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Discussion Starter · #1 ·
Coming from an R53 a few years ago. I finally came back to having a Mini after a break. And once again love my car.

Much like everyone else, I was pretty sad to see that the Cooper S had lost its pops, bangs and crackles. But what can you do with Euro 6 emissions standards.

After a lot of searching about I was lucky enough to come across a GP3 exhaust that was up for sale. Boy what a difference it makes. A few burbles here and there now, and a much more spirited tone. Feels much more Mini like now.
 

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Discussion Starter · #2 ·
Next thing is a slight tweak in the air intake system. I have my eye on a GP3 intake system, so I’m curious to see what difference that makes if any at all.
 

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22 JCW Hatch Manual Rebel Green
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The exhaust tone lets them down a bit indeed - well done on the upgrade 👍 I have my eyes on JCW Pro, to add a bit of juice.
 

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Discussion Starter · #8 ·
Thanks. I am a lot happier. Has a lot more smiles for miles. I have a before somewhere. So I might bundle that together as a video to compare.

Currently looking to see what I can do with the air intake. Upon investigating the GP3 intake; which as far as I can tell is the same as the 306hp Clubman, there are quite a few differences between the JCW intake layout and the GP3.

Guess it makes sense as they are both outputting more power, so they need larger intakes. But the cross link is totally different on the GP3. Images online for the part number seem to confuse the issue somewhat as they are the same.

I’d assume more air still equals more power…
 

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My technical understanding is limited but from a layman perspective anything freeflowing, even just an exhaust, should indeed give more power. There should be someone on here who's got first hand experience with the GP3 kit - where are you folks?!
 

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Discussion Starter · #10 · (Edited)
About the same as mine then.

The interesting thing with the GP3 kit is that the intake is pretty standard. Higher capacity, but generally the same. It’s the fitment that seems odd.

There is a different cowl design to allow for the larger intake. So that should be a straight forward update.
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Gets more interesting here as the GP3 intake is wider, so the standard bonnet supports have been moved onto a new cross brace.
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But if you look at the Clubman 306hp version. Same cross member/strut. But they have a moulded section for the support braces. On the cowling section.

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You can kind of see it here in the parts diagram.

Main question really is how important are those supports, I guess they are there for a reason. Ideally you’d want to either extend out or build up from the air duct housing.
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Main reason for not just replacing the strut is that it is an eye-watering £550 for the GP3 version. It’s the only model it is used on.

l’ll have to have a think and see what the options are.
 

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2021 F56 Cooper SE Level 2
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My technical understanding is limited but from a layman perspective anything freeflowing, even just an exhaust, should indeed give more power. There should be someone on here who's got first hand experience with the GP3 kit - where are you folks?!
It's not quite as simple as that. Fundamentally yes - more air in means you can add more fuel to get a bigger bang, and more gas out means it can escape quickly. But it isn't just volume of air that's important, it is temperature, density and speed and all of these can be impacted by the pipework volume, cross-section and routing. Not forgetting there's a turbocharger in the way.
 

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Discussion Starter · #12 ·
Thanks @figbat. From an engineering perspective I'd like to think that BMW know what they are up too. The facts are; that the GP3 and the Clubman both have bigger air intakes. So there must be a need for more air in that design to make more power (using the standard S/JCW intakes on both versions wasn't providing enough air). The air ducts should be engineered for increased volume, density and speed. Also there other fundamentals involved from an engine perspective including compression, turbo etc

My brain is telling me that a higher capacity design should make a difference. Even with a restricted engine tune.

It's not quite as simple as that. Fundamentally yes - more air in means you can add more fuel to get a bigger bang, and more gas out means it can escape quickly. But it isn't just volume of air that's important, it is temperature, density and speed and all of these can be impacted by the pipework volume, cross-section and routing. Not forgetting there's a turbocharger in the way.
 

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Discussion Starter · #13 ·
So a bit more of an update on the actual intake setup. (Even if it is marketing materials)

In addition, the extreme performance of the 4-cylinder engine is achieved by means of a newly developed turbocharger. It is integrated into the exhaust manifold and fitted with a divert-air valve that helps optimise its response. The compression ratio of the engine in the MINI John Cooper Works has been reduced from 10.2 to 9.5 in line with the increased boost pressure as provided by the system. The intake air duct has also been newly developed. Enlarged inlet and flow cross-sections and the increased volume of the noise damper ensure maximum dethrottling.

There was also some more information here on the X2 M35i which I think is the same engine.

The X2 M35i gets a reinforced crankshaft with larger main bearings and new pistons with a lower 9.5:1 compression ratio. This allows the engine to take more boost pressure from a larger turbocharger, which blows compressed air through an intake tract that's been reworked for better airflow.

 

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Discussion Starter · #14 ·
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So just a very quick update. Pulled the trigger on the GP3 air box and it’s here.

I have a load of conflicting information from a load of sources. But alt least I should be able to feedback in some capacity.

Have no idea where this is going. Currently things look like they line up. And top down sizes are very similar. But I we will have to see.

I’m going to be posting out exact details with a sort of install and if there are any issues on going so we have a reference in the future.

Still waiting for some bits to arrive so fingers crossed 🤞
 

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Discussion Starter · #16 ·
Watching. Let us know real world gains
This will be the interesting thing.
If and this is a big if, if we see more power it won’t be huge. But we should get more air in. Which should mean something.
Currently no dyno readings so will be more of a feel thing. But it’s been bugging me as to will it fit.
If nothing else I can answer that.
 

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Discussion Starter · #17 ·
I also found this explanation which gives some idea of improvements


Example 1:

Let’s assume this car is running a restrictive stock intake and filter setup that creates a 2.0psig pressure loss (vacuum) at the compressor wheel. You must subtract this from the atmospheric pressure value in the denominator, and when you do the calculation again ((20psig + 14.7psia) / (-2psig + 14.7psia)), you come up with a pressure ratio of 2.73. This means that for the turbo to run 20psig, the turbo is working as hard as if it was running 25.5psig in a “perfect world”!
Example 2:

Now, let’s say we upgrade to a better flowing intake that is still stock size and reduces the negative pressure in the intake by .5psig. Running the calculation again ((20psig + 14.7psia) / (-1.5psig + 14.7psia)), we get a pressure ratio of 2.63. This has reduced the work load on the turbo by 1.6 psi and the turbo is now only working as hard as if it were pushing 23.9psig in our “perfect world”.
 

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Discussion Starter · #18 ·
So today was the day. Finally had everything turn up and had the time to go through some fitting.

First off all, these are what I am working with now.

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So all is good from that point of view. I began with removing the snorkel assembly and removing the MAF, all really straight forward. And was then able to remove the existing airbox, and place in the new one.

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You can see from here that the intake for the GP3 is huge by comparison to the existing air box. And you can see if more so when you compare the snorkels to each other.

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Good thing is now that when you get eveything to line up I think that we will get a clean bonnet close. But this then raised the only issue so far.

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The intake tube and the exit from the air tube are pretty much the same size. Not ideal. So the inner dimension of the existing air box is 76mm, where as the GP3 one is around 89mm. Slightly annoying as this was one of the things that I checked with a mini dealer in the US, but hey ho.

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So overall great, but with some hurdles that I still need to overcome. I should be able to get a proper fit of the snorkels once I have got the box to fit. I also have the other issue now with how much difference is it going to have by going down a size from airbox to resonator.
 

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Discussion Starter · #19 ·
Coupler ordered now from 3.5” to 3“ I’m hoping now that we might be heading in the right direction. So with any luck it might marry up.

🤞 for tomorrow.
 

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Discussion Starter · #20 ·
So coupler arrived, but to be honest I’m not sure it is fit for purpose. New one on order now. Mainly due to the inner fitment just looked like it was going to cause more issues. So I’ve gone for a different one.

I’m having to look at a 4” to 3” (96mm to 76mm) reduction to go from the outside of the GP3 to the inside of the original intake filter. Only issue is now that amazon is saying delivery is the 4th of July, so watch this space.
 
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