3.0 liter sidi poor fuel mileage

[redonetoo]

Anybody have any suggestions on trying to get the fuel mileage up on a 2010 Terrain with 3.0 liter sidi. You would think with all the tech. in this engine it should be able to get more than 20 mpgs. I have the v2 flash and tune. I am new to this whole tuning thing so I apologize for my ignorance.

[swingtan]

There is no tuning support for the V6 yet, so it's going to come down to...

• How the car is used.
• The fuel being used.
• Driving style

You may be able to adjust the auto settings though and that can help with mileage.

Simon.

[GMPX]

Actually Simon, we do support the 3.0L and 2.4L SIDI as used in the Terrain, it uses an E39 ECM.
Redonetoo, I think the problem comes down to the weight of the vehicle, getting all that mass moving with a small engine takes a lot of effort. If the Terrain has an instant MPG readout take a look when you take off from the lights. I've only just started playing around with the 3.0L V6, but so far the fuel economy is about on par with what I thought it would be (11.5 L/100), which is about 20MPG. I would expect about 26-27 MPG on the highway.

[redonetoo]

I am looking at the short term fuel trims and they seem to always stay in they negative. Also the o2 sensors seem to run constantly around .750 volts. Which makes me think it is rich. I have changed the gear ratio in the transmission to 3.39 to help with the weight factor. Just in my mind it makes no sense that an engine of this size gets close to the same mileage as a v-8. I had a 2000 5.3 in a full size truck that got 18.

[redonetoo]

It does have the instant mpg feature. And you are right it does seem to drop quickly. But even at light acceleration on the highway it drops hard. I thought the advantage of the sidi was to more accuratlely control fuel timing. They have the injection timing at 300 degrees or so before tdc. So how is this better than MFI? I was told I could play with the MAF settings to help with the running rich. Like I said I am new to this.

[redonetoo]

This car has never seen 26 mpg. I went to Greenville NC from raleigh the other day all interstate 19.5 mpg. After I reset the trip.

[GMPX]

Again, it's how hard the 3.0L needs to work to get the vehicle moving, a 6.0L GenIV will move a 2 tonne vehicle away from the lights with ease, maybe shift at 2,200RPM at moderate throttle. Your 3.0L has to work twice as hard as the 6.0L, rev a little harder etc, if it's working hard it's got to use more fuel. At speed the 3.0L should do pretty good though.

SIDI allows them to have far higher compression, the LF1 is up at 11.7:1 from memory, that's race gas levels from days gone by. Injection timing is probably not something you want to 'experiment' with, GM would have spent a long time getting that timing right.

[redonetoo]

Even at idle the o2 sensors are running close to.750 is this normal? I live in Eastern North Carolina flat land. And most of her driving is interstate 75 to 80 mph. We had a Mariner it got 26 mpgs average with a 3.0 liter. The Terrain is much heavier. I just don't see the advantage of the sidi.

[redonetoo]

Another thing this Short term trim thing. It seems to stay in the negative numbers. Is that normal?

[redonetoo]

I work on Diesel truck engines. We can advance and retard injection timing at different rpms to get better performance. But if not careful you can melt a piston. I was just amazed at the time at which they were injecting fuel. The are injecting on the intake stroke instead of on compression stroke. I guess with gasoline that would be impossible.