Quote:
Originally Posted by cbaber
Many current Honda engines use lean burn, especially outside the US. Lean burn is not limited to the 5th and 6th gen Civics. For the 7th generation Civic both the HX and EX engines are lean burn, despite the EX being the more powerful trim. The EX engine is the same in almost every way to the HX engine, with minor ECU and gearing differences that account for the difference in horsepower and fuel economy. Both engines use a VTEC-E system just like on the HX and VX of earlier generations. During low load, low RPM driving one intake valve is closed and air/fuel mixtures are leaned out. When VTEC activates it switches to a normal cam profile using all 16 valves for more power. The EX has a more aggressive cam profile than the HX, allowing greater horsepower.
Beyond the 7th generation Honda developed i-VTEC which combines all the features of all the previous VTEC versions, including VTEC-E. In i-VTEC engines the ECU can control valve timing and lift, allowing some i-VTEC engines to run in 12 valve mode and achieve lean air/fuel ratios. It's important to note that i-VTEC dramatically reduces pumping losses experienced at low load, low RPM operation. This alone increases fuel economy compared to a normal engine.
I'm not sure if the TL or other i-VTEC motors have a lean burn mode, but I know the technology exists in some i-VTEC motors like the 1.3 i-VTEC. VTEC-E has not gone away, it's just implemented in a different way.
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The particular TL i'm talking about is a 2003 model. It's just a VTEC system, you can actually hear the crossover at 4500rpm. below 4500rpm it seems to always be operating low lift cams. Again experimenting with the LBN gauge, i have only seemed to be able to get really low values like 15s at 50mph cruising only.