[cstavaru]

Hi,

EDIT: I have now added maximum power and maximum torque figures. Now you can see how meth helps !

Have you ever wondered how much boost is really safe for your stock turbos, and how to calculate it ? The sticky thread about the Mitsubishi TD03 turbo characteristics does not mention any calculations, just speculations. This was driving me mad. I needed real answers based on calculations.

With the help of a software program that I just made, I have calculated how much boost is safe for the stock N54 turbos, at each RPM.

Based on the results below and your logs, you can see if your turbos are inside the efficiency range or you are pushing them too hard.

I used these materials as a reference:

This tells you how to calculate various parameters:

http://www.turbobygarrett.com/turbob...Catalog_V4.pdf

This tells you the Mitsubishi TD03 turbo efficiency maps:

http://www.e90post.com/forums/showthread.php?t=256804

Algorithm: For each RPM (in steps of 100), check each psi value from 22 down to 0, in steps of 0.1psi, and see if the resulting values (pressure ratio, air flow) is inside the efficiency maps using an algorithm to determine if a point is inside a polygon. Of course, it's a bit more complicated but this is the essence.

Here are the results for an IAT of 40 Celsius (104F) and a pressure drop (intercooler + piping) of 1.5psi:

RPM PSI HP Nm

1300 4.00 55 302
1400 6.50 67 343
1500 15.80 104 493
1600 17.50 117 521
1700 17.60 125 522
1800 17.70 132 524
1900 17.80 140 525
2000 17.80 148 525
2100 17.90 155 527
2200 18.00 163 529
2300 18.10 171 530
2400 18.20 179 532
2500 18.30 187 534
2600 18.40 195 535
2700 18.50 204 537
2800 18.50 211 537
2900 18.60 219 538
3000 18.80 228 542
3100 18.90 237 543
3200 19.00 245 545
3300 19.10 253 546
3400 19.20 262 548
3500 19.30 270 550
3600 19.40 279 551
3700 19.30 286 550
3800 19.20 293 548
3900 19.10 299 546
4000 19.00 306 545
4100 18.90 313 543
4200 18.70 319 540
4300 18.60 325 538
4400 18.50 332 537
4500 18.40 338 535
4600 18.10 343 530
4700 17.70 346 524
4800 17.30 349 517
4900 16.90 352 511
5000 16.50 354 504
5100 16.20 358 500
5200 15.80 360 493
5300 15.50 363 488
5400 15.10 365 482
5500 14.80 368 477
5600 14.50 371 472
5700 14.10 373 466
5800 13.60 373 458
5900 13.00 371 448
6000 12.40 369 438
6100 11.90 368 430
6200 11.30 366 420
6300 10.80 365 412
6400 10.20 362 403
6500 9.70 360 394
6600 9.10 357 385
6700 8.60 354 377
6800 8.20 354 370
6900 7.70 351 362
7000 7.20 348 354
7100 6.80 347 348
7200 6.40 345 341
7300 6.00 343 335
7400 5.60 341 328

Here are the results for IAT of 22 Celsius (74F) - for example if you are using meth - see how the psi is the same, but the max power increases by 24hp:

RPM PSI HP Nm
1300 4.00 59 321
1400 6.50 71 363
1500 15.80 110 523
1600 17.50 124 552
1700 17.60 132 554
1800 17.70 140 555
1900 17.70 148 555
2000 17.80 156 557
2100 17.90 165 559
2200 18.00 173 560
2300 18.10 182 562
2400 18.20 190 564
2500 18.30 199 566
2600 18.40 207 567
2700 18.40 215 567
2800 18.50 224 569
2900 18.60 232 571
3000 18.70 241 572
3100 18.90 251 576
3200 19.00 260 578
3300 19.10 268 579
3400 19.20 277 581
3500 19.30 286 583
3600 19.40 296 584
3700 19.30 303 583
3800 19.20 310 581
3900 19.10 317 579
4000 19.00 324 578
4100 18.90 332 576
4200 18.70 338 572
4300 18.60 345 571
4400 18.50 352 569
4500 18.40 359 567
4600 18.10 363 562
4700 17.70 367 555
4800 17.30 370 548
4900 16.90 373 542
5000 16.50 376 535
5100 16.20 379 530
5200 15.80 382 523
5300 15.50 385 518
5400 15.10 387 511
5500 14.80 391 506
5600 14.50 394 500
5700 14.20 397 495
5800 13.60 395 485
5900 13.00 393 475
6000 12.40 391 464
6100 11.90 391 456
6200 11.30 388 446
6300 10.80 387 437
6400 10.20 384 427
6500 9.70 382 418
6600 9.20 380 410
6700 8.70 377 401
6800 8.20 375 393
6900 7.70 372 384
7000 7.20 369 375
7100 6.80 367 369
7200 6.40 366 362
7300 6.00 364 355
7400 5.60 362 348

Now let's have a tuner push these turbos to the max, it seems to me there is plenty of room in the midrange

[spool twice]

Thanks, Subscribed!

[E92ML]

I'm pretty sure those two charts are exactly the same

[GOTMH8N]

Good stuff!

[NiVeDh]

Both of your datasets are the same.

[cstavaru]

Originally Posted by NiVeDh

Both of your datasets are the same.

That's what came out of the program. But they are not identical, example: at 3000RPM, the 40C set has 18.80 max psi while the 22C set has 18.70 psi.

The IAT does not really influence turbo efficiency because the air is cooled only after it passes the turbocharger, so it really shouldn't play a huge role in establishing the maximum turbo PSI for a given RPM, not saying it doesn't play a huge role in other areas of combustion. So the turbo receives ambient air, and gets out hot air. The IAT has nothing to do with this, it plays a role after this, with the ECU reducing the boost because there is plenty of oxygen due to the denser air. So you can make more power with less boost, but this doesn't mean that the turbos can push more psi at a given RPM.

[E90Company]

Subbed

[tofu-]

i think cobb is already pushing over 18psi in the mid range

[type rrr]

Originally Posted by tofu-

i think cobb is already pushing over 18psi in the mid range

18.7psi for me

[jayzF30]

Anything like this for RB turbos possible?

[Ace_HollyWood]

subscribed

[ianthegreat]

great job

[woosh]

Sweet info mate

[AU335i]

Originally Posted by tofu-

i think cobb is already pushing over 18psi in the mid range

it spikes to ~18.5 but for the most part holds 17.5 in mid-range... the chart looks to be in line with what COBB's Stage 2+ produces to be honest... seems like COBB might have used the same calculations.

[cstavaru]

I have now added maximum power and maximum torque figures. Now you can see how meth helps, there is a 24hp gain from 40C to 22C in IAT.

To be honest, I got these exact numbers on a well calibrated Mustang dyno that I am using. It's amazing how the numbers match.

[Lulz_M3]

How are you calculating VE?

[cstavaru]

Originally Posted by Lulz_M3

How are you calculating VE?

Garrett states that 4-valve heads have a VE of 95%-98% (I used 95%).

[Lulz_M3]

VE is at its peak during peak power on variable valve engines, you cant use the same VE for the entire RPM range, you gotta start with peak VE at peak power output and scale it down with lower RPMS.

[cstavaru]

Originally Posted by Lulz_M3

VE is at its peak during peak power on variable valve engines, you cant use the same VE for the entire RPM range, you gotta start with peak VE at peak power output and scale it down with lower RPMS.

The question is, do you really need super accurate calculations of power at 4000RPM, or are you looking for the most accurate calculations at the RPMs with the maximum power, like 5000-6000RPM, where VE is at its peak anyway ? Also, between 95-98% is a small enough range to not really matter. Likewise with the AFR.

[R1000K3]

Quite interesting information

[Lulz_M3]

Originally Posted by cstavaru

The question is, do you really need super accurate calculations of power at 4000RPM, or are you looking for the most accurate calculations at the RPMs with the maximum power, like 5000-6000RPM, where VE is at its peak anyway ? Also, between 95-98% is a small enough range to not really matter. Likewise with the AFR.

Agreed, i'd be more interested in the actual VE of our engines in NA form, mapped across the entire RPM range.

[Jeff@TopGearSolutions]

Definitely plenty of room in the mid-range. I remember when Cobb first came out everyone was bugging out about seeing 16-17 PSI in the mid-range, its perfectly acceptable for this car so as long as its not at redline.

I had to dial back the boost on the stage 3 PROcede maps, too much torque for the stock clutch on my car. Car is a beast down low.