Hill climb and cooling issues.

[fxgt race]

standard is ok as long as they don't come past the front struts,and there is someone running there own carbon one to the same specs,must be higher than the rim incase you get a flat tyre it won't hit the ground

[RedMist]

Its a twin pass radiator!

It's designed to have both fittings on one side (or top) of the radiator. There is a baffle half way through the top tank, it forces all water through one half of the core to the bottom tank and then pass to the other side of the tank where it passes again to the top. It's considerably more efficient than a stock single pass radiator as it causes more turbulance in the core. The slightest problem with this baffle causes it to leak and water to simply pass across the top of the radiator. Lower quality radiators simply seal this with a sealant whereas it should have been 360 degree welded. My bet is either you have an older and damaged rad, a cheap and damaged rad, or it was never constructed corretly in the first place.

[fivebob]

Its a twin pass radiator!

Don't think that's possible. The end tanks are on the side of the radiator not the top/bottom, and there is one inlet/outlet fitting in each end tank. Any baffle in the end tank would cause the collant to only flow through half the radiator

[jondee86]

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.

There was a time when car engines had convection cooling systems, that
worked perfectly well without a pump. The water ran from the head to
the top of the radiator, and returned from the bottom of the rad to the
block. Not exactly high performance, but it got the job done.

I have installed a lot of hot water heating radiators, and the preferred
radiator design invariably has connections TBOE. The reason is to obtain
a balanced hydraulic circuit. The flow connection is at the top, and the
return at the bottom, to work with the natural convection effect.

A car radiator is sized to dissipate the quantity of heat generated by
the engine at full load. At that time it will (theoretically) have a high
airflow, as the car should be going fast If it is not e.g. when towing on
an uphill grade, the radiator may overheat. On the other hand, when
cruising around on part throttle, the radiator will have excess capacity,
and the bottom of the radiator may feel cold.

This would be more apparent in a TOE design, where the hot water
would be inclined to stay at the top of the radiator. When pushed hard
(as in a race) the bottom of your radiator should be near enough as hot
as the top. If it is not, then you do have a circulation problem, or the
radiator capacity is simply not sufficient for the engine output. Better
airflow thru the rad should help.

Cheers... jondee86

[RedMist]

Its a twin pass radiator!

Don't think that's possible. The end tanks are on the side of the radiator not the top/bottom, and there is one inlet/outlet fitting in each end tank. Any baffle in the end tank would cause the collant to only flow through half the radiator

Whoops, didnt note the tank location. Currently on dialup speeds so pics didnt load.
So Toyota are relying on core resistance to feed the entire radiator?

[fivebob]

So Toyota are relying on core resistance to feed the entire radiator?

Pretty much, that along with the angle of the inlet/outlet pipes end tank shape. Though I haven't had one apart to see if there are any internal baffles in the end tanks to direct the flow, but I doubt that there would be.

[pureadrenalin]

A car radiator is sized to dissipate the quantity of heat generated by
the engine at full load. At that time it will (theoretically) have a high
airflow, as the car should be going fast If it is not e.g. when towing on
an uphill grade, the radiator may overheat. On the other hand, when
cruising around on part throttle, the radiator will have excess capacity,
and the bottom of the radiator may feel cold.

This would be more apparent in a TOE design, where the hot water
would be inclined to stay at the top of the radiator. When pushed hard
(as in a race) the bottom of your radiator should be near enough as hot
as the top. If it is not, then you do have a circulation problem, or the
radiator capacity is simply not sufficient for the engine output. Better
airflow thru the rad should help.

Cheers... jondee86

Agreed.

Whole radiator should be the same temp, even without the mod’s I’ve done. It’s rather hard to check tho. It’s kind of like trying to check tire temps. Things change on the cool down lap.
Annoyingly the top of the radiator in the SW20 is behind a large ‘impact’ bar, so there’s not much I can do to improve direct flow into the top of the radiator short of removing this bar (but I like the safety feeling it gives me), and modifying the front bumper.

[Santa'sBoostinSleigh]

heat as such doesnt rise, hot air is less dense than cold air, therefore the hotter the air, the less dense it is, therefore colder more dense air sinks below less dense air (same for all gases)

now from memory water behaves slightly differently, ie ice is cold, but it floats on top of water (if it didnt we would all be fuxed)
however as you get down deeper in water it gets cold again
on the other end of the scale, steam (water in its gaseous form) is far less dense than water so of course will sit above water.
i dont have time do research more into it to prove or disprove my recollections!


Garnett, its possible from what others have said about the HG, the car has been hot on a few occasions, and maybe this is why its gone pop now?
You didnt even up having the frunk vented during SS2000 Puke did you? this would presumably created a huge area of 'dead hot air' which wouldnt have helped matters.
If this is true, it could possibly have also caused your battery problems to worsen

AGM batteries are designed to be operated within a wide temperature range -15degC and +55degC. The optimum operating temperature is 20degC
Higher temps reduce the lifetime...above 40degC there is a risk of thermal runaway
...
Battery temperature affects the available capacity

Batteries are generally rated at 20degC, so above this temp, you are ok
The graph i have here for an Exide Marathon L battery, states that at 50degC, the battery life is less than 2 years (at 20degC its 12 years)

food for thought?

I suggest looking at installing a AGM/Gel battery in the compartment behind the passenger seat as discussed the other week. I guess due to everything being electric in a MR2 this means battery size will always have to be fairly large, but as you mentioned, non-electric PS may be an option to reduce this load.

[pureadrenalin]

now from memory water behaves slightly differently, ie ice is cold, but it floats on top of water (if it didnt we would all be fuxed)
however as you get down deeper in water it gets cold again

LOL this made me laugh. It dosn't quite work like that with ice.


I don't think its the head gasket, but since I am now taking the head off, I will be replacing it.
I didn't really have the uncontrolable cooling issues I did at manfield this time round, but we've modifyed a fair bit.

From the sound of it, the engine troubles are deffinatly in the head. My guess is that a shim has come loose.

Correct, frunk wasn't vented, but I guess i have some time to rectify that now
Battery problems are from having a crap battery, and no altanator belt

[rollaholic]

i believe the reason ice floats in water is because it expands as it freezes, thus per cubic cm has less mass than liquid water

[allencr]

The bottom of the radiator is stone cold, gradually getting hotter towards the top. The inlet and outlet to the radiator are both at the top, and it seams that the hot water is just running across the top of the radiator.

Seems to be running across the top to me too.
Is the inlet tank missing a plate that would diffuse the flow and make it a lot more even?
Has it been re-cored with larger core tubes, bigger defintly isn't better in this case?

[matt dunn]

I don't think its the head gasket, but since I am now taking the head off, I will be replacing it.
Battery problems are from having a crap battery, and no altanator belt

Just re-read thru your project thread.

I see you did a lap of two with no alt belt.

Having done that myself to finish a race I can tell that you that your
waterpump also looses it's drive,
so there is no water flow around the engine.

The engine can overheat and do a head gasket,
without getting too hot on the gauge, as the hot stuff doesn't make it out to the temp sender.

In my case it did a gasket and also had to skim the head to get it flat again.

[fivebob]

I see you did a lap of two with no alt belt.

Having done that myself to finish a race I can tell that you that your
waterpump also looses it's drive

Not on a 3S, the water pump is driven off the cambelt

[matt dunn]

I see you did a lap of two with no alt belt.

Having done that myself to finish a race I can tell that you that your
waterpump also looses it's drive

Not on a 3S, the water pump is driven off the cambelt

AH, good point.