[vasillalov]

Typical physicists! They'll give you a 10 paragraph explanation in their language but they won't summarize it in a language that the average person can understand it.

GeorgiaTech,
can you translate some of that into a for that's more easily palatable for the rest of us?

[Will335i]

This thread makes me what to dig out my Heat Transfer book.

Props to both Overboost and Bmwguy11 on great write ups.

Guys please correct me if I am wrong but the take away for those that don't have an engineering back ground the lower the starting temp the lower final temp. While in some applications this might not be significant, like Bmwguy11 stated if you are looking for every last pony you want to go with a set up gives you the lowest inlet temp.

happykn8er, its been a few years since I was in heat transfer but is the flat plate heat exchanger the proper model for the ICs on our cars? Also what material are you using in your modeling? I believe that will affect the efficiency.

[vasillalov]

Originally Posted by Will335i

Guys please correct me if I am wrong but the take away for those that don't have an engineering back ground the lower the starting temp the lower final temp.

Bingo!

That is of course considering that you are providing sufficient flow to the turbos.

[GeorgiaTech335coupe]

Originally Posted by vasillalov

GeorgiaTech,
can you translate some of that into a for that's more easily palatable for the rest of us?

Someone wanted to know the temp rise between the entering and exiting air of the turbo. This equation gives a good approximation.

To make it easier, this is the relationship in degree F: T2 = 1.22*T1 + 101.2

This assumes that heat is not transferred from the anywhere else into the air while being compressed.

[vasillalov]

Originally Posted by GeorgiaTech335coupe

Someone wanted to know the temp rise between the entering and exiting air of the turbo. This equation gives a good approximation.

To make it easier, this is the relationship in degree F: T2 = 1.22*T1 + 101.2

This assumes that heat is not transferred from the anywhere else into the air while being compressed.

Thanks. So this is the minimum amount of heat rise that occurs JUST from compression. We also have heat being added to the intake charge by simple matter of air passing through the super hot turbos.

[GeorgiaTech335coupe]

Originally Posted by Will335i

Guys please correct me if I am wrong but the take away for those that don't have an engineering back ground the lower the starting temp the lower final temp. While in some applications this might not be significant, like Bmwguy11 stated if you are looking for every last pony you want to go with a set up gives you the lowest inlet temp.

Simplistically, yes. But, (there always is a but) heat transfer is easier when the difference between the hot source and the cold source is greater. This means that, although the DCI is playing catch up to the stock box, it is losing heat at a greater rate thru the IC and on its way to the intake manifold.

Another thing to factor in is that the DCI at higher boost pressures allows the turbos to work more efficiently, creating less heat. More heat created by the turbos is more heat that is transferred into the compressed air during compression.

The question is, with the advantage of greater heat transfer and less heat absorbed through the turbo, does the DCI air temp get close enough or even catch and maybe pass the stock box temperature by the time it enters the intake manifold? My gut tells me it is probably very close. Close enough that it is worth the increased efficiency of the turbos that the DCI brings.

[Overboost]

Welcome GeorgiaTech335coupe... feel free to correct any mistakes I may have made. Wrote this off teh top of my head in a few mins. College physics and Chemistry only take it so far.

We've seen 4% max increase in duty cycle on the stock intake from the Mr.5 vbox thread but very close results with average vbox times. 4% doesn't seem like a lot.

[Overboost]

Also to add to the above.I think there was no increase or maybe even a slight decrease in duty cycle with the Mr.5 intake

[Overboost]

Originally Posted by Will335i

This thread makes me what to dig out my Heat Transfer book.

Props to both Overboost and Bmwguy11 on great write ups.

.

Please Do

[Will335i]

Originally Posted by GeorgiaTech335coupe

Simplistically, yes. But, (there always is a but) heat transfer is easier when the difference between the hot source and the cold source is greater. This means that, although the DCI is playing catch up to the stock box, it is losing heat at a greater rate thru the IC and on its way to the intake manifold.

Another thing to factor in is that the DCI at higher boost pressures allows the turbos to work more efficiently, creating less heat. More heat created by the turbos is more heat that is transferred into the compressed air during compression.

The question is, with the advantage of greater heat transfer and less heat absorbed through the turbo, does the DCI air temp get close enough or even catch and maybe pass the stock box temperature by the time it enters the intake manifold? My gut tells me it is probably very close. Close enough that it is worth the increased efficiency of the turbos that the DCI brings.

Right, the greater the deltaT the greater percentage of heat transfer and will decrease as the system reaches equilibrium deltaT = 0. I was just putting it in very simple terms.

It would just be easier if everyone was an engineer. HAHA

[max]

Originally Posted by GeorgiaTech335coupe

Simplistically, yes. But, (there always is a but) heat transfer is easier when the difference between the hot source and the cold source is greater. This means that, although the DCI is playing catch up to the stock box, it is losing heat at a greater rate thru the IC and on its way to the intake manifold.

Another thing to factor in is that the DCI at higher boost pressures allows the turbos to work more efficiently, creating less heat. More heat created by the turbos is more heat that is transferred into the compressed air during compression.

The question is, with the advantage of greater heat transfer and less heat absorbed through the turbo, does the DCI air temp get close enough or even catch and maybe pass the stock box temperature by the time it enters the intake manifold? My gut tells me it is probably very close. Close enough that it is worth the increased efficiency of the turbos that the DCI brings.

I can't agree with this. The turbine compressor is more efficient if it had very little temp change across it, not the other way around as you stated. In engineering terms adiabatic compression is more efficient than isotropic compression.

If you research the history of water/alcohol injection you'll find that back in the old days (WW2) they quite often sprayed into the eye of the compressor wheel or immediately upstream to take advantage of increasing the efficiency of the compressor by cooling the inlet temp thus cooling the outlet temp. This allowed them to increase boost even more since the compressor wasn't fighting (wasting energy) heating the charge air up.

In actuality, this spraying before the compressor is like shifting the compressor map and allows us to run even higher boost without compressor surge, and allows safe operation of the compressor within it's new range at a lower RPM for a given amount of boost pressure.

I wonder, is there anyone out there spraying before the compressor to take advantage of this?

[vasillalov]

Originally Posted by max

I wonder, is there anyone out there spraying before the compressor to take advantage of this?

Spraying before the compressor has its disadvantages though... You need to make sure that the entire water/meth injection system is functioning correctly all the time. The last thing you want is droplets hitting the compressor wheel which is spinning at very high speed.... I've seen some compressor wheel fins bent out of shape because of a dripping nozzle.

[samchoi604]

Absolutely great write up, OverBoost, and I completely agree with everything you've said. If DCI were effective across all temperatures, and provided good benefits, you have to wonder why car manufacturers don't use them in the first place.

[anerbe]

It's always fun reading all these posts.

Everyone has a ton of theoretical information with ideal conditions.

Unfortunately, in real life, there are so many components that effect the condition of the air before entering in the combustion chamber, answering the question of mod vs. HP increase is too complex. It also has to do whether the engine software targets boost or load to determine the effect of a modification on a vehicle.

During the design of a complete PTC module (including the Charge Air path), an iterative analysis is conducted on all components, paths, restrictions, heat sources and exchangers to come up with both a transient and steady state result. Most of the theoretical discussions in this thread are too theoretical with ideal conditions and assuming a particular snipet of time as steady state. What's better? Higher IAT with lower restriction or lower IAT with higher restriction? The answer isn't so simple. What is the condition of the system during the test? Cold? Hot? Air conditions?

Most sizing of powertrain systems are done with a real world condition in mind. Pulling a trailer up a grade, consistent lap times at a track, etc.. are used to spec out a powertrain, not for increase in HP during a snapshot in time.

Lowering IAT's while maintaining the same restriction in any part of the flow path will drop temps/raise density of the air creating more power. However, the temp difference between a stock box and an CAI is very low compared to the effects of the CAC/IC due to the dT comparing the turbo outlet temp vs. ambient air. The real benefits of a new intake is to reduce restriction in airflow. However, if the stock intake does not see airflow rates outside of it's efficiency range, swapping to a different intake will yield minimal results. Best way to analyze this is thru flowbench testing or A/B comparisons at a dyno (which has been done). Testing so far has shown that the stock intake is indeed a great system in itself, and more benefits can be seen upgrading the CAC. CAC/IC's are indeed a great bang for the buck and are often at higher efficiencies with large dT and relatively small dPs. It's often the case that fitting a high performing CAC/IC can more than offset the lower efficiencies of a turbocharger.

Turbos are rated in efficiency at 100% if the charge process is adiabatic. The more the air is heated post turbo above the temp calculated by adiabatic compression, then the less efficient the turbocharger is. Turbochargers often have the highest efficiency range somewhere in the middle of the RPM operating range, lower than the choke and surge limits. Also note that the efficiency of a turbo cannot be calculated based off the air pressure found at the CAI site. This pressure will be different than the compressor inlet (which is the important bit). The mass flowrate will be the same.

ME here, worked 4 years for a German Auto Climate Systems Tier 1 supplier in Powertrain Cooling.

[Bash]

Ok this thread started out easy enough, ended in lots of words in chinese lol

[Overboost]

Originally Posted by anerbe

It's always fun reading all these posts.

Everyone has a ton of theoretical information with ideal conditions.

Unfortunately, in real life, there are so many components that effect the condition of the air before entering in the combustion chamber, answering the question of mod vs. HP increase is too complex. It also has to do whether the engine software targets boost or load to determine the effect of a modification on a vehicle.

During the design of a complete PTC module (including the Charge Air path), an iterative analysis is conducted on all components, paths, restrictions, heat sources and exchangers to come up with both a transient and steady state result. Most of the theoretical discussions in this thread are too theoretical with ideal conditions and assuming a particular snipet of time as steady state. What's better? Higher IAT with lower restriction or lower IAT with higher restriction? The answer isn't so simple. What is the condition of the system during the test? Cold? Hot? Air conditions?

Most sizing of powertrain systems are done with a real world condition in mind. Pulling a trailer up a grade, consistent lap times at a track, etc.. are used to spec out a powertrain, not for increase in HP during a snapshot in time.

Lowering IAT's while maintaining the same restriction in any part of the flow path will drop temps/raise density of the air creating more power. However, the temp difference between a stock box and an CAI is very low compared to the effects of the CAC/IC due to the dT comparing the turbo outlet temp vs. ambient air. The real benefits of a new intake is to reduce restriction in airflow. However, if the stock intake does not see airflow rates outside of it's efficiency range, swapping to a different intake will yield minimal results. Best way to analyze this is thru flowbench testing or A/B comparisons at a dyno (which has been done). Testing so far has shown that the stock intake is indeed a great system in itself, and more benefits can be seen upgrading the CAC. CAC/IC's are indeed a great bang for the buck and are often at higher efficiencies with large dT and relatively small dPs. It's often the case that fitting a high performing CAC/IC can more than offset the lower efficiencies of a turbocharger.

Turbos are rated in efficiency at 100% if the charge process is adiabatic. The more the air is heated post turbo above the temp calculated by adiabatic compression, then the less efficient the turbocharger is. Turbochargers often have the highest efficiency range somewhere in the middle of the RPM operating range, lower than the choke and surge limits. Also note that the efficiency of a turbo cannot be calculated based off the air pressure found at the CAI site. This pressure will be different than the compressor inlet (which is the important bit). The mass flowrate will be the same.

ME here, worked 4 years for a German Auto Climate Systems Tier 1 supplier in Powertrain Cooling.

Only a few of us can understand what you just wrote. I chose to write in such a way that everyone could understand. Makes it a bit harder when doing so. Your comments are appreciated. Think of it like recording a film. Its made up of frames or snapshots that when but in motion creates the movie.

[GeorgiaTech335coupe]

Originally Posted by max

I can't agree with this. The turbine compressor is more efficient if it had very little temp change across it, not the other way around as you stated. In engineering terms adiabatic compression is more efficient than isotropic compression.

If you research the history of water/alcohol injection you'll find that back in the old days (WW2) they quite often sprayed into the eye of the compressor wheel or immediately upstream to take advantage of increasing the efficiency of the compressor by cooling the inlet temp thus cooling the outlet temp. This allowed them to increase boost even more since the compressor wasn't fighting (wasting energy) heating the charge air up.

In actuality, this spraying before the compressor is like shifting the compressor map and allows us to run even higher boost without compressor surge, and allows safe operation of the compressor within it's new range at a lower RPM for a given amount of boost pressure.

I wonder, is there anyone out there spraying before the compressor to take advantage of this?

You either didn't read what I said or misunderstood. We both agree. More efficiency = less heat absorbed into the charge air or temperature change as you stated. This means the compression is closer to being adiabatic, as no external heat transfer is done to the air and the only temperature change is through compression.

[GeorgiaTech335coupe]

Originally Posted by anerbe

It's always fun reading all these posts.

Everyone has a ton of theoretical information with ideal conditions.

Unfortunately, in real life, there are so many components that effect the condition of the air before entering in the combustion chamber, answering the question of mod vs. HP increase is too complex. It also has to do whether the engine software targets boost or load to determine the effect of a modification on a vehicle.

During the design of a complete PTC module (including the Charge Air path), an iterative analysis is conducted on all components, paths, restrictions, heat sources and exchangers to come up with both a transient and steady state result. Most of the theoretical discussions in this thread are too theoretical with ideal conditions and assuming a particular snipet of time as steady state. What's better? Higher IAT with lower restriction or lower IAT with higher restriction? The answer isn't so simple. What is the condition of the system during the test? Cold? Hot? Air conditions?

Most sizing of powertrain systems are done with a real world condition in mind. Pulling a trailer up a grade, consistent lap times at a track, etc.. are used to spec out a powertrain, not for increase in HP during a snapshot in time.

Lowering IAT's while maintaining the same restriction in any part of the flow path will drop temps/raise density of the air creating more power. However, the temp difference between a stock box and an CAI is very low compared to the effects of the CAC/IC due to the dT comparing the turbo outlet temp vs. ambient air. The real benefits of a new intake is to reduce restriction in airflow. However, if the stock intake does not see airflow rates outside of it's efficiency range, swapping to a different intake will yield minimal results. Best way to analyze this is thru flowbench testing or A/B comparisons at a dyno (which has been done). Testing so far has shown that the stock intake is indeed a great system in itself, and more benefits can be seen upgrading the CAC. CAC/IC's are indeed a great bang for the buck and are often at higher efficiencies with large dT and relatively small dPs. It's often the case that fitting a high performing CAC/IC can more than offset the lower efficiencies of a turbocharger.

Turbos are rated in efficiency at 100% if the charge process is adiabatic. The more the air is heated post turbo above the temp calculated by adiabatic compression, then the less efficient the turbocharger is. Turbochargers often have the highest efficiency range somewhere in the middle of the RPM operating range, lower than the choke and surge limits. Also note that the efficiency of a turbo cannot be calculated based off the air pressure found at the CAI site. This pressure will be different than the compressor inlet (which is the important bit). The mass flowrate will be the same.

ME here, worked 4 years for a German Auto Climate Systems Tier 1 supplier in Powertrain Cooling.

Exactly. This would be nearly impossible to prove one way or another using equations without multiple sensors, a ton of data and a fun algorithm. The answer will have to be discovered emprically. We have seen results showing that each outperforms the other. Couple that with the inconsistent nature of this car and that is why I believe the differences are very small, at least at tune only power. At 18+ lbs of boost I believe the stock box falls short to DCI. From one ME to another.

[Overboost]

Originally Posted by GeorgiaTech335coupe

Exactly. This would be nearly impossible to prove one way or another using equations without multiple sensors, a ton of data and a fun algorithm. The answer will have to be discovered emprically. We have seen results showing that each outperforms the other. Couple that with the inconsistent nature of this car and that is why I believe the differences are very small, at least at tune only power. At 18+ lbs of boost I believe the stock box falls short to DCI. From one ME to another.

I think the big problem with the stock box is that after the air passes through the filter it basically has to do a 180* turn back down into the turbo inlet tubing. You engineers should know better than any of us how sharp turns affect flow. Wonder what the difference would have been if BMW mounted the filter vertically (or even diagonally to increase area) instead of horizontally, to reduce the change in direction.