Overheating problems

SeanDezart

Well-Known Forum User
Not funny at all - I've just lent my square (made from ally) crossflow rad to the GrpIV here that had 'an ally rad' with overheating problems because I was convinced that warter was not taking the time to be cooled.........

Later this year I shall be offering for sale less expensive versions of the Arizona Zcar rad for that very reason.
 

johnymd

Club Member
It IS funny to Me. The misconception of speeding up the water flow for better cooling has been around for a long time. Ask a plumber about how household radiators work. They throttle back the flow to get the required temperature drop across them. Same principle applies to any radiator.
 

SeanDezart

Well-Known Forum User
It IS funny to Me. The misconception of speeding up the water flow for better cooling has been around for a long time.

Yep - people have removed their thermostats to allow hot water to escape early enough..........but then if it rushed back into the block still hot............!:(
 

racer

Club Member
More venting ideas
 

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racer

Club Member
Now there's a man who knows!
Lifted from the site.

"A common misconception is that if coolant flows too quickly through the system, that it will not have time to cool properly. However the cooling system is a closed loop, so if you are keeping the coolant in the radiator longer to allow it to cool, you are also allowing it to stay in the engine longer, which increases coolant temperatures. Coolant in the engine will actually boil away from critical heat areas within the cooling system if not forced through the cooling system at a sufficiently high velocity. This situation is a common cause of so-called "hot spots", which can lead to failures."
 

racer

Club Member
And more

"Years ago, cars used low pressure radiator caps with upright-style radiators. At high RPM, the water pump pressure would overcome the radiator cap's rating and force coolant out, resulting in an overheated engine. Many enthusiasts mistakenly believed that these situations were caused because the coolant was flowing through the radiator so quickly, that it did not have time to cool. Using restrictors or slowing water pump speed prevented the coolant from being forced out, and allowed the engine to run cooler. However, cars built in the past thirty years have used cross flow radiators that position the radiator cap on the low pressure (suction) side of the system. This type of system does not subject the radiator cap to pressure from the water pump, so it benefits from maximizing coolant flow, not restricting it"
 

Aceman

Well-Known Forum User
We have similar discussions on the rotary forums (due to the temps the Wankel engine runs at!).

Most seem to agree with many of the above comments - oil cooler (for us Rotary boys that means getting a second cooler to aid the first one!), bigger rad, better rad ducting.

Undertrays seem to work very well on the rotarys - something to do with the low pressure under the car sucking air in to aid with blowing it into the bay or something (I used to understand Physics being a UCL honours Physics graduate, but the knowledge escaped me when I left university for the real world).

Similarly, there's huge debates about "bonnet lifting" (in your case, running the Z with the bonnet on latch). Something to do with there being designed a high pressure area at the base of the windscreen, which when you lift the bonnet at the windscreen end actually pushes the hot air back into the engine bay, rather than letting the air flow through the bay and out at the windscreen.

As such, to summarise what we do, add an oil cooler, up the radiator core size, duct air too it better (it sits as standard infront of the intercooler as an FYI) and pop an undertray on to utilise the air flow from under the vehicle.
 

Rob Gaskin

Treasurer
Staff member
Site Administrator
John, you know my views on this.

I realise it is standard practice to fit inter-coolers in front of rads but it must influence the ability of the water rad to cool the water. After a long drag up the Kemel straight at Spa when your inter-cooler would be hotter than 'normal' from the turbo at high boost for so long it is surely going to affect water cooling.

I know folks will disagree but it just doesn't seem sensible to stick a rad in front of a rad. What about this: Mount the intercooler further forward and direct the air flowing through it 'up and away through ducting and a bonnet vent. Duct air from under the car up between the intercooler and the rad and out through more bonnet vents/inspection flap apertures.
 

Sylv1

Well-Known Forum User
I have the opposite trouble... engine works at too low temp in normal driving (yes, not so common situation :D)


I've undertray and uper tray to duct the air from the grill to the top of the rad and the biggest alloy rad I could fit in the car
+ an oil rad

If you want pics of trays and rad, I can send them.
 

tel240z

Club Member
Do you use a thermastat ? yes i spotted your undertray and ducting, very nice, also your luminos pink exhaust straps ;)
 

TomZupra

Well-Known Forum User
I have some thermocouples you can borrow if you need to do some localised temperature monitoring, if you get some time on a rolling road let me know and I'll knock up a data logger and see how many probes I can get my hands on.
 
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Rob Gaskin

Treasurer
Staff member
Site Administrator
John, you know my views on this.

I realise it is standard practice to fit inter-coolers in front of rads but it must influence the ability of the water rad to cool the water. After a long drag up the Kemel straight at Spa when your intercooler would be hotter than 'normal' from the turbo at high boost for so long it is surely going to affect water cooling.

I know folks will disagree but it just doesn't seem sensible to stick a rad in front of a rad. What about this: Mount the intercooler further forward and direct the air flowing through it 'up and away through ducting and a bonnet vent. Duct air from under the car up between the intercooler and the rad and out through more bonnet vents/inspection flap apertures.

Coming at this from another angle, could the water rad be affecting the efficiency of the intercooler i.e. blocking the through-flow of air and so your incoming 'charge' is too hot. Are there any sensors monitoring this?

Just a thought ;)
 
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