Toyota vs Infinity/Nissan MPG

[rpn453]

quote:

---

Originally posted by Winston:
But we are talking a 3 mpg difference on the highway between the two cars. I dont think tires, tranny, electric steering, and 100rpm could account for 3mpg. IMHO.

---

If you want an extreme example of how much difference a tranny can make, check out a '92 Geo Metro 1.0L:
3 spd auto: 36/39mpg
5 spd manual: 46/50mpg
Because of the inefficiency of that auto, the manual gets over 25% better mileage. A more efficient automatic, probably even one with 3 speeds (and a lockup TC), could match the economy of the 5spd.
It's common to assume as much as 25% drivetrain loss on an automatic. There's a lot of room for differences there. You could probably even change it more than 3mpg on the EPA test just by changing shift mapping though; getting into high gears quicker or holding shifts longer. GM incorporates a solenoid that prevents you from being able to shift to second on the Tremec 6spd under moderate acceleration, just to improve EPA fuel economy numbers. It must make a significant difference for them to not only spend the time and money, but also **** drivers off that have to use it. Luckily, it's easy to disable.

As for the other things: car companies haven't gone to electric steering on some vehicles because it feels better, and they're definitely not running 215's on the Avalon because it performs or handles better. These things add up!

quote:

---

Originally posted by Winston:
RPN, where are you getting the "drag area" numbers?

---

Car and Driver publishes drag area. I've got lots of back issues!
For anyone that's unfamiliar with the term; it's just frontal area multiplied by drag coefficient.

 

[jtantare]

quote:

---

Originally posted by ekpolk:
OK, if the Max's FWD system is that much more efficient than the G's RWD setup, why does the Max, which weighs about the same, and has almost identical hp and tq take a full second more to reach 60 mph than the G? Can you account for that "loss"? Only in the gear ratios.

Think about the setups -- what part of a RWD setup would account for such a huge disparity in mileage? They both have an engine, a transmission, a differential, etc. The extra weight of a longer drive shaft is way short of being sufficient to drag mileage down by approx 20%. And again, by your reasoning, if the RWD setup is significantly "draggier" the Max should be that much faster than the G, but it's not. It's a slower car.

---

Simple. FWD weight shift. When you are flooring it the weight of the car shifts onto the rear tires. In that situation front tires have less traction and therefore longer acceleration numbers for FWD. This has nothing to do with the efficiency of the drive train at lower power constant speed cruise. A RWD car will always have better acceleration numbers than a FWD with the same power and weight.

 

[ekpolk]

And what about this FWD/RWD comparison: The '06 ES-330, with 3.3L V-6 and FWD is rated at 21/29 mpg. The new GS-300, with 3.0L V-6 and RWD is rated at 30 mpg highway. Not surprisingly, despite its impressive hp figures for a 3.0 engine (245/230), it's acceleration is about a tick slower than the G.

So, here we have similar FWD and RWD cars, and yet they're getting essentially the same mileage. This is happening because Lexus desires to maintain quiet ambience for which its cars are famous. To do this, they have to be geared for relaxed, low-rpm cruising, which also happens to result in improved gas mileage.

By the way, I was dcefinitely incorrect about one thing. The new Avalon's engine is NOT the 3MZ 3.3L. It's a new 3.5L V-6 derived from the 4.0L V-6 that first appeared in the current version of the 4-runner. This is of little consequence, though; this engine is yet another example of Toyota's baby's bottom smooth V-6s.

 

[ekpolk]

quote:

---

Originally posted by jtantare:

quote:

---

Originally posted by ekpolk:
OK, if the Max's FWD system is that much more efficient than the G's RWD setup, why does the Max, which weighs about the same, and has almost identical hp and tq take a full second more to reach 60 mph than the G? Can you account for that "loss"? Only in the gear ratios.

Think about the setups -- what part of a RWD setup would account for such a huge disparity in mileage? They both have an engine, a transmission, a differential, etc. The extra weight of a longer drive shaft is way short of being sufficient to drag mileage down by approx 20%. And again, by your reasoning, if the RWD setup is significantly "draggier" the Max should be that much faster than the G, but it's not. It's a slower car.

---

Simple. FWD weight shift. When you are flooring it the weight of the car shifts onto the rear tires. In that situation front tires have less traction and therefore longer acceleration numbers for FWD. This has nothing to do with the efficiency of the drive train at lower power constant speed cruise. A RWD car will always have better acceleration numbers than a FWD with the same power and weight.

---

All things being equal, true by a small margin. But now, we're mixing metaphors and adding other factors. If you take two cars, A and B, that are identical in all respects, but you put a 3.0 final drive in A and you put a 4.0 final drive in B, B will stomp the crap out of A in virtually every acceleration contest you can devise. On the other hand, A will always turn in far superior gas mileage figures. At a stable, side-by-side highway cruise, A's fuel supply only has to turn the engine over three times while B's has to do four revolutions.

Now, let's change the facts some. If A happens to be a Max and B happens to be a G35 Sedan, you'll get the same results. The fact that the G35's weight and balance favor it slightly at the strip won't change things by much.

In addition, weight shift has nothing to do with the highway mileage disparity that exists between these two cars.

EDIT: I would change your last statement to read, "A RWD car will always have better acceleration numbers than a FWD with the same power and weight, and same final drive ratios.

 

[jtantare]

Have you tried stomping on a Maxima from a standstill? It will lay down a single black tire mark on the road for a good 30 feet before it really starts accelerating. Ask me how I know. Traction makes a world of differenece in acceleration.

 

[ekpolk]

quote:

---

Originally posted by jtantare:
Have you tried stomping on a Maxima from a standstill? It will lay down a single black tire mark on the road for a good 30 feet before it really starts accelerating. Ask me how I know. Traction makes a world of differenece in acceleration.

---

Actually, yes I have, on a test drive -- wish I'd taken a photo of the salesman's face. Part of why I now drive a G35. On the other hand, if you do this in a stock G35, with it's achilles heel open differential, you get much the same result, only not quite as long. At some point, I'll probably spring for a Quaife LSD, but until then, I'm a fellow member of the "peg leg diff" club. My G will beat your Max (assuming it's stock

) at the strip, but I will pay for the privilege at the pumps. All comes back to -- yep, the final drives. BTW, I was sort of hoping that Quaife would offer a better mileage gear ratio, but no such luck. Doesn't make sense anyway, they're really marketing to the 350Z crowd and they're definitely not looking for mileage over acceleration.

 

[Winston]

EK, again, you argue while agreeing. Jtantare never implied that the max would beat your G.

Jtantare was answering your question;

"why does the Max, which weighs about the same, and has almost identical hp and tq take a full second more to reach 60 mph than the G? Can you account for that "loss"? Only in the gear ratios.
"

He was stating it was because the weight shift causes lack of traction.

 

[ekpolk]

quote:

---

Originally posted by Winston:
EK, again, you argue while agreeing. Jtantare never implied that the max would beat your G.

Jtantare was answering your question;

"why does the Max, which weighs about the same, and has almost identical hp and tq take a full second more to reach 60 mph than the G? Can you account for that "loss"? Only in the gear ratios.
"

He was stating it was because the weight shift causes lack of traction.

---

I was not arguing at all, you didn't read the post carefully. I was merely pointing out that the result of the acceleration contest would be as he predicted, but because of the G's quicker gearing, not just because of the traction difference. That same quicker gearing, of course, is what kills the G's mileage figures.

And, by the way, you have not explained how or why the two Lexus models I described above, which like the Max and G are of similar size and weight, while one is FWD and the other is RWD, get virtually the same mileage. I'll save you the trouble: it's because the FWD vs. RWD differences are minor but they both have similar quiet-cruise-oriented final drive ratios resulting in parallel, high mpg numbers.

 

[Winston]

quote:

---

And, by the way, you have not explained how or why the two Lexus models I described above, which like the Max and G are of similar size and weight, while one is FWD and the other is RWD, get virtually the same mileage. I'll save you the trouble: it's because the FWD vs. RWD differences are minor but they both have similar quiet-cruise-oriented final drive ratios resulting in parallel, high mpg numbers.

---

They have completely different engines. Reading on the Lexus web site the GS has dual VVTi with separate control of intake and exhaust valves. The ES only has VVTi on the intake valves. The GS has "direct to cylinder" fuel injection. The ES engine has a bigger displacement 3.3L vs the 3.0L of the GS. In addition it has six speeds vs the 5 speed transmission of the ES.

Look at the '05 GS with the older engine. It is only rated at 25mpg highway. The new GS mpg jumped up to 30mpg with this new engine/tranny combo.

 

[XS650]

quote:

---

Originally posted by John K:
EK - I don't remember how much the MG Midget weighed for sure, but I think it was around 2200 lbs... The engine was 1100 cc.

---

Closer to 1600 lbs. There weren't any extra parts in that car and what were there were small.

 

[ekpolk]

quote:

---

Originally posted by Winston:

quote:

---

And, by the way, you have not explained how or why the two Lexus models I described above, which like the Max and G are of similar size and weight, while one is FWD and the other is RWD, get virtually the same mileage. I'll save you the trouble: it's because the FWD vs. RWD differences are minor but they both have similar quiet-cruise-oriented final drive ratios resulting in parallel, high mpg numbers.

---

They have completely different engines. Reading on the Lexus web site the GS has dual VVTi with separate control of intake and exhaust valves. The ES only has VVTi on the intake valves. The GS has "direct to cylinder" fuel injection. The ES engine has a bigger displacement 3.3L vs the 3.0L of the GS. In addition it has six speeds vs the 5 speed transmission of the ES.

Look at the '05 GS with the older engine. It is only rated at 25mpg highway. The new GS mpg jumped up to 30mpg with this new engine/tranny combo.

---

30 mpg with one of those terribly inefficient RWD setups -- how could that be???

And now, when a comparison of two similar RWD and FWD cars,* with similar mileage, conflicts with the point you are pushing, you want to start bringing in other factors. Up to this point, you've been asserting that there's some friction or drag inherent in the RWD setup that's absent from FWD cars, and this is the explanation for the mileage disparity. Now we have two cars that don't fit that mold, so you rush to bring in other factors.

*where did I say identical, the Max and G aren't identical either, far from it, and in addition, while their engines are both of the VQ35 family, they both have significantly different versions.

Here's an excerpt from an article you should study: "Fortunately, today's transmissions frequently utilize Overdrive high gears in the neighborhood of 0.70:1, which allow reduced engine speeds. Combine these overdrive transmissions with a 4.10 axle ratio and you have a fuel-friendly final drive ratio of 2.87:1 (4.10 x 0.70 = 2.87) in high gear. A TH200-4R overdrive automatic utilizes a First gear of 2.74, a Second of 1.57, a Third of 1.00, and a 0.67 Overdrive. With this transmission's First gear ratio of 2.74 combined with a 3.73 axle ratio, the final drive ratio >> yields a 10.22 (2.74 x 3.73 = 10.22). In overdrive, the final drive ratio equates to a Bonneville-ready 2.49:1.

. . .

By applying the basics of gear ratios and power leverage, you can easily improve acceleration without paying too steep a price in highway rpm. It's all in the ratios" (emphasis added). Full article at chevyperformance.com.

Or how about this, from the carlist auto glossary: "FINAL DRIVE RATIO. This is the ratio of the gearset (usually the differential) that is farthest from the engine. A ratio of 3-54:1 means the driveshaft turns 3.54 times for every one turn of the wheels. Generally speaking, the higher the number, the better the vehicle's initial acceleration and pulling power. The lower the number, the better the vehicle's fuel economy" (emphasis added).

This is a precise, and exact explanation of why a G35 is quicker than a Max, and sucks down a lot more gas.

Back at ya. . .

 

[John K]

EK - I don't remember how much the MG Midget weighed for sure, but I think it was around 2200 lbs... The engine was 1100 cc. I also had an 87 Chevy Sprint 5 spd someone mentioned, I usually got around 45 mpg, and I drove it hard. Speedometer only went to 85, and I guestimate I had it up to 93 mph while it was hammering and making all kinds of noises! Fun for a little 3 cylinder.

 

[Alan]

quote:

---

Originally posted by ekpolk:
This is of little consequence, though; this engine is yet another example of Toyota's baby's bottom smooth V-6s.

---

I have a 1MZ-FE in my 02 Sienna and it's pretty smooth but not "baby's bottom smooth"(man i'm picky!).The VR6 on my previous VW GTI was a bit smoother.

The M54 I6 in my 325i creams both though.Truely an awesome engine!

 

[ekpolk]

Shoot Alan, you're just spoiled! The BMW straight sixes are almost untouchable as to smoothness. Between the inherent balance of the I-6 and the effort BMW puts into them -- well you know what I mean better than I do.

It's always a struggle to characterize qualities such as how an engine runs in subjective terms. Bottom line (ooops) is that the VQ V-6 does not seem to convey as much of a hushed, velvety feel as the xMZ engines. It's by no means unpleasant, at least to me. I enjoy the "powerful machine" sense that the VQ creates as well as the more "animal growl" it makes when you step into it. Definitely a "fun" engine to use, whereas my Camry's V-6, seemed like the engine that the designers wanted to be unseen, unheard and unfelt. Again, both outstanding, just different personalities.

 

[Winston]

OK. Lets see. You asked me to explain why the two cars get similar mileage while one is RWD and the other is FWD. Then you complain that I brought up "Other factors"?!?!?! I feel like you are calling me a cheater. The Lexus literature clearly states that the dual VVTi allows for better efficiency and better torque curve. From the very begining of this thread I have been saying that engine efficiency plays a role in mpg. The initial premise of this thread is that Toyota engines are more efficient than Nissan VQ engines. That new Lexus engine seems even more efficient that the previous versions of their V6 engine.

As far as the question of RWD vs FWD and efficiency, I think the inefficiencies of RWD do have a significant effect on MPG. All the examples confirm this. Your example does not disprove it.

As far as rpm/final drive ratio vs. mpg, I agree that it affects mpg, the question is how much.

As far as why the G is faster than the Max, I agree that gearing plays a big part in it. The weight shift issue is probably not too significant.

In the end I think we agree that all these factors contribute to mpg. We will never determine exactly how much they contribute without hard data. Our main dissagreement is over the significance of FWD/RWD vs gearing. By comparing various cars mpg we can learn something, but nothing really conclusive. There are many references that state that gearing affect mpg, but again the question is how significantly. Its been an interesting discussion for me. It think we have beat it to death. I think I am done with this one.

 

[ekpolk]

Winson:

No I'm not calling you a cheater. I just think you're mixing metaphors and changing factors a bit inconsistently. That's easy enough to do with no dishonesty whatsoever intended. Please accept my apologies if I came off too strongly in this regard -- certainly not intended.

You said, "The initial premise of this thread is that Toyota engines are more efficient than Nissan VQ engines. That new Lexus engine seems even more efficient that the previous versions of their V6 engine". I respectfully disagree with that. I would just point out that the Max and the V-6 Altima achieve about the same mileage as the comparable Toyota products. From that, you might infer that the RWD is less efficient, because it's RWD. But remember, the G35 is a different car with a different "mission" in life. It's "inefficiencies" aren't a result of its RWD design, at least not primarily. Remember, the G is nothing more than an expansion of the 350Z platform. It was not designed with fuel economy in mind, but rather, for fast acceleration and razor sharp handling. The final drives that are available for this family of cars are all dreadfully anti-mileage, pro-acceleration. There are a number of threads about this issue over on my350z.com that are worth a look.

The one question that keeps coming to me as I consider what you're saying is, "what specific mechanism in a RWD car that's absent from a FWD car do you think is responsible for making RWD that much less efficient?"

All this said, I do agree with you that many factors play into any car's ultimate bottom line mileage and performance stats.* If you do some more digging around for info, I think you'll find that final drive ratio is one of the (if not the) dominant factor in fuel efficiency, other factors being equal or similar. In short, if you changed a Max's, the V-6 Altima's, or even a V-6 Camry's FDR to be the equivalent of a G35's, they'd suck down pretty much the same amount of gas.

EDIT: They'd also be a good bit quicker off the line.

*One more disclaimer: it is very possible to agree with some of what you say, while disagreeing with other things. I don't understand why you find this disturbing.

 

[jtantare]

Are we still debating the 3mpg difference? Hard core.

 

[ekpolk]

quote:

---

Originally posted by jtantare:
Are we still debating the 3mpg difference? Hard core.

---

Alas, when you average about 35k miles per year (I did 40k last year) and fuel goes for around $3 per gallon, a 3 mpg difference has a hard core impact on your overall fuel expenditure. . .