2.0 Torque Curves

[engineXI]

how do i get started in this world?

Sponsored

 

[AnnDee4444]

The dot on your compressor map is for a PR of 1.95 perhaps which would be around 14 psi gauge boost - did you use gauge rather than absolute boost?

I think with 22-23 lbs boost (255 kPa absolute) the PR would be in the 2.7-2.8 ball park. There's usually far more pressure loss on the suction side than people realize - about 0.1 bar drop to the compressor. There's also around 0.1 bar drop across the intercooler too but it's on the high side of the equation.

And I'd use 9 hp/lb/min so the dot would be at the end of the first r of garret.

I used numbers I found online for max boost (28 psi IIRC), but this was on an Alfa (different turbo). It was a measured number, not what the ECU reports... but I don't know where the probe was located.

If I understand everything correctly, pressure ratio is basically number of atmospheres, with everything below 1 being a vacuum (where N/A motors live). Converting the absolute pressure number includes everything from complete vacuum instead of how many times the compressor increases the pressure.

Think of this like an air compressor for tires: you don't care about pressure below 1 atmosphere. As far as I know turbo compressor maps work the same way.

https://en.wikipedia.org/wiki/Compressor_map

Edit: related thread https://www.jlwranglerforums.com/fo...peak-boost-on-these-2-0ts.98303/#post-2034450

 

[AnnDee4444]

how do i get started in this world?

What would you like to know? I'd be happy to explain as much as I can.

 

[dstevens]

If I understand everything correctly, pressure ratio is basically number of atmospheres, with everything below 1 being a vacuum (where N/A motors live). Converting the absolute pressure number includes everything from complete vacuum instead of how many times the compressor increases the pressure.

Pressure ratio is the ratio of absolute pressures each side of the compressor. So at 1 atm with some intake drop there is around 0.9 bar on the suction side. Then at 2.6 bar intake manifold pressure (23 lbs) the pressure ratio is around 2.9.

It is very common for people to incorrectly convert 23 lbs boost to 1.56 bar whereas it is actually 2.56 bar absolute. And so the PR would be 1 point too low.

 

[AnnDee4444]

Pressure ratio is the ratio of absolute pressures each side of the compressor. So at 1 atm with some intake drop there is around 0.9 bar on the suction side. Then at 2.6 bar intake manifold pressure (23 lbs) the pressure ratio is around 2.9.

It is very common for people to incorrectly convert 23 lbs boost to 1.56 bar whereas it is actually 2.56 bar absolute. And so the PR would be 1 point too low.

Corrected:

 

[AnnDee4444]

Found what I think might be an official crank HP dyno chart here: https://www.motales.com/engines/straight/hurricane4.php

Note that all other numbers in this thread are wheel measurements.

 

[Odyssey USA]

Found what I think might be an official crank HP dyno chart here: https://www.motales.com/engines/straight/hurricane4.php

Note that all other numbers in this thread are wheel measurements.

It’s kinda odd they didn’t go to 5250 where the tq and hp would normally intersect. If that’s their intersection, seems both curves should shift right 250 rpms.

 

[AnnDee4444]

It’s kinda odd they didn’t go to 5250 where the tq and hp would normally intersect. If that’s their intersection, seems both curves should shift right 250 rpms.

Agreed. I also found the second measurement RPM strange, as it should be 1,500 instead of ~1,250

Even stranger is the 3.6's with the measurement at ~4,100 RPM: https://www.jlwranglerforums.com/forum/threads/3-6-torque-curves.62669/page-4#post-3429560

Sponsored