Hill climb and cooling issues.

[mr30%jr]

i dont see the logic behind that mod to be honest youd be beter of just to cut and shut the return and put it down the botom. even beter just slap an aw11 one in there.

the water will still just flow across the top.

[pureadrenalin]

This will let water flow across the bottom much better.
If it still overheats, I’ll know I have a terminal problem.

I couldn’t put an AW11 radiator in there. That would be like admitting that the design of the AW11 is superior to the SW20

It would be like using Honda parts (actually I have a Honda petrol cap)

[mr30%jr]

ill admit to them being better handling but somethings have been comprimsed for a biger more spacious modern car

[Py7h0n]

Why not just get an aluminium replacement made up?

Get it made thicker and crossflow to ensure everything is 100/100!

[85AW20v]

When I'm bleeding my AW, I do what Fivebob says and jack it up as high as possible and also use a piece of heater hose with a cutoff coke bottle taped to it as a sort of header tank to give a bit more pressure to fill the lines and force the air out. I think its 1/2" hose that fits neatly into the filler neck. It take about 15 minutes at idle to get the outlet of the radiator up to temperature and the pipes at the motor near enough to the same temp. And I'd go with mr30%jr and block off the cold outlet at the top of the radiator so the water has to go from top to bottom.

A while ago now, Paul Tulloch, from Wanganui Exhaust Centre, supercharged an SW20 and had overheating problems during events. Traced it back to the waterpump cavitating due to the constant high revs so installed an electric water pump and solved the problem. You might want to give him a call.

[Mr Revhead]

cavitation could also be due to wrong radiator cap

[matt dunn]

I also doubt that what you will have done will fix it,

In fact I believe it will make it worse.

Inlet and outlet need to be diagonally opposite each other,
and the outlet needs to be at the bottom to get the cold water to the engine as heat rises,

[fivebob]

Like I said before, there is nothing wrong with the stock system. It's good enough to support 700HP, and to run 12Hours around Bathurst, albeit in non turbo form.

If it's not a blown Head gasket or a bleeding problem then I wonder about the aerodynamics.

Is all the undertray still intact and a close fit to the radiator?

What about the top cover for the radiator?

Is there any room for air to escape around the side of the radiator?

Why is the number plate mounted in the radiator airstream?

[matt dunn]

Stuff

All good points,

air flow in around and out of the radiator is as important as the actual radiator itself.

[pureadrenalin]

Thanks for all the ideas guys. This is giving me a bit to think about.

Why not just get an aluminium replacement made up?

Get it made thicker and crossflow to ensure everything is 100/100!

Because a PWR alloy one is a direct replacement (inlet/outlet both at the top) and sells for $850 aussie. This is costing me ~$80 of radiator mods, a couple of $10 radiator hoses, and some favours from some mates.
There are not many other manufactures that make an alloy radiator for the MR2. I’d hate to know how much a custom one costs.

A while ago now, Paul Tulloch, from Wanganui Exhaust Centre, supercharged an SW20 and had overheating problems during events. Traced it back to the waterpump cavitating due to the constant high revs so installed an electric water pump and solved the problem. You might want to give him a call.

Cheers for the info. I’ve been thinking about adding an electric water pump so I can have in switched on and water flowing when the car is turned off. This will probably be the next step on the cooling front.

cavitation could also be due to wrong radiator cap

due to too lower pressure?
We replaced the radiator cap at the last meet, thinking that the rubber gasket on the bottom of it might be a little worn. It wasn’t.

I also doubt that what you will have done will fix it,

In fact I believe it will make it worse.

Care to elaborate?

Inlet and outlet need to be diagonally opposite each other,
and the outlet needs to be at the bottom to get the cold water to the engine as heat rises,

Why do they NEED to be diagonally opposite, and outlet NEED to be at the bottom? Toyota obviously didn’t think so.
I’m just doing this to make sure that the bottom is getting even flow.

Come on, give me some credit, I design piping systems, heat exchangers, fluid flow systems for a living (be it on a bigger scale). For this reason, the “heat rises” argument makes me laugh. It would be perfectly fine argument if this was a convection system, but its not, its forced flow. ALL the cooling will be done by the fin/tube section of the radiator, the header tanks will do neglable cooling. For this reason, from a cooling point of view, it doesn’t matter where the inlet/outlet is on the header tanks.
From a “having even flow through all fin/tubes”, it is best to have end tanks like a “GTR style intercooler”, slowly going from a pipe shape to a rectangle.
I’m going one step better than the diagonally opposite and having inlets and outlets on both top and bottom.

If it's not a blown Head gasket or a bleeding problem then I wonder about the aerodynamics.

Is all the undertray still intact and a close fit to the radiator?

What about the top cover for the radiator?

Is there any room for air to escape around the side of the radiator?

Why is the number plate mounted in the radiator airstream?

Good points. My undertrays are not on the car. They were removed to do a lot of work, and were never put back on. Plus in the SS2000 rules, you not allowed undertrays. I could probably argue this point as they came standard on my car, but I thought it better to just avoid the issue.

We are making up some alloy ducting for around the radiator at the moment, and removing the number plate

[Mr Revhead]

yeah too low water pressure.
or worn fins on pump.

no undertray? surely they mean custom made aerodynamic undertrays.
not standard undertrays.
fivebob has a very good point there. the ducting/trays around a rad can have a huge effect on airflow through the rad.
not only infront of it, but behind it as well. if something is allowing pressure to build up behind the rad then how can air flow through it?

[mr30%jr]

making water flow faster through the rad inst allways better it doesnt have time to cool.

having oposite outlets has a few pluses,

water is being taken from the botom. wherer its cold.

water is flowing from the botom of the tank and entering the top so has a tendancy to flow across the rad more evenly

[pureadrenalin]

yeah too low water pressure.
or worn fins on pump.

Water pump was replaced last week. Old one looked fine. Man I hate replacing things when they are in good nick.

no undertray? surely they mean custom made aerodynamic undertrays.
not standard undertrays.

Yeah, I know, they probably do mean aerodynamic aids, but why risk someone complaining.

fivebob has a very good point there. the ducting/trays around a rad can have a huge effect on airflow through the rad.
not only infront of it, but behind it as well. if something is allowing pressure to build up behind the rad then how can air flow through it?

Agreed. We are building ducting/trays at the moment. Just to complicate construction, my bumper is removable via 7 quarter turn clips, so anything we construct can’t attach to the front bumper
There isn’t anything to allow pressure to build up behind the radiator after last night. A grinder saw to that. Bye bye frunk.

[fivebob]

There isn’t anything to allow pressure to build up behind the radiator after last night. A grinder saw to that. Bye bye frunk.

So what is going to create the low pressure area behind the radiator now???

Random removal of things which actually aid the airflow is not the answer, unless you plan on replacing them with something more effective.

[pureadrenalin]

making water flow faster through the rad inst allways better it doesnt have time to cool.

Correct.
I’m not trying to make it flow faster; I’m trying to make the flow thru the fins/tubes even.
Doubling the number (hence area) of inlets/outlets will halve the flow rate through the inlet/outlet, but the since the fins/tubes are not being touched, the flow rate through them will be exactly the same.

water is being taken from the botom. wherer its cold.

Why is it colder?

[Leon]

Ring SS2000 series scrutineer, and ask if you can refit factory undertrays.

[touge rolla]

There isn’t anything to allow pressure to build up behind the radiator after last night. A grinder saw to that. Bye bye frunk.

Now make a huge vent on your front bonnet so after the air flows through the radiator it's up out the bonnet and over the car. Should make for some good downforce too.
May cause some difficulty with motorsport regulations however.

[fxgt race]

I think under ss2000 rules you can run standard undertrays and i am pretty sure you can run custom ones as long as it dosen't come pass the front axles which dosen't mean you can run yours to the rear axles,I will ring someone in the know tonite and let you know.

[mr30%jr]

heat rises hot water will allways be at top. your hot water cylinder in a house is a very good example of this.

the sw20 rad is only like that due to design because of the underbody and new space

i stress thats its not your rad causing your your overheating. the faintest $&#$% headgasket will over heat the shit out of the car. and we all know of the 3s issues.

[FXGTV]

my mr2 makes boiling sounds after a drive it with a bit of spirit... now that cant be good