Bad mpg?

[Antonm]

Is this what you want to go with?

Ok...

1) 5.3 towing uphill at 80% throttle WILL NOT BE AT 14.7 no matter how many times you try to type this out. The 5,3 will be deep into fuel enrichment (depending on gear) and close to max power so there is no feasible way you can claim it is at 14.7 afr.

Ergo of course it will make more power than a 6.2 that is on flat ground cruising.

2) 5.3 L cylinder mixed at 14.7 air/ratio will make less power than a 6.2L cylinder at 14.7 afr because the smaller cylinder will have less fuel in it.


From 1 and 2 you can see that at part loads (where a 6.2 can be at a higher afr) it will have incremental efficiency over 5.3. The 5.3 has a small enough displacement difference that it will need more fuel to make same power as 6.2.

If this isn't the case, then there is no need to have higher displacement engines.

If every engine on earth that runs on Otto cycle makes the same power at every AFR, or at 14.7, then it must be an illusion when dyno sheets show that a stock 6.2 makes way more power than a stock 5.3 at wot (13.1 afr).

In your view, no matter what the afr is, the 5.3 and 6.2 should make the same power in virtually all conditions of driving. This is ludicrous beyond what the english language can accurately describe.

You're just trying for anything aren't you, sad little man. You're wrong, just face it.

A 5.3 at 80% throttle will in fact be making more horsepower (at any given afr ,including 14.7) than a 6.2 will be at 20% throttle (at that same given AFR, even if its 14.7).

If that is beyond your comprehension then I'm truly sorry for you mankind. Because that's how we got to where we now have warnings in the owners manuals that say don't drink the contents of the battery.
...

 

[Antonm]

I'll bet the OP regrets posting this thread.

Why, its good for laugh and entertaining, or at least I'm entertained (although it is probably morally wrong of me to laugh at someone that might be mentally challenged).
...

 

[Marky Dissod]

Vast majority of mentally challenged people are the nicest people ever. At least that's my experience.
They certainly don't go out of their way to be psychologically / socially challenging / obstinate / obtuse / vexatious / difficult,
and they certainly do NOT deserve to be IGNORED.

 

[Antonm]

Please respond to post 79 as well.

Sure, its just yet another case of you being silly and grasping at straws (all while being clueless I might add).

Post 79 started when I responded to your post 67 about how could the 5.3 and 6.2 get the same fuel milage (see post 67 below)



To which I responded in post #70 as;



To which you now throw in;



So, lol, okay, you never said the same rate.

If they're moving or accelerating at different rates, then its not an apples to apples comparison for fuel milage. Of course it takes more energy to move or accelerate at a faster rate. That what's you call a self evident fact.

Remember how I mentioned you should be taking notes,,, yeah this is another time when those notes would've been helpful to you.
...

 

[Antonm]

Vast majority of mentally challenged people are the nicest people ever. At least that's my experience.
They certainly don't go out of their way to be psychologically / socially challenging / obstinate / obtuse / vexatious / difficult,
and they certainly do NOT deserve to be IGNORED.

You know, you're absolutely right.

My apologies to any mentally challenged people out there for comparing Blanchard7684 to you,,, you guys/ gals are much nicer.
...

​

 

[blanchard7684]

You're just trying for anything aren't you, sad little man. You're wrong, just face it.

A 5.3 at 80% throttle will in fact be making more horsepower (at any given afr ,including 14.7) than a 6.2 will be at 20% throttle (at that same given AFR, even if its 14.7).

If that is beyond your comprehension then I'm truly sorry for you mankind. Because that's how we got to where we now have warnings in the owners manuals that say don't drink the contents of the battery.
...

Please continue living in fantasy land.

You are astonishingly misinformed here.

but at least you are making it clear you think displacement is meaningless.

Well done

 

[Antonm]

lol, you’re a riot man.

So by that comment am I to assume you think a larger displacement 6.2 will make more power at 20% throttle than the smaller displacement 5.3 will at 80% throttle assuming that both engines running at the same afr?

Is that what you’re saying now? Because that sounds like what you’re going for, and would be consistent with that earlier statement you accidentally deleted.
..

 

[blanchard7684]

lol, you’re a riot man.

So by that comment am I to assume you think a larger displacement 6.2 will make more power at 20% throttle than the smaller displacement 5.3 will at 80% throttle assuming that both engines running at the same afr?

Is that what you’re saying now? Because that sounds like what you’re going for, and would be consistent with that earlier statement you accidentally deleted.
..

Nope. Not what I'm saying.

1)

You are injecting a throttle position range into the discussion where it doesn't need to be.

80% throttle in a 5.3 will not be the same afr as a 6.2 at 20% throttle.

I'm not talking about extremes of driving here as was clearly present in many of my posts. I'm talking about tip-in conditions for moderate passing, small inclines, and substantial headwinds.

These aren't scenarios where 80% throttle is even close to applicable.


Again the 6.2 equipped suv can navigate these situations with a small efficiency surplus vs the 5.3. Taking this over a tank of gas, it will show up as a small increase in fuel efficiency.

I'm not talking about some huge mpg difference. It isn't like the 6.2 can get 30 mpg in the above driving scenarios...I'm talking like 0.5-2.5 mpg difference.

The reason the 6.2 can do this is because it can make the requisite power to do so at higher afrs, meaning it can do so with less fuel.

This is because a 6.2 filled to a 14.7 afr (for example) will make more power than a 5.3 L engine filled up at 14.7 afr.

I'm not saying the 5.3 jumps into a full power afr at the conditions specified above.

If I floor my suburban (5.3) my instant fuel mileage reads 2. When on flat level ground with no headwind the instant fuel mileage reading is 18.5 at 75 mph.

The scenarios above I've seen instant fuel mileage in a range of 8-13.

If "2" represents open loop afr then it should be about 12.8-13.1.

If 18.5 represents the lowest power demand (just barely enough to overcome wind) then this should be in range of 14.7-15 afr.

(direct injection can actually go up to 17 because of the combustion chamber design...perhaps another discussion)

So you can see that in the specified conditions for driving above, the afr in the 5.3 is not going to be 14.7.

From this very thread there are many instances of the 6.2 getting better than expected fuel mileage.

Based on displacement alone, this is justifiable and reasonable outcome.

2)
The other variable that is related to engine power is what the transmission is doing.

In the above scenarios, the transmission can downshift (1-2 gears). Especially if more than one situation is present (incline and passing, headwind and incline, etc).

If engine is downshifting more often, it will be spending more time at an incrementally higher rpm which also uses more fuel over a given stretch of distance. This is because there is more fuel injection events happening over a given time range regardless of afr.

Because the 5.3 is at a power and torque deficit to the 6.2, because it is a smaller engine displacement, the downshifting in these scenarios is more prevalent.

Add both the downshifting and the displacement difference and a 5.3 equipped suv could have a small but noticeable deficit in fuel mileage vs 6.2.

 

[blanchard7684]

Some open source reference information to support this.

1). GM 4.3 Ecotec 3 study.

https://www.researchgate.net/publication/316000431_Characterizing_Factors_Influencing_SI_Engine_Transient_Fuel_Consumption_for_Vehicle_Simulation_in_ALPHA

Figure 1. BSFC map for 4.3 with DFM disabled.

You can see that at highway speeds this engine (lower displacement than a 5.3) would be operating at a suboptimal BSFC for speed and torque.

Downshifting to get to more torque and engine rpm puts this at a lower BSFC. But fueling rate for engine goes up (pink line, figure 6b).

From this you can see the lower displacement has a challenge in maintaining a good bsfc at cruising engine speed, and to improve it, more engine rpm is needed which only adds to the fuel consumption.

This is because the lower displacement engine has to use more fuel to make torque.

2) University based lecture notes on the details being discussed here.

https://www.webpages.uidaho.edu/mindworks/IC_Engines/week%203/Wk3_Performance_Parameters.pdf

Some pertinent aspects.

BSFC decreases with engine displacement. page 11.

Page 9 shows the inverse relation between displacement and BMEP.

Page 17 shows VE is a ratio of mass and is NOT a constant until WOT.

Further that VE is lower with lower throttle position and at a minimum when fully closed.

This relation shows that for a given mass air flow, the smaller displacement engine has to be at a higher VE for a given rpm.

Or put another way the combo of rpm and displacement has to be such that it supports the mass air flow required for a given engine torque.

This is where throttle position is actually somewhat relevant: the 5.3 will have a higher open throttle position to achieve moderate load driving demands. This throttle position though will drive up the fuel consumption because of it's lower BSFC.

 

[blanchard7684]

Sure, its just yet another case of you being silly and grasping at straws (all while being clueless I might add).

Post 79 started when I responded to your post 67 about how could the 5.3 and 6.2 get the same fuel milage (see post 67 below)

View attachment 447543

To which I responded in post #70 as;

View attachment 447544

To which you now throw in;

View attachment 447545

So, lol, okay, you never said the same rate.

If they're moving or accelerating at different rates, then its not an apples to apples comparison for fuel milage. Of course it takes more energy to move or accelerate at a faster rate. That what's you call a self evident fact.

Remember how I mentioned you should be taking notes,,, yeah this is another time when those notes would've been helpful to you.
...

Engine Power equation

See equation on slide 4.

nv is VE, Vbdc is engine displacement, AFR is air/fuel ratio.

For the power required to execute part load manuever, it is same because it is essentially the same mass.

The difference is engine displacement. The argument at hand is if the 6.2 can do this at higher AFR vs 5.3.

Based on that equation, if you assume VE is constant, the 6.2 can have higher AFR and make same power because the Vbdc term is increased.

So moving the mass up an incline, or into headwind, or tip in acceleration, for instance, the 6.2 can reach the required P on lhs of equation at higher AFR than 5.3 assuming throttle position is constant.

But, if 5.3 increases Ve via throttle, it can reach the required power. However throttle position and AFR are linked together inversely. So the 5.3 has to move to a lower BSFC area on its BMEP vs BSFC curve. This is in rel world represented by the fuel tables and shift schedule.

So the smaller engine will have a harder time keeping fuel consumption minimized in part-load conditions.

This is my point.