Is a double pass radiator worth it?
 

So, after my first competition I'm back on the drawing board to upgrade my cooling system.
https://my350z.com/forum/forced-indu...con-v-pro.html

Someone recommanded me to get a double pass radiator. I understand that a double pass radiator keeps coolant longer in a radiator, but seems like custom fabricating a double pass radiator for 350z is going to be a little more complicated than I initially thought.

One issue is that the inlet and outlet of our radiator is positioned opposite side (top right and bottom left) of one another, but the inlet and outlet of a double pass radiator needs to be located on the same side. This is a minor problem I suppose, since a longer rubber hose for the relocated inlet or outlet will solve this problem. Bigger issue is that in a stock radiator coolant flows from top to bottom, but seems like double pass radiator flows from side to side. Is there a reason why a double pass radiator flows from side to side? Can I create a double pass radiator that flows from top to bottom and bottom to top?

If a double pass radiator must flow from side to side, then this means that radiator reservors(?) need to be placed on the left and right side instead of top and bottom. This will totally alter the dimension of a radiator, so a new fan shroud need to be fabricated and etc...

I'm just trying to figure out if this is worth going through all the troubles, or should I just get the 56mm PWR radiator with the GTM's double 14" fans.
I know GTM has a thick @$$ racing radiator, but I don't want to loose my A/C and I don't want to fork out a grand for a radiator...
Thanks to Quaman I emailed the Howeracing, and I'm waiting for their response, but meanwhile I wanted to hear your opinions.

Lastly, I have a pathfinder cooling mod and I'm thinking about removing both thermostats. I understand that if I get rid of them my car might not warm up fast, but besides this are there other potential problems I should be concerned about?

Not sure about the VQ but in most cases if you remove the thermostat it will overheat. I had a MG midget long time ago and it loved having the thermostat removed. But a jeep I had with a 360 over heated.quick when I removed the thermostat

I will soon be tracking my Z and I am just looking to get a larger raditor core myself.And have been cheching out those GTM dual fans.

^ why would the car overheat from REMOVING the thermostatic bypass? I don't believe you will lose A/C with the thick radiator + fans + shroud (at least I didn't when Forged Performance installed the thick Koyo along with the shroud and upgraded SPAL fans that they sell).

I guess you didn't see this. ;) https://my350z.com/forum/product-ann...-radiator.html

BTW, I never overheat no matter how crazy I drive on the road, but road course/circuit driving is a completely different story.

You could try wiring your fans with relays so that both fans come on as soon as you start the car. That would be the cheapest solution to try and then go from there. I have my fans wired that way and it seems to work good for spirited street driving and drag racing.

Cars I have had in the past. Some over heat without a thermostat. Pull it out and see if it over heats. That is the only way to tell forsure. That's just from my past experiments.

I dont understand how you could overheat from removing a thermostat... your basically allowing coolant to flow through the radiator ALL the time instead of opening only when the coolant is at a certain temp.

IMO double pass radiator sounds like a lot of work... just get a koyo or something and call it good.

I will explain...

When the thermostat is close the coolant in the radiator will continue to cool. Even if the outside temp is 100 degrees it will still be cooler than what your engine temp is. When the temp outside is in the higher levels it will take more time for the coolant to cool while in the radiator. By removing your thermostat, you create a situation where the coolant never sits in the radiator long enough to reduce the tempature of the coolant. Essentially the coolant is constantly circulating and never cools down. You will most likely see a rise in the operating temp.:)

Exactly. Without the thermostat in the system the coolant travels to quickly through the radiator and engine, this prevents it from being able to transfer heat to the atmosphere and prevents the coolant from being able to absorb the heat from the engine. In many racing applications I have removed the thermostate and replaced it with a water restrictor. Either a piece of aluminum with a hole bored in it (usually 5/8") or a thermostat that has been cut apart leaving just the metal with a 5/8-3/4" hole in it.


As for a double pass radiator, I am a big fan of those. I come from a background in circle track racing, where it's on and off the throttle at over 8,000 RPMS. A lot of cycles and a lot of stress on the engine, temperature is a major issue. In my cars switching from a single pass radiator to a double pass would usually drop temps 15-20 degrees. This will obviously vary depending on the type of vehicles and I don't know if you would see those same types of results in your application but if you're having cooling problems a double pass would be the ultimate solution.

Oh I see, I didnt realize it needed some restriction. Thanks for explanation!

Great info! I wanted to hear from someone like you with racing backgrounds and experiences. You are right, spirited driving on the street DOESN'T come close to what the car experiences at track racing. I mean I never ever overheated on the street. This is why I can't just get the 56mm PWR radiator with GTM fans and call it good. I need to overdo it to the max to barely get by at the track... :icon22:

I also plan to fabricate an intercooler/radiator duct, so the air entering the front grill can't escape anywhere but through the intercooler and the radiator. My friend who owns a full out race car tells me just this duct alone made his water temp to drop like 50F!!

I wonder if anyone has made a duct such as the one you speak of? I would be interested in getting/making one.

Vented hoods also do a great job in cooling. I have noticed a 15 degree drop in oil temp by using just a vented hood. Water temp still stays the same though.

Amuse made it, but it's for NA application.

This is what I'm talking about:

http://img104.imageshack.us/i/resize...ecsl21xh1.jpg/

So it's the flow restriction caused by the thermostat that is actually the issue with its removal (because that restricted flow rate is optimal for efficient cooling). That makes sense - the flow rate should be maintained, one way or another (i.e. larger volume or dual pass core will be less affected by a higher flow rate).

OP - one consideration would be to run Evans NPG+ if the track allows it. Then you don't have to worry about water's low boiling point, vapor, elevated pressure, etc. (can run the engine coolant hotter, more safely). Sharif would track his sleeved Z with NPG+.

One of the other factors that many over look is turbulant flow in a radiator. The same theory as the thermostat mentioned above still applies to inside the actual radiator. Having extra heat sink capabilities, as in a larger radiator, means nothing if you can't move the water in a way that utilizies it.

Turbulant flow in a radiator is important to how much of the heat is absorbed into the radiator and how much stays with the water. This is in part why modern day coolant hoses and radiators are significantly smaller. Velocity is important in creating the proper flow pattern for maximum cooling efficiency just like in an exhaust manifold.

i'm sure you saw that custom double pass radiator in the marketplace right? Pretty crazy coincidence between this thread and that FS ad.

No I have not!! I better go look!!

I just checked it out. It even has an integrated oil heat exchanger.. Nice piece, but I'm gonna stick with other brand Quamen recommanded. A lot cheaper!

For sure! Custom radiators that average between $250 and $400 is the way to go!!