Blow Off Valves - M6 S63TU?

[figgie]

Originally Posted by michel lane

When you are running turbo charged cars with cats as a stock setup, there are restrictions on the flow of gases out of the exhaust due to the restrictions. If you remove these restrictions then the gases will flow better , causing over boost . Over boost usually takes the fuelling map out of its optimum zone, it may cause the car to run lean or rich .

The piggy back ECU will increase the boost by fooling the Ecu on the readings. Depending on how much the map has been adjusted to compensate for over boost , you may fall into an area of the map which has more or less fuel or ignition timing .

Most cars will compensate for around 10% over boost , but when you combine increase of boost with de-cats you will get more boost, therefor falling into area's of the map where it is not running optimal.

People have this understanding that more boost creates more power , this is not that case when you are using a stock ecu with piggyback unless the fuelling and ignition has been reviewed. My knowledge with the bmw piggyback is very slim unfortunately as I am familiar with stand alone ecu such as motek ,Aem, syvecs.

Sometimes you gain more peak power but when you look at the map, you may be surprised that you are actually getting less power before peak compared to the stock setting .

Running lean causes higher EGT , which will cause hotter running engines therefore result in piston failures .
Maybe I am just to cautious , but from experience in the past with big HP cars , it works out better.

I would be exceptionally careful with that piece of advice.

AFR are post. at full tilt, it will not take but less than 1 second to pop that motor. AFR gauges whether wideband or not will be a reactionary device (ie the lean condition has to happen before it is picked up). At 600hp, you go lean, you MIGHT get lucky to take your foot off the throttle intime to prvent something. I kindly label such devices "explosion detectors". Why? well, when an explosion happens, not only do you know but everyone else. It is definetly a post event sensor.

with that said, The Bosch EMS are some of the most sophisticated EMS in the world.

I am talking about 4 dimensional maps and probably more. The change of going lean due to turbo overspeed is for the most part nonexistent as the car is measuring the air in through the hot film air mass meter. In other words it knows exactly how much air is gulped by the engine at ANY given time (that includes load, TP % etc). Deleting exhaust restrictions will only move the VE% in a different "cell" with minor adjustments done through the closed loop cycle with the Wideband O2.

at full boost.. 11.5 ( I prefer lambda as that is across the board and in 11.5 afr translated to around lambda .85) is as high as you will want to go. 12.5 is asking for trouble. Now if you are lucky enough to be able to handle e85... 10 (lambda = .7) is the magic number.

Originally Posted by Michael lane

The bmw has 2 narrow band lambda sensors before the cats , I would weld the wideband further down the stream of the lambda sensor.

Michael,

I know you mean well but this is easily searched.

The engine has one Wideband sensor (The LSU ADV) which is pre-cat and one narrow band (also known as switching) LSF4.2 which is the monitor (in between the two ceramic substrates of the cat).

http://aa-boschap-de.resource.bosch....magefolder.pdf

page 7 for the LSU ADV, page 5 for LSF