Steady State Dyno vs. DynoJet just some FYI

[steve shadows]

Steve's Homepage - Different dyno types

This is another good link I wanted to share with everyone regarding the differences in output you get as well as the ability to tune.

Again most shops that have been popularized by media and the common car culture use a dynojet. In Japan's most serious tuning shops, BMW north america as well as almost all australian shops a Steady State Capable dyno is used.

I am trying to educate people to this so that the head breaking and psychological effect of having a car tuned on a better dyno but recieving a "lower" number can be calmed.

The fact is a dynojet does not account for

1. Weight of the wheels or driveline
2. The actual load and drag (that increases as you accelerate in real life) on an inertial dyno the amount of drag that the engine has to fight against actually decreases
3. The moment of torque (a steady state dyno makes an explosive load up into torque much harder or impossible giving a more accurate number in the real world application of the output to the ground).
4. The lack of a true torque measurement - HP is Toruqe over RPM or TIME = a representation of work.
5. Dyna-Packs are will frequently read even lower than DynoJets as well - unsprung weight or the weight of the wheels, and rotating assembly actually make a huge difference in real output- more than most could possibly imagine

The advantage of the Inertia style dyno comes down to making customers happy and the reliability of comparing any given dyno number to any other dyno readout on the same type of dyno easier- because the given weight of the drum being used to test the acceleration rate is commonly the same as long as the intertia dyno is made by the same manufacturer.

This is why high end tuning shops often have a dyno dynamics to tune the car in every cell and to achieve the best tune and the Dyno Jet to print the best possible graph to show linear outputs under WOT so it can be easily compared to other cars from other shops that frequently have dynos from dyn-days- not from highly technical shops doing a full EMS overrun

I got these from the shop that is about to dyno my M Coupe. It is consistent with what I have been told elsewhere but certainly an interesting read:

20) My car makes 300 hp but your dyno says it makes 215. What is up? Our dyno is the most accurate measurement of torque at the wheels. More accurate than most. No "interpolation" or "estimation" or "inertia factors" are applied like they are on other competitors' lesser machines. What this means is that this is the actual torque being applied at the tire. Typically, a 300hp all wheel drive car will measure in around 210-215 on our dyno. This is normal.

21) I went to a Mustang dyno and they said theirs reads low, but you say yours reads low. Is this just some trick used by tuners? The Dyno Dynamics is known throughout the industry as being the "heartbreaker" dyno - because it breaks the heart of every man that thinks he has 500 hp when he really has 350. The Dyno Dynamics reads lower than the Mustang. It reads WAY lower than a Dynojet. It reads WAY lower than a Dynapack (which actually reads too high on tip-in). The closest in numbers (at low HP) is the mustang, but using the above example, the same 300hp car was dyno'd back to back on a Dyno Dynamics 450 LowBoy (what we have) and a Mustang AWD500E (what some other guys have), and that 300hp rated car consistently read 223 on the Dyno Dynam ics and 249 on the Mustang. One hour apart, exact same car, same town, same altitude, etc.

22) Why dont you just make your numbers look high to be the same as some others? Dyno correction is not a fixed amount. In other words, adding 30% at xx RPM and xx power does not translate. i.e. Using the above example, a car that makes 225 is about 1.3 to get 300. A 900hp car on this dyno is NOT making 1200hp ! Dyno numbers should be used for relative back to back comparison, and nothing else.

23) How do I compare my dyno results to others with similar setups? For Subaru owners, there are enough internet resources to compare, but essentially, Dyno Dynamics and Dynapack are the only 'consistent' numbers, and Dynapack reads very high, Dyno Dynamics very low. We can help you seek out other similar results. A great resource listing a slew of Dyno Dynamics HP baselines is available in the Gallery section at the KTR Performance Dyno Gallery Web Site. It should be noted that KTR uses atmospheric correction, which we do not use on our dyno plots.

24) How do I compare my pulls to Mustang Dyno, or a Dynojet, or a Dynapack? Every dyno is different. If you want dynojet or mustang-ish #s you have to multiply by 1.18 or so, 1.25+ for DynaPack. But remember, this is just ballpark, as it is not linear.

[96Turbo]

good stuff....

[ATLspeed]

wow.....now im not sure where i wanna go to get mine dynoed to see what numbers im puttin down...hmmm

[DJ_Sunrise]

Steve, you're true gangster. Thank you for clearing the air. Dyno dynamics shouldn't be called a heart breaker, it should be called get the reality dyno.. but that just doesn't sound so cool.

-Bart

[Om1kron]

hey steve do you tune chrome for honda's just wondering. My little brother wants to tune his car, and I was telling him about you so I just wanted to check.

[sillyvia13]

A number shouldnt be put on it...
Get in it, if it RIPS better than it did. GOOD! lol...

I got into cars and jumped on a higher reading dyno...
what a mistake... the shop SUCKED! lets say I made better #'s but shit ran like a wide open ass.... shitty.

Tuning dyno's ftw. gimmie 154 hp. as long as I can spin tires til 4th(sliding) I am good.

[redpotatoes]

Mustang Dyno's, dynojets, dyno dynamics or dynapack, it doesn't really matter the # you produce. A dyno should be used to TUNE CARS and not to show off HP,TQ numbers.

I personnaly went on a dynapack cause my tuner is using one. The most important thing is to have a good tune after the runs. If you really want to see the difference, go out and dyno your car on all the dyno types and compare. Great way to waste money...

[steve shadows]

Exactly,

A Dyno is a tool used to tune, but frequently becomes a measurement of whether all your money and hard work was worth it.

The issue comes in when you pay for tuning - especially in the drifting and road racing community - where you need the map tuned everywhere- not just for WOT.

A dyna-pack can simulate some steady state conditions but will quickly overheat if you attempt to hold it in any particular cell as long as a dyno-dynamics.


If you really want to see the difference you just need to get an accurate measurement of trap speed in a given distance.

[Def]

Ugh, I hate this argument because there is so much misconception on the basic kinematics and relationship between power, force, and time that causes each "side" to like their own dyno.

My take on it - a steady state dyno is great for engine tuning to find small variations in engine VE and knock sensitivity, but it is *NOT* accurate for the conditions on which an engine will actually operate. An engine sweeping through an RPM range is not the same as one being held at a given condition at WOT/partial throttle/whatever.

An inertial dyno is arguably closer to real world conditions the engine will operate in as long as the dyno roller inertia times angular acceleration is relatively close to the combined aero load plus mass times linear acceleration of the vehicle would see in a real world 4th/5th gear pull.

[steve shadows]

We don't just hold the car in steady state the whole time.

We pull it up through sweeps under a given load - this load can be adjusted to simulate the most appropriate amount of drag on the drivetrain ,

We can simulate the way the engine will actually operate and much much more. We can simulate drag racing, full throttle pulls in any gear, and adjust load to match particular conditions that we would like to simulate. This is why rally shops love these things, you can simulate uphill, program corrections for BARO and do WOT pulls in every gear or bring WOT pull up to a certain point and hold for trouble spots in the map as well.

You can't adjust this with an inertia dyno, it's one size fits all - weight - the drum represents a given weight or load on the vehicle that the vehicle has to overcome - it's a measurement of the car overcoming the movement of a given weight- No adjustment can be made and the weight of the vehicle on the roller (the amount of mass or weight of the vehicle moving it) is also left out of the equation- at least the last time I used a dynojet straight roller dyno. It's actually audible - the surge on. When you roll into 4th gear in your turbo powered car when it has full traction with the road does it surge faster through the rpms? The dyno dynamics in WOT mode simulates the exact same conditions as accelerating

Dynojet numbers are often closer to MFG suggest brake/flywheel outputs than they are actual road power numbers

[Def]

I realize you can do RPM sweeps at varying rates with a steady state dyno, but that all affects apparent output. To get a "comparable" number you have to allow a set ramp rate etc.

I do agree a steady state dyno has its uses, but as far as accuracy, Dynojets seem much more realistic to actual on the road acceleration from the few analysis I've done out of curiosity. Pretty straightforward to get a function to roughly match a power curve, input a vehicle weight and do an approximation of aero drag/rolling resistance etc. and see how fast a car should accelerate with given gear ratios.

[steve shadows]

Originally Posted by Def

I realize you can do RPM sweeps at varying rates with a steady state dyno, but that all affects apparent output. To get a "comparable" number you have to allow a set ramp rate etc.

I do agree a steady state dyno has its uses, but as far as accuracy, Dynojets seem much more realistic to actual on the road acceleration from the few analysis I've done out of curiosity. Pretty straightforward to get a function to roughly match a power curve, input a vehicle weight and do an approximation of aero drag/rolling resistance etc. and see how fast a car should accelerate with given gear ratios.

Yes, but Def usually dynojet numbers are MUCH closer to Manufacturers Brake HP ratings which is extremely suspicious if you are using the dyno to read real Road Power.

Now if you are using it to simply check output on a sweep up in rpms, and you arent really concerned with exactly what torque at the wheels is being output it seems like a good tool.

I have had some pretty well known shops and tuners complain about "spots" on the map where no matter what they did with their dynojet they could not access the cells to tune them out so the car would be totally smooth in accelerating through certain rough regions.

This is when they asked to use the DD. This is especially apparent when tuning cars that do drifting or other uses where they see very sporadic and fast load transitions on the engine. There will always be some spots that the car will see on the track or road that the dynojet will just not be able to access.

[g6civcx]

I use Dynapack exclusively to tune the secondary air metering on my carb. I don't care about peak numbers; I'm only tuning out the flat spots in the torque curve.

Do you see any problems with this?