Bad mpg?

[blanchard7684]

Yeap, just like mentioned above, the 5.3 might need 30% throttle to achieve the same power the 6.2 does at 20% throttle.

So for all use cases that don't call for more than 355hp (the amount the 5.3 makes), the 5.3 will have the throttle open slight more than a 6.2 making the same power.

Once the 5.3 hits wide open throttle, its done, can't draw in any more air, so injecting more fuel wouldn't do anything to make more HP. Whereas the 6.2 can draw in more air thanks to its larger displacement, so it can inject and burn more fuel, making more hp.
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Yes the difference in throttle position is precisely related to ve.

The ve is not constant until wot.

This is why timing maps are dependent on rpm and load as well.

As the load increases, ve goes up because more air is entering the cylinder. To keep the power level the same more fuel is added but the ratio does not necessarily default to 14.7.

If you have been to any dyno or even seen one on media you’d know that the afr isn’t just either 14.7 or 12.8.

 

[BacDoc]

As far as the OP and mileage, I think that your mpgs are pretty good going 79 mph. My 2024 Tahoe has the 6.2l and gets similar mpg going 78-80mph. Here in Florida on flat roads and highway speed limit is 70 mph traffic is usually doing mid 70’s mph so that’s what I’m usually driving on the highway. Some of my routes are 50 mph speed limits and on these roads with cruise set at 55 mph my Tahoe usually gets mid 20’s mpg. This is on flat smooth roads. Not bad for the big V8 with 420hp.

In the mid 90’s I bought a Chevy van with the smaller V8 as I was concerned about fuel economy. That smaller V8 only got 16/17 mpg on highway and close to 12 mpg in city. Always felt underpowered when driving although it towed well with no problems. I put over a hundred K miles on that with no problems but the next Chevy van I bought in 2004 had the 6.0l V8, much better driving experience and I was getting consistent 18 mpg going 75-80 on highway. I was surprised at how the bigger more powerful engine was slightly better mpg and a lot better driving overall.

Now I’m not concerned at all with fuel economy and loving the power, sound and performance of the 6.2l. If you drive aggressively and have fun the fuel economy suffers but it’s worth it lol!

My conclusion is the newer GM bigger V8 can get similar mpg as the smaller V8 and both V8’s can get similar to better mpg than newer turbo charged 6 cylinder engines offered in the newer trucks by other manufacturers like Toyota and Ford.

If your main concern in buying a new truck is fuel economy then the desiel is the best option. Or god forbid buy a friggen Prius

 

[Antonm]

Do you know what an air fuel ratio is?

Do you know that they vary depending on power demand?

You have a really really hard time with this.

Your response is amusing and immature.

Which reflects your knowledge of this subject.

LOL, you're freaking clueless, trying to argue points with gross conceptual errors on your part.

Everything we've talked about (at least so far) has been pretty basic stuff ,,, and you've gotten most of it wrong.
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[Antonm]

.

As the load increases, ve goes up because more air is entering the cylinder. To keep the power level the same more fuel is added but the ratio does not necessarily default to 14.7.

The air fuel ratio "defaults" to whatever the ECM tells it to.

At light throttle, it doesn't go into enrichment, it stays at, or as near as it can, to Stoichiometric. Becsue the 02 sensors tell the ECM how far it is off, and the ECM adjusts injector pulse width to get AFR back to wherever the tuner (in this case the GM tuners, the guys that will do anything for 0.01mpg to help their CAFE numbers), tells it to.
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[Antonm]

If you have been to any dyno or even seen one on media you’d know that the afr isn’t just either 14.7 or 12.8.

Only been to the chassis dyno maybe 30-40 times, but I have had cars (multiple cars actually) with aftermarket afr gauges in them that I keep an eye on while driving.

And while lean is mean, you always error on the side of rich for safety. What the 02 sensor sees is an average off all cylinders (or an average of all cylinders on that bank for a V configuration engine). So if you're seeing 14.1 at wide open throttle on the gauge, you can bet your left nut that one of the cylinders on that back is running in the 15s, and that can get expensive real quick.

So targeting a 13.0 afr is generally good for both horsepower and for cylinder to cylinder distribution.

The fancy engine dyno guys have headers with lambda sensors in every primary tube, so they get to see just how crappy whatever intake manifold they're testing is at cylinder to cylinder distribution . Some of the more serious drag and drive guys will have headers with eight lambda sensors in them too.
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[blanchard7684]

LOL, you're freaking clueless, trying to argue points with gross conceptual errors on your part.

Everything we've talked about (at least so far) has been pretty basic stuff ,,, and you've gotten most of it wrong.
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A dismissive post with ad hominem is usually a good indicator of weakness.

Slow clap.

 

[blanchard7684]

The air fuel ratio "defaults" to whatever the ECM tells it to.

At light throttle, it doesn't go into enrichment, it stays at, or as near as it can, to Stoichiometric. Becsue the 02 sensors tell the ECM how far it is off, and the ECM adjusts injector pulse width to get AFR back to wherever the tuner (in this case the GM tuners, the guys that will do anything for 0.01mpg to help their CAFE numbers), tells it to.
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Ok since I’m so clueless you tell me:

How is it the 6.2 can get nearly identical mileage as the 5.3 in the same suv with same gear and same mass?

Since your knowledge is so vast and impressive it should be easy.

I have offered a plausible explanation with facts and solid theoretical basis.

Your turn…

 

[blanchard7684]

The air fuel ratio "defaults" to whatever the ECM tells it to.

At light throttle, it doesn't go into enrichment, it stays at, or as near as it can, to Stoichiometric. Becsue the 02 sensors tell the ECM how far it is off, and the ECM adjusts injector pulse width to get AFR back to wherever the tuner (in this case the GM tuners, the guys that will do anything for 0.01mpg to help their CAFE numbers), tells it to.
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How exactly do you know this?

Do you have an afr vs hp ( or throttle position)chart you can share?

Fuel tables in the ecm aren’t just stoichiometric or full enrichment.

 

[Antonm]

Ok since I’m so clueless you tell me:

Yeap, you're clueless , but at least you had the good sense to go back and edit this little gem out out of your original post that contained it.



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[Antonm]

How is it the 6.2 can get nearly identical mileage as the 5.3 in the same suv with same gear and same mass?

Easy, because they're moving the same mass at the same rate, and therefore using the same amount of energy,,, maybe go back and review , because we've been over this before.
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