What is a intercooler? And why do I need one on my 1.8t?
An intercooler is an intake air cooling device which is a necessity for turbocharged vehicles. This is because as the intake air passes through the turbo it increases in temperature due to the compression and also due to heat transfer from the hot turbo housing. This increase in temperature causes the air density to drop and therefore its oxygen content. An efficient intercooler will keep the intake air cool, increasing its density and oxygen content thus allowing more fuel to be burned, improving combustion and giving more power.
There are two types of intercoolers; Air-to-Air and Air-to-Water
The most commonly used type of intercooler mainly down to cost and simplicity. They work by removing the heat from the compressed air by passing it through the charge side of the core which has a network of tube/bars which are filled with fins. As the compressed air is pushed through the intercooler it transfers the heat to the fins and therefor the tubes/bars. The cool air from outside the car travels at speed through the core between the external surfaces of the tubes/bars which also have fins between them. The heat from the tubes/bars transfer to the fins and is then absorbed by this cool air. Hence overall reducing the temperature of the compressed intake air.
• Lower cost
• Light weight.
• Longer intake length (as the intercooler is usually at the front of the car)
• More variation in temperature than the Air-to-Water type.
Air-to-water is a less common means of cooling charge air. It works by using water as a heat transfer agent. Heated compressed air travels through a heat exchanger similar to that of an air-to-air intercooler but rather than using cold air to cool the compressed air this setup takes cold water and pumps it through the air/water heat exchanger, extracting heat from the compressed air as it passes through. The heated water is then pumped through another cooling circuit (usually a separate dedicated radiator located at the front of the car) while the cooled compressed air is pushed into the engine.
• Smaller than Air-to-Air intercoolers which makes them more suited to difficult installations (such as mid/rear engine cars) where space, airflow and intake length are an issue.
• Water is more efficient at heat transfer than air and has more stability so it can handle a wider range of temperatures.
• More complex
• Added cost of a radiator, a pump, water and transfer lines.
What do I currently have?
The 1.8t platform came with 2 different intercooler setups. The K03 and K03s powered cars came with a single side mounted intercooler. The K04 powered cars came with a twin side mounted intercooler (one in front of each front wheel)
What should I buy?
The decision is entirely up to you. Although on the 1.8T platform it is A LOT more common to use an air-to-air intercooler so for the purpose of this article we are going to stick to talking about those.
Side mounted (SMIC) or Front mounted (FMIC)?
There are “upgraded” SMIC’s available on the market but we advise that you avoid these. They have been found in the past by many tuners to not be much better than the standard cores. This is due to the lack of airflow in the area of the core meaning a lack of cooling and high intake air temperatures
Using a FMIC is a much better option as they have a larger surface area and with being placed at the front of the car behind the centre grill they are exposed to lots of cold air and that cold air is able to pass through the core into the engine bay.
Bar and plate or Tube and fin?
Bar and plate cores are heavy but cheaper. Flow great and cool well.
Cheap tube and fin cores must be avoided. This is due to poor flow causing high pressure drop meaning the turbo must working harder to create the desired boost and therefore creating more heat. Although well designed tube and fin core which use louvers etc work incredibly well but this is reflected by the high costs.
For the majority of people we recommend the Toyosports bar and plate intercooler due to them being proven time and time again to perform incredibly and are a reasonable price.
Twin pass or single pass?
Overall single pass cores are a better option. Twin pass cores have a higher pressure drop than a single pass core of the same size. Although for some setups where space is limited or where discreetness is more important than outright power they are a good compromise.
It’s has been found that on the smaller turbos such as the K03 and K03s a twin pass cooler can work very well upto around 240-250bhp. But if you plan on pushing the setup for max performance we recommend avoiding them.
What size do I need?
The size of the core you need depends on the application. For smaller turbos such as the k03s we don’t want too big of a core as you lose the low down punchiness that the small turbos are renowned for. It has been found that the Toyosports 550x225x63mm matches perfectly to the smaller sub 300bhp turbos flow and gives sufficient cooling of the charge air.
For K03 hybrids such as the BBT K300 or for stock k04-023 turbos we suggest either using the 550x225x63mm core as above or if you are pushing the setup and want the max possible power out of it going for the 600x300x76mm Toyosports core also known as the “Wellycooler” which originated from a forum member called “Welly” first testing the core on his K04 setup with great results many years ago.
Foe 300bhp+ setups such as K04 hybrids, K04-064 and big turbos setups we suggest sticking to the 600x300x76mm core.
What about the pipework?
Over the years it has been found that for setups up to around about the 600+bhp mark the most suitable pipework size is 63mm. Fitting pipework any larger than 63mm will cause a loss of air velocity within the pipework thus increasing lag. Fitting Pipework smaller than 63mm reduces flow and induces high pressure drop across the whole setup. Although it has been found on the smaller k03 and k03s setups having the first half of the hot side pipework a smaller 57mm has no detrimental effect and can increase the low down punchiness mentioned before.
We recommend that you always use beaded pipework. This prevents any silicone joins slipping on which is a very common occurrence with non-beaded pipes. You can buy the pipe pre beaded but when making the intercooler pipework it is likely you will lose some of these while cutting the pipes to fit. There are a couple of options for replacing the bead. You can either make a DIY beading tool (see image gallery at the bottom of the page) this is the easiest and cheapest option if you have the parts at home. Secondly you can get someday with a proper bead roller to apply a bead to the pipes for you, or lastly you can get a weld run around the end of the pipe although this will be the most expensive and also the least effective.
How should I route my pipework?
There are several different ways to route the intercooler pipework and it mainly comes down to personal preference and how you want the engine bay to look. It also depends on whether you have a left or right side facing inlet. But the main thing to note is that you want the pipework to be as free flowing as possible which means minimum bends and what bends there are should be nice and sweeping, not tight radius 180 degree bends etc. As an example if you can fit 2 45 degrees bends rather then 1 90 degree bend that would be preferable. It is also good to have as much welded hard pipe as possible so there are less clamped silicone joins which could possibly leak! But note that it is still advised to have one silicone join in the middle of a large hard pipe section to allow for some flex and also aid in fitting. We recommend using JCS Hi-Grip jubilee clips on all your silicone joins.
How do I make my FMIC setup?
- You need to start with decided how the pipework is going route. As said previously this is down to personal preference. Once decided figure out how many alloy bends, silicone bends/couplers and roughly how much straight alloy pipe you will need. You may want to buy a single 45 and 90 degree alloy pipe so you can have a play in the engine bay figuring where it will fit etc.
- Next up is to buy the Core, the list of pipework you have made and enough JCS hi-grip clips for your silicone joins. You will also need an alloy 25mm take off, 6mm alloy take off and if running a me7 ecu (distinguishable by having a drive by wire throttle body) you will also need a weld on map sensor boss.
- When all the parts arrive you need to figure a way of securely fixing the core. This is normally done with the use of metal brackets being secured to the crash bar or slam panel. Then you need to make your way through making your pipework cutting the pipes to size and securing them together using duct tape.
- Once you are happy with the pipework routing and it’s all taped together you need to mark and drill where you want the 25mm, 6mm and map sensor boss
- Then send them to your welder and get them all stuck together!
See below for a few examples of different 1.8t intercooler setups.