Again for your reading pleasure
http://www.gnttype.org/techarea/turbo/turboflow.html
http://www.turbobygarrett.com/turbob...Tech%20103.pdf
http://www.superstreetonline.com/tec...e/viewall.html

 

Found this on stumbleupon.com at work a couple months ago. It actually talks about the "twin-scroll" turbo that is found in the Mini.

http://www.stumbleupon.com/su/1JJFCW...uction_3.html/

 

Page 2

 

In that article under "2-Stage Variable Twin-turbo" the diagram has a part label "LLK" do you know what this means?

 

"Average" boost will be approximately 0, i.e atmospheric pressure, no boost at all. That's because the ECU manages the wastegate to only boost when necessary. I have done a fair bit of datalogging with Torque on the street and track and also watching my boost gauge, unless there's demand for increased power output, boost is zero. Driving at constant speed on a flat road, boost is zero.

Maximum boost will be 11-13psia (psi above ambient, ambient = 14.7psi at sea level) unless you get a tune, because the only way to change this is to change the ECU control of the wastegate.

Getting rid of the muffler on the turbo discharge pipe and a larger FMIC will theoretically allow a bit better flow and deliver more air to the engine for increased HP, Alta has dyno charts that show this. But without a tune the gains are small. The other thing a larger FMIC will do for you is keep the intake air temperatures lower under boost, so you get denser air and therefore more HP. My datalogs show that the only place this matters is on the track, on the street you just can't drive that hard for long enough to get the IATs up. Unless you live in Phoenix or Death Valley and have ambient temps above 100F.

 

Does any one know what the real purpose of that "muffler" is? I just have a hard time believing that the engineers would install a part that muffles the sound at the expense of performance/efficiency (albeit small) and then turn around and install a noisemaker somewhere else.

 

LLK is short for Ladeluftkühler which in German is Intercooler

 

My guess is it is all about managing the frequencies - the muffler takes off the high end, the noisemaker (happily not present from 2012 on) was for letting the lower frequencies into the cabin. Personally, I don't notice any difference in sound with/without the muffler, but my ears are getting old.

 

ignore this message

 

And thank you everyone for the wonderful articles, this is why i love these forums . So correct me if im wrong, but you are saying that you only get boost when really driving the mini hard such as pedal to the metal acceleration and high speeds?

 

 

Okay to make boost simple- When your car idles, it'll read around -20 psi vacuum. Now when you begin to drive normal/crusing. Your car will pull 0psi or 14.7psia- which is what ambient pressure is. When you get on the gas harder(doesn't need to be WOT right of the bat, progressive throttling)and you begin to get the turbo to spool faster an faster until the turbine begins to force air into your intake manifold faster than the motor can let in, you begin to pressurize the intake manifold. This is what we call boost. Literally, you'll feel a spike of power!

Now I'll try to explain why any aircharge/cai/piping isn't a boost adder without a tune. Your engine ECU will control boost using a wastegate. The more air you try to bring onto the "cold" side of the turbo, the higher your wastegate duty cycle will be, so all that precious air you tried to put into your motor is just getting exhausted.

Get a tune with those mods, turn up your boost parameters via ECU. Then you'll get your moneys wortH!

 

Okay that does make sense, so replacing oem tubes with aftermarket tubes such as NM or ALTA doesnt necessarily add boost but it can handle higher boost situations (please correct me if im wrong). So i guess one of the most performance adding mods you can get is an ecu tune which will also take advantage of any other mods you add (cai, discharge and charge tubes etc etc). Okay, thank you everyone

 

Think of it this way - it's like blowing through a straw. Your turbo can blow through a thin, constricted straw (discharge pipe muffler and stock FMIC) or it can blow through a fat, wide open straw. Boost pressure gets measured at the intake manifold, the ECU will manage maximum boost the same, but there will be some performance gain without a tune as you'll be able to build boost faster as the turbo is blowing through a fat straw instead of a thin one. Also a larger FMIC will keep the boosted air temps lower, therefore denser so more air to mix with fuel.

 

Putting that on a MINI wouldn't get you any boost. And do you know what that is used for? My first guess is aviation but it could be for a large ship engine

http://www.boatdesign.net/forums/die...l-34881-2.html
EDIT: Post 21 , and take a look at the wiki article on post 1

Because f*** logic, thats why

 

Kinda right, which my response will be also - entire textbooks are written on this topic. Fatter straw = more volume to pressurize = more mols of air = more turbo lag. Smoother passages, less bends though will decrease drag and increase efficiency. Larger flow area will decrease velocity which will help with efficiency.

Low drag intakes and exhausts allow for efficient spooling which is good no matter what.

On cars that control boost levels mechanically, increasing charge density increases power (to a point - if you knock they generally pull timing advance). In these minis, the ecu seems to manage air input via varying the boost. I plan to investigate this more (only had my mini for 6 weeks) as boost levels are not consistently applied in my 2010. I get anywhere from 12.1-14, all at WOT and across all gears and seems to be external condition dependent. More logging is needed for me to understand what is happening.

 

I remember reading somewhere on another thread that it goes to a certain manifold absolute pressure-- something like 33 psi

 

BOOM!!
you can boost the psi with a tune....
But as many folks found out with overly aggressive custom tunes or "stage 3 canned tunes" the pistons...or more appropriately the skirts around the rings fail at high boost levels....
Engineers speed months calculating exactly how strong to make parts so they can be made as cheaply and lightly as possible.... General rule is you can go a bit over stock....but much more....you start to need custom pistons.....

 

+1,000 times true.

Sucks but true.

 

Your point about more volume is correct, though since the turbo is capable of much higher boost levels it can fill that added volume fast enough that there isn't any significant increase in turbo lag.



The N18 manages both boost and intake valve lift/duration to control the air input. I'm still working on understanding the details of how that interacts with the MAP and MAF and fuel metering.