ian/555

Anyone sell a ChargeCooler for the Impreza?

If so, what price are they and are there any downside's to using one?

Thanks Ian

GavinP

Ian,

As far as I am aware, there is no commercially available chargecooler kit.

Pace products produce a universal kit but due to the design, it would be very difficult to adapt to fit an Impreza - see

IWatkins

Gavin,

Why no good on track ? I.e why no good under full boost most of the time ? Is it because the capacity of the system is too small ?

They ran chargecoolers on the TTE rally cars for quite a while and quite successfully for a few years. IIRC the radiator and coolant capacity was quite large though.

Cheers

Ian

GavinP

Ian,

I obviously haven't tried it on a GT4 but I can say that on my car I can generate heat quicker than I can get rid of it (if I try ).

"Buy a bigger radiator!" I hear you cry, and that is probably the answer.

Out of interest, what capacity is the chargecooler system in the GT4 ? Does it share the coolant with the engine (like a Cosworth)?

On my (evolving) system, I have the exchanger (about 1.5 litres approx.), oil cooler (0.3 litre), reservoir (4.5 litres) and I guess the pipework (all 5/8"). This runs separately to the engine coolant.

OK, I'm off to buy a bigger radiator!

Thanks

Gavin

firefox

Gavin,

The oil cooler will not give you enough cooling...

Get yourself a larger/less robust cooler.

Use seperate coolant to the engine coolant...definately!

Where is your reservoir located ?

J.

IWatkins

Gavin,

The standard system on my GT4 consists of the chargecooler (heat exchanger), the radiator (motorbike sized), pump and hoses.

The coolant is a separate system than the engine coolant (they got one thing right )

Total system capacity is about 3.5 litres

On this standard system, the coolant would only last about 5 minutes of flat out (on boost) driving before becoming really hot (like 80 degrees+ and hence useless).

I then tried to increase the capacity to about 8 litres using a reservoir post radiator and pre-chargecooler. This worked and would last about 10 minutes before coolant temps were again no use at all

So, I ditched the reservoir, didn't like that extra weight anyway.

Next was the radiator. The OE kit was about 12 x 9 inches, i.e. poxy.

Replaced this with a Pace all ally rad that fills the front grille. Approx 3 foot x 12 inches. About 180 quid. Total capacity of system back to about 4.5 litres. Rad is super light.

This really works well. Can drive the car flat out for ages and can still put my hand on the chargecooler afterwards without burning myself

So, yes, replace the radiator. From my tests (unscientific really) is appears that cooling surface size is much more important than fluid capacity. Fluid capacity helps, but it only delays the time it takes to reach useless temps.

Intake temps are stable at around 35 degrees but I want to test further.

Another GT4 owner (has the larger chargecooler) gets an average intake temp of around 20 degrees C at 1.4 bar That was just by replacing the standard OE radiator with the much bigger Pace unit.

Job's a good 'un

So, I would say, yes, take a look at a bigger, more efficient radiator.

Cheers

Ian

ian/555

Disclaimer!!! My technical knowledge could fill this full stop. So I hold no responsibility if any of what I am about to type is CAK!


Guys wouldn't the rate of flow have an effect on the ability of the chargecooler to dissipate heat as well as, the capacity of the system itself?
To fast and the water don't have enough time in the radiator to cool down before being subjected to cooling the inducted air or to slow and the water overheats?

Did you try to increase the flow rate of your system as well Ian W?

Is there an optimum flow rate/capacity/surface area ratio, If there is, what is it?

IWatkins

Ian,

No, you are bang on correct

I have yet to play with the pump rate on the GT4 but I do know it is quite slow. I'm sure there are some sums you could do to work this all out but I haven't looked for them yet.

In the ideal world, the pump would make sure that the water going back into the chargecooler is as cool as possible, but that would have to be balanced against how quickly the water already in there is being heated by the transfer of heat from the air charge passing through.

My maths ain't very good, but I'm sure there is a way to work this out.

As standard, on the GT4, the pump is controlled via a small ECU. This switches the pump on only when you go to full throttle (actually 90% throttle). Even if you only do that for one second, the pump will carry on running for 30 seconds then switch off. And then, it doesn't matter what you do, it will not run again for at least 2 minutes. Work the reasons out for that ??

Needless to say, I've bypassed this and the pump runs full time (for now).

And we haven't even got onto the size of the chargecooler itself yet

Cheers

Ian

ian/555

Hmmm,
Ian I have just been thinking back to an old physics lesson. I am sure that at the time in the text book, it said that the best colour for radiating heat was black! Maybe if there are any central heating engineers on the bbs they could confirm this?

If black is the best colour for heat radiation then maybe all these nice shiny exchangers should be matt black ( or would matt paint create unwanted turbulence? )

Anyone know what the latent heat of evaporation was about? Would any of it's formula be relevant here?

My head hurts

firefox

Good stuff chaps...

Keep it coming

Matt black is the best to radiate heat the quickest... but I belive a shiny surface radiates out more heat.

Latent energy of evaporation is the energy required to convert the state (from water to steam/gas) of a substance

Something to remember is the paint could act as a thermal barrier

The flow (duration) of the water in the cooler is important...to quick and it doesnt have enough time to transfer the energy/heat out... to slow... and you arent effeciently cooling/flowing the water.

J.

Bob Rawle

And also of importance is ensuring that the pump is not too big and powerful so as to cavitate the coolant, if that happens then it becomes aerated and the efficiency of the system goes for a ball of chalk, The balance between capacity, flow etc is of paramount importance. Managed to get my Cav turbo charge temps down from 120 deg C (yes thats right) to mid 50's on the track using a well designed and balanced system. It took a bit of adusting though but was well worth the effort. the Legacy unit works well up to a point but as Gavin has pointed out it can suffer from a thermal capacity problem, its very efficient though. On the two occasions I have used this (engine dyno) exit water temps were in the order of 60-65 deg C. This running circa 1.5/1.6 bar boost.

IWatkins

The paint thing has always done my head in

I have always been told that black is best for speed of radiation, but I also thought that black was the best absorber of heat etc. Arrrggghh !!

Anyway, talking about the radiators, the OE Toyota radiator was black but very small. The Pace unis is very big but very shiny ally. Er, still not sure what colour it should be.

Also, the chargecooler (on the GT4) is ally but is covered in a thick varnish like finish. Removing this helps, so I'm told. Many of the GT4 owners have had their chemically stripped. Only downside is that they need cleaning quite often now. But hey, they look good and they should be radiating more heat.

The other thing I have thought to do is to lag the whole chargecooler (sits above the block) so that it doesn't absorb any heat from the engine bay. i.e. doesn't heat soak in traffic. Again, quite a few of the GT4 lot have built heat sheilds to sit between the chargecooler and the block and also appears to help.

Bob has a good point ref. cavitation of the fluid. Air is poor at removing heat, water is good

I guess what you need is a good idea of the effeciency of the chargecooler, known the capacity of the system, the cooling surface of the radiator, the speed of the pump etc. and then you could sit down and with some maths/physics work out the best system.

I guess, the best system would be one with a big radiator, an very effecient chargecooler and an intelligent pump system that alters the speed of flow depending on throttle position, road speed (hence air flow), and boost levels.

No, no good, too late in the day, my head is about to explode

Cheers

Ian

GavinP

*LONG POST*

I should have listened to J (Firefox) when we discussed this before and got a bigger radiator there and then.....

I read up quite a bit on Intercooling within Autospeed, "Maximum Boost" by Corky Bell and another book about turbocharging. They all seem to share the opinion that the radiator is the least important part - but obviously not as minor as I now realise...

I got Forge Motorsport to make an alloy reservoir to fit in the only gap in the engine bay which is in front of the air filter. Some blurry pics at:

firefox

I saw temps just over 40 degrees with my charge cooler... this was during summer... on a hot day (t-shirt/shorts/aircon weather)...

My front intercooler seems to work a tad better

The charge cooler utilised a two speed system (resistor) based on boost.

The airiation/cavitation can be minimize by redesigning the tank...and by adding an anti-caviation/swirl pot tank

J.

GavinP

How about this for a (crazy?) idea ?

Use the Legacy chargecooler in addition to a front-mount.....

The Legacy heat exchanger has a round entry pipe underneath facing forward which you could connect the return from the front-mounted IC.

I would think the main downside would be pressure loss so you would need a very efficient front air/air unit - Spearco make some units which are long but run vertically (as opposed to the normal horizontal) to minimise pressure loss.

Putting a slim 18mm water radiator (with large area) between the main rad and the air con rad would cool the water. I appreciate that it is not the best position for it but you would be running out of front space at this point.....

As the universal chargecooler that Pace sell won't fit a Scoob - would this be a better answer ?

Are you able to buy Spearco intercoolers in the UK or do you need to import them ?

Thanks

Gavin

ian/555

Sounds like a good idea Gavin.

I would be interested in seeing it fitted, if you manage to get it to work.

On the spearco intercooler subject would it not be possible to get pace to make one to the same spec?

Thanks guy's for the top info