[chiefsotos]

I am running the natural aspired mode two days now and although the sound is awesome(very deep!!), the exhaust fumes smells a lot.
I have catless dps but from there and back, the stock exhaust with the second cats on and even if i parked the car, turn it off and get out, i can feel the smell for a few secs.
It smells like a more fuel in the air/fuel ratio, but doesn't the NA mode supposed to be more economical with less fuel in the air/fuel ratio???

[MF80]

So, you are saying you smell unburned fuel?

[MF80]

Also, did you feel MPG improvement compare to the boosting mode?

[Transport3r]

Yesterday I had my car actually backfire on NA Mode lol.

NA mode:
Ambient temp 62-63F
10.2 mile distance at 80MPH on cruise
27.0 MPG (Average over the 10.2 miles)

Map1:
Ambient temp 64F
10.6 mile distance at 80MPH on cruise
28.3 MPG (Average over the 10.6 miles)

This test is irrelevant however, since I was unaware that the trip computer will read low in NA mode.

[vasillalov]

Your trips are too short to accurately measure the fuel efficiency. Don't trust the car computer to measure your fuel efficiency.

...and just so you know, my N54 smashes your fuel efficiency EASILY. I get around 30-32 mpg when cruising @ 70-80 mph and gets up to 32-34 mpg when I nanny it down to 55-60mph.

[Clap135]

You have to manually calculate your gas mileage. When I used NA mode for an entire tank, my trip computer read 23.5, actual was 26.8 when i divided miles over the distance travled. Shiv did mention somewhere that when in NA mode, the mpg calculations the ecu processes are wrong.

[OpenFlash]

Yep, the MPG reading is inaccurate in NA mode since we remap fuel pressure and DME perceived boost. On a 1hr cruise (light throttle), NA mode indicated 27mpg. Actual was 32mpg.

Also, AFR is similar to stock. Which is stoich at idle/light cruise. You can even monitor it on the dash. Nothing rich about it.

If you are running catless, that explain the smell. I suppose you may smell it a bit more at idle since your exhaust pulses are stronger as less of the exhaust is channelled through the turbine. That is also why your exhaust note is deeper.

Shiv

[Transport3r]

Originally Posted by shiv@vishnu

Yep, the MPG reading is inaccurate in NA mode since we remap fuel pressure and DME perceived boost. On a 1hr cruise (light throttle), NA mode indicated 27mpg. Actual was 32mpg.

Cool! I retract my statement!

Originally Posted by vasillalov

...and just so you know, my N54 smashes your fuel efficiency EASILY. I get around 30-32 mpg when cruising @ 70-80 mph and gets up to 32-34 mpg when I nanny it down to 55-60mph.

Good for you.
...and just so you know, there's a big difference in drag between 70 and 80 MPH. At 70, the Reynolds # of your flow drops by 12.5% compared to a 80MPH flow. Seeing that drag is proportionate to the square of your velocity, you'd see about 23% less form drag at 70 compared to 80. (Not taking into account friction effects.)
So yea, your N54 at '70-80' will smash mine at a constant 80.

[Proper Motion LLC]

Does cruising at 70mph in NA mode really improve MPG vs cruising at 70 regularly? I highly doubt it

[OpenFlash]

Originally Posted by Rysandro

Does cruising at 70mph in NA mode really improve MPG vs cruising at 70 regularly? I highly doubt it

There are slight improvements to pumping efficiency by keeping the wastegates fully open. NA mode also adds a timing bump during cruise. And up to 10 more degrees of advance at higher throttle angles.

Shiv

[Mike@N54Tuning.com]

Originally Posted by Rysandro

Does cruising at 70mph in NA mode really improve MPG vs cruising at 70 regularly? I highly doubt it

Typically turbochargers slightly improve efficiency by recycling some of the heat energy that would be otherwise lost out the tailpipe. If leaving the wastegates fully opened improved economy BMW would definitely do it. Small improvements to fuel economy can add up to millions of dollars in various fleet mileage incentives for them.

Mike

[OpenFlash]

Originally Posted by Mike@N54Tuning.com

Typically turbocharges slightly improve efficiency by recycling some of the heat energy that would be otherwise lost out the tailpipe. If leaving the wastegates fully opened improved economy BMW would definitely do it. Small improvements to fuel economy can add up to millions of dollars in various fleet mileage incentives for them.

Mike

Leaving the wastegates fully opened during cruise has a very obvious effect on low end boost response. Which is why BMW doesn't do that. Interestingly enough, they tried doing that with the wastegate rattle DME software "fix" and we all know how that worked out for them.

Under boost, turbos have fuel economy benefits compared to larger displacement engines pumping the same mass airflow due to a reducing in recipricating mass/fraction (less moving parts, less surface contact) and, as you mentioned, "recycling" heat from the expanding exhaust gases. But this is only under boost when compared to engine making the same power with larger displacement.

Shiv

[chiefsotos]

Originally Posted by shiv@vishnu

Also, AFR is similar to stock. Which is stoich at idle/light cruise. You can even monitor it on the dash. Nothing rich about it.

If you are running catless, that explain the smell. I suppose you may smell it a bit more at idle since your exhaust pulses are stronger as less of the exhaust is channelled through the turbine. That is also why your exhaust note is deeper.

Shiv

Glad to hear that a/f ratio is like stock, because of this bad smell i wondered if an extra unburned fuel goes to the second cats (which i have) and damage them more.

Can we earn in fuel economy, by making, in NA mode, the a/f r leaner than stock? Also we wont have that bad smell. (it's really really bad)

[OpenFlash]

Originally Posted by chiefsotos

Glad to hear that a/f ratio is like stock, because of this bad smell i wondered if an extra unburned fuel goes to the second cats (which i have) and damage them more.

Can we earn in fuel economy, by making, in NA mode, the a/f r leaner than stock? Also we wont have that bad smell. (it's really really bad)

There is no "unburned fuel" to speak of. Or at least there shouldn't be if your AFR is stoich (~14.7:1) at idle. You can see this in your in-dash AFR gauge. At idle it should point mostly to the middle of the gauge with the car fully warmed up.

[chiefsotos]

I checked it yesterday. The Afr in the oil gauge until 4000rpm was ~15:1 and until 6000rpm is ~ 13:1, so it's not rich at all.
Who knows maybe the low outside temperatures (-2c) make the car smell so bad especially if it hadn't warmed up.