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southernstar · 05-02-2013, 04:24 AM

Pothole, you are suggesting (without any evidence) that Porsche changed the gearing on the 2.7 to improve fuel economy at the expense of performance. My point about the 981 was that, yes I agree that Porsche has made some changes in the Boxster for the purpose of improved fuel economy - e.g., electric steering and start/stop technology in its most recent model, and they have acknowledged that this was the principle reason for those changes. But I thought we were talking about changes made to the 986 Boxster series, where they made no such claim about the changed gearing that came with the introduction of the 2.7.

What is interesting about the gear ratios on the 2.5 as opposed to the 2.7 is that, while the ratios for the the first three gears are identical, the ratios for fourth and fifth gear are actually closer in the 2.7 than the 2.5. I assume you will agree that for the purpose of performance driving, a close-ratio gearbox is generally considered better (after a shift, it enables one to keep the engine RPM's in the sweet spot in the middle of the power band). Put in practice, a shift into fourth from third, or fifth from fourth in the 2.7 will drop the rpm's less than in the 2.5.

It is obvious that we will never agree on this point and that's fine. You say that Porsche changed the gearing solely for the purpose of improving fuel economy. You say that in spite of the fact that Porsche never made such claims and indeed, you offer no fuel consumption figures to prove that there was any such improvement. I say that Porsche introduced that 2.7 and 3.2 in order to improve performance and thereby address the biggest criticism of the 2.5 - that it was lacking in power, torque and flexibility. I am saying that Porsche altered the gearing in order to match and optimize it with the improved peak torque and horsepower as well as the flatter torque and horsepower curves that came with the increased displacement and improved fuel injection in the new engine.

While it is unclear whether Porsche improved fuel efficiency with the 2.7 (and I suspect they did not), it is clear from Porsche's own figures and from comtemporary tests that it did improve performance over the 2.5.

Cheers!

Brad

05-02-2013, 04:24 AM	#32
southernstar Registered User Join Date: Apr 2012 Location: Ontario, Canada Posts: 598	Pothole, you are suggesting (without any evidence) that Porsche changed the gearing on the 2.7 to improve fuel economy at the expense of performance. My point about the 981 was that, yes I agree that Porsche has made some changes in the Boxster for the purpose of improved fuel economy - e.g., electric steering and start/stop technology in its most recent model, and they have acknowledged that this was the principle reason for those changes. But I thought we were talking about changes made to the 986 Boxster series, where they made no such claim about the changed gearing that came with the introduction of the 2.7. What is interesting about the gear ratios on the 2.5 as opposed to the 2.7 is that, while the ratios for the the first three gears are identical, the ratios for fourth and fifth gear are actually closer in the 2.7 than the 2.5. I assume you will agree that for the purpose of performance driving, a close-ratio gearbox is generally considered better (after a shift, it enables one to keep the engine RPM's in the sweet spot in the middle of the power band). Put in practice, a shift into fourth from third, or fifth from fourth in the 2.7 will drop the rpm's less than in the 2.5. It is obvious that we will never agree on this point and that's fine. You say that Porsche changed the gearing solely for the purpose of improving fuel economy. You say that in spite of the fact that Porsche never made such claims and indeed, you offer no fuel consumption figures to prove that there was any such improvement. I say that Porsche introduced that 2.7 and 3.2 in order to improve performance and thereby address the biggest criticism of the 2.5 - that it was lacking in power, torque and flexibility. I am saying that Porsche altered the gearing in order to match and optimize it with the improved peak torque and horsepower as well as the flatter torque and horsepower curves that came with the increased displacement and improved fuel injection in the new engine. While it is unclear whether Porsche improved fuel efficiency with the 2.7 (and I suspect they did not), it is clear from Porsche's own figures and from comtemporary tests that it did improve performance over the 2.5. Cheers! Brad