EFI University

[CMW]

I have asked five people, and had five different responses, so am now asking a wider audience .

I have a sports GT race car (Zeus) that currently has a Toyota 1600 4A-GE Formula Atlantic engine in it, making about 210 BHP. I am turbo charging it with the hope of seeing about 350 to 380 BHP at the flywheel. The turbo is a Garrett GT3071R, with integral wastegate. The management will be Motec M800. The current pair of twin choke Weber 48DCOE carb are removed and a plenum with a single 65 mm throttle body made. I am dropping the CR to about 8.5 to 1 and fitting milder cams, of about 270 to 280 degrees duration.

My indecision rests on how to intercool it. Anyone with nothing better to do is welcome to look at some photos of the car I link below. I won't muddy the water with my own, or currently suggested ideas, except to say I need to keep the current water radiator set up, I can't get away with less. I don't mid scoops on the rear body work, but don't want any front of the car mounted heat exchanger.

I will consider air to water, but ONLY if I can get information from people with first hand experience of this of this running a similar power output from a small engine, in circuit RACE trim. My fear is an air to water will work fine on the road, or even tack days, but may heat soak in full long distance circuit race usage.

Photos of the ongoing project at http://www.gatesgarth.com/intercooling2/intercooling.html


Thanks for looking.
_________________
Best regards,
CMW

[Gadgeroonie]

"My fear is an air to water will work fine on the road, or even tack days, but may heat soak in full long distance circuit race usage."

ive tried them all and the only time i was happier with water to air was when i could fill the bottle with ice cold water

go for a big front mounted intercooler - just make sure you are not running on the edge of the compressor map where the efiificency is poor and the charge temps will be higher

[Six_Shooter]

I would usually only use air to water in drag race or applications where air to air is just not feasible.

In your situation I'm sort of torn.

Since it's long distance, I would first be inclined to go air to air. Then you have to ask: Where do I mount the intercooler?"

Air to water could be used, but a rather large heat exchanger usually needs to be used, in order to bring the liquid (water, anti-freeze, etc) down to a low enough temperature, as close to ambiant as possible, so you will still need to find some place that will allow enough flow of air, with enough surface area to do so.

The place that I could see for you to mount either of these schemes is where the inlet through the boddy originally was for the carbs. You won't be using this anymore due to the different layout of the air intake system with the turbocharger being on the opporiste side of the car. You could add a similiar ( or mirror) image of what you have now to place a scoop or transition to route air down to the compressor inlet, and this still leaves the original hole in the body work there, for use in intercooling. You will need to allow for air flow out of the engine compartment though, which I'm sure there already is some, but this may need to be opened up a bit more, maybe even channeled directly from behind the intercooler/heat exchanger out to the air flow exit from the engine compartment. This would also likely increase flow through the intercooler/heatexchanger as well, instead of relying solely on pressure differential.

I think if it were me, I'd find as efficiant of a core I could find, and run an air to air. It's simple, virtually no parts to fail, certainly no supporting parts, like pumps or liquid transfer hoses to fail, and would be lighter overall than an air to water set-up.
This pays back with quicker acceleration, and higher fuel effciciancy, for the road race or endurance racers.

With your power level, and the ability to add scoops,and air channels you wouldn't need a huge air to air intercooler as well, and think that the opening that you already have, may be enough to do what you need to do.

[4SFED4]

Check out a Porsche 962... they used a combination of A2A and A2W.

I run A2W and have IAT's of +25*F whether at idle or WOT. The car see's some track time, road course not drag.

A2W is more efficient than A2A, as long as your components (intercooler, heat exchanger, resevoir, pump) are properly sized you will have a solution that works very well.

A2W is more complex though as you need a resevoir, pump and heat exchanger. These components are smaller than an A2A setup so packaging is easier.

Looking at your pictures I would personally go A2W and drop the carb's for injection. The space the carbs take up alone would be enough to mount your intercooler. I understand you may be rule bound with them.

Cheers a lot and good luck with your project.

[Power-Tripp]

I am a big fan of the efficiency of air/water systems - especially used with Laminova cores in the plenum. But water acts like a heat sink that is limited only by the volume of water. I have been wanting to test a tank with paraffin in the coolant system to test a theory about the paraffin absorbing much of the intake heat until the paraffin is completely melted. This would (in theory) act like a much larger heat sink. This is just like ice in the system holding the same temps until the ice melts. Fusion, specific heat, and all that.

When endurance and weight are at issue, air/air is hard to beat.
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"To achieve anything in this game you must be prepared to dabble in the boundary of disaster." -Sterling Moss

[Warpspeed]

Yes the water certainly does act like a big heat sink, and that can be a DISADVANTAGE too.
At least in a road car, once everything heat soaks, you will have great difficulty cooling all that stored water back down to anything like ambient temperature.

Air/water/air systems are perfect for one shot operation, like drag racing, or hill climbing, especially with iced water.

After building quite a few different experimental systems over the years, I much prefer a large front mounted air/air cooler. It is simpler, lighter, and there is far less to go wrong. If you can keep the pipe volumes down, it is the preferred way to go IMHO.

[CMW]

Wow, lots of excellent replies, thank you all for your trouble. OK, I think air to air is going to be the best solution. I spoke with Mel at Docking and Co Engineering, (Silverstone), who has done some intercooler work for me before, and he too was strongly in favour of air to air. The people who have run air to water all seem to be using it in road cars, or dtag / sprint cars, where, no matter how much of a lunatic you think you are, it's all but impossible to maintain the sort of engine loadings you'd see in a 25 lap race situation on a road race circuit. Therefore I remain sceptical of the seemingly very small heat exchangers they get away with. For sure, I am in no doubt that air to water can and does work, I am just uneasy about the cost of sizing a set up incorrectly, and having to re-engineer a lot of stuff, plus the added complexity and weight.

So, now I am set on air to air here is a truly dreadful rendition of two locations I consider feasible for an air to air charge cooler. The original oval aperture in the rear body work is where a carbon air box, F3 style, stuck out. I have now removed the twin side draught Webers and am in the process of fitting the existing short manifold with an alloy plenum and a single throttle body. It shoudn't stick out laterally from the head too much, hopefully allowing a maybe 50 mm core intercooler to fit semi vertically behind the side of the bodywork, roughly where the existing air box was. The aperture could be enlarged and a simple carbon or glass fibre scoop made to feed the outer face of the I/C with air. I could probably seal it to the bodywork with foam or a simple rubber seal strip. I reckon the rear engine bay is a low pressure area, to a pressure differential should exist.

The other idea is to cut out a rectangular section of the passenger (LH) side of the rear bodywork upper surface, fit the I/C above the exhaust manifold, and make a scoop to bring the rear bodywork on the LH side level with that on the RH side. The scoop would see clean air, and would be higher than than the dashboard line. Downside to that is the I/C would be quite lose to the exhaust manifolding and heat soak would occur. I could make some heat shielding though. I am unsure which area would be best for picking up the best flow of clean high pressure air. Despite a plethora of photos of the car in one piece I don't seem to be able to find anything very suitable from a rearward angle. I have added the best one I can find, you can see how the LH rear bodywork top panel is lower on that side, compared to behind the drivers head. The broken white lines badly reflect where I would envisage making the actual apertures for the I/C, in each case.

Please bounce more opinions and ideas about Thanks and a very happy, healthy and prosperous New Year to all.




_________________
Best regards,
CMW

[Warpspeed]

Do some differential air pressure testing at speed. Wherever there is a high pressure differential from one side of a panel to the other, that is where the intercooler goes.
No pressure differential = no airflow through the core.

Get yourself a Magnehelic gauge, they measure low differential air pressures in various ranges. They are not expensive and have a large easy to read scale, Check out e-bay.

Poke around with some small bore air tubing inside and outside the body to find the best spot to cut a hole.

[CMW]

[sam@tdi]

My advise would be to steer well clear of air to air in the back of the car.

We've been playing with supercharged Honda engines in the Lotus Elise and Exige for the last 4years now and we've seen both approach's tried and tested.

Water to air is very tricky to make work sustainably, you need massive capacity in the pre-rad first and foremost. Once you've achieved that you need to find away of giving the charge air as much time in the hot-end heat exchanger as possible, then when you've got that you need to really circulate that coolant. A customer of ours who manufactures the Honda>Lotus conversion kits put a massive amount of effort and time into researching this and to his credit he got there in the end, and now has many cars running the system very successfully in the Lotus on track series, Britcar (inc 24hrs), LMA in the UK and a very hot GT series in Australia.

We've seen competitors persevere with air to air solutions and they've made it work, but always at a disproportionate cost in terms of aerodynamic efficiency and pressure pipe volume.
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Sam Borgman
www.tdi-plc.com
www.toda-europe.com
www.rototest.com

[Martiens]

Ive installed a Motec on a Porsche 956, and yes they run A2A and A2W on both sides of the car. each turbo has its own set of coolers. They run the A2W first then the A2A. Ive never seen a car that cools the charge as well as this. We are running 1.2 Bar boost with 2 by KKK K27`s

Martin