Last post on Jan 10, 2009 at 3:50 PM
You are in the Nissan Sentra
What is this discussion about?
Nissan Sentra, Honda Civic, Car Comparisons, Sedan
#31 of 226 Re: 1997-2006...And your point is...? [thegraduate]
Feb 09, 2006 (2:27 pm)
The Accord, yours or mine, has 139lb-ft4200RPM. The 07 Sentra is claimed to have about 1262400. (see Nissan webpage about the car, where they say "90% of max torque at 2400RPM".) The key is that a lot of drivers hate to send the engine to 4000+ RPM by downshifting the auto. trans., feeling dragged backward without warning. It takes a stronger engine to be capable to deliver high torque at low RPM. Other than the German cars, such as the VW Golf or Audi A3, only the Sentra is designed so. For cars with 2.5 liter or larger engines, it is OK to have the max torque (>180) appear at 4000, because even a linear interpolation implies >135 torque at below 3000RPM, while the weight of the car usually does not increase by 30%. (e.g. the Sentra 2.5 or the Impreza 2.5.) Like in a 6 cylinder car, there is no downshift necessary on a ramp.
With the Sentra, you can accelerate by push gas pedel slightly harder and make the RPM increase continuously. With a car having max torque 1304200, when you push the gas pedal a little bit harder, the car does not take your order to accelerate. Then you have to floor the pedal, the tahometer needle will jump to 4000, while you feel the dragging for a second, hear the engine hauling. I just hate it when that happens.
I hope I make my opinion clear. You may disagree with me.
#32 of 226 Re: 1997-2006...And your point is...? [tthota]
Feb 09, 2006 (2:37 pm)
You may disagree with me.
Thank you, and I do respectfully (on part of it anyway). Your facts are fine, and I don't find fault with anything you said; it's just subjective to each person. I drive in traffic everyday, and go between my 06 Accord with 160lb-ft and my 96 Accord with 139 lb-ft. Honestly, I can't tell much difference below 3k RPM in around town acceleration. Above 3k RPM though, boy, that 06 takes off. I hit the gas hard today when merging (short on-ramp), and I took off faster than I ever could've with my 96, and I wasn't flooring it. This is more to do with horspeower (high-end) than torque, yes I realize that.
If you are used to the engine characteristics of a V-6, I'm surprised you find a small 4-cylinder doable (Honda OR Nissan).
What I like about Honda's, is that there is natural progression of power increase...the higher the rpm, the more power available. Some cars run out of steam before redline, and that scares me for this reason...
If I'm getting out of the way of a truck bearing down on me dangerously, I'm gonna floor it if I can't get out of the lane(and likely, you are too). Flooring it is going to put me higher in the rev range, and in a Honda, that is where my power is going to be. My 2006 Accord makes its peak hp at 5750rpm (I think, 750 from redline). Our Odyssey made its peak hp closer to 5,000 rpm, which made it feel like it went soft when right at redline (of the few times it had to go there). I didn't like that.
Agreed to disagree tthota.
#33 of 226 Re: data [tthota]
Feb 09, 2006 (4:30 pm)
So now you agree with me. With Civics you use high RPM.
First of all I'm a new poster and never disagreed with you that the Civic engine makes the bulk of it's power at higher revs.
I do not like it, nor the downshift to get there. I like 6 cylinder cars just because of this. The Sentra is the only non-German compact 4 cylinder car which has good low RPM acceleration. This is what I have found so far, based on published specs. If you know some mechanics, you know this is hard to achieve. Driving a car to work everyday at age 50, I do not seek the motercycle excitement. I actually feel annoyed by the noises made by the other "sporty" cars, sometimes. You have to understand that different people look for different features on their cars. The number of drivers who hate having to use high RPM is not negligible. A lot of people do not know the importance of the location of max hoese power and max torque yet. The old specs from 10 years ago only gave the maxima. Now every specification of a new car is mandated to reveal the max HP and max torque together with the RPM numbers where the maxima appear. That is not for no reason. In fact, I would like to see the entire HPRPM and TorqueRPM curves for these cars. Without those, some car makers can still fool comsumers with cheaply designed engines, even dependable but cheap ones.
Hey, if you like driving a tractor and keeping the revs low, that's fine with me. Don't assume that everyone likes that though, or that an engine has superior design or engineering because it makes its power at lower rpm's. It's simply designed differently. It probably has a heavier flywheel and different cam, etc to achieve that goal (and thus probably revs up much slower than an engine designed to rev as well - it takes more effort to spin that heavy flywheel up to speed). EVERY torque and rpm curve cross at 5250 rpm's, it's just a matter of what they do before and after that point. If you like low rpm torque, why stop with a 6 cylinder? Why not a big block that makes 300 foot pounds while it's idling? You'd never even have to step on the gas then, you could just put really tall gearing in the transmission and shift. My point is that each application is different. If you don't like spinning the engine up to make power that's fine and it sounds like you bought the right car for YOU, but don't assume that everyone wants that same driving experience. I would personally HATE to drive a car who's engine wouldn't wind out a little. I don't really see the advantage to the low rpm torque personally. If it were a towing vehicle or truck that carried a heavy load that's a different story (and thus why those types of vehicles are designed to make power in that range). An economy car is not a different story though.
#34 of 226 Re: 1997-2006...And your point is...? [thegraduate]
Feb 09, 2006 (5:23 pm)
The 06 Accord has 160lb-ft4000RPM, compared to the 96 Accord having 1394200. If both at below 3000RPM, normally where it is at 50 mph, the 06 Accord should have 20% more torque than the 96 Accord, may be even more because of improved design details. The weight difference is only 10%. Of course the 06 Accord is faster.
Anyway, max torque at low rpm is desired in the design of small cars. Some examples are:
2006 Saab 9-3: 2.0 liter, 2212500
2006 Audi A4 convertible: 1.8 liter, 1661950,
2006 Audi A3: 2.0 liter, 2071800,
2006 VW Golf: 2.0 liter, 1222600,
2006 Sentra: 1.8 liter, 1292400.
Among them, Sentra has an affordable price. I buy it because I have to pay college tuition for my son.
A bad example among German cars is the MINI: 1114500.
#35 of 226 Re: 1997-2006...And your point is...? [tthota] THERE IS A MISUNDERSTANDING
Feb 10, 2006 (5:50 am)
There is quite a misunderstanding here....
Maximum torque is just that the RPM where maximum torque occurs. Each engine has a torque cureve base on RPM. All are in a somewhat bell shaped curve . but the diffrrences in the curve, very flat to a very steep peak make a differnece in the torque. The weght of the car makes a significant difference.Also the type of transmission, automatic ( number of gears or CVT) and manual number of gears and each gear ratio. Ant then finally there is the rear-end gear ratio. If it is a large number then it in effect multiplies the torque, but your engine runs at a higher RPM and your gas mileage will be less.
I think what maybe you shouldconcetrate on, instead of "Peak Torque" is the actual accelration times 0-10, 0-20, 0-30, 0-40, 0-50, 0-60. Most major car magazines when they review a car will give those numbers inseconds.
You probably want to concetrate on the 0-30 or 0-20 times. This will give you a much better idea than just the max torque number of a cars actual performance.
To put this all in perspective, would you buy a pet based solely on its eye color?
Cruis'n in a low torque, high RPM 2.2L 4 cylinder,
P.S.- It is amazing how many arm chair designers are better than factory design engineers
#36 of 226 Re: 1997-2006...And your point is...? [tthota] THERE IS A MISUNDERSTANDING
Feb 10, 2006 (7:22 am)
I'm concerned with acceleration from 50mph to 70mph. Experience tells me that, if the torque-weight ratio is small while the engine is turning at ~2500RPM, the transmission has to downshift for acceleration. A larger engine (>2.5 liter or 6 cylinder) should have enough torque in this range, no matter which car it is.
Compare Nissan Maxima with Sentra, the max torques are 2554400 and 1292400, and weights are 3447 and 2620. A Sentra has 76% of the weight of a Maxima, but only 50.5% of its torque.
For the compact cars with small engines, it helps to have the max torque appear early at ~2500RPM. In addition to what I listed as example of cars designed in this way, there are the VW Passat 2.0, VW Jetta 1.9 and VW GTI 1.8. Only a strong engine can take the load of high torque output at low RPM.
Those numbers like 0-60 in 7 seconds are for racing, where the engine turns at >5000RPM. I never have my cars run at >4500RPM for a second.
Feb 10, 2006 (7:34 am)
Then I'll pray for you the day an ambulance comes racing up behind you on the freeway at 90 miles per hour. We'll see where your torque gets you if you never rev your engine near the horsepower. My Honda will be singing at 5k and leaving the ambulance in the dust. FYI it doesn't hurt a car to rev it, you know, as long as you stay out of the tachometer's red zone, and even there, the engine should cut power to reduce engine speed, and prevent any damage. On my way to school today I doubt I touched 3,000 rpm, and had no problem making it to 65 mph, passing cars, or maintaining my speed up a 10% grade. This, in my car (96 Accord)whose peak torque supposedly isn't satisfactory. Yesterday, on my way home, a car was merging in to the right lane (where I was, so instead of hit the brakes and risk getting rear-ended, I gunned it, revved to about 4300 rpm, and took off. Guess what, my car is still alive. After 157,000 miles of this, same tranny, engine, block, and everything mechanical. All I've ever replaced is the main radiator fan, $250. Not bad to be such a race car driver (like a race car driver could get 2 MPGs over EPA on trips like I do, HA).
#39 of 226 Re: Why never rev? [thegraduate]
Feb 10, 2006 (7:41 am)
Can you explain why those German compact cars are designed in the way I like?
#40 of 226 Re: Why never rev? [tthota]
Feb 10, 2006 (8:01 am)
Huh? Those german cars are also designed to rev high, for passing on the autobahn at 110 miles per hour. I doubt the Jetta 2.5, while having plentiful low-end, would be able to have get up and go if left in top gear to pass quickly at 85. It would rev higher, pushing higher into its horsepower band.