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Old 11th June 2015, 08:22   #16
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Default Re: Moving the Radiator to the Rear!

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Originally Posted by dhanushs View Post
The amount of water leaving the system = the amount of water entering the system.
Ah, I overlooked that. The entire circuit is full of water, so there is pre-cooled waiting to enter. Thanks.
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Old 11th June 2015, 11:07   #17
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Default Re: Moving the Radiator to the Rear!

My thoughts on the pump is that at a fixed rpm,power = flow rate * head,the head has been increased by the bends and the frictional resistance of the increased piping.Hence the speed with which the water flows through your system might be reduced.
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Old 11th June 2015, 11:25   #18
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Default Re: Moving the Radiator to the Rear!

Pardon me for such a novice question but is it not possible to enclose the entire fans & the radiator section in a plastic container or something and have a duct for the intake of air as in how there is the snorkel for the air intake etc ? This could be removable during normal usage.
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Old 11th June 2015, 11:34   #19
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Default Re: Moving the Radiator to the Rear!

I was going to ask something similar. Would it make sense for you now to add a air scoop of sorts on the roof which feeds the intake of the fans? Could it help in more efficient cooling v/s the current setup?

Also, do add the thermal switch at the earliest, while you have a large system now with more coolant, allowing more laxity in turning on the fans, it should not happen that you are engrossed in a tricky trough and miss out turning on the fans. You could even consider both fans on independent thermal switches perhaps.

Kudos on this build, a rarity in our geography as of now.
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Old 11th June 2015, 14:21   #20
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Default Re: Moving the Radiator to the Rear!

Hi dhanushs!

It seems to be a valid solution for your problem.

My only concern is that by putting radiator at the back you have compromised on the natural flow over of air through the radiator fins.
This will make it less efficient system.
Now with your setup the engine will reach its operating temperature faster, and fan will have to work more to keep the engine at its optimal temperature.
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Old 11th June 2015, 22:16   #21
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Default Re: Moving the Radiator to the Rear!

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Originally Posted by Samurai View Post
Just thinking back to the time I studied hydraulics...

2) The pump will move X amount of water at a given rpm. I don't think that will change with the change in the length or width or bends of the new pipe.

The above is just logical deduction... feel free to poke holes in it.

Since you have invited poking, I shall do so.

Pumps have a head vs flow curve , which typically looks like this.

Name:  CurveslightboxLs.jpg
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When you change the resistance of the system ( more bends, longer pipes, etc) the operating point changes so you get higher pressure but lower flow from the pump.

The curve above is for a single rpm.

In the case of a jeep water pump the rpm varies from 1000-4000 so the system flow rates will vary with that as well.
It can be approximated by drawing parallel curves like the one above.

The OEM design is probably over rated for various reasons so the stock pump should work if its with in 20% extra head requirement.

Last edited by Samurai : 11th June 2015 at 23:43. Reason: attached pic
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Old 12th June 2015, 10:19   #22
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Default Re: Moving the Radiator to the Rear!

Dear Dhanush - first of all, congratulations for successfully doing this work. By the way, cooling system integration and evaluation are my favorite work areas, so here goes:

Remove the filler cap and neck from the radiator and seal it by soldering. Use a Tata Winger (first choice due to rectangular packaging shape) or a Tata Indica (second choice, but also very easily available) degassing tank in the area above the radiator. Connect the degassing tank (filler) outlet to the suction side of the water pump and bleed the topmost points of the engine and the radiator. Use bleeder pipes of Indica. Use metal pipes of the same diameter for connecting. Use Zen heater hose clips for ensuring Japanese specification tight joints and reliability. If you maintain the "head" (hydraulic term for level), you will not need bleeders. As a backup, mount switches on the dashboard to manually operate the fans in case of thermoswitch issue. Impirical ATB is 55 degrees MAX. ATB is nothing great, it is called "air to boil", it is the difference in temperature between the engine outlet coolant temperature and the ambient temperature measured in the shade. Please let me know the sigma of water (capacity in cc). Don't waste money on coolant, do all experimentation with water, establish reliability and then use coolant at 50% concentration level. Specific heat of water is slightly more than coolant so ATB will increase by 3 degrees with coolant.

Best regards,

Behram Dhabhar
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Old 12th June 2015, 10:24   #23
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Quote:
Originally Posted by dhawcash View Post
Those are some neat looking welds on the gi tubes. Did you use arc welding?
Yup.
Quote:
Thumbs up to the twin fan shrouding as well. Was it fabricated or found ready made?
It was fabricated.
Quote:
Congratulations for acquiring a base to make a cab heater for the upcoming winters!
This is temp. After the initial testing stage is done. Will move to covered twin cab. Afterall, all this came into being only after my idea to fit AC. Which will be effective in a closed twin cab.
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Originally Posted by bullrun87 View Post
Did you notice the temperature gauge to be higher than normal when cruising the highway?
Hi, this vehicle isnt intended for highway use. It handles crazy after 60kmph, which is somehow managed by my twin shock custom suspension. However, yes, one drawback of this mod is that the fan will have to stay on for a long time. And, I've decreased the water pump pulley ~10%. Which is more than enough for now.
Quote:
2) Are those the orignal fans or somehow modified?
Nope. nothing in this vehicle is original. Custom radiator. Custom fan.
Quote:
Your coolant flow is definately LOWER than it was before you modified. This reduction in coolant flow should be adequately compensated by increasing the air flow across the radiator\
Yup. However, in this case, I have the double coolant volume, which works in my favor. And also, not only the radiator. The GI pipes to and fro the radiator also work in cooling the coolant. Temperatures are pretty much consistent. Infact, lesser, so that I have to keep the fan OFF.

Quote:
Originally Posted by biju1971 View Post
My thoughts on the pump is that at a fixed rpm,power = flow rate * head,the head has been increased by the bends and the frictional resistance of the increased piping.Hence the speed with which the water flows through your system might be reduced.
Quote:
Originally Posted by rev_rohit View Post
My only concern is that by putting radiator at the back you have compromised on the natural flow over of air through the radiator fins.
This will make it less efficient system.
Quote:
Originally Posted by latentpotential View Post
I was going to ask something similar. Would it make sense for you now to add a air scoop of sorts on the roof which feeds the intake of the fans? Could it help in more efficient cooling v/s the current setup?
Hi,

Two factors compensate the ram air effect of cooling.
  • I have double, or more coolant volume in the system. IIRC its more than ~20 liters.
  • The GI pipes to and fro along the system act as small time radiators.
Quote:
Originally Posted by sumeethaldankar View Post
Pardon me for such a novice question but is it not possible to enclose the entire fans & the radiator section in a plastic container or something and have a duct for the intake of air as in how there is the snorkel for the air intake etc ? This could be removable during normal usage.
Hi, the radiator isnt closed in any way. So, fans have enough air to work. Regarding ram air. See the comments above.
Quote:
Originally Posted by latentpotential View Post
... it should not happen that you are engrossed in a tricky trough and miss out turning on the fans. You could even consider both fans on independent thermal switches perhaps.
Yup. Been there. Also, if somebody else takes the vehicle for a drive. Yes, I'll fix the thermoswitches ASAP.
Quote:
Originally Posted by latentpotential View Post
Kudos on this build, a rarity in our geography as of now.
Thanks!

Quote:
Originally Posted by DHABHAR.BEHRAM View Post
Dear Dhanush - first of all, congratulations for successfully doing this work.
Thank you sir!
Quote:
Use bleeder pipes of Indica.
Just saw these yesterday. And is a practical solution for my problem. I dont need to fabricate and waste money.
Quote:
As a backup, mount switches on the dashboard to manually operate the fans in case of thermoswitch issue.
Yes, I have two switches for fans which will stay.
Quote:
Please let me know the sigma of water (capacity in cc)
Since I have to bleed the system, and cant fill it in one shot. How do I measure the total water capacity? btw, I guess its ~20 liters.
Quote:
Don't waste money on coolant
Nope. Running on water till this is permanant.

- And, thank you sir for the comments. I will follow, and let you know the results.

Last edited by Gannu_1 : 12th June 2015 at 12:03. Reason: Back to back posts merged.
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Old 12th June 2015, 11:55   #24
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Default Re: Moving the Radiator to the Rear!

This is a seriously hard core mod! Congrats on the successful job.
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Old 12th June 2015, 12:07   #25
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Default Re: Moving the Radiator to the Rear!

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Originally Posted by dhanushs View Post
Attachment 1380189

So, thats pretty much it. Fellow members please feel free to add/correct to the above.
Thats not it, tell us more about your engine, turbo, fuelling, suspension mods. I am eagerly waiting for that information.
Have you gave a thought on adding additional water pump in circuit for those crazy high reving mud incline and continuous high reving mud plugging scenario. just as a back-up?

Shubhendra Singh
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Old 17th June 2015, 10:52   #26
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Default Re: Moving the Radiator to the Rear!

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Originally Posted by Shubhendra View Post
Thats not it, tell us more about your engine, turbo, fuelling, suspension mods. I am eagerly waiting for that information.
Hi Shubendra,

I have a Nissan SD25 engine, which I have turbocharged. Apart from FIP, have an electric fuel pump. Suspension is custom. Will post all the details in a separate thread.
Quote:
Have you gave a thought on adding additional water pump in circuit for those crazy high reving mud incline and continuous high reving mud plugging scenario. just as a back-up?
Well, just back from a three day continuous recce, which included some serious high revving. The engine is running much much cooler than before.

Eg:


Last edited by benbsb29 : 18th June 2015 at 05:25. Reason: Removed first video link as requested.
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Old 10th February 2016, 15:42   #27
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Default Re: Moving the Radiator to the Rear!

Thought to share few pics of rear radiator conversion done by friend. Vehicle in question is SPOA 550 with Toyota 14B. Pipes used for plumbing were industrial grade flexi hydraulic pipes. A grill to front of radiator and a fan to rear of radiator has been attached. After 1-2 offroad trips and close to 1000 kms of highway driving system is holding fine and temperature donít exceed after 80-90 degree cel.

Moving the Radiator to the Rear!-img_20151210_152711.jpg

Moving the Radiator to the Rear!-img_20151210_162127.jpg

Moving the Radiator to the Rear!-img_20151210_162134.jpg

Moving the Radiator to the Rear!-img_20151210_162146.jpg

Moving the Radiator to the Rear!-img_20151210_162159.jpg

Regards,
Shubhendra Singh
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