quote:Wishful thinking. FWD in most cases is more efficient than RWD. FWD drive train has fewer and smaller moving parts which generate less fricting. I'm sure there are other factors that we are completely ignoring. I have no doubt that both engines generate the advertised output. A fair comparison would be the FWD Nissan Maxima (20/28mpg)with the same engine vs Toyota Avalon.
Originally posted by Winston: They are both Japanese engines. They are both probably misstating the HP equally.
code:Engine HP Curb wt. Drag Coef. CityMPG HwyMPG Height Width Toyota Avalon 3.5L 280 3560 0.29 22 31 58.5 72.8 Infinity G35 3.5L 280 3468 0.27 18 25 57.7 69 Nissan Maxima 3.5L 265 3473 0.30 20 28 58.3 71.7
quote:Nope; 3460lb, 55.9" high, 71.5" wide. Smaller engine though.
Originally posted by jtantare: The BMW is a much smaller car than than the G35 or the Avalon.
quote:Maybe the Toyota's tranny gets into higher gears faster or at lower speeds? Maybe it is a more efficient engine? Why can't they do it with the IS350 though (3.5L, 19/26mpg, 306hp, 1850rpm at 60mph). The new G35 has a 298hp 3.5L and gets 19/26mpg too, at higher highway rpm. A lot of info would be needed for a definite answer. I congratulate them on getting such good mileage though. I consider that to be a big factor when I'm looking at cars.
Originally posted by jtantare: Nobody thinks the Toyota is a more efficient engine? What about the city mpg. The engine rpm at cruise would not have much effect on the city mpg. A Lexus GS300 gets 22/30 mpg. About the same size as the G35.
code:So, the Toyota is heavier, fatter, taller with a higher Cd. Yet it gets better mpg?!?!? How can this be? I think that both engines have VVT. I would not think the torque curves are that different. Yet clearly this shows that the Toyota engine is much more efficient. What do you think?Engine HP Curb wt. Drag Coef. CityMPG HwyMPG Height Width Toyota Avalon 3.5L 280 3560 0.29 22 31 58.5 72.8 Infinity G35 3.5L 280 3468 0.27 18 25 57.7 69
quote:The Toyota 3MZ-FE and Nissan/Infiniti VQ35 are totally different engines, other than displacement and general DOHC configuration. The 1MZ/3MZ family has always been biased toward quiet and smooth, whereas the VQ series is designed more with performance in mind. The VQ also has chain driven camshafts, whereas the xMZs are belt driven, so the Toyotas sound and feel a tad smoother (but don't forget to change the belts...). At least in the G35, the VQ has a smooth but rumbling/growling quality that's totally absent from the velvety MZ engines. Within the Nissan family, the VQ engines are built in several configurations, with varying intakes and ECU programming. For example, hp can run as low as 240 (recent MY Quest van) up to almost 300 (in the 350Z sports car). Also, as between the Max and the G, the setup varies as the engine is transverse in the FWD Max and longitudinal (front to rear) in the rear-drive G35. Both the 1MZ/3MZ and the VQ family are set up so that they can use regular fuel, but timing retards automatically (knock sensor-ECU based) on regular, resulting in less output. Use of premium results in noticeably better performance, as the timing advances in the absence of knock/ping. Advertised hp figures are supposed to be based upon use of the lowest speced fuel grade, hence Toyota's recent "derating" of its figures. Nissan/Infiniti went the other way, and now just says "premium fuel required" on performance-oriented VQ-powered cars, hence the higher figures. But back to the original question, I think that the main reason for the different mpg figures is the final drive ratios. The G is plainly set up with a short final drive, and shows it. It absolutely rockets off the line like its on a catapult, but it turns high rpms at highway cruise (I see almost 3000 rpms when cruising at 80 mph, about 3250 at 85), and gets crappy highway mileage (I'm lucky to see 23 mpg, real world). The Toyota's taller gearing rewards the driver with better mileage.
Originally posted by Winston: Good idea on the Maxima. Here goes. Still quite a difference, and now with less power.code:Engine HP Curb wt. Drag Coef. CityMPG HwyMPG Height Width Toyota Avalon 3.5L 280 3560 0.29 22 31 58.5 72.8 Infinity G35 3.5L 280 3468 0.27 18 25 57.7 69 Nissan Maxima 3.5L 265 3473 0.30 20 28 58.3 71.7
quote:Final drive ratios have little to do with friction. It's about the rpms associated with any given speed. The Avalon cruising beside me on the interstate at the same speed, with its taller gearing is going to be turning a lot fewer rpms than my G35 is, more importantly, he will be running in a more efficient part of his operating "envelope" than I am. Yes, the Avalon has a quieter cabin for several reasons, primarily though, because its engine isn't scremaing along at higher rpm like the G's is. Sure, RWD cars suffer a slight disadvantage in mileage, but that does not account for the 5 mpg defference between these two. If you don't understand what I mean by "designed with peformance in mind," you have not driven a VQ35-powered car. I might perhaps have chosen my words differently, OK. The car I owned before my G35 was a 1MZ-powered Camry (the 1MZ is the 3.0L predecessor to the 3MZ found in the new Avalon). Try driving a G and an Avalon back to back and you'll see what I mean. Similar specs, different animals. This comparison is a great illustration of the idea that there's more to a car than its performance numbers. Two fine cars with outstanding engines, but comparing them is apples and oranges. EDIT: As to the torque curve, though I've compared them side by side, I'd say that the VQ's is a lot fatter down low, probably a tossup at higher rpm. As far as the derating is concerned, that was my point -- they derated the numbers to satisfy the regulators. EDIT: This engine probably is good for 280 on premium, but it's Toyota's choice to keep its advertising consistent with use of regular gas. Inifiniti, on the other hand, wants the bigger numbers (remember, performance empahsis), so it calls for premium gas only. I don't begrudge you your preference of camshaft drive systems, though I'll take a timing chain any day over a belt. My UOAs don't seem to indicate that my timing chain is stressing the oil, and I have about 1/100th the chance that an Avalon owner has of finding out first hand what happens when a timing failure occurs. Hint: the 3MZ is an "interference" design -- i.e. if the belt breaks, pistons and valves are going to try to occupy the same space at the same time, a very, very bad thing. Not quiet, and not easy on any part of the engine, oil included, when that happens.
Originally posted by Winston: I tend to dissagree that it is the final drive ratios that affect the mpg. There will be a little more friction but not much. Lower final drive ratio also contributes to less cabin noise which is a reason for it in the Avalon. Looking at other cars mpg, the correlation seems much more related FWD vs RWD. Note the comment on the mpg for the IS350, it is a small car but it has RWD. As far as the de-rating of the Toyota, it probably puts out close to 280 with the same premium fuel as recommended for the Nissan. I am also confused by the quote "designed with performance in mind". Hp and Torque is Hp and Torque. I wonder what the difference in the torque curves is between these two engines. Oh, and I like timing belts. Quiet and easy on the oil.
quote:I think this is the crux of the issue. RWD/FWD, RPMs, and engine efficiency. I dont think a couple hundred rpms account for much in the way of efficiency. I think they do it mainly for the noise. Look at the Maxima, you only have 100 rpm difference while there is still a 3mpg difference between it and the Avalon. Plus, the Maxima engine is derated in hp(I would assume to increase efficiency). I think that example clearly shows the VQ engine is less efficient. I do not mean to Infinity bash, I like them much better than Toyota's, just the whole mpg thing bothers me. Oh, and about the whole interference engine blow up thing. It is a great way for mechanics to scare you into doing maintenance on your engine. How many engines have you ever heard of being damaged by a broken timing belt? When was the last time you had an alternator belt break? It just doesn't happen very often any more. As far as your chain, when you get up to nice high mileage (120k) that chain will have stretched and you will have no way to change it. Oh, and
Sure, RWD cars suffer a slight disadvantage in mileage, but that does not account for the 5 mpg defference between these two.