Chilled intake...?

[Dougal]

Mathematics isn't my storng suit so I'm at a disadvantage. I can visualize & understand things like theoretical physics and thermodynamics but I fall down at calculations. That said:

Seems you're looking at a linear relationship when in fact it's an exponential increase. Going along with what Octamog describes: You chill the air for more density as in more air. That allows more fuel injected which means more exhaust expansion to spin the turbo, which means more fuel can be added again, which gives more boost.

The horsepower draw of compresor is constant but the ductwork containing the regrigerant piping can have various cross sectional areas, potentially allowing more airflow. As long as the refrigerant can keep removing latent heat the numbers can keep going up.

So a guy would have to know how much latent heat may be exchanged in a given size of ductwork under a given boost pressure and according to which refrigerant is used and also the length of the column the refrigerated air is traveling in for what length of time. Longer column means a potential of more cooling. More fuel means more air which means a longer column but same amount of horsepower loss driving compressor.

I don't think it's a linear relationship but rather one of exponential increase. Make sense?

Using the ideal gas law to predict changes in density from changes in temperature.
PV=NRT.
We're changing T, which changes V.
V= T*NR/P (NR/P is constant for this case).
V = T* constant

Volume change with temperature change is indeed linear.

I tried to make my own air/water intercooler once using 2.5m of 3/8" copper tube wound in a spiral.
Measured the efficiency of it at 15% when working with an 80 deg C temp difference.

You need some serious working area to get a good performing heat exchanger with low temperature gradients.

[Dougal]

I wonder if you could convert a water after cooler to a refrigerant evaporator? To me, you would want your refrigerant powered cooler to be right on top of the engine.

Also, about the 20C to 0C cooling, I think you are in the wrong temp range. I have not hard data, but am willing to bet that compressed charge air is in the 30C-100C range depending on ambient air temperature and boost pressure. I say this because if an air to air cooler makes a difference on a 110F Texas summer day, than the intake air has to be damn hot.

Also, if the air conditioner can pull that same 110F air in from outside and have it at 50-60F when it comes out the ait ducts, I think it has some cooling potential.

Now, will someone build it already so we can quit hypothesising and get some facts, already!

I was using the 20C range to indicate cooling air from ambient to below ambient. This temp range only exists at your air intake before the turbo.

There's no point using refrigeration to cool boosted air, as you, I and the others know that's over 100C for 15psi. There's no point using engine power to run a refrigeration system when a completely passive intercooler can be used to strip that heat down close to ambient without requiring whole kilowatts from the engine.

[Dougal]

One more consideration: various refrigerants have different operating temperatures so a freezer type refrigerant is more desireable than A/C refrigerant. From a scalded memory, R601 or somesuch is for deep freeze and maybe there's stuff that's even better.

There are serious safety concerns using freon based refrigerants in a place where they could be ingested into the engine and burned.

IMO the only suitable refrigerants will be hydrocarbon based.

[Dougal]

Both types of intercoolers have their pluses and minuses. Air-to-air are typically more efficient and don't heat soak, as there is a (seemingly) endless supply of coolant (fresh air). They require less mechanics -- no pumps, plumbing or coolant. Then again, they aren't very efficient at very low speeds as they require air speed to work.

That's why someone invented fans.

[Octamog]

There's no point using engine power to run a refrigeration system when a completely passive intercooler can be used to strip that heat down close to ambient without requiring whole kilowatts from the engine.

That's why someone invented fans.

Ah... but it's not completely passive then, is it?

[Octamog]

This comes from someone who is way more knowledgeable about intercoolers than I, and has a bunch of data and experience to back it up.

AGAINST -

Complexity & Cost. You need a second radiator, water pump & preferably some form of pump speed control, 2 speeds will do the trick. They are much harder to size, this is why we have pumped hundreds of hours into data logging & creating a sizing spreadsheet programme. Under the same circumstances, drive in/out will be approx. 20 to 60% dearer.

It also became apparent after a couple of years testing that I had to down grade my initial cooling estimates of air/water intercooling, which is a disappointment, but necessary. I thought that I could design a system that at speed, would cool the charge air within 4ºc of a front mount - both systems being equally engineered. It appears 8 to 12 ºc is a real world figure. Please put this into perspective. A 'front mount' car - Skyline GTR, 180 - 200 Sx, Supra etc. will give results on a 25ºc day of 31 - 36ºc into the plennum. An air/water setup will give 42 - 48ºc under the same circumstances, but a 'non front mount' car - Skyline GTS-t, VL Commodore, Subaru - any car that doesn't have a front facing throttle body towards the radiator support - will give similar temps. due to heat soak in the long return pipe from under bonnet heat - approx 70 + ºc, even though the charge air in both air/air setups, exits the 'cooler at 31 - 36ºc.

FOR --

Now, the above paragraph is the only time a front mount will out perform an air/water if both are set up properly - at speed . Stop/start, drag racing, towing, 4 x 4 offroad etc. all gain from air/water. The charge air temps. into the engine are also much more stable with logging showing a spread of 35 to 40ºc around town & 35 to 50ºc laden in soft sand, 2nd gear low range, whereas, front mounts have logged 30 to 65ºc around town & 30 to 95ºc in sand. This is with turbo outlet temps of 140ºc as for a top mount, 38ºc c to 116ºc have been recorded ! When you have your foot right into it at slower speeds is when detonation is most likely to happen, air/air intercooling is performing at it's worst efficiency. A very big fan under a top mount will make a fair difference & to a lesser extent, behind a front mount, but none can get near the fact that water 'holds' heat 37 times better than air & a thin radiator at the front of a vehicle cools better than a thick intercooler (air flow), & also has much less effect on the volume of air flow too the engine radiator - very important with some vehicles - eg. 70 series Landcruisers.

from here: http://www.are.com.au/feat/techt/airwaterinter.htm

Also some interesting graphs from Kenne-Bell and a Laminova cored intercooler here: http://www.kennebell.net/techinfo/ma...no-results.pdf

(just to spur some dialogue)

[JimmieD]

A Laminova cored intercooler as shown wouldn't work in my vehicle. I'd never get it off the coffee table and if I did I'd take it in to snuggly up with at night! That's downright porn, boy, downright porn I tell ya! I'd have to buy 3, one for the coffee table, one for next to my pillow and one for the truck......

[JimmieD]

BTW: one heck of a build dialogue at that link, Octamog! Very interesting and one resourceful guy. I always envy clever machinists being more of a mechanic/fabricator myself.

Also thanks to everyone for some really great contributions to this thread and to Dougal for 'doing the math'

[nexxussian]

Octamog, that's a nice lookin' cooler you posted.

Here's a thread with some pictures of a somewhat different setup for them.

http://www.4btswaps.com/forum/showth...nova#post48331

[matt.mcinnes]

Or like this

MaverickTD42 our latest creation.



Were working on a BMW at the momment



Bush65 Monster 8 core

[Dougal]

For those who don't know what Matt's on about.
Those are four laminova air/water intercooler cores fitted to a modified intake manifold.
That particular one (TD42) is for a 4.2 litre 6 cylinder nissan turbo diesel.

Results on his completed projects are very impressive (so is the workmanship), but they're still expanding their scope of vehicles and engines.

[matt.mcinnes]

Results on his completed projects are very impressive (so is the workmanship), but they're still expanding their scope of vehicles and engines.

My tried and tested one just prior to installing the water fittings and connections. Petrol I'm afraid making 155rwkw and 650rwNm Oh and Tks for the comments Dougal.



On the drawing board.

I have never had the chance to test the intercooler on my 40 with the pre and post temp sensors hooked up with the snorkel fitted. Only one quick run prior to Vic Winch with just the intake temp.

1st graph is
Orange - Throttle Positon
Green - RPM
2nd graph
Dark Blue - Load
Light Blue - Boost PSI
3rd graph
Red - Pre intercooler Temp (Rescaled by 1.82)
Spring Green - Post intercooler Temp (scale 1:1)

The Wolf V500 does not support 2 air temp sensors so the external map sensor input has been re graphed to use an air temp sensor, but at a scale of 1:1.82. In other words the red line is almost half scale, and the reason the graph shows it under the post intercooer temp.

After warming up the engine for over 20min pre intercooler temps were 45C post intercooler 26C ambient 19C

The run shown in the picture is 30sec up hill starting in 2nd gear.
Pre intercooler temp maxing at just over 80C post intercooler 31C ambient 19C




You can see even though the 2 scales are different in the bottom graph, my intercooler basically flat lines my intake temps even at full boost.