Question About Horsepower

So Toyota claims my truck makes 381 horses from the factory. How come every dyno test I see on Tundras, in the threads about different after market tunes, show the stock Tundra falling way, way short of those numbers? How can Toyota claim 381 when in fact, it's not really even close to that number, more like sub 300 horses?

Enlighten me

 

381 at the crank. You lose horsepower through the drive train.

 

You lose somewhere between 15 and 16% from what I recall. Every manufacture does.

 

Truth. Go look at any vehicles claimed HP and torque numbers, and then find a dyno of the stock vehicle. NONE will match the claim because of this.

 

Ok but sub 300 horsepower is more the norm which is no where close to 381. At best, the horse power of a Tundra floats around 300 and that sucks and is more like 20-25% drop in advertised horsepower.

 

Even more enlightenment LOL. There are two types of dyno’s. An engine dyno and a chassis dyno. An engine dynamometer measures at the crank and a chassis dynamometer measures at the wheels.

 

I understand what you are saying but so it's normal for there to be (up to a) 100hp difference in the two dynos?

 

I don’t know what percentage the Toyota tundra drive train takes away from the crank horsepower, but I would imagine it’s more than a small car or basic hot rod. Big transmission, to drive shafts and a huge rear end, I can imagine take a little more than 15%. I would suggest checking other manufacture competing trucks and figure out what their horsepower is at the wheel. I don’t think the Tundra is losing that much more than the competitors through the drivetrain.

 

I don’t know any actual numbers so I couldn’t help with that. I just know you lose quite a bit.

 

A quick Google search led me to another Tundra site. Looks like right around 300 hp to the wheels. That’s about 21 to 22%-ish? so I’m going to assume that the 15% loss is more for cars and older trucks with simple drive trains.

 

Our torque management system is so aggressive that kills our felt power.

This same system tho is probably why the transmissions are damn near bulletproof.

 

It isnt false advertising and it isnt isolated to Toyota.

The motor makes 381 horsepower, that's true. That is purely what the motor produces.

The drivetrain (transmission, transfer case, drive shaft, axle and tires) takes power to spin, this is true for any car and how much power depends on a lot of things. A front wheel drive car loses less power through the drivetrain because it has less parts to rotate. Rear whee drive or 4wd have a lot of parts to rotate.

If you ever have a truck and you put a bigger set of tires on it, you'll notice it feels like it has less power. The power of the motor hasn't changed, you've made the drivetrain harder to rotate. Think of it that way.

 

20% is about right for an average truck drivetrain, heavy duty stuff is harder to spin.

First gen tundras that make 245 horses at the motor generally hit 198-206 buff ponies at the wheel on a dyno.

 

"Horsepower sells cars, torque wins races."

Every manufacturer uses the engine dyno numbers in their ads because that is the "truest" and highest power output.

Let's say, HYPOTHETICALLY, that Dodge said their truck made 400hp at the crank, but lost 25-30% at the wheels (which was never advertised). But then Toyota advertised the Tundra hp numbers at the wheels, 300hp. Everyone would think that the Toyota is a dog and that Dodge makes the most powerful truck but in reality it made less power at the wheels than the Toyota.

So measuring at the crank is a way for them to keep each other honest in the loosest sense of the word. And as a friend once told me "Measuring horsepower at the crank is like measuring your dick, but starting at your asshole to the tip and back."

 

Just throwing this out there too, Ultra4 cars (off-road desert/rock racers) lose around 50% through their drivetrain. The top guys have 900hp engines and on a dyno make 400-500hp at the wheels. Point being, 20-30% seems like a lot compared to a car but when you take a transfercase, big differentials, etc. into account I'm not surprised.

 

I’m not supposed to measure from that point? Dammit! So I need to subtract 25% of my measured “horsepower” from the asshole. I’ll keep that to myself and continue to advertise crank horsepower.

 

In the olden days I followed the motorcycle publications where the manufacturers would make claims about the curb weight of the machine and the horsepower of the new engines.

Someone wrote in and was published in 'The Letters to the Editor' section of the magazine.

The weight and horsepower were 'At the Brochure' this fellow said.

YMMV ~ Your Mileage May Vary

 

You can learn a lot from this guy. It's worth the watch.

 

^^^^^


Add more hps with some or all of...
SC
LT headers
Catback X-pipe, w/ true duals and rebuilt cats

To get a little nuttier...
Port/polish heads and intake.
Add larger TB.

Even with all this, max on a 5.7 is going to be around 600 hp...meaning about 470 -480 to the wheels.

 

Thanks for the education, much appreciated

 

OK -

All "advertised" HP / TQ is at the CRANK...and not to the wheels, unless it is stated...at the wheels.

This difference is due to the "driveline" of applying that power from the motor...to the wheels.
Measuring the chasis (the advertised) power is difficult while the motor is still in the vehicle...and mods are added...so there is a CHasis dyno.

it is important to create a baseline on the Dyno - before making any modifications, in order to evaluate the modifications...so lets say...300 at the wheels (ball park)....and you do a modification...and the dyno pulls (assuming the same testing conditions, temperature, altitude, etc...) 320...you made 20 more over your baseline.


if you expect to buy a vehicle that is stated 380 HP (measured at hte crank) and expect to see 380 when measured at hte wheels...you are mistaken.

 

Turn off your AC... it will suddenly feel like you gained 50 hp.

 

Doesn't the Super Charger use 100 hp to make whatever hp it delivers to the rear wheels?

 

great explanations from everyone.

 

Truth in advertising should require the use of an *

 

Think @ViktorG would have a ton of info he can share on this matter.

Would you care to chime in.

https://www.tundras.com/threads/pro...en-awd-tundra-build.54634/page-2#post-1432039

 

There are some great explanations on this thread, my response won't be one of them. I had an f150 for 10 long years and the "Triton" advertised 300 hp and 450 lbs ft of torque. I looked everwhere, never found them. In fact my 1984 dodge d150 with 360 4bbl rated at 185 hp felt faster, and seemed to pull as good. With the Ford I always felt like I was back in the old Freightshaker and just had to make a hole in the interstate at the ends of on ramps. I seldom use more than half throttle on our short on ramps to get in the flow of traffic and at full throttle the Tundra will run off and hide from the Ford. Completely subjective but I never knew 81 hp would make that much difference.

 

I think it's less the increase in HP than it is the engineering to get it to the ground effectively. Look at the muscle cars that have stupid HP numbers, and compare them to cars that go faster on less HP. There are so many variables, that the butt dyno is the only one you should care about.

 

I have extensively dynoed 2 of my Tundras both stock, supercharged and with various mods such as custom camshafts, nitrous etc etc.
My bone stock Tundra put out 331whp and 336wtq on a Dynomite hub dyno.
My modded truck put out 570 whp a year ago.
As the others have explained to the OP, the manufacturer rates the engine on a chassis dyno, without a transmission or the rest of the drivetrain being part of the equation.
When a consumer takes the truck to a dyno, it measures the power at the wheels (whp stands for wheel horsepower).
Obviously, that number will be lower due to all the drivetrain losses.
Who cares what the number is anyways, unless you are using it as a benchmark for seeing if modifications are actually adding more power or not.
There is no other reason to waste money on dynoing a stock truck.

 

That's not terribly bad.