Braggin rights is the best way to describe what a dyno readout is, for the majority of us who do not race our work trucks most of the dyno readouts mean nothing. A loading dyno is a tuning tool as you can fine tune the engine while the unit is operating under normal conditions over a period of time. The ultimate test is every day use while working with a load, crawling mountains grossing 20-25,000lbs on 6-8% grades shows consistant pulling power. Times have not changed, "he who gets to the top first with same load has got the biggest horse" and no paper printout will change that. If you race, a 1-2 second number generated on a dyno is an indication of what might happen, reality is the guy with the trophy at the end of the day at the track. When your truck is at 210F, 2200rpm, 30-35psi manifold and it has been doing that for 15 minutes up a hill and maintained a consistant speed more or less grossing 21,000lbs like my truck I am smiling . When an owner has a dyno sheet with big numbers but wont load and play in the hills it is nothing but course TP. I imagine it is the same at the sled pulls lots of bragging and numbers flying around but when the hammer drops reality sets in. PK

 

If that r1 is rpms them using hp= (rpm*torque)/5252 then
297hp = 567 ft lbs

 

No, the R1 Trq isn't RPMs. If it was RPMs then the R1 Trq figures would be higher at 50 and 60 mph, not lower. But thanks for the stab at it. I'm still trying to figure it out too.

Steve

 

My bad

Lets make it easy- using the same formula and solving for torque:

torque = (5252*hp)/ rpm

So if you have 297 hp @ 60 then divide 1559844 (5252*297) by your rpm @ 60 and you'll know your torque

 

I guess it's time for me to give me long-winded standard dyno spiel.

A DJ is the most reproducible and consistent "dyno" around-- period. This is because it eliminates the variables of the operator and the load. You can take DJ numbers and they will be consistenty from one DJ to another with GREAT reproducibility.

So, if you are NASCAR team looking for that last 2.2HP testing different water pump designs, or different gear lubes or what have you, then a DJ is the only tool that will help you. Any other dyno is simply not consistent enough-- too many variables.

But the DJ numbers, as consistent as they are, could be way off. Your NASCAR engine may only make 645hp, not 720hp.

BUT NO ONE CARES IF THE DJ IS OFF


Why? Because it doesn't matter. The pros who use a DJ know how to use it, and they simply use it as a right direction/wrong direction tool. It doesn't matter what the number is-- what matters is how is compares to your baseline. THIS IS THE PROPER WAY TO USE A DJ "DYNO".

IN other words, you don't use a DJ to tell you HOW MUCH hp you are making, you use it to tell you if you are making more or less than you did before.


A superflow, Mustang, Dyno Dynamics, or whatever can probably come closer to an "accurate" number. But even if it IS more accurate, it's still worthless.


Pretend that you bolted a 500lb flywheel to your truck:
- What would happen to the dyno reading on a Dynojet? (it goes down)
- What would happen to the dyno reading on a Mustang? (it goes up)
- Has the actual power output of the engine changed at all? (no, it stayed the same)

Or ask yourself how the dyno results of a motorcycle would compare with that of an 18-wheeler, accounting for flywheel effect of the vastly different engine sizes.



So, you should use the dyno that best approximates what you want to do with your truck. If it's towing performance you want, then a load dyno is for you. If it's just acceleration, then a properly setup intertial is what you want.

Since dynos are so flawed in the way they measure hp (indeed, the whole concept of HP is pretty worthless), then don't count on the numbers they produce as being accurate (defined as true to actuality).

Instead, use a dyno as a right/wrong direction tool, and depend on it's PRECISION (defined as reproducibility), not accuracy.

There's no truly accurate dyno. So pick one that's precise (like a DJ) and do some tuning.

jh

 

HOHN, thank you.

That is exactly I have been saying all along on here. An inertia 'dyno' is a fabulous tool, and I have said that a million times. I have even personally used an intertia 'dyno' on my race car. Yes its great, but IT IS RELATIVE!!!! It is not A DYNO !!!!!!!!!!!!!!!!!!

A Dynamometer gives an ACCURATE reading of ACTUAL torque produced BY ACTUALLY MEASURING that toruqe and also recording the RPM's at which that torque is produced, thus giving and indication of ACTUAL POWER produced. A real Dynamometer will give you a reading within 1% of EVERY OTHER BRAND of REAL Dynamometer EVERY SINGLE TIME.. ( not including weather factor corrections).

That is all I am saying. When someone says 'how much power did you make' so you tell them X HP and Y torque, and then you need to clarify which "dyno" you used, thats an indication YOU WERENT USING A DYNO, you were using a RELATIVE TOOL.

And thats, OK, just understand the NUMBERS DONT MEAN JACK.


Sheeeesh, THank You

KP

 

I'm no expert and what you say sounds logical. But can you explain this one...

Went to a Mustang 250 Dyno Day. Loaded the dyno to the empty weight I use when hauling... 7400 lbs (Truck, me & full fuel).
Two pulls on the dyno were very close, but was only getting 38 psi boost and a lot of smoke. ( I can make 45 psi (gated) on the Hwy).

One more pull at 9000 lbs dialed in to try and get full boost. No difference in boost or HP.???
RJ

 

i will take a stab at why you were getting only 38 psi when dyno'ing at a 7400 lb load: wind resistance or lack thereof. the front surface area of the truck pushing the air at 60+ mph is a large load that doesnt show up on a stationary dyno, and that decrease in load may account for the decrease in boost.

but thinking about it from a different side, the cooling effects of that air flow over the intercooler isnt happening as effectively (provided some sort of fan was setup in the front), so boost shouldnt decrease as a result of that...

as to why 9000 lbs didnt make a difference in boost or HP, well

 

Thanks for the info guys. These last few posts have been very enlightening for me and hopefully others too. If phatboy's correct in his equation, and I don't see why it wouldn't be, all I need to do is see what the RPMs are at 60, 50 and 40, use these figures and calculate the torque measured by this particular load dyno. It was also informative to get Justin's explanation of dynos - good stuff.

On a side note, has anyone ever heard of Pro-Tec Diesel Fuel Conditioner or seen or read of it reducing smoke like the diesel tech told me? I did a Google search and didn't really come up with anything informative, just a couple of hits from distributors and little else. The print on the can says "Formulated to control biocidal growth and increase fuel stability while reducing corrosion and injector wear and clogging thus greatly reducing smoke emissions." I bought it mostly for the reduction of smoke to help pass the emission test. Guess I'll try the stuff since I've already bought it and I'll also put the stock 95 plate in for the emission test too so the truck won't be fueling nearly like it can now then put the 10 plate back in after the test. I'm temped to try just the fuel conditioner alone but the retest costs $35 and I don't want to risk not passing as I need the new license plates soon and don't want to have to wait for something else I have to do to get them and possibly at more cost yet.

Anyway, if anyone knows anything about this stuff I'd love to hear back.

As always thanks for all your comments and knowledge.

Steve