I wouldn't call it a horsepower loss so much as an Acceleration loss, but that's just me nit-picking. An excellent read, thanks for posting it!

 

I actually meant drivetrain loss, does that make sense?

 

I've seen dyno plots that measure actual force at them rear wheels in different gears. It's a huge difference between gears, and actual engine torque.

 

As in, the force at the rear wheels continues increasing with each gear, while engine torque stays the same, correct?

I wasn't trying to pick on you so please don't take it that way. What I got from the article though is that lower gears always give you better acceleration for any given horsepower. So much so that even if you go past peak power the lower gear will usually ACCELERATE faster than a bit more horsepower in a higher gear. This explains why concentrating your shifts on peak horsepower doesn't always result in the best track times. Of course this will vary from car to car, engine to engine and gear ratio to gear ratio which makes for hours of fun experimentation...

No I didn't take it that way at all. The point I was trying to make about horsepower loss was directed at the drivetrain loss "debate". This article explains how it's not a fixed percentage, but a value which increases with increasing acceleration (power). There's always been quite a bit of dissent on that topic, as well as the optimum shift point.

This all came about because I was playing with a g-force app on my phone, and wanted to figure out what the numbers I was getting meant, and how they stacked up to different fast cars.

 

I wasn't trying to pick on you so please don't take it that way. What I got from the article though is that lower gears always give you better acceleration for any given horsepower. So much so that even if you go past peak power the lower gear will usually ACCELERATE faster than a bit more horsepower in a higher gear. This explains why concentrating your shifts on peak horsepower doesn't always result in the best track times. Of course this will vary from car to car, engine to engine and gear ratio to gear ratio which makes for hours of fun experimentation...

 

Someone on GTOOC worked out final torque vs gear and it was a real eye opener!.

 

This stuff is pretty obvious if you have ever played with a hp to torque conversion calculator or needed to interpret a dyno plot that has not torque curve.

Here are some charts I made years ago when thinking about why having more HP with a big cam motor was worthless when my rev limiter could not be increased above 6200. Went much faster with much less HP but better power throughout the gear, less lag, etc.

I have the two different common final drives that I can use (which actually have different ratios in the gear stacks) and then the average power improvement if I shifted a few hundred rpms higher. If my power flatlined or slowly fell off I could really rev high before it makes sense to Shift.

The thing these charts do not help you visualize is the mechanical advantage of real work done at the tires with gearing changes. 3.0ish:1 1st gear ratio vs a 1.0ish:1 4th gear makes a huge difference. .

 

I have this in Excel. N.B. it is currently geared for my Toyo R888 315/30/18 tyre circumference.