| pgfpro |
12-10-2013 01:39 PM |
Quote:
Originally Posted by oil pan 4
(Post 402519)
Turbo gas engine have to run a lower air/fuel ratio so they don't destroy them selves. Your typical lowest N/A gas motor air/fuel ratio is between 12.5:1 to 13.2:1. A turbo charged gas engine can hit 10:1 or 11:1 during normal operation under demand for more power and there are several reasons this must happen.
Diesels are totally different and do not have to come any where close to gas engine air/fuel ratios for any reason.
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Cooling combustion temps by means of running rich for knock control is kinda a thing of the past. Even the Ecoboost F-150 3.5L twin turbo engine runs at only 13.5 A/F at peak torque.
One of the main reason GDI engines were built was to run at a leaner A/F ratio to improve BSFC to help improve fuel efficiency. GDI engines utilize the boost to lower combustion temperature (valve overlap, cycling air only) and add the fuel much later in the cycle to prevent knock. This also makes the GDI engine able to run a higher compression ratio that improves efficiency. Plus the GDI fuel atomization is much higher then what we see in today's PI engines.
The new valve seal and valve guide technology will help with particulates emissions. But keep in mind the problem is the oil getting past the valve guide no matter what engine it is, GDI, PI or Diesel. This oil will be burned in all three types of engines. The cleaning of PI injection might keep the valve clean and prevent intake valve soot build up but the oil is still being burnt.
IMO the problems were seeing with the Ecoboost engine is more of a combination of the above intake valve soot build up and the EGR system.
No matter what the GDI technology is here to stay and all the major manufacturers are going this direction.
I have a good friend that owns a F-150 Ecoboost truck that is at 80K now with no problems at all, so its not all the Ecoboost engines that are having these issues. |
