Choosing A Big Radiator, Over Cooling?

[Slo 283 1 Cars]

If its over heating in traffic it can only be the thermostat fried or cooling fan not good enough (that fan with no cowling pretty much speaks for itself lol).

 

I finished my turbo project in june with a brand new 205 bog standard rad and pipes, new water pump and a cheap £20 slimline fan and then the weather went into the 30's, was a bit nervous when stood with the hot sun baking down but it was spot on although the fan was on and off considerably more than when it had the 1.9 in it.

 

Cant see a v6 creating that much more heat than a turbo even if its fills up the engine bay more (less air flow space) the turbo heat goes up insanely fast if your not careful, infact its runs a hell of a lot cooler now than it did originally when it was in my 605 (with a radiator more than twice the size of the 205 rad and 2 massive cooling fans).

 

I do also have an oil cooler though rather than the original heat exchanger so that may contribute a big difference.

[allanallen 528 2 Cars]

This is all very very well and good, but at the end of the day I don't want to lunch a engine that costs more than most GTI's........ For the sake of a couple hundred £ I'll be finding a big radiator to fit.

Your rad is fine, it's the lack of cowling and probably the piping that's the problem as everyone is telling you! Why ask for advice when you're not prepared to listen. You clearly want a bigger rad so just fit one, use a tape measure, see what'll fit and shove it in.

There's some good advice in this thread, wether you publicly admit it or not I'd listen to it or the only thing that will 'lunch' your 'worth more than most gti's' engine is your negligence.

[welshpug 1,621]

406 Rad -

 

32mm thick core btw, this barely fitted into a 306 Rallye that I helped Adam B convert a few years back.

 

 

 

 

and this is the rad that Renault used on the clio, its actually a laguna/espace/velsatis Radiator.

 

 

 

 

you can see it is rather wide, so I doubt it will fit, its also a bit taller.

 

 

 

this is the Rad that George has used on each of his 3 conversions, a mk3 golf VR6 unit, note the provision for a thermoswitch, neither of the 406 or clio/laguna rads have that.

 

 

 

 

 

Personally all I would do is add a thermostatically controlled oil cooler.

Edited November 28, 2013 by welshpug

[Tom Fenton 1,524]

Sort the fan out and seal the rad to the car, I'd be 99% confident it would then be fine. That fan setup is bobar.

[allanallen 528 2 Cars]

It's not a fan, it's a propellor

[TooMany2cvs 65]

[allye 530 3 Cars]

Thank WP, that's helpful and you can see that the clio radiator is some what larger than a 406 item, which means it's much too wide unfortunately. This alone is confirmation enough that a 406 radiator will not be sufficient. Mile's has stated in the past the 406 radiator in the 406 barely does the job!

 

Advising to just stick 2, as large fans as possible, on there does really solve the problem (IMO) just sort of skirts around it. I have my answer that I've not really got to worry about over cooling it so I will find 50mm core item so it will never be a concern, or sitting in the back of my head on a hot summers day.

 

I have room to play with in term of height as that is already a custom bracket so making a new one would not be a problem, I also have depth to play with having more room in the bay than a 205.

[TooMany2cvs 65]

This alone is confirmation enough that a 406 radiator will not be sufficient.

I thought you said that the rad was just fine once you were moving freely - traffic and steep long hills apart - and once the temps had risen, they came down again quickly once you got under way again?

 

If so, that suggests to me that the rad's fine, and confirms the fans are the problem. If the rad wasn't up to the job, it wouldn't be shedding enough heat no matter how much airflow. Because it is once the air's flowing, then the rad surely HAS to be up to the job, and the problem MUST be the "artificial airflow".

[allye 530 3 Cars]

It's up to the job if you are moving quick enough. Still heats up even moving slowly. There is not a huge amount I can do about air flow to the front as I want it to remain looking unmodified.

 

The Clio V6's are also renown for running very warm (likely to their position though) What I'm basically trying to get at is I want to over do it a little. If I were to use the 406 radiator the fans would be clicking on and off non stop on anything other than a fast moving road.

[rallyeash 155]

how slow is slow? if its under 30 mph then its just there isn't enough forced air going into the rad.

 

I still maintain with a pair of 12" decent fans and the cooling system steamlined you'll be fine. Spend the £500 on a custom rad elsewhere.

 

even if you get a 60mm thick radiator if it isn't being cooled enough by airflow be that by a fan or driving at sped then it'll still get hot.

[rallyeash 155]

also what are your oil temperatures like? this can have a knock on effect to the water temp. do they rise in traffic?

 

on track my engine oil sits 85-95 depending on outside air temp and my water is 65-75. On a standard 205 gti rad and a 235mm 13 row oil cooler. These figures are directly in front of me as its monitored by a Stack Dash

Edited November 29, 2013 by rallyeash

[stu8v 68 1 Cars]

Your setup is gash.

 

Sort the ducting, seal the rad so the air goes through it and not round it and it will be fine.

That fan is p!$$ my pants funny btw......

[allye 530 3 Cars]

Your setup is gash.

 

Sort the ducting, seal the rad so the air goes through it and not round it and it will be fine.

That fan is p!$$ my pants funny btw......

 

Is there a echo in here?

[allye 530 3 Cars]

Pretty much ash, on a warm day driving under/around 30 it would heat up. Oil temp gauge never worked but the oil pressure always stayed rock solid which indicates oil is ok.

 

The fact the Clio rad is so big is all the assurance I need!!

[camgti 56]

406s don't over heat over here either. So not sure about the comments that they barely keep them cool...

 

Get a rad that's thick, triple core, fills the front, 2 fans, laughing.

 

Cam

[allye 530 3 Cars]

406s don't over heat over here either. So not sure about the comments that they barely keep them cool...

 

Get a rad that's thick, triple core, fills the front, 2 fans, laughing.

 

Cam

 

Thats it! This is the plan.

[Miles 331 1 Cars]

406 V6's don;t like track work full stop, All I could manage in mine was 1/2 lap at the ring and 6 to 7 minutes at Combe. that is with a couple of different rads too before the temps got too hot, that's D8 & D9 Versions, the latter just gets the heat exchanger fitted which makes things even worse.

OK for blasting along at 150+ MPH in Germany until the fuel tank runs dry with around 7 mpg

[RP1983 4]

I had a v'6 306 and like your 309 it would get hot quickly in traffic, my fan was wired to a switch and was a bit better setup than yours so would reduce the temps and keep them nice when sat still, even on a hot day like the day of pugfest I was queing with the car ticking over and no problems so I'd agree with everyone else your 'stood still' problem is just your fan setup.

 

The main problem I found with mine was giving it stick on B roads and situations for example going up Prescott hill where your putting it under full load but never really hitting enough speed to get plenty of air flowing over the rad. This would see the temp rise quickly so I would have to turn the fans on so I can see why you want to address the issue with a much more expensive engine and doing a conversion you want to be spot on otherwise as you've said, even with it all good the fan is going to be constantly on and off trying to control the temp.

 

It sounds like the Vr6 rad has done the job for Goliath as no way I could of done that in my 306 without the fan on constant so increasing the size definitely seems like the way forward.

[allye 530 3 Cars]

Advice from man with experience, cheers mate!

[welshpug 1,621]

Ahem...

[Biggles 65]

I'd be very surprised if a 640x414x32 rad wasn't sufficient to cool 260bhp if you ducted the air into it properly and had twin fans with shrouds sealed to it. I'm cooling 220bhp with a 560x200x50 rad with twin 8" fans. The fans stand off the back of the rad by 20mm with foam strip between shroud and rad so they can only draw through the rad and 20swg aluminium sheet ducts the air into the rad so all the air through the grill & bumper vent has to go through the rad. It doesn't overheat in traffic nor on the rally stage.

 

[allye 530 3 Cars]

You can't really compare a 4cylinder though. I'm no expert but its not as cut and dry as saying a certain volume will cool a certain BHP.

 

I found a after market radiator I will be using. Its from a S200, 50mm deep, dual core and over 50% more capacity than the 406 one. Not going to bugger about with this!

 

I like that metal surround and scoop at the bottom though.

Edited December 18, 2013 by allye

[Biggles 65]

Actually you can and it is but my apologies for trying to add some science to the debate. There's no significant difference in thermal efficiency of an I4 compared to a V6, ie the proportion of the fuel energy turned into useful work is the same. You want twice the power, you have to burn twice the fuel. To burn twice the fuel needs twice the air as air/fuel ratio is essentially fixed so exhaust heat also doubles. Hence twice the amount of heat needs to be rejected by the cooling system. But, as you've already made up your mind I'll take all my years experience as a development engineer for a major automotive OEM elsewhere whilst asking myself why i bother trying to help people on here.

[allanallen 528 2 Cars]

You have to remember this is a big heap of s*it v6, it turns most of the fuel it burns into heat and noise unlike a tuned 16v

 

Allye knew he wanted a bigger rad before he even started this thread?!

 

Bahh humbug!

[allye 530 3 Cars]

so exhaust heat also doubles.

 

Really?

 

Yes I had decided I wanted a bigger radiator, the original question was can it be too big and bit silly. If a evo radiator was 10mm narrower that would fit, and they are hoooogggee!