V6 gas mileage

[Pamaro]

Originally Posted by badgebunny

On the way to C5F I was getting around 26mpg avg (the camaro's number) on the way back driving with the cruise set the same way we were getting 28+mpg avg.

That's right about what I got on the C5Fest trip. Daily I'm getting about 21-23 (all city driving).

[Angrybird 12]

Originally Posted by rtcat600man

True enough, but both mornings were cold and clear.....not sure how much humidty or BP change there really was......like I said not scientific and this was the only time I was going to do these tests, otherwise I will set the cruise on my drive in and just enjoy the music and the ride.

I always figure in + or -1 Mpg anyway...

[Reeko]

Originally Posted by theholycow

More dense air, more oxygen, so you can inject more fuel and make more power. That's more power, not more fuel economy.

Not necessarily.
It depends on the air flow.
Many of the CAIs out therenot only flow better, but they effect the fuel trims slightly. The stock Airbox I believe (at least on the SS) runs a little rich. This results in less effeciency.

If a CAI results in fuel trims that are closer to optimal, you can result in a slight MPG improvement, even while gaining power.

[Angrybird 12]

Originally Posted by Reeko

Not necessarily.
It depends on the air flow.
Many of the CAIs out therenot only flow better, but they effect the fuel trims slightly. The stock Airbox I believe (at least on the SS) runs a little rich. This results in less effeciency.

If a CAI results in fuel trims that are closer to optimal, you can result in a slight MPG improvement, even while gaining power.

i agree, I put one on my 2005 Jeep Liberty hoping to get better than 20MPG on the Highway and the gas mileage went down... I took it off and it went back up...

[theholycow]

Originally Posted by Reeko

The stock Airbox I believe (at least on the SS) runs a little rich. This results in less effeciency.

This thread is about the V6. One of the major reasons why the DI V6 can get such great fuel economy is that it can run very, very lean without having to worry about detonation.

If a CAI results in fuel trims that are closer to optimal, you can result in a slight MPG improvement, even while gaining power.

I suspect that GM's engineers aren't fools.

As far as lean vs. rich, the MAF sensor will tell the computer how much air entered the engine (by mass, so changing density doesn't affect its accuracy) and the O2 sensors will tell it if it was lean or rich so it can adjust.

[Reeko]

Originally Posted by theholycow

This thread is about the V6. One of the major reasons why the DI V6 can get such great fuel economy is that it can run very, very lean without having to worry about detonation.



I suspect that GM's engineers aren't fools.

As far as lean vs. rich, the MAF sensor will tell the computer how much air entered the engine (by mass, so changing density doesn't affect its accuracy) and the O2 sensors will tell it if it was lean or rich so it can adjust.

I got that, but GM tends to be concervative. Many people have hooked up Tuners to their car and observe that they run a little rich under load. All I am saying is that a CAI can result in the A/F mixture being leaner with the stock Tune. It has been measured.

My only point is that a CAI does not have to result in a lower MPG and CAN get better MPG in some cases.

[l008com]

Originally Posted by theholycow

One of the major reasons why the DI V6 can get such great fuel economy is that it can run very, very lean without having to worry about detonation.

What is the technical reason for that? I'm curious.

[theholycow]

Originally Posted by l008com

What is the technical reason for that? I'm curious.

With direct injection you don't have to worry about knock. The fuel isn't injected until just before the spark plug fires. That means that most of the compression stroke is finished before there's any fuel there.

Another related advantage of DI is that the throttle can be opened to reduce pumping losses...people worry about their air filter but then they keep their throttle closed, it's kinda backwards (no choice with an automatic transmission, though). Anyway, it can operate like a diesel, controlling power by how much fuel goes in rather than having to strangle the air supply to keep the ratio correct. With drive-by-wire throttle, the computer can make this happen regardless of what the driver does.

[l008com]

The first paragraph made perfect sense.

The second one totally lost me.

[theholycow]

Put more simply, DI allows you to have an open throttle (using methods other than throttling to limit power), which means you don't waste energy sucking air through a closed throttle.

It's similar to how diesels operate. They don't have a throttle at all. That's one of the reasons they're more efficient.

[DGthe3]

Originally Posted by theholycow

With direct injection you don't have to worry about knock. The fuel isn't injected until just before the spark plug fires. That means that most of the compression stroke is finished before there's any fuel there.

Another related advantage of DI is that the throttle can be opened to reduce pumping losses...people worry about their air filter but then they keep their throttle closed, it's kinda backwards (no choice with an automatic transmission, though). Anyway, it can operate like a diesel, controlling power by how much fuel goes in rather than having to strangle the air supply to keep the ratio correct. With drive-by-wire throttle, the computer can make this happen regardless of what the driver does.

I don't believe DI has advanced that far yet. There are two methods of DI, what you mentioned where its towards the end of the compression stroke, but there is also the sort where it is still injected on the intake stroke. But it still reduces knock. As the ultra-high pressure fuel is injected, the rapid de-pressurization causes it to absorb heat, even from regular temperatures seen in the intake. At first I didn't know of this second method, but I believe this is how the DI in the Camaro works. The next step would be what you were describing.

[theholycow]

Oh...I thought that was pretty much the entire point of DI. Did GM do a half-assed job on it? :(

[DGthe3]

Originally Posted by theholycow

Oh...I thought that was pretty much the entire point of DI. Did GM do a half-assed job on it? :(

Technology is often used as an adaptation of existing methods rather than going with something completely different. Its safer to let engineers play with what they sorta know rather than going into uncharted territory. Fuel injection was initially a substitute for collaborators with via throttle body injection. Then multi-port came along and the true benefits were seen. Current DI is utilized largely like multi-port. It still shows good gains, but there is always more potential. And direct injection is only an intermediate step on the way to HCCI (don't expect it any time soon)

[biojack]

I'm at 20 mpg at about 1200 miles - i have only started revving it above 3000rpm this week...how are any of you getting +25 mpg??

on one tank i really made an effort to drive efficiently, no hard take offs over 2000rpm, and still only got about 20-21...i think some ppl are fibbin' (especially anyone saying they are getting 27 mpg....