Header tanks = plumbing
Discussion
My track car always ran a bit too hot, it'd be the limiting factor on how long I could stay out, it'd get up to 115oC in 15 minutes or so. Now that was already running a high volume alloy rad and an external 13 row oil cooler - but then it did have to deal with 130bhp over stock power.
Now the cars being rebuilt and will be approximately 200bhp over stock so I want to improve cooling again and I figure more coolant volumes got to be a good thing so thought addition of a header tank would make sense. Thing is whats the best way to plumb them in and how or do that effect expansion tank requirements?>
Now the cars being rebuilt and will be approximately 200bhp over stock so I want to improve cooling again and I figure more coolant volumes got to be a good thing so thought addition of a header tank would make sense. Thing is whats the best way to plumb them in and how or do that effect expansion tank requirements?>
Also having it in mind its a track only car and currently gets to hot quite easily would ditching the thermostat be an issue? I wonder because I have with the rebuild dumped the "all ways hot" heater matrix that allowed coolant to circulate when the thermostat was closed. I thought if I ditch the thermostate then I won't have to run a "by pass" pipe as the coolant will always be circlating.
Before someones says why did I ditch the extra rad / matrix - its because I have no interior at all now.
Before someones says why did I ditch the extra rad / matrix - its because I have no interior at all now.
This new builds got an even bigger rad (52mm over 37mm) and had the oil cooler moved into more air flow - I just want to be sure as ideally it'd run at 80oC so 35oC seems a lot to have to loose.
This is the total sum of all coolant / oil flows as it stands :-
This is the total sum of all coolant / oil flows as it stands :-
Edited by Herman Toothrot on Saturday 22 October 21:28
Airflow through the radiator is key imho. Air will take the path of least resistance and a radiator has fairly high resistance to airflow, so if there are gaps around the rad through which the air can pass you're not making the most of the radiator you have got.
From your picture, but it looks to me as though there's going to be a large gap between the top of the rad and the bonnet, with a big hole in the bonnet pin plate through which to pass air. What about around the sides and under the bottom of the radiator? Foam may not look pretty, but it's very good at directing airflow.
I'm not entirely convinced that where you've placed holes for air to the oil cooler isn't in fact a low pressure zone, which could actually be drawing air out if that is the case. The oil cooler just looks to be floating in the breeze - do you have any panelling to direct airflow through it?
If you've eliminated all routes for air to bypass the rad and you're still having problems then look at airflow out of the engine bay.
I'd be loathed to try running without a thermostat. Not having a thermostat won't stop the car overheating, and some engines don't flow water properly without one. Stick with the bypass pipe.
From your picture, but it looks to me as though there's going to be a large gap between the top of the rad and the bonnet, with a big hole in the bonnet pin plate through which to pass air. What about around the sides and under the bottom of the radiator? Foam may not look pretty, but it's very good at directing airflow.
I'm not entirely convinced that where you've placed holes for air to the oil cooler isn't in fact a low pressure zone, which could actually be drawing air out if that is the case. The oil cooler just looks to be floating in the breeze - do you have any panelling to direct airflow through it?
If you've eliminated all routes for air to bypass the rad and you're still having problems then look at airflow out of the engine bay.
I'd be loathed to try running without a thermostat. Not having a thermostat won't stop the car overheating, and some engines don't flow water properly without one. Stick with the bypass pipe.
It was previously all ducted and sealed - it's all open and exposed as it's still being built at the moment. I'm aware the removal of the thermostat won't help cooling, it's just simplification - removing the bypass and if it's really not needed to speed up engine warming.
Another friend with a similarly powerful car 260bhp (pre my recent increase) with same engine but side by side custom oil cooler / coolant radiator also found track cooling problems. So I feel it's right to be approaching it with a 'get it as cool as I can' attitude.
So has anyone any suggestions as to where I should plumb a header tank into the system?
Another friend with a similarly powerful car 260bhp (pre my recent increase) with same engine but side by side custom oil cooler / coolant radiator also found track cooling problems. So I feel it's right to be approaching it with a 'get it as cool as I can' attitude.
So has anyone any suggestions as to where I should plumb a header tank into the system?
An expansion tank is only going to add about a pint of additional coolant to the system - a pretty insignificant amount. At best it's going to add a slight delay to the onset of overheating, but it's not going to cure the problem.
If there is proper ducting in place to the radiator, then you need to start looking at pressure differentials either side of it. Modifications to the undertray, and bonnet vents can both be used to this effect, but you'll need to base these on proper testing using something like the Dwyer Magnehelic gauge.
If there is proper ducting in place to the radiator, then you need to start looking at pressure differentials either side of it. Modifications to the undertray, and bonnet vents can both be used to this effect, but you'll need to base these on proper testing using something like the Dwyer Magnehelic gauge.
I had been wondering about venting the bonnet. As standard the engine bay is a dead end other than the transmission tunnel. The undertray goes from against the back of the radiator to the stock pressed subframe - I now have a tubular subframe with a lot more free space so if I leave it more air willexit the back of the engine bay under the car.
I know the base of the windscreen / back of the bonnet is a very high pressure area - the OEM heater ducting inlet was in this area and I plugged the hole as a temperary measure with duct tape and it blew open immediately.
I know the base of the windscreen / back of the bonnet is a very high pressure area - the OEM heater ducting inlet was in this area and I plugged the hole as a temperary measure with duct tape and it blew open immediately.
Sounds like air egress is the problem then.
Usually the front half of the bonnet is low pressure so the best place to put vents, and the rear half is high pressure. This is where some accurate pressure data is needed for best results.
As for the undertray, again testing various sized trays is really the only way using pressure differential data. If you can rig up a temporary one to hack about until you find the best solution it'll save messing up the proper undertray too much. Ally sheet, perspex, mdf are all good makeshift materials. Play about with undertray lengths, angles, and possibly spoiler arrangements.
Usually the front half of the bonnet is low pressure so the best place to put vents, and the rear half is high pressure. This is where some accurate pressure data is needed for best results.
As for the undertray, again testing various sized trays is really the only way using pressure differential data. If you can rig up a temporary one to hack about until you find the best solution it'll save messing up the proper undertray too much. Ally sheet, perspex, mdf are all good makeshift materials. Play about with undertray lengths, angles, and possibly spoiler arrangements.
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