jkarran
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| posted on 22/8/07 at 11:06 AM |
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Intercooler vs Chargecooler
My charge cooler is going to have to sit on top of my engine, moving it to the nose is not an option. I'm after opinions especially from those
running in-enginebay coolers as to which is likely to be most efficient:
Air/Water with similar sized nose mounted water cooler. Water replacing the cooling air, ie flowing over the core not through it.
Air/Air with a ducted 8" rad fan sucking through the core and a good sealed cold air feed from the nose.
I have the bits and skills to build either and was leaning toward Air/Water but weighing it all up I'm thinking it adds a lot of weight for
little (any?) extra performance except perhaps the excess heat will be shifted out of ducts in the nose rather than into the already hot engine bay.
Oh and I can add an ice bucket for the drag strip. The blower is a roots type and working quite hard so the intercooler efficiency is hugely important
to getting a decent, safe power gain from the project. R1 engine.
jk
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ditchlewis
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| posted on 22/8/07 at 11:35 AM |
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Air cooled engines work better than water cooled engines in the desert because of the difference in temp of the cooling medium. I.e. air at 45 degrees
C or water at 95 degrees C
Surley if you are bringing in cool air from outside it will be better than rads with water at a much higher temp. water has also a weight penalty and
are the benefits any greater than the weight penalty?
Could you not put a spray bar either in the air duct or in the intercooler to lower temps still further with less of a weight penalty?
Ww2 German fighters used superchargers with a methanol/water injection system to boost their performance
I think I would go for the Air cooled version.
Ditch
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Ivan
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| posted on 22/8/07 at 11:46 AM |
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I would go for the charge cooler because i believe it is the better option package wise and can be more efficient with a much slower heat soak rate -
and you get the added advantage of being able to use ice for the drag strip. The down side is that it is more complex (pumps & pump controllers)
however if you are contemplating a fan driven intercooler it's also complex.
I believe the power required to drive a sufficiently large fan/fans will equal the power lost by the weight of water in the charge cooler so
don't worry too much about that. (I don't think that a ducted 8" fan will move nearly enough air - but you need to do the maths)
I think that either will have very similar efficiencies if properly designed.
As an aside I believe that for a tin top I would go for a charge cooler with the tank chilled by the aircon every time and a throttle or boost switch
turning off the aircon at near full boost as on the road you seldom use full boost for more than 10 to 15 seconds at a time at which point you will be
doing well over 160 kph.
[Edited on 22/8/07 by Ivan]
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jkarran
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| posted on 22/8/07 at 12:21 PM |
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Interesting to see different opinions
Complexity wise neither is a big deal, I've the bits already bought to make both, I've changed my mind once already! Both will involve
some sheet metal work but nothing compared to the pelnum or end tank on the cooler core.
The fan is nearly as big as the cooler and its main use will be at low speed to prevent heatsoak by keeping up a good cooling flow. Air pressure from
the nosecone should take over at reasonable road speeds.
The chargecooler option will have it's own water rad rather than sharing engine coolant so it should stay close to ambient when on the move. The
thermal mass of the water should keep temperatures reasonable for big standing starts. The big bonus is the ice option which could potentially net me
an extra 20bhp for a drag run.
Power consumption wise, the fan will use more power than the electric water pump for sure but neither use a huge amount of power.
The fan setup will weigh in about 3-4Kg less and it won't be in the nose. The car is already a bit nose heavy.
I just wonder if I'm deluding myself that I'll be able to prevent heatsoak with careful ducting?
jk
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DIY Si
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| posted on 22/8/07 at 01:42 PM |
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I'd go chargecooler, if nothing else it'll help keep the engine bay a bit cooler, which has got to be worth it. It'll also remove
the need for the extra ducting and all important space that this'll take up.
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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violentblue
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| posted on 22/8/07 at 03:18 PM |
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Water is much better at stripping heat from air, than air is, meaning if you use a air/air heat exchanger in a poor location your gain will be much
less than an air/water/air heat exchanger, with the final radiator in only a marginally better location.
But the flexibility of a the air/water/air system is ability to locate it almost anywhere without introducing additional air volumes on the charge
side, which will increase lag (how much is debated)
a few pics of my other projects
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RazMan
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| posted on 22/8/07 at 03:30 PM |
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I've been looking at this dilemma quite recently and I am still undecided. The air/air system requires much bulkier plumbing but is more
efficient in most situations, although heatsoak can be a problem at low speeds. The water/air system will not get the charge temps down as well, but
it has the advantage of keeping the intake pipes shorter (less lag?)
[Edited on 22-8-07 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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DIY Si
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| posted on 22/8/07 at 06:24 PM |
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Just as an aside, what is it that makes the air/air set up produce lower intake temps?
Would it possible to use a set up similar to that found in a fridge? Ie have a compressed/pressurised part that runs over the core and then releases
it's heat at the front some how? You might be able to get the intake below ambient that way. If you could plumb it all up, AND make it work.
Which may be a challenge.
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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RazMan
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| posted on 22/8/07 at 06:59 PM |
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As I understand it, the coolant temps will gradually rise above ambient due to the heat soaking in from the turbo. This would therefore mean that the
cooler's ability to get the charge temps closer to ambient becomes more difficult. This can be improved by adding ice but it can only be
regarded as a temporary fix for drag racing. However, if there is a LOT of heat to dissipate then water is more efficient (14 times iirc) than air.
I think the fridge idea is good in theory, but the amount of power needed for the large pump and fans would probably defeat the object imo.
[Edited on 22-8-07 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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DIY Si
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| posted on 22/8/07 at 07:53 PM |
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Surely having the separate rad in the front should stop things heating up too much? Especially if running a fan?
The fridge based thing was merely a thought, since I'm not too up on all the ins and outs of turbo installs. Getting there, but not all there
yet. Especially since I prefer superchargers. 
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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Moorron
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| posted on 22/8/07 at 08:34 PM |
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Lol, I would say intercooler. Its much lighter, cheaper and easier to do. There is much more to go wrong with a charge cooler and if it leaked into
the air stream you could hydro lock the engine.
The main advantage with it tho is the smaller pipe run for the air, reducing the lag by a small margin.
Having had many discussions about this very topic on the Renault turbo owners club and a few arguments, IMHO I cant see a charge cooler being better,
it will never be as efficient as an intercooler. Its got 2 matrixes instead of one and as none will ever be 100% efficient its always lagging behind
the one intercooler matrix. Its only going to be better at certain times (like sitting in traffic and ¼ mile racing) as the water will ‘delay’ the
heat soak from sitting in traffic, its also better in situations where pipe work is so long that having a ‘remote’ rad is better (like rear engine
cars which would be mad to run the intercooler at the front of the car, yet with the charge cooler piping its rad at the front is fine). I am going to
be fitting a intercooler on mine in the front nosecone, but if I couldn’t I would try maybe 2 smaller intercoolers at the sides of the car? Depending
if I could encourage the air flow to go thru them.
To answer your OP and if I read it right, I would go intercooler on top of the engine. This is taking into consideration I think you are saying if you
used a charge cooler the charge cooler matrix would sit on top of the engine where the intercooler would be and its rad at the front of the engine.???
Sorry about my spelling, im an engineer and only work in numbers.
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jkarran
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| posted on 22/8/07 at 10:41 PM |
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Cheers guys, seems like I've been thinking along the same lines as everyone else!
I think I'll be going air/air initially as I can change to air/water in the future if I like but I can't easily change back.
It's a road car but will see some track/strip time too. It'll have boost control (switchable maps for road/calm vs track  ) so will
make big boost fairly infrequently on the road and only for ~12 seconds on the strip.
Some pictures if it helps:
[IMG]
That gives an idea of where it all sits. Air/Air and Air/Water can be done stealthily (desirable) as the rad is fully shrouded so 'high'
pressure cool nosecone air can be collected without chopping holes in the body.
Lots more pictures at http://s118.photobucket.com/albums/o118/jkarran/ if anyone is interested
Keep the ideas coming!
jk
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Dale
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| posted on 23/8/07 at 12:53 AM |
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Do you have room to put the intercooler between the side rails on the intake side of the engine keeping it below the higher temps on top of the
engine. It may allow for some ducting to help draw the heat away. I am still working on setting the location for mine but it will likely end up in
the side pod/wing. Water or alcohol misting in the intake will drop it a lot as well.
Dale
Thanks
Dale
my 14 and11 year old boys 22
and 19 now want to drive but have to be 25 before insurance will allow. Finally on the road
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jkarran
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| posted on 23/8/07 at 08:30 AM |
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There's no room down by the chassis sideskin, there's a couple of braces and the steering linkage in the way. That and it's already
welded to the plenum and the bottom ducting is well underway. I did consider that location but having open front wheels it takes quite a battering
from chippings etc.
I've read conflicting information on pre-intercooler water injection, some say 'don't, it'll condense' some just say
'be careful'. It's possibly a trick to fall back on if I get a stuborn detonation problem. It'll also seal the rotors up
better if drawn through the blower increasing its efficiency.
Water spray onto the outside of the core is another option but it'll ultimately just lead to corrosion in the surrounding area.
jk
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bimbleuk
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| posted on 23/8/07 at 08:51 AM |
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www.autospeed.com have several articles on intercooler theory. I've learnt a few things from reading them. Some are subscriber only access but
this one below is decent starter.
http://autospeed.drive.com.au/cms/A_2469/article.html
As you can see on my car below I went for a front mount air/air. Even though this particular intercooler doesn't actually rate that well in a
couple of Autospeed articles. I've got it work as efficiently as possible. As I'm using a supercharger with fairly short pipe runs lag is
not noticeable.
Even on the rolling road under extreme conditions the inlet temps didn't get out of the 30s. On the road my inlet temps stay in the high 20s (20
deg ambient). The Rotrex I use is very efficient which helps. The water temp averages in the high 80s and the Rotrex oil cooler behind both
doesn't get above 60 deg temps which surprised me.
[Edited on 23/8/07 by bimbleuk]
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jkarran
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| posted on 23/8/07 at 09:22 AM |
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Sick looking Striker! Those 20V Toyotas just look so good.
Is the duct below the exhaust manifold just to let out hot air? Good idea.
What intercooler are you using, it looks to have ideal pipe positions, did you build it? Is that fuel pressure regulator just referenced to atmosphere
or is there another MAP referenced one lurking out of sight?
I think mine's going to run quite a bit hotter than yours due to the roots inefficiency, calculations suggest IAT of up to 46deg (20deg ambient)
if I can coax 70% efficiency from the intercooler. Blower temps are in the 110deg region... that'll be getting some cooling air I guess!
<edit> Interesting article, cheers. I guess it's going to come down to how often it's making real boost on the road. To an extent
that can be managed by the ECU and bypass valve so a big heatsink of water may be a good idea... the pendulum swings back toward air/water. Careful
testing is the only way to solve this conclusively.
jk
[Edited on 23/8/07 by jkarran]
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Moorron
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| posted on 23/8/07 at 09:59 AM |
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thats a nice photo of the twin cam.
uts set up like mine, but my intercooler from turbo enters under the rad. Its a snug fit and im worried the rad will suffer from not getting direct
clean air and cause the temps to go up.
Think theres some in progress photos in my profile under cbr100f heading (i missed a 0 off lol).
Sorry about my spelling, im an engineer and only work in numbers.
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bimbleuk
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| posted on 23/8/07 at 12:53 PM |
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JK,
The intercooler is from a Mk2 MR2 turbo. Fensport usually have a pile of em lying around!
Yes the Rotrex could be 15-20% more efficient than a typical roots but also they only work hard at higher RPMs. So some of the theory in that article
is even more relevant to the Rotrex.
The side vent is well proven to lower the engine bay temps and can lower air pressure behind the radiator. The other benefit is the transmission
tunnel doesn't burn my legs in the summer anymore!
That picture was taken on the day I took my car to get tuned. So the Rotrex belt was off and the fuel regulator was not referenced for boost/vaccum.
Drove there with 160BHP and drove home again with 260BHP which was nice 
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jkarran
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| posted on 23/8/07 at 02:01 PM |
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I think I'll look at venting my engine bay in that case. Have been planning to remove a 3/4" strip from the rear of the bonnet to help the
through flow at the top of the engine bay, only thing putting me off is the thought of a blown coolant hose venting over the flyscreen 
The article on intercooler water spray and their 'intelegent' controller is interesting. Should be easy to replicate something close in
Megasquirt or a direct copy of their control routine on a PIC dirt cheap. I'll probably be using a PIC in the boost controller circuitry
anyway.
jk
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