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Thread: Rear Mount Radiator Questions

  1. #1
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    Rear Mount Radiator Questions

    Hey guys,

    I am going to set up a rear mount radiator for my 1UZ AE86 coupe project.

    If you guys know me, shhh it's a secret and keep it off Instagram (@swayton #risingsun #battlecar #100hpoffury) and Facebook. I dont want my East Coast USA peeps to know about my power plant project, so I'm hitting up this Canada forum! I like this forum anyway. <3

    Anyways, the AE86 stock radiator carries about 5.9 QTs of coolant. The 1UZ is used to running 11.6 QTs in the SC400/LS400 system, so this tells me that I should run closer to the 1UZ stock radiator, that's obvious.

    I've done some research, but I dont quite understand the math and science of cooling, especially since we're going to route it to the rear of the car, which means that there will be ADDITIONAL coolant in the lines I'm running under the car from front to back. Does that really affect the cooling system? That means there's more coolant to run, but more pressure to push additional coolant to the back and back to the front. So do I need an upgraded water pump? Will the stock one run ok?

    I have yet to measure my coupe trunk to see if a stock LS400 radiator will fit; I'm hoping to stand it straight up right under the windshield. I plan to create air ducts from the quarter windows and install push fans on the radiator. Partitions will need to be created to protect the driver from any coolant spewing, and coolant lines will run under the car and have skid plates made to cover them.

    I know you guys are really smart, I have been watching the build threads in this forum. Can you guys help me figure all of this out in the most painless way? It already sucks that I have very little time for trial and error, but I don't want to sacrifice a motor or track day because I'm building the car wrong.

    So here are additional questions I'd like to get sorted out:

    What are ideal dimensions I can search for that keeps the car cool and not risk overheating?

    Should I look up 2 core radiators or stick to one?

    Is the radiator position (vertical) ideal, or should I cut a hole in the spare tire bay and mount it horizontally? (Not comfortable with this idea since it's closer to the bumper, more comfortable with radiator between the rear struts)

    How can I sort out the venting? (Thinking of having a mesh or louvered trunk lid)

    It seems that D-Mac has the only drift car with a rear mount radiator that I can find online, but that's for a hatchback with roof scoops, and is not running a 1UZ.

    Reasons for running rear mount radiator:

    - Space in front of the 1UZ is severely limited and cluttered
    - Better weight balance
    - Front crash protection. No busted radiator, keep drifting.
    - It's different, but oh so cool in the cars already running that setup

    More info about me:

    Been drifting AE86s since 2006.

    First AE86 "Sway" with a 4agze installed. Drift career 2006-2009


    Second AE86 "Saika" with a bone stock 188-198k mile 4age. Caged and tandem ready in Spring 2011. Never qualified for a pro comp due to lack of power. Drift career 2010 to 2012. Pro comp build pending for 2013.










    Third AE86 "Riley" a grassroots drift car, taking Saika's stock 4age to continue drifting until Saika can hit pro comps. Build pending, deadline March 20, 2013.



    Sand color bay paint.


    Thanks for anything you guys can offer to help me out! I'm hoping to hit up pro comps and wow the 240-dominant crowd!

  2. #2
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    I personally think rear mount is silly, it causes over rotation because it's more weight in the back and it is a lot of excess materialszszszszs. You wanna tuck your 1uz so close to the firewall you could fit five 3 bar koyo rads up front no issue anyways. If you still wanna be fd spec not d1gp spec consider SS hoses, the only thing I know about building drift cars is copy JDM builds it's 1000% better. ueo doesn't run a silly trunk mount and the excess high mount weight in the trunk is not better weight dis. Although 1uz is the new sr20 so idk what i am talking about....

    also fill the distance for coolant and burp the system not much more you can do besides considering piping location to make the flow easier on the pump which will have to move more water/rad fluid.... venting is key look at that wanker ae86 hatch from irealand, dmac... a 3 bar is bestestest. Trunk mounting is silly because it also adds the problem of water pumps pushing x psi vs speed .i.e size of pipe to x amount of water extra distance to cool before moving back, if your thermostat opens at 170 lets say its gotta fully open and allow a extra x amount of warm water to go to a further distance to cool, that is only vented not forced feed like the front of the car, if your not moving itll overheat more like a porsche. Also your stock thermostat might need to change to encompass the distance to cool. my 5 cents because canada has no more pennies is don't do it, spend the money on hookers and blow. sorry for spelling mistakes i am drunk
    Last edited by LastLatvian; 03-01-2013 at 12:07 AM.

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  3. #3
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    Just my 2 cents but the the guys doing the 1UZ 86's around here are using Be cool Scirocco rads and good E-fans. Plenty of cooling, just cut the rad support and make it fit.

    Having a radiator in the back would be a ton of extra work, more stuff to fail, more areas to leak, etc etc. I think the cons outweigh the pros.

  4. #4
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    Coolant volume shouldn't matter much with a properly sized radiator with sufficient airflow. Essentially, if your radiator can't dissipate enough heat the extra capacity buys you some time as it takes longer for it to get hot. Yes the coolant in the long tubes would contribute to this effective coolant volume. In terms of performance you are better off comparing flow area and the number of rows of fins. (ie single dual triple core), and whether the rad is single or dual pass.

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  5. #5
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    tommy is offline Redneck engineer/machinist
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    Think about the SW20 and AW11... both 3SG and 4AG had the same waterpump as the Corolla and Celica using the same engine mounted in front with the rad compared to the MR2 having the engine in the back and rad at the front with hoses running the length of the car, exactly the opposite of what you're trying to achieve. As long as you have a properly sized rad and a way to get airflow to it you'll be fine.
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  6. #6
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    You're going down the right path. It's something I'm looking to do with my car. It overheats like crazy.


    RETIRED

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    Very Scandanavian
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  8. #8
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    Some things need to be done just to be different. Do it up, and keep it clean. Makes more room up front for an intercooler anyways.

  9. #9
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    Quote Originally Posted by Sparkie View Post
    more room up front for an intercooler anyways.
    Wait.. is this a turbo 1UZ? I would be more inclined to agree with a rear mounted radiator setup if that were the case. Maybe start studying the old JUN impreza driven by Kumakubo?

    PS I wish I made a temporary 4AG ae86 drift car while I build my V8 one.

  10. #10
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    You need to create a positive pressure in the front of the rad and a negative pressure behind the rad. There are a lot of important aspects to cooling other than the rad such as ducting, shrouding, fan choice and location.

    I personally would leave it in the front where there is more air flow and focus more on quality
    of the components and design. There is a lot of room in front of that motor if you are willing to cant the rad, rebuild the rad support and fab a bash bar. The last two cars we did used the scirroco be cool rad but the current one we are doing we are using an even bigger rad.

    We also just found out gates makes a 170 degree thermostat for the 1uz.

    If you like spending money you can have C&R build you a rad fan combo to your specs and it will work like magic.

  11. #11
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    A big reason 1uz corollas or other cars with small bays ans 1UZs overheat is because the whole volume of hte engine bay is fulled with engine. You can have a huge rad, and fan, but if the air can't escape, it can't flow.

    Like billiam said, you need to get negative pressure behind the rad. Drop vent? Louvres?


    What rad do you run Devin?





    ...I think
    Last edited by clay72; 03-03-2013 at 08:32 PM.
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  12. #12
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    Quote Originally Posted by JungleMatic View Post
    You're going down the right path. It's something I'm looking to do with my car. It overheats like crazy.
    I never had even remotly close to overheating, only time I did is when I forgot to turn my fans on(which still got slightly above half way on the guage), But Mine is a big heavy copper rad, might do it in aluminum someday to shave weight...I wouldn't bother with rear mount, too much hassel for little or no gain
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  13. #13
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    Quote Originally Posted by LastLatvian View Post
    . sorry for spelling mistakes i am drunk
    Hahahaha.

  14. #14
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    95% of this thread is wrong. My advice though, is dont try.


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  15. #15
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    I think the advice is pretty good. I'd go for it if it was for a track car and i had time.

    I think the biggest battle will be figuring out where the air is going to come from to go through it. I guess that depends on whether you are going to try to direct air through or just have openings and blow air through with fans. Making sure that the whole system is easy to purge is important.

    Considered an electric water pump? Height of the rad relative to the water pump will have an effect on the ability of the pump.

    Should I look up 2 core radiators or stick to one?
    Do you mean row instead of core or do you mean a dual pass setup?
    Last edited by clay72; 03-09-2013 at 11:00 PM.
    1JZ 1984 Celica GTS
    1UZ 1981 Corolla sedan
    ? 1972 Celica race car

  16. #16
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    1JZ 1984 Celica GTS
    1UZ 1981 Corolla sedan
    ? 1972 Celica race car

  17. #17
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    Quote Originally Posted by clay72 View Post
    I think the advice is pretty good. I'd go for it if it was for a track car and i had time.

    I think the biggest battle will be figuring out where the air is going to come from to go through it. I guess that depends on whether you are going to try to direct air through or just have openings and blow air through with fans. Making sure that the whole system is easy to purge is important.

    Considered an electric water pump? Height of the rad relative to the water pump will have an effect on the ability of the pump.



    Do you mean row instead of core or do you mean a dual pass setup?
    Rad fans become useless with air speed. This is well known in racing. You will have to find a happy medium in a rear rad setup. At about 20kmph, on a well ducted and flowed system, you wont need fans. This is common practice on dedicated race cars. So trying to push through a Fan is counter productive if you design it right. Fans are for Idling. Venting through the trunk lid is a terrible idea to. High pressure zones, under the car is a low pressure zone and common practice. Now having the ability to purge the system as you state, should not even be thought about. You will need a means to Air Lift Fill the system and have a Proper Header tank tied into all troublesome spots and possibly run a swirl pot on cars that see Continious high RPM or have steam pocket issues. Normal filling or bleed points wont work worth a damn. The lower T-stat statments are far from the truth too, especially on a rearmount/front mount system. Thats old hot rodder BS.


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  18. #18
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    THE number one problem I encountered with running the ae86 fan was it didn't have enough flow rate and the water pump would over pressure the top tank and blow out the rad cap. The setup I came up with is a huge 3core 3/4" tube custom brass radiator with scirocco fans. This is the setup dano is running now and works perfectly.
    Owned too many different modified toyotas to list LOL


  19. #19
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    Rad fans become useless with air speed.
    I am assuming this car will stop from time to time, be in line, etc, and he will also want to warm it up to operating temp before thrashing it.

    Now having the ability to purge the system as you state, should not even be thought about. You will need a means to Air Lift Fill the system and have a Proper Header tank tied into all troublesome spots and possibly run a swirl pot on cars that see Continious high RPM or have steam pocket issues. Normal filling or bleed points wont work worth a damn.
    I'm not following here. I guess you figure having the ability to purge it and to have a header tank are 2 different things? Is a header tank not a means of purging?

    All in all it sounds like a pain in the ass but i would like to see someone do it and work out all the bugs. Someone who is not me. I have a 3 row fox body mustang aluminum rad and will have a big pusher on it because its a street car.
    1JZ 1984 Celica GTS
    1UZ 1981 Corolla sedan
    ? 1972 Celica race car

  20. #20
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    It is common practice in high performance to run a cross flow radiator with the rad cap on the lower rad hose side. Helps keep the rad cap from lifting by having the cooler temp under it as well as not being on the out put side of the water pump pushing against it.

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