20v cooling re-visited

[Sam_Q]

As many of you would know I wrote a guide a while back on how to convert a cooling system on a 20v to a rwd format. I used part of other guides and part of what I figured out for myself. Now I have since learnt that Toyota made their coolant run the way it did for a reason. I figured at the time I was messing with something I didnt fully understand but now I like to think better.

Here are some main components of a 20v cooling system breaking it down oversimplified for the purposes of this explination.

radiator top: hot water in
radiator bottom: cold water out
head inlet ports channel: coolant passage thats under the 4 inlet ports
block- collant passages through the block
rest of head- the coolant passages though it with the exception of the inlet channel, exits the back exhaust side of head

Anyhow heres a standard flow path:


- Radiator cold water out
- goes into the back of head and flows under inlet ports and out at the front
- out of front of head then sucked in the block
- through the block then the head and out again

cool in-> inlet side -> block -> other side of head -> out

I know the OEM setup ran the coolest water through the passage under the inlet ports, now I can only assume they did this on purpose to cool that sideo of the head to keep the inlet ports cooler and therfore the inlet air cooler.


- however mine is all back to front:

- cool water out, sucked into block
- through block into head on exhaust side
- water bypassed from what was the outlet port to what was the inlet port
- water in the inlet port though the inlet channel
- out to rad

cool in-> block -> head (ex) -> head (inlet passage) -> hot out


With my setup I am purposefully putting the hottest water though that passage under the inlets, so I know I would be heating up my inlet ports more


how all that over and done with heres my questions:

With that side of the head hotter would it really heat the air up much? would it really make a difference?


I am thinking of doing a different setup for my next engine, because I want the advantage of the cooler ports but hate extenal thermostats I thought of this:


cold water -> pipe to back of head (inlet port passage) -> adapted into the inlet of my RWD 4ac water pump -> block -> head -> pipe back to the rad

the only difference from factory is that I have a thermostat between the end of the inlet port passage and the block unlike stock which has it between the ports that are the top and bottom radiator hose inlet/oulets.

Would it work?

thanks for anyone who bothered to read this

[JP]

Here's a page from the AE101 manual that helps to show the stock cooling flow:
http://users.tpg.com.au/adsl0uxv/2_0040.jpg

Jason

[Sam_Q]

thanks, that fills my understanding in a bit more

[blacktop]

Sam and JP you have no f**king idea how much i searched for this info, and i still didn't find it.

+ rep both of you

[Sam_Q]

thanks for the rep, I am curious though what information were you chasing exaclty and why? were you interested in the coolant path?

Bit of a side note I might be boring a hole in the side of my new cylender head to get the plumbing design I want

[blacktop]

I just wanted know the path in which the cooling system followed and what would be the most desirable path for a modified system.

In the end i couldn't find the info i wanted and just ended up blocking the side outlet, re-routing the back of the head and running an external Thermo housing of the pump, its not the way i wanted to do it but i was getting impatient.

JP i would give you Rep but the board won't let me for awhile sorry

[Sam_Q]

sounds like you went down the same road as me, what do you think of my concept that I post on the bottom of the first post?

[thanhngo]

I'm heading down the same path soon as well Sam...

Bore out the water passage (intake side) of head, enough to fit a thermostat. Use a plate so you can mount/seal the thermostat and housing. Might have to drill some holes in the thermostat to allow for bypass? Im just not sure how much space you have back there to work with as this is my first 20v conversion - from pics it looks like MAX 4cm depth?

is that what your thinking as well?

[cooter]

hey sam
i set my 20Vs cooling up a lil diff to your guide. to make things easier i had a front cut to start with. as i was pulling the motor out i checked out the flow paths of the water so i could work out how it was all going to go back together. on the back of the head when you take the thermostat setup off it exposes those 2 ports. i made a plate out of 10mm alum plate (that i cut to shape with a hacksaw) which blocked the exhaust side port but had a hole in it for the inlet side port. then an inch long 30(something)mm id then a 90deg bend/weld and angled 45 down and away from the motor. then i just used the other exhaust outlet for return. as for the sensors i put the water temp one in the alum plate but when i was doing that i forgot about the dash sensor. so that got plumbed into the foot long alum return pipe back to the radiator. turns out thats not the best place to put it. reading skyrocket temps with that position but the microtech says cool. so i gotta put that in the plumbing between the ewp and the themo blockplate.

so my flow path goes:
radiator -- ewp -- water routing plate -- into the inlet water port -- through the head and out the front water port -- round the cast alum bend into the back of the water pump -- water pump impellor blades have been removed -- into the block -- out the exhaust side water port back to radiator.

i dont run any sort of themo stat anymore. i just use the microtech to switch on the ewp at 40deg.
is there any negative in running this setup? its my first engine conversion

cheers
craig

[blacktop]

How long does it take for your ECU to read 40deg?

[Sam_Q]

thanhngo: I am not quite sure what you mean when you say you want to bore a hole when you say to bore out the intake passage to fit a thermostat, would you be able to explain this in detail?

also have you read my cooling guide? (link in my signiture)


cooter: from a highly reliable source I have been told that if you run no thermostat you need to run a restrictor plate to keep the pressure on the cooling system. Otherwsie you may be hot spots around your bores and cause damage. Otherwsie you are running your cooling sytem to standard specifications and therfore you wont have any problems

[cooter]

sam
that restrictor plate would be on the exhaust side outlet hey?
ecu doesnt take to long. after a min of driving its all good.

[Sam_Q]

I am unsure where that would be placed, normally I would say it would be put where your old thermostat would normally sit. However seeing you dont have any thermostat at all thats different.

My real opinion though is that you should run a thermostat, all your parts are made to run at a certain tempreture and only at that tempreture are meant to suit their tollerences.

[thanhngo]

I think the radiator cap regulates the cooling system pressure more so than the thermostat. E.g. 1.1bar, 1.3bar pressure caps etc.

The thermostat is designed more for regulating flow using tempartures (although it may contribute to pressure) as it lets the engine warmup to operating tempatures quicker.

Going back on the topic; Sam_Q: I've read your 20v rwd cooling guide


In reference to this picture/posts; I can understand why it could be beneficial to replicate the 20V oem flow in RWD format (not disputing other methods as they have been proven to work).

One thing I haven't confirmed is how the rear water housing/thermostat works (I don't have that part yet). It looks like to me toyota implemented a bypass-thermostat.

The plan for me is to run two coolant pipes on the intake side. How to handle the thermostat/rear housing seems to be the tricky part. An external thermostat would be the easy way out

[Sam_Q]

I think the advantage of using the original approach instead of my clean cut rwd method is that the intake ports are significantly cooler this way. How much better no-body seems to know

As for the thermostat why not use the 4ac setup like in my guide?