim). According to the maps, it is much better suited to high PR applications. According to this map, at a 3.31 PR and 390 crank hp, the compressor will be well within the 76% efficiency island and will also be spinning at about 115,000 rpm, versus the 123,000 rpm the "regular" 50 trim is spinning to move the same mass of air. The slower compressor wheel will drop turbine backpressure. I had the Super 50 on my car before and really liked it. In my experience, it will crap out around 390-400 whp (simply cant move anymore air than that). The "Super" and "regular" 50's both use the same inducer size, so they are both going to be capable of the same maximum airflow.

that turbo would give him around these kind of demand lines.

[Frank]

Quote:

Originally posted by fkatzenb that turbo would give him around these kind of demand lines.

Good call Larry,

based on that graph, and the thought of increasing VE through porting etc, you will definently have a better setup with the super-50 t04e.

just my 2 cents.

frank

[DakotaKid]

Quote:

Originally posted by 4sfed4 My first question is--- Do you get any anti-creep (i.e. does the boost pressure drop with rpm) or are you able to hold the desired 34 psi all the way to redline?

Boost will spike about 2 psi when power hits, then settle and hold a steady 34 psi.

[Frank]

Since this is as good as thread as any, here is my map for the turbo I am putting on my 3.0L. (demand lines are at 2500 and 3000 to 8000 rpms respectively left to right).

The compressor wheel you are looking at is a DBB GT37. I will be matching it up with a GT31 turbine that contains a GT30 wheel which creates a GT3037. This should compensate for the lower flow that my engine has when compare to better flowing 3.0l's that use the full gt37 package or the super large a/r of the gt3037 setup.

The gt3037 turbine a/r's availabe are .63, .82, and 1.06. I probably wont decide which of the two smaller a/r's to use until i have recieved flowbench numbers from my head work that Brian Slowe will be doing shortly.

The compressor map is a different story. I want an all around car... road race (& autocross), street, and drag - in that order. So initially I was thinking that i would want the 76mm (or T04) housing, however, i would sacrifice the high end that I feel that this motor can grab (with custom manifolds and intake). So should I go with the 82mm? I dont know how the 82mm would effect me with my autocross and low end. The other thing to note that in the autocross/road racing, I will be barely pushing 25psi, but on the drag, 30psi. And again, another aspect to note is that the gt3037 setup flows less at high end then the full gt37 setup, so will i even achieve the high end of the 82mm compressor?

Plain and simple, its all a mess :big grin:

Any suggestions would be golden.

Frank