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air to water intercooler?

19K views 21 replies 9 participants last post by  Ruso 
#1 ·
If there was ever a car set up perfect for an air to water intercooler setup it would be the WRX. You can put the intercooler itself as a direct replacement for the stock TMIC, and put the heat exchanger in front of the radiator where it gets great airflow.

Has anyone done this and I just missed it in my search?

Keith
 
#5 ·
stileguy said:
yeah, subaru did it from 1989-1994, its called a legacy rs turbo
Thanks for that heads up. Why did they go to an air to air TMIC? Less expensive, or were there problems with the air to water setup?

Keith
 
#6 ·
Fourdoor said:
Thanks for that heads up. Why did they go to an air to air TMIC? Less expensive, or were there problems with the air to water setup?

Keith
Both probably. Plus, those factory air-water intercoolers weren't very efficient. I do know a couple people running air-water intercoolers in their street cars with no problems. Neither are on a Subaru though.

But, if you do it right, it should be fine.

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#7 ·
Weight was also a factor. The reason Subaru stuck with air to air TMIC is because air to air with a water sprayer was just as effecient as the water to air, and lighter. I have a writeup somewhere in my room about it.
 
#8 ·
Vew said:
Weight was also a factor. The reason Subaru stuck with air to air TMIC is because air to air with a water sprayer was just as effecient as the water to air, and lighter. I have a writeup somewhere in my room about it.
If I did a setup like this it would probably have more expensive heat exchangers than a factory setup, probably around the efficiency of a good FMIC setup during normal street use. Also I would have a surge where I could drain the system and re-fill it with Ice and water for track use.

I am not doing this any time soon, just looking at possibilities for the future.

Keith
 
#9 ·
stileguy said:
yeah, subaru did it from 1989-1994, its called a legacy rs turbo
Did some google searches and the only thing I found was the twin turbo lagacy's. Do you have any links that show how the air to water IC was set up on them?

Thanks,

Keith
 
#10 ·
The heat exchanger was placed in an identical fashion to the wrx top mount, same turbo to intercooler piping and intercooler to intake pipe setup. the heat exchanger has a radiator cap on it to add your liquid (demineralised water and water wetter works best). this liquid is piped to a pump in the front left fender then to a front radiator where it is sent back to the heat exchanger, the pump was controlled by a relay on the left strut tower. it had 2 speeds, low speed at light throttle to ensure liquid spent as long as possible in the front radiator and high speed to get the liquid out of the heat exchanger under full throttle, MRT did an upgrde to the size of the front radiator which gave 40% more cooling and worked better at removing heat from the intake than most top mount intercoolers but did not flow enough air.
in the late 90s guys here in oz enclosed the stock top mount intercooler in aluminium plate and made it into a water air setup with great results but nothing compares in terms of heat dissipation and airflow volume to a quality 3' thick front mount. with the cost of intercoolers being so low it is a waste of money to go to the trouble to spend more money and more complex setup just to save 200rpm in lag. there is a reason why nearly all fast subarus have front mounts. it has been proven again and again, if you keep your pipe sizes sensible and dont go overboard with core size a fmic is hard to beat. you do not need 3' pipes and a 600x300x90mm core until you start looking above 600hp.
 
#11 ·
stileguy said:
The heat exchanger was placed in an identical fashion to the wrx top mount, same turbo to intercooler piping and intercooler to intake pipe setup. the heat exchanger has a radiator cap on it to add your liquid (demineralised water and water wetter works best). this liquid is piped to a pump in the front left fender then to a front radiator where it is sent back to the heat exchanger, the pump was controlled by a relay on the left strut tower. it had 2 speeds, low speed at light throttle to ensure liquid spent as long as possible in the front radiator and high speed to get the liquid out of the heat exchanger under full throttle, MRT did an upgrde to the size of the front radiator which gave 40% more cooling and worked better at removing heat from the intake than most top mount intercoolers but did not flow enough air.
in the late 90s guys here in oz enclosed the stock top mount intercooler in aluminium plate and made it into a water air setup with great results but nothing compares in terms of heat dissipation and airflow volume to a quality 3' thick front mount. with the cost of intercoolers being so low it is a waste of money to go to the trouble to spend more money and more complex setup just to save 200rpm in lag. there is a reason why nearly all fast subarus have front mounts. it has been proven again and again, if you keep your pipe sizes sensible and dont go overboard with core size a fmic is hard to beat. you do not need 3' pipes and a 600x300x90mm core until you start looking above 600hp.

Great explanation! Thanks !Thumbs Up I didn't realize the difference in lag was so small or I would not of even brought up the subject.

I have seen poeple explain the reason the stock TMIC has two inlets to be because it distributes air flow better. My view is that it was set up for the twin turbo subaru's (one turbo's outlet going to each TMIC inlet) and they just used the same TMIC on the single turbo cars to save money. Is my speculation correct?

Keith
 
#12 ·
subaru australia never imported the twin turbo legacy to oz and much better results are achieved from doing conversions with the cheaper single turbo setups (wrx, legacy rs) the biggest problems is with the sequential operation and getting the transition seemless, most people hunting for more than 320hp just installed the manifolds from the single turbo cars. i have never really looked at the plumbing on a GT so i dont really know. in NZ there have been reports of GTs grossly overboosting when high flow exhausts are installed and resulting in engine destruction as the backpressure in the exhaust seems to aid the transition of the turbos. They start off low in the revs with only 1 little IHI RHB4 turbo spooling at 2300 and the second RHB4 opening (via exhaust manifold flapper) at approx 3500-4000, the exhaust manifolds are merged into one before the turbos. if they were simultaneous setup a swap to a pair of TD04Ls would be a sweet setup but subaru wanted strong torque from just off idle to redline so they went for sequential.
 
#16 ·
Hello everyone, I just finished my WAIC setup. I saw this post in doing research and wanted to share the build.

In my case it's a custom fabrication of universal components. The WAIC itself is HUGE and flows a lot of air and barely fits in the engine bay (Had to relocate hoses and bend back the tab on the firewall to make it fit).

The purpose was to do a budget build and even though it took several days of non-stop fabrication, I ended up with a rebuilt VF-39 AND the entire WAIC setup for less than the price of a half decent TMIC.

You can read a blog article about the entire build here: Turbo Upgrade and Fabrication on the WRX ? Dmitri's Gallery

Here's a couple pictures:
Engine Bay with Water to Air Intercooler


Front Mount Heat Exchanger


The final Intercooler Unit with my custom sticker and all fabrications finished


The water does not get much warmer than the outside temp and it's always cold to the touch even after repeated tuning runs. I think properly designing the system makes it well worth it.

Now to fix that damn ram intake that pulls hot air in to further improve cooling of intake air.
 
#17 ·
look good man nice work! i would love a closer of pic of how it connects to the throttle body if you dont mind :)

you got any plot graphs? i'm really interested in your spool rate with an intake path that short.
 
#18 ·
Thanks titter!

It connects via the stock silicone hose that went to the TMIC. The one difference is that the hose had soft silicone ends (they sort of wrap around the end) but because of that poor design choice I have blown the hose off the throttle body several times. I took those off the hose (they are lightly attached probably just by heat over time).

As far as spool goes, I just started tuning last night so no graphs yet. I am very baffled by the results but I managed to overboost at 18+ psi at 3200 but I think that was an anomaly. After I tune that out I suspect full boost right around or just below 3500.

That said I'm very confused because the VF39 is not behaving that much different than my old TD-04... it did at first before I tweaked boost (it took a while to spool) but now I hear it start spinning at around 2k and pulling strong right at 3500 with peak power right around 4400.

What I really wanna know is the intake air temperature versus air temperature after the unit. I've touched it after wide open pulls and it never gets any warmer (neither the intercooler or the heat exchanger.
 

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#19 ·
Here's a boost graph one of the last times I logged last night but I ran out of time so as you can see there's still a ton of work to do to smooth out the boost. I did manage to level out that peak to safer levels but it's still far from perfect.

My issue is that I live in the mountains and elevation changes rapidly when tuning so it's very unexpected and hard to tune for. I can overboost and then one mile down the road not hit target boost.

I'm definitely still learning to tune, but gladly with tamed boost I know it's safe since there's no knock at all. I plan on building an EWG setup with a dump tube as a last series of power mods and will pay for an opensource pro tune at that point if I still can't dial it in perfectly.
 

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#21 ·
One last update from me for now. I finally got around to building a cold air box for my DIY Ram Intake. I'll be posting a how-to article at some point in the near future.

Intake temps dropped like night and day. I'm very pleased with this mod making the WAIC system complete (minus the ghetto resevoir mounting system I have now). :D
 

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#22 ·
I'm still working out the kinks in the system. I built a new RAM intake because my original (just reducing tube with a MAF cutout) was turbulent at low RPM so it was no fun parking and reversing (not to mention impossible to tune the sensor scale). The MAF was mounted too close to where the reducing section of the pipe is.

I built a new one where the tube is slightly longer and the reducing section is right at the filter. I also added two vertical plates inside (similar to stock air box) before the MAF to even out the air flow. I have fixed all the low RPM issues and was able to tune the MAF scaling without any issues.

So I'm getting the boost dialed in. It looks like I'll be having target boost at right below 3400 RPMs. One of the first road dyno runs yielded 285 WHP with just under 300 TQ (but that had the slight overboost). Obviously this number is not exact since it's not a real dyno (and I'm at weird elevations). This is also without attempting to advance timing (I will start doing that when the boost is completely dialed in).

Here's current boost. I'm slightly under at a few of the RPM cells but I'm right about to hit target with a couple more runs and since there's no wild spikes or creeps, I should be able to have turbo dynamics keep it there in all conditions.
 

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