Rear heater core for liquid to air inter-cooler 1hd-t hdj81 (1 Viewer)

[badQtip]

Hey, I'm currently doing a little over haul on the 1hd-t, MAMBA turbo, custom exhaust and fuel pin blah blah ect... but I had a thought for the liquid to air inter cooler heat exchanger. Since I have the rear heater disconnected and everything is still there and was working fine when i deleted it. Has anyone thought of using the rear heater for their liquid to air inter cooler?

Other then putting heat into the cabin i can't think of a reason not to use it. factory blower, switch, wiring and piping, would obviously need to add a reservoir and a pump to the mix but how inefficient could it be?

 

[Loober]

W2A intercoolers are inherently much less efficient then air to air for these purposes. The volume of water needs to be really large for it to dissipate heat faster then the engine heats it, which what you are describing is def not big enough. What will happen is the system will get heat soaked really quickly and then it will be pretty much useless. If you are going to add an intercooler go with a front mount A2A, plenty of good kits out there, don't waste time and money with anything else.

 

[Feistl]

While I agree the rear heater just isn’t big enough and won’t cool the water down fast enough, I disagree that water to air isn’t suitable.

However for it to work properly you need a big radiator at the front and should be running 1” hose throughout. I’d also be aiming for a ~10L + resivour for best performance... pretty much any w2a system using 5/8” sized hose isn’t going to work that well...

But a typical radiator will have a greater surface area for incoming air compared to a air/air cooler, so done right you will actually get greater performance from water to air.

 

[badQtip]

While I agree the rear heater just isn’t big enough and won’t cool the water down fast enough, I disagree that water to air isn’t suitable.

However for it to work properly you need a big radiator at the front and should be running 1” hose throughout. I’d also be aiming for a ~10L + resivour for best performance... pretty much any w2a system using 5/8” sized hose isn’t going to work that well...

But a typical radiator will have a greater surface area for incoming air compared to a air/air cooler, so done right you will actually get greater performance from water to air.

Yeah I did think it was to small to efficiently remove the heat, I didn’t even think about the line size! Water to air is the route I’m take with this build and I was aiming for a 3-4 gallon system system so thats right inline with your advice.

Thanks for the pointers!

 

[KiwiDingo]

Yep, a properly size W2A system will always beat an A2A for efficiency. Trouble is most systems I see aren't properly sized which gives W2A systems a bit of a bad wrap and where I think the false information about A2A being more efficient comes from. Great work and idea @Bobby Williams I enjoy seeing people think outside the box

 

[bjowett]

Here is the front heat exchanger core from a Lexus NX 200T. Looks like a nice fit for an 80... Toyota has a few different cores, pumps, and reservoirs, for their Turbo and Inverter cooling systems, that might make for a good system.

 

[gerg]

if Your air/ water coolant rad was 100% efficient your air water inter cooler set up would just reach the overall efficiency of an air to air set up. You can’t beat the math boys.

 

[KiwiDingo]

The math clearly shows water is the winner over air

 

[Loober]

Couldn't an argument be made that W2W is more efficient only if the proper sized components are used such as a large radiator core, large tubing, large xchanger. Essentially rendering it unfeasible in the subject application, therefore the W2W setup that can be made to work will be less efficient then A2A because of the limitations in packaging. Whereas A2A is more efficient within the constraints of where it is being installed?

 

[gerg]

Dollar for dollar putting the same effort into each set up air to air will yield a better outcome. The water to air set up will always be less efficient because you deal with the water intercooler efficiency as well as its radiator efficiency. So for arguments lets say the cooler is 85% efficient and the radiator is 85% efficient which is extremely generous. .85x.85 is only 72% overall which is a mediocre air air cooler efficiency. If you put the same effort into each system mathematically the air air always wins. Go all out and design an amazing ground breaking air/water and I can do a better more efficient air air that is less complex and cost less. Air water really only makes sense in two situations. Where an air to air won’t fit and in a boat. Now people have built great set ups that are “sized properly” and I highly encourage you to oversize your radiator as it is really the limiting factor. You can have great results. In the end though it is a harder way to achieve the same goal.

 

[Feistl]

The fundamental part you are missing with your efficiency numbers is an air to air intercooler uses half the physical space in the cross flow fins for the compressed air.... so say you had a intercooler that was 100sq inches, only 50 sq inches would be for fins for actual cooling to the outside air. The other 50 sq inches of space would be used for the cross flowing compressed air.

Now in a radiator the cross flow water fins are considerable smaller, so depending on the design in the same 100 sq inches of space you might have 80 sq inches of cooling with 20 sq inches used for cross flow water.

So if you have 85% efficiency at the radiator and the intercooler you have 80sq inches * 85% * 85% is effectively say 57 square inches of cooling compared to 50 for air to air.

Secondly, even if you do say air to air is more efficient, unless you are running under constant boost and load for like 10 minutes plus (very unlikely) then water has an advantage in the amount of heat it can store.

So say you drive hard for 2 minutes up a long hill, with enough water capacity in the system you won’t have time to heat it up enough to become less efficient. It takes a LOT of energy to heat water up by 1 degree, which is why it’s critical to have a large enough reservoir (which is why I said 10+ litres if possible).

So once you get over the hill when you are coasting you are cooling the water down both by the front radiator AND by heating the air going into the engine.

So even if you do have a lower AVERAGE temperature with air/air, you generally have a lower PEAK temperature with water. And it’s the high peak intake temp under high load where you break things.

So yes, dollar for dollar air to air is better, a GOOD water setup will cost you $1000+.... but considering what some people are prepared to spend on their engines (and turbo etc) then I don’t think $1000 is unreasonable.

Add to that, water inter coolers are better suited to off roading (especially sand) where engine load is high and road speed/air speed is low.

The downsides to a water setup is weight, but for a 2ton vehicle and extra 10-20kg isn’t that big a deal.

So yeah, again a PROPERLY designed water system can be better (or at least as good as) air to air.

 

[KiwiDingo]

Dollar for dollar putting the same effort into each set up air to air will yield a better outcome.

Ahh I see, you have to put a handicap on the W2A for the comparison to a dollar and effort value as the only way to make A2A come out on top

 

[gerg]

No, there is no problem with my math. Go ahead and make the ultimate air water intercooler set up. Do post up your results though. I’m interested to see a “proper” air water intercooler set up looks like.

 

[gerg]

Equal is no handicap

 

[GTSSportCoupe]

I have an air/water system and love it. It's over sized for the displacement of my engine though. I've never measured the efficiency, but it seems pretty good. It literally dropped my EGT's so much when I installed it I thought I'd wrecked my Pyrometer somehow. Pipe into heat exchanger at engine can be far to hot to touch, pipe out is just a bit warmer than ambient..

I agree though that an air/air system can be more efficient. Two imperfect heat exchangers will be cumulatively worse than one imperfect heat exchanger. That part is math no doubt about it.

But, there are definite advantages to an air/water system. Namely the huge thermal mass. When there is minimal air flowing through an air/air, everything heat soaks right away because of the low thermal mass. That's where the air/water systems shine. When your vehicle is stopped and there is little airflow through the air/water rad at the front, the air/water exchanger at the motor still keeps the air flowing into the motor cool, because the water is still cool. It sort of 'filters' out the inconsistent air flow at the front of the vehicle. So in stop/go traffic, it is beneficial. Or quick acceleration (drag racing for example) where there is no time for the system to heat up the water significantly.

On the flip side, if you let an air/water system get heat soaked (through poor design essentially), you're screwed, as it takes forever to cool it back down again. I had to add a couple of 10" fans to the front of my air/water radiator to prevent this heat soak from occurring in 35C summer weather when I'm stuck in rush hour for 45min before towing up an 8% grade heading out camping on a Friday.

All that said. I probably would have gone Air/Air if I could have, just for the sake of fewer parts, less expense and less to go wrong. But couldn't fit Air/Air. So that's another advantage in some cases for Air/Water. It can be made to fit in different ways from Air/Air.

 

[gerg]

Good to hear Nick but with mechanical fan up front a fmic never heat soaks. It gets large amounts of air pulled through it all the time. Top mounts like to soak though.

 

[franklin40]

one more potential disadvantage with air to air is turbo lag is worse than with air to water because of the volume in the piping. water to air can be done with much less volume to pressurize. i’ve been happy with my water to air but i too didn’t have the room to do air to air

to the OPs original question though i agree the heater is too small but very cool thinking outside the box!! i like how you think!

 

[KiwiDingo]

one more potential disadvantage with air to air is turbo lag is worse than with air to water because of the volume in the piping. water to air can be done with much less volume to pressurize.

I've experienced this first hand after removing my large PDI front mount cooler and stuck the factory cross over pipe back in. The difference in throttle response and drivability I gained after it was removed was enough to make me never want to put it back in. There was a number of other issues I had with that PDI cooler kit and after seeing how the car drove without it I ended up selling it and went another route.

 

[GTSSportCoupe]

Good to hear Nick but with mechanical fan up front a fmic never heat soaks. It gets large amounts of air pulled through it all the time. Top mounts like to soak though.

To get the air flow you speak of you need to be idling high and have the intercooler sealed to the radiator (as the rad is sealed to the fan shroud). Elec fans directly on the intercooler are a better option.

 

[gerg]

Yeah more volume is definitely better. But I’ve found the mechanical fans do move a ton of air even at idle. Sealing up gaps that open up around the rad and bezel in these old trucks will help all aspects of cooling mind you. Yours was mechanical fan and you added an electric? Which fan did you use? I know spal makes good fans but they are a bit pricey.