Seeking better cooling distribution in block - GT-R Register - Official Nissan Skyline and GTR Owners Club forum

makenski · 26th June 2008, 06:06 PM

Hello,

I been trying to figure out a way to equalize the cooling done within the rb26. I know that the engine gets progressively hotter starting at cylinder one to cylinder six being hottest. This is what I believe the reason why #6 runs leaner.

I heard of a GT mod, which eliminates the ITBs, but it is out of question, I am going to keep the ITBs.

I also heard there has been modifications to widen the passage ways for coolant flow better at the rear of the head, anyone done or seen this before?

And lastly, I know the n1 block has been designed to have better coolant flow, does anyone know what the difference in the flow of the n1 compared to stock?

Thanks for your time.

Spearmint · 26th June 2008, 06:17 PM

I can't really help with your questions other than I believe when tuning a little more fuel is thrown in the last couple of cylinders to compensate for the poor coolant circulation to the rear of the block.

paul cawson · 28th June 2008, 05:19 PM

Quote:

Originally Posted by makenski

I also heard there has been modifications to widen the passage ways for coolant flow better at the rear of the head, anyone done or seen this before?

The rear cylinder head welsh plug is removed and the water ways cleaned and polished

makenski · 28th June 2008, 08:01 PM

Quote:

Originally Posted by paul cawson

The rear cylinder head welsh plug is removed and the water ways cleaned and polished

It's your car, if that is your car on your sig, that I heard this widening was done. I have all my freeze plugs out, so upon visual glance, I see two passage ways to near front of the hole, and two on the immediate sides of the hole.

In other words, can you be more descriptive. Plus, how did this effect your cooling?

Thanks.

paul cawson · 28th June 2008, 10:55 PM

No not mine, its a well known dRIFT R32 GTST,with RB26 fitted and as you say the head water way modifications.

kismetcapitan · 29th June 2008, 03:03 AM

Good info - I assume the welsh plug is reinstalled after the polishing!

makenski · 29th June 2008, 05:42 AM

Hmm.. I have a problem with polishing the coolant, due to the dipples are meant cause turbulence, which allows more coolant to spread over the area, by adding a smooth area the hot coolant will just want to flow over the surface continously, instead of mixing with the above flow...basicly it loses it cooling potential.

It's too bad you can't tell more about that mod.

beaumackenzie · 29th June 2008, 09:44 AM

this is where i think the earlier rb20dets still had a advantage over the later rb's with the three seperate pipes coming out from under the intake manifold back to the radiator as it let the hot water flow away from the back of the block sooner than the rb25's and gtr's as the water still has to travel back along the intake side of the block before exiting back to the radiator...it was a good idea i dint know why they removed it from later designs.

paul cawson · 29th June 2008, 11:06 AM

Quote:

Originally Posted by makenski

Hmm.. I have a problem with polishing the coolant, due to the dipples are meant cause turbulence, which allows more coolant to spread over the area, by adding a smooth area the hot coolant will just want to flow over the surface continously, instead of mixing with the above flow...basicly it loses it cooling potential.

It's too bad you can't tell more about that mod.

Yes its easy to make things worse with only half the picture, I know that on a smooth surface micro bubbles form which help heat transfer, the opposite to what seems logical. The plug is not put back after but a screw in type fitted. This may be bigger to gain better access I will have to try and find the pictures of the mod again

Info on cooling and micro bubbles
BOILING HEAT TRANSFER

SamuraiSam · 29th June 2008, 05:47 PM

To prevent air bubbles (that prevent direct block-to-water contact, hindering heat transfer) use a cooling system surfectant such as Redline Water Wetter. Using a 33/66 mix of distilled water to ethylene glycol coolant helps too.

makenski · 29th June 2008, 08:32 PM

I been summing up that trapped air is causing the rb cooling trouble, and possible caviation.

Which makes sense since water boils, so by raising the pressure of the system raises the boiling temp of water. But trap air within the system creates hot spots.

gibson · 29th June 2008, 09:02 PM

why change the block and head water ways ??? why not increase the radiator or go charge cooling ...and air removal tank.
Number 6 is lean due to air fuel mix not really water temp.

I do agree with the trapped air idea hot spots are present due to the long 6 cylinder lay out of the RB ..water and oiling do cause a few small probs.

just my 2p

GT-R Glenn · 29th June 2008, 09:40 PM

Quote:

Number 6 is lean due to air fuel mix not really water temp.

Dual entry fuel rails .
I have pcx somewhere of a mod for waterways ..
Ill try and find it

kismetcapitan · 30th June 2008, 01:31 AM

whoa, so if you have a dual entry fuel rail then the extra-fuel-on 5-and-6 isn't necessary anymore?

I would still keep extra fuel (just a bit) on those as they are still subject to being hot (last to get coolant as mentioned) plus #6 gets all the leftover air not used by the other cylinders (causing lean running). Until I get a Nismo intake plenum, its cheaper to just add a bit of fuel via the injector trims

GT-R Glenn · 1st July 2008, 01:50 AM

You dont have to reinvent the wheel, all this stuff has already been done.

I found this on one of my old cd's

Not written by me, just collected.

This is the GT cooling setup you see on some of the race
cars such as JUN and the Exvitermini stuff.
Using a mill you plunge down to the water passage
in the manifold between ports 1-2, 3-4 and 5-6.
I then welded a -8 male an fitting to the manifold.
This will run to a reservoir that will also be a merge
for the water returns for the turbo's.
From there it will run back to the radiator.
Basically, all the water leaves the head and runs to
the front of the intake via the log on the bottom.
To help expidite coolant flow from the head we supplement
by adding additional outage points from the manifold.
It would have probably looked a bit more clean on the
bottom of the manifold, but might as well show it off.

26th June 2008, 06:06 PM	#1 (permalink)
makenski GTR Register Member Join Date: Oct 2007 Posts: 40	Seeking better cooling distribution in block Hello, I been trying to figure out a way to equalize the cooling done within the rb26. I know that the engine gets progressively hotter starting at cylinder one to cylinder six being hottest. This is what I believe the reason why #6 runs leaner. I heard of a GT mod, which eliminates the ITBs, but it is out of question, I am going to keep the ITBs. I also heard there has been modifications to widen the passage ways for coolant flow better at the rear of the head, anyone done or seen this before? And lastly, I know the n1 block has been designed to have better coolant flow, does anyone know what the difference in the flow of the n1 compared to stock? Thanks for your time. Last edited by makenski; 26th June 2008 at 06:09 PM.

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26th June 2008, 06:17 PM	#2 (permalink)
Spearmint GTR Register Member Join Date: Aug 2005 Location: Northamptonshire Posts: 799	I can't really help with your questions other than I believe when tuning a little more fuel is thrown in the last couple of cylinders to compensate for the poor coolant circulation to the rear of the block.

28th June 2008, 10:55 PM	#5 (permalink)
paul cawson New Users Join Date: Jul 2003 Location: Essex Posts: 2,061	No not mine, its a well known dRIFT R32 GTST,with RB26 fitted and as you say the head water way modifications.

29th June 2008, 03:03 AM	#6 (permalink)
kismetcapitan GTR Register Member Join Date: Nov 2005 Location: Seoul Korea Posts: 6,315	Good info - I assume the welsh plug is reinstalled after the polishing!

29th June 2008, 05:42 AM	#7 (permalink)
makenski GTR Register Member Join Date: Oct 2007 Posts: 40	Hmm.. I have a problem with polishing the coolant, due to the dipples are meant cause turbulence, which allows more coolant to spread over the area, by adding a smooth area the hot coolant will just want to flow over the surface continously, instead of mixing with the above flow...basicly it loses it cooling potential. It's too bad you can't tell more about that mod.

29th June 2008, 09:44 AM	#8 (permalink)
beaumackenzie GTR Register Member Join Date: Jan 2008 Location: P.N NZ Posts: 279	this is where i think the earlier rb20dets still had a advantage over the later rb's with the three seperate pipes coming out from under the intake manifold back to the radiator as it let the hot water flow away from the back of the block sooner than the rb25's and gtr's as the water still has to travel back along the intake side of the block before exiting back to the radiator...it was a good idea i dint know why they removed it from later designs.

29th June 2008, 05:47 PM	#10 (permalink)
SamuraiSam GTR Register Member Join Date: Oct 2007 Posts: 390	To prevent air bubbles (that prevent direct block-to-water contact, hindering heat transfer) use a cooling system surfectant such as Redline Water Wetter. Using a 33/66 mix of distilled water to ethylene glycol coolant helps too.

29th June 2008, 08:32 PM	#11 (permalink)
makenski GTR Register Member Join Date: Oct 2007 Posts: 40	I been summing up that trapped air is causing the rb cooling trouble, and possible caviation. Which makes sense since water boils, so by raising the pressure of the system raises the boiling temp of water. But trap air within the system creates hot spots.

29th June 2008, 09:02 PM	#12 (permalink)
gibson GTR Register Member Join Date: Feb 2005 Location: hertfordshire Posts: 386	why change the block and head water ways ??? why not increase the radiator or go charge cooling ...and air removal tank. Number 6 is lean due to air fuel mix not really water temp. I do agree with the trapped air idea hot spots are present due to the long 6 cylinder lay out of the RB ..water and oiling do cause a few small probs. just my 2p

30th June 2008, 01:31 AM	#14 (permalink)
kismetcapitan GTR Register Member Join Date: Nov 2005 Location: Seoul Korea Posts: 6,315	whoa, so if you have a dual entry fuel rail then the extra-fuel-on 5-and-6 isn't necessary anymore? I would still keep extra fuel (just a bit) on those as they are still subject to being hot (last to get coolant as mentioned) plus #6 gets all the leftover air not used by the other cylinders (causing lean running). Until I get a Nismo intake plenum, its cheaper to just add a bit of fuel via the injector trims

1st July 2008, 01:50 AM	#15 (permalink)
GT-R Glenn GTR Register Member Join Date: Nov 2002 Location: Waiuku NZ Posts: 1,176	You dont have to reinvent the wheel, all this stuff has already been done. I found this on one of my old cd's Not written by me, just collected. This is the GT cooling setup you see on some of the race cars such as JUN and the Exvitermini stuff. Using a mill you plunge down to the water passage in the manifold between ports 1-2, 3-4 and 5-6. I then welded a -8 male an fitting to the manifold. This will run to a reservoir that will also be a merge for the water returns for the turbo's. From there it will run back to the radiator. Basically, all the water leaves the head and runs to the front of the intake via the log on the bottom. To help expidite coolant flow from the head we supplement by adding additional outage points from the manifold. It would have probably looked a bit more clean on the bottom of the manifold, but might as well show it off.