DaveFunction2ND

iTrader: (8)

Tuning and Power Measurement is done on a Load Based dyno. ONLY Power measurement is done on an inertia based dyno.

What is Power?

There are many terms in the market place for power but the only one that is important to a tuner of any competence is torque. Torque is the be all end all of tuning information. A good tuner with the correct dyno is able to use this information to provide a safe reliable tune while still making a reasonable amount of power.
The term "rotational force" is the key concept we are honing in on. Torque is the actual measurement of the rotational forces that transfer from the exploded gases inside your motor through the piston, through the rod, into the crankshaft, through the flywheel and then onto the drivetrain.

Horsepower is an averaging number. I feel that the OEMs have marketed it as a number to sell cars since it is higher (we’re all human, bigger’s better right) but has less significance on how fast the car is then torque. It is not an accurate measurement for tuning if an accurate torque figure is available.

The mathematical calculation for HP is Torque x RPM / 5250. This is why Torque Curves and Horsepower Curves ALWAYS cross at 5250 RPM and also why HP exceeds Torque above 5250 RPM. This is also why high revving motors can make high HP numbers. As your RPM’s increase you are bound to increase your HP even if it is a function of RPM and not the actual power the motor is generating. Ultimately your HP is based on your Torque with an additive introduced. So as a tuner I want the purest information. That pure number is torque. If my torque goes up invariably my HP does too.

So that still does not really explain it right? Of course not. The concept I’m trying to explain is that Torque is a direct derivative of timing. If the gases inside the motor explode too soon then the torque being generating is not being transferred into the crank. Where is it going? Into the heads, into the top of the pistons, into the rods.

So that we all understand properly. Timing is torque, torque is timing. Timing is power, timing is also damage to the motor. Torque is power; torque is not necessarily damage to the motor if the correct timing is used.

The Physical Differences

Lets start with the physical differences between an inertia based dyno and a load based dyno.

Rollers

Inertia – SINGLE Large Circumference Extremely Heavy Rollers. The roller has no control over itself. So think about this. When you start to push a dead car it’s very heavy, but once its moving it becomes easier and easier to accelerate it. This is how an inertia dyno acts. This is fine for power measurement because the computer knows how much the roller weighs and how much the roller will accelerate on its own. For tuning it makes it a variable load. A motor accelerates in a linear fashion, fighting the forces of the vehicle weight, rotational forces attached to the drivetrain, aerodynamic drag and many other obstacles. At a certain point the Inertia dyno’s roller weight can actually begin to spin the motor due to momentum. This does not happen with a load based dyno.

Load – Two Small Light Rollers attached to a Retarder (Think really big electric motor). This motor and the hand held remote control the “Ramp” rate of the motor. In other words it tells the car how fast it can accelerate. This keeps a constant load on the motor much in the way it happens on the street.

Securing Method

Inertia – Straps car to ground with minimal tire contact patch on the roller. Because of the single roller design and the overall size of the roller the vehicle can be strapped in-front, in the center, or behind the roller centerline. This changes the traction of the tires and also how well it can accelerate the roller.

Load – Straps pull car into the valley of the two rollers. As the vehicle accelerates it “Pushes” itself “Into” the front roller and attempts to fight its own weight, gravity, and the straps to lift out of the valley. Something that is practically impossible. This also creates a very stable environment with extreme repeatability. Traction is never lost! The tires are always in the same place even if the vehicle is unstrapped and restrapped or dyno’d thirty days from now.

Since the load based dyno has been able to eliminate any mounting based issues it immediately becomes the more accurate device. This is 90% of the battle. Once we are able to secure the vehicle properly we are then able to add a measurement device to the roller that can sense even the smallest changes at very high sampling rates and is not disturbed by minor outside influences.

The Computer

The Dyno Dynamics Dyno takes it a few steps further. Within the computers interface it allows me to measure the real time torque. This number is accurate to a very small amount. I am able to hold the motor at any engine speed and open the throttle up to any range and it will not accelerate beyond the specified RPM. With this method I can see exactly how my timing translates into torque.

In the graph screen I am able to see Torque drawn as the motor accelerates. Either while in a run or once a run is complete I can zoom into the graph and look at 100, 1000, or whatever increment of RPMs I desire. This allows me to refine the tune to an exceptional degree with no concerns of whether the dyno is reading accurately or not.

The Proof

Here is an example of the infamous car I tuned most recently. Each higher dyno graph line is after I have added some timing to a conservative base map. This precise type of readout is not possible with a DynoJet.





Here is another example of a zoom into a graph so that I can refine certain areas. Here I have added timing just to a certain RPM range. This can tell me if I will make more power or smoother power in other areas of the graph.







The Conclusion

If your tuner is tuning on an inertia based dyno then they are not tuning your car. At best they are guessing and hoping for the best. I know; I’ve tuned on DynoJet Dynos. I know I was guessing many times when I tuned on those dynos. That is why I always, always confirmed my tune on the street. A DynoJet only provided me a safe place to accelerate the vehicle to triple digits in an efficient time period.

I'll try to answer any questions anyone has and add to this article as time allows. There are many more features an functions of a DynoDynamics Dyno that have yet to be explained. Some that I am even not familiar with just becasue I don't use it for the same things that other shops use it for.

It is also proof to me when three major car manufactures use the Dyno Dynamics dyno as their in-house dyno. This includes Subaru, Toyota, and Honda. All companies that involved very deeply with racing, from Formula 1 to Rally.

VIZAGE

iTrader: (20)

Makes you wonder why shops spend so much money on dynojets?

failsafe306

iTrader: (38)

Excellent write-up, thanks for taking the time to do that.

Devil Z

iTrader: (6)

Interesting . . . . . so guys that use a Dynojet (inertia dynos) must tune their cars on the street?

AboostedG

iTrader: (6)

I'd have to say that was a book worth reading compared to some other long posts, thanks for the info!

Ninja350Z

Thanks Dave for the write up.......good info.

AboostedG

iTrader: (6)

4 posts at the same time..

failsafe306

iTrader: (38)

I heard that if you get 5 posts in a row, you'll bring down the forum permanently.

Audible Mayhem

iTrader: (48)

you cant change the corrections on a dynojet. that is WHY its the industry standard.


if you make 400 whp , the car HAS 400 hp, we cant "make" it have it if it doenst put it down.

thats why everyone likes dynojets.

how come all these big big high hp DD cars dont put down time slips??

i have only seen a few.

correcting a dyno chart is like correcting a trap speed. "Well, my car really trapped 116 but corrected i think its a 135!!" doesnt happen, so why does it happen with dynos...

too many variables, too many corrections.

you cant trap faster than your car really is, it IS the best method of hp...

Devil Z

iTrader: (6)

So how do shops like GTM and stuff tune their cars . . . . if they CAN'T TUNE on a Dynojet . . . . again I am a newb and I know nothing.

So please help me out.

Is it all in the road tuning?

Audible Mayhem

iTrader: (48)

i "tune" all my cars on a dynojet, i tune my personal car on a dynojet and bring it to the track and datalog the same thing.

its is DEAD on every time. how much more can the 1/4 mile track be "real world"???

DaveFunction2ND

iTrader: (8)

Well I guess that would work but DD pretty much always read lower HP then DJ. Regardless even DJ is now making Load Based Dynos. We are not discussing power #'s we are discussing tuning. I wish I could find some of the articles that included interviews with the owner and original designer of the DynoJet. Even he states that his HP # is based on no known standarized calculation. FYI Dynojets were designed originally for big HP motorcycles becasue at the time the existing dynos were very unstable. Through marketing and ubiquitousness throughout the US DynoJet has become the defacto HP tool. But if you read my post I state the following very clearly. The DD is a tuning tool and secondarily a power measurement tool. The Inertia DJ IMHO is a power measurement device. Proof is in the fact that even DJ is now making load based dynos.

DaveFunction2ND

iTrader: (8)

1/4 is a small representation of the real world. Most of the 1/4 mile is WOT. Sure give or take a few pedalings here or there. The REAL real world is many different loads at many different throttle angles. How do you tune that on a DynoJet?

Sean

For everone that claims Load Based is better, you will find another that claims Inertia is better.
It's like Ford and Chevy supporters fighting to the death.
I would be happy to have either dyno in my back yard.

Audible Mayhem

iTrader: (48)

arent you tuning for power though?? i think you are confusing the customers with too much info. people have tuned thousands and thousands of cars on dynojets. the industry standard is the dynojet for a reason...


the best place to tune a car is on the street, hands down, thats the only way to replicate how a car is REALLY going to act....

DaveFunction2ND

iTrader: (8)

They can tune a car. Its is the fact that the line between safe power, great but unsafe power, and the happy medium in-between is very blurred. Also for WOT the DynoJet can be a decent tool, but who drives at WOT all the time? Most of us here use our cars every day. Not strictly at the track. Road tuning is still required even after a DynoDynamics Dyno if only to confirm the dyno tune. The REAL world is the REAL WORLD. A Dyno can never replicate everything.

sentry65

iTrader: (11)

I think the dyno-dynamics is a nicer dyno as far as features and real-time graphing the charts selected, but I don't think dynojets are crap either


I know when I was at GT Motorsports with Sam tuning my car, he got things really dialed in on the dyno while monitoring everything else via the laptop which logged fuel pressure, A/F, intake temp, EGT, boost, and about 4 or 5 other things at least. There were a bunch of graphs all being shown at the same time. To my knowledge, he was mostly going off that that info and then looking at actual dyno chart every now and then to confirm what it seemed like he already knew as far as what areas needed work and which areas were doing fine - that was my take on what was going on anyway. I don't wanna be putting words in his mouth

Later he road tuned it with him driving the car and then also with me driving the car. This whole thread might end up turning into a debate between load based dynoing vs road tuning etc. I think either are good methods

DaveFunction2ND

iTrader: (8)

Agreed! But I know much better what is going on in the motor with the DD at all throttle angles then I would with the DJ. So when I do get it out on the street I'm not guessing I'm refining. There is a big difference.

Have you ever tuned on a DD? If you haven't then I don't really understand where you are coming from. I've tuned on a DJ so I know.

Audible Mayhem

iTrader: (48)

then why start a thread clearly bashing dynojets...

maybe its just the tuner, i dont have an issue tuning on one...


WOT is where people care about how the car runs, if it doesnt make as much power at 43% throttle, then push it to 56% throttle, who cares??

as long as my car is in the front of yours , thats what matters...

DaveFunction2ND

iTrader: (8)

I think that is because Sam understands the limits of his dyno. He uses it more as a safe place to do high speed runs.

Street tuning is the be all end all. BUT on the street how do you know how close to the edge or how far away you are? Esspecially partial throttle. Without some type of device that allows me to get close to that edge with at least some simulation of the street I would never know. A dyno is only a tool and many tools are only as good as their operators. The DD just allows me to take more of the modifying factors out. Just liek in any scientific experiment. We are trying to eliminate the variable. A load based dyno does that.