Dave the H.

I'm still learning the ropes with my still-new (one month old) 2007 TSX (NBP, 6MT), and questions about peak HP and peak torque come to mind.

In fact, I readily see and use peak torque, which happens at 4500 RPM. When accelerating for a lane change, say, or passing another car, I kick it up -- staying in 3rd gear, say -- and go past that RPM mark.

I love the way the car feels, pulling quickly at that point, with a great sense of control.

However, I have not hit peak HP yet, which at 7000 RPM is only 100 revs below the red line.

So, when might you use, get to, peak HP?

Isn't it odd to have peak HP so close to the red line?

In fact, for you, and you, and you: In what situations do you access the engine's peak HP? And why?

Dave, who drove an auto version of the TSX for a couple of days which made him very very happy to have bought one with a manual tranny

james41

It is a design decision that is, at a minimum, very interesting.

On the negative side- I see it as a way of posting 200HP for the car mags and web sites when the 200HP isn't that usable in a daily manner.

On the plus side- when you want to use it and are WOT the car continues to accelerate all the way to VTEC and then you get a little extra. This is great if you are passing, merging, or trying to put distance between yourself and the cars behind.

I'm also new to my car and I'm still making friends with its driving characteristics after 2200 miles.

rmpage

First, horsepower is a mathematical expression of total engine power, and expresses both the torque exerted by the output shaft, as well as how fast the shaft is able to rotate while exerting it. More here. Reading that page will clear up some things for you.

Horsepower sells cars. Torque wins races. Torque is what actually moves the car. It is what you feel when you mash the gas, get some wheelspin, and are pushed back into the seat. That is why you say you can feel it. Horsepower isn't directly perceptible like that, but it allows you to take advantage of gearing by spinning the engine very fast in a lower gear, the lower gear offering better torque multiplication than if you had upshifted.

At 7k RPM, you don't feel peak HP because, at the upper end of the rev range, the engine is not breathing very well and torque starts to fall off rapidly (a result of the K24 engine's design using the cylinder head from the 2.0L K20).

If you're shifting for maximum acceleration, you want to keep the engine revving as high as possible so as to let the transmission transform that high rotational speed from the engine into torque for the wheels. This is when you should be shifting right before the rev limit. Also, doing this will keep the engine in VTEC as much as possible, which will also help you gain speed faster.

GenXY2k

hondata !!! lowering VTEC hit point from 6000 rpm to 4500 rpm and increase revv limit all the way to 7600 rpm !! i have been reading good things about it , can't wait till to get it myself !! enjoy ur new car !! i just got mine a month ago and i m loving it !!

waTSX

As usual, an excellent, detailed explantation. Great link too. Thank you.

aaronng

HP is just a measure of work done based on torque and RPM. What you want is your peak HP to be as close to redline as possible. That means that your engine is efficient enough to keep increasing the amount of work done as you increase in RPM. If you have peak HP at 6000rpm and your redline is 7000rpm, that means that your engine is engineered well enough to spin at 7000rpm without damage, but once you pass 6000rpm, efficiency drops and your engine is just using an increasing rate of petrol without increasing the rate of work done.

Torque is what determines your acceleration. So to change lanes and accelerate, torque will be more important to determine whether a car will accelerate well when you mash the pedal. All HP does is let you know how quickly you will cover a certain distance when you accelerate. That's why you calculate estimate 1/4 mile times using HP and not torque.

ATsxMan8305

All great responses above, but I do want to mention one thing that hasn't been brought up. It's not just peak torque @ 4500 rpm, but the TORQUE CURVE (and HP too, for that matter) throughout the ENTIRE RPM RANGE. Yes, 4500 rpm is high for a peak torque, but the curve increases substantially to ~ 3k such that the difference between 3000 and 4500 isn't that much. That is a true marvel of engineering. This is why the TSX doesn't "feel slow." VTEC does boost the torque and HP a bit after 6K, which is always nice!

dolparism

i think the formular for horse power is.....hp = torque X RPM / 5,252.....
so peak horse power at highest RPM is normal....

aaronng

Not unless you lose a lot of torque at the higher RPM like the older engines. Then your peak HP won't be at highest RPM.

rb1

Actually, this is only partially correct. Horsepower is the best predictor of which car will win the race, not torque.

Diesel engines, for example, sometimes have almost double the torque of a gasoline engine. VW sells 150 hp diesels in Europe that have 300 lb-ft of torque, almost double what the TSX has. But the TSX will smoke those cars.

As a practical matter, you can have two cars with identical torque, but one with higher horspower. This means (usually) that the car with the higher horsepower simply holds the torque higher into the RPM band, so you can stay in the lower gear longer. That is what wins the race...

aaronng

That's just what some website quoted. Not necessarily correct. Torque is what determines how fast your car accelerates. HP is calculated from torque and RPM and is an indicator of how quickly a car will cover a certain distance. So for dragstrips, HP is a better indicator.

Wisc Badger

all i know is that in either HP or torque the 07+08's could use a little more of both of them.


C'MON HONDATA!!!!

Wisc Badger

oh and all you new 07 owners i just read from... please check out this thread.

https://acurazine.com/forums/showthread.php?t=38682