Project Rear Mounted Radiators

[pkovgolf]

Could someone please post pictures and details on plumbing the dual radiators on a fiero?
You can see details at my build diary - I have the original rear on the car so there is not a ton of room for the 1.5" or bigger tubing
Thank you!!

[tonypaul]

So, from what I read, you had dual radiators but one got a leak so you took it out and ran the car with just one radiator instead? You wonder why the car ran hotter running on just one radiator instead of 2?
I think this discussion is about Dual pass radiators versus single pass radiators, not dual radiators versus single radiators lol.

You gotta read the entire post- especially the part where I said "it makes sense" why it was running hotter....
 Im sorry I should have only posted something only if it was pertaining exactly to the subject... my bad~ 

[tonypaul]

When I took my Griffin radiator in to the shop to get it fixed the guy commented on how small of radiator it was. I told him I was running dual radiators, he immediately ask me if I had them in a series or parallel setup. I told him I had them in a series and asked if that was best way to run them. He said most manufacturers that uses 2 or more radiators that he has seen runs them in parallel but he said he has seen problems with them run that way.

His explaination was that one of the radiators could get a air bubble/pocket or debris one and not let coolant run thru both at the same rate of flow as the other and cause the circulation not to be evenly distributed.  He also said he had seen them in a dual setup where one radiator cools each side of the engine in some industrial machines. So in theory if one radiator was blocked the head on that side would be running hotter than the other and cause all kinds of problems.

But thats all in theory and would depend on the setup. He suggested that I keep them in a series if its working for me. I would think that what ever setup someone wants to use and it works- more power to them.....

[BigPines]

I may have muddied the water with my post including comments on single vs. dual radiators. However, I think everyone knows what the discussion is about by now.

For what it is worth, I thought tonypaul's comments were very interesting. Kinda nice to know you could limp along with one radiator in an emergency. Nice side-effect of a dual radiator set-up. You automatically get a hot spare (pardon the pun).

As I mentioned before, the testing posted in the link above is very helpful. I would be interested to see additional testing of series vs. parallel as well as push/pull fan configurations. Has anyone done this or is anyone interested in doing it? I may have to do my own testing someday. Honestly, why not do everything possible to lower the temps?

[670SV]

So, from what I read, you had dual radiators but one got a leak so you took it out and ran the car with just one radiator instead? You wonder why the car ran hotter running on just one radiator instead of 2?
I think this discussion is about Dual pass radiators versus single pass radiators, not dual radiators versus single radiators lol.

[tonypaul]

Not sure if this is revelant or not but- Last October one of my dual Griffen radiators got a small pin hole leak. I took it out and dropped it off to get it fixed. Wanting to drive the car I just looped the coolant lines together and only used the one radiator. My engine temps went from 160-170 degrees (160 thermostat) to 200 to 210 degrees on my LS4 using only 1 of the spal fans. This was in cool fall air temps of 60-65 degrees, I bet had I tried it in the 100+ degree summer months it would have over heated...

But these are pretty small radiators on a v8 so it makes sense that the temps went up. Got the other radaitor fixed and put back in 3 days later and the engine temps went back down to normal levels. Recently the summer temps reached 95-100+ degrees and my car temps started to go up around 200-210 degrees in heavy traffic.

 After scratching my head for awhile trying to figure out way my engine was running hotter than normal I found out that the factory LS4 aluminum heater core lines that ran along the exhaust manifold and exhaust cross over was getting to hot. Fixed that issue and now the engine temps are back down again....

[670SV]

The working temperature of the radiator is anywhere between freezing and 260 degrees. Lets say the engine is running at about 200 degrees F. as the coolant runs through the single pass radiator, it cools to 180 degrees F and returns to the engine (this is just a hypothetical example, temperatures vary). That is a 10% drop in temperature, which is about normal.
Now, as stated, "dual pass radiators cool about 5% better than single pass radiators". So, if a single pass cools 20 degrees a dual pass will cool an additional 5% (of that 20 degrees), so 5% of 20 = 1 degree. So the single pass cools 20 degrees, and the dual pass cools 21 degrees.  As stated, dual pass radiators do cool better than single pass, but only 5% better than the amount of cooling expected from a single pass. It's not opinion, its fact.
As also stated before, Aluminum tubing (metal) also accounts for much heat dissipation in the total system, and the more tubing the better. Aluminum sheds heat much quicker than steel or copper, that's why heat sinks made from Aluminum are used on electrical components.
Location of the radiators has nothing to do with cooling if the radiators receive the same amount of airflow regardless of their position. The Radiators in the back of my build receive far more airflow than the front single radiator ever did, due to the design of the front of the car and the ride height.

The numbers and temperatures are just an example, not chosen for any reason other than for sake of example.
I think every manufacturer fudges the numbers somewhat, and there are other factors that play into the total cooling effect as well.
I went on Nutrisystem 3 years ago and GAINED 6 pounds dammit! They lied to lol!
I think the whole point being made was to not buy into all the hoopla and claims. The price of a dual pass radiator compared to a single pass is not justified (in my opinion) for the amount of cooling achieved (dollar vs. degree).
I bought a time machine off ebay that doesn't work either, maybe I just have it hooked up wrong  I did enjoy your sarcasm about the subject though, very refreshing!

[BigPines]

Now that's what I am talking about jdinner! Nice to have some science in this argument. This was a very interesting experiment. I wonder if anyone has done any experiments on push-pull fan configurations?

I did a quick Google search and didn't turn up anything really useful.

[jdinner]

The working temperature of the radiator is anywhere between freezing and 260 degrees. Lets say the engine is running at about 200 degrees F. as the coolant runs through the single pass radiator, it cools to 180 degrees F and returns to the engine (this is just a hypothetical example, temperatures vary). That is a 10% drop in temperature, which is about normal.
Now, as stated, "dual pass radiators cool about 5% better than single pass radiators". So, if a single pass cools 20 degrees a dual pass will cool an additional 5% (of that 20 degrees), so 5% of 20 = 1 degree. So the single pass cools 20 degrees, and the dual pass cools 21 degrees.  As stated, dual pass radiators do cool better than single pass, but only 5% better than the amount of cooling expected from a single pass. It's not opinion, its fact.
As also stated before, Aluminum tubing (metal) also accounts for much heat dissipation in the total system, and the more tubing the better. Aluminum sheds heat much quicker than steel or copper, that's why heat sinks made from Aluminum are used on electrical components.
Location of the radiators has nothing to do with cooling if the radiators receive the same amount of airflow regardless of their position. The Radiators in the back of my build receive far more airflow than the front single radiator ever did, due to the design of the front of the car and the ride height.

First off, welcome to the forum 670SV!
Not to beat a dead horse here but....
I was just wondering why you would choose the radiator temperature numbers of 180*F to 200*F to base your 'fact' on? Can you provide data for this?
I was just curious why the 5% fact would be based on such a weird number combination when a lot of LS engines run at about 212*F and some euro engines run at a 230*F.
http://www.flyinmiata.com/tech/rads.php
Is it possible that the people that put this study together fudged the numbers to show that the dual pass radiator had a better cooling difference of 12*C (21.6*F)?
Do they not know the facts? This is not supposed to happen, it should only be 1.0*F, right? 

[BigPines]

Look, I don't pretend to be an expert on this particular discussion. However, it makes sense that two radiators are better than one. How much better? We can debate that forever. The only way to tell for sure is do some scientific tests and post the results. I doubt anyone will take the time to do that but I personally would find it very interesting. It also makes sense that two fans in a push-pull configuration will do a better job than one. It is a simple concept - two fans simply move more air. I have been doing the same thing on my custom built (water cooled) PC for years. I can tell you two fans make a difference. How much? Again, if we really want to know, we will need to take the time to do the experiment and analyze the results. I'd love to see this done.

Mike

[plans4sale]

The working temperature of the radiator is anywhere between freezing and 260 degrees. Lets say the engine is running at about 200 degrees F. as the coolant runs through the single pass radiator, it cools to 180 degrees F and returns to the engine (this is just a hypothetical example, temperatures vary). That is a 10% drop in temperature, which is about normal.
Now, as stated, "dual pass radiators cool about 5% better than single pass radiators". So, if a single pass cools 20 degrees a dual pass will cool an additional 5% (of that 20 degrees), so 5% of 20 = 1 degree. So the single pass cools 20 degrees, and the dual pass cools 21 degrees.  As stated, dual pass radiators do cool better than single pass, but only 5% better than the amount of cooling expected from a single pass. It's not opinion, its fact.
As also stated before, Aluminum tubing (metal) also accounts for much heat dissipation in the total system, and the more tubing the better. Aluminum sheds heat much quicker than steel or copper, that's why heat sinks made from Aluminum are used on electrical components.
Location of the radiators has nothing to do with cooling if the radiators receive the same amount of airflow regardless of their position. The Radiators in the back of my build receive far more airflow than the front single radiator ever did, due to the design of the front of the car and the ride height.

Have you ever checked the tests of companies making dual-pass radiators? I checked these yesterday. Aside from the usual fake numbers most of them use for advertising purposes, there are thermal tests showing at least 5-10 degrees F drop of the temperature compared to normal single-pass radiator.

 Also, the example you gave may not work on your car if you didn't provided proper air flow in the front end to extract the hot air behind the radiator (and this must be at least the same size as the air intake, plus proper way to redirect it to outside). Blocking the hot air behind the radiator is the easiest way to make the latter ineffective, thus overheat the engine. Also, a radiator inside the engine compartment (like some builders install the radiator in front of the rear air ducts below the tail lights) and taking air from inside is all wrong, because that means the radiator is receiving already 50-80 degrees C hot air before the fan which is not as effective like the cold air coming in a front air intake radiator configuration.

 As for the tubing used to additionally cool the hot water, with 2 radiators at the front you have at least 3 meters (118") length for each of the two tubes of each radiator that are making the circuit between the endine and the radiator. Depending of whether you connect both radiators to use the same circuit in (1) a engine>radiator>radiator arrangement, or (2) engine>both radiators arrangement, you get either 6 (236") or 12 (472") meters long tubing respectively. I have never heard about anyone who is installing his/her radiators at the back with that much length of tubing. And, again, even if somehow you manage to put 12 meters of tubing inside the engine compartment, you can not expect to have the same positive effect of losing heat from the tubes, because the heat inside the engine compartment will act against the hot water in the tubes. This is double negative effect where each of these hot things will impede the cooling of the other one.

[670SV]

The working temperature of the radiator is anywhere between freezing and 260 degrees. Lets say the engine is running at about 200 degrees F. as the coolant runs through the single pass radiator, it cools to 180 degrees F and returns to the engine (this is just a hypothetical example, temperatures vary). That is a 10% drop in temperature, which is about normal.
Now, as stated, "dual pass radiators cool about 5% better than single pass radiators". So, if a single pass cools 20 degrees a dual pass will cool an additional 5% (of that 20 degrees), so 5% of 20 = 1 degree. So the single pass cools 20 degrees, and the dual pass cools 21 degrees.  As stated, dual pass radiators do cool better than single pass, but only 5% better than the amount of cooling expected from a single pass. It's not opinion, its fact.
As also stated before, Aluminum tubing (metal) also accounts for much heat dissipation in the total system, and the more tubing the better. Aluminum sheds heat much quicker than steel or copper, that's why heat sinks made from Aluminum are used on electrical components.
Location of the radiators has nothing to do with cooling if the radiators receive the same amount of airflow regardless of their position. The Radiators in the back of my build receive far more airflow than the front single radiator ever did, due to the design of the front of the car and the ride height.

[plans4sale]

5% better only amounts to 1 or 2 degrees.

You claim that the radiator's working temperature is just about 20-40 degrees? What are those degrees? F or C?
 I'm asking, because last time I serviced a radiator the temperature was nearly 100 degrees C (212 degrees F) because the water inside was just starting to vapour. 5% improvement in cooling means 5 degrees C (10.6 degrees F) lower temperature, which is a lot.

 By the way, best cooling is made with front mounted radiators and metal tubes, because (1) taking air stream directly from the front air intakes will provide the most cool air possible, and (2) the water will go through longer distance where the metal tubes will release a few more degrees in both directions.

[Murci-Me]

5% better only amounts to 1 or 2 degrees.

[jdinner]

How about 5% better. I'll take 5% better than 5% worse any day of the week. If your car is running a stock 2.8 you may never see the importance of a properly functioning cooling system. I battled with running hot issues for over a year on my V12. Now it is solved and I documented the entire process.
Our cars can not be textbook due to the way air can flow. The lower rocker scoops can redirect or cause turbulence to radiator air intake prior to hitting the rad, huge vacuum is created behind our cars when they are at speed and the engine bay has virtually no air movement.
Dual Pass = Lamborghini