E90Post
 


Coby Wheel
 
BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > FMIC Causes Increase in Engine Heat?



Reply
 
Thread Tools Search this Thread
      10-24-2007, 12:31 PM   #67
tintivilus
Lieutenant Colonel
tintivilus's Avatar
United_States
26
Rep
1,826
Posts

Drives: E92 335i
Join Date: Sep 2006
Location: Lake County, IL

iTrader: (0)

Garage List
2007 E92 335i  [0.00]
2003 325i  [0.00]
Yes, sure we're digressing, but it's fun

Quote:
Originally Posted by ilia@industry View Post
It's simply the inverse of the same equation. Take a gas like air, and assume it's sitting in a jar.
I think we might be suffering from differing assumptions about the experimental apparatus... the issue I took was with this statement in particular:

Quote:
Originally Posted by ilia@industry
Raising flow velocity increases temperature and pressure.
Are you talking about reducing the delta-V between the intake and output of the IC? The more I read this, the more it sounds like blowing air faster through an IC makes it hotter, which I just can't fathom based on ideal gas law.

If your IC is cooling the charge air (as it should be) the volume entering the IC should be greater than the volume leaving the IC (since reduction of temp yields reduction of volume). This is plain enough. If you increase the velocity of air at the intake (pushing greater volume in a given period of time) then the air at the output will probably be warmer and therefore at higher pressure than before due to transferring less of its energy to the IC... and is this the point you were trying to make that I just misunderstood?

I really don't recall enough of my thermodynamics to judge whether the increase in delta-T will speed up heat transfer enough to cancel out the reduced transfer time due to increased velocity through the cooler. Could any ME's out there chime in on that?
Appreciate 0
      10-24-2007, 01:16 PM   #68
Dascamel
Lieutenant Colonel
Dascamel's Avatar
50
Rep
1,664
Posts

Drives: 2008 e92 M3, 2010 e91 328i
Join Date: Jul 2007
Location: Bakersfield, CA

iTrader: (0)

haha, back to high school chemistry: PV=nRT, don't remember it, google for some fun.

edit
__________________
2008 E92 M3 Jerez Black,DCT,Fox Red ext,Prem,Tech,19", ipod/usb, CF roof and trim
2010 E91 328i Space Gray,Black int, M sport, most options
2007 Montego Blue 335i (retired)

Last edited by Dascamel; 10-24-2007 at 01:17 PM.. Reason: edit: basic two laws of thermodynamics also apply.
Appreciate 0
      10-24-2007, 01:16 PM   #69
IND-Distribution
BimmerPost Supporting Vendor
IND-Distribution's Avatar
10059
Rep
11,087
Posts


Drives: G82 M4 / G87 M2
Join Date: Oct 2006
Location: Chicago

iTrader: (3)

Yep, you've got me now.

Say you're pushing 30CFM through an intercooler and the temp is 20 degrees Celsius. When you go to run 60CFM through the same intercooler setup the temp will be 20+x degrees Celsius.

More than anything, I was explaining the ideal gas law, and how all the variables affect each other. Temperature affects pressure, pressure affects volume, etc...
__________________
IND DISTRIBUTION | 866-963-4520 • INSTAGRAMYOUTUBEFACEBOOKFLICKR
Appreciate 0
      10-24-2007, 01:42 PM   #70
stressdoc
Moderator
stressdoc's Avatar
Dominica
660
Rep
10,865
Posts

Drives: BMW i8; Toy 4runner TRD pro
Join Date: Jun 2005
Location: Waco TX

iTrader: (0)

I hope that the younger set here is getting enthused about thermodynamics and the importance of Physics courses...

The basic idea is that the explosions that take place inside the cylinders of your engine generate heat. Heat is basically a measure of the speed at which molecules are moving around. The faster they are moving, the more energy, the more "push" from expansion that moves the pistons. The explosions are the release of energy from the breaking down of complex hydrocarbon molecules in gasoline/petrol into smaller molecules. There is energy stored in the chemical bonds, and when they are broken, the energy is released. This chemical reaction needs Oxygen molecules, and that is where the function of the IC comes in. Colder air is more dense, it has more O2 molecules in it per unit of volume, because the molecules are not moving as fast. During an intake cycle of your engine, a set volume of air is allowed into the cylinder, along with a set amount of fuel, which the spark ignites and sets off the chemical reaction. The colder the air, the more O2. This can produce more power: if there is more O2, then engine management systems can adjust the amount of fuel accordingly. More fuel, more O2, more chemical reaction, more energy. More O2 may also increase the efficiency of the chemical reaction, resulting in less unburned fuel entering the exhaust. Because fuel entering into the exhaust does not contribute usable power (it's not moving the pistons), but still may generate heat energy if it continues to burn (which it does), then the power / heat ratio diminishes. Hence an IC may decrease engine temperatures if the cooled air results in a more efficient burn (lower EGTs).

An additional factor involves the potential interference of the IC with other cooling systems (water radiator, oil cooler). This depends on the shared airflow. If the IC is placed where the air that it uses to transfer heat (from the intake air compressed by the spinning turbos) via its cooling fins will also flow over the radiators of the other systems, then that raises the heat of the air passing over those other radiators and diminishes their cooling abililty. Hence the concern with placement of the IC so that it does not interfere with the air flow over other cooling systems, and does not 'pre-heat' the air that will flow over them either.

On a related point, all things being equal (that is, the efficiency of the chemical reaction), when you mod your engine to produce more power, that entails more heat production. A piggybacked engine is capable of producing more power, with associated higher levels of heat that need to be dissipated. Similarly, an engine with an IC that enables higher horsepower will have higher cooling demands, but only when the higher power is realized.
Appreciate 0
      10-24-2007, 10:35 PM   #71
IND-Distribution
BimmerPost Supporting Vendor
IND-Distribution's Avatar
10059
Rep
11,087
Posts


Drives: G82 M4 / G87 M2
Join Date: Oct 2006
Location: Chicago

iTrader: (3)

Quote:
Originally Posted by stressdoc View Post
On a related point, all things being equal (that is, the efficiency of the chemical reaction), when you mod your engine to produce more power, that entails more heat production. A piggybacked engine is capable of producing more power, with associated higher levels of heat that need to be dissipated. Similarly, an engine with an IC that enables higher horsepower will have higher cooling demands, but only when the higher power is realized.
Exactly! Well said. I think that's what I said before we got sidetracked from our original topic, and then got sidetracked from the second topic...
__________________
IND DISTRIBUTION | 866-963-4520 • INSTAGRAMYOUTUBEFACEBOOKFLICKR
Appreciate 0
      10-25-2007, 01:24 AM   #72
Orb
Lieutenant Colonel
No_Country
119
Rep
1,764
Posts

Drives: 335
Join Date: Jun 2006
Location: Canada

iTrader: (1)

Quote:
Originally Posted by tintivilus View Post
Yes, sure we're digressing, but it's fun



I think we might be suffering from differing assumptions about the experimental apparatus... the issue I took was with this statement in particular:



Are you talking about reducing the delta-V between the intake and output of the IC? The more I read this, the more it sounds like blowing air faster through an IC makes it hotter, which I just can't fathom based on ideal gas law.

If your IC is cooling the charge air (as it should be) the volume entering the IC should be greater than the volume leaving the IC (since reduction of temp yields reduction of volume). This is plain enough. If you increase the velocity of air at the intake (pushing greater volume in a given period of time) then the air at the output will probably be warmer and therefore at higher pressure than before due to transferring less of its energy to the IC... and is this the point you were trying to make that I just misunderstood?

I really don't recall enough of my thermodynamics to judge whether the increase in delta-T will speed up heat transfer enough to cancel out the reduced transfer time due to increased velocity through the cooler. Could any ME's out there chime in on that?
You gut feeling is right. So much physics have been missed here that it is not worth getting into this. ilia comments seem to on the right track but increasing velocity will not increase pressure. I will use his example. I heat a can and the pressure increases. I vent the heated can and velocity increase while pressure decrease…makes sense I hope.

If anyone is taking this discussion further then start by looking at ALL the properties of this two phase gas.

Orb
Appreciate 0
Reply

Bookmarks


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 09:03 PM.




e90post
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST