Quick antifreeze question

[T0MMY]

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?).

Edited by T0MMY on Saturday 5th October 15:39

[T0MMY]

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.

[T0MMY]

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!).

[T0MMY]

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.

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.

[T0MMY]

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]

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

Edited by T0MMY on Saturday 5th October 21:34

[T0MMY]

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]

wildoliver said:

More to the point your getting good advice from experienced members on here and not listening.

With all due respect I have to disagree.

Your experience of running a normally aspirated MX5 trackcar is not really relevant as it is a totally different situation and I am well aware that the standard cooling system can cope as I have done numerous trackdays prior to adding the turbo with no overheating issues. The experience of your friend worries me slightly when you say "particularly"...did it overheat or didn't it? Was that on a track or on the road? Also if he's using the dash temperature gauge and it has moved from the middle even a little bit then he has more serious overheating issues than he realises as the gauge is "desensitised" around the centre and only moves when the coolant gets very hot indeed (likewise, if you are only going on that guage in your n/a cars you may be running hotter than you think). As for not listening, well I've said numerous times the car has no overheating issues in as much as the dash gauge never moves (with the above concern in mind however). I am simply saying having not tested it with the turbo on track it seems eminently sensible to consider the possibility that the cooling system may not cope as it would have to be massively over engineered to do so. The extra power alone is probably adding 50% more heat, then you have the water coming through the turbo itself which obviously runs extremely hot. Combine that with the extra demand of track driving and I wouldn't be surprised if a turbo'd MX5 on track is having to shed literally twice as much heat as an n/a one on the road.

I'm absolutely certain Stevieturbo knows his stuff and I mean no disrespect at all but unless he has actually tried a turbo'd MX5 on track or has figures for both the headspace cooling capacity of the standard cooling system and the amount of extra heat generated with my setup then I'm not really willing to take his word for it as he's only really guessing based on what has worked on totally different cars.

Anyway, it's a moot point as I have booked Bedford for this Saturday so we'll see how the car gets on. Frankly I think the clutch may well be the weakest link and I'll be slightly surprised if I make it through the day without anything breaking at all If I have no overheating issues at 25% antifreeze I will add more anyway.

Edited by T0MMY on Wednesday 9th October 17:08

[T0MMY]

Mikey G said:

Well it seams your such a clever person I wonder why you asked the question on here in the first place?
Don't forget BBR was doing MX5 conversions and still do, so your not the only one out there. Is a bigger cooling system part of the BBR conversion kit? (genuine question)
I hope for your sake that your not trying to increase the cooling capacity to mask an underlying problem with your AFR's. Or that track day could end up costing your more than you bargained for.

Clever enough to not risk my engine on the back of some comments from people I don't know, none of whom have said they actually have any experience of this situation or have offered anything more than opinion. Also, I think you'll find I never asked if I needed more cooling, I asked what protection different concentrations of antifreeze offered. I've already asked about extra cooling on two MX5 forums and everyone running a turbo trackcar has said I need it...in fact that what I've done might not even be enough. I don't know if BBR modified the cooling system but I do know that a) they ran considerably less power and b) that was a kit for road cars not specifically for track cars.

wildoliver said:

No one is trying to deny that your car will need more cooling than a NA car. The point that is being made is if your car was marginal on track (needing the heater on) without the turbo and you are now having concerns about antifreeze mixture then you have bigger concerns than said mixture, this isn't an F1 car where you are calculating every detail down to the nth degree to make weight savings and specing a smaller rad and not running antifreeze would save weight and be acceptable for cooling, this is an mx5 with a turbo strapped to it, the standard cooling system should be acceptable, your upgraded cooling system should be more than acceptable, but if it isn't then don't go looking at the antifreeze mixture because the tiny improvements you can gain there aren't worth the payoff for not running enough antifreeze.

I suggest if it does run hot (and I agree your clutch is more likely to go first as this is the weak point on turbo MX5s not the cooling system) then look at the air ducting side of things as air flow will have a big impact to your overall running temp. Also look to try to get the heat from the turbo out of the engine bay, from my days of playing with supercharged Alfas the killer was always engine bay heat. The more heat you can get away from that turbo the more reliable it will be.

Thanks, some good points although I do have to ask, when you say my upgraded cooling sytem should be more than acceptable is that based on some knowledge of this situation? I agree that the difference the antifreeze makes isn't that great but just thought I may as well do as much as I can.

As for air ducting, I am indeed worried about engine bay temperatures but I don't really want to start hacking holes in my bonnet. From diagrams I've seen of airflow over the front of an MX5 you really only get low pressure about half way up so you'd need to cut a hole. Lifting the rear of the bonnet or taking off a headlight will pressurise the engine bay and bugger up the airflow through the radiator completely. Not sure what other free and easy mods I could do unless I could improve the undertray or seal the front of the engine bay better.

Ultimately, by plumbing in water cooling for the turbo I've shifted that heat issue a little bit from the turbo to the cooling system I guess.

Edited by T0MMY on Wednesday 9th October 18:34

[T0MMY]

Ok, that's interesting. Perhaps explains why HKS say water cooling the turbo is not necessary (I didn't want to chance that so hooked up the water cooling). I was indeed worried about heat soak with the engine off so I've tried to promote thermal siphoning with the positioning of the pipe work but as it's a top mount I was a bit stuck for space with the angles of the fittings I had.

[T0MMY]

wildoliver said:

On another point if you have the water cooling set up it's well worth looking at getting an electric pump to run after the engine switches off to pull the heat out of the turbo.

I think as this is no longer a daily driver I don't need to worry so much about that as I can do cool down laps. I only do open pit lane days so don't need to worry about wasting track time!

I think I've done all I'm going to do cooling wise now, so we'll see how it goes on saturday. I will be utterly astonished if the clutch survives the day but didn't see the point in assuming it won't take it without actually trying it first. I'll try to go a bit easy on it anyway. Beinteresting to see how the brakes go too...they were excellent when the car was standard but I'll be hitting the braking zones a lot faster now and the pads are a little thin now so there'll be a lot of heat going into the fluid.

Edited by T0MMY on Thursday 10th October 17:33

[T0MMY]

Eh?

[T0MMY]

Why do I get the feeling that the default position on this forum is that any new poster is an idiot

The clutch is not iffy, it's fine on the road, I just hadn't tried it on track with the turbo. No point in assuming it won't take it and shelling out for a better one if the standard one is fine. And when I said the pads were thin I (obviously) didn't mean they didn't have enough meat left to do a trackday, they just aren't very thick so will transmit more heat to the fluid. I obviously would not do a trackday knowing the pads will not survive the day!

Anyway, I did the trackday today and the car survived. The clutch was mostly ok but I got a bit of slip at the end of longer runs so I think I'll get an upgraded one as I don't want to have to nurse it. Cooling wise the car was fine and the brakes were ok too despite the thin pads. The exhaust baffles didn't fair so well and I have a power steering leak too. Also the gearbox was a bit of a pig when it got hot but might just need an oil change.

Might stick up a video if anyone is interested. Seems a lightly turboed MX5 is a bit of a giant killer