Lets look at some compressor maps

Checkered-Member · Post by **Checkered-Member** » Mon Apr 05, 2004 7:47 am

I was bored and made some compressor map of T4E 50,54 & 57 trim all at 9 psi.

Assuming the following:

At 6000 rpm the KA flows 26lb/minAt 3500 rpm the KA flows 15lb/min and you hit full boost at this level.Between 1000-3500rpm the boost vs. flow rises linearly (some one hit me if this assumption is wrong.

First is the highly regarded 50 trimHitting 9 psi at 72% efficiency Boost rises 70% threw 72% and starts at 8lb/min

The 54 trim.Hitting 9 psi at 74% efficiency Boost rises 70% threw 72% and starts at 5lb/minLook how long you stay at 9psi at maximum efficiency compare to the 50 trim

The 57 TrimHitting 9 psi at 70% efficiency Boost rises 65% threw 70% and starts at 8lb/minLook how short the maximum efficiency is at 9psi, most of the time you are in the 73%

Conclusion: for low boost 7-11 psi (which most of the guys on here run or plan to run) the 54 trim is ideal, also when boost is getting build up the 50 and 54 stay within a good efficiency range, while the 57 is not. The 54 trim starts building boost the lowest, at 5lb/min vs 8.

something to think about when selecting a turbo

Post by **C-Kwik** » Mon Apr 05, 2004 7:47 am

Good post. But I will note that the turbine you choose can affect the slope of the curve as boost rises and also the point at which the set boost is reached. The 54 Trim has a slightly better efficiency at 9 psi, but I'd still get the 50 Trim myself for the headroom. The difference is quite marginal at that boost.

"Between 1000-3500rpm the boost vs. flow rises linearly (some one hit me if this assumption is wrong."

Not exactly, but it would be way too complicated to calculate. Th VE of a motor changes with RPM. And with boost rising, the airflow would not be constant for a given RPM. Heck, it's already different from one gear to the next. I usually draw the line to 0 from th boost threshold point only to confirm there are no surge issues and to get an idea of the efficiency during the boost rise.

Checkered-Member · Post by **Checkered-Member** » Mon Apr 05, 2004 7:47 am

C-Kwik wrote:I will note that the turbine you choose can affect the slope of the curve as boost rises and also the point at which the set boost is reached.

I was trying to figure out the curve, after thinking about it for 30min, a strait line is just easier, I would think the actual curve is something more like so;

The engine has to overcome the initial restriction of the turbo, then as the turbine starts spinning the restriction goes away, just trying to picture what an actual PR vs. Flow slope looks like.

is this more accurate?

Post by **C-Kwik** » Mon Apr 05, 2004 7:47 am

Actually, no. It's difficult to picture this. The compressor maps don't reference time changes in anyway, so the slope would not reflect that. The Engine will see a particular VE at a given RPM. This VE dictates how much flow the motor will have. At a given boost, the flow will change based on VE and engine speed. But since RPM is constantly rising when you are at WOT, the VE changes. It is possible for the slope to look like what you posted, but it really just depends on the motor. Also, as I've said, spool up relative to RPM changes with gearing/load. So different gears will see a slightly different curve. I usually make my calculations condisering the highest gearing as this will push the boost threshold furthest to the left. This will give me the safest margin for error against surge. But I only scrutinize that if it is close enough to the surge line to cause worry.

Post by **Redline240** » Mon Apr 05, 2004 7:47 am

Does anyone have the compressor maps for these turbos at 14psi? at 18-20psi too if possible? Just to see which is more efficent at higher boost levels...

Redline

Post by **spitz7985** » Mon Apr 05, 2004 7:47 am

so would this be right for a T3 60 trim (my turbo), assuming the same (although I'm guessing the T3 would hit 9psi before 3500. how'd you figure out the flow rates of the KA at the given rpm? also, how do you calculate the pressure ratio from the pounds per square inch?

Post by **C-Kwik** » Mon Apr 05, 2004 7:47 am

I can't see the pic. Calculating flow rates is done based on a few assumptions, unless you have actual test data from the KA. I don't feel like looking up the equations. But you can find them in Maximum Boost by Corky Bell, or even in the June 2003 SCC magazine.

Pressure Ratio is Absolute pressure plus boost pressure divided by absolute pressure. Most people assume 14.7 psi as absolute. 14.7 psi = 1 bar. so a pressure ratio of 2 is 1 bar of boost. A PR of 3 is 2 bar of boost. Multiply Bar by 14.7 and you will get your boost in psi.

Post by **spitz7985** » Mon Apr 05, 2004 7:47 am

why didn't the pic show up?

it shows up for a minute and then the next time i refresh it doesn't work if i'm logged out from my pic hosting page. what do you guys use to host pictures?

Post by **TrunkMonkey** » Mon Apr 05, 2004 7:47 am

a very good post Checkered-Member.

Quote »how'd you figure out the flow rates of the KA at the given rpm? also, how do you calculate the pressure ratio from the pounds per square inch?[/quote] imo, the absolute best written article on how to plot compressor maps ever.

-demetrius

Post by **C-Kwik** » Mon Apr 05, 2004 7:47 am

Good link Demetrius. I only skimmed it and the only error I found was he called coking, choking when referring to cooking oil onto the bearings. The explanations of the maps were good.

Checkered-Member · Post by **Checkered-Member** » Mon Apr 05, 2004 7:47 am

spitz7985 wrote:so would this be right for a T3 60 trim (my turbo), assuming the same (although I'm guessing the T3 would hit 9psi before 3500. how'd you figure out the flow rates of the KA at the given rpm? also, how do you calculate the pressure ratio from the pounds per square inch?

flow rate for KA:

2.4L x RPM X 90 x PR/ (5600x14.27) = lb/min

RPM is the enigne speed

PR is 14.7+ boost /14.7= PRex. 14.7+9/14.7 =1.6122

T3 60 trim compressor

Assuming full boost at 3000rpm

Notice that past 5600rpm you are surging the turbo

(the actual slope is up for debate, but its a good estimate)

Post by **:: orion ::** » Mon Apr 05, 2004 7:47 am

I have an Excel sheet that calculate this VERY easily...you just plug in the boost, and it'll give PR and flow in lbs/min.

I also included a numerical estimate for HP, and it's theoretical, but it's a good spot check.

I uploaded it here for everyone:

Right Click, save as...please - ( compressor_maps.xls )

Just play with the numbers in green, the rest will calculate automatically...

I assume a 90% VE, the stock KA is 149 cubic inches, and the stock CR in the 240SX is 9.5:1...

- Brian

Post by **C-Kwik** » Mon Apr 05, 2004 7:47 am

Checkered-Member wrote:flow rate for KA:

2.4L x RPM X 90 x PR/ (5600x14.27) = lb/min

RPM is the enigne speed

PR is 14.7+ boost /14.7= PRex. 14.7+9/14.7 =1.6122

T3 60 trim compressor

Assuming full boost at 3000rpm

Notice that past 5600rpm you are surging the turbo

(the actual slope is up for debate, but its a good estimate)

Surge actually occurs only to the left of the map. If it goes of the right edge of the map, it's only becoming more of a heat pump. It can still operate safely there, but the efficiency is so bad it makes no sense for the turbo manufacturer to even test or provide numbers in that range.

Post by **Jookmasta** » Mon Apr 05, 2004 7:47 am

ok so then in other words i was right to choose my little t3 60 trim turbo for the little 8 psi that i want to run?

Post by **C-Kwik** » Mon Apr 05, 2004 7:47 am

That's too subjective to answer. It's not a turbo I would choose even for 8 psi. It's a matter of personal preference and each person's opportunity cost.

Post by **Jookmasta** » Mon Apr 05, 2004 7:47 am

so what would have u chosen?

Post by **C-Kwik** » Mon Apr 05, 2004 7:47 am

I doubt it's any big secret that I'm a fan of the T04E-50 Trim compressor. But I will say I don't mind a little lag and I prefer the bigger power.

Checkered-Member · Post by **Checkered-Member** » Mon Apr 05, 2004 7:47 am

Well since thie thread became a sticky I will add the following information:

CFM = L x RPM x VE x PR . . . . . . 5600

(convert to lb/min, divide CFM by 14.27)

L = engine capacity in litersRPM = engine speedVE = engine volumetric efficiency.

2-valve 1 cam = 82%2-valve 2 cams = 85%4-valve 1 cam = 88%4-valve 2 cams = 90%5-valve 2 cams = 91%

If you have variable lift or variable timing add 1%Street Modified: add 2-3%

Competition = 105%

Pr = pressure ratio 14.7+psi/14.7

Post by **fiznat** » Mon Apr 05, 2004 7:47 am

wtf I had a good post about compressor maps too, it even had an excel spreadsheet with all the math already done for the KA's flow rates... how come THAT didnt get stickied huh?

anyways I guess to add to this one, heres the link:

http://www.nissaninfiniticlub....9195&

Checkered-Member · Post by **Checkered-Member** » Mon Apr 05, 2004 7:47 am

fiznat wrote:wtf I had a good post about compressor maps too, it even had an excel spreadsheet with all the math already done for the KA's flow rates... how come THAT didnt get stickied huh?

aww...I guess I’m just more popular ....:pface

JK, that is a good post...mines better thou:pface

Post by **TrunkMonkey** » Mon Apr 05, 2004 7:47 am

fiznat wrote:wtf I had a good post about compressor maps too, it even had an excel spreadsheet with all the math already done for the KA's flow rates... how come THAT didnt get stickied huh?

ummm...blame WD? why? i don't know, but we do love you fiznat. really, we do

.

-demetrius

Post by **fiznat** » Mon Apr 05, 2004 7:47 am

awwwwwwwwwww okay, everything is better now haha

Post by **spitz7985** » Mon Apr 05, 2004 7:47 am

demcj wrote:a very good post Checkered-Member.

imo, the absolute best written article on how to plot compressor maps ever.

-demetrius

Are you sure that the Turbo Saturn site is right? I used their formula to calculate the flow rates for the KA and got these numbers assuming 90% VE and 146 CID. Maybe I screwed up somewhere because it just seems wrong (but I double checked it ?).

RPM lb/min7200 18.96200 16.35200 13.64200 113200 8.42200 5.81200 3.2

Post by **TrunkMonkey** » Mon Apr 05, 2004 7:47 am

yes, the site is right.

i use 85% VE and 145.78 cid.

rpm lb/min

2000 4.953000 7.424000 9.905000 12.376000 14.846900 17.07

i haven't double checked them, but your numbers look about right.

-demetrius

Post by **spitz7985** » Mon Apr 05, 2004 7:47 am

The flow numbers are way differnet then the ones Checkered-Member used on the first thread of this site....

Have you tried plotting them? They just seem wrong. Or maybe I am. IDK

Post by **TrunkMonkey** » Mon Apr 05, 2004 7:47 am

spitz7985 wrote:The flow numbers are way differnet then the ones Checkered-Member used on the first thread of this site....

that's because Checkered-Member's numbers are for what the KA would flow at 9psi. yours and mine are for n/a.

multiply everything you have in your post by 1.61 and you'll see that everything is just gravy

.

-demetrius

Post by **spitz7985** » Mon Apr 05, 2004 7:47 am

sweet, i knew something was wrong. thanks. :pface

Post by **p00t** » Mon Apr 05, 2004 7:47 am

I guess using a static VE is ok... I wasnt happy with it tho and did some rough estimates of the real VE of the KA according to some different dyno charts (theoretical vs actual). I hoped this would help me see the flow better as it is being used rather than it being a plain VE + flow @ 6000rpm...

heres what I came up with:

- - - - - - - - - N/A - - 10psiRPM - VE - lb/min - lb/min2k - - 78% - 4.5 - - 7.52.5k - 82% - 6 - - -- 103k - - 82% - 7 - - - - 123.5k - 88% - 9 - - - - 154k - - 95% - 11 - - - 18.54.5k - 96% - 12.5 - - 215k - - 93% - 13.5 - - 235.5k - 87% - 14 - - - 246k - - 78% - 13.5 - - 236.5k - 66% - 12.5 - - 217k - - 54% - 11 - - - 18.5

I can post up the way i calculated it.... not hard.. but may be totally wrong. I basically looked at a dyno graph of an NA 240, with mild upgades. Then I did theoretical power ((146ci * RPM) / 3456) * VE = CFM or for lb/min its CFM *.069 . I left VE at 100%, then did a very rough estimate that moving lb/min over one decimal point is your HP, so that on the graph it shows your HP at 3000rpm is lets say.. 140... and your 100% theoretical would be 165 hp... then your VE would be near 140/165 = 84%.

This is a very rough estimate, and I guess I will take samples from actual turboed KAs... since many flow problems an engine has is reduced when being force fed. Example being the KAs VE at high RPM.... it clearly shows WHY you lack power up top, and how power peaks 500-1000rpm after the peak VE on this engine. Also shows how shifting the VE up top gains more power.

Its interesting to note how more RPM doesnt mean you flow more..... so if the turbo is efficient at 4.5-5.5k for the KA it will be fine at the higher RPMs with the boost kept around the same pressure. Another thing learned from this I suppose is dont just take any random rpm and use that flow number, since you may actually be under/over rating how much output your car is making!

Let me know what you think, if I'm totally wrong let me know.

Post by **somthin240** » Mon Nov 15, 2004 4:49 pm

has anyone mapped the TD04-13G to the flow of the ka? I have the map if anyone wants it.

Post by **Calesta** » Tue Nov 16, 2004 4:46 am

I've matched it up before myself- that turbo is WAY too small for a KA24. You're going to be outside the last efficiency before 5000rpm no matter what pressure ratio you're at.

Lets look at some compressor maps

Lets look at some compressor maps

Re: (somthin240)

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