Horsepower and Torque

the rest of the story

[lawman]

ken_b asked about my power numbers in another Foo thread - [webmasterworld.com...] - and I gave a partial answer. For anyone who cares, below is a more complete answer.

As you all know I had my car dynotuned last month. I previously had it tuned at the same location January of 2012. I got the run files from January today and took a look. Max numbers were:

2012 2014
690 687 Horsepower
669 688 Torque

Appears that HP number is down slightly and the Torque numnber is up noticeably. A closer look reveals interesting info. First off, maximum HP on the 2012 pull (690.09) came at 6230rpms. At this engine speed the HP on the 2013 pull was 686.05 - off about 3 HP.

However, at 6430rpms the HP on both pulls was virtually identical at 685. So really the HP levels of the 2012 and 2014 pulls seems like a tie. Nope, but I'll get back to that after we look at the torque numbers.


(Note: you can skip over the next two paragraphs if numbers make your head spin)

There is a marked increase in torque in the middle of the rpm range on the 2014 pull. As you recall from the above chart, 2014 maximum torque was 688.58 ft/lbs. This came at 4172 rpms. The 2012 pull at the same rpm level registered 668.75 ft/lbs. THe 2012 maximum torque of 669.75 registered at 4542rpms. The 2014 torque at that rpm level was still 16 ft/lbs higher.

You don't have to remember this but in case you want to know, the formula for calculating horsepower is Torque X RPM / 5252 (the horsepower/torque curves will always intersect at 5252 rpms). Assume a torque level of 685 at 4542 rpms, plug it in: 685(ft/lbs of torque) X 4542rpms / 5252 = 592 horsepower. This number is confirmed by my dynojet graph.

(OK, you can start reading again)

I guess I said all that to say this: HP and torque are about a wash between the pulls at higher rpms. But in the mid range, I'm running as much as 20 ft/lbs of torque more on the 2014 pull vs the 2012 pull, and almost 18 horsepower more in the 2014 pull than the 2012 pull.

The take away is this - just looking at the maximum numbers posted on the graph doesn't tell the whole story. For those of you interested ONLY IN HORSEPOWER NUMBERS, it is NOT a tie as we figured above; I'm actually up nearly 18 HP.

Differences between the two pulls - 72 lb injectors on the 2012 pull and 80 lb injectors on the 2014 pull. I also installed Magnaflow resonators (straight through pipes) before the rear axle between the two pulls.

Are there any questions?

[edited by: lawman at 5:01 am (utc) on Apr 12, 2014]

[phranque]

how does it sound/feel 2012 vs 2014?

[ken_b]

Thanks for the info Lawman, pretty interesting. I'm not a racer and not really up on all this stuff, but have great memories of going to the strip with my older brother who raced a little when I was younger.

Are there any questions?

Why yes, yes there is :)

How has this all affected the performance at the track, if you've had it at the track yet this year? Or what do you hope to see? (Here in the frozen tundra the strips are probably still iced over)

[lawman]

phranque, The resonators got rid of most of the raspiness at all rpm ranges. The sound is definitely mellower at lower rpms and I can get out of the neighborhood without the neighbors calling the cops.

ken_b, I'm hoping to get to the track by the end of the month. If I can get traction (I launch at about 3500 rpms and slip the clutch on the launch) I'll be in the 10s (how deep I don't know) and should trap 135 or so.

BTW, I'm on my third clutch.

[engine]

Interesting figures, thanks for sharing that.

>BTW, I'm on my third clutch.

LOL

Don't worry about the clutch:They are replaceable. The key is avoiding wheel spin, which is wasting time and wrecking the tires (kids think wheel spin and tyre smoke means fast, lol, it looks good, and is fun, but it's not fast).

Now that you have a new map you'll just need to practice control to bring in the power at the (new) right point. Immediate take off may seem slow, but get the car moving, then bring in the power. The lower revs and torque band are going to be so much more fun than having to rev high. I'd be very surprised if you were not much, much quicker.

[lawman]

You are correct engine. Launching is key for a good pass. My car does not have launch control but my tuner said he is hoping to have launch control built into his software before the end of the year.

[engine]

Oh, yes, launch control is fun and often consistent, but there's something self satisfying about getting a great start with your own skill. :)

[ken_b]

So now I'm wondering what kind of tires and pressures you run at the strip.

[lawman]

engine, I have no skill. :)

ken_b, at the drag strip I use M&H Racemaster drag radials. They hook better than Mickey Thompsons for me. I mount them, drive them to the track and drop the pressure to 16psi. When I'm done I air them up, drive the 12 miles back home, and put my Toyo R888s back on.

[engine]

Oh, Lawman, you say you have no skill. You have enthusiasm, and the opportunity to practice. You can do it, just keep at it.

One way to improve your skill levels is to go onto a skid pan. Spend some time there using accelerator and car control. No need to use the brakes. lol

Having said that, when you get the launch control, you'll wonder why you didn't get it sooner. It's fun whichever way you go.

[lawman]

Not exactly on topic, but . . .

Last night I hung out with a bunch of drivers with high performance cars at the Local Steak n Shake. When I left I punched it and passenger exhaust pipe immediately separated at the clamp joint. Pulled into a parking lot and looked - the way it was hanging down I was afraid it might catch the pavement and cause some bad damage. Didn't feel like waiting two hours for AAA (they're always two hours away from anywhere). So I locked it and got my son to pick me up. At 7:53 this morning I called AAA. By 8:53 my car was unloaded at the muffler shop. That's the fastest AAA service I've ever had.

[lawman]

Turns out the guy who rebuilt the engine did not secure a slip clamp on the passenger exhaust pipe. Muffler guy had it fixed in 5 minutes. Purring like a kitten.