Selecting a turbo/reading compressor maps

[revolutionz_s13]

Ok. I have spent hours reading on this. I am looking at a Garrett GT25/40R turbo for my 95 KA24DE motor. I cannot figure out how to read compressor maps for the life of me using what little info I did find. I think I need the flow rate of the KA in order to make the maps more relevant. Although I am not new to the world of turbos (mostly experience with bolt-on kits), I am new to how to match a turbo up to a car based on the flow and efficiency which is seen on the compressor map. I am trying to put together a kit for my car, and want the best possible combination of parts/fastest spool time. My goal in the end is to run anywhere from 350-450 rwhp. Here is a link to the compressor map for that turbo. http://www.atpturbo.com/root/maps/gt2540r.htmHere is the link to the turbine map. ( what do I need to know about this map?) http://www.atpturbo.com/root/m...e.htm

Also, from what I gathered, a lower A/R will produce a quicker spool-up, but a higher A/R will give more top end power, but more lag. Is this correct. If so, I would be looking at the .64 A/R for this turbo. It is now 3:30am, and I'm not sure if the post quite makes sense, but I am at a loss after about 4 hours of research on this. It is killing me. Any help or other information that I might need would be appreciated.

-Nate

[:: orion ::]

For the KA, go with the .86 A/R...IMO.

Spool suffers with the .86 on the SR motor, but the KA has 20% more displacement, and will spool it MUCH quicker.

As for reading a compressor map...

See here, for starters:

http://www.turbosaturns.net (site is down right now??? But it's a good reference)

...

As for KA flow numbers...

You plot pressure ratio (PR) based on boost pressure = [ (expected boost + 14.5) / 14.5 ] = PR

So 12psi would be 26.5/14.5 = 1.83PR.

That's your Y axis.

The X axis, or flow in lbs/min, is determined based on the motors flow, volumetric efficiency, etc...there are formulas to determine flow...and what you're looking for is flow AT THE SPECIFIC PR, from spool to redline.

I'll give you some #s to help you get started:

8psi (1.54 PR), full boost at 3500, plot from 14 to 29lbs/min.

12psi (1.83), full boost at 3750, plot from 18 to 34 lbs/min

16psi (2.1 PR), full boost at 4000, plot from 22 to 39 lbs/min.

(The flow #s are based on 90% VE, stock displacement (149c.i.d.), and stock compression of 9.5:1.)

...and what you want are the beginning flow #s to be to the RIGHT of the surge line (right edge of the map), and the line to pass horizontally across the map tot he max flow #...and that should be still on the map.

Hope that helps...

- Brian

[C-Kwik]

zerothread?id=59168

You can also look at this thread as well..lotsa good info there.

[Checkered-Member]

My goal in the end is to run anywhere from 350-450 rwhp. Here is a link to the compressor map for that turbo.

I took the liberty to plot some lines Line 1: the approximate pressure you need to get 450whpLine 2: 400whpLine 3: 350whpLine 4: 240-260 whp @9 psi

Your goal of 350-450 can't be achieve with this turbo, it is however quite good up to 10psi

[C-Kwik]

I took the liberty to plot some lines Line 1: the approximate pressure you need to get 450whpLine 2: 400whpLine 3: 350whpLine 4: 240-260 whp @9 psi

Your goal of 350-450 can't be achieve with this turbo, it is however quite good up to 10psi

Checkered: By your reasoning, each boost level you indicate on the graph would still only yield 250 HP and be way too far to the left of the surge line. For a given engine, as you increase the pressure ratio(boost) airflow increases. Assuming your boost estimate is correct, the back end of your line 1 would need to be somewhere in the neighborhood of 45 lbs/min of airflow. The airflow would not remain the same at all boost levels. The reason more power can be made is because you are pushing more air and fuel into a motor, so as you increase boost, you also increase airflow...for a given motor.

A more typical map would look like this with each horizontal line representing the corresponding level of boost noted on the left column of the graph:



*Disclaimier: I did not plot these lines according to the KA's airflow rates but these are just an example of how an engine would typically map out against a compressor map.

[revolutionz_s13]

That turbosaturns.net site made the compressor maps very easy to understand. I have made a spreadsheet with all the airflow numbers for the KA24DE, including airflow under boost, which is to be considered. If anyone wants the spreadsheet, PM me, or email me @[email protected]. Thanks for plotting the map for me though.I think I have decided on this turbo, from what I gathered, this would work well for me. What do you guys think?http://www.turbobygarrett.com/...2.htmFrom what I determined by plotting points, I will be able to make ~500 flywheel HP@6000RPM with this turbo. Let me know if I figured it out, or am still messed up.**Edit: Another AWESOME SITE for turbo infohttp://www.turbobygarrett.com/....html


Modified by revolutionz_s13 at 11:07 AM 7/12/2005

[DRIFTEADOR]

both links are broken. when you copy a link you need to right click>copy shortcut and not just copy.

also, i don't know if you accounted for this on your hp estimate, but consider the difference in VE at different rpm points. it won't be 90% VE from 0-6.5k rpm.

[:: orion ::]

For a given engine, as you increase the pressure ratio(boost) airflow increases.

...

A more typical map would look like this with each horizontal line representing the corresponding level of boost noted on the left column of the graph:



*Disclaimier: I did not plot these lines according to the KA's airflow rates but these are just an example of how an engine would typically map out against a compressor map.

As I posted above, here are some KA airflow #s for each specific PR:

8psi (1.54 PR), full boost at 3500, plot from 14 to 29lbs/min.

12psi (1.83), full boost at 3750, plot from 18 to 34 lbs/min

16psi (2.1 PR), full boost at 4000, plot from 22 to 39 lbs/min.

(The flow #s are based on 90% VE, stock displacement (149c.i.d.), and stock compression of 9.5:1.)

- Brian

[revolutionz_s13]

Ok, the links are fixed. I also think the Garrett GT3076R might be a better fit. here is that link. http://www.turbobygarrett.com/...2.htmSorry for asking so many damn questions, I am just trying to figure all this stuff out.Thanks for all the help guys.
Modified by revolutionz_s13 at 12:37 PM 7/12/2005

[Checkered-Member]

LoL…I knew something was wrong with those lines …oops…good fix