COOLANT TECH : Single, Dual, Triple pass

[Bebop]

Sooooo, I'm planning to upgrade my cooling package in the buggy and will go to the biggest rad I can fit, which will be a 28x19 3 row unit.

Should I go single or dual pass ?

Dual pass makes plumbing easier for me but that's marginal. I have a LS based engine, meaning that I can find water pumps with either driver or pass side outlets no problem, it's just another expense.

Factory rad is single pass.

I plan to buy a DIY radiator kit and weld my own inlet/outlets/cap. I could make it single or dual pass. Dual pass is more work and potentially more problems like : welding closer to the core (harder), divider not sealing 100% etc...

I am reading conflicting info about single vs dual passes (and triple passes for that matter).

I've heard that single pass doesn't distribute eventy the temperature and dual pass increases pump load..

These guys seem to know what they're talking about and don't recommend a dual pass it seems :

https://www.stewartcomponents.com/index.php?route=information/information&information_id=13

Double pass radiators require 16x more pressure to flow the same volume of coolant through them, as compared to a single pass radiator. Triple pass radiators require 64x more pressure to maintain the same volume. Automotive water pumps are a centrifugal design, not positive displacement, so with a double pass radiator, the pressure is doubled and flow is reduced by approximately 33%. Modern radiator designs, using wide/thin cross sections tubes, seldom benefit from multiple pass configurations. The decrease in flow caused by multiple passes offsets any benefits of a high-flow water pump.

I also read somewhere (forum sooo, take that with a grain of salt) that a certain style of rad is better at low RPM vs the other one being better for high RPM.


In both cases, there will be PLENTY of fan for low speed airflow.

Thanks for your help.

PS : Pagging HYDRODYNAMIC again

 

[Domer]

This is a shitty topic that I learned the hard way with, You can google search for references. But for every pass you add to a radiator (Not cores) you lose pressure by 16x. I am currently running a triple pass radiator with my small 4.7 V8 and it wont keep the engine cool at sustained higher rpms, as my water pump is insufficient. They require a substantial electric water pump to work. The Dual pass seem to work fine with LS engines as they were some what designed for that purpose.

 

[Satan's_Minion]

You will never get the true specifications of the components and a real requirement for heat rejection for your engine to do the maths...

Water pump flow curve map vs rpm
Piping head loss
Radiator flow/restriction curves (air/fluid sides)
Radiator effectiveness map
Fan flow curve
Air side installation restrictions (shroud/grill/etc)
Air inlet temperatures
Engine heat rejection map as function of rpm vs load

This is what you need to a simple 1D simulation, where you still have to decide what is the dynamic cycle you want to it to cool in.


Single vs dual pass 16x pressure loss blanket statement sounds pretty wrong.

The increase will be VERY dependent on the actual specs of the cores being used. Think about it this way you will have to double the flow through the core for twice the length. So the restriction curve of the core will have a big effect.

There are several large inflection points within each of the components where their performance can change quickly. If you end up with something operating outside of its designed zone your system of good parts may severely underperform.


One interesting thing to think about is a dual pass radiator does not have uniform expansion of the tubes as half of the tubes are at a different temperature profile, 1st vs 2nd pass. This is a big negative for long term longevity, but we do not use our vehicles like a normal car, might still last 10+ years.

 

[Bebop]

You will never get the true specifications of the components and a real requirement for heat rejection for your engine to do the maths...

Water pump flow curve map vs rpm
Piping head loss
Radiator flow/restriction curves (air/fluid sides)
Radiator effectiveness map
Fan flow curve
Air side installation restrictions (shroud/grill/etc)
Air inlet temperatures
Engine heat rejection map as function of rpm vs load

This is what you need to a simple 1D simulation, where you still have to decide what is the dynamic cycle you want to it to cool in.

Welp, not happening

Single vs dual pass 16x pressure loss blanket statement sounds pretty wrong.

The increase will be VERY dependent on the actual specs of the cores being used. Think about it this way you will have to double the flow through the core for twice the length. So the restriction curve of the core will have a big effect.

There are several large inflection points within each of the components where their performance can change quickly. If you end up with something operating outside of its designed zone your system of good parts may severely underperform.

Makes sense.

One interesting thing to think about is a dual pass radiator does not have uniform expansion of the tubes as half of the tubes are at a different temperature profile, 1st vs 2nd pass. This is a big negative for long term longevity, but we do not use our vehicles like a normal car, might still last 10+ years.

Makes total sense too and I would have never thought about that.

Thanks for the tech !

 

[HYDRODYNAMIC]

Older engines with water pumps designed for single pass need a single pass to keep pressure and flow in spec otherwise flow will drop and overall performance will drop.
LS engines can run a dual pass without issue. That has been confirmed by many radiator manufacturers.
Make sure the research you are doing is specific for the engine at hand. A SBC hot rod site is going to have non applicable info VS a LS rock crawling site.
I ran dual pass on my old buggy 6.0 and 19x31 Griffin and dual 12” Spal deep curve blade with no issues in 100* plus weather.
A taller core and deeper core is also going to flow easier than a thin and short core. So a single pass motor and pump could run a dual pass radiator if the core flow was double the size.

 

[arse_sidewards]

What are you running now and why do you think you need to upgrade? I'd bet money there's one or two things in the system that are simply not sized or installed in a way that matches the rest of the system.

These threads always wind up full of the same idiots who think you need to run 1/0 welding cable for a 60A 1-wire alt on a tractor.

The cooling requirements of anything that isn't being floored a large % of the time it's running (shibox going from light to light, pickup hauling something, racing) aren't really that much.

For the duty cycles that the overwhelming majority of the "gets to the trail on a trailer" vehicles run a junkyard radiator from something with about the same power level is sufficient.

Most "cooling system problems" are actually "22RE needs its annual head gasket" or "20yo half clogged radiator is not sufficient for an LS swap that triples the vehicle's horsepower" problems exacerbated by morons who don't understand how fan shrouds work and why they're important or bigger morons who think an electric fan is an upgrade over a mechanical fan driven off the pump.

 

[Bebop]

While I agree with you on the non-optimized systems, my current one does great. It's a 28x15 griffin dual pass rad with (2) 12" brushed spal fans that are PWM modulated through a C6 module. Cools my engine (5.3 vortec) just fine.

The problem is the blower that is going to top this engine in the near future. I'll be doubling the output of my engine, I plan to use all of it and I like to have some extra room in case I have to tow a friend back to camp and/or ride in summer temps (100+). Overheating and sitting on the side of the trail because my cooling system is under performing doesn't sound like a great idea. While running my fans at 30% all the time because the cooling system is "too efficient" doesn't seem like that bad of a deal.

I'm also limited in terms of dimensions because of the chassis and the rad location (front radiator) so in order to be able to achieve my goals I'll have to maximize the efficiency of my setup.

But with what I learned from brushing on the topic, I cannot really make a big mistake from going either single or dual pass in my application. I'll make the call when I have the radiator in my hands and I'll go from there.

Thanks guys !

 

[HYDRODYNAMIC]

What are you running now and why do you think you need to upgrade? I'd bet money there's one or two things in the system that are simply not sized or installed in a way that matches the rest of the system.

These threads always wind up full of the same idiots who think you need to run 1/0 welding cable for a 60A 1-wire alt on a tractor.

The cooling requirements of anything that isn't being floored a large % of the time it's running (shibox going from light to light, pickup hauling something, racing) aren't really that much.

For the duty cycles that the overwhelming majority of the "gets to the trail on a trailer" vehicles run a junkyard radiator from something with about the same power level is sufficient.

Most "cooling system problems" are actually "22RE needs its annual head gasket" or "20yo half clogged radiator is not sufficient for an LS swap that triples the vehicle's horsepower" problems exacerbated by morons who don't understand how fan shrouds work and why they're important or bigger morons who think an electric fan is an upgrade over a mechanical fan driven off the pump.

Don't disregard what works in one climate works for all climates. I can only assume that you wheel in Worcester. If so, your hottest month is 20F cooler than it is at Hammers. Your coldest month is 22F cooler than the coldest month at Hammers.
Entering Temperature Difference E.T.D. = Entering fluid temp - Entering ambient air temp
220F engine coolant - 80F ambient air = 140ETD
220F engine coolant - 100F ambient air = 120ETD
120F/140F= 86% so operating in different climates can de-rate a cooling system by 14%, I'm sure the swing is more depending on what states and counties everyone lives in.

You mention to "run a junkyard radiator from something with about the same power level". The LS truck motor which is probably the most common buggy motor in stock form which is using dual electric fans pulling 52A on a 17.5" x 34" core from the factory. Most people can not fit that large of a cooling system in a buggy so they are downsizing the systems to fit and are laying them down or putting them in the rear where they do not get the same cool airflow as right up front in the grille going down the road at speed.
Now when someone adds some power to one of those motors and is using it heavily in a hot climate it is right on the border line of overheating.

What works for one does not work all, that is for sure.

 

[Provience]

While I agree with you on the non-optimized systems, my current one does great. It's a 28x15 griffin dual pass rad with (2) 12" brushed spal fans that are PWM modulated through a C6 module. Cools my engine (5.3 vortec) just fine.

The problem is the blower that is going to top this engine in the near future. I'll be doubling the output of my engine, I plan to use all of it and I like to have some extra room in case I have to tow a friend back to camp and/or ride in summer temps (100+). Overheating and sitting on the side of the trail because my cooling system is under performing doesn't sound like a great idea. While running my fans at 30% all the time because the cooling system is "too efficient" doesn't seem like that bad of a deal.

I'm also limited in terms of dimensions because of the chassis and the rad location (front radiator) so in order to be able to achieve my goals I'll have to maximize the efficiency of my setup.

But with what I learned from brushing on the topic, I cannot really make a big mistake from going either single or dual pass in my application. I'll make the call when I have the radiator in my hands and I'll go from there.

Thanks guys !

if it works good as is and you aren't currently running your fans maxed out, i'd give what you've a clean and a whirl and see if it is also fine for adding the blower. odds are good.

electric fans and electric pumps are great if you are having low speed/high load cooling issues and cannot fit more capacity

 

[Bebop]

I have a big alternator so that’s not a worry but as far as my experience goes, electric water pumps (the ones that bolt directly in place of the stock ones) do not hold up to an Offroad environment.
Remote pumps work great but I don’t have room unfortunately.

I may supercharge it and keep my current system just to see what happens but I’d like to plan for the worst.

 

[TrailTamer]

I also read somewhere (forum sooo, take that with a grain of salt) that a certain style of rad is better at low RPM vs the other one being better for high RPM.

In both cases, there will be PLENTY of fan for low speed airflow.

I'll like to drop in my $0.02 about that.

a heat exchanger, or radiator in our case, the higher flow rate the more heat it will remove from the coolant, so I don't think claiming that some radiator is better at higher or lower rpm is correct.

Obviously, for us off roaders our engine mostly see idle to mid-rpm range at most with low ground speed. So, cooling fan is critical.

 

[CarterKraft]

I think I found the radiator tech thread...

All my reading says dual and triple pass radiators are pressure sensitive (need high pressure capability not high flow dependant).

Bigger core tube diameter is preferred? Vs smaller tube with increased count.