Golf 1.8GTI 1.8T Intercooler Kit

1.8T Golf Mk4 Twin Pass Cooler

The idea

The 1.8T MK4 Golf platforms utilise a small side mount intercooler as standard, which provides adequate cooling for a stock car. However once boost levels are increased, either by ECU remapping or the introduction of a bigger turbo, the stock cooler is unable to maintain low intake temperatures.

Once the air intake temperature gets too hot, the engine ECU will retard the timing and lower boost levels to maintain engine’s safety.

The Golfs existing intercooler system is designed around the fact that the turbo outlet and inlet manifold on the same side. Traditional single pass intercooler's are not suited to this set up and result in long lengths of extra pipe work (often under the car). The only effective solution for a front mounted cooler is a twin pass cooler.

The other part of the charge air system which is restricted is the flat boost pipe inside the wheel arch (appropriately nick named the "pancake pipe")

The Flip!

When using a twin pass intercooler (especially on a Golf) it is more efficient for the turbo outlet air (hot side) to pass through the top of the intercooler first and then flow back through the bottom. Why?

• Heat rises! When off boost, hot charge air rises. Once back on boost the colder air at the bottom of the cooler is used first
• The bumper design of the golf means the bottom half of the cooler receives the most cooling from air passing over it.
  Hot charge air from the turbo enters top of the cooler, returning through the colder bottom half before entering the engine.

The Design

To utilise the extra efficiency we have developed pipe work that flips hot side charge air to the top of the intercooler and the cold side charge air to the bottom of the intercooler. Using the ‘Flip Pipe’ design also allows the intercooler piping to make smaller directional changes which further helps increases air flow.

The end tanks are TIG welded to a bar and plate core. The complete cooler is pressure tested to 5bar (72psi)

The kit

The THS 1.8T cooler features a Bar and Plate core. Bar and Plate core offers similar cooling properties as tube and fin systems but has the added advantage of reducing pressure drop due to lower hydraulic internal restrictions.

The also includes our Pancake Replacement Pipe (PCR). The pipe removes the restrictive standard squashed pancake pipe from the wheel arch area and replaces it with our free flowing PCR pipe The PCR pipe still allows the same clearance on the front wheel when on full lock as the original pipe!

Pressure drop

How does reducing pressure drop help?

On the 1.8T engine the boost pressure is measured on the up-pipe after the intercooler. However the boost pressure here, or at the intake manifold will be less than that at the turbo outlet. This is because of the restriction of the intercooler and pipe work.

Reducing the pressure drop by means of a more efficient intercooler and pipe work requires the turbo to produce less boost pressure at its outlet whilst still maintaining the required boost pressure at the intake manifold.

This has 2 distinct advantages:

1. Compressing air causes it to increase in temperature, the less it is compressed the colder it remains.
   An intercooler which offers good cooling but with a high pressure drop due to restrictive core and excessive pipe work is less efficient than one with similar cooling but a less restriction.
2. The turbo is not working as hard to produce the same requested boost at the manifold. Prolonging the life of turbo.

The result

Giving lower intake temperatures right across the rev range. Let the figures speak for themselves. Figures shown are with Revo stage2 settings: boost 9, timing 6.

Fitting Instructions

Supplied with the intercooler are a set of comprehensive instructions.