[cstavaru]

Hi,

EDIT: I have added maximum horsepower / maximum torque figures. You can now see how the use of meth increases power by ~25hp.

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:

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 BMS push these turbos to the max, it seems to me there is plenty of room in the midrange

[Landman]

Those seem to be the same numbers. Are you saying there is no difference between 104* and 74*?

[aoschadlin]

Originally Posted by Landman

Those seem to be the same numbers. Are you saying there is no difference between 104* and 74*?

There seems to be very subtle differences, but I agree I would have expected a greater difference with that much temperature range.

[Landman]

Actually, now that I have actually put some thought into it, the numbers make sense. The air leaving the turbos is much hotter than the 100+* stated above so in regards to the OP's conclusions the intake air has little affect. This is solely the efficiency of the turbos. Good info, thanks.

[boostaholic]

Agreed

[drfrink24]

This assumes bone stock intake and exhaust? All else being equal, suppose one car has a downpipe w/o cat, would these values increase, or are they assuming max system efficiency already?

[MathR601]

As well as the DCI

Originally Posted by drfrink24

This assumes bone stock intake and exhaust? All else being equal, suppose one car has a downpipe w/o cat, would these values increase, or are they assuming max system efficiency already?

[cstavaru]

I have added maximum horsepower / maximum torque figures. You can now see how the use of meth increases power by ~25hp.

[drfrink24]

Originally Posted by cstavaru

I have added maximum horsepower / maximum torque figures. You can now see how the use of meth increases power by ~25hp.

I assume these numbers are brake HP, unless you factored in drive train losses. In which case, they seem low across the board vs. numerous real and virtual dynos.

Even actual trap speeds with full weight cars are showing to be in the upper 400s

[cstavaru]

Originally Posted by drfrink24

I assume these numbers are brake HP, unless you factored in drive train losses. In which case, they seem low across the board vs. numerous real and virtual dynos.

Even actual trap speeds with full weight cars are showing to be in the upper 400s

These numbers are based on those boost values such that the turbos remain in the efficiency range. Maybe some people use higher boost levels (pushing turbos out of their efficiency range) and get a bit more power.

They seem low because people are using Dynojets and few people are using well calibrated Mustangs. For example, I got exactly 390hp (332whp) at my last dyno session with GIAC Stage 2 Race on a Mustang (and I kept up with a JB4 map 7 FBO + meth a night before). And the most I got on that Mustang was 356whp. This map has 13.5psi at 5800RPM, exactly like in those calculations.

[drfrink24]

Originally Posted by cstavaru

These numbers are based on those boost values such that the turbos remain in the efficiency range. Maybe some people use higher boost levels (pushing turbos out of their efficiency range) and get a bit more power.

They seem low because people are using Dynojets and few people are using well calibrated Mustangs. For example, I got exactly 390hp (332whp) at my last dyno session with GIAC Stage 2 Race on a Mustang (and I kept up with a JB4 map 7 FBO + meth a night before). And the most I got on that Mustang was 356whp. This map has 13.5psi at 5800RPM, exactly like in those calculations.

4000lb cars are trapping 115+. If they are pushing their cars past their effective range, they're still picking up 50+ whp.. which if you can pickup 50whp or more past their range, one has to question if these maps are conservative.

Can you run new numbers that reflect the diminishing returns as you move well past their ranges? I know at some point EGTs rise with no HP increase, be interesting to see those numbers in theory.

[Vorsprung_CJB]

Are these calculations for a single TD03 turbo on a 3-cylinder bank or for the two in tandem as on the N54? I would guess there are special calculations for that.

[cstavaru]

Originally Posted by Vorsprung_CJB

Are these calculations for a single TD03 turbo on a 3-cylinder bank or for the two in tandem as on the N54? I would guess there are special calculations for that.

These calculations are for the two turbos in tandem. The calculations are indeed different. There are a few areas in the equations where you have to consider that there are 2 turbos, but it's pretty much intuitive and straightforward to adapt from one to two turbos.

[rudypoochris]

These numbers make sense to me. I think the OP is not stating that you cant make more power than this - you can. You're just driving the turbos out of their efficiency range. Basically if you're trying to make more than those HP/boost numbers you would be better off with a larger turbo. If you are trying for much more than those numbers you're going to be driving the turboa you have too hard.

BMW didn't just size the turbos with an extra 100hp in them for fun. We are picking up this extra HP by droving the turbos into a less efficient range.

[Terry @ BMS]

It's important to have a solid understanding of the theory and this post is great for that but I've always put as much or maybe more weight in physical observations. And we've been running say 11psi @ 7000rpm now for several years with good results.

In terms of midrange boost remember advance plays a large role. As I've said in the past we've tested big midrange boost pump maps, even posted some (they require CPS), and I think they are great for marketing (18psi on pump gas yo), but we've found the same and often better performance running 12-13psi in the midrange with more advance. Now with race gas, E85, or meth, where octane is not a limiting factor, then yes there is plenty of room to crank up torque if one is so inclined. We've made as much as 500wtq on the OEM turbos @ 18psi + 10-12 degrees @ ~3500rpm using meth. Map 3 is actually fairly aggressive down there at higher additives. A 75 additive will target 18.5psi @ 3500rpm.

[cstavaru]

Originally Posted by Terry @ BMS

It's important to have a solid understanding of the theory and this post is great for that but I've always put as much or maybe more weight in physical observations. And we've been running say 11psi @ 7000rpm now for several years with good results.

In terms of midrange boost remember advance plays a large role. As I've said in the past we've tested big midrange boost pump maps, even posted some (they require CPS), and I think they are great for marketing (18psi on pump gas yo), but we've found the same and often better performance running 12-13psi in the midrange with more advance. Now with race gas, E85, or meth, where octane is not a limiting factor, then yes there is plenty of room to crank up torque if one is so inclined. We've made as much as 500wtq on the OEM turbos @ 18psi + 10-12 degrees @ ~3500rpm using meth. Map 3 is actually fairly aggressive down there at higher additives. A 75 additive will target 18.5psi @ 3500rpm.

I didn't say you can't run more psi and make more power. It's just that is not in the turbine efficiency range. My calculations are done such that the turbos are always in the efficiency range.

[R1000K3]

Originally Posted by cstavaru

I didn't say you can't run more psi and make more power. It's just that is not in the turbine efficiency range. My calculations are done such that the turbos are always in the efficiency range.

What is the exact definition of efficiency range in your calculation?

[Terry @ BMS]

Originally Posted by cstavaru

I didn't say you can't run more psi and make more power. It's just that is not in the turbine efficiency range. My calculations are done such that the turbos are always in the efficiency range.

Makes sense to me. You can monitor IAT under various boost curves and draw some conclusions that way as well.

[Milwaukee135]

This is a bit off-topic for this thread, but here goes:

I have been wondering for quite some time how much horse power is needed to run the turbos as boost is added.

As I understand the situation, turbos are more efficient because they do not lose inertia all over the place like a reciprocating crankshaft piston setup and you can better control the pressure loss (pushing pistons to high hp only makes sense to a certain not-too-low pressure at exhaust valve open).

So here's my question: Can the power used to run the turbos (otherwise wasted as exhaust by the engine or not) to sustain a given psi at a given rpm be easily described in terms of horsepower?

Does someone have such a chart, I'm really asking.

I would say that if we could compare that to the potential hp gain due to the increased air, we'd have an interesting number about the efficiency of the turbine vs the piston engine.

(Obviously a jet turbine engine is the best case, but somehow we just can't grapple with putting them in cars -- tanks, trains and ships sure, but not cars.)

[az335iat]

Google "air compressor hp". This will list several sites that will calculate HP required..... in the range of 30Hp.

[Milwaukee135]

Makes sense.

Thanks.

[Ian]

Originally Posted by Landman

Actually, now that I have actually put some thought into it, the numbers make sense. The air leaving the turbos is much hotter than the 100+* stated above so in regards to the OP's conclusions the intake air has little affect. This is solely the efficiency of the turbos. Good info, thanks.

Yes it is, but the turbos are X efficient, which means intake temp in = some discharge temp out... This is of course effected by the intercooler. I'm not even sure how the system works... Does the air get cooled prior to the turbos or after compression?

The turbos are only capable of a certain head, the wastegates effect this obviously, but the principles are still the same.