Radiator question.. Core thickness/air flow

[TurboRA28]

Hello, hows you all going? Got a quick radiator question I hope..

I've fitted the RA28 with a Hyundai Excel radiator. They are an alloy core, plastic tank job. Much more surface area than the original Celica one. Seem to do a great job of cooling the AE86 down that i've also got one in.

Anyhows.. Im finding in the RA28 under boost/load or in traffic it struggles to cool it. The rest of the cooling system is up to scratch, new water pump etc.

Now the hyundai radiator I have is from the early boxy hyundais and as i wasn't sure if it do the job or not i just purchased a secondhand one. The fins are a bit soft.

As its overheating i realise im going to have to either try a new core in the hyundai radiator, or swap out to something else completely.

I was looking at the newer hyundai radiators from the roundish hyundais, mid 95 models. There radiators are actually thinner core than the older model ones. Both are alloy, same mounting points.

Am I better off with the early radiator with the thicker core, or the newer model one with the thinner core? I thought thicker would be better.. But if the newer models are coming with thinner radiators maybe thats not the case.

Thanks
Joel

[Bananaman]

Most people seem to use the X3 radiator, which runs from 94-2000 (radiator should be the same right through as far as i know). Had a look at YelloRolla's setup yesterday which uses this, and he doesn't seem to have had any dramas with it. I'm intending on using the same one myself.

That said, i can't comment on how they compare to the early ones, but my thinking is that if it works for someone else, it should ideally work for me

[TurboRA28]

Yeah YelloRolla has the later model one.. Just cant stop thinking the earlier thicker one would be better.. But maybe not hey..

[roadsailing]

thicker isn't always better, you gain heat dissapation area, but the core becomes more restrictive for air to flow through.

at a guess, thicker core would be better when you don't have much natural airflow.

bear in mind that a car company doesn't change things to be "better" unless they are causing them problems, most changes are made to lower cost. its possible the earlier radiator had loads of excess capacity and they decided they didnt need it.

then again, it could really work better

[oldcorollas]

agreed.. more likely to be cost push than performance push..

an addition to the above points, if your thermostat is the flow restrictor in the system, a thicker core gives longer residence time in the cooling tubes, which may offset the inefficiency of the thicker core (air flow resistance, heated air on second row etc).. but then maybe the inefficiency is too large to ignore, or more water is going thru the rear core? (maybe nto likely)

if your core is second hand, how sure are you that it is not blocked?

if it's in traffic, are the fans up to the job of pulling air thru? are you directing all air into radiator (not allowing it to leak into engine bay any other way?) can the air get out of engine bay? etc?

[phrostbyte]

I recently upgraded to a '95 Excel aluminum core radiator on tha 4AGE recently too. I've found it does a great job of cooling, not really a noticeably difference between the stock KE70 radiator and the new one, but it puts the mind at ease a bit knowing that you have that extra cooling for a hot day.

Keep in mind that any engine under boost or load is going to heat up more than normal. Coolants are designed to handle between 120 and 140 degrees before boiling, and most toyota engines are designed to operate at around 85 degrees (89 i think?). Probably a good idea to get an aftermarket temperature gauge so you can get an accurate numbered reading and see exactly what temperature its actually reaching.

My 4AGE always used to boil the water after a good thrashing (was using water, not coolant, at that stage). And that was only at half-way up the temp gauge. Water's boiling point is 100 degrees celcius, so I'd say that about 105 or so degrees is the exact centre of most stock temperature gauges, with a quarter of the way being the designed operating temperature, ie. 89 degrees.

Anyway, been up all night and am rambling on.

Kev.

[TurboRA28]

Thanks all for the replys.. It could well be just a dirty radiator. I plan on getting a new core, or finding one with a good core and getting it flushed etc. But just wanted to make sure the radiator I pick is up to the task.

I'm keen to stick with the hyundai one as i've got the mounts all setup for it now.

Traffic isn't such the problem, it does get up on a 35 degree day to say 95 degrees or so. Which is a bit too hot, but it doesn't seem to get any worse. We really noticed it most of all on the dyno trying to tune under boost/load. It just couldn't keep the temps down.

On the street its not always going to be under boost/load but it will see a lot of track days and dont want to be going down to Wakefield and find it can only handle a couple of laps.

I'd like to talk about air flow etc..

The hyundai radiator is bigger than the opening at the front of the car. It's spaced back an inch or so. So air could get around it. I should be sealing this in yeah?

Also, i dont have the shield that normally sits between radiator and xmember at the bottom of it. I heard rumors this is important for cooling?

Cheers
Joel

[45aken]

how much did you pay for the new 95 radiator with fans and the switch?
thinkin this might be a good idea for me too.

[TurboRA28]

I haven't purchased new one yet.. Just trying to work out first if this radiator will actually do the job..

[45aken]

no worries mate. good luck with it.

[Bananaman]

The hyundai radiator is bigger than the opening at the front of the car. It's spaced back an inch or so. So air could get around it. I should be sealing this in yeah?

Also, i dont have the shield that normally sits between radiator and xmember at the bottom of it. I heard rumors this is important for cooling?

Cheers
Joel

As much as an inch isn't as much as i was talking, to use my old rx7 as an example:



The radiator in an rx7 is set back a fair way from the very front of the bay (given it slopes down of course), and is ducted from the front to the radiator. One day i removed the top panel you can see between the top of the radiator and the front of the car, when i was test fitting an aircon condensor (to make sure i didn't overheat). I subsequently started overheating, from a rock solid 83-85 deg to going over 100, with the removal of that ducting being the cause. In the same sense, when using an engine fan (well, any i suppose), its much more effective with a shroud.

So yes, i'd say that making sure that the air can't go around the radiator is important, air is going to take the easy path before going through your radiator

[TurboRA28]

Very very interesting thankyou
What materials do you think would work well? I was thinking foam on the sides, and maybe some thin sheet metal at the top and bottom?

[oldcorollas]

yah, DEFINITELY seal the bastard in as bananaman said...

for my shitty rolla i noticed big difference too...

stop air getting around sides and top of radiator and if possible, extend the shielding at the top to the front of the bonnet or thereabouts (so the air doesn't go between the radiator support and the bonnet)

what you want is to effectively create a "dam" where the only spillway is the radiator core... so air hits the front of the car, and either has to go above bonnet, below car, or thru radiator... so the radiator nees to be effictively sealed to the very front of the car with no gaps..

a good material to use is the plastic sheet used or real estate signs.... cheap, easy to work with, shouldn't melt.. much.... altough if you want to use metal sheet, why not... and foam at sides will also work... when i was testing, i used camping mat foam and ice-cream container lids with lashings of duct tape... duct tape doesn't like radiator heat so much tho...

it may not hekp on dyno, but on dyno you have buggerall air flow, even with big fan... ont he track, the extra cooling from movign fast will most likely keep it cool enough... since radiator fans are usually surpased by air speed from moving at around... 40k's? (in my experience)

[TurboRA28]

Thats my project for this week then

Does the splash guard that normally sits under the radiator spanning from front of car to xmember have much to do with all this? I haven't had one in for years, but figuring maybe its a good idea.

[oldcorollas]

in some cars it makes a massive difference to airflow thru the engine bay ( i can't remember the good example tho.... maybe a commonwhore?)

afair by having it there... and altering the airflow under car, you can create a kind of venturi effect of sorts, and suck air out the bottom at the rear of the engine bay, aiding in pulling air thru radiator.... and also my help divert air to the sides of the engine bay a little as well... every bit of air not going under car reduces the pressure = higher pressure differential between under car and front of car, ie across radiator...

what you could do (as a test) is to seal up around radiator first, then get good temp probe and put somewhere specific (ie like K-type thermocouple?) in cooling system (or even just measure resistance of the stock temp sensor perhaps.. then you can later correlate with temp using a pot on the stove), go for a drive on highway, stay at high speed for... a few minutes.. enough to stabilie temps....

then put on undertray, and repeat.. same day, near same time so air temp is not so different.. and se if it makes any difference..... would at least be interesting to see results