Intercooler Efficiency

Hey All,

I have started another thread here to chat about intercooler efficiency as some questions have been asked about how well they work.

If you look at Gamers dyno in the following thread the ambient temp is recorded at 21deg C and intake temp is showing as 14.7deg C.

http://www.mkivsupra.net/vbb/showthread.php?t=94693

This suggests the Blitz LM FMIC has reduced the intake temp from ambient by approx 6deg C which I would say is very good.

and i'll add my post and stop cluttering up gamers thread

"cheers i'm just struggling to get how a flow of say 20 degrees ambient air can cool anything to below that temp?

Intake air is heated by being compressed and presumable due to going through a hot turbo/piping etc....... then its cooled by the IC..........does it then expand further cooling it?

Intuitively i would expect that the IC would do no better than get the intake air back to as near to the ambient temp as possible?"

tell me where i've got it wrong please.............i don't care if i have got it wrong just want to know what goes on.........

If the intercooler is cooling the charge to less than ambient temperatures, doesn't that mean the efficiency is >100%?! Whilst the air velocity through the fins would have a cooling effect, I don't see how it can cool greater than ambient temperatures due to 'wind chill' not affecting non-organic materials.

Ah well, that's me subscribed anyway

Bob thats my thinking too..............

This does indeed sound odd.

Hmmm here's a slightly wild thought...what if it's 14degC over ambient? So it's 21+14? would the system do that? That at least would be believable.

Are intake temps of 35-40deg C ok?

It would prob help if we knew were the prob was placed.

Indeed without talking to the operator, I doubt we'll ever know.

35degC in a building would be ok IMO.

What does the dyno do with the figures it gets for intake temp etc, are they used in any of the calculations?

My 2p's worth.

When my car was dyno'd, the temperature probe was placed in the air box, don't think they would have removed bits to fit a probe directly to the intake after the IC.

My 2p's worth.

 

When my car was dyno'd, the temperature probe was placed in the air box, don't think they would have removed bits to fit a probe directly to the intake after the IC.

So in your case ambient and intake temps would be the same.

The dyno printout only had 1 temperature recorded so that must be the case. See here

If the machine had one sensor and a separate probe under the bonnet then you may get this variation depending on where they are in relation to each other, the car may have been outside.

No idea if it was used or not but the I have an air temp sensor mounted on my intercooler piping about 12" before my TB for the Motec.

Its impossible for an IC to cool below ambient so Alex's suggestion is the only plausible one (Unless they got the temp sensors the wrong way round!)

Isn't there a known dodge where some RR operators overstate the true ambient air temp in order for the dyno software to give a more customer pleasing result?

No idea if it was used or not but the I have an air temp sensor mounted on my intercooler piping about 12" before my TB for the Motec.

On or inside the pipe? It would make a huge diff if it's on (ie outside).

Another possible explanation is that the temp sensors are calibrated differently....

Some time ago I spoke to a guy who used to be an engineer for a WRC team, and he told me that once you get the inlet temps down to about 40 degrees, cooling it below that doesn't actually give you a much gain.

On or inside the pipe? It would make a huge diff if it's on (ie outside).

It is inside of the pipe. Let me dig up an old pic ...

You can see the sensor just opposite the small fuse to the far right in this pic

Isn't there a known dodge where some RR operators overstate the true ambient air temp in order for the dyno software to give a more customer pleasing result?

This was posted by a member on LS1 forum :-

I was invited to a dyno demonstration day in recent times.They distinctly said that the air intake temp sensor should be in the intake.If your picking up that amount of heat then you are not recording the incoming air temperature and thus your dyno readouts do the calculations and show a higher dyno reading.

You can see the sensor just opposite the small fuse to the far right in this pic

 

[qimg]http://homepages.nildram.co.uk/~shemesh/Greddy004.jpg[/qimg]

Lovely engine bay dude, you got a full shot, car p0rn

Mine looks like its 30 years old

Cheers mate.

Here is one from a few months ago, I have changed a few things since then. I plan on cleaning up the bay a bit tomorrow and take some pics if the weather holds up.

Very nice

Last time I posted an engine bay shot it was noted that I had some wood holding my battery in place, he he he.

The difference between the temperature of the air coming out the back of the intercooler is always cooler than the charge coming out of the intercooller. In the perfect intercooler the two figures would be the same. However you would need and intercoooler so big you could not fit it in the car. So I am pretty sure the figures on that print out are not a true reflection of what your intercoller was doing.

I am pretty sure the temp reading depends on the probe type. A standard thermo couple will be subject to the cooling effect speed of the air passing the probe, a bit like wind chill. I have seen even bigger differences with my Trust 3 row side mount with the probe in the centre of the TB opening. This is of course impossible. To get a true temperature reading, you have a K type thermo couple.

I dod some heat exchanger calcs recently fr an air/water exchanger. The maths is the same for air/air and its not difficult but unfortunately the formulae rely heavily on knowing a lot about the airflow through the exchanger.

As a bogey figure, I've been told that if you take the vehicle's forward velocity, the airflow through the exchanger is only about 20 of this. MAybe TLicense can add some detail from his F1 work?

If you can get the the mass flow rates pegged (cooling air and cooled air), you can then work out the intercooler effectiveness (which also isn't a constant - it varies as the airflows vary).

One additional complication is that knowing the actual airflow through the IC on a dyno when a cooling fan is used will be very tricky.

I remember some of the thermodynamics stuff I did years ago, but it is all a bit hazy now. I think the difference in temps is call the "approach" but there are a hell of a lot of factors, including IC design, flow rates of both the charge and cooling air, pressure drops, swirl effect inside the IC and loads more The main thing I remember was it would be theoretical possible to get the approach to zero, but the benefits would not justify the cost's. An IC the size of a double deck er bus plays havoc with tire ware.

There are gains to be had by spraying water on the IC as water is a much better conductor of heat than air. If I remember correctly and approach of between 40 and 20 degrees is very good. There is also not much to be gained by going lower.

I never have and never will take much comfort from dyno figures, there are far to many correction factors involved. It the time from A to B which can not be disputed.