[roland2003]

Hi Guys, just been playing around with the plastic plenum that is between the throttle body and the SC inlet. As some of you know there is a severe flattening of this pipe just after the bypass valve inlet. The cross sectional area at this point is quite small and certainly less than that of a 63mm or 57mm throttle butterfly that preceeds it. This results in a partial vacuum at the SC inlet (not good)even at full throttle (Andy Ross has a nice graph to prove this). Even with the least restrictive air filter system ( GTT Cold Ram ), you still only get around 1.5psi below atmospheric..
Yes you can get a metal replacement but these guys only achieve 16psi max at the inlet manifold.(everyone who achieves more is wrong apparantly) Holy smoke my car achieves near 20psi on a 17% pulley with the stock plastic plenum.(Plus GTT Intercooler and Induction Kit -;makes quite a difference to the boost as you can see)
What I've discovered is my heating the plastic it can be re-shaped by squeezing with grips across the widest point & at the same time pushing the bottleneck out with a bit of broom handle . I would guess the cross sectional area at this point increases by around 30%.
More than enough I think, I have yet to try it on the car but if we get 1psi nearer ambient , (WOT 6000rpm) at the SC inlet, we will get more boost at the inlet manifold too plus better efficiency.
The mod is totally discrete &cheap too, well free if you do it yourself.
Best Regards Roland GT Tuning

[62Lincoln]

Roland, you've got to share your results once you have a chance to try it on the car. This would be an amazing upgrade if it works as you expect....

[ChocolateAZ]

Yes, please share!! An easy fix/mod that we can DIY with little or no $$.

[MINI-Morgan]

Sounds like a good idea! Will certainly be interesting to see the difference.

[RedUn]

sounds good, lets have some results

another thing thats interesting, have you got any flow figures for the air filters on the market showing how they compare to the GTT one??

[flyboy2160]

roland, you need to measure the circumference before and after. if the circumference hasn't changed, you haven't changed the area, just the shape.

"you may ignore the laws of physics, but the laws of physics never ignore you."

and isn't it flattened to allow for clearance when the engine moves? have you checked the clearance?

[Mike Edwards]

My maths isn't being helped by a week of not thinking hard plus too much to eat and drink, but I'm fairly sure that the cross-sectional area of a tube increases as the section gets closer to circular?

[bimini]

not if the radius is reduced in one direction by the same amount as its increased in a another

however flow is better on a more circular area over a less circular area of the same amount for most applications.

[roland2003]

FLYBOY Blimey you must think Im retarded, So every conceivable shape that has the same distance around the perimeter has the same area within? I dont think so.
As one of a million examples, take a rectangle 1cm by 10cm, the distance around the perimeter is 22cm & the cross sectional area is 1 times 10 which equals 10 sq cm.
We then 'remould the shape ' to make a new rectangle 5.5cm by 5.5cm,this still has a distance around the perimeter of 22cm yet the new area is 30.25 sq cm . Thats over 300% of the original !
Or to take it further lets remould the shape to a circle, the circumference is still 22cm the area using pi now increases to a whopping 38.5 square cm. This is 380% of the original .
Only if a shape is a perfect circle can you not improve on the area for a given perimeter.
No part of the original stock part (apart from the first inch) is any where near circular.
The restrictive creases in the stock part are for clearance to the rad & SC. have found I can still get a double decker bus sideways through the gaps after modification.
I have now completed the mod, car definately feels quicker, but I will hook up a vacuum gauge to the SC on the connection just before the rotors to get a reading(where the PCV valve normally connects). My guess is with GTT Cold Ram + GTT 63mm throttle+ GTT 'reformed plastic plenum' even at 6500rpm using a small SC pulley (ie alot of suck) at WOT it will never go lower than half a psi below atmospheric. If I achieve 1psi below atmospheric thats bloody good going.

Regards Roland GT Tuning
ps When I have time and 2 old units , I will hacksaw them in half where the crease is/was, draw aroound it onto '1mm square graph paper', then count the squares within the shapes .Next divide the number of squares on the modded example to the number of squares on the stock to get the % increase cross sectional area.

[flyboy2160]

apologies roland,
i must be brain dead from the holiday! i may edit/delete the post so as not to mess up your thread.

[roland2003]

Its ok, actually you had me thinking too. And I think it has brought to light some good points .Regards Roland GT Tuning.

[62Lincoln]

Roland, might it be a good idea (if your testing confirms the improvement) to offer modified tubes on an exchange basis? I can envision 10 different people getting 10 different results when they do this themselves, but everyone could be assured that the mod had been done properly if you were the supplier. My 2 cents (an American, you know ).

[roland2003]

Hi Lincoln, yes thats the way Im thinking too. What we would do is sell them either (1)'new/GTT modded outright purchase or (2) 'Used/ GTT modded exchange'. In practice I think we would end up selling new outright mostly as firstly they are not that expensive from BMW (IIRC about £30 ish) .Also they wear away/break out the hole on the fixing lug eventually. Interestingly they seem to vary as to the extent of the first restriction ,(ie the one nearest the TB) , the second more severe flattening is bad on all 3 that I have inspected this closely.The only downside to the mod is its about 3-4 hrs labour, unless the front of car & SC is coming off anyway
Regards Roland Gt Tuning

[62Lincoln]

Well in my case I have a modded s/c that is waiting to be installed, so I would be in a position to have this install done at the same time the s/c is installed. Please keep me in mind, and PM me once you are satisfied that this mod produces the results you expect. I will gladly be one of the first to buy this once you are satisfied with its results.

[roland2003]

OK Lincoln will do.
Regards Roland GTT

[-=cHiLli=-]

For those of us reading this, but havent got a clue what you are talking about, cold you post some pics, ie pipe location in car and before and after shots of modded pipe...

thanks,

mD()

[roland2003]

OK will do (tommorrow) . BTW can some clever person let me know (in detail) how to post a full size pic that 'comes up with the text'. I can only do the 'attached thumbnails' which only permit very small files & make everything look a bit crappy. Please PM me .
Thanks in advance. Roland GTT

[Wobert]

Quote: Originally Posted by roland2003

FLYBOY Blimey you must think Im retarded, So every conceivable shape that has the same distance around the perimeter has the same area within? I dont think so.
As one of a million examples, take a rectangle 1cm by 10cm, the distance around the perimeter is 22cm & the cross sectional area is 1 times 10 which equals 10 sq cm.
We then 'remould the shape ' to make a new rectangle 5.5cm by 5.5cm,this still has a distance around the perimeter of 22cm yet the new area is 30.25 sq cm . Thats over 300% of the original !
Or to take it further lets remould the shape to a circle, the circumference is still 22cm the area using pi now increases to a whopping 38.5 square cm. This is 380% of the original .
Only if a shape is a perfect circle can you not improve on the area for a given perimeter.
No part of the original stock part (apart from the first inch) is any where near circular.
The restrictive creases in the stock part are for clearance to the rad & SC. have found I can still get a double decker bus sideways through the gaps after modification.
I have now completed the mod, car definately feels quicker, but I will hook up a vacuum gauge to the SC on the connection just before the rotors to get a reading(where the PCV valve normally connects). My guess is with GTT Cold Ram + GTT 63mm throttle+ GTT 'reformed plastic plenum' even at 6500rpm using a small SC pulley (ie alot of suck) at WOT it will never go lower than half a psi below atmospheric. If I achieve 1psi below atmospheric thats bloody good going.

Regards Roland GT Tuning
ps When I have time and 2 old units , I will hacksaw them in half where the crease is/was, draw aroound it onto '1mm square graph paper', then count the squares within the shapes .Next divide the number of squares on the modded example to the number of squares on the stock to get the % increase cross sectional area.

One thing to consider is the "hydraulic area".......perimeter vs cross-sectional area.

A circle offer the maximum area for minimum perimeter. The losses through surface friction on the runner will be minimised.

Deviate from this and any gains made from increasing the cross-sectional area will be partially negated by the increased friction of air against runner wall.

Another thing to consider progressive changes in section, balancing areas before and after any deviation.

[obehave]

Quote: Originally Posted by roland2003

OK will do (tommorrow) . BTW can some clever person let me know (in detail) how to post a full size pic that 'comes up with the text'. I can only do the 'attached thumbnails' which only permit very small files & make everything look a bit crappy. Please PM me .
Thanks in advance. Roland GTT

You need to post from a url link


You use the little icon at the top of the post pagethat looks like a postage stamp with mountains on it.

The code will look like this except with brackets instead of braces {IMG]http://www.mini2.com/galleries/data/670/medium/54724.jpg[/IMG}

The end result is this:

[Tonyt3]

Quote: Originally Posted by roland2003

OK will do (tommorrow) . BTW can some clever person let me know (in detail) how to post a full size pic that 'comes up with the text'. I can only do the 'attached thumbnails' which only permit very small files & make everything look a bit crappy. Please PM me .
Thanks in advance. Roland GTT

Upload the photograph into your Gallary - use the Gallaries link at the top of this page. When you load the picture up, it will give you a html link that you can cut and paste into your post.

Sure there must be other ways, but this seems simplest to me.....