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    Thread: The Rabbit TDI Project Part 8: Intercooler and Pipework

    1. 05-20-2003 11:28 AM #1
      The Rabbit TDI Project
      Part 8: Intercooler and Pipework

      Or: do it once, do it right

      The TDI engine is intercooled.
      For those that don't know, air is heated as it is compressed. Intercoolers are
      used to remove heat from the charge air to allow the charge air to increase in
      density so you have more combustion air entering the combustion chamber.

      More air allows for more fuel. More fuel means more power.

      Or basically: Intercoolers are good.

      There are lots of schools of thought on the methods of intercooling. To summarize
      that, most people are wrong. Bigger is not always better, as it all depends on flow.

      If you install an intercooler with a huge area, let's say it's 36" long in the
      direction of flow, and 8" tall, but only 1" thick. All of your combustion air
      must pass thru 4 square inches, and the intercooler will have a significant
      pressure drop and will be a huge flow restriction. (8"x1" is 8 square inches,
      but only 1/2 of that is for charge flow. the other half is atmospheric flow thru the IC).

      If you read Corky Bell's book on turbocharging he states that a
      good rule of thumb is 6 square inches of flow area for every 100 hp.
      The second rule of thumb is 1.5xHP = airflow in CFM for gasoline engines.
      The third rule of thumb is diesels require 25% more air than gas engines.

      Analysis of the OEM TDI intercooler:
      size: 3.5x7x8
      flow area: 3.5x7/2 = 12.25 sq in
      A quick estimate on flowrate based on BellIntercoolers.com tables: Max flow = 240cfm.
      Max horsepower for the stock IC: 240/(1.5x1.25)=~128hp.


      Analysis of my IC:
      size: 3x6x9.4

      flow area = 3x9.4/2 = 14.1 sq in
      flowrate = 302 cfm (from the tables)
      max hp: 302/(1.5x1.25) = 161 HP

      I want the pickup to be a sleeper. I don't want big scoops or wings or anything
      like that. Being a pickup, there are somethings that are easier on the cars, and
      not so easy on the trucks. The TDI intercooler that came with the engine would've
      worked fine, it's just that I had nowhere to put it. I could've put it where the
      battery is, and then relocated the battery, but that would've been a bit of a pain.
      I could've put it over the tranny, but then I'd need a hood scoop. I could've put a
      front mount down below the bumper, but I couldn't figure out how to run the pipework.
      I decided to locate the IC in front of the radiator. But to do that, I couldn't use
      the TDI IC, I had to get a custom built one.

      Could I have gone larger? Yes. I could've gone with one about 8" wider.
      (basically, to fill the entire space between the headlights.

      Could I afford a larger IC? Well, not really.
      And with a max HP rating for the IC of about 160 hp, all should be fine.
      By the time the TDI gets to that power level, I should have a larger budget.

      I had to clearance the front support to mount the intercooler, and it's a very
      tight fit with the radiator. A 2.25" thick core would've fit perfectly. Also,
      I had to shorten the safety catch on the hood, as I couldn't close the hood
      (the catch was hitting the IC)

      The pipework is thinwall 2" stainless steel.
      The elbows are all rad-hoses.

      summary: ooohhhhh shiney

      Stay tuned...


      Part 1: Introduction
      Part 2: Installing the Engine
      Part 3: Transmission
      Part 4: Wiring 1
      Part 5: Speedometer and Cluster
      Part 6: ImmobilizerIII
      Part 7: Drive By Wire
      Part 8: Intercooler
      Part 9: Intake and Exhaust
      part 10: MFA and Cruise Control
      Part 11: The Dash
      Part 12: The Little Things
      Part 13: The End (for now)
      Part 14: 6spd transmission and brake upgrades
      One Year Later
      Dyno results
      Who Needs a VR6
      TDI Rabbit
      Last edited by MrDave; 02-16-2015 at 03:46 AM. Reason: VWV messed up formatting and links

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    3. 05-20-2003 03:55 PM #2
      As always, very interesting. [IMG]http://*****************.com/smile/emthup.gif[/IMG]

    4. Member fukengruven1982's Avatar
      Join Date
      Jan 8th, 2005
      Fleet O' Diesel Dubs.
      11-23-2006 08:23 PM #3

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