Zetec Turbo Cooling

In the second in our series of Zetec Turbo related articles we examine the vitally important aspect of a turbocharged Zetec installation that is cooling.

This includes taking a look at the options available and reviews and opinions on selection of intercoolers and chargecoolers from GRS, Pro Alloy, Pace, along with some custom options including the 2wd and 4x4 Cosworth coolers.

Note: This article was originally written a few years ago by (I believe) Dave Edwards and StevenRW from the RS Owner’s Club Bulletin Board. It was hosted on www.rstcooling.co.uk which now ceases to exist. The article below is an updated version with newer information and more focus on the Fiesta rather than Escort RS Turbo.


After the amount of discussions, arguments and debates about this subject on various forums, we decided that it was time to write a non-biased article to offer information to people considering upgrades to the cooling system of their RS Turbo. The information here can be applied to both the CVH Turbo and the Zetec Turbo, although the fittings may differ depending on setup.

For years this area has been overlooked in the field of tuning turbocharged cars, but the importance of decent cooling has become a big issue and companies are responding with some very good products. The ECU on a Fiesta RS Turbo retards the ignition timing at Charge Air Temperature (ACT’s) above 62 degrees C. When the ECU retards the timing, the car is not performing anywhere near as well as it should, or indeed could. Power is lost to compensate for the high ACT’s. Even before the ECU retards the ignition timing, the cooler you can get the ACT’s the better. To put it simply….

Colder air entering engine = Denser air = More air in cylinder = ECU adds more fuel = Bigger ‘BANG’ = More power!

Further to this - high ACT’s could be harming the engine, by increasing the chance of detonation. And who wants melted pistons if it can be avoided? Cooling should be number 1 on your list of modifications to your motor for power, reliability, and safety.

We have kept this article as unbiased as possible in the featured products. Both the authors of this page have however had a good deal of experience in this field, and have tested almost every product on this page personally or via close friends. Our views will be expressed in the final section. These are ONLY our views however and should be taken as such.

Disclaimer- The views on products expressed in this website are our own and do not necessarily express the views of everyone, or indeed the companies involved.

A bit about cooling

A good cooling setup needs to be made with a large volume, so that air is within the cooling product (whether that be the Intercooler or Chargecooler) for longer. The longer it is in there, the longer time it has to be cooled down, therefore lower ACTs are achieved. Good cooling products ideally need to have as large a cross sectional area as possible, so that more air from the front of the car hits the product at any one time. This is why uprated intercoolers are generally thicker, to give more volume, as well as slightly larger in cross section to get more air flow. A good cooling product will ideally keep ACTs down to below 40 degrees C.

We recommend the purchase of an ACT gauge. You cannot guess at what is going on inside your engine. These guages can be bought from Sainsbury’s Homebase, for £15. The sensor is then placed into the inlet passage somewhere.

These gauges are crude, as they have an update time of a few seconds, but offer a cheap indication to your temperatures. Alternatively, more professional gauges which update every second can be purchased from Mike Rainbird’s R&B Motorsport at a cost of around £45. We strongly recommend not automatically believing the manufacturer’s claims as to their product’s performance, but to either test yourself, or read about others personal experience. We would also like to point out that ambient temperatures (the temperature of the air outside) will affect the ACT reading. Obviously temperatures in winter will be colder than summer.

To find out what your ACTs are, you need to run at full boost, maximum RPM and therefore maximum load for a period of up to 30 seconds or more. This is the time when ACTs become critical and they need to be as low as possible and this is of course where your ACTs are going to be at their highest point. A good way of testing your ACTs, but without running in 5th gear at 140mph is to accelerate to 6000rpm in 4th gear, and then hold the car back on the brakes whilst still on the accelerator (maintaining 6000rpm in 4th) for 30 seconds or so. Keep your eye or get a friend to keep an eye on the ACT gauge -

Warning : You WILL get a shock if you connect an ACT gauge!!!

The Coolers

Standard Intercooler

The Fiesta RS Turbo standard Intercooler has a small surface area and its position in the engine bay means that it is not in a good place as far as airflow from the front of the car is concerned. It is slightly larger than the Escort RST item, the dimensions of which are 200mm x 150mm x 65mm. This give a volume of 1950 cubic centimetres.

Pace / Pro Alloy Intercooler - £270

The Pace Products and Pro Alloy intercoolers are very similar in design and gain their efficiency by having a larger surface area than the standard core. Pace claim it is 50% larger than a standard Intercooler. Using the volume of the standard intercooler (1950cubic cm) this means the volume of the Pace Intercooler is 2925 cubic centimeters. This gives 2 main advantages:

  • It ‘grabs’ more cold air from the front of the car.
  • The unit has much better air flow due to its larger capacity.


  • All alloy construction & polished tanks
  • Comes complete with fitting kit
  • 50% larger than standard cooler

Pace Chargecooler - £620

The Pace chargecooler works by passing the charge air through an intercooler jacketed in a container. Water is then passed through the container and the water absorbs the heat from the cooler. The water is then pumped round a system and in turn cooled by a radiator of its own. The theory is that the charge air will be cooled better by passing water through it than passing air through it as in the intercooler.


  • All alloy construction
  • Kit comes complete and ready to install
  • Now with heavy duty water pump

GRS Motorsport Chargecooler - £POA

The GRS Motorsport chargecooler works in exactly the same way as the equivalent product, by passing the charge air through an intercooler jacketed in a container. Water is then passed through the container and the water absorbs the heat from the cooler. The water is then pumped round a system and in turn cooled by a radiator of its own. The GRS Motorsport product features a different size and shape water radiator for the cooling of the the chargecooler water


  • Kit comes complete and ready to install
  • Fast Flowing water pump

GRS Motorsport Ultra Large “Evo 3” Intercooler - £315

The GRS Motorsport Large Intercooler is one of the largest standard production intercoolers for the Fiesta RS Turbo. It has a surface area nearly 5 times larger than that of the standard intercooler, and a very large amount of this surface area is in un-restricted air flow from the front of the car. The volume of the GRS Large Intercooler is 5760 cubic cm, that is 3 times larger than the standard intercooler and still twice as large as the Pace intercooler. This makes it the ideal choice for many Zetec Turbo installations and has proven itself in 170+ mph cars on several occasions.

Fitting of these coolers is not so straightforward as the smaller items. Due to it’s large surface area it will offer little improvement if hidden away behind the bumper, so it’s advisable to either cut away the bumper to improve air flow, or swap to a bumper of a more “open” design such as the Cosworth style item.

GRS Chargecooler / Intercooler combo - £POA

The GRS Motorsport Chargecooler / Intercooler combo is incorporates the GRS chargecooler shown above, with an additional intercooler to aid the ACT cooling process further. Complex pipe work links the turbo to the intercooler, which then connects to the chargecooler and then finally on into the engine.

Pro Alloy Front Mount Intercooler - £400

This is another large front mount cooler but it differs from the GRS in several ways. Firstly although the inlet and outlet are at the same ends, it is a single pass design. It does this by rotating the core from horizontal to vertical. Secondly despite appearing more expensive than the GRS, it is very competitive as the price includes a high quality fan, fittings and silicone hoses. These parts are are worth around £100 on their own.


  • Single pass high flow vertical core.
  • Surface cooling area 3 x the size of the standard cooler
  • Easy fitting with only minimal cutting required
  • Can be used with the standard radiator, Pro alloy fast road radiator or Pro alloy Race Spec radiator (100mm longer)
  • Kit is supplied complete with Spal fan and fitting kit, silicon joiner hoses and alloy pipework
  • Original bonnet catch and upright support bar are retained
  • Available to fit the T25 turbo or T3

Custom Twin Chargecooler

It is possible to connect two chargcoolers in series one such example utilises a Pace chargecooler and a Jaguar Chargecooler. The charge air is dragged through them both before entering the engine.

2wd Cosworth Intercooler ~ £50

Some people choose to fit a single 2wd Cosworth intercooler which offers a great improvement over standard, and is a lot easier to physically fit. The Cosworth intercoolers use a Behr core which is far superior to many others on the market. These cost whatever the cooler costs second hand.

The Cosworth intercoolers are all “single pass”. This indicates that the inlet and outlets are at opposite ends of the cooler, with the air going in one end and out of the other. This is the same method as the OEM FRST cooler. The GRS Evo cooler is a “double pass” unit - the air passes to the other side of the cooler before circulating back to the outlet mounted at the same end as the inlet.

Fitting will usually require some cutting to the bumper for air flow, although the lower aperture in Cosworth bumpers is the ideal shape for these coolers and no modification is required for maximum cooler exposure.

4x4 Cosworth Intercooler ~ £90

The 4x4 Intercooler uses the same excellent Behr core but is 25% larger than the 2wd item and offers even better performance. They tend to be harder to obtain than the 2wd cooler though as many 2wd Cosworth owners upgrade to the 4x4 item.

Combined Cosworth Intercoolers

Several Cosworth intercoolers may be combined to form a larger unit. The end tanks of the coolers are removed leaving just the cores, and new end tanks are fabricated. These coolers are very effective and relatively good value for money and if produced well can offer almost zero pressure drop across the intercooler.

The disadvantage to these is the thickness of the core may make the cooler difficult to install neatly. Space is already at a premium at the front of the Fiesta engine bay and such a thick cooler might require mounting the cooling fan on the rear of the radiator and relocating the turbo with a tubular manifold to clear it.

Norris Motorsport offer a triple 2wd Cosworth intercooler. This is produced to order and is perhaps the ultimate in RS Turbo cooling.

Our Opinion

OK so we’ve shown you all the options available. We will be adding information on coolers as and when people notify us of them. Feel free make comments or suggestions in the forums.

The standard charge air cooling on the RS Turbo is fine- for standard boost pressure. As soon as you think about upping the boost from the factory standard 6psi, you need to think about uprating the cooling, and quickly. As soon as the car is running increased boost, an uprated cooler is not just recommended, it is necessary. To leave the standard cooler in a tuned car is false economy as you won’t ever see the full benefit of your modifications!

Now for our opinion on what uprated cooler is the best to use. We think that chargecoolers are not worth the money. Generally speaking they are double the price of an intercooler, due to cost of producing the whole kit. Intercoolers are much more simple, making them cheaper, and easier for you to fit. Intercoolers have proven themselves to be more efficient over a period of time.

Pace products don’t measure up to others on the market in our opinion. The Pace intercooler is bigger than the standard item, nice and shiny, and looks beautiful sat behind the grill. The only problem is it doesn’t work! If you are looking for an easy cooler to fit, which looks nice, at an average price, go for the Pace one. On a chipped RS Turbo with little other modifications, it may do the job of keeping the ACT’s acceptable- it will never be ‘good’!

The Pace chargecooler - talking from experience here, I had one of these on my tuned RS Turbo. It simply could not keep the ACT’s down below 60 Degrees, and I didn’t even use fifth gear in the test. The problem with these is the cooler can only be as good as the temperature of the water passing through it. The water needs to be cooled, and cooled well. The pre-rad that comes in the Pace kit is poor. If you are considering one of these kits, the first thing on your shopping list should be a large radiator to plumb into the system, probably from a motorbike. The GRS chargecooler is very similar in terms of performance to the Pace equivalent. It gives similar ACT results for similar money. But again, the cost is getting towards twice that of an Intercooler because it is more complex.

The GRS chargecooler / intercooler setup is very effective. The intercooler is of a good enough size to aid the chargecooler for good results. But this setup does not come out on top of our list, purely due to cost. It is approximately £800 for a combo setup, which is 3 times the price of the GRS Large Intercooler, for no extra gain.

The GRS Large Intercooler in our opinion is the best production cooling product for the Fiesta RS Turbo, without a shadow of a doubt. Its large volume of approximately 3 times that of the standard intercooler means that air is within the Intercooler for longer, therefore being cooled further. The massive surface area means that more cold air flowing from the front of the car hits the intercooler. The main concern with this product was the engine radiator cooling fan positioning. The fan does not work well enough if it has to be in front of the intercooler as it cannot blow enough air through to the radiator. But a solution has been found, which involves purchasing a very thin 10” fan from Kenlowe for approximately £85 which fits in between the intercooler and the radiator. This works very well and will solve all issues with using this intercooler.

The 2wd intercoolers are proving themselves VERY efficient indeed. Even a single unit will keep the temps low enough for most applications. The problem with these is they were not designed for the Fiesta Turbo, and therefore do not fit. The bumper will have to be modified to make them fit, especially for a twin cooler. Do not be fooled by the £50 price of a second hand cooler, it will soon add up to more. Another factor here is the extra pipework needed to plumb these in. All pipework adds lag to the system. If however you are handy with a spanner (and a hacksaw) this is a very good, cheap option.

The Norris Motorsport coolers are awesome. These keep ACT’s as low as they can go, typically 5-10 degrees above ambient temperature. The cost of this cooler is more than the GRS Motorsport intercooler, as it is more complex and requires a reverse charge carrier pipe etc. These coolers are for hard tuned CVH or Zetec Turbos, or for people who simply want the best cooler available.


The second 20th Anniversary article, a dive into the history of how the site came about is available here: https://t.co/kbCfZ4sf0R

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