Quick antifreeze question
Discussion
What's the minimum amount of antifreeze I can get away with? It's a road legal trackcar and it lives in East Anglia so it should never see less than about -5 deg C as I'll never be driving it to Finland. Anyone have a handy table of concentration vs. freezing point? Also thinking about corrosion inhibition although I doubt the car will still be alive in 2 years so maybe I shouldn't be too concerned 
It's a 20 year old MX5 so we're talking about the older type (ethylene glycol?).
It's a 20 year old MX5 so we're talking about the older type (ethylene glycol?).
Edited by T0MMY on Saturday 5th October 15:39
Different makes may have a different concentration spec, check the mixture rate on the back of the bottle and work it out.
But I agree above, for the cost may as well use the recommended amount. Its not just an anti freeze though, so its in your best interests to use the right amount as it increases the boiling point too.
But I agree above, for the cost may as well use the recommended amount. Its not just an anti freeze though, so its in your best interests to use the right amount as it increases the boiling point too.
I'm not trying to save money
Basically I need all the cooling I can get as the car is modified and generates a lot of heat as a result. Antifreeze has lower specific heat capacity and thermal conductivity than water so I don't want to put too much in there. I already have a larger radiator and a higher pressure cap.
Basically I need all the cooling I can get as the car is modified and generates a lot of heat as a result. Antifreeze has lower specific heat capacity and thermal conductivity than water so I don't want to put too much in there. I already have a larger radiator and a higher pressure cap.
The car doesn't overheat on the road but I suspect it will on the track. I would estimate it is making somewhere in the region of 50% more power than standard which equates to a hell of a lot more heat (I guess it's proportional forgetting efficiency changes?). The original system would definitely struggle with the extra demands of track driving although it did cope when the car was standard (albeit with the heater on full blast!).
HustleRussell said:
Ditch the antifreeze altogether and use Redline 'Water Wetter'.
Having said that, if your cooling is borderline on the road I'd suggest you need to upgrade the system before you go anywhere near a track.
I will probably get some water wetter, seems the way to go. The reason I was asking about a minimum of antifreeze is because I do trackdays through the winter and don't want to have to drain the system down all the time then have to fill it on the morning of every trackday.Having said that, if your cooling is borderline on the road I'd suggest you need to upgrade the system before you go anywhere near a track.
To clarify, when the car was standard the cooling system was fine on the road and pretty much fine on the track, even through summer. I haven't tracked it since turboing it but whilst the standard system does cope with the extra power on the road I think it would struggle on the track, especially now I have added water cooling to the turbo. I now have a bigger alloy rad and the higher pressure cap so I think it should be ok but want to use a minimum of antifreeze just to help it further. Hence my question
I should probably get an oil cooler too but there's a limit to what I want to spend on this car.
HustleRussell said:
Ditch the antifreeze altogether and use Redline 'Water Wetter'.
Having said that, if your cooling is borderline on the road I'd suggest you need to upgrade the system before you go anywhere near a track.
i'd agree with that Having said that, if your cooling is borderline on the road I'd suggest you need to upgrade the system before you go anywhere near a track.
If specific heat capacity isd the issue that the Op is concerned aobut surely one of the waterless coolants would be the answer - although i've no idea what their freezing point is.
I guess heat transfer efficiency is the biggest issue as the turbo is a very effective run through heater and I want to dump that out as much as possible before the coolant goes through the engine. As I understand it water wetter is basically a surfactant so will improve transfer by reducing the surface tension of the water where it contacts the metal bits. Not sure if it also has a higher heat capacity too?
T0MMY said:
The car doesn't overheat on the road but I suspect it will on the track. I would estimate it is making somewhere in the region of 50% more power than standard which equates to a hell of a lot more heat (I guess it's proportional forgetting efficiency changes?). The original system would definitely struggle with the extra demands of track driving although it did cope when the car was standard (albeit with the heater on full blast!).
Again I find it very unlikely even a 50% increase in power would pose a problem. The Mazda would be heavily over-engineered, especially in that respect.I would suggest you have another problem. Whether it be the radiator used is of poor quality, or airflow through the radiator is not up to scratch.
Assuming water pump, thermostat etc are also in good condition.
As for water wetter, tried it on a few cars over the years, never made a single bit of difference.
Most standard cars will test their cooling system to the limit on a trackday, let alone one that's had forced induction bodged onto it. Honestly, there is no specific problem with the functioning of the cooling system as it is, it's just unlikely to be designed to cope with this much heat. The car has never overheated on track without the turbo or on the road with the turbo. The issue is combining track and turbo and frankly I'd be astonished if the standard cooling system had so much spare capacity it could happily accommodate track driving (which it's not really designed for), an extra 50% power (which it's definitely not designed for) and cooling the turbo itself (which it's also definitely not designed for). The turbo is plumbed into the existing cooling circuit rather than through a separate heat exchanger system so this alone dumps a shedload of heat into the coolant. Judging from your name I presume you know how hot turbos get!
I haven't tried the new rad yet as I just installed it today (hence asking about coolant mix as I need to fill it up!). It seems decent quality and comes recommended. I haven't done anything about airflow in particular but I have the undertray in place and all the seals around the front and rear of the bonnet and the lights are in good nick so it should be ok. I could start cutting holes in the bonnet but without knowing exactly where the low pressure spots are it could very easily be counterproductive
I haven't tried the new rad yet as I just installed it today (hence asking about coolant mix as I need to fill it up!). It seems decent quality and comes recommended. I haven't done anything about airflow in particular but I have the undertray in place and all the seals around the front and rear of the bonnet and the lights are in good nick so it should be ok. I could start cutting holes in the bonnet but without knowing exactly where the low pressure spots are it could very easily be counterproductive
Edited by T0MMY on Saturday 5th October 21:34
It's simple:
1) don't bother with any of the supposed "go faster" coolants, complete waste of time
2) Mix a test batch of coolant (normal antifreeze with tap water, (suggest 10/90% as starting point)
3) Stick a sample in a mug in the freezer (generally around about -5 min to -15max depending on where you set the dial, and also a mug full of plain tap water (to let you know you've left it in long enough
Slowly increase the concentration of antifreeze until you're confident in the freezing resistance!
(Edited because i can't add up to 100......)
1) don't bother with any of the supposed "go faster" coolants, complete waste of time
2) Mix a test batch of coolant (normal antifreeze with tap water, (suggest 10/90% as starting point)
3) Stick a sample in a mug in the freezer (generally around about -5 min to -15max depending on where you set the dial, and also a mug full of plain tap water (to let you know you've left it in long enough
Slowly increase the concentration of antifreeze until you're confident in the freezing resistance!
(Edited because i can't add up to 100......)
Edited by anonymous-user on Sunday 6th October 15:08
It might help to see what the temps are in the Cyl head . I used to see up to 120c in the head using the standard rad with temps of 105c coming out of the bottom of the rad .stock capacity was 9 litres . Bigger rad with 12 litre capacity and outlet temps dropped to 95 with 105 c peak at the head .
Not an mx5 but a fairly high output 4pot turbo set up
Not an mx5 but a fairly high output 4pot turbo set up
Simple answer to the original question, based on the most practical balance between protection and minimum antifreeze, I'd say 33% mix. (2 pints water to 1 pint antifreeze).
You could get away with 25% mix (3 pints water to 1 pint antifreeze) but I would not go any lower than that.
No great science involved in this answer, just my recollection of what worked in the old days before the 50% mix became standard dogma. Of course if corrosion protection is not an issue for you, you might get away with plain water just by leaving out the thermostat.
You could get away with 25% mix (3 pints water to 1 pint antifreeze) but I would not go any lower than that.
No great science involved in this answer, just my recollection of what worked in the old days before the 50% mix became standard dogma. Of course if corrosion protection is not an issue for you, you might get away with plain water just by leaving out the thermostat.
I went with about 25% in the end but I might put more in when it turns really cold. Might take the car out this weekend so that will be the real test of the cooling system. Bedford Autodrome or Blyton Park...frankly the massive straight at Bedford worries me but I guess I could short shift if I'm not trying to overtake anyone. Be easier on my brakes too.
T0MMY said:
What's the minimum amount of antifreeze I can get away with? It's a road legal trackcar and it lives in East Anglia so it should never see less than about -5 deg C as I'll never be driving it to Finland.
-10C is hardly an unusual temperature in the UK during Winter, and it can go quite a bit lower than this.More to the point your getting good advice from experienced members on here and not listening.
I have had 4 mx5s 2 of which have been used on track and don't struggle even in summer (not turbo). They run a 50/50 Antifreeze mix, standard cooling system.
I have a friend with a really homemade turbo conversion on an NA and his car doesn't overheat particularly.
It sounds to me like you have an issue, either your not getting rid of the heat be that due to air not going through the rad due to no air guides at the front of the car or air getting trapped in the engine bay, or you are generating too much heat, what is the mixture like on the engine? Just how bodged is the turbo conversion? StevieTurbo above has a lot of experience on these forums with tuning, if he's giving you advice it's generally going to be good advice.
Your car should not be marginal on the cooling front, if anything MX5s are massively over engineered cooling wise, on my last 5 an NA I went to town lightening I even ditched the expansion tank for weight savings as the temperature never moved on it so it didn't really need the expansion tank to push water in and out of as the engine went up and down in temp. My current build I am retaining the tank as it's following a slightly different path and I wouldn't advise people do ditch the tank, but it does make the point that the cooling system is not stressed.
I have had 4 mx5s 2 of which have been used on track and don't struggle even in summer (not turbo). They run a 50/50 Antifreeze mix, standard cooling system.
I have a friend with a really homemade turbo conversion on an NA and his car doesn't overheat particularly.
It sounds to me like you have an issue, either your not getting rid of the heat be that due to air not going through the rad due to no air guides at the front of the car or air getting trapped in the engine bay, or you are generating too much heat, what is the mixture like on the engine? Just how bodged is the turbo conversion? StevieTurbo above has a lot of experience on these forums with tuning, if he's giving you advice it's generally going to be good advice.
Your car should not be marginal on the cooling front, if anything MX5s are massively over engineered cooling wise, on my last 5 an NA I went to town lightening I even ditched the expansion tank for weight savings as the temperature never moved on it so it didn't really need the expansion tank to push water in and out of as the engine went up and down in temp. My current build I am retaining the tank as it's following a slightly different path and I wouldn't advise people do ditch the tank, but it does make the point that the cooling system is not stressed.
Also to add my two penniesworth
yes adding anit-freeze reduces the heat capacity very slightly, however it does a lot more than just prevent the water form freezing as it contains anti-foamin agents and water pump lubricant and also surface tension modifiers ( like water wetter)
so a 25% will give better cooling than water on its own
yes adding anit-freeze reduces the heat capacity very slightly, however it does a lot more than just prevent the water form freezing as it contains anti-foamin agents and water pump lubricant and also surface tension modifiers ( like water wetter)
so a 25% will give better cooling than water on its own
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