I found this thread "SC inlet plenum -new worthwhile mod from GTT" rather intersting over at MINI2 and thought I would bring it your attention.

http://www.mini2.com/forum/showthread.php?t=106656

 

nice find. thanks!

 

By reading this the issue is resolved by just replacing the tube with one from an 05-06 MCS. Or do what they did for free

 

mdsbrain,
Did you mean a MCSA tube?

 

Maybe...I don't recall which 05-06 model had it.

 

Does anybody know which model has the preferred SC inlet plenum or should I try to modify it myself?
Is this what BBR calls their "Changes to the boost and intercooling delivery systems?"

 

Are you sure about that? I think it's on all manual 02-06 MCSs (dunno anything about the MCSa)

By the way, i've known about this for ages, I thought you guys would have known about it too! Its definitely something i'll be doing on my 05 MCS, as soon as i fix it that is :D

 

the new piece for autos doesn't do it. Break out the heat gun and go for it with a stock piece....

Here are Roland's test results...


Hi Guys, ok some test results for you, but first a couple of points. Firstly I didn't get to do an identical test with 'unmodified plenum' ( Im not taking it off again at the moment, its a fair bit of work). The largest drop in pressure will show using small sc pulley and max revs, so this is what we used.
This is an extremley accurate way of testing as it is actual conditions with real life airflow over the windscreen ,& through the grille etc. The result shows any restriction in A) airflow into airbox B) air filter element and trumpet design (or in the case of non GTT filters 'lack of trumpet'!!! ) (C) Throttle body & (D) S/C Inlet plenum.
We connected the vacuum gauge to the inlet on the S/C itself (ie where the PCV valve /OCC normally connects.) This outlet is at 90 degrees to the airflow ;important so as to not to introduce any additional dynamic pressure into the results.The PCV just vents to atmosphere during the test. If we had connected to the plenum itself ,ie where the upstream map sensor 'T's off ,any restiction in the plastic plenum would not show.
All in all a demanding test that will show up any gremlins!

First test was with all the mods .ie GTT Cold Ram Induction KIt+ GTT 63mm Throttle Body with knife-edged spindle + GTT modded plastic plenum. Tested at 6500 at WOT vacuum measured
-0.8psi .Next substitute stock hose for silicone one and re-test ,again -0.8psi.
Next use standard airbox with brand new element , (still with GTT 63mm TB and GTT plenum.)
Result -2.0psi ,yup thats over twice the pressure drop! Finally we fit the 'ultimate airflow element' into the stock box ,(in other words no element at all) and re-test. Result -1.4psi
in other words halfway house. With a K&N element in there obviously the result can only be worse than this,with a result probably near to stock element in stock box.( -1.9psi?)
CONCLUSIONS An improvement at the SC inlet of 1.2 psi at max rpm is quite a bit and would explain why adding GTT cold ram will give around 10bhp, this is what we achieved on the rollers when adding just this to our GTT210 kit.I would like to retest with stock throttle body and see if restriction increases. If it doesnt then the plenum is still the restriction..


End Roland's Results....

Matt

 

Who has a heat resistant plenum catheter?


Hmmmm......bike tube....rubber cement.....clamps.........safety glasses

 

Well, glad to see this thread awake. So I just woke up M2

 

I spent a couple of hours heating and stretching the s/c inlet plenum on my 2003. This will go down in my book as one of the worst engineered parts I have ever seen. Someone ought to make an aftermarket version!

 

Is M7 the only company that has noticed the need for a new tube? (AGS)

They could probably make a good chunk-o-change just selling their alluminum tube instead of only getting it with the entire system!

 

will not fit because it relocates the TB. I first learned about this modification from Roland at GTT.

 

why isn't GTT the ones capitalizing on it!?

 

They originally said they'd sell the modded part flat out or on exchange.
Haven't heard anything since although I noticed the thread got bumped up today

 

It's a part you already have, and all it takes is initiative to capatilize on it.

Get a broom handle, a 6 pack and a heat gun and go for it!

Matt

ps, mods to this part have floated around for a while....

 

Unfortunately, the former official contrarian is un-willing to comment, so allow me to interject some points to ponder.

Roland’s results with the stock box and filter are contrary to previous experiments measuring pressure drop across the stock filter in the stock box.

The stock supercharger intake duct has limitations that go beyond its oddball shapes. I cut the SID into 6 critical sections and measured circumference of each section. Even with straightening the bends in the stock SID there will still be a narrowing of internal area at a point just downstream of the breather tube boss measuring 53mm; that’s 5mm less than the stock throttle body. Here’s an old thread on the Webb forum showing the evolution of my thoughts on the SID entering on page two; http://store.webbmotorsports.com/for...r=asc&start=15 . Since then I’ve modified two other SIDs and conclude (supported only by time and experience) the most important factors in stock SID performance are the gasket at the interface between the SID & SC and vent hose seal.

According to my local MINI parts department, cracks in the SID are common. One of the design strengths of the SID’s bends and convoluted shapes is rigidity. It takes some force to get the SID aligned with the bypass valve and supercharger, hence the need for structural strength in addition to the form factor. When applying heat and manipulation, stress to the composite material will occur; keep that in mind for long term performance.

 

is it possible to fabricate a smoothed out SID out of metal, with a circular circumference of at least 58mm?

 

and that the flow perterbation is larger than the diameter of the shaft. I'd think that a 53 mm duct is a pretty good match for a 58 mm TB....

But so what? Point is that you can make an improvement here, and that all it costs is time.

Also, for those with eary cars, there was a lot of glue flash on the joints, so taking it off, and optimizing it isn't a bad idea, and it would be hard to make it worst.

Also, circumfrence isn't the correct measure. It's open area that's what is relavent.....

Matt

 

Matt, please provide more information about your understanding of “perturbation”. In my limited understanding of fluid dynamics there would be an exchange of energy between the two motions of air but it would not be mutually additive or subtractive in terms of overall volume once the two streams reunited.

Something I’ve wondered about is whether in designing the supercharger intake duct some of what appears to be form factor considerations may in fact be engineered shaping to counter vorticity resulting from the disruption of laminar flow after the incoming air contacts the butterfly and shaft creating the free space and then encountering the first right hand turn. I agree that cross-sectional area is more important than circumference in determining usable space; I use circumference because the area of a circle is the most one could hope for as an optimum comparison. Yes, once vessel shape becomes elliptical or beyond it looses volume, but I have a “what if” the SID shapes may enhance velocity and control directional stability. What is considered an “improvement” by increasing area can sometimes kill flow; Roland would agree with that statement by itself.

 

I mean that the shaft going across the throat of the TB blocks airflow more than a simple measurement of the area blocked by the shaft. The presence of the shaft perturbs the flow. For a 58 mm TB throat with a 6 mm shaft going through it, the actuall unblocked area is ~2640-348 mm^2, or around 2300 mm^2. But because of pertubations to flow around the shaft, it actually flows less than this, to the tune of a bit less than 2000 mm^2.

FWIW, I guessed at the shaft diameter, but this would give a effective diameter a bit larger than 50 mm, even though the actual open area is the same as an open bore of about 54 mm.

A lot can go into flow design to improve mass transport over what would be created by a simple circular cross section. The D shaped exhaust ports are a perfect example of this, where the long side of the D is on the inner radius of the curve of the duct. But in looking at the SID, it sure seems like it was designed more based on "space available" than on "flow optimization". Either detailed modeling would really be required, or some well controlled tests, to determine what is better.

Matt

 

Why are ya'll making me think of such things.. now im going to spend half the night re-designing that thing

 

Hey Matt do you have a heat gun and some free time? =P We ought to put a car build get together together...Jasons car is close to being running again...nikki still needs to install her aero kit...I wouldn't mind doing this mod and might be swapping someone my jcw head for their stocker.

 

Free time? Sure!

Matt

 

Actually, for non-circular flow channels like the SID the relevant factor is the open area divided by the wetted perimeter. This gives what is called the "hydraulic diameter", and is the usual way of calculating the diameter of a circular pipe having the same resistance to flow as the odd-shaped channel.