Has anybody who does a lot a trac days experienced the standard radiator not having the capacity to cool the engine to be able to do say 10 hard laps.
I do quiet a few trac days and am about to change my old radiator as it’s nackered, but before replacing it with a standeard one was considereing an upgrade.
Any one had any experiences they would care to share?
If your engine is standard(ish) then a new standard radiator should be fine for track days, as you are unlikely to be racing hard up someone’s rear bumper and therefore not getting a decent airflow.
My new (very cheap!) radiator in my standard 1.6 Mk1 withstood the rigours of a seriously hot day absolutely caning it in 1st & 2nd gear over a very long near-stage that was something like 9 miles long.
It has also easily coped with track days at Brands Hatch so I would say yes, a standard one will be ok, but if you want some extra margin just in case then of course a deeper core version will do the trick.
However do make sure that your electric fan is in good shape as you’ll have more bother with possible overheating immediately after coming off the track.
I use a standard radiator on my turbo 1.6, and have done for years. The car is used for drifting, which is more abusive to cooling systems than track days (higher revs more of the time and less cooling air flow), but still it’s been fine.
Whilst I agree with the guys above, my standard one let go at the top, where the aluminium bends over the plastic. I upgraded to the MX5 Parts performance one and have NEVER suffered any overheating problems since. Oh, and it’s shiny!
Thanks for the advice guys.
I would add to the good advice above that the standard rads can easily become blocked with sediment/corrosion, causing serious flow problems and overheating when pushed hard. I replaced my rad a year or so ago for this reason but outwardly it looked immaculate. Try testing the rad flow by putting a hose in the top hose port and making sure of a clean flow from the bottom hose port. You can also test for cold spots on the rad after a run but be careful of the fans :-)
The Ma5da guys usually use an aluminium performance rad but they are putting out around 140bhp and giving the cars a serious hammering week after week - my vote would be to check out your rad and look to replace with standard - around £70 as opposed to £300+ for performance.
Your flow test will only show if the entire radiator is blocked, not if half the runners are blocked.
Cold spot test is the way to do it, using an infra-red remote temperture sensor if possible, and it helps not to have AC so you can get to the front of the rad.
Hi Captain Muppet
Appreciate the reply but this certainly was not true with my 1.6 rad or others I have tested before selling/scrapping. Quite simply a healthy rad should expel water from the bottom outlet as quickly as it enters at mains pressure through the top. If it doesn’t it is partially blocked and the backup of water will be forced back through the top outlet. When I took my rad apart, the waterways were very, very narrow and blockages are AFAIK not reversable.
I would also recommend this test to anyone fitting a secondhand rad as it can be performed off the car and could save time. My car only showed signs of overheating after a long continuous blast(70 miles+) down the motorway on a hot day and I reckon the rad had needed replacing for years.
Yes, a really blocked radiator will spew out water from the top, but a partially blocked radiator could still flow all the water out of the bottom despite having a proportion of the runners blocked (the combined flow area of the runners is larger than the flow area of the inlet/outlet pipes). So you could test it, think it was fine but actually have a dead area. A partially blocked radiator will not reject as much heat as a clear one, even if they both have the same flow rate through them.
A flow test tells you that the radiator is not entirely blocked, rather than telling you that the radiator is entirely clear.
I’m going to cut to the chase having sold a number of secondhand radiators, as well as scrapping others that don’t flow.
In order to test a secondhand radiator that has been purchased from an unknown source, the simplest method is to check the flow with a hosepipe. I have never come across a totally blocked MX5 rad but a partially blocked rad will not allow the flow of a hosepipe under mains pressure to go from top to bottom. The fine flow channels in an MX5 rad will fail this test, pushing water back out of the top hose port if there is a corrosion buildup. Fitting a secondhand rad without testing with a hosepipe first, unless the part was bought off me 
is ill advised.
Best advice is to fit a new rad but if buying secondhand, make sure that the unit is guaranteed and test it first before fitting.
If you are worried about your own rad, checking for cold areas after a run is a good way to confirm that the there is a problem. MX5 rads do have a limited lifespan, even with perfect servicing. Most of the failed ones I have come across appear corroded rather than blocked through sediment.
I understand that you have done this test lots of times, but a partially blocked rad can still pass it. Say just one runner of the rad was blocked - your flow area will be decreased by just 1.4%. There is no way sticking a hose pipe in the top and looking at the flow out of the bottom will spot this because the flow area of the remaining runners is still larger than the flow area of the outlet pipe.
What is the threshold for spotting blocked runners with this test? 2.8%? 10%? 20%? No one knows. You don’t cut open radiators that pass your test do you?
Yes it will weed out a very blocked radiator, but it won’t find every blockage. Even if you used a controlled inlet pressure (and “mains pressure” is variable) and measured flow rate and pressure delta you wouldn’t be able to spot small blockages. It’s a great test for weeding out scrap radiators, but it isn’t a rigerous enough test to prove the radiator is perfectly clear.
The important thing the radiator has to do is reject heat, and mass flow is only half the story - you need surface area for heat transfer.
Not had too much experience of failed rads on other cars but have come across a number on the MX5. In truth the MX5 temp guage sits at just below 12 o’clock for ages before indicating overheating. The car runs very efficiently unless there is an engine problem and most of the time will display no symptoms of a blocked rad. Track days and thrashing down the motorway, or even up, on a hot day may be the only opportunity to confirm a problem without checking for cold spots on the rad itself after a run.
When testing in Coventry a healthy rad will flow all output from a hosepipe at mains pressure. This may be different down here in Devon where the mains pressure is a lot higher and seems to blow the fixings of my hosepipes 
If the flow test fails to any extent, the rad is scrap. Never found one with anything more that a small trace of sediment - always corrosion. Not sure why, with regular servicing and good antifreeze discipline, corrosion has a chance of occuring ? If corrosion does occur it is likely to affect the whole rad, so I imagine this is why the flow test works for me. Take an old rad apart - remove the tanks and check the narrowness of the flow channels - difficult to get even a thin knife blade into them.
I have never found a way to recondition a blocked rad. Be interested to hear of any refurbishing techniques anyone has successfully used.
I did this most recently on a Toyota Soarer twin turbo, where the only
alternative was to wait for one to be shipped from Japan at significant
expense, MX-5 radiators are not expensive and I don’t really think it’s worthwhile but the process I used is as follows
Remove the rad from the car and lay it flat with the connections pointing upwards, preferably with around 9-10 inches of straight hose on each large connection, and any overflows blocked off, then pour in a boiling solution of acid descaler and rock the radiator to keep the solution in motion. The solution will cool quickly. Drain the solution and check for improvement, repeat as necessary It’s important not to leave the solution in for too long as it may attack the rubber seals used if the radiator has plastic end-caps.
Though I have found this a very effective way to clean a radiator internally the use of a boiling solution of even dilute acid can be very dangerous and suitable HAZ-CHEM precaution must be taken ( Rubber gloves and eye protection are a must ). Anyone who tries this does so entirely at their own risk, please be very careful.
Agreed
M-m
I put one of the ebay 52mm rads on my Supercharged 10ae (non intercooled) and it ran through France and Spain without a hitch at 37 degree daytime temps.