Intercoolers and Hood Scoops - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• Intercoolers and Hood Scoops by 2mn2 on 03 Jun, 2004 11:50
• Has anyone ever used a hood scoop to direct fresh air to the intercooler on a VW?
  
  IC placement before the radiator compromises radiator function and placement after the radiator compromises the IC function.
  
  Any thoughts on this?
  
  
  m alexander
• #1 by VWRacer on 03 Jun, 2004 12:08
• I think it's fair to say that everything about ICs is a compromise.
  
  Hood scoop ICs certainly have their share of compromises. The principle limitation to them is that by their very nature hood scoops force the air to go down while picking up heat. It can be done, but it violates basic physics principles and so necessarily is less efficient than the same size IC can be when employed in a better orientation.
  
  Placing the IC in front of the radiator is almost always the most efficient and effective placement. Keep in mind that a radiator is designed to provide adequate heat transfer under the most unfavorable circumstances -- high ambient temperature, engine running with a/c full on. Once the car is rolling any radiator in good shape has far more than enough cooling capacity to absorb the extra couple of horsepower represented by the hot air going through an IC placed in front of it.
  
  Another effective plan can be to place the IC in one of the fenders, ala the modern VW TDi. The biggest limitation of this approach is the small size of the IC that can fit there compared to a FMIC.
  
  Hope that helps!
• #2 by BlackTieTD on 03 Jun, 2004 12:10
• my thoughts are that having the intercooler above a hot engine would compromise its function more than behind the radiator.
  
  are you having problems with cooling that you need to address? otherwise, you shouldn't be too concerned with putting the IC before the rad as most people do. there is also a free space on the passenger side of the radiator, you could mount the IC mostly in that free space which will leave more surface area on the rad open.
  
  have fun  
• #3 by Dropout on 03 Jun, 2004 12:47
• Something that has always stuck in the back of my mind is to try and use the cold high pressure air at the base of the windshield for this. The only problem that I can see is how to vent the air after it's passed through the intercooler.
  
  One possibility is to punch two holes in the firewall and lay a long thin intercooler in the tray at the base of the windshield. You'd have to make sure that the wipers don't hit it though. The intercooler could be nothing more than a few lengths of finned tubing available from just about anywhere. You could vent the hot air out through grilles at the bottom of the fenders.
  
  Dropout
• #4 by BlackTieTD on 03 Jun, 2004 12:54
• thought about that too..
  
  if you want efficiency, the rain tray idea won't be as good as a simple front mount. so much surface area and the wind is just howling across the full diameter.
  
  i'm considering a cooler in the raintray though, but an air/water setup.
• #5 by Hammy on 03 Jun, 2004 15:00
• Is there concerns in dealing with bends, and overall length of intercooler tubing?(losses?)
• #6 by fatmobile on 03 Jun, 2004 23:20
• I thought the air pressure at the base of the winshield was quite low. Especially compared to the pressure at the front of the vehicle.
• #7 by Dropout on 04 Jun, 2004 05:46
• Think of the cowl induction hood scoops on the Corvettes and Chevelles.
• #8 by BlackTieTD on 04 Jun, 2004 06:35
• Quote

  Think of the cowl induction hood scoops on the Corvettes and Chevelles.

  
  
  yep, i am aware of this type of air intake, my next door neighbour and good friend has a trans am with a 455 olds engine making 500+ft/Ibs, cowl induction.  :twisted:
  
  the pressure and the amount of air that will be forced through the fins of an intercooler will no doubt be higher at the front of a vehicle... not to mention that with the IC in the front, the air moves through it on its own, its physics. with the IC on top of the engine with a scoop or cowl induction or whatever you want, you're asking the air to take a sharp turn downward. there will be losses in efficiency there.
  
  i'd really like to see some concrete numbers on all of this..
• #9 by 2mn2 on 07 Jun, 2004 10:26
• Thanks to all that replied to this thread.
  
  I live in the cental valley of California. Summertime temps
  are regularly over 100° F. A/C is a neccessity.  In my old rabbit
  with fresh engine and radiator, it was possible to run the coolant temp into the danger on a long grade on a hot day. (think the grapevine or
  tehatchapi). I always cut the A/C off on long grades. A friend with an
  80, did the same thing.
   
  The cooling system is fine for mellow conditons but
  is marginal in severe heat. I am putting an AAZ engine into this car.
  This is why I do not want to put the IC in front of the radiator.
  
  With a base of windshield installation, the rain tray would have to be
  cut. The rain tray looks like it provides rigidity to the body so
  cutting it is out. Also, the air is this area is very turbulent due to
  the air being thrown up by the front end of the car. It may well be a
  low pressure area.
  
  I think a hood scoop with baffling and ducting would get the job done.
  
  Discuss
  
  
  m alexander
• #10 by BlackTieTD on 07 Jun, 2004 11:40
• don't forget that the top-mount hood scoup location will heat soak that intercooler fairly quickly and lower its efficiency, especially on those really hot days and on city streets. on the highway, constantly moving, wouldn't heatsoak it badly, if at all, if done correctly.
• #11 by fspGTD on 07 Jun, 2004 11:59
• I think you will find that adding the intercooler will actually augment your usual water cooling system, in that it helps get rid of heat that would otherwise be present in the engine.  As long as you don't up the fuel to take advantage of the additional air density it provides and then use that extra fuel that was added to power WOT up the mountain pass, you will find your engine to run cooler with the intercooler.  The cooling that the intercooler assists the normal cooling system with will be greater the higher the post-compressor air temps - so that is particularly with high boost pressures.  By the way with a highly efficient turbo and intercooler, running more boost pressure will also help with engine cooling!  The way it works is the extra mass of air going through the engine helps remove the heat better.  That is, assuming a fixed rate of fuel quantity being injected.
  
  You might want to try a fresh radiator too.  Old ones can get pretty crudded up and I'm sure that hurts their efficiency!  And make sure your thermostat is opening fully (maybe test it in boiling water.)
  
  You should upgrade to the super-size 2-speed turbo-diesel/diesel automatic radiator fan if you don't already have it.  It's the one with the really big fan motor and 3 blades on the fan that have the larger diameter, and the largr diameter fan shroud.  I have an extra TD fan & shroud for an A1, if that might be useful to you let me know and I'll make you a deal!
• #12 by 2mn2 on 07 Jun, 2004 16:10
• Quote from: "fspGTD"

  
  
  You should upgrade to the super-size 2-speed turbo-diesel/diesel automatic radiator fan if you don't already have it.  It's the one with the really big fan motor and 3 blades on the fan that have the larger diameter, and the largr diameter fan shroud.  I have an extra TD fan & shroud for an A1, if that might be useful to you let me know and I'll make you a deal!

  
  
  Jake
  
  Make me a deal!
  
  m alexander
• #13 by fspGTD on 07 Jun, 2004 19:44
• Let me check out my supplies and see what I have... I know I have the TD shroud/fan/motor assembly (with a wiring plug in the motor, wires cut with pigtails that could be wired to your existing single-speed wiring harness and switch), but you might also want also want the other stuff that goes with it to make it a 2-speed setup: there is a 3-terminal fan switch, and a special wiring harness with a relay that is for the high fan speed.  I need to look and see if I have a spare wiring harness/relay, that is the only quesion mark I have at the moment.  I do have a 3-terminal fan swtich that is a good used one, but it will only work for you if you are using the stock-temperature thermostat.  If you are running a cooler than stock thermostat, this fan switch would be too hot for you.  Let me know on the thermostat question.  I will get back to you soon on the wiring harness.