Calling all Honda experts. Coolant question. - LotusTalk - The Lotus Cars Community
 
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post #1 of 19 (permalink) Old 01-04-2018, 07:11 PM Thread Starter
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Calling all Honda experts. Coolant question.

Specifically, @ageshelin and @dstevens , but also anyone else with knowledge of the Honda K20 or K24 motors.

I am going to plumb in a Laminova oil-to-water heat exchanger for my oil cooling. I want the temperature gradient to go:

engine --> oil --> radiator --> back to engine

So I need to CONFIRM which direction the coolant flows in the system. Does it come out the head, go through the radiator, then back to the engine block through the thermostat? Or is it the other way around?

I've researched and searched and searched on all the Honda forums and NO ONE has confirmed the coolant flow. It's so weird. It's almost like finding a bug in the Matrix. Lots of threads where people just say they've gotten contradicting information from "experts".

My engine is out of the car right now so I can't fire it up to confirm myself, unfortunately.

Thinking of K-swapping? Here's an idea of the cost involved.

2006 LOTUS EXIGE (ASPEN WHITE) Honda K24A2 + MPx90 supercharger. 322whp/271lb-ft @13psi. Build thread here.
1994 AUTOZAM AZ-1 MAZDASPEED Japanese Super Kei!
2014 FIAT 500e Hydroelectric powered EV daily driver.
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post #2 of 19 (permalink) Old 01-04-2018, 10:06 PM
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I've always understood the Honda's coolant flow to be 'backwards', that is, it exits the block at the thermostat near the BOTTOM of the rad and flows upward. I remember Dave Koski having difficulties with his K20 equipped S1 Elise due to this.

Sometimes the Honda coolant systems are difficult to bleed or 'burp' due to this design.


Atwell Haines

(Lots of Hondas over the years, currently K24 CR-V)

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post #3 of 19 (permalink) Old 01-04-2018, 10:23 PM Thread Starter
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Quote:
Originally Posted by carbuff View Post
I've always understood the Honda's coolant flow to be 'backwards', that is, it exits the block at the thermostat near the BOTTOM of the rad and flows upward. I remember Dave Koski having difficulties with his K20 equipped S1 Elise due to this.

Sometimes the Honda coolant systems are difficult to bleed or 'burp' due to this design.


Atwell Haines

(Lots of Hondas over the years, currently K24 CR-V)
I've read this as well, and it makes sense to me just by way of common sense. Thermostat is what keeps the coolant circulating in the block until it gets hot enough, then the wax expands, opening the thermostat, letting the coolant flow out into the radiator where it is cooled, then makes its way back into the engine via the top (head).

BUT.

I've read that it's the other way. So.

Still no confirmation.

Thinking of K-swapping? Here's an idea of the cost involved.

2006 LOTUS EXIGE (ASPEN WHITE) Honda K24A2 + MPx90 supercharger. 322whp/271lb-ft @13psi. Build thread here.
1994 AUTOZAM AZ-1 MAZDASPEED Japanese Super Kei!
2014 FIAT 500e Hydroelectric powered EV daily driver.
2007 SUZUKI SV650 Track bike.
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post #4 of 19 (permalink) Old 01-05-2018, 08:46 AM Thread Starter
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Well, after doing some more research, I think I may have answered my own questions BUT would still love for someone else to chime in, as well.

Seeing as how the K24 water pump is a centrifugal pump design:



... this means that the coolant is drawn toward the eye of the impeller and thrown outwards. Meaning it pumps fluid outwards into the casing and up into the block.

Here is the water pump mounted to the block (the largest pulley seen in the middle):



So it appears we have an answer: The coolant flow on a Honda K20 / K24 exits the engine at the top (the head), flows to the radiator, and re-enters the engine through the bottom of the block (through the thermostat). In other words, it flows from top to bottom.

Looks like my original location for mounting the Laminova will have to be re-thought.

Thinking of K-swapping? Here's an idea of the cost involved.

2006 LOTUS EXIGE (ASPEN WHITE) Honda K24A2 + MPx90 supercharger. 322whp/271lb-ft @13psi. Build thread here.
1994 AUTOZAM AZ-1 MAZDASPEED Japanese Super Kei!
2014 FIAT 500e Hydroelectric powered EV daily driver.
2007 SUZUKI SV650 Track bike.
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post #5 of 19 (permalink) Old 01-05-2018, 10:06 AM
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From my RSX K20A manual.


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Last edited by Vulcan Grey; 01-05-2018 at 10:46 AM.
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post #6 of 19 (permalink) Old 01-05-2018, 10:16 AM Thread Starter
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Originally Posted by Vulcan Grey View Post
Well, ****, Travis.

Thinking of K-swapping? Here's an idea of the cost involved.

2006 LOTUS EXIGE (ASPEN WHITE) Honda K24A2 + MPx90 supercharger. 322whp/271lb-ft @13psi. Build thread here.
1994 AUTOZAM AZ-1 MAZDASPEED Japanese Super Kei!
2014 FIAT 500e Hydroelectric powered EV daily driver.
2007 SUZUKI SV650 Track bike.
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post #7 of 19 (permalink) Old 01-05-2018, 10:18 AM
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K24 looks a bit different

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post #8 of 19 (permalink) Old 01-05-2018, 10:20 AM
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I don't see the "water outlet" on the K24?
But it's there on the K20 diagram from my RSX manual above

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post #9 of 19 (permalink) Old 01-05-2018, 10:25 AM
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NO WONDER no one can tell...

Atwell Haines
'88 Esprit
Succasunna, NJ USA


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post #10 of 19 (permalink) Old 01-05-2018, 10:25 AM Thread Starter
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Thanks for posting those, Travis. Really appreciate it. Hopefully this search will come up when someone searches for coolant flow direction Honda K20 K24 in the future.

Thinking of K-swapping? Here's an idea of the cost involved.

2006 LOTUS EXIGE (ASPEN WHITE) Honda K24A2 + MPx90 supercharger. 322whp/271lb-ft @13psi. Build thread here.
1994 AUTOZAM AZ-1 MAZDASPEED Japanese Super Kei!
2014 FIAT 500e Hydroelectric powered EV daily driver.
2007 SUZUKI SV650 Track bike.
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post #11 of 19 (permalink) Old 01-05-2018, 10:32 AM
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The Lotus Esprit cooling diagram includes arrows!!!...

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post #12 of 19 (permalink) Old 01-05-2018, 10:34 AM Thread Starter
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Quote:
Originally Posted by carbuff View Post
NO WONDER no one can tell...
Quote:
Originally Posted by Vulcan Grey View Post
The Lotus Esprit cooling diagram includes arrows!!!...
Hahaha! I know! I was really expecting a diagram like the one you posted, Travis. Arrows. Just give me the damned arrows to make it easy.

Thinking of K-swapping? Here's an idea of the cost involved.

2006 LOTUS EXIGE (ASPEN WHITE) Honda K24A2 + MPx90 supercharger. 322whp/271lb-ft @13psi. Build thread here.
1994 AUTOZAM AZ-1 MAZDASPEED Japanese Super Kei!
2014 FIAT 500e Hydroelectric powered EV daily driver.
2007 SUZUKI SV650 Track bike.
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post #13 of 19 (permalink) Old 01-05-2018, 10:36 AM
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you can see the water comes in from the outside of the pump and goes into the block also at the outside via that ramp.
But the water pump is a bit different than the Honda




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post #14 of 19 (permalink) Old 01-05-2018, 10:37 AM
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BTW, the Esprit feeds into the top right of the radiator and returns from the lower left.

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post #15 of 19 (permalink) Old 01-05-2018, 10:42 AM
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here a good diagram of how a water pump works


The esprit shop manual is good bedtime reading

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post #16 of 19 (permalink) Old 01-05-2018, 12:45 PM
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@Butters - I was going to post the same page that Travis posted for the K20 this morning, but the site ate my composition twice and I gave up. Home now on the desktop ... in case it helps, here's a link to an Acura RSX K20 manual: Manual. Page 226 of the pdf is the page showing the "outlet."

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post #17 of 19 (permalink) Old 01-05-2018, 01:37 PM Thread Starter
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Quote:
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@Butters - I was going to post the same page that Travis posted for the K20 this morning, but the site ate my composition twice and I gave up. Home now on the desktop ... in case it helps, here's a link to an Acura RSX K20 manual: Manual. Page 226 of the pdf is the page showing the "outlet."

Glen
Sweeeeet. Thanks, Glen! I appreciate all your help, sir!

Thinking of K-swapping? Here's an idea of the cost involved.

2006 LOTUS EXIGE (ASPEN WHITE) Honda K24A2 + MPx90 supercharger. 322whp/271lb-ft @13psi. Build thread here.
1994 AUTOZAM AZ-1 MAZDASPEED Japanese Super Kei!
2014 FIAT 500e Hydroelectric powered EV daily driver.
2007 SUZUKI SV650 Track bike.
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post #18 of 19 (permalink) Old 01-29-2018, 12:24 PM
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Late to this thread. Coolant flows out of the cylinder head, through the radiator and back into the thermostat housing. I'm 100% sure of this.
When the thermostat is closed the coolant will bypass the radiator via the smaller diameter hose which runs from the cylinder head outlet to the thermostat housing.
I plumbed in a laminova on the radiator return hose, but that was a race car and I wanted the oil to stay around 210F - 230F (which it did).

2005 Elise with Honda engine
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post #19 of 19 (permalink) Old 04-02-2018, 10:51 AM
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re: Honda K water flow

Sorry for late reply to this thread. There is a lot of confusion in the Honda community about the water flow.
I could not get a definitive answer, until, now! Since, I used an electric pump and sold the original and did not
notice the notation in the RSX manual, I have been doubting myself all this time! Thank You!

I did the water flow the right way. Block-first design is most common in stock engines. It decreases thermal stress on the
aluminum heads during start-up and idle. Hence, I made the right choice based on this logic. Also, looking at the
diagram in the RSX manual, the top radiator hose is always for hot water i.e. return from engine. AS the water cools it drops in the radiator top the
outlet, easier.

Race engines are pre-heated or warmed up carefully. It is more advantageous to plumb the head first, since it is the hottest part
and more sensitive to heat. If you look at all the NASCAR engines (especially when they were based on stock blocks), not only did the water enter the heads, first,
but an attempt was made to have an inlet by each cylinder ot at least front and back (4 inlets).

I would plumb any oil/water cooler (heat exchanger) on the hot side i.e. after the engine and before the radiator. You want oil at 80 to 100C. Oil/Water
cooler warms up the oil when you start the motor (this is good, unless you have a dry sump with a tank heater). The oil flow and lower heat capacity of oil will
not affect the cooling system and vise-versa. We can start a big argument about what the optimum water temperature is, let us not. But
there should be no argument that oil should be between 80 and 100C. Synthetic can run up to 140 and mineral oil 120, but I would not feel comfortable,
if the steady state oil temperature is over 120 or below 70. The ASTM oil viscosity test is conducted at 80 and 100, VI is calculated from that. There is
a separate test for the cold/winter rating. (I still remember doing this with a glass manometer and a stopwatch, 33 years, ago!).

Has anybody tried or knows about running a Honda K motor for track use with the flow of water reversed i.e. head-first with some benefit? (I have no heater, thermostat or oil/water cooler, so I can switch with ease, if it is advantageous. Just remembered that my turbo is water cooled...)

Anton


Quote:
Originally Posted by dstevens View Post
Late to this thread. Coolant flows out of the cylinder head, through the radiator and back into the thermostat housing. I'm 100% sure of this.
When the thermostat is closed the coolant will bypass the radiator via the smaller diameter hose which runs from the cylinder head outlet to the thermostat housing.
I plumbed in a laminova on the radiator return hose, but that was a race car and I wanted the oil to stay around 210F - 230F (which it did).

Anton
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