Discussions about gas direct injection (GDI) and the cooling effect on the induced charge
Discussions about gas direct injection (GDI) and the cooling effect on the induced charge
(OP)
Please use this thread and NOT the "Current Peak Cylinder Pressures" thread for discussion of GDI and it's impact on allowing higher static compression ratio, lower fuel consumption, etc.
Is best not to go off-topic on a thread so that those reading or desiring to contribute do not need to wade through a lot of discussion unrelated to the thread subject.
140airpower-
Why this "...There is no de-throttling or lean burn mode per se used in the VW VR6 model engines..."?
These expedients work for just about everybody else. It seems VW is leaving something (a lot!) on the table.
I do not know why VW and other auto makers have not changed to induction systems without a T/Body on PFI/GDI engines other than cost. For years BMW has used PFI systems without a T/Body but it is a complicated system and thus more expensive. With VW's sales volume many times that of BMW it apparently is not cost effective or a significant advantage at this stage of the game. There are pros and cons to lean burn mode. Each engine maker has to decide what strategy works best for their particular situation.
Is best not to go off-topic on a thread so that those reading or desiring to contribute do not need to wade through a lot of discussion unrelated to the thread subject.
140airpower-
Why this "...There is no de-throttling or lean burn mode per se used in the VW VR6 model engines..."?
These expedients work for just about everybody else. It seems VW is leaving something (a lot!) on the table.
I do not know why VW and other auto makers have not changed to induction systems without a T/Body on PFI/GDI engines other than cost. For years BMW has used PFI systems without a T/Body but it is a complicated system and thus more expensive. With VW's sales volume many times that of BMW it apparently is not cost effective or a significant advantage at this stage of the game. There are pros and cons to lean burn mode. Each engine maker has to decide what strategy works best for their particular situation.





RE: Discussions about gas direct injection (GDI) and the cooling effect on the induced charge
BMW Valvetronic (and Fiat MultiAir) can run without a throttle because of variable valve timing and lift, not because of GDI. They are more-or-less limiting the amount of intake charge by playing with valve timing and lift as opposed to shutting a throttle. Done properly, it reduces pumping losses. But make no mistake, the engine is still running stoichiometric air/fuel ratio (although with some EGR) in order for the 3-way catalyst to function.
I know of no current production spark ignition engines that are successfully using lean burn and complying with current NOx emission standards (US EPA Tier 2 or Euro 6).
As for the cooling effect on the intake charge ... Normal port injection involves squirting fuel against a closed intake valve and around the inside of the intake port, which draws heat mostly out of the cooling system (or the valve).
RE: Discussions about gas direct injection (GDI) and the cooling effect on the induced charge
Which is where technology like Mahle TJI comes in.
"The transition between very light engine load (when very lean burn and/or very high EGR is theoretically possible) and full torque output (when neither lean burn nor high EGR are consistent with getting decent torque out of the engine) requires passing through a somewhat-lean and low-EGR regime that produces very high engine-out NOx."
The future for lean burn tech (if there is to be one) is full-time lean burn - which means reduced peak power output - and must be offset by upsizing, 2-stroke operation or forced induction. Of these, forced induction would be most likely (as in current Formula One power-plants (with 50+% TE compounded)).
je suis charlie
RE: Discussions about gas direct injection (GDI) and the cooling effect on the induced charge
"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz
RE: Discussions about gas direct injection (GDI) and the cooling effect on the induced charge
je suis charlie
RE: Discussions about gas direct injection (GDI) and the cooling effect on the induced charge
"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz