Dyno Wars - Consider it started

[Rhino]

Continued from another thread (http://svr58.ehostpros.com/%7Eopela58/phpBB2-3/viewtopic.php?t=1763&start=0&postdays=0&postorder=asc&highlight=)


If you want to start one (a dyno war), open up a thread :)

I'd love to, but I don't know enough about them to make an educated debate, only what I've been told, which similar to Woman's Day, may have contained less than reliable information.

I'd like to see the operators of them start a thread and give me the fores and againsts.

I can only say, and this won't be the first time, that the dyno is a tool best used to measure performance increase (or decrease) as a result of modifications made to your car. With that in mind, I would rather use a hub mount, that is more consistent than a rolling road bacause it removes from the equation things such as tyre pressure, tyre slippage...

I'd rather that than make a change, stick it on a rolling road and find I'd gained 10kw when 5 of it is because my tires are flat (or colder) thus, reducing the circumference of the tyre... or conversely, that I'd actually gained 15kw but there was tyre slip and it was actually an increase of 20kw.

I believe the two different dynos have two different applications here:
1. Rolling road is better if you want closer to 'street performance'.
2. HUB is better if you want to accurately compare and track mods.

[BASSULA]

both have there merits but also if you have a dyno dynamics dyno that is in SHOOTOUT mode there should be no difference as all variables are locked. something I'm not sure that the hub dynos have.

this has been prooven here in WA when 1 car ther day before ran on 1 dyno in shootout mode and the next day on a totally diff 1 and the diff was only 2HP both being dyno dynamics in shootout mode, and to add to that the 2nd dyno was in a pressurised arena at that.

[ultim8DTM5]

I think people get worried when they want to quantify the power increase in proportion to how much it cost them, so they turn to dyno's to justify the increase in expense :screwy:

[Jass]

I know that if iam paying for a certain engine upgrade and iam paying x amount of dollars and iam expected to get x amount of power then ofcourse iam going to test it on a dyno. Iam not gonna hand someone a few hundred - grand worth of cash for nothing. :mrgreen:

[Anonymous]

I prefer Rolling Road.
Dynamic Test Systems(Melb.) have the Best System I've Seen and I know the Owners of the Company, So I am Biased.
Dynamic Test Systems have Air Temp. Sensors for Atmosphere Temp, Air Intake Temp, Can calulate where the Power loss in the Drive Train.
Its been Proven They make the most Accurate Dynos in the World, Yes even more Accurate than Bosch Dynos that are Twice the Price.
See http://www.dtsaust.com.au/technical.htm
That will lay some Arguements to Rest.
And http://www.dtsaust.com.au
For the Full Site. Glady made here in Melbourne and Used by all NHRA Drag Teams.

[Anonymous]

both have there merits but also if you have a dyno dynamics dyno that is in SHOOTOUT mode there should be no difference as all variables are locked. something I'm not sure that the hub dynos have.

this has been prooven here in WA when 1 car ther day before ran on 1 dyno in shootout mode and the next day on a totally diff 1 and the diff was only 2HP both being dyno dynamics in shootout mode, and to add to that the 2nd dyno was in a pressurised arena at that.

SHOOTOUT Mode still had different settings and can be adjusted accordingly.

A HUB DYno is only measuring ( or lack of ) power up until the hubs of the car, anything after that ( Wheels ) is not calculated in the equasion and is going to give you a higher hP reading.

Remember, power is lose through the the drivtrain aswell as the oils that lubricate them. The DYNO hub is not taking into the rotating mass of the wheels of the car, hence the reason why you achieve 20kw higher ATW then most other Astra-T's.

I went to a Dyno day ( Proton GTi ) where we actually proved that by changing the 17" ( Aftermarket ) wheels to 14" Wheels that we achieved an extra 12kw ATW.

Like Rhino has stated, a Dyno is only good for 2 things.

1/ Tuning
2/ Giving people Egos about how much power they have :) :) :)

I actually posted a large post that I found on the internet in a new thread under the Astra Turbo section. I will see if I can find it and post it again.

[Anonymous]

Guys, Keep this civil

This was taken off http://www.sdsefi.com/techdyno.htm

You can either believe it or not. I just spoke to gman ( some of you guys know him ) and he agreed with what I was saying in the other thread. he is also going to post a study that a friend of ours performed. I would rather no one replied to this thread with negativity or doubts like the other thread unless you have HARD evidence to back up what you are saying.

Dyno Thoughts and HP Losses

After reading various articles in numerous publications on dynos and horsepower, I feel I should put forth a few observations:

Chassis dynos are great tuning aids but they only give a approximation of power output as some of the important variables are not accurately controlled. Certain magazines seem to think that results obtained from chassis dynos are the gospel. They are not. In one recent independent test, hp figures varied by 11% simply by doing the runs in different gears and in another test, results varied by almost 4 % by doing the runs with a different wheel/tire combination. Tire alignment has been shown to affect results up to 3% as well. Note that Engine hp DID NOT change here yet the dyno recorded an increase in hp at the wheels. A change in wheels/tires also does not affect true, wheel hp either, only the rate of change on the rollers and the vehicle acceleration on the road. One can only conclude that inaccurate moments of inertia and correction factors are being used.

On intercooled, turbo cars, there is usually insufficient airflow to ensure accurate results due to charge temperature variation which can be substantial. Even coolant temperatures may not stay down during the run which can affect power outputs considerably. The rate of acceleration is also important on turbo cars to be sure that the boost is not lagging the engine rpm. With RPM climbing too quickly, the boost has not reached a peak value so the hp figure is again inaccurate. Turbo cars should therefore be tested in top gear.

Without proper temperature stability and accurate moments of inertia on the rotating components, there CANNOT be accurate results as the scientific method is no longer being applied.

When all things are kept the same between runs and you get a tangible gain, it is a gain at least. How much, is open for discussion. It is important to note that as the oil temperatures in the engine, transmission and differential increase, friction usually decreases. This manifests itself as an increase in power at the rollers on each subsequent test. This factor should be accounted for when doing back to back runs. It may look like you are gaining some power on each run by making other changes when in fact this is due to reduced oil viscosity. When using a chassis dyno, always use the same gear and tires and wheels and start the runs from the same speed or RPM. Re-baseline periodically to see what temperature increases have done to power output.

Chassis dynos are quick and easy to hook up but have many of the above failings. They do not possess the accuracy of a properly calibrated engine dyno which has a more carefully controlled environment and condition set. Obviously, most non-professionals don't want to be yanking engines to use an engine dyno so chassis dynos do have their place.

Flywheel vs. Wheel HP

As most people know, there are power losses through the drivetrain so wheel hp is always lower than flywheel hp. Front wheel drive cars with transverse engines tend to be more efficient than most rear drive configurations due to the layout of components. However most publications overestimate these losses considerably.

Most rear drive cars have a 1 to 1, 4th gear which means that the power path goes directly through the mainshaft of the transmission. The only losses here are bearing drag which is less than 0.5% and the viscous drag of the gears running through the oil which is about 1% with hot oil. Indeed, published data indicates a transmission efficiency of 98 to 98.5% for conventional transmissions in 4th gear.

Losses within the driveshaft account for about 0.5% if they are properly aligned, balanced and with fresh U-joints.

Differential losses in the commonly used Hypoid type gearset is in the order of 6 to 10%.

The worst scenario case for a rear drive setup is on the order of 12.5% in 4th gear, not the 20 -25% often published. If 25% was being lost in the drivetrain, the oil would boil in the differential housing in short order and aluminum transmission cases would fatigue and break from the temperatures generated. On a 200 hp engine, something on the order of 37,000 watts would have to be dissipated out of the transmission and differential housings. Obviously, this is not the case.

Transverse, front drive transaxles usually have no direct lockup gears and no 1 to 1 ratio, however, since the torque path is never turned 90 degrees as in the rear drive setup and efficient helical gears are usually employed for the final drive set, losses are more on the order of 6 to 9 percent in the upper ratios.

Tire pressure and wheel alignment can have very significant effects on losses at the rollers. Tire pressures should be set the same between each test. Tire rolling resistance varies inversely with speed, another factor not taken into account by most chassis dynos when applying phantom flywheel hp formulas.

Comparing the Numbers

Many novices are quick to compare hp numbers between chassis and engine dynos and come up with all sorts of wild conclusions about drivetrain losses. These comparisons are essentially meaningless. Inertial dynos are based on the sound scientific priciple of accelerating a certain mass with a known moment(distance) over a given time. The rate of acceleration of that mass and moment is a result of the force applied (torque). If the RPM is known, HP can be calculated. On an inertial chassis dyno, it is virtually impossible to calculate the the moment of inertia of every tire, wheel, gear, joint , axle and shaft in the power train between the crankshaft and roller, therefore its results cannot offer an accurate HP figure. Even with coastdown drag measurements, these cannot be accurately calculated as different factors are affected in different ways. Some are proportional, some are inverse squared functions etc. Inertial engine dynos offer a very accurate figure if properly calibrated as only the flywheel's moment of inertia needs to be calculated and added to that of the billet. Water brake or eddy current dynos generally measure force (torque) directly through a ram or strain gauge so moments of inertia are not important on these in fully loaded tests.

Concluding that there was a 25% drivetrain loss by comparing HP achieved on an inertial chassis dyno and that obtained on an engine dyno is fundamentally flawed in that the chassis dyno numbers are highly suspect in the first place.

Other things to watch are correction factors applied for altitude, barometric pressure and temperature. These factors are NOT the same for atmo and turbo engines. Using atmo factors inflates the true, corrected HP figures on a turbo engine. In fact, look at the correction factor applied on your dyno sheets and see if they make sense. Many shady dyno operators simply enter a phantom correction factor to make the customer happy. This is a case where the dyno sheet DOES lie. Chassis dynos are essentially for tuning purposes, they are not well suited to giving an accurate hp figure.

Be aware that SAE correction factors do not apply to turbocharged engines! If your dyno sheet lists SAE corrected HP, ignore it as it is incorrect. You are better off getting an idea of where you stand by looking at observed hp with a turbo engine.


One of my friends recently received a well known commercially available chassis dyno with both inertial and eddy current loading capability. When a different vehicle weight is entered in the software for a pull, the computer spits out a dyno sheet with vastly different hp figures. This is complete BS and shows that the software package is just plain wrong. HP did NOT change on the pull simply because a different weight was plugged into the computer. Take all these figures with a grain of salt. I had an engineer from this company E-mail me and tell me their dynos were accurate. I told him I'd be happy to look at his data and asked him to send me his information to support this claim. I never heard back. Changing the weight DOES NOT change the hp the engine puts out PERIOD!

Another SDS customer had his drag car chassis dynoed. It showed a max hp of 280 yet when the car weight, ET and trap speed were plugged in, these showed that around 500hp was required to achieve these results. The dyno figure was so far off, it was essentially useless.

Looking at the jagged, sawtooth "curve" that most chassis dynos produce is amusing. The torque and hp curves really don't look like this. This is a result of poor software or mechanical measurement in the first place. Torque does not go up down, up down 2-4 ft./lbs. over 50-100 rpm as any real engine dyno will prove. Chassis dynos are essentially tuning aids, not true hp measurement devices. Use them to dial in your EMS mapping, not to brag to your friend's that you made XXX hp. When he blows you away at the stoplight, you'll just look, just, well, uninformed.

[Anonymous]

Very Good Find AlterAC :D
Alot of the Important Factors ya Brought up were in the Link i Posted Above.
I whole hearted agree, Chassis Dyno are a Tuning Guide only and For and I'll say it Wankers that wanna Show how much power they think they have. I've been too many Dyno Shootouts,Test, Etc. And People take what comes up on the Screen or Printout as Gospel. But like in the Above Post. Simple Factors make dire Power decreases, Examples:(Already Quoted) Thick and Cold Diff,Tranaxle,Trans. Oils.
Spark Plugs, Under Inflated Tyres, Oil Seal in Drive Line, Under Lubed Drive Shafts, The List can go all Day. Any of the Pre Mentioned can give In accurate Readings and Shark Tooth Dyno Charts.
This Dyno War will go for ever, But the Dynamic Test System is the Best I've Seen.
I aint going to Bag anyone or Anything here, Coz It has turned into Companies complaining. But MOST Chassis and Hub are In Accurate, And in my Opinion Hub Dyno are :screwy: A Few Years ago at the Easternats(Melb.) the Dyno Shootout they Used a Hub Dyno and it started the Biggest War in Forums, Magazines. Because it was inaccurate and Worse when People don't follow the rules of the Competition by taking out Rear Brake Pads.
But again I hear people sook at Auto Salon, Summernats, Etc that the Dyno Operator strapped there car down to hard and that Effected there Run. Get Over it, Petrol can Be Crap or ya Engine can had a Dicky Plug or Lead.
So no system will ever be 100% Gospel.

[Anonymous]

P.S. Everyone has there own Opinion about everything and They know better, Me Included :lol: But it is interesting to see/Read other Peoples Views.

[astra_city]

Interesting readings!
I'm not going to begin to pretend knowing all about the itty bitty bits of how a dyno measures the power etc etc...however I have and always will believed that dyno's are good for pretty much one thing:

Measuring a power gain before and after you do a modification...so you have a pretty good idea if the mod worked/didn't work and if it did, how much power ATW you gained.

I don't think that you should begin speculating about how this compares to flywheel power, how your car compares to another car on another dyno or the same for that matter - it is purely a tool for tuning your car to the mods performed and gaining an idea of how effective each mod/mods you do to your car has been.

[BASSULA]

Alter AC nice find.....

but the inital post wasnt bout flywheel horse power that engine manufactures use in true scientific conditions to get the best out of the engine they are trying to sell... but as a question for the "normal" ppl to see what sort of power there cars actually have...

now not saying you are wrong... more than likely very right... but for the normal ppl what would you go by for an ATW measurement??? HUB OR CHASSIS

I prefer chassis with a shootout mode with supposedly should be the same anywhere int he world so I can take my car from here perth with 200BHP ATW to QLD and do the same thing... that to me is a good dyno system for the consumer!

cheers

[Anonymous]

ATW the wheel figure should be taken from a Chasis Dyno.

Your not taking a At the Hub figure are you :) :) :) :)

Me, I would prefer to line the 2 cars up and go at it :) :) :) Fvck this dyno bullshit :)

[Rhino]

My brain is melting. Much information.

Furthermore, you CANNOT measure drivetrain loss as a percentage because power loss is not linear.

Example, if stock hp for car is 200hp at the FW, we dyno it and get 140 at the wheels. One might say, my car has a 30% drivetrain powerloss. But put 500hp through your car (flywheel), and the drivetrain is not going to absorbe 150hp. It is more likely to remain very similar to the original 60hp.

Don't get me wrong my fellow Opel Ausians - I don't back myself that I have the highest power car or anything remotely close to it. And as I mentioned to Wayne who is coming to Perth, dynos are so unreliable that he may notice absolutely no difference between my car on the road and an AMD mapped car on the road.

Like I've said before - I can overtake when I want to... and do :D

[Jass]

Weve had cars with 10kw diference (supposidly on the dyno) side by side and nail them on the quarter, both cars seem to run exaclty the same (also driver ability comes into the question bu this aside), as explained above the main reason to have a car on the dyno is to check how well the car is running.

Check to see if the car is pinging, maybe cases of blow, ect ect
This are what really worries me, iam not after 10 or 15kw more or less between astras T atm, iam more concerned that my car is running at 100% and that no engine damage of tear and wear will continue from settings not tuned correctly.

I know that if i line up my car againts either a WRX or GTI 180 pug, integra or another astra T, that my car will quite confortably keep up or do better, with 10 or 15kw more or less.

At the end of the day the power output that you use on every day road or track driving can come down to driver, temp and also the high light the car is.

Dyno tunes for kw in my mind is pointless, dyno tuning for optimal engine performance for your car is the way to go!

[Rhino]

I come back to this pinging issue.

My tuner says you cannot know if a car is pinging by looking at a dyno chart.

You need an osciloscope (and maybe spelling lessons?). True?

It is his opinion the saw tooth graphs are misleading because it depends on how your tuner has set the 'zoom' level of the graph. Sharp rises and falls don't indicate pinging.

Comments

[Anonymous]

My brain is melting. Much information.

Furthermore, you CANNOT measure drivetrain loss as a percentage because power loss is not linear.

Example, if stock hp for car is 200hp at the FW, we dyno it and get 140 at the wheels. One might say, my car has a 30% drivetrain powerloss. But put 500hp through your car (flywheel), and the drivetrain is not going to absorbe 150hp. It is more likely to remain very similar to the original 60hp.

Don't get me wrong my fellow Opel Ausians - I don't back myself that I have the highest power car or anything remotely close to it. And as I mentioned to Wayne who is coming to Perth, dynos are so unreliable that he may notice absolutely no difference between my car on the road and an AMD mapped car on the road.

Like I've said before - I can overtake when I want to... and do :D

EXACLT!!!!

Do a search for my posts on here and you will see probably the largest and biggest argument on this forums History :)

[Jass]

I come back to this pinging issue.

My tuner says you cannot know if a car is pinging by looking at a dyno chart.

You need an osciloscope (and maybe spelling lessons?). True?

It is his opinion the saw tooth graphs are misleading because it depends on how your tuner has set the 'zoom' level of the graph. Sharp rises and falls don't indicate pinging.

Comments

It is harder to see if the car is pinging on the dyno read out, but remember that tuners can set the dyno up to give all sorts of readings, including air fuel ratios.

If you lift your bonet while the car is on the dyno and u hear a sound like a ratteling spray can then your car is pignging.

Or so ive been told. ive had my car on two diferent dynos and both tuners have said my car is pinging atm. I could also hear the ratteling while on high boost

[Rhino]

OK, was thinking about this this morning.

I have two conflicting scenarios... which I could probably think about a bit more and extrapolate an answer but...

On a rolling road, won't reading the wheels produce a higher figure - similar to a merry-go-round, ie, outer spins faster than the inner?

And the conflicting argument...

You get quicker times down the 1/4 with smaller wheels...

:(

[Chux]

ah yes, but do you get faster times down the 1/4 with smaller wheels because the car can actually move faster with smaller wheels (kind of like changing the diff ratio)

or is it because you can fit bigger tyres on smaller wheels which gives you more flex in the tyres off the line and therefore more grip?

I'm going to run my car with my 205/55/16s on wednesday instead of the 225/40/18s

so i'll let you know how the 60 foot times go :P

[Rhino]

I'm going down on Sunday if it doesn't rain. Running my stock 17s though. Gonna let them down to 20, maybe 15 psi and see if I can't keep some grip on our track and improve my time.

[Jass]

ah yes, but do you get faster times down the 1/4 with smaller wheels because the car can actually move faster with smaller wheels (kind of like changing the diff ratio)

or is it because you can fit bigger tyres on smaller wheels which gives you more flex in the tyres off the line and therefore more grip?

I'm going to run my car with my 205/55/16s on wednesday instead of the 225/40/18s

so i'll let you know how the 60 foot times go :P

Remember thought with more power and smallers wheels its harder to get the power down to the ground. Try sticking 16's in your car and see if you can take of the line the same way that you do with your 17's.

Specially on a front wheel drive car and no LSD wheel sping city hahaha :P

[OPL-20T]

the less air u have thebeter of the mark BUT at high speed the slower they will roll as with more air u roll faster rite... so go for an uinbetween dude.

[Anonymous]

That arugment comes down to rotating mass!