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Old 06-07-2009, 09:32 PM   #1
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Default My latest coolant reroute

So after my high coolant temperatures at the track I have been on a quest to bring them down. I am using a multi-pronged approach, one of which is to rethink the coolant reroute. I have incorporated several elements from previous discussions/implementations posted here as there are a lot of great ideas.

I have already done the spacerless reroute, and this is in fact what I was running at the track. The coolant flow at the front of the head is completely plugged (freeze plug) and all flow exits the back of the head.

One of the reasons I think I may have been having problems with temperature is the heater core recirculating back into the 'mixing manifold' or in my case the lower radiator hose. Because of this route, there is a significant portion of the flow that is not circulating through the radiator. The pro is that it is good for a street car; quick heatup, no overcooling (been there, done that). The con is that it is not great for a track car for the reason already stated. This has been discussed at length in other threads so I will not rehash it all here. But what am implementing is the idea of recirculating the heater core loop into the upper radiator hose, but regulating it with an in-line thermostat.

Another change is that I am redoing the way the small diameter lines circulate through the heater core and turbo; I am running them in parallel. I am also eliminating the circulation through the throttle body. There are two points at which flow is tapped for the two parallel loops. One is the existing, stock point at the back of the head. The other is from the pre-thermostat point in the in-line housing for the heater core flow. The former will be the one that feeds the oil cooler. The latter will be the one that feeds the turbo. The flows are teed together just before the bung located at the inlet manifold to the water pump.

I'll post up some pictures of the actual parts. But for now here is a diagram of the reroute. I am looking for some input to see if I overlooked anything or if anyone sees any potential problems. The car is offline right now so this is one of several things I am working on while I can.

A quick comment on the dual thermostats. Right now they are both 180 deg F units. I think I may switch the one at the back of the head to a 200 deg F unit. That way the flow will be biased through the heater core. If that flow is not enough to keep the engine cool, then the one at the back of the head will open and provide additional flow.

Also, note that there is continuous flow through the motor. The flow through the parallel lines for the turbo and oil cooler are always free to flow. Plus I drilled a small hole, about 3/16" in the flange of the front t-stat so it always flows as well. Hopefully those three paths will be enough to keep a sufficient amount of coolant moving through the motor during warm-up, without flowing too much and keeping the motor from warming up completely.

I am also trying out my previously posted double oil cooler sandwich idea using two stock water/oil heat exchangers. I already installed it and routed the coolant lines and it all fits. I'll be installing a temp sending unit in the oil drain plug to see what the resulting delta-T is between the oil and the coolant.
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Old 06-07-2009, 09:44 PM   #2
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The only thing I see is the possible lack of flow before the t-stats open.
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Old 06-07-2009, 10:03 PM   #3
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Yep, I agree. There is flow before the t-stats open, just not sure whether it is enough. If it is not enough, I can always drill more holes in the front t-stat flange to allow more flow to bypass the t-stat.

But, how do I know if there is enough? I am not sure of a good way to tell if I am getting enough flow through the head before the t-stats open, short of something like instrumenting the head with a bunch of thermocouples to look for hot spots, or checking the flow rates against a stock setup.
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Old 06-07-2009, 10:33 PM   #4
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Originally Posted by ZX-Tex View Post
Yep, I agree. There is flow before the t-stats open, just not sure whether it is enough. If it is not enough, I can always drill more holes in the front t-stat flange to allow more flow to bypass the t-stat.
So you already have holes drilled? How many, how big? If the holes combined are as big or close to the inner diameter of the heater hoses I would say your good then.
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Old 06-07-2009, 10:41 PM   #5
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Well I am not sure I want them to be that large. If they are, I think I will be back to having the same problem I had before with the unregulated upper radiator heater core hose return. There is too much flow through the radiator when warming up and cruising, and the car takes too long to get up to temperature, or never gets there.
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Old 06-08-2009, 12:25 AM   #6
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Why do you guys keep re-inventing the re-route?

With this routing, the heater will see very little flow.
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Old 06-08-2009, 12:55 AM   #7
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Default I have done 6 re routes on '01 - '05

This works! Wheel b/4 reinvention! These kits are for '01 - '05 cold side S/C or Naturally aspirated. $175 if any one wants one. I am working on a kit for the intake side. I will say that stock coilpacks are a problem, of course any one concidering a reroute is a "track dog" and has changed to COPS anyway.
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My latest coolant reroute-coolant-bypass-070.jpg   My latest coolant reroute-coolant-bypass-054.jpg   My latest coolant reroute-coolant-bypass-055.jpg  
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Old 06-08-2009, 10:56 AM   #8
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Quote:
Originally Posted by JasonC SBB View Post
Why do you guys keep re-inventing the re-route?

With this routing, the heater will see very little flow.
Well, I think I answered that already, but maybe not, so I'll try again. If the heater core return goes into the lower hose, like stock, then (I think) there is too much flow that is not circulating through the radiator and the car runs hot. If the heater core return goes into the upper radiator hose, unregulated, then the car runs too cool for the street. The winters here in South Texas are not harsh so little heater core flow is not a big deal.

I have seen three-way regulators, though not big enough for a car. Instead of blocking/opening flow based on inlet temperature, they divert flow between two different outlets. The application I worked on was for a heat exchanger for a high-powered radar system; that is all I will say about that. But basically it either took the incoming coolant and diverted it to the heat exchanger, or flowed it directly back into the coolant loop. That way there was always full flow through the system, but temperature was still regulated.

If I could find one of these regulators with 5/8" inlet-outlets (or adaptable to that) it would be ideal. One output goes to the upper, one goes to the lower. Done.
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Old 06-08-2009, 11:41 AM   #9
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Quote:
Originally Posted by fun02se View Post
This works! Wheel b/4 reinvention! These kits are for '01 - '05 cold side S/C or Naturally aspirated. $175 if any one wants one. I am working on a kit for the intake side. I will say that stock coilpacks are a problem, of course any one concidering a reroute is a "track dog" and has changed to COPS anyway.
I would think that the exhaust manifold would absolutely dump heat into the coolant pipe, I'd at least wrap it.
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Old 06-08-2009, 11:45 AM   #10
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I used a cold-side reroute. No way I wanted to route mine hot-side with the S4 manifold.

BTW noob if you want to sell your reroute kit, which really has nothing to do with mine, please start a new thread.
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Old 06-08-2009, 12:03 PM   #11
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What's wrong with the standard reroute then add a valve or t-stat to stop flow through the heater when hot?
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Old 06-08-2009, 12:08 PM   #12
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Yeah that could work too, but then you are giving up some flow. On the street, that is no problem. But I think it is better when the engine is shedding a LOT of heat, like on the track (where I had the problem), to use all available flow through the engine and radiator to help with cooling.

Where does one get a standard packaged t-stat that closes with heat instead of opens? I would be interested in that.
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Old 06-08-2009, 01:04 PM   #13
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Someone previously suggested an oil cooler thermostat
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Old 06-08-2009, 01:08 PM   #14
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IIRC they talked to an oil thermostat supplier who said it would not work correctly for some reason, but I could be wrong.
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Old 06-08-2009, 01:21 PM   #15
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Yes, the use of an oil T-stat was discussed with one of the companies that makes them, and it was concluded that due to the much lower viscosity of water, the coolant would pretty much bypass the thermostat all the time. (Oil thermostats never close completely- they have a bypass path designed to allow 10-15% "leakage" in order to maintain circulation through the whole system. With water instead of oil, you'd get closer to 100% leakage.)
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Old 06-08-2009, 01:21 PM   #16
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Why not just restrict flow between the heater core and the lower rad hose? Many Hondas have a little ball valve that only opens when the climate control is set to 'hot'. Nab one out a junkyard and find a reasonable setting that gets some flow, but not enough to hurt cooling. Or just close it entirely before a session.
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Old 06-08-2009, 01:46 PM   #17
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I have suggested a tap in that heater return line a long time ago, would still work actually. Just find a tap.
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Old 06-08-2009, 01:48 PM   #18
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Quote:
Originally Posted by vehicular View Post
Why not just restrict flow between the heater core and the lower rad hose? Many Hondas have a little ball valve that only opens when the climate control is set to 'hot'. Nab one out a junkyard and find a reasonable setting that gets some flow, but not enough to hurt cooling. Or just close it entirely before a session.
That would cause water to stop flowing past the rear mounted thermostat and cause it to not open as readily when necessary.



One possible fix would be simply to reduce flow volume through the heater core enough that it wouldn't be as much a detriment to the temp at the mixing manifold, but would still have a little flow for the benefit of the thermostat and for offering a little heat from the heater. Like 1/3 or 1/4 the flow?
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Old 06-08-2009, 01:51 PM   #19
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Quote:
Originally Posted by JasonC SBB View Post
What's wrong with the standard reroute then add a valve or t-stat to stop flow through the heater when hot?
A normally open 12v solenoid valve,wired n parallel w/ the rad fan should work.
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Old 06-08-2009, 03:04 PM   #20
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Zxtex, the problem I see with your original sketch is that before the rear thermostat opens, the only coolant flow through the engine is through that heater hose, which you've blocked with the second thermostat. I will be doing this same reroute without the second thermostat, soon. It is encouagimg to hear that it is too cold for the streets.

And to save me five minutes of searching, do you remember the freeze plug diameter for the front of the block?

Last edited by curly; 06-21-2009 at 03:05 PM.
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