Process West Top Mount Intercooler Kit Black – Subaru Forester XT SG 03-08 (02 STI Scoop)


Process West Top Mount Intercooler Kit Black – Subaru Forester XT SG 03-08 (02 STI Scoop)

The goal when developing our new top mounted intercooler was to make it the very best aftermarket top mounted intercooler for WRX/STi… period. We studied our competitors products and fixed all of the mistakes they have made…some of them major. The most obvious error that EVERY one of our competors makes is not supplying their intercooler with proper ducting/shrouding to suit the increased size of the new intercooler. There is no point in installing a larger intercooler and leaving the factory under bonnet splitter/shroud in place. Here is the solution. A properly sized splitter/shroud to suit the application. Pictured below is a pic of our top mounted intercooler installed in a 2006 Forester XT. For demonstration purposes we have removed the factory splitter/shroud and placed it on the intercooler as if the bonnet were shut. Its simple to see that 50% of the new upgraded intercooler would be seeing no ambient air flow… total waste of time and money. The picture (below right) is how it should be done. Process West intercooler and splitter/combination showing 100% of the new larger intercooler with full ambient airflow over the entire core. The next major problem that we see competitors doing (and they all copy each other) is building an intercooler that is too thick. Their design criteria is spot on for bragging rights whilst marketing. They say that bigger is better. This is totally not the case with an intercooler that is mounted at 90 degrees to the ambient air flow. For good heat exchange to take place you need good ambient airflow through the intercooler. In the case of the boxer engine with its intercooler mounted under a bonnet scoop the ambient airflow speed is already struggling after doing a 90 degree turn through the scoop. The last thing it now needs to do is find its way through 114mm (4.5in) of intercooler core. This will result poor heat exchange and high inlet temps. Our intercooler is 90mm thick (3.5in) and in turn the intercooler breathes, gives lower outlets temps and in turn more power. SILICONE Y-PIPE Almost all of the aftermarket Y-pipes we see do not distribute the charge air flow along the intercooler evenly. Their Y-pipe usually consists of one nicely flowing section with an afterthough spout as the second duct. Looking at the picture (below left) it’s easy to see that our Y-pipe will give perfect charge air distribution. Combining all 3 features of out top mounted intercooler gives the perfectly designed top mounted intercooler for Subaru. This picture (below right) shows the complete combination of Y-pipe (underneath), intercooler and splitter. DYNO TESTING Before looking at the results below I must say that dynos and top mounted intercoolers are not a great mix. No matter where you position the dyno fan there is still very little air flow into the bonnet scoop. Having said that both the stock intercooler and the PW upgrade intercooler were subject to exactly the same test conditions. A few other things worth mentioning. The test vehicle was a stock (apart from a BPM GT exhaust system) 05 WRX. Stock WRXs consistently put down about 90kw ATW on his dyno. The intercooler outlet temp probe was placed in the silicon hose joiner at the throttle body. (IAT on the data sheet). We started off with the PW intercooler/splitter and did a base line power run. Result was 115.5kw. Looking at the intercooler outlet temp saw a peak of 51C. I must say at this point I was a little disappointed. We saved all of the data collected during the run so that we could overlay it with the results from the stock intercooler. Next we installed the stock intercooler/splitter. Max power was 107.5kw. More disturbing was how badly the factory WRX intercooler performs. STREET TESTING Ok, real testing is done on the road. The only data that I was able to get on the road (with the equipment that I have) is intercooler outlet temps. I used a Fluke 87 digital multimeter with a K-type thermo couple just before the throttle body. (same position a the dyno test). Im not able log this data so you will just have to take my word for it.(Hence the reason stage 2 testing that will be done) While doing the dyno testing I compared my Fluke meter with the dyno AIT probe and they were always within a degree of each other. So, out into mountains with the PW intercooler/splitter combo. Basically I was unable to get the intercooler outlet temp above 43C no matter how hard I pushed. Great… now Im happy. Back to workshop and changed back to the stock intercooler/splitter. Went and did the same hard driving and saw a peak of 72C which would probably have kept rising but I decided that was enough. The car also felt a lot less lively.


There are no reviews yet.

Only logged in customers who have purchased this product may leave a review.

Product Location

Product Enquiry

This privacy policy sets out how we uses and protects any information that you give us when you use this website.

We are committed to ensuring that your privacy is protected. Should we ask you to provide certain information by which you can be identified when using this website, then you can be assured that it will only be used in accordance with this privacy statement.

We may change this policy from time to time by updating this page. You should check this page from time to time to ensure that you are happy with any changes.

What we collect

We may collect the following information:

name and job title
contact information including email address
demographic information such as postcode, preferences and interests
other information relevant to customer surveys and/or offers
What we do with the information we gather

We require this information to understand your needs and provide you with a better service, and in particular for the following reasons:

Internal record keeping.
We may use the information to improve our products and services.
We may periodically send promotional emails about new products, special offers or other information which we think you may find interesting using the email address which you have provided.
From time to time, we may also use your information to contact you for market research purposes. We may contact you by email, phone, fax or mail. We may use the information to customise the website according to your interests.

We are committed to ensuring that your information is secure. In order to prevent unauthorised access or disclosure, we have put in place suitable physical, electronic and managerial procedures to safeguard and secure the information we collect online.

How we use cookies

A cookie is a small file which asks permission to be placed on your computer's hard drive. Once you agree, the file is added and the cookie helps analyse web traffic or lets you know when you visit a particular site. Cookies allow web applications to respond to you as an individual. The web application can tailor its operations to your needs, likes and dislikes by gathering and remembering information about your preferences.

We use traffic log cookies to identify which pages are being used. This helps us analyse data about webpage traffic and improve our website in order to tailor it to customer needs. We only use this information for statistical analysis purposes and then the data is removed from the system.
Overall, cookies help us provide you with a better website by enabling us to monitor which pages you find useful and which you do not. A cookie in no way gives us access to your computer or any information about you, other than the data you choose to share with us.
You can choose to accept or decline cookies. Most web browsers automatically accept cookies, but you can usually modify your browser setting to decline cookies if you prefer. This may prevent you from taking full advantage of the website.

Links to other websites

Our website may contain links to other websites of interest. However, once you have used these links to leave our site, you should note that we do not have any control over that other website. Therefore, we cannot be responsible for the protection and privacy of any information which you provide whilst visiting such sites and such sites are not governed by this privacy statement. You should exercise caution and look at the privacy statement applicable to the website in question.

Controlling your personal information

You may choose to restrict the collection or use of your personal information in the following ways:

whenever you are asked to fill in a form on the website, look for the box that you can click to indicate that you do not want the information to be used by anybody for direct marketing purposes
if you have previously agreed to us using your personal information for direct marketing purposes, you may change your mind at any time by writing to or emailing us.
We will not sell, distribute or lease your personal information to third parties unless we have your permission or are required by law to do so. We may use your personal information to send you promotional information about third parties which we think you may find interesting if you tell us that you wish this to happen.

If you believe that any information we are holding on you is incorrect or incomplete, please write to or email us as soon as possible at the above address. We will promptly correct any information found to be incorrect.