Ferocity02

iTrader: (60)

Now I didn't expect my fuel economy to improve after the turbo, however, I did not expect my cruising fuel economy to get any worse. Before the turbo I would get 19-20mpg on the highway at 65-70mph, now I'm getting 12-13mpg. I can't think of why this is happening.

The narrowband O2's are showing that it's running at stoich because they are switching just fine. The wideband is showing around 14.4 AFR but it could be a bit off. Before the turbo I was averaging about 39 g/s airflow on the highway, now its about 44 g/s. So a little more airflow, but not enough to cause the decrease in fuel economy I'm seeing, IMO.

So if it's not running rich, and the airflow isn't that much higher, then I am stumped as to why the cruise fuel economy took a huge hit. I'm thinking it's probably something in the tune (still working on it with my tuner), but it just doesn't make sense

I don't think there are any exhaust leaks before the NBO2's, but there are some well after the downpipe. I'm running TR6 plugs gaped at 0.028". It's a 1 bar MAF tune with the stock OS (for now).

HRHohio

Did you do cam swap with the turbo add-on?

SPDKNGG

Could you post you data log? I would look at the injector scaling and or fuel load tables.

Ferocity02

iTrader: (60)

Cam swap was done a few months before the turbo, so I was getting the decent mileage with the cam.

Log attached. Injectors are 83# @ 4bar from FIC with their data in the tune. I'm using the stock manifold referenced FPR (this is a truck BTW).

LilJohn

That tune is still rich at light load part throttle if its 14.4.

95bowtie

Since we are on the subject what would a good cruising afr be on 93 and e85?

My wideband reads all fuels in gas scale so whatever is good for gas should be the same for corn right?

Sarg

iTrader: (6)

Typically 14.7 at cruise with no load if your wideband only reads afr. My guess is 14.7 on your wideband would be a lambda of 1.

HexenLord

How much did your IATs change? An intercooler at highway speeds can have a pretty good drop when compared to a poorly placed air filter in an N/A app.

Also, how high is your timing when cruising?

BMF_Racing

iTrader: (6)

When on the highway, is you cruising coolant temp the same as N/A?

Ferocity02

iTrader: (60)

But in closed loop shouldn't the NBO2's be aiming for 14.7 using the fuel trims? According to the activity of the NBO2's, it's not rich. I'm thinking my wideband is off, no surprise, it only "works" about 1/3 of the time.


Crusing IAT's are roughly 10F higher than ambient, before the turbo they were almost exactly ambient. Crusing timing is high 20's low 30's. Before the turbo I tested the cruise timing up into the 40's and it made no difference in fuel economy. The tuner brought it back down in the base tune I'm running now.


Yes, exact same.

BMF_Racing

iTrader: (6)

Hmm? ...Same tires and frontal area (mods for intercooler)? Tire pressure the same?

Ferocity02

iTrader: (60)

Everything is the same. If the drag went up, the engine airflow should go up as well. It did go up, but not by the same amount that the fuel economy went down.

The only thing I can think of is that there is an exhaust leak that is letting fresh air in before the NBO2's, so it thinks it's lean and adds fuel to trim it out. But exhaust leaks usually let air out of the exhaust not in, in my experience. I checked for leaks and didn't see/feel any.

FIC is sending me a fresh set of injectors and data to rule out the possibility of a faulty set of injectors. Talk about service!

Cam72aro

iTrader: (28)

That's some serious customer service on their part. Kudos to them.

Cam72aro

iTrader: (28)

What was your map sensor reading before and now after?

Ferocity02

iTrader: (60)

MAP didn't change at all with the turbo, still about 42kPa at idle and about 63kPa at cruise.

Sarg

iTrader: (6)

Fuel Injector Connection or Clinic?

Ferocity02

iTrader: (60)

Connection

SPDKNGG

Question...
How old are your O2's? and have they seen race fuel often?
im am reviewing your logs now..

SPDKNGG

Looks ok to me..more worried about WOT then come back and clean up the cruise and part throttle..

SPDKNGG

Typically turbo cars like 12.8-13.0 depending on the set-up. Only the dyno can really tell you what AFR's you engine makes the most power on. Plus you wanna be on the safer side. So it's always better to be a little rich than lean.