Doing my daily, predictable 20 mile commute this morning I decided I needed some extra exhaust noise to supplement 'normal' mode driving so I pressed the PSE button and was surprised to see at least 2 mpg greater economy than usual... As I say this is a very predictable drive so i know my usual mpg over the 4000 or so miles of this commute is 28mpg and I was up at 31 mpg today (UK units). The drive is mostly 50-70mph limits so no hard acceleration except a few spots of fun between speed limit changes and junctions.

I wasn't 100% sure if my 'style' was a factor so I did the same again on return journey and hey presto... Another 2mpg extra...

As you can probably tell from this and previous threads I do like to know what fuel economy the car can achieve because a) it is my daily driver b) I'm European c) I like to know that after owning several high perf cars that this one is so much more flexible as a DD yet delivers a far more exhilarating experience when the twisties come!

So here it is... Does the magic pse bypass reduce back pressure enough to create this refinery effect or is there another technical explanation or am I going mad?... I will continue with the experiment to get better statistical data over a longer period...

 

I would say yes that makes perfect sense that the exhaust would be freer flowing hence the better fuel economy!

 

Could the weather from today be a factor?

 

I did wonder that pvr.... Will keep the experiment going

 

I believe the PSE in my car causes it to be less fuel efficient.

I'm always on throttle to hear that glorious sound, I just can't help myself.

 

I wish somebody would post some back-to-back dyno graphs with PSE on and off. Porsche says it makes no difference, but I'd swear that low-RPM power delivery is smoother in my 3.4L 981 with PSE turned on.

 

Yes, yes and yes. Engines pump air. Anything restricting air going in or out restricts power. Things get tricky fast if you get into it in more detail, but that's the gist of it. In normal driving, part throttle, there's plenty of power, but the engine still has to work to move the air. The less restrictive, the less work, the more left for power, the higher the mpg.

 

what would you say your avg rev range was?

 

Hi larry...1500-2500 rpm with a few bursts of 7000 rpm but only short bursts.... Repeated today and got consistently improved mpg... Air Temperature and air pressure back to normal so thinking I can rule out density/temp etc.
I'm familiar (too familiar) with pipe losses though pressure differentials and acoustic silencers but I am not familiar with the exhaust system construction on the 911 and I am surprised it has such a dramatic and measurable effect... In my technology field that improvement would equate to an overly restrictive std set up... Or a major innovation...
So it leaves me to wonder why I would ever NOT press that wonderfully acoustic button when I jump in the car... Unless of course I am 'with family' and have some listening to do

 

In theory the less restrictive exhaust will be more efficient. 2.0 MPG more? Not a chance in hell. If you could do a controlled test, the gain would be on the order of 0.1 MPG.

 

I'm amazed how a 430 HP car can get over 30 mpg on the highway. But I like it best when I'm getting about 12.

 

Exactly my thinking ... That was why I was surprised.

Lexvan - I couldn't agree more but as a DD I have little choice to blend the two!

 

I find selecting PSE helps a lot with having to do some "listening" - as a technical sort of guy, I'm surprised you haven't come across that yet!!

 

PSE is supposed to be a performance enhancing system. Therefore, by definition it cannot improve MPG. Anything that' s designed to boost hp cannot by definition improve economy. Period.

 

Period? Reducing pipe losses can improve performance AND reduce energy consumption in any pneumatic/hydraulic system. I was just surprised by how much. Key right