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Graph of acceleration in 2nd from below VTEC


Legendary Member
17 March 2001
St. Louis, Mo.
This could have been added to the thread about R&P but that one was getting stale and I thought this might be of interest to others. If you haven't read that one, Nsxtasy posted some excellent insight relevant to this.

I went out this afternoon and did a few runs in my bone-stock (drive train) '93 with a mild launch in first and an early shift to second so I could record the acceleration at wide open throttle from well below VTEC range on up. This link takes you to the graphs:

Because the G readings are a bit erratic during and just after a shift, on this run I shifted very early so I could get a clean reading at relatively low RPM in second. Keep in mind that the elapsed time is badly skewed due to a mild launch and very early shift. Both graphs are from the same run but the first displays acceleration and speed at the point where things settle down after the shift and the car is accelerating at WOT. The second shows acceleration and speed at the point where it hits max Gs for second gear. I have scaled the graphs so you can clearly see the steps as torque increases, rising from 0.37 to 0.40 Gs during a period of 1 second.. The ripple further down may have been the result of the bumpy stretch of road I was on (tough to find a flat empty strip on a sunny Saturday afternoon), or I may have been hovering right on the edge between 0.39 and 0.40. I've noticed similar bumps in dyno torque graphs from stock engines, so that may be part of it as well. I'll repeat these runs soon with double the sample rate and see if it looks any different. I also can't specifically account for the fact that the Gs do not increase slightly at higher RPM as does torque, but I'm guessing that it is offset by increased air and rolling resistance.

How does this translate in terms of speed and times? Working from the fact that 1G = 32.17405 ft/sec^2, each 0.01G increase in acceleration will yield an additional 0.2194 MPH per second. So in the example graphs, the car is moving at approximately 0.33 MPH slower by mid 2nd gear than if it had pulled 0.40 Gs throughout that three seconds. Of course, you would never shift that early in a race, and by the time you do shift you are already in the range of maximum acceleration even though still on the first cams.

So, it appears that the second gear hole is indeed almost entirely a result of the tall gear ratio as a torque multiplier and not from falling beneath the torque curve. (Kudos to Nsxtasy) By contrast, with a proper hole-shot 1st gear peaks at 0.77G and tapers off to 0.57 by 8000 RPM, still well above the 0.40G maximum in 2nd. Third gear drops to a dismal 0.26 but manages to sustain most of it to well over 100 MPH before physics take a noticeable toll. That gives you a good idea just how direct the torque multiplying impact of gearing is.

These graphs also further illustrate what dynos and our seat of the pants have always known, that the real beauty of the VTEC design is a VERY wide power band. It reminds me that the "VTEC range" is just as much about the low RPM cams as the high ones, possibly more so.

[This message has been edited by sjs (edited 25 March 2001).]
I was not able to access the graph. I got "Access forbidden from external hosts"

on the brighter side, great job on the information and interpertation. After reading your post, I now grasp why more torque in the low range isn't always better (such as in the Insight where you get 83ftlb at 1500rpm and 66 ftlb at 5000 rpm) because of torque multiplication through gears. (you don't mind if i take some of the info and use it in physics class do you?)

A general question of mine is why is there a "power band" in non-vtec engines? VTEC creates an early powerband or extends it because of radical cam grinds. From the graphs I see of non-vtec engines, the powerband comes when the torque curve starts to go down. If the torque is goin down, there is less force pushing the car foward; then why does that sudden burst of speed occour?

the curous admirer.
On my system, it's just the Netscape browser that gives the access-denied error message. IE seems to work fine...


[This message has been edited by Number9 (edited 25 March 2001).]
Im using IE 5.5 and being denied.

95 T bl/bl @ 35K
Originally posted by SigEpUCI:
Im using IE 5.5 and being denied.

I went to this link, got forbidden, changed the extension to '.jpg', got a Yahoo error, changed it back to '.JPG' and got the image just fine. Odd, but it worked
I can't see it either. Using IE 5.5

95 NSX-T Black/Black
Im using IE 5.5 and being denied.

I'm using IE 5.5 and I can view it no problem. So it's not IE 5.5 that's the problem.

I do have an account with Yahoo, though.
OK, let's try this link...

... hrmph, comes out smaller here.


I guess there's more than one definition of "power band". The common old-school definition with which I'm familiar seems follow the rule of thumb that gears should be spaced such that you shift out of one gear at max HP, and land in the next gear at max torque. The RPM span between those points is often referred to as the power band. No doubt there are plenty of other variations on the definition amongst different types of gear-heads. But, whatever the definition, all internal combustion engines have a power band. The differences have to do with how low or high they start and how wide and flat they are.

As for the sudden burst of speed, it may be perception, in part because all your senses get a rush as the engine screams, the scenery starts to fly past, and the suspension encounters bumps faster and sharper. But unless I'm missing something, you will get the most acceleration in any given gear at max torque. There's and old saying that toque is what burns rubber, but HP is what produces top speed. I'm not sure that's entirely accurate, but it sounds good. Get a ride (better in the passenger seat) in a stock Z28 or Mustang GT sometime. They feel incredibly fast even compared to an NSX which will stomp them to almost any speed above 50. That's torque. (Partly due to more displacement but also to a longer stroke relative to the bore, which limits reliable yet cheap RPM due to higher piston speeds.)

One of the main ingredients for more "power" from an NA motor is to turn higher revs because HP is actually just the product of torque and RPM. However, with a single fixed set of cam lobes that also results in peak torque being produced at a higher RPM and closer to peak HP. So as peak HP moves up, the power band typically narrows. That's why race versions of production engines are mated with much closer ratio transmissions. Besides adding gobs of power overall, well designed SC and turbo systems help to widen the power band by producing lots of torque at lower RPM, and are often happier (faster) with wider gearing than you might think. VTEC was the first production implementation (as far as I know) of variable valve timing and lift, placing two sets of lobes on each camshaft, one ground for high torque at low RPM and the other for efficient breathing at higher RPM, extending the torque curve and therefore producing more HP per cubic inch.

Ooops, I'm rambling. Sorry, I'm sure this has been covered a hundred times here. But I hope I have helped answer your questions NSXadmirer. If not, I'm sure someone can point you to much better and more detailed explanations of how all this works. And be careful of using anything here in your physics class, I for one am no authority.

[This message has been edited by sjs (edited 25 March 2001).]