Help w/ Compressor Map Computation Values on a GT2860RS / GT28RS

[GetBoosted84]

Can someone review the values I am using the map out the efficiency of my turbo? I want to make sure they are correct.

Here is the info regarding how I am getting some of these numbers:
Turbo: The disco potato (GT2860RS)
Intercooler: EvoMS FMIC (Normally looking at 1.5 to 2 psi of pressure drop)
Chem. Cooling: Methanol/water injection (thus the lower than normal intake temp number)

BOOST(PSI)...............20
DISPLACEMENT(cc).........1781
INTAKE TEMP..............90
VOLUMETRIC EFFICIENCY....90%
COMP. INTAKE TEMP........545
COMP. INTAKE PRESS.......18.98
IC PRESSURE DROP(PSI)....2



By my calculations, I am completely out of effeciency at 20 PSI above 5.5k RPM which seems odd to me. With only 18 PSI I about 70+% across the board.

[Nebone]

What are you using for equations?

[GetBoosted84]

What are you using for equations?

To get the Comp Intake Pressure I take my boost and multiply by 0.948979591836734

Then after I have all the values, I do the following:

PRESSURE RATIO (PR) = ( BOOST + 14.7 + IC_PRESSURE_DROP ) / 14.7

DISPLACEMENT (Cu. In.) = DISPLACEMENT_IN_CCs * 0.0610237

INTAKE AIR DENSITY(Di) = ( BOOST + 14.7 ) / ( 53.3 * 12 * ( 460 + INTAKE_TEMP ) )

MASS FLOW RATE (Mf) = INTAKE_AIR_DENSITY * DISPLACEMENT * ( RPM / 2 ) * VOLUMETRIC_EFFICIENCY

CORRECTED MASS FLOW (CMF) = MASS_FLOW_RATE * ( SQRT( COMP_INTAKE_TEMP / 545 ) / ( 14.7 / COMP_INTAKE_PRESSURE ) )

Then I use the PRESSURE RATIO (PR) as the X-Axis and the CORRECTED MASS FLOW (CMF) as the y-axis and plot it on a compressor map like this one:

[Nebone]

I can send you an excel sheet calculator later. Advanced one but you can really use it.

[GetBoosted84]

All the calculations I outlined above were taken from the Excel sheet I currently use but I would love to see whatever you use for your calculations if you wouldn't mind. I'll PM you my e-mail address so you can send it over if you wouldn't mind.

[gotaudi]

post for all!!!!

[Nebone]

Is the volumetric efficiency of the 1.8T really 90%? Thats very good if you ask me.

I'll post the info for everyone later too.

Use the values and plot on that graph. See what you come up with. On that turbo, it should be in the middle of the compressor map.

[GetBoosted84]

Is the volumetric efficiency of the 1.8T really 90%? Thats very good if you ask me.

I'll post the info for everyone later too.

I cannot find any information to figure out what that number should be but I think you are right and it should be lower. 90% would be with a free flowing head I would imagine (which my AWM does not have since it's the small port).

[GetBoosted84]

Use the values and plot on that graph. See what you come up with. On that turbo, it should be in the middle of the compressor map.

Here is the compressor map with the mapped lines:

[mike-2ptzero]

So doesn't that mean at 20psi your right at the edge of the 75% range of the map if your flowing a max 30 CFM?


Might be time to upgrade your turbo to a 2871r, pretty big difference between the 2 maps. So with the same 2.5 PR at 20psi your smack in the middle of the 75% island and flowing a max of 37 CFM, plus plenty more head room for more boost.

[GetBoosted84]

lol, can't go that route just yet. Haven't even put this turbo into my car yet! Although when I do, my supporting mods will support it thanks to you and integrated engineering.

[mike-2ptzero]

lol, can't go that route just yet. Haven't even put this turbo into my car yet! Although when I do, my supporting mods will support it thanks to you and integrated engineering.

The best thing to do then is just not worry about the compressor map at this point and just find the sweet spot for boost.

[onemoremile]

There is a time for thinking and a time for action and this, gentlemen, is no time to think.

-john candy in canadian bacon.

[djwimbo]

... flowing a max 30 CFM?

...and flowing a max of 37 CFM,

I think you mean lbs/min. I think my chainsaw gobbles up 30CFM.

A lot of people have been real happy with the 2860 in the 18-20psi range. Whether it's real efficient at that point or not, it's hard to tell.
Compressor maps aren't extremely hard to read, but a lot easier to plot when you have first hand data to plot onto it.

[mike-2ptzero]

I think you mean lbs/min. I think my chainsaw gobbles up 30CFM.

A lot of people have been real happy with the 2860 in the 18-20psi range. Whether it's real efficient at that point or not, it's hard to tell.
Compressor maps aren't extremely hard to read, but a lot easier to plot when you have first hand data to plot onto it.

Yeah I meant CAF(lbs/min) instead of CFM.

[bassed]

Sheesh

[GetBoosted84]

The best thing to do then is just not worry about the compressor map at this point and just find the sweet spot for boost.

I am just trying to find the best amount of boost to run through the setup. Originally I was going to run 20 psi through it but now that I have some rods and a clutch that will support it I figured I would try to run some more boost if I wasn't completely out of efficiency.

Sheesh

lol, trying to see if more than 20 lbs of boost is feasable

No sense in wasting a perfectly good set of rods on just 20 psi.

[mike-2ptzero]

I am just trying to find the best amount of boost to run through the setup. Originally I was going to run 20 psi through it but now that I have some rods and a clutch that will support it I figured I would try to run some more boost if I wasn't completely out of efficiency.



lol, trying to see if more than 20 lbs of boost is feasable

No sense in wasting a perfectly good set of rods on just 20 psi.

Do you really think anyone running a chipped K03 is doing so in its efficiency? Think a K04 pushed at 25-28psi is in its efficiency? You think the tons of people that have already ran a GT28rs at 25-30psi were worried about its flow map? It isn't like your the first person to run the RS on a 1.8 and there have been plenty of people that have ran it on a fully built 2 liter at 25psi.

Stop thinking about it and just do it, thats the only way to know if it works are not.

[djwimbo]

Sheesh

You're normally the guy w/ technical advice and jargon.

And yes, 20+psi is feasible. Slap that stuff together and get it rollin.

[GetBoosted84]

Do you really think anyone running a chipped K03 is doing so in its efficiency? Think a K04 pushed at 25-28psi is in its efficiency? You think the tons of people that have already ran a GT28rs at 25-30psi were worried about its flow map? It isn't like your the first person to run the RS on a 1.8 and there have been plenty of people that have ran it on a fully built 2 liter at 25psi.

Stop thinking about it and just do it, thats the only way to know if it works are not.

Good point. I'll run it at at 20 psi until I hit a dyno.

Back to the values I was using for my calculations, I needed to alter them a little and I am still reviewing the formulas to make sure those are right.

You're normally the guy w/ technical advice and jargon.

And yes, 20+psi is feasible. Slap that stuff together and get it rollin.

lol, I'll get some tech jargon this weekend from him and poopie this weekend when the motor build goes down. Then I can get to having the flanges and bungs all welded together for the turbo to go on. I want to go for a ride in that beast of a car you have too bassed.