Air/Water aftercooler decision and parts

Car in question is my TDI swapped W116

This car has a relatively small grill area and not much room to snake boost piping around the sides of the radiator without 1) running a narrower radiator or 2) cutting the body work(which I would rather not). I'm not against running a narrower radiator if Air/Air is that much better of an idea, but I was thinking a bigger radiator is better in an endurance race car. However most people seem to point towards Air/Air for endurance race cars. Another data point is this engine is non-crossflow so for an Air/Air setup the core would make sense to be in/out from the same end.

All this has me thinking it may be better to set up an Air/Water aftercooler. I could have very little boost piping and a simple intake system. Then I would need to add a pump, tank and heat exchanger. I am mostly thinking about the positives, mostly packaging. Photo below of a TDI with A/W. Thoughts of the hive?

I am a large fan of water/air vs air/air for plumbing and heatsoak reasons.  In an endurance environment the heatsoak problem goes away, leaving you with trading off additional weight and things to go wrong with not having to snake large diameter plumbing to the front of the car.  Which is why the go to is air/air.

My gut instinct, which may be full of E36 M3, is that if you are keeping boost below 9psi or so then just run without an intercooler.  It is not like you will run into detonation issues, right?

I have a decent tune on this thing and want to keep it alive. Tuner says around 20psi

Are you required to use pump fuel?  Since E85 is sold at gas pumps it's legal.  
     Plus no  intercooler required!!!! 85% ethanol will drop charge air temps from 200+ to under 100.  
     If you buy it in 55 gallon drums. ( they also sell it in 5 gallon cans)   They mix 15% race fuel with 85% ethanol.  Gas station pumps vary from 55% to 83% ethanol.  Depending on the season.  Plus the Gas isn't very high grade.     
  The good thing about that is you'll pick up 15-20% more power as a result.   The engine will love it.   Flame front on alcohol is softer than the flame front  on gasoline.  
   Yes you will need to richen the mixture. For driving on the street  15-20% more fuel is required. Plus a slight timing advance.    Racing can increase needs to 40.%. 
     The one thing about E 85  is it's less sensitive to going too lean or too rich. Alcohol is extremely tolerant.   
   A Little history.  Indy cars ran on alcohol and  they had as much as 85 psi boost pressure for the race with up to 120 PSI for qualifying.  Making as much as 1200 horsepower!!   No intercooler!!  None!!!  

Diesel frenchy.

In reply to buzzboy :

Oops! Sorry. 
  I'd use air to air still.  Water/ air will require some way to drop the water temp in an endurance race.  Drag racing they put fresh ice in  or just add dry ice as it's used up.  
  You don't see water used in endurance racing.  

frenchyd said:

In reply to buzzboy :

Oops! Sorry. 
  I'd use air to air still.  Water/ air will require some way to drop the water temp in an endurance race.  Drag racing they put fresh ice in  or just add dry ice as it's used up.  
  You don't see water used in endurance racing.  

Some Group A rally cars did.

If you are running for more than a few seconds at a time, you use a radiator for the water.

A LOT of manufacturers use water/air in their street cars now.  Not just supercharged applications, there are quite a few modern turbo engines that use it too.  Some Fords even stick the unit right in the intake manifold plenum.

In reply to Pete. (l33t FS) :

They were using the water from the radiator to cool it.  That needs a really big radiator.  The OP doesn't have that room or he doesn't want to cut holes  to allow the tubes.  

I don't have room to run two 2.5" charge pipes. I can snake two water lines through my body work much easier. Then I only add a little thickness to my cooling stack with a heat exchange.r.

Could you fit an Air to Air in the wheelwell behind the bumper? (I've been working a lot on my son's Audi TT so I've spent a good deal of time seeing one lately.) I do like the simplicity of the intake with the A2W but the endurance racing aspect means you should definitely build a robust system and source a high quality electric pump. 

I had a A/W on my om617 with a vgt turbo. 

frenchyd said:

In reply to Pete. (l33t FS) :

They were using the water from the radiator to cool it.  That needs a really big radiator.  The OP doesn't have that room or he doesn't want to cut holes  to allow the tubes.  

Every water/air intercooler setup I have seen had a separate radiator for the charge cooler.  They may use the same "coolant" but only at the top of the system to ensure it never runs low, they are effectively two separate coolant loops.  The intercooler radiator/radiators are usually in a wheelwell, but sometimes parked out front of the rest of the cooling stack.

That did throw me for a loop at first on the 1.5 Ecoboost Fusions, as there is no second coolant reservoir, but while they share the same coolant they do not cross-circulate.  Audis are the same way, and I think Mercedes as well.

Can we stop with the dry ice idea, it's a really bad idea. First, dry ice has a much lower specific heat than ice, then when it does melt, gas CO2 doesn't transfer heat as well as liquid water. Third, the sublimation will blow apart any closed system with the pressure increase. Given drag runs, you will quickly melt the CO2 making the lower temp useless. 
 

Use salt really cold, use salt; like you do when making home made ice cream.   That will lower the temp of the water and still keep thr specific heat. 

In reply to alfadriver :

Dry ice IS, or was, used for drag racing setups.   In acetone, which has a freezing point below that of dry ice, so it doesn't sublimate as much as it could.  The acetone circulates through the intercooler and the dry ice just hangs out in the reservoir, cooling the acetone.

I would imagine that an adequate tank vent is used, but that's the entirety of my knowledge about its use in charge cooling.  I can't see how they could make the acetone tank spillproof while also venting the CO2.  Given that I only heard about people doing this about 20-30 years ago, maybe they stopped doing it for this reason

I expect that methanol injection is more popular now.  People used to run turbos on blow through carburetors (methanol fuel) and find that the intake manifolds were iced over after a 40psi boost run.

Regarding the OP's conundrum, as much as I like water/air, I like it for reasons irrelevant to the problem at hand, so air/air would make the most sense.   Because I like to overcomplicate things, I wonder how much it'd be worthwhile to run a BIG intercooler up front and move the radiator elsewhere, and what the race series rules have to say about that...

I have the stock B5.5 Passat side mount aftercooler but the plastic end tanks use OEM specific connections that I can't adapt to regular piping. And I would like more cooling capacity than that.

Moving the radiator is an interesting idea. Huge front mount would give me heckin low IATs and a cooler engine bay but then I've got a lot of work ahead of me moving the radiator. So, practical? Maybe not, but an interesting idea. Lemons doesn't care as long as I don't have a coolant pipe in the cabin with me.

Depending on the length of the race water injection may be easier than running an intercooler, or can be combined with one for maximum cooling.  Many oems are going air to water now for easy packaging.

Do any of the upgrades for the Hondas with 1/2 width radiators work for a side by side intercooler/radiator setup?

Edit: the merc is wiiiide-maybe a normal car sized radiator and a narrow intercooler up/down on the intake side  1/3 of the radiator.

In reply to Pete. (l33t FS) :

Interesting, at least it's supplying a fire suppressant with the very flammable acetone. 
 

Still, the specific heat of both isn't water. 

MrJoshua said:

Do any of the upgrades for the Hondas with 1/2 width radiators work for a side by side intercooler/radiator setup?

 

Edit: the merc is wiiiide-maybe a normal car sized radiator and a narrow intercooler up/down on the intake side  1/3 of the radiator.

The benz is a wide boy, but the radiator opening is quite narrow comparatively at 27"

I was wondering about the narrow honda radiators. I guess radiators care more about HP than anything, right? So if the radiator is good for a 175HP Honda B series then it should be good with a 175HP TDI?

MKIV Supras ran sidemount intercoolers like this:

This was the setup on my 240d:

I have room for a half Honda radiator and an Air/Air front mount mounted next to each other in the grill area. 

So my question now: is radiator sizing based on HP? Find one for a high HP Honda

I had an air to water intercooler on my supercharged AW11 MR2 track toy and always struggled with heatsoak issues after 10 minutes on track.  I used a mustang Cobra front radiator, separate cooling system, frozen boost intercooler and a big Bosch pump. My issue may have been air in the system which was complicated by the rear engine setup. In any event, I'd package even a small air to air before I'd go air to water again.

buzzboy said:

I have room for a half Honda radiator and an Air/Air front mount mounted next to each other in the grill area. 

So my question now: is radiator sizing based on HP? Find one for a high HP Honda

The typical radiator is too small for racing in an enduro. Unless driven at a percentage of power  80%?   That last bit of power really tends to add a lot of heat. 

Whenever you need to get a lot of cooling from a small radiator area, add rows and passes. 2-row 1-pass is better than the common 1-row 1-pass, but the best setup you're likely to be able to fit is the 3-row 3-pass. In this kind of radiator, the liquid goes through the back row, then the middle, then the front, so by the time it gets to the front row it's had a lot of cooling already and has the coolest air doing the last bit of work, it's very efficient. A 3-row 3-pass half-width (AKA "Civic-size") radiator will cool better than a full-width 2-row 1-pass. The inlet and outlet locations will have some effect on how many passes you can fit though.

Next, know how to stack your radiators (of various types) from coolest to hottest to get the most cooling out of the smallest area. Intercooler or AC condenser should go first, depending on your priorities, then engine coolant radiator, then engine oil/trans/PS fluid coolers. Keep in mind that the most efficient setup may not make the most sense for a particular use - if certain systems overheat more easily you may want to throw efficiency under the bus to boost cooling power where it's needed.

Third, consider V-mounting - if you have the longitudinal space, this can let you put more radiators in parallel in a smaller frontal area, and parallel airflow is always better for cooling.

I don't have the area for V mounting, but I've drawn my two ideas. I found 3 row Honda radiators and I like the idea of that setup. Also puts the outlets in favorable places.

Then a scirocco radiator would take up about 20" of my 27" width and give room to route charge air pipes in front of it, through my current radiator hole.