Hot Rods Horsepower minimum, got a number?

It's funny but I have a little box with wheels with 130 hp that would run a lot of 300+ hp cars into the ground on the long roads when you get up to real road speed for hours on end. I've been thinking about putting the motor in a T modified and figuring out final gearing to be the same as it is now and going out to play.

 

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The Chevy has a whopping 200RWHP and it is fun. Anything I put together moving forward will need to have more than that!

 

Straight up legitimate question.......
As you say, power = torque * rpm. Wouldn't that mean that the only way to add power is to increase torque, or to raise the rpm where your torque peak happens? I don't get how else you can "insert more power" when power is a function of torque and rpm.

 

Power is Torque x RPM.
there is 2 basic methods for more power , Increase Torque, or Increase RPM [without losing torque]

All the car really cares about is Power [or torque if you want to argue] at the rear wheels
There can be 2 different engines with the same power but one needs to rev higher to achieve this.

If the gear ratios are used to correct this ,so the wheel speeds were the same then the power at the wheels is also the same .

If there was Zero drivetrain losses the power output of the engine would be identical to the power output at the wheels
300 ft/lbs at 6000 rpm = 342 hp
Now if we geared down the output 4:1 the torque is multiplied by this [and the output speed divided by this]
1200 ft/lb at 1500 rpm = 342 hp

 

Here's a little test I did years ago. First run with regular gearing . . .


. . . and then a little gear change . . .


Speed was about the same, but a second quicker E.T. (Notice how courteous I am while drag racing -- I've always let the other guy go first. Could be why I switched to Land Speed.) I wouldn't recommend this for everyone. It took a lot of arm power to turn off the strip with all the added caster.

 

^^^ That is how I understand it too.^^^
I don't get @G-son talking about adding power, as if it was a separate entity.
You get power increases by tweaking torque and rpm. Add torque, and increase the rpm where the torque is most effective. The power increase follows as a result, doesn't it?

 

I was referring to using different engine rpms & gear ratios to get the same wheel speed and compare wheel torque to see what will give you the best acceleration. The peak power engine speed will produce more wheel torque than the peak torque rpm - for that matter, any rpm with more power than peak torque rpm will beat peak torque rpm.

You don't need to raise the peak torque rpm, you just need to raise the rpm more than you let the torque drop off (at rpm above torque peak). As long as the rpm rises more than torque drops off the power will keep going up. Peak power is the rpm where torque begins dropping of faster than rpm increases.

 

I am curious if this was your Ride & let's hypothetically say 500 pounds of torque , 500 hp ,on these tires and this light of a car 1,300 -1,600
What would you do for traction ?
@ a Guess , not have drove yet ,
I would start with a 3:00 gear , 2,000 -2,400 stall Or maybe 2:90 & 2,800 stall ,
& still need to know & have throttle control before WOT .

 

^^^^When the 14" drag slicks are being driven by a blown hemi, does having front spindle mount discs really help that much with 3" tires? This reminds me a of a hot Vegas hooker or that turbo pogo stick @Moriarity owns, fun to look at but do you really want to hit it? HP per IQ ratio needs to be considered.

 

Less than 3000lbs and more than 300HP with a nice torque curve is perfect for the street…

and I’m sure a lot of people that think they have 300 HP would be shocked if they really knew what they had…

my motor is good from 1800-6000…don’t think I’ve seen 6K…but I do like to reach the speed limit as quickly as possible ,when possible, and when it’s safe to do so…and ya feel torque on the street and in the seat

 

Oh, you're changing the gear.

That's just what I said above....in a different way...

 

I’ve been watching Nick’s Garage from Montreal on YT for over a year now. He specializes in building and dyno testing OT muscle car engines from the late 60s and early 70s. Most builds end up pretty damn close to the OEM specs (gross) for hp & torque even with some enhancements. You’re doing real good if you’re achieving 1 hp/cubic inch using pump gas. A recent test of an Olds hi-perf W31 350 “only” made 325 hp.

 

Hmmm
Where did I put those leaf blowers?
Hold my beer!

 

More formulas....you engineer types.

 

My "tractor" motor made
665 tq @2500
362 hp @2500
But somehow it still made
642 tq @6000
791 hp @6000
I won't mention the extra tq it made in between but will say it broke 700 by 3000 rpm and didn't dip below that 700 until 5200 rpm
So yup, all the character of a tractor

 

1000 hp, nah. 500, probably and it won't be 100 grand.

 

Horsepower is bullshit. Torque makes shit move.
275 hp and 375 ft lbs is way more fun than 500hp and 175 ft lbs.
Don’t agree? Buy a “Naws” kit for your Honda and try that out…… lol

 

Don't base everything on only his channel, I watched a few of his one sided mopar episodes, there's plenty of other well documented channels that make more power with same type builds.
This guy is just one of them

 

@twenty8

That is back to front
Torque is force over distance [met by resistance]
And as time is factored it become power [Power makes shit move]

Torque and Power are like twins
You don't feel the effects of torque unless you ARE the actual resistance [but you do feel power]

If you put the nose of the car against a brick wall while in gear there is torque [force met by resistance]
When the resistance is overcome and the wall collapses, and the car f***s off thru the other side, you feel the power [because of velocity]

Increasing torque multiplication will increase the torque against resistance [which is why a car accelerates better in lower gears]
Larger torque output also is the same.
Eventually there becomes a point of equilibrium where there is not enough power to overcome resistance [velocity is part of this equation now] and the car literally won't accelerate any further
This is the aerodynamic "brick wall"

The rate of acceleration is calculated as thrust [at the tyre footprint] against resistance [mass]
Thrust is engine torque x total torque multiplication ÷ wheel radius.
3000lbs thrust in a 3000 lb vehicle should accelerate at 1g

With power factored this theoretical 1g could be 0-50 mph or 0-100 mph depending on power output.
The 0-100 mph example would need 4 x the power of the 0-50 mph example.

This ^^^^ is why the stock eliminator racers stack as much mechanical leverage into their setups
They are usually at peak power approx 50 to 100 yards from the end of the quarter [the gains are made from leaping out of the hole]

This almost sounds like a contradiction, but acceleration is actually a constantly changing velocity [velocity is force/time or torque/rpm] as a vehicle accelerates the torque "could" theoretically remain constant but the RPM increases , therefore power increases

 

A guy built a curved dash Olds replica, the original had a 1 cyl, 1 HP engine. His had a 2 cyl, 2 HP engine. He figured he doubled the number of cyls & doubled the HP so it gotta be a hot rod...

 

My daily off topic economy car has 165hp at 6500rpm and a 5 speed stick. It weighs about 3000 lbs. 90% of the time I don't turn much more than 4500 rpm with is only about 110hp. 99% of the time I am running up on all the traffic around me.

My off topic late model '93 Mustang has just over 400 hp, a TKO600 5 speed and weighs about 3400 lbs. I can barely use it. By the time I'm in 4th gear I'm at going to jail speeds.

For my '32 Tudor perfection would be 300-ish hp and a 4 speed or a 5 speed. I'm not looking for a race car I can drive on the street. But reality will probably be half that (if I'm lucky) as I wanna keep the car Flathead powered and I don't have deep pockets.

But really...HP is kind of a bogus "power" number to focus on. Torque is work. HP is an expression of torque versus time. Regardless of the HP I want as much torque as possible as soon as I can get it and I want to carry as much torque as possible through the revs up to around 5000 rpm. After all torque and horsepower cross at 5252 rpm.

 

We should have a HAMB bench rather meet. Like soap box races, we all bring our fast work benches to a sloped racetrack and let em go! Bench racing! It's awesome baby!

 

A lot of discussion on HP vs Torque when actually they are closely related. As stated HP is a function of torque so at any given RPM the higher the torque the higher the HP will be. The bottom line is cubes rule. Small blocks with snotty cams are fun IMO but are harder drive well.
Bottom line :
Horsepower minimum = how slow or how fast do you wanna go?
Light cars need less HP
More speed = more $$$s

 

Hey Kerry, that was not me. You have quoted @dumprat .....

 

I replied to Dumprat but also tagged you to this response regarding your original question

sorry for any misunderstanding cheers

 

I think the forebears of prewar racing understood that. This vid always brings a smile to my face. Lol!

 

Always a blast to drive my T roadster had a 107 rear wheel rated factory horse power engine 4 speed 427 gear. 2050 pounds . Drove the crap out of it 22 years 9 states. Never got out ran by a flat head at nostalgia drags