How-To - Fitting a G&M Aluminium Intercooler (CDTi)

[Arctic]

Hi Russ.
Thank you for posting i am sure it was your post ages that i read, reason for bring back the thread was that a member was thinking of one and i wanted to be sure that i gave him the information about them before he spent his money, as you say have they improved ? i doubt it or we would have heard about it by now surely.

Originals new are non existent as far as i know, and even good second hand ones are hard to come by.

[BigRuss]

Yes, I remember posting about it some years ago, it's all to do with fluid dynamics which also applies to airflow.
The calculations are very complex, probably far above the scope of an aftermarket manufacturer.

Unless it was an exact copy of the original it will most likely cause the problems as described.

A decent radiator re-core specialist may be able to refin and rebuild a corroded intercooler.

Russ

[Robson Rover Repair]

The simple solution is to fit a manual boost controller and why anyone would change to a bigger intercooler and not do that is beyond me.

Reason why it's down on power is to do with the volume of air being shifted.

As the intercooler is now larger its able to hold more air per square unit which means instead of shifting say 50 units of air, its now capable of shifting 100 units of air, but the car was optimised for 50, making it feel half as effective.

Essentially its like fitting a larger sink in your kitchen to the same sized tap. The water can't flow any faster, and actually takes longer to fill up unless you change to a bigger tap.

You find typically on our cars a larger intercooler will drop 4 or 5 psi. This doesn't mean the cars not right, your just gonna have to adjust the boost representive to new parts and air moving capacity.

Pressure per square inch here folks. You have fitted a bigger capacity unit and need to adjust the pressure intake accordingly, the psi setting was based in your old factory components.

Obviously you can then bring it back to factory 17/19 psi using a manual boost controller or up to 23/24 psi before boost cut kicks in.

I've mine all set at 22.5 personally along with mafless remaps to match, egr bypass and decats, and barely a drop of smoke on full throttle as they are mapped correctly. With plans for solid steel hard pipe work replacing everything plastic next and dual maps once I've my white 75 mot'd again.

Only caution I'd say about setting the boost is there are boost controllers specifically for diesels, I'd highly recemmend you get one for none vnt turbos and one with a quality locking grub screw that once set won't vibrate loose to over or under boost again once set correctly.

Even a decent cheap unit will set you back £20, takes 10 mins to fit and you read the boost via the odb plug on toaf or any odb car phone app.

[Gino]

Originally Posted by Robson Rover Repair

The simple solution is to fit a manual boost controller and why anyone would change to a bigger intercooler and not do that is beyond me.

Reason why it's down on power is to do with the volume of air being shifted.

As the intercooler is now larger its able to hold more air per square unit which means instead of shifting say 50 units of air, its now capable of shifting 100 units of air, but the car was optimised for 50, making it feel half as effective.

Essentially its like fitting a larger sink in your kitchen to the same sized tap. The water can't flow any faster, and actually takes longer to fill up unless you change to a bigger tap.

You find typically on our cars a larger intercooler will drop 4 or 5 psi. This doesn't mean the cars not right, your just gonna have to adjust the boost representive to new parts and air moving capacity.

Pressure per square inch here folks. You have fitted a bigger capacity unit and need to adjust the pressure intake accordingly, the psi setting was based in your old factory components.

Obviously you can then bring it back to factory 17/19 psi using a manual boost controller or up to 23/24 psi before boost cut kicks in.

I've mine all set at 22.5 personally along with mafless remaps to match, egr bypass and decats, and barely a drop of smoke on full throttle as they are mapped correctly. With plans for solid steel hard pipe work replacing everything plastic next and dual maps once I've my white 75 mot'd again.

Only caution I'd say about setting the boost is there are boost controllers specifically for diesels, I'd highly recemmend you get one for none vnt turbos and one with a quality locking grub screw that once set won't vibrate loose to over or under boost again once set correctly.

Even a decent cheap unit will set you back £20, takes 10 mins to fit and you read the boost via the odb plug on toaf or any odb car phone app.

Good morning Colin,

back in January I fitted an aftermarket intercooler & think I have the problems you are describing with under boost. My intercooler was falling apart & had to be replaced, in my opinion. I couldn't find a good 2nd hand unit so had no choice but go with the aftermarket.
After reading your comments I'd like to fit a boost controller, but the problem is the OBD does not communicate with a phone app. I think it has something to do with my car being early 2002, although I can be wrong. Do you know of any workarounds?

Thanks,

Rob

[Robson Rover Repair]

Any basic fault software reader or diagnostic system can read the boost, t4 and toaf is bound to have a boost reader in there. I've never checked myself.

I was able to get odb working on my 2001 diesel auto tourer for boost via torque using a USB c to odb wired cable.

Must have a look on toaf here quickly once the toaf book is charged up.

[Gino]

Hi Colin,
I dont suppose you have a link to a suitable obd reader? Or know what the correct boost pressure should be? I've had a quick look around & think it should be around 21.

Thanks,

Rob

[Robson Rover Repair]

Factory is 1.2bar so about 17.4 psi, but even then depending how your reading it might be off. Memory makes me think boost cut is 21.4 but I also think the sensor can't read beyond it.

Personally I'd advice just to just get a laptop with toaf or toaf mobile and use it to get the pressure and then set it appropriately.