I have been informed in other sections of this website that flywheel horsepower don't mean sh*# around here and this seems like the best place for me to take exception. I've been told that flywheel horsepower doesn't matter because it's where the tire meets the road that is important. Also it is easier to measure. So I will assume that it is the truck's power that is desired and not the motor's. If this is the case then a dyno's power calculations are bogus. A dyno measures torque which is a "real, indisputable measurement of the actual output at the wheel", and calculates the H.P. H.P.=Torque *5252/rpm. If it truly is the trucks power we seek, the engine rpm should not be a factor. The best measure of a truck's power would be a familiar formula involving 1/4 mile speed and the weight of the vehicle. On a dyno, A better approximation of the truck's power would be the area under the torque curve. My purpose here is not to bash dynometers because they are very useful tools for measuring rear wheel TORQUE. Still they calculate (approximately) the HORSEpower of the ENGINE at the rear wheels. If we are going to make comparisons between vehicles, lets compare apples to apples.

 

Horsepower is nothing but a numerical result of a mathematical calculation.

Torque is a true measurement of work performed.

An engine's ability to create X amount of torque across a varying RPM range requires tuning for airflow in AND out of the combustion chamber, efficient flame front travel, complete combustion of the fuel, proper air/fuel mixture, among other things.

800hp is just that. 800hp. What matters is the torque rise, the torque curve, and at what RPM it starts, ends, and the rolling average through an engine's powerband.

Horsepower is a word made up during the industrial revolution when engines, whether they be steam, electric, or fossil fuel fired, took the place of horses to perform work. It was a way for Billy Bob to advertise how much 'work' his engine could perform that people of that time could understand.

In some countries, horsepower isn't even a viable rating as kilowatt-hours and newton-meters are methods of measurement.

Then there's flywheel horsepower versus rear wheel horsepower.

An engine can make X amount of horsepower, but drivetrain losses reduce what actually makes it to the ground.

Brake drag, rotating weight in the transmission, transfer case, driveshaft, differentials, flywheel/clutch housing or torque converter, etc all contribute to drivetrain losses.

Get an aluminum flywheel and slide coupler, aluminum diff spool, aluminum driveshaft, remove every gear except for direct and back off your brakes and you'll have quite the dyno RWHP cheater rig.

Won't do anything worth a f**k except make big numbers, but it would look cool doing it.

Of course, then we could take all the dyno queens and put them on a real chassis load dyno like a real f'ing truck is tested and see which ones are still alive after 20 minutes at peak torque with 100% load.



rant off

 

 

I dynoed my 04 on a chassis load dyno. I got way different numbers then a dyno jet. Way nicer to tune a engine too. Peak tq comes in lower around 1650 on a load dyno vrs 2500 RPM on a dyno jet

 

dyno is a tuning tool

 

Great thread to stumble onto

 

As stated, HP is nothing more than an advertizing gimic. Something most north american dealerships just thrive on.

Most people, buy horsepower but drive torque and don't know the difference at all. Generally, a diesel, regardless of displacement will product much higher torque numbers that a naturally aspirated gasser. The numbers are closer on a turbo charged gasser but still advantage is diesel.

This is the power you feel when you take off at a light, pull up a hill or just accelerate to pass on the HWY.

I hope that helps.

 

gas engines will never produce the same torque as a diesel and the reason is the fuel diesel fuel as more energy than gas and it burns slower this means that the piston is being pushed all the way down its power stroke unlike a gas engine that has a fast violent combustion that last much less time

 

I disagree with that statement completely....

There are way to many outside influences that would compromise the end result or number to use this as a valid argument.Weather,air conditions,track conditions,tire choice/compounds and the amount of traction additive used on the test track could skew the numbers greatly.

Good example...
A 70 Dodge Challenger that runs in NHRA"s superstock class with a 440/6pack-automatic needs to weight in for SS/FA at 3790lbs with the driver when they cross the scales after a run for the record.That same car with the motor out of the chassis and mounted on a SuperFlow engine dyno made 625hp at the crank.The motor was installed and the car taken to a divisional event in the South in the Fall where the weather is known for good air.The record was set at 9.89et at 135.7mph.If you use your et/weight of the vehicle then it shows the car made 697hp at the crank which shows way more than it made.When in acuality the fact that we had temps in the 50's and had air which was down to almost 1800ft below sea level is what was the cause for the hp increase.

You may not like dynos,you may not beleive in them but one thing you can not dispute is the repeatability of the numbers in a controlled environment,something that can not be done at a drag/dirt/sled pull or any type of motorsport event.IF your dyno tuning is correct and your notes from that day are kept,then when you run into the same type air conditions during a competition event you should be right on with your vehicle for power.Bad air and poor tracks will cause the hp number to lower and good air and good tracks will raise the Hp number.This is why the dyno is a better tool to go by for power/torque numbers than any conversion done off of a timeslip.

I'd rather have you tell me your vehicle makes xxx amount of power based off of a dyno run number(either engine dyno or chassis dyno)that you tell me your making xxx amount of power based off of your slide rule math from a ET timeslip.When you try and tell me your making xx amount of power off of that timeslip I may ask you what the weather conditions were and use that to determine if you made the power based on what the motor is capable of all the time or what it made due to the conditions it was in.

Why do you think that all of the fast cars in competition(NHRA/IHRA/NMRA/WoO/USAC/ESS/IMSA/NASCAR etc etc)carry their own on board weather stations?.Its to optimize their vehicles engine output for the weather on the day they are supposed to race to gain the needed edge to ensure a win.

It was not too many years ago that only the big hitters in NASCAR and NHRA were tuning by weather.Now you go to the local tracks,both dirt and drag,and you will see wet bulb/dry bulbs,barometers,altimeters and computers used to figure out whats needed on a given night.

Yes,you may not like the dyno and its numbers,but,as for actual numbers made they are some of the best tools to use to attain a good baseline and ensure a controlled atomosphere to gain those numbers........Andy

P.S.-Dan....You would be amazed at how many people I have said to lighten the drivelines up for dyno events and how many look at me like I am nuts.The aluminum driveshaft in my Superstock car was good for a couple of hundreths and when your in a heads-up class race it may be all you need for the win.

 

x2


What bugs me about dynos is the people who think they automatically have a fast rig because it dynos X horsepower and Y torque.

I will agree that the dyno is a more consistent tuning tool but, like you said, there are way more variables that factor in to a track time....and depending on the type of dyno a guy is running on, there is specific tuning for that as well.


PS....The ASCS and WoO boys have had weather stations in their trailers the last few times I've been to the Nationals.....