My idea to on upgrading SC intercoolers (not heat exchanger)

B8 S4
#1

I posted this is the “how to bleed CPS” thread and no one shot me down. So next step is to get the idea out to more people.

With all this talk about heat soaking our intercooler loop, I can’t stop thinking there must be a way to upgrade the intercoolers with out making it bigger because of the fixed SC casting. So I’ve drawn a crude picture to show my idea. Page 35 of the 3.0t study guide shows a close up of the OEM double pass intercooler. The cold water enters the bottom, gets heated up once, loops around and gets heated up again. The only way I can see to upgrade is to provide 2 paths of cold water.

Basically remove the rear exposed end tank that loops the water around for second pass, and install a port at the end of each pass, to make 2 straight through pipes. Probably be wise to be manufactured from scratch, with preformed fittings built in. Remove supercharger, throttle body, and slide out OEM cores. Slide new cores, with 2 extra preformed fittings to clear the throttle body. Then re plumb to divide 2 parallel loops into 4 parallel loops of cold water. I’m sure some engineering would need to take place to size larger feed pipes to supply loops evenly. The second loop would need to run opposite of first loop to provide consistent temps to all cylinders. I bet to AMS system with large pump would be sufficient.

I don’t see why this couldn’t be fabricated by 034, AWE, or whom ever is already in the game for water to water heat exchangers.

http://audirevolution.net/addons/albums/images/385902510.jpg

Benefits:
Both passes start cold, removing more heat from boosted air. consistantly colder IAT, I imagine at least 25% colder water at intercoolers. Upgrade should actually make more power opposed to just maintaining power. Only way I imagine to gain any significant increase in temp differential fitting in the OEM SC casting

So what do you think? Stupid idea, no benefit? I haven’t been able to discredit my idea yet…

Why does the word “b e n e f i t” not post correctly?.. Strange…

#2

Are you talking stage 3? Because the oem intercooler for the 3.0t are pretty significant. I don’t get the sense that this is an area of weakness.

If you compare them to say the ones on the Apr 1740 kits or the AMD 1900 kit those are a complete joke.

#3

No I’m talking for the OEM SC, all boosted motors can use colder air. I haven’t had any problems yet still being stock, but I would be shocked if there wasn’t an increase in power over the OEM design.

#4

^^ totally off topic, but I have to ask - are you pro or con Bernanke?

#5

I’m not pro fed, but I don’t think he’s any better/worse than any other bureaucrat before (or since). He was the guy when I got into economics… Found a near picture on the Internet with a double faced, double bearded Bernanke, and then name just created itself. I have too much trouble posting pics from iPhone…

#6

Haha gotcha. I don’t want to clog up your thread any further. Ben’s got a blog going now. Some interesting post hoc justifications:

http://www.brookings.edu/blogs/ben-bernanke

#7

Thanks! I’m gonna check that out

http://audirevolution.net/addons/albums/images/199620710.jpg

#8

OK, I’ll bite.

Short Answer:
No. You may lose heat transfer.

I’m not good with short answers, so…

Consider that with a water-to-air heat exchanger, the higher resistance to heat transfer is on the air side, and very low resistance on the water side - any improvements to heat transfer resistance on the water side will see negligible gains. But regardless, you’ve increased resistance to heat transfer on the water side (i.e. worse), by now only supplying half the flow through each pass, and thus reducing the turbulence across the heat exchanger.

ie. if you had 5 gpm through each pass in the original configuration, you now have only 2.5 gpm through each. With the less turbulence inside the exchanger, the fluid has to rely more on conductive heat transfer rather than convection. Losing turbulence inside a heat exchanger is generally bad.

The water side in OEM configuration probably sees only a few degrees C temperature rise through the exchanger. Even if you forced an unlimited supply of ambient temperature water through the exchanger, to the point that the inlet and outlet temperatures are almost the same, you have only gained back a 2 degree C “delta T” across the water side - and consider that the temperature difference from the hot to the cold side is 60 degrees C and beyond at full load. So, ignoring the turbulence issue (say you used a bigger pump to double the flow to keep turbulence the same) you’ve made back a few percent of heat transfer at best.

What do I think would improve this heat exchanger practically?

1.) Cooler fluid supply - the idea of the CPS/coldfront/AMS heat exchanger and larger reservoirs are to ensure the fluid is as cold as possible supplied to the blower intercoolers. That can at least ensure you have ambient temperature fluid going to the manifold, instead of 50C fluid. A reservoir big enough to put ice in may help, but I’ve heard ice generally doesn’t even last through the staging lanes.
2.) More fluid - by increasing the mass of your system, you can delay the heat-up of your system during short acceleration events. Bigger reservoir is better, but obviously at a weight cost.
3.) Water/water wetter. Replacing with straight water is the summer is the oldest trick in the book. It has a more heat transfer capacity than any glycol mix. Putting a bit of water wetter in will help with adding back corrosion inhibition, since you took out the coolant, I’m not sold on any other improvements with water wetter.

I wonder what the APR 1740 intercooler cores look like? The OEM ones look nice (below)…I’m not sure why they didn’t just incorporate the OEM ones in their casting. The APR 1320 ones for the 4.2 looked like relative junk. Maybe that’s a clue to the missing performance :slight_smile:

http://images.tapatalk-cdn.com/15/07/20/ac4125da2416258dee8f2debfd4b4fad.jpg

#9

jspazz did you ever see a picture of the apr cores for the 4.2 just wondering.

I think the the OP has a good idea. But I think to see if its needed you would have to measure temps pre and post core. usually you see more flow and a bigger resivware help first.

#10

So your saying air is harder to cool, than water is to heat? If that were true the intercoolers would need to be much larger than they are. There is no reason to want the water to heat up more, there is no gain to the water heating up, only from the decreased temp of the intercoolers.

In stock form, end of 5th gear the water enters the intercooler at 92 degrees and leaves at 122, creating 140 degree IAT.

So if I had proper flow through my system the highest temp at intercooler heat transfer spot could be 15 degrees lower.

But if that boosted air is touching 122degree water at some point, my design would make it so post intercooling water temp would only be 107, the hottest the water is that IAT temps ever touch…

Heating the water does is no good. Cooling the hot air is all that matters

#11

Let’s say my water slows down some and is a 20 degree differential of water temp pre and post intercoolers, so my incoming water starts at 92, my leaving water is at 112… The hot air is passing over cooler water than stock, all the time…

#12

Sorry for so many posts…
To achieve 100% effiency (coldest IAT) would be to have zero temp rise from pre to post intercooler. That would mean u have the coldest temp possible for all of the IAT to make contact with.

All u care about is the water temp at the point the IAT crosses paths with the intercooler.

#13

Beard, do you have the data? measured the temps?

Are these measured? It helps to have the data, I’m making a spreadsheet for you to use. If you know the flow of the pump, that helps too. My assumption is about 5 gpm per side, 10 gpm total.

#14

The info I used is directly from AMS website. I’m not sure what mods, if any, accompany their test car. So I don’t know the boost psi. I have to look at compressor maps to see pre-intercooler air temps to see the temp diff the OEM unit is capable of.
AMS wasn’t upgrading that so they had no reason to list IC temp differential.
I’m expecting like a 25% larger differential with my idea…
I don’t imagine any way to make an accurate test. But if OEM dropped 40 degrees passing OEM IC, I bet mine would drop 50-60 degrees…
All just educated guesses, assuming I can easily find a way to keep maintain the same/similar gpm through 4 parallel circuits. I suspect that would not be a major problem, more powerful pump (AMS is pretty stout)

#15

Ok. I’ll update the spreadsheet when I get back to my desk, but here’s a quick a dirty heat balance of each side. From here I’ll calculate the log mean temp difference, which would give you the rough benefit of your idea in terms of extra cooling to the intake air (ignoring any difference in flow/turbulence). I have to do extra calcs since this is a cross-flow heat exchanger, so bear with me, had to look that up since I haven’t done this in a while:

http://www.cambridge.org/us/engineering/author/nellisandklein/downloads/examples/example_8.2-1.pdf

http://images.tapatalk-cdn.com/15/09/23/72f14faca192008a8404bcb135380b3c.jpg

To clarify, though - when I say “resistance to heat transfer is higher on the air side than the water side”, that means the biggest hurdle/improvements are on the air side. The easiest visual example of this is: To transfer heat out of water/water you can use a tiny area exchanger. For air to air, you need a massive area exchanger. Mostly this is because of the huge heat capacity of water, 4 times that of air per mass, and density, 1000 times that of air. So improvements made to the resistance to heat transfer on the water side of a water to air exchanger (ie double the flow, etc) are generally minor in effect to the overall heat transfer. Improvements made to the driving force such as supplying cooler water in the first place will make bigger improvements - and temperature is your driving force for heat transfer.

If the AMS numbers are right, ie 30F temp difference in/out on the water side, then there will be improvements and you’re onto something by making it a single pass exchanger. If there’s only 2-5 degrees in/out difference, then not so much. But if those are the numbers, I change my position :slight_smile:

#16

No I haven’t seen the 1740 heat exchangers yet - I saw the APR/harrop 1320 and they looked junk. OEM Audi ones looks decent…

Any pics?

#17

5 gpm is lo I like a garden hose. No way it’s any higher than that…
Stage 3 IC

http://audirevolution.net/addons/albums/images/984401185.jpg

http://audirevolution.net/addons/albums/images/853453368.jpg

#18

that looks tiny. The pic gives it more perceived depth because it was cut on the bias

#19

Thanks for the pics. Looks really similar to the Audi units. In fact they have 8 plates instead of 9 on the OEM. If they are not bigger, then why didn’t they just make the castings to fit the Audi units? Or better question, why not just make them bigger? Taller, especially, they can afford some pressure drop with the monster blower.

Anyhow, the results are in: 4 deg C lower air temp for the “beard” flow unit.

http://images.tapatalk-cdn.com/15/09/23/a534ee0eb504bb7e80a03185a1ef0a23.jpg

It’s worth noting two things:
1.) the beard design would be plumbed a lot easier if it simply fed both from the front, and returned from the back. The difference in front to back cylinder temps would be negligible with enough flow.
2.) if we simply fed double the flow to the OEM design (if it’s possible with pressure drop), we would come to the same result - 4 degrees C lower air temp.

#20

Wow, it’s gonna take a while for me the figure out that spread sheet, try and verify it, but that’s some nice work…I reached out to a friend who thinks like u…

I think you would need serious flow to have a negligible temp differential between cylinders, to provide a straight trough cooler, but that would be much simpler. I’ve heard some complaints about the sound of the AMS pump as it is. But your way would be the absolute coldest IAT. My design would be more complicated but quieter, it would look like the OEM setup, just on front and back.

Another hurdle would be how and when to turn on the pump. tony from EPL says he can adjust the 122 degree pump on switch. I read somewhere in the study guide that too cold of loop water made the pump struggle, doubt that would be complicated compared to implementing the hardware, but gotta think ahead…

The intercoolers gotta be a serious air restriction, raising PSI which means raising heat. If what u say is true, and we drop IAT by 39f (4c) then maybe we can reduce some of the aluminum heat sinks while we are at it, and physically cram more air in less PSI and even further drop IAT…