Rb26 Single Turbo Coolant Routing Question

[SirRacer]

Thanks Shaun for your pictures today via pm.

A well known RB NZ tuner has emailed me back today (i sent the email a while back) and informed me that he plumbs the turbo outlet into the front of the engine. Just makes for a completely different perspective on things.

I had a look through the GTR manual last night and couldnt find anything really in there. 300 odd pages of it though doesnt make for the most interesting reading.

[SirRacer]

After speaking to a guy who makes radiators for a living, i can confirm that the bottom of the radiator (as per discopotatos comments) is in fact the colder piece of the two, and the top is the hot side.

So in theory the thermostat is regulating cold water into the engine so plumbing the hot turbo water in there is a big no no.

Ive heard people taking their feeds from the back of the engine. In theory this is wrong as the cold water is pumped into the bottom of the block (where the feed taps from) and then passes through the head and then is returned through below the plenum. The hose in question runs from the back of the head.

Plumbing it (outlet) into the water hoses at the back of the engine or into the water outlet on the plenum will effectively do the same thing, however plumbing it into the plenum is going to be better because the hose is in view and easy to access should anything go wrong, and also we arent recirculating more hot water into the engine.

Ive attached 2 pictures of how RIPS in NZ does things and also the standard rb20det. It took me a while to get hold of this as i had no access to a stock turbo car, nor had my engine with me.

I hope it answers a few questions about water lines on an rb**det

[discopotato03]

Sir racer as far as I'm concerned the inlet manifold is part of the engine so if you can avoid it then so much the better . Really anything that transfers heat to the coolant (ie turbos/water oil heat exchangers etc) really needs to

have as direct a path as possible to the radiators top tank because you want to transfer the heat input to the radiator not the engine or its externals .

I think the reason Nissan went the way they did was to simplify the overall package and makes life easier on the production line . Also they know what the thermal output of their engines is and cater to that plus a margin for reliability .

Honestly the best system I know of is the one I described before . Find water at the lowest point in the block you can get and and plumb water through the turbo and on to the engines water return to the radiators top tank . That pic from RIPS clearly shows his turbo coolant return to the engines water outlet though if you wanted to make work for yourself a tube bewteen cuts/shut in the top hose and a barb for the inlet wold work as well . Actually if you were having an aluminium radiator fabbed you could spec a barb fitting in the back of the top tank on the near side to avoid running the water tube across the front of the cylinder head .

Just thinking about high mounted turbos for a sec , if they are above the highest point in the engines cooling system then its going to require an even higher mounted water header tank to work reliably at all .

Cheers A .

[SirRacer]

I get what your saying and ideally plumbing the return into the radiator would be a good idea, however for the majority of us running stock radiators this isnt really an options.

For me it comes down to a case of below the plenum or around the back of the head. The way routing the line around the back of the head is more asthetically pleasing however the more logical way would be to run it around the front, where access is easy should anything need checking.

If or when i do go to an aftermarket radiator i will contemplate a fitting going into the top as i can then tidy things up somewhat, and avoid having a line running around the front of the engine.

[Shaun]

Ok, so its been confirmed that the hot water exits the engine via the top radiator hose, and cool water enters the engine via the bottom hose and through the thermostat.

So does this mean that the cool water (turbo feed) should be taken from the low point in the exhaust side of the block (near #6 piston), and the post turbo water should be returned into the top radiator hose via the nipple on the neck at the front of the engine? If so, thats fine and easy but makes me feel a bit stupid because i certainly chose the long way round.

The only other thing is; what do i do about the feed at the back of the engine underneath the plenum. This is connected to the thermostat housing. Do i just block it off?

Its been so long that i forget what it was there for in the standard set up.

This is pretty important because im now thinking that if i was routing water incorrectly, it could have been a contributing factor in my engine failure because of increased thermal load etc.

Shaun.

Edited December 6, 2007 by Shaun

[Butters]

So does this mean that the cool water (turbo feed) should be taken from the low point in the exhaust side of the block (near #6 piston), and the post turbo water should be returned into the top radiator hose via the nipple on the neck at the front of the engine?

Thats exactly what i figured out. No one seems able to confirm this though !

Also a lot of people seem to block up the water pipe thats on the front of the engine. Even seen this on some jap race engines.

So the evidence contradicts the theory that makes sense !!

[Shaun]

Yeah, well ive blocked up the water pipe on the pront of the engine and used the other two sources of coolant, but apparently this is not ideal. Its easy to change, but i just need some confirmation from those who know more than me.

Also, i think maybe its not a good idea to use the big Jap teams as a comparison because i think they'd probably be more inclined to have a dedicated return straight to the radiator or something like that. When i did mine, i saw that many of these cars had blocked off the front return and assumed that they used the other two sources. Maybe that was wrong.

Shaun.

Edited December 7, 2007 by Shaun

[s13_Skyline_inside]

the engine always gets hotter around the rear because water has to travel from the front to the rear of the block thats, why the head gaskets normally let go around piston 5 an 6 if it gets overheated

[Shaun]

Mine let go on #6. Im trying to ensure it doesnt happen again.

[SirRacer]

Hey Shaun,

As ive mentioned in PM RIPS the NZ RB tuner (thats all he does really) has told me to route the return to the front of the engine and take the water from the piece on the block near #5 cylinder.

What you have done is basically just route the water return in a little earlier. I wouldnt think that would have made a massive difference however as the rb20/25's run their water returns there stock (i didnt know that until the other day).

Quite a few people have this wrong so its not a bad mistake at all.

The post by discopotato above is bang on!

Edited December 7, 2007 by SirRacer

[Shaun]

No worries Byron, thanks for that. I still might change it though just so its spot on. I like discopotato's idea of returning it straight into the top tank of an aluminium radiator. Pity i dont have one.

Shaun.

Edited December 7, 2007 by Shaun

[GeeTR]

A thought - Instead of requiring a new alloy rad to plumb in the turbo return to, and the concern with high mounts being the highest link in the cooling system; use a ARC style air removal tank (~$300) (or one of the much cheaper derivative's) and weld a fitting in.

Most people mount the top breather tank, high on the driver side strut tower; which would be higher then the turbo cartridge - booya

Edited December 7, 2007 by GeeTR

[Shaun]

I dont get what you mean. Are you saying to return the water into the breather tank?? There is already a nipple on the front of the engine to return the hot water to the radiator (on the RB256 anyway). I just liked the idea because you wouldnt really see the water return line if it went straight into the radiator. Its just an aesthetic thing i think.

Shaun.

[GeeTR]

I don't get what you mean...

It was a utopic response to Disco, who was suggesting the thermosiphon killing effect of having the turbo cartridge, as the highest point in the system.

Taking a the feed from low in the block, and feeding it high to a breather tank would tick all the required wish list box's including...

I just liked the idea because you wouldn't really see the water return line if it went straight into the radiator.

... without needing a alloy rad, as the return could be hidden around the back of the engine and fed into the breather tank.

Edited December 7, 2007 by GeeTR

[GeeTR]

On the topic of utopia, a bleed tank allows one to setup trick multi point head water relief

... just wanted an excuse to show a pretty CRD setup hehehe.

[discopotato03]

It would be interesting to know why CRD had the water crossover pipe and the rads water inlet on the nearside insted of the std offside . Must have been to get around something on the offside behind the radiator ?

Cheers A .

[Shaun]

Ok, i get what you mean. Ill definately see whether my turbo core is higher than my radiator cap. If so, ill install a breather tank. I dont think it'll be quite as elaborate as the pic above though. Bit of money in those earls fittings!

Shaun.