Premium fuel for turbos!

Post by **northernlights** » 26 Sep 2014, 08:18

This isn't Volvo specific, but here's a really interesting quote from Edmunds review of the 2015 2.3 Ecoboost (i.e. turbo) Mustang:

http://www.edmunds.com/ford/mustang/2015/road-test1.html

It's an interesting option, generating 310 horsepower and 320 lb-ft of torque while delivering better fuel economy than the slightly less-powerful entry-level V6 offering....

There is one catch, however: the EcoBoost engine needs premium fuel to deliver its peak horsepower ratings. Put in regular gas and the EcoBoost can only muster 270 horsepower, although its torque output remains unchanged according to the engineers at Ford.

This is from a 9.5:1 engine, with about 1.2 bar boost during acceleration peaking at 1 bar at redline.

That's a huge loss of horsepower! I'm a premium fuel buyer for any performance engine, so I'm a little biased in favor of good gas even without knowing details like this, so that's all my 94 Turbo burns.

Post by **rmmagow** » 26 Sep 2014, 10:26

This phenomenon is primarily caused but the knock sensors right? They dial back advance when sensing knock. I know my V70 has a sensor, but how about early turbos, maybe before high end ECUs were in use? They'd benefit a lot from premium fuel and using crap gas can actually damage them due to knock. My v70 runs OK on mid-grade (91) but I don't run a tune. Premium does feel better but I'm not sure if this is real or just because I want to think it made a difference because I paid a 20 cent premium for it. I put a tank of regular in it once due to zero gas and the station had no better available, car ran like crap, felt like the e-brake was dragging.

Post by **matthew1** » 26 Sep 2014, 11:00

Engineers can do anything they want with engine management now. I suspect this huge drop in hp is fully intended. They've got warranties to honor, so as an engineer, I'd want this huge margin. There is crap gasoline out there. Old, water, etc.

But yea, it's a shocking difference however you try to explain it.

I'd also suspect it might be a low "sample" data point. Test a hundred more and you'd find the average hp drop w/ 87 octane to be less drastic than this. Just a hunch.

Post by **rmmagow** » 26 Sep 2014, 11:59

I had an old Mazda 929 and a test for the knock sensor involved tapping an area of the block with a ball-peen hammer and watching the timing marks change. It was pretty obvious watching that happen on that motor.

Post by **northernlights** » 26 Sep 2014, 14:35

matthew1 wrote:Engineers can do anything they want with engine management now. I suspect this huge drop in hp is fully intended. They've got warranties to honor, so as an engineer, I'd want this huge margin. There is crap gasoline out there. Old, water, etc.

But yea, it's a shocking difference however you try to explain it.

I'd also suspect it might be a low "sample" data point. Test a hundred more and you'd find the average hp drop w/ 87 octane to be less drastic than this. Just a hunch.

You are absolutely correct regarding the degree of control available from engine management. And on that note...the more I think about it, it's funny that the claimed torque is the same at reduced power. I wonder how much they are limiting it via engine management to make sure it doesn't step on the V8's toes!

brad850 · Post by **brad850** » 27 Oct 2014, 12:27

I swear by high octane. The higher cost is worth it, especially for a turbo and or high miles Volvo, I can tell the difference in performance and the fuel economy is a little better with high octane as well.

Post by **Ben850** » 27 Dec 2014, 16:41

brad850 wrote:I swear by high octane. The higher cost is worth it, especially for a turbo and or high miles Volvo, I can tell the difference in performance and the fuel economy is a little better with high octane as well.

I agree and go a little step further with every other tank full and add some octane boost/fuel conditioner to the 93 octane I always buy.
I spoil the cars, and it may be over kill but it makes me feel comfort in an area that is easily doable.

I must say, as a result of this regimen, my turbo and intake hoses appear clean, as well as my spark plugs. I realize these are not all related and it may be a placebo affect to me, but I know the octane level is not the cause of related issues.