charge cooling using the engine cooling system...

[Jim-SR]

been thinking about charge coolers and noticed that everyone runs a seperate pump and a seperate radiator for their charge cooler setups. space is at a premium, as is airflow (another radiator is going to mess my aero up more), as is (most importantly) weight! plus i dont want the power losses of driving yet another pump

im not going to have the airflow at the rear of the car to realistically be able to mount a chargecooler rad at the back end of the car, id like to have it up front. thats going to mean all the pipework, full of water, another rad, as well as the chargecooler element, and the pump. it all adds up to a load of weight that i dont want

so, whilst i think i already know the main answer as to why it isnt done, why dont people run their chargecooler within the standard cooling system? cold water out of the rad comes straight into the chargecooler, and from there goes into the engine like normal? the water from the radiator is always going to be slightly hotter than if you run a seperate radiator that only deals with chargecooling. but how hot does boosted air realistically get? id hazard a guess at 50-60 degsC quite easily when the engine is being pushed hard?

if thats the case then its only 20-30 degs cooler than the engine, and if i was to run a larger and more efficient radiator (more efficient = aluminium = weight reduction anyway!) then i should probably still be able to get the chargecooler running around 40-45 degsC, which would be an improvement over not running any cooling at all, and dare i say an improvement over an intercooler? (which is completely non-viable due to the logistics of sending air the length of the car and back again)

just wondering what peoples thoughts on it are, and what the specific reasons are for it not being done very often (i say that because im sure someone somewhere uses it, but i cant find anyone!)

[jaspa]

I think it is because the main water system is designed to keep the whole engine less warm than without it. where as the idea of the CC/IC is to reduce the temperature of the air being passed through the inlet manifold. Because it is a lesser quantity of water it should be possible to keep this system that much cooler than the engine system, there will be more water here and also going through the block itself will keep the water warmer.

I think :confused:

edit - just reread what you put and err... ignore me. DOH!

[robwsurf]

how about mounting a thin rad above engine bay at the back end of the roof with a scoop

[AlunJ]

Jim, from what I recall tis fairly regular to see a post-turbo temp of over 100 degrees C on boost. A normal coolant temp for a 4a is around 85 degrees at idle, can hit 100 or more on a track day. This is why you don't take the filler cap off with the engine hot - the coolant system pressure drops to atmospheric and the waters boiling point drops to 100 (which is below it's current temperature if you've been giving it some stick) causing coolant to flash boil and cause big cloud of scalding steam :cry:

If you ran the chargecooler rad off the stock coolant systems under off-boost conditions you'd end up heating the intake charge. On boost you'd not get any intake cooling due to the marginal difference in temperatures between hot charge and hot coolant.

Is there not sufficient space for a chargecooler rad (or a rad that'll fit) mounted just ahead of the gearbox or scooped into a space in the boot?

Edit: found the equations for charge temps etc - a 100% efficient turbo would be putting out about 125c at a bar of boost.

[Murf]

The coolant in my cc system never actually gets more than lukewarm. If you used hot engine coolant then you'd prob actually be heating the charge air!

[Limeymk1]

In addition to the above you wouldn't get any flow through the charge cooler until the thermostat opened unless you made up a bypass for it which would probably be as much faffage as installing a seperate system.

Also as stated it'd probably become an 'interwarmer'.

[s_cleary84]

I've pondered this one too mate, I'm certainly not an expert on the subject but I reckon in principle it would work. I've noticed that the cold side of the rad is merely lukewarm by the time it gets to the engine, probably 10 or 20 degrees above ambient (the benefits of such a large cooling system)!
You'd be adding thermal energy to the system, so a larger Aluminium rad would take care of that. I'm wondering would there be an issue with the water speed? i.e. the rate at which the warm water passes through the core of the chargecooler: Too fast and the water will not absorb enough heat, too slow and you'll get heat-soak back into the core.
Would the engine's water pump circulate the water fast enough or would it "stall" in the 'cooler?


id hazard a guess at 50-60 degsC quite easily when the engine is being pushed hard?
I think it's much higher than this at full boost, has anyone measured it?


Have a read of this article (http://forums.twobrutal.com/showthread.php?t=14152) as an alternative to water cooling. It's interesting, definitely un conventional and therefore BRUTAL! :freak3:
Might even save a bit of weight too:thumbsup:

Along the same lines of simplifying and saving weight, what about losing the full length heater pipes and just 'tapping off' the hot water from the rad pipes at the front? There must be a litre(kilo) or two in those pipes, not to mention the hard pipes & brackets, hoses etc.

http://www.twobrutal.co.uk/forum/images/recovered/2009/02/146.jpg

I might have the hot/cold sides mixed up, can't remember.

[s_cleary84]

Ha. 5 responses by the time I wrote that rotflmao
I forgot about cooling system pressure. of course it's gonna be hot.

[Jim-SR]

heater pipes are already gone!! its a track car so there is no need for heating. in the same vein, there is also no issue with the thermostat as nothing will be running until the engine is upto temperature, and once its there it wont be dropping back down whilst running

if boost temperatures can rise above 100 degC then i think it makes the engine cooling option even more viable. sure, the temperature is up around the 85 degC mark for the ENGINE. but look at where the temperature sender is located - at the thermostat, which is the last place the coolant travels to before its journey to the radiator

after it exits the radiator, assuming the radiator is working efficiently, i would expect the coolant to be 40-45 degrees, although obviously ambient air temperature will play a part. on a 30 degC day (like we ever get them in the UK anyway) the temperature may be higher, but the same is true of an independant chargecooler rad. but typical the weather here during trackday season is anything from 10-30 degsC, and id therefore anticipate coolant temperatures at the chargecooler core of probably something like 30-50 degsC. which wouldnt be bad at all

there isnt going to be space to mount a radiator at the rear of the car in a position where it wont screw up my airflow, and id rather not have the weight, regardless of where it mounts. it sounds as though my idea is actually a viable one, albeit one that needs further investigation. at the end of the day it requires only one item to be purchased (chargecooler core) and plumbed in to test it. if it doesnt work then buying a radiator and a pump will give me a tried and tested setup, and il just have to take a hit on the weight penalty!

[Jim-SR]

that fusion intercooler setup sounds pretty cool, but it wouldnt suit my application. the car will be on boost almost permanently whilst being used, so it wouldnt offer sufficient cooling over long periods of raised temperatures. it sounds as though maybe air-air cooling is actually the best method , but is just about impossible for me to implement, so water-air is going to be a compromise anyway

[Paul Woods]

Can i chuck an idea i've had for a while into the pot? How about plumbing the AC system through the CC...ok it would need high pressure fittings etc but surely this would be much colder? just a wacky idea i had.

[Marksman]

Can i chuck an idea i've had for a while into the pot? How about plumbing the AC system through the CC...ok it would need high pressure fittings etc but surely this would be much colder? just a wacky idea i had.

I had a look at this a while ago. 2 concerns. Firstly you're sapping engine power to run the pump and secondly unless you buffer the heat somehow you might be going too cool. Near zero temp to +100 in a flash under full boost could be metal fatigue time in an aluminium rad. Not saying it can't be done though. I did wonder about using it as a precooler that is used just before a drag race or traffic light derby. (But turn it on to cool the system, then turn it off for full power to the wheels, and then launch if you see what I mean?)

Owen.

[Paul Woods]

yep totally agree it has a use as some sort of short zap colling aid before a hard launch etc... anyone know if there is any reason this would not work?

[Marksman]

Or if we coil the hardlines to the correct diameter we could use it to cool beer cans at this year's JAE...

[s_cleary84]

For drag racing......clicky (http://www.are.com.au/Big%20HP/Dry%20Ice%20race%20cooling.htm)

[semtexcow]

doesnt the aircon system have a relief valve incase the coolant pressures rise too high?
im sure i found one when i was ripping out the aircon on the celica
a sudden heatsoak into the aircon coolant could cause an over-pressure in the system and loss of aircon coolant
be great for beer cans though :)

[Murf]

Yeah, theres a high pressure cut off in the A/C, as well as a low pressure cutoff to protect the compressor.

I have an intercooler temp datalogger. Heres a graph of the output from it when i hooked it up to my GT4. The high initial temp is due to heatsoak from the engine being run, then stopped for a while.

http://www.twobrutal.co.uk/forum/images/recovered/2008/05/287.jpg

[Murf]

From it you can see the coolant temp is in the mid-high 20's and how when the coolant temp drops and stays low, the charge temp drops noticeably too.
Say for example you run it off you engine cooling system, even if you get the temp down to mid 40's your still going to have much higher temps than if you ran a seperate system. Its worth the extra weight to have it seperate, IMO.

[Jim-SR]

interesting results. essentially the boost charge is 15 degrees hotter than the coolant in the system, and that is using a stock GT4 charge cooler right?

if i was to get one that is more efficient (as im sure OEM items are compromised in some way for cost or whatever) so maybe it worked 10 degrees hotter, and i could get my coolant coming in at around 35-45, then i could get boost charge down to 45-55. that wouldnt be too bad, somewhere below 45 would be ideal

anyone got a calculation or example of how much output power differs compared to boost temperature?

in order to justify a seperate system and potentially 5-10bhp (or more at the RPM's i want to run!) drain on the engine for a pump, and the additional 15-20kg of equipment to run a system on its own, il need to be totally convinced that im going to make back more power than il lose from the pump (remembering that electric pumps still drain power, and my alternator will be switching off at full throttle, making an electric pump potentially unuseable without a larger battery, and thus even more weight) and that the additional weight (which will potentially be 2-3% of the overall weight of the car!!!!) which is going to hurt my cornering is going to be worth the performance trade off for having more power. power is of less importance to me than minimum weight

[Murf]

Thats in a stock st205 gt4, the mr2 system will have loads more water in it and therefore temps are lower. From memory my air temp when it leaves the CC core is between 20 and 30deg C at 17 psi boost!

[GregLeBon]

anyone got a calculation or example of how much output power differs compared to boost temperature?


Approximately 3.5% power loss per 20C raise in charge temp......

If you start with 200hp @ 20c, you'll only get around 175 @ 100c.....
(or something like this.......saw it on some sort of Audi sport website a year ago......?:thumbsup:)

[GregHoon]

Jim, i think if you had an intercooler that protruded from the boot of the car you'd be able to get enough air to pass over it to keep the intake temps low enough without any 'added' weight to a stock turbo setup. Mine has a boot located intercooler. I'm running a standard-ish rev 1 3sgte at 15 psi and when i give it some constant welly on the motorway i'm not noticing less performance as the intercooler warms up.

The mk1 is not exactly the most aerodynamic of cars so i don't think an external intercooler will be introducing any noticeable drag. Have you decided on the engine you want to go for yet and the setup?:poke2:

There's plenty of ideas yet.

Greg

[s_cleary84]

Have you considered running no intercooler at all, but with water injection instead?:hidesbehi

A well designed water inj system would give ample cooling and the lack of IC piping would give snappy NA-like throttle response!
Granted, you need a reservoir for the water/methanol, but you can place the weight where you need it, i.e. in the frunk or passenger foot well to offset the driver.
I'm sure compressor efficiency is a factor too, I could be wrong, but +100 deg temps would imply the turbo is running outside it's peak efficiency 'map'.

Most of the off the shelf systems make use of a high pressure (expensive) pump, boost switch, high pressure nozzle etc, but what about using the venturi effect from a good old carburetor? Compressed air exiting the turbo passes through the water fed carb and an increase in air speed (boost) picks up more atomised water. Simple and adjustable.


BTW I've ditched my heater too mate, but it's a bloody long winter you have over here!

[GregLeBon]

WI is a much misunderstood beast.....!

I removed my IC on the 4AGZE and used a WI setup (Aquamist).
I just fitted a 0.7mm nozzle initially, but did some experiments with high-speed soleniods, etc, later.

Also tried H2O, and various Methanol / water mixes.

TBH, this is a way forward: the amount of heat absorbed by the evaporation process is huge: adding methanol only improves things (up to a point: then you NEED a standalone ECU......but thats a different ball-game!)

I have had HUGE arguments on various forums on this subject (and CBA to get into any more! lol)

...but the bottom line is it worked for me: the steam cleans deposits from the chamber, the combustion process benefits immensely, and you can advance the timing more, giving more power.

IMHO, injecting a very fine water mist BEFORE the turbo / SC is the way to go...sort of emulates the "driving-in -the-early-hours" effect...!

You could have a 2 stage system: a pre TC/SC spray, and a "det-controlling" stage for when you're pushing the limits......
Most of this needs a programmable ECU, but its all doable..needs mapping, but you CAN ditch the IC....

Mind you, in front-engined applications, where you have the luxury of being able to fit a large FMIC, you're probably better off using one: a properly-specced A2A can be very good, light, etc.............and you'll never run out of H2O......!

(not that thats a problem...when was the last time you ran out of petrol..??!)

[Jim-SR]

a few more interesting replies. if the 3.5% per 20degC thing is correct (its obviously just a generalisation) then in theory id probably only lose 10-20bhp through running a chargecooler off the stock cooling system

so far as running any kind of intercooler or radiator protruding into airflow at the rear, it just isnt very feasible. i wont have anywhere at the rear of the car that i can stand to disturb the airflow, so its essentially front or nothing. the only area at the rear is going to be inside the engine bay with minimal airflow, and what flow there is will be quite hot

water injection may be an option, il be standalone on the ECU anyway, but its a question of whether something that can control the water injection will be within my budget. plus theres the issue of carrying the extra water, it could potentially weigh as much as a chargecooler setup, but also potentially be more effective. a "venturi" system may simplify things to within budget, so that only weight would be an issue

[GregHoon]

How about a vent on the side akin to the one for the engine, but to allow more air into the boot and onto the intercooler. Then vents at the back of the boot to allow airflow out.

Am interesting to see what you come up with as you are looking at a lot of options and seem open-minded as to a solution. Plus like that you have been so rigorous in keeping weight down. :thumbsup:

Greg

[s_cleary84]

Here's what I meant about a venturi WI system.
I'm sure everyone knows how a carby works, but i found a good diagram. Then I hacked it into a "Hydurettor" WI system haha.

http://www.twobrutal.co.uk/forum/images/recovered/2009/02/1.png

http://www.twobrutal.co.uk/forum/images/recovered/2009/02/2.png



plus theres the issue of carrying the extra water, it could potentially weigh as much as a chargecooler setup

I agree that weight is the enemy. But maybe well-placed ballast can be your friend. I've always thought the AW11 could do with a bit more weight over the front tyres.
Alternatively you could use the existing washer bottle with a separate pump (a little methanol on the windscreen won't hurt, will it:confused:) so it would be weight-neutral!

[GregLeBon]

How about a vent on the side akin to the one for the engine, but to allow more air into the boot and onto the intercooler. Then vents at the back of the boot to allow airflow out.

Do this...then stick a Spal fan on the core...

Then you'll be able to control the airflow over the rad....

As long as the cold air has a good route into the boot, and the hot air is ducted out efficiently, it'll be very efficient.......:thumbsup:

The other Greg.!

[s_cleary84]

windscreen washer fluid already has methanol (http://en.wikipedia.org/wiki/Methanol#Other_applications) in it :)

I've wondered what is the best way to mount an IC fan - push cold air down or extract hot air? both have their pros & cons i guess.
Heatshields and thermo-wrapping the exhaust would help in either case.

[Jim-SR]

a fan will use as much if not more electricity than a pump, but used with an intercooler would mean no water on board so would save on weight. a problem i see with using a carb for feeding water is the surface tension of water, i think it would cause major problems with the water release, it would feed out in droplets as more water collects at the nozzle, as opposed to a constant stream. i can see that causing some pretty major problems. running methanol or another additive would then make it pricey in the long term.

so far i think the options available are....

front mount intercooler - too much pipework, wouldnt work

rear mount intercooler protruding from bodywork or vented - disturbance to airflow, so wouldnt work

rear mount intercooler in engine bay with fan blowing air - possibility. fan will drain power, but intercooler will save weight

chargecooler with rad up front and own pump - pump drains power, adds lots of weight

chargecooler with rad at rear - will disturb airflow, so wouldnt work

chargecooler using engine coolant system - no power drain, wont be as efficient as separate system

water injection with ECU setup - probably the most effective setup. but expensive and adds weight

water injection with carb - potential problems but might be doable. adds weight


i think those are all of the options thus far. its a question of weighing up the pros and cons of each and figuring out which one hinders me the least. they all have major drawbacks, but theres always a compromise somewhere

so far as using water as ballast goes - im space framing most of the car and running double wishbone suspension all round. so what works on stock AW11 is pretty much irrelevant lol. im more concerned with having the absolute minimum of weight without spending a fortune