Radiators? 1 core 2 core, cross flow, etc...

[fireslave]

Hey guys, im looking to get a new radiator for my project car, a vq35HR (350z engine) powered 240sx.

the 350z radiator wont fit, and even if it would, i might need some additional cooling later on if i decide to turbo it.

I want to buy a custom radiator, but i have no idea what to get. 1 core or 2 core, crossflow or downflow.

i assume more cores is better, but by how much? is 1 thick core as good as 2 thin cores?

same with crossflow.. i heard its better, but by how much?


if anyone has any advice, or a link to a good article, thatd be awesome. thanks!

 

[Bribyk]

Adding cores (and even thickness for that matter) has a diminishing return effect as each core added behind the first sees warmer air from the core ahead of it. Fit the biggest frontal area you can and then start adding cores as required. Talk to a manufacturer for their sizing recommendations and input. If you're drifting you'll want even more rad because the airflow direction isn't head on with the car.

 

[evelrod]

We have our racing radiators fabbed by Ron Davis in Arizona. I make up the sketches and they build it. If you know the hp output and the intended use, it should not be a problem to come up with something you will be ok with.

Check out your competition, it may save you some time and a couple bucks.


Rod

 

[tbuelna]

fireslave,

Most automotive coolant heat exchangers are single pass cross-flow cores. Since you desire to achieve a greater heat rejection rate in a core that must fit an existing engine bay, your only real option is to use a core with greater thickness. Adding thickness (ie. 4 rows of tubes vs. 3 rows) is fairly effective with regards to heat transfer efficiency, and will not increase the inlet/outlet duct cross sections needed for the installation.

Actually, thicker tube/fin liquid-to-air cores tend to perform quite well since the longer airflow path gives a greater temperature rise in the airflow, thus requiring a lower mass flow to reject a given heat load.

High performance aftermarket cores also generally perform better than an OEM core of equal size, since the aftermarket guys can use things like thinner wall tubes, denser fin spacing, flow passage turbulators, fin louvers, etc., that an OEM cannot afford to use.

Good luck.
Terry

 

[Deltona]

Double pass rads are the most efficient.

 

[izzmus]

I would focus on airflow management - getting the air out of the engine bay. There's only incremental gains you can make with respect to getting more radiator in the nose of that particular car, but there will be much more to be had by actually moving air through it.

I'd imagine that a big four cam V6 would make the airflow situation even worse than normal.

 

[patprimmer]

Improving airflow out of the engine bay was a fix for V12 Jaguars here. We simply raised the rear end slightly and reworked the floor at the bottom of the firewall and back a little to improve flow under the car and relocated any easily movable obvious obstructions between the engine and the inner guards.

Tubular headers and big collectors were counter productive re heat, but we needed them for power.

A big oil cooler located at the rear out of the main airstream with a fan on it also helped.

Regards
Pat
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[marcusaurailius]

I totally agree with Izmus and Pat,
getting the air out, is as good as ,or better than a rad change

the faster you go, the more air is forced into the bonnet/hood area, thus raising the front of the car of the ground

also you need a good tight fitting rad shroud, so that any air that goes thru the grill, will ..go thru the rad ..

and not around it

regards Marcus

One does nae have to know how some thing works, to know that it is nae working right

http://s545.photobucket.com/albums/hh369/marcusaurailius/

 

[patprimmer]

Oh

While raising the gap between the floor and the ground and increasing opening at the rear of the car we made sure the front chin spoiler was as low as practicable to reduce air going under the car that had not already gone through the radiator.

Regards
Pat
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[isaac338]

evelrod,

Do you have any links which might go over the calculations required to figure out the cooling load of a motor and the size of the rad?

Thanks a lot.

 

[evelrod]

No, sorry. I just gave the folks over at Ron Davis the specs and let them do the work. I have noticed that they tend to be on the conservative side.

I do have a magazine article somewhere that Smokey wrote. It details all the necessary calcs.
I'll see if I can find it.

Rod

 

[fireslave]

thanks for all the helpful posts.


i ordered a dual core aluminum radiator from griffin radiator.

next project is to build a custom aluminum fan shroud... plan is to re-use the 350z fans.



I was thinking of adding a vented hood to get rid of some of the excess heat... something like this:

http://images.extremedimensions.com/ExtImages/89_240sxd1hood.jpg

do you goys think it would be a good idea to duct all the air coming through the radiator out through the hood vent to take advantage of the low pressure zone, or would it be better to just let the air flow as it pleases?



Also, i might add forced induction at some point, and im not sure what would be a better choice, a front mount intercooler or a v-mount system... any advice?

 

[evelrod]

I did a similar modification to a Pantera a few yeas back. They were notorious for overheat in our climate and the opening in the bonnet worked like a charm. I will say, the Pantera mod looked a bit more journeyman than the photo you post.

Rod

 

[patprimmer]

I would let it decide for itself what is the easiest way out. Fluids are VERY good at that.

The vents should work. I was tempted to say look good meaning good to work, then had a look and decided to be non ambiguous

Regards
Pat
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