Looking for intake temperature data (after turbo) on MS3

[jeffmsp]

hey ,

wondering if anyone has ever measured the intake temperatures before the intercooler on the MS3 running ~20psi on the stock turbo, or if there is a link that can calculate the temps of the stock turbo at ~20psi.

Not interested in post IC temps.


thanks for your time, jeff (drinks)

 

[Carl.E]

I haven't seen any actual MS3 data, but a little thermodynamics can help give a pretty good idea of the temperature. Assuming air as an idea gas and that the compression does not add any heat (adiabatic compression):

T_final = T_initial * (P_final/P_initial)^0.2857

Where P is absolute pressure, T is temperature measured in Kelvin, Initial = pre-turbo, and Final = post-turbo.

So for your 20 psi boost case, P_final/P_initial is about 2.36 (34.7/14.7).

Let's assume you have a CAI, so T_initial could be ~80 degrees F (300 Kelvin).

T_final = 300 * 2.36^0.2857

T_final = 383 Kelvin, or 230 degrees F.

Note that you can change your boost pressure and turbo inlet temps to whatever you want to calculate the turbo outlet temp with that equation.
This also shows how much turbo inlet temperature matters, and also why intercoolers are such a good idea. (yes)

 

[jeffmsp]

thank you for your perfect answer. I had a similar equation but i could not get it to work out properly. would it be accurate for temp increase from compressing pre compressed air since I could just add the boost to atmospheric for p initial?

 

[Carl.E]

thank you for your perfect answer. I had a similar equation but i could not get it to work out properly. would it be accurate for temp increase from compressing pre compressed air since I could just add the boost to atmospheric for p initial?

Yep, as long as you know the temperature of the pre-compressed air, you can have any starting pressure you want.

-Carl

 

[jeffmsp]

If I wanted to figure out how much the temperature would increase during compression in the engine, using say the stock MS3 9.7:1 compression, how would I go about doing so?

Say I have 255 degree F intake charge going into 9.7:1?

Any idea what the intake temperature would end up being at Top Dead Center

 

[Carl.E]

Answered your PM asking the same question. For anyone else who's interested; the same equation can be used, just use your new starting temperature and pressure ratio. Also, this compression does not take into account fuel being added in the cylinder, which will probably cool the charge somewhat.

 

[Jays07MS3]

Answered your PM asking the same question. For anyone else who's interested; the same equation can be used, just use your new starting temperature and pressure ratio. Also, this compression does not take into account fuel being added in the cylinder, which will probably cool the charge somewhat.

Plus heat of the combustion chamber adding to temp of the air. Plus, turbos are only so efficient at compressing air. I believe most of them are around 70-80% which means its not adiabatic. So your temps will likely be 20-30% higher than the ideal gas law calculates. And I'm pretty sure that 20psi is quite far outside the efficiency range on our turbos so the heat added will be even greater. If you find a compressor map for the K04 turbo in our cars, you can find the exact efficiency at 20 psi.

But I'm glad to see some people out there crunching numbers and trying to make sense of things. As a engineer I can definitely appreciate it