http://www.bimmerboost.com/ Advanced technical/tuning discussion and questions en Wed, 19 Jun 2013 17:25:11 GMT vBulletin 60 http://www.bimmerboost.com/images/misc/rss.png http://www.bimmerboost.com/ http://www.bimmerboost.com/showthread.php?40358-Questions-about-Spark-Timing-Advance&goto=newpost Sat, 01 Jun 2013 01:44:12 GMT So I have a question and I'm sure someone has a good answer. It involves spark timing, specifically spark advance for more power.

So, when I was learning about combustion engines in college, I was taught that the optimal point for a combustion chamber to achieve peak pressure after ignition is 15-20 degrees ATDC. I was also taught that an AFR or 12.5-13.5 is optimal for maximum flame front speed which results in more complete combustion.

When spark timing is advanced, the burn starts and ends sooner. in order to maintain peak pressure timing of 15-20 ATDC, a lower AFR must be used to slow down the burn. The idea is that more fuel burning longer increases the power, when in reality you're tuning the AFR to slow the flame front speed in order to maintain peak pressure being in that 15-20 ATDC range. The pressure in the combustion chamber reaches higher levels closer to TDC than a equivalent, non-spark advanced engine. this early pressure increase reduces efficiency due to the mechanical leverage the con rod has on the crank, which (im assuming, correct if wrong) increases the heat. produced.

My question is this, why not tune (retard) the spark to maximize the relationship between mechanical leverage on the crank (less pressure pre-TDC) and combustion chamber pressure? (Doesn't pressure buildup before TDC cost power?) All while keeping the AFR in the optimal 12.5-13.5 range (fast, efficient, complete burn of all the fuel). Wouldn't focusing on complete burn of fuel reduce the chances of knock due to less residual fuel being present from the previous combustion cycle? I feel like this would result in a smoother, more efficient engine.

Im sure there are holes in my logic here. I wont get upset if someone chimes in and says "you're full of $#@!" so long as they explain why. ]]> Advanced Tech DFM http://www.bimmerboost.com/showthread.php?40358-Questions-about-Spark-Timing-Advance http://www.bimmerboost.com/showthread.php?40239-We-need-this-now!!!!!-Performance-Acronym-definition-list&goto=newpost Wed, 29 May 2013 06:36:25 GMT All of this FBC, DCT, FOM, BBC, BBW, BDSM, etc stuff I can't understand all of this lingo. It's the 335i guys who are talking about these EBC's and whatever else. Can someone please make an acronym listing so I can understand wtf they're talking about? Everytime I click on a N54/N55 thread I have to open up google to understand what it is they're referencing. Thanks.

PS. Obviously, I know the basics.

FMIC= Front Mount Intercooler

DCT= Dual Clutch Transmission

JB= Burger Tuning stuff

But ISO, I had to google that one and some others. This may also help other people new to the N54 platform. ]]> Advanced Tech StinkyM http://www.bimmerboost.com/showthread.php?40239-We-need-this-now!!!!!-Performance-Acronym-definition-list