Why Your Dyno Figures Might Be Wrong and Your Horsepower Comparison is Invalid!

[@magnetic0314]

I like that you touched on the idea of calculating BHP. Cracks me up how guys in the UK are always quoting BHP

[@ChristopherHallett]

BHP literally means brake horse power, or power measured on a brake (dynamometer).

[@magnetic0314]

@@ChristopherHallett yes, as measured from the engine

[@H05TYL]

@@ChristopherHallett "Measured" not measured then fudged to get an approximation of what it would be if it was measured differently. Calling an estimated crank reading "BHP" is disingenuous.

[@ChristopherHallett]

​@@magnetic0314 All dynamometers are brakes, whether chassis, hub, or engine. Hence, power measured by a dynamometer is brake power, whether that be horsepower or kilowatts. So the correct terminology for say a Porsche 911 that measured 300 kilowatts on a hub dyno is "300 brake kilowatts at the hubs".

[@ChristopherHallett]

@@H05TYL All dynamometers are brakes, whether chassis, hub, or engine. Hence, power measured by a dynamometer is brake power, whether that be horsepower or kilowatts. So the correct terminology for say a Porsche 911 that measured 300 kilowatts on a hub dyno is "300 brake kilowatts at the hubs".

[@PHATT_TV]

Omg I’ve been dying for someone knowledgeable to break this down for everyone…..Thanks Andrew/Motive!💪🏽

[@vlt873]

I know it's only really 1/4 mile focussed but would be interesting to learn more about how different torque converters affect readings and the way the car drives.

[@TGLAZEY99]

As well as gearbox, driveshaft, axle set up etc. You will always have a percentage loss from any drivetrain set up in any car. As well as temperature of car and air, air quality, humidity, mouisture, temp of gearbox and engine. Theres about 50 different variables to power levels on a dyno run.

[@2rismo]

@@TGLAZEY99 "You will always have a percentage loss from any drivetrain set up in any car." - this is incorrect and addressed in the video. Arbitrary drivetrain percentage losses aren't a thing.

[@TGLAZEY99]

@@2rismo i dont think so really. But it all depends on how a car is tuned. Different tuners can say and do whatever they like to a cars ecu and that could be all the car makes on the day. A real proper tuner just does a good job and makes the car run properly and produce a better horsepower and torque figure. My mates ls1 v8 holden calais made 352hp and 1058nm of torque last year. But did 390hp and 600nm of torque couple weeks ago. Both on a chassis style dyno.

[@2rismo]

@@TGLAZEY99 It's not me disagreeing with you about arbitrary drivetrain percentage loss. It's the fundamental laws of nature. You're picking a fight with Isaac Newton.

[@MotiveVideo]

The entire point of the video is to get people to stop saying "percentage loss" and start saying "loss"

[@davecozzie1]

Without a doubt the most comprehensive modified car tuning channel on KZbin

[@mrn0b0t]

Hello Andrew, the best thing you said in this video was "it is a tool to compare" so its important to measure before and after the tuning to see the gains. Your video is great to understand basics but its not complete. Please let me help you a bit. 1. PS stands for "Pferdestärke" ( Horsepower ) , but in mathmatics we calculate in KW ( Kilowatt ) 2. you miss a very important thing : the Rollers, there are Single rollers and 2 ( or more ? ) per axle. a single roller has way less slip then a dual roller design. 3. We in Europe , in my case germany, measure wheel horsepower and add the parasites to get crank horsepower, so we do not guess and put a weird factor in it , we measure it ;) 4. Eddy Current BRAKE

[@HashDogg06]

Well i gained no more info from your write up over watching Andrew's video.

[@mrn0b0t]

@@HashDogg06 thats a pity

[@briansrensen4068]

Yes, he did not mention the method of measuring the parasites losses, when you let the car coast down after the run and then add it to WHP numbers, to get to the crank horsepower numbers. That's how must dyno's in Europe measures and that way you have take strapping metodes, tire size, pressure and other things out of the equation and get nice and repeatable numbers.

[@shadowprice8100]

Finally! This is shall be the video I reference when people start talking crap about power numbers.

[@frozenpete788]

We had 3 chassis dyno in our group (famous swedish heavy truck manufacturer) and never compared one dyno to another. On our site we had a truck, with a known engine that was tested in engine test cell, known power, torque, fuel consumption etc (all the important parameters) and we used that very same truck every month as a quick check to see if we could repeat numbers. It's not a calibration because you need something more accurate to check (works for everything). Truck was installed the most repeatedly way as possible every time, chains and tension the same way but that thing moves so much even with sensors.. Can't tell the difference. Cell temp regulated to 25C all year. Warm-up the same way, rear axle and gearbox temp monitered. Engine fan speed monitered too, and most importantly, engine ecu connected to the control room so we could do everything the same way all the time and not let the truck switch between modes (yeah even full throttle). We had a fuel flow meter with regulated fuel temp too etc. The most interesting yet difficult years of my carrer because this is maybe 5% of things we checked during our tests. And we broke things too ahahah. It's still a very quick process to see if your engine or else has issue, test new strategies, and do a before after the same day if you could. We didn't play with 4 digits gtr's, but seeing a 750hp truck with 4 digits of torque twisting the frame and shredding rear tires on the rollers, which BTW were 2.5m in diameter and were 9 metric tons with the rotor of the generator each. Heavy stuff

[@lukezivkovic8731]

This is the best video I’ve seen on KZbin all week.

[@MotiveVideo]

Thanks!

[@freakyRunner]

In Germany we let the dyno also messure the drivertrain when decaleratin in neutral. So that we get the crank HP. And the PS is here from Germany the Japanese just use it also , Pferdestärke is the complete word and it means Horsepower. 1 PS is when a Horse lifts 75kg 1m high in 1second Greetings from Germany 🇩🇪

[@Levent_Ergun]

Drivetrain losses are also great to know.

[@tsdyno]

exactly, engine hp on modern dynos arent "guessed", its measured because the software knows how fast/slow the roller will decelerate whitout load and then it decelerates faster or slower with the car on it... I would also argue that the wheel hp is the most inaccurate because of the reasons also said in this video, strapping, tire rpessure, etc. But when you measure the losses and display crank hp its more accurate/repeatable. Obviously hub dyno is still the most accurate if not using a engine dyno.

[@tunkka]

​@@tsdyno Weight and diameter of the roller and therefore intertia is constant and don't change during multiple runs therefore with simple math you can calculate power... on the other hand there are eddy losses by heating of eddy based hub dynos and there is actually no steady point measurement thru RPM range during dyno pull on HUBs. So getting curve from eddy hubs is at the end calculation from load cell + corrections averaging the spikes as eddy is PID controlled. Take in to consideration bigger roller with large diameter and inertia have great prone against changing wheel size especially if drivetan decaleration is taken in to factor.... but if you combine large diameter roller with capable eddy brake than you have proper tool for working with WOT pulls as for steady state tuning and measuring.

[@sergeyakinin997]

@@tsdyno That's also effected by engine compression, internal friction and weight of rotating assemblies... it's not really a 100% fool-proof way of getting drivetrain losses. Anyway it's completely pointless to guess (no matter how educated the guess) engine HP numbers when change in WHP of your actual setup is what matters anyway.

[@tsdyno]

@@sergeyakinin997 nothing after the transmission input shaft affects the drive train loss measurement, its done while coasting in neutral after the dyno run. only resistance from gearbox, diff tires etc and all the rotating mass/inertia of those drivetrain parts and wheels+tires are measured ass losses.

[@boostedmedia]

Excellent video Andrew! Really clearly explained with no fluff. Thanks :)

[@bollinsracing74]

This is the best explanation of dyno tuning I have seen, well done.

[@Tom-lf8hx]

These videos are the best!! Ive always wonderd how they all work and it done in a way you can understan without needing a PHD

[@KuyaPow626]

This is the best explanation I've seen, wow! I learned SO MUCH and feel absolutely confident I could explain it to any friends of mine who ask about dyno numbers. Thanks! This was really a pleasure to watch

[@yudaresigama4209]

I have been wanting to make a youtube video explaining about this in my country's language, but you nailed it man! Love it!!

[@shamil808]

Knowledge = Power Loving Motive Tech. Thank you for making us better petrolheads. 👌

[@masudrahman1750]

this channel is very underrated

[@konholio2]

This channel is gold ! Each one of these videos is priceless.

[@StavTech]

Dyno numbers no matter what is BS, who cares. Performance figures is all that matters. If you don't want grip to affect it, look at KMH/MPH. 1/4mile, half mile, whatever, those don't lie and grip levels have next to zero effect unless you spinning for literally the whole length.

[@wobblysauce]

Classic butt dyno, you don't need to make big power to go fast.

[@manitoublack]

As always Andrew, great video telling it how it is. One thing thing that I've noted with turbo engines, is the low/midrange number can be affected a reasonable amount by how much heat is in the exhaust system. If that exhaust manifold is glowing red, then things tend to light off a little sooner.

[@MotiveVideo]

Thanks! Yeah, agreed. There is so much more depth we could go to in the video. We had to draw the line somewhere. We worked out we could do 10 hours plus video if we let me go down every rabbit hole.

[@antonjimmy5636]

Richard Holdener has a great video about engine vs chassis dynos. He compared an auto Dodge van and a manual LS Silvia, but ran both cars "stock" and then modified on both chassis and engine dynos. The hp loss through each transmission was pretty much the same for the "stock" and modified power levels

[@RyanOlsen042]

RPM goes down with a decrease in wheel diameter, but torque goes up as wheel diameter decreases. Both are a linear relationship so I would guess the two cancel each other out. I would argue that the deflection in the tyre as it hits the dyno roller and then leaves it requires energy and creates heat in the tyre, thus decreasing the recorded power.

[@matthewoneil8136]

I'm glad someone else picked up on this!

[@RossHollandAU]

Thanks for this!!! Its hard to explain this sorta thing to some people without them getting pretty defensive 🤣

[@ktmr8]

Great informative tech video thanks. However I’d like to add that a faster ramp rate is useful in finding a base line for AFR or a problem with fuel system capacity or function as well as a host of other issues that could be potentially harmful to an engine. By reducing the time the engine is loaded in a less than desirable tune condition can mean the difference between being able to rectify the problem or having to rebuild a damaged engine!… so as part of the dyno tuning tool kit, ramp rate is extremely useful… But once the base tune has been found or any potential setup problems are rectified, then I’m in absolute agreement that the load on the engine during a dyno run needs to replicate the load the engine will see during its intended usage and so a ramp rate a little slower than the slowest the engine would see in use is what I use during tuning to make sure the tune is safe for a long and reliable operational life.

[@omypest]

Good video Andrew good points covered I am lucky enough to have engines on engine dyno then put in car and tune chassis Iknow you can not use % but from what I have seen 600-620hp. Would relate to around 450-465hp on a dyno dynamics roller 700 engine 520 on chassis 810 engine 590 who so on we know a 400 hp stock ls hsv would have 300hp wheels so what I have observed is approx whp convert to kw at engine now this is based on auto with hi stall and built diff so big power loss on hubs say 990hp engine 799 hub. 1030hp engine 811hp hubs 1220hp engine 967hp hub 878hp engine 690 hub so I always say it’s almost close to say 30% on engine to chassis roller with exhaust and auto ect and around 20% for hub dyno not to be fact but as a guide so yeh many variables even driveline angles can influence it and yes obviously manuals would read higher as less loss 1 example here is dynoed a 355 made 456hp engine on roller dyno with stick t5 manual and small diff made 357hp at wheels where if it was auto it would be like 330ish hope some of that info helps and the standard correction used in the us with engine dyno reads around 6% higher than say our sae calc this is why many crate engines tested don’t measure up here. Anyhow great video sorry about long winded reply and yes if your gtr made that 700+ on dyno rollers it’s easily making around 1000 engine trust me

[@adamloader9534]

I’m always facilitating with these in depth technical explanation videos. Great content 😎

[@markj6049]

Great video... however, I disagree with two statements. At around the 6 minute mark you talked about that the reason strapping the car down harder will cause a lower reading was that the tire diameter decreases. If the diameter goes down, the moment arm will shorten, making the torque measured at the roller go up, while the speed (rpm) would be lower. In a loss free system, these two factors cancle each other out. The reason that strapping the car down harder causes reduction in the measured power is the hystresis of the rubber. It requires a lot of energy (and therefore power) to compress a tire. Imagine the tire rotating at just 20 revolutions per second. That tire has to compress and bounce back 20 times every second, and the more it must compress the more power it will et up. That is also one of the reason tires heat up, when driven (friction is of cause also a contributing factor). The second thing is that you said PS was Japanese... it might be widely used in Japan, but the unit is German, and is actually an abbreviation of the German word Pferdestärken, meaning Horsepower... But other than that great video, keep them comming

[@nickthelebo]

Allso drivetrain losses can be calculated same as inertia and friction losses in a hub dyno are calculated

[@aaronmahanga7635]

Thanks andrew for explaining the differences between dynos

[@auttomotiveelectronicperfo2010]

Good material! Our dyno is chassis, already had reading above 850 whp with no wheel spinning, our dyno is "drum" model, I do think more than 1000 whp could be an issue for reading without wheel spinning. Greetings from Brazil!

[@jimbostir5004]

Very informative. Thankyou Andrew. Now I’m pleased that mine was hub dyno’d here in the uk. Before this I thought “at the wheels” was the same as “at the hubs”.

[@datdom34]

Anther great one Andrew and the motive crew.

[@laistab1916]

Finally more videos putting this out there

[@cgaquikkie]

I'm really surprised that there aren't way more "u R rong" type comments. Ah well, it's only been a few days... Fantastic video, thanks for all the nuggets of knowledge Andrew!

[@blaznmax8877]

I think it's best to tune on chassis dyno cause close simulation to actually street driving with load extra weight in car ... want to impress people put it on a hub dyno

[@MotiveVideo]

We dont agree. We found hub dyno enabled much better fine tuning as runs are repeatable. Have a watch of our latest Yaris video

[@tjbugeye]

My tuner has a dyno dynamic chassis dyno. He did a video where he adjusted the wheel base of the dyno. Didn't touch the straps at all. And picked up 20hp. So it goes to show how numbers can be manipulated.

[@MrXr8260]

This is a great video explains everything you need to know..thanks for posting this

[@MafiaboysWorld]

Not just workshops and brands Hawko, but also countries. For example, everyone knows that 5000hp on dynos in the USA is the same as 500hp on dynos in Oz. 😛👍

[@MotiveVideo]

We do cover that in the video and very true. Yaris development has shown just how bad

[@MafiaboysWorld]

@@MotiveVideo Yeah, as I hit send, you started on the country differences of ps, Kw, etc., hence why I kept hp vs hp in my comment instead of going to Kw. 😂 I'll shut up now and wait for the inevitable talk about the "shootout" mode on dynos. 😉👍

[@TGLAZEY99]

@@MotiveVideo as well as tire pressure engine temp/ pressure. gearbox temp gearbox/ driveshaft set ups. You will always have a percentage of loss/ gain of torque and power from the drivetrain on any dynos you run any car on. Just true mechanical facts.

[@wrx2hot4u]

@@TGLAZEY99 dont forget running valve caps also affects alot, that 1 gram makes a big difference.

[@TheConburger]

A lot of good tips and basically in principle indicates the differences in dynos. There are a few things I think you should put more research on.... For starters, depending on the tuner's skill level, a good tuner does not tune for power only (mostly loading dyno) but for road conditions. The car must believe it's on the road (as close as possible) Your car will make less power in 1st gear than in top gear. Why ? Because of the inherent more power drawn by accelerating engine and wheel components, turbo lag, engine transients, etc in lower gear. Tuning a car in each gear, at road conditions is some of the final touches a good tuner will do. Decent ECU's have tuning maps for each gear. We've built more than 500, chassis, engine, hub dyno from 2Hp to 8000Hp, so being a fan of all these types of dyno's (loading and inertia) it is vital to realize that each one has its place and application. A good inertia dyno will have roller weights equal to vehicle weight. A better dyno will have load added to compensate for wind resistance. Rolling losses (wheel drag) is not a fixed number or a constant. Rather a quadratic increase as speed increases. Normally inertia dynamometers can measure the losses when the vehicle is in neutral and these losses can be measured. SAE gives very good predictable powertrain losses. If an inertia dyno (compensating to engine power) reads high, verify it's accuracy on an engine dyno, or at least use a brand that has verified it this way. A dyno is the same measuring tool as a scale, it needs to be accurate. Weather it measures in pound, kg or ounces, there is a correlation. If the power is different, it is not accurate, unless the manufacturer can explain what he measures and what he is compensating for, or how. But yes, the reality is that they do read differently and ultimately it is a (has to be) a relative measuring tool. Any tool can be misused, it all depends on how honest the user is and how much you can trust your tuner. The proof is in the pudding and the pudding is the road. Simulating these conditions as close as possible is what a dyno is about. You cant BS the road.

[@m.j4037]

Doubt there's anything on the net that comes close to this tech talk.

[@Armaniche]

I think people just get the purpose of the dyno wrong. It is a tool that is used for tuning a car and it should not be used for hunting of peak numbers. They can be altered as you showed. Repeatability is what is desired. That is the only way to know if the changes you've made have actually made a difference. Even the same car on the same dyno on a different day will read differently. It is all about consistency throughout the session. Steady state hub dynos are really the only way to tune in my opinion. The thing that saddens me is that bench racers only really care about peak numbers. It's like comparing dicks for them. And for an actual car peak numbers only tell 1/3 of the story. Sorry for the rant. I've grown to hate dyno queens and bench racers for multiple reasons but really dyno stuff it one of the topics that triggers me the most. And I'll not even dive into the incompetence of some dyno operators... the amount of misinformation and bro science that is floating around is frightening

[@tunkka]

Don't forget eddy brakes bolted on the car axle also cause drag and other parasitic losses as there eddy brake inside of the dyno hub box is usually air cooled (basically fan) which cause quite a lot of not controlled drag for cooling especially on high rpm plus with more eddy brakes bolted trough axles in row on a hub instead of tyre touching big diameter roller (big diameter roller are preventing smal patch contact and therefore tyre losses) there a lot of added inertia is an factor.

[@GarageSupra]

New drinking game, take a swig every time he says basically 😂🍻

[@2fast2nick]

I blacked out, what happened?

[@rubberbandman2540]

what a legend mate thanks for the information

[@TheGinger1]

We have a similar problem in cycling. It doesn't matter if the number is 3 or 3 million as long as when you do two runs with the same combination of parts and conditions that it says 3 or 3 million. The reason to measure power is to then make changes and see if those changes have increased the power. The problem comes when people want to brag about their power numbers without actually racing eachother.

[@doctor_who1]

the best video on the internet

[@finnroen2334]

We also look at injector size, fuel pressure, duty, BSFC, AFR, airflow BSAC and EGT that all should confirm the horsepower claim, not contradict the result.

[@GoNutsButch]

Subscribed, your awesome Andrew! Thanks fella!

[@JimShorts10]

It would be interesting to know about Torque Multiplication from a torque converter. This seems to not be covered much in places

[@hyper8545]

Thanks for the video motive. Always down to learn this type of knowledge ^^

[@bigcountry5520]

dyno's are really only useful for relative comparison, not determining road performance values.

[@bradleyfryer5563]

Great video explains a lot of questions I have had about dyno figures. I have always thought quarter mile times a better basis for comparison

[@2fast2nick]

Great video, you explained so much… Yeah ridiculous shit I have heard.. People get their WHP from the dyno, then they just add the 15-20% drivetrain loss in their head so they can go around quoting a high number.

[@matthewoneil8136]

My personal favourite is when people quote their "roller" torque figure as if it is indicative of engine torque. Sure mate, your cammed LS1 is making 950nm of torque :D

[@lockjawjak]

Brilliant stuff, between you, D4A and Andre from HPA I have all the tech talk videos I could ever want!

[@Freechinesefood561]

Can you please do a comparison on air filter setups on big single turbo RB’s?

[@MotiveVideo]

If someone makes us a bunch to test, we will

[@ScubaSteveArkinstall]

Haha you were there the only time my Silvia’s ever been on a dyno, at parklands back it the day!

[@jasonwallis2594]

Excellent video. Thank you

[@bradpittman5075]

Very good. I dunno about you guys but In my experience, rwd 275, 28x10.5, once you are making over 650-700 you will generally need to start using a strategy for traction on the leave. With that said, it is very silly to me to watch videos with people claiming 1000,1200, 1300 or whatever and then they go run 140 mph in the 1/4 mile and their cars are like 3200 pounds… obviously there is a disconnect somewhere in there. Even if they were going 1.6 60 foots or something.

[@m5nut]

Living in the UK I have always had a problem with the dyno slips given to people I know (never dyno'd any of my cars). I sit there thinking "how can a tuner know the exact drive train losses on X or Y car?". It's just bullshit and naivety, on the customers part, that see's this practice continue. Hub dyno's for everyone! And we will all quote HHP as the norm from then on.

[@kitastan]

Afyer power run the drive train is slowing down without the engine and the dyno is calculating loses there. That is how it knows.

[@MattyEngland]

Looks like it's going to be another good vid 👍👍

[@SR22VET-S15]

A dyno is primarily a tuning tool, people get too caught up in numbers and there are too many variables. Nothing is more accurate than the blacktop dyno with trap speed though.

[@St0RM33]

4:18 Mate is "Diamater" Australian for Diameter?

[@billbrockbank8111]

You compare a mainline chassis dyno then hub dyno and proclaim the losses remain a constant..... Mainline doesn't read coastdown losses does it? It estimates ... OR measures losses.

[@eclipsetrekker]

Best fucking video i seen all year!! Thanks for the honesty.

[@oscarzt1652]

I had my focus ST170 make 160 brake horsepower and 210Nm when measured on a rolling road with eddy retarder. im from england.

[@sanjayabale]

brilliantly explained. Thank you

[@Catbus-Driver]

Regardless of dyno or location in the world, a stock K24 Honda engine will be capable of 200+ WHP right?

[@JayJay-_]

the measurement of horsepower is a comparative tool to assist in tuning and that's about it.. if you want to talk sheyat put it on the track

[@tdlaustralia7791]

You could have a dyno day or single event winner, if they all used the same dyno with the same calibration, i think, but certainly not some overall dyno record. Everywhere i look for performance parts for my car will have dyno graph with very nice but bs promises.

[@kesterglasgow4895]

Thanks motive video knowledge and proof

[@hardcoreep]

Agree Andrew, have been fighting it out with my friends on the UK forums for decades. Why try figure engine HP from a chassis dyno? SMH.

[@WraithDeath]

Plenty of American enthusiasts are gonna be triggered by this 🤣

[@MrLincoln87]

Love the commodore scene with Walky packs getting ripped on for having a 555 package / boot badge lol Even commodore/hsv standard have the 325 badging on the rear. What a joke. And yeah, so essentially ... fudge the dyno the before the work to get a lower rating, fudge the rating after the work to get a higher reading. Used to love seeing some cars at certain shops getting high kw/hp dyno readings than other shops, but then getting slower MPH at the track. 330rwkw with a MPH to match a 275rwkw figure.

[@bens_gone_nomad5299]

Really like this tech feature 👍🏻

[@martinrodger9565]

Modern dynos employing a ramp run feature all appear to have a factor of error. As noted in the video: inertia only ramp runs output a higher hp than a retarded ramp run. A fast ramp run outputs higher output than a slow ramp run. Part of the differences/errors appear to be in the recording and averaging of acceleration. As you make the ramp run longer, have more data to average over, the error appears to go down. If you worked back to true steady state you would negate the acceleration and interia errors and could calculate braked hp and not a fudged hp. It is also much easier to identify and quantify wheelspin in steady state compared to ramp runs on a chassis dyno. There are arguments around the ramp run simulating the actual acceleration of the car on the road, this is obviously dependant on many factors including gear etc. Unfortunately steady state measurements take a lot more time, put a lot of strain on the car, potentially more than you will ever see on the road depending on hp and weight of the car. Depending on the ability of the dyno controller and PID it can take anywhere up to 15 to 20 seconds to get a “steady” reading. This is a ton of time a full hp/tq. Dyno cell Cooling requirements go up to try to keep things safe and with all these factors ramp runs became the go to for a number of very good reasons. However, we still appear to be fighting the error associated with ramp runs. I’m not saying ramp runs are not repeatable on same car same dyno as the error, at a point, appears to become consistent : hence you can tune using them. As soon as you move to another car, a different dyno: a factor of difference/error will most likely appear. There are a ton of factors which could be discussed. A test which may be interesting is to compare different ramp run settings versus steady state on a hub dyno to see where the ramp run error hopefully reduces to negligible. The odd methodology is using higher ramp rates on higher hp. I believe this is to give cars less of a hard time, more hp, more heat and stress, but this methodology must be increasing the error and the outputted figures as the hp goes up…

[@martinrodger9565]

Further point on high hp ramp rates being higher: probably just as much about protecting the dyno retarders from heat as much as protecting the car depending on dyno setup, retarder sizes etc. In summary as figures go up; it appears the bullshit follows 😂 Trying to get everyone on the same page of bull is not easy. I suspect Todd from Mainline has done a ton of steady state versus ramp run measurement at high hp to understand it. His test rig had all the intent. I think there is a necessary evil in here with ramp runs and 1/4 mile time bombs and keeping things alive and affordable. My other understanding was the dyno dynamics added a straight 1.15 to 1.16 correction to get from wheels hp to engine calc hp due to pressure from overseas markets including uk. As Andrew says, these calcs are bonkers across a spread of vehicles. I think they can also do run down drive train loss measurements but this can be manipulated or messed up by brakes etc.

[@MotiveVideo]

Todd has run dyno competitions and worked with shops who need 5000hp capable dynos. His teachings are what has taught us so much.

[@MariosEvoCy]

You can compare between two different brands of the same type dyno, and yes there is a % difference between the two. You can compare between two cars in different parts of the world put on the same exact dyno, the same altitude, with the same whether station and ambient conditions, You can also compare between two cars if both use Virtual Dyno software i.e. and all else is kept the same. As long as you know the difference in either % or in fixed hp between dynos, and everything else is kept exactly the same, then you've got a pretty valid comparison. I do agree that it is difficult for an accurate comparison between two cars in two different parts of the world, but it is not something that cannot be done and also on the fact that dynos are indeed a tuning tool and nothing much beyond that, and that what really matters is E.T and MPH.

[@raheengabier3984]

Uhm???

[@xWheatThinz]

Very informative 😎🤘

[@mdnovaman]

Andrew, our bhp figures you mention. could you please explain why the figures on a reliable retarder dyno (agreed they aren't all good) match almost perfectly the quoted manufacturer power figure. that are stated by in some cases billion £ oem manufacturers? The dyno doesn't know what car is sat on it, so its not doing a quick sneaky google to make sure its telling you the right thing and every wheel tyre and drivetrain will have a different loss, but if its a complete guess/rubbish then how come its almost always matching rubbish to what bmw,audi,nissan,honda etc etc quote? i completely agree that shouting numbers in a bar/pub are about as much use as a chocolate tea pot when it comes to dyno figures. but this argument has always interested me. cracking vid with some very valid points, my question though, what makes Australian guess work any better than our guess work.......?

[@user-br3mj7dd7r]

I made a dyno run with a completely changed gearbox than stock no previous run. The oem gearbox had a 4th gear of 1:1.03 and the changed one had a 1:0.985 should the results be recalculated because he searched for my stock vehicle on the dyno list? Or it makes no difference because I'm guessing the dyno calculated wtorque transformed it into whp and then to engine hp by a stantard 15 % for fwd cars. Does it take into account the gear ratio and devides my numbers by 1.03?

[@boostben]

I thought BHP was calculated by the change in rate of the slowing of the Dyno? This is only done on an inertia dyno....it knows how fast the roller decelerates naturally with no load. You then do a pull and press the clutch in and it will decelerate faster as the roller is now spinning the drive line? Somehow it figures out some factor to apply based on this? Maybe? I could be way off...I try to only use hub dynos for the reason you stated...very long pulls.

[@MotiveVideo]

The inertia dyno can do that deceleration test, yes

[@nordic5490]

There is one error in this video, the tyre speed over the roller is the same regardless ofthe deflection or the tyre, ie, the gearing or mechanical advantage remains the same, regardless of the tyre deflection. If it didnt, try and explain where did that excess tyre go every revolution ? You could also consider the tyre as a belt - regrdless as to how that belt runs over pullys, the belt speed remains the same.

[@eclipsetrekker]

The gearing does change as the radius from the center of axle to drum surface changes. Your excess belt is being pushed out in the x and probably z axis somewhat but really doesn't have anything to do with this calculation. The mechanical advantage WILL vary based on the radius mentioned above.

[@nordic5490]

@@eclipsetrekker completely incorrect. If the tyre surface contacting the roller is moving at 1m/sec when the tyre is perfectly round, then this is 1m/sec top and bottom or the tyre. This 1m/s is also the speed of the surface of the dyno roller and let us assume there is no slippage for ease of calculation. What if the tyre was severely deflected ? For that same axle speed, the top of the tyre is still moving at 1ms, and..... the tyre surface in contact with the dyno is also still moving at 1m/s (the amount of tyre contacting the roller cannot not be added or lost to the system - where would the excess tyre go ? Bunched up like some kind of failed casette mechanism ?) Because the tyre contacting the roller is still moving at 1m/s, the roller surface still moves at 1m/s as it would have with a round tyre, thus the roller still rotates with the same rpm as it would if the tyre was perfectly round. Is your head exploding yet ?

[@eclipsetrekker]

@@nordic5490 I'm not going to continue a conversation with a disrespectful individual. Live in ignorance sir, good day.

[@Jrautomotive1]

Amazing 🙌🏽 my car just done a 1/4 mile in 13.1 I think I could have got into the high 12s but not enough time however the car made 391 at the hubs!! I was told that’s 490bhp is this correct or does that sound a little off? Oh cars running BPU at 1.2 bar boost stock turbos

[@adrian_silus8975]

Been waiting this 😁

[@Libadergiotis]

Great video! Any info on the intro / outro song?

[@darianistead2239]

Like those boostedboiz in the states getting higher whp figures than the turbo flow rates 🤣🤣

[@Red2l16v]

You can get more power than a Turbo is rated for. The turbo is rated at a max flow at a certain efficiency not at choke flow rate. So a "300hp" turbo can exceed that rating but may be doing it very inefficiently. However when you're limited in racing by rules you tend to push things beyond optimal. That's why people blow up turbos superchargers and engines at the drag strip all the time. They are running it beyond its engineering limits to win.

[@darianistead2239]

@@Red2l16v Not true. You maybe able to exceed your compressor map on some turbo's to a certain extent but your turbine is certainly a choke point resulting in more back pressure. Your compressor speed is also a limitation, more boost doesn't necessarily mean more power, in fact it can mean the opposite when running outside it's efficiency range by generating too much heat.. Hot air is less dense, less air, less fuel, smaller bang, less power. Drag and rally cars mostly kill turbos because they are exploding fuel in the turbo all the time, to get them to spool artificially when the engine rpm/load/ exhaust flow is insufficient to do do so on it's own. It's called Antilag/2 step/bumping in etc etc.

[@florian_montuzet]

It was really interesting.

[@jessegregoryCREEKSQUAD]

I saw a video of banks power make 1,400ish engine HP on a engine dyno with twin compound turbos and a huge whipple supercharger, id deffinatly recomend looking at it and seeing what u think :)

[@kUNCHRIS]

Not wrong .. just different .. got it

[@rob9752]

Why does gear used change the numbers? The Engine makes the same torque regardless of gear selected, but the gear multiplies the torque at the roller or hub, but at the same time it changes the roller or hub RPM, and since the formula for HP is (( Torque at the Roller x Roller RPM ) divided by 5252 ) if we pick an engine rpm, say 4000rpm, the Torque at the rollers is increased in a lower gear but the RPM is lower so the HP power at the roller should be the same. To me it seems the maths is saying the transmission gear selected makes no difference

[@mareksumguy1887]

Because many gearboxes have a “gear” that isn’t really a gear. It simply connects the input and output shafts (in the gearbox) without passing through a gear set (so it’s 1:1) … so there’s no frictional losses, as is the case with transmitting the power through a gear set (more so with helical cut gears).

[@viewfield5]

On the Yaris is those HP figures quoted for thw chassis dyno and hub dybo, the HP at the wheels or calculated to the engine HP?

[@MotiveVideo]

We NEVER use calculated engine hp. Only at hubs or at wheels

[@slicktop2jz855]

Does nitrogen vs oxygen affect the dyno readings via the tyres....ie the way the heat affects each one

[@MotiveVideo]

Not really. It is all about tyre temperature and friction

[@slicktop2jz855]

@@MotiveVideo sweet as cheers bro

[@nemanja162]

Unigroup engineering did a great video on fudging dyno figures.

[@Walterronny]

Something is wrong there when hub dyno read higher, my experience on my hub dyno is reading almost manufacturers claim and even less than roller ones..

[@MotiveVideo]

The physics of a hub reading less than roller is impossible. something very wrong if so. Roller mist be set to “calculated engine bhp” to read higher than hub

[@Walterronny]

​@@MotiveVideo it's not about physics, it's a tool that measure torque , i can say a roller will read even higher to the wheels due wheels , im not saying reading always less than roller, maybe same than roller if roller is good calibrated but i will not be happy if my dyno reads +50hp of a car. my hub have been comparing with a lot of rollers and good calibrated ones, measure almost same hp/torque but as you know there are a lot of dynos reading to high.. i can't imaginate to dyno pull a stock Civic FK8 TYpe R and my hub dyno measure 360-370hp at crank or so from stock when these cars even hardly make 320hp as Honda claims..i will not even sleep good lol. dont get wrong, just id like to share info and learn of course all time. Video is really good but part that these hub dynos and saying all hub dynos reads +50-100hp..i dont agree. from my experience!

[@nizamnordin4666]

Better tools achieve good result....

[@hoslyr86bass]

Great video

[@svrautosport1632]

Not agree... WHP Will differ even between runs, depending on tire temp gearbox oil temp, differential oil temp ect. Even strapping method makes a difference. Let's take another variable, wheel size... The inertia of 16" vs 19" wheels is quite different, which you will notice in whp numbers If you have a proper dyno that does the effort of measuring drivetrain losses instead off just adding a percentage, all those variabele will ben taken into account when losses measurement is done. For example my own dyno in the shop, if you look to whp numbers, between 5 runs, it will differ, but engine hp is the same because losses differ, but engine numbers are consistent. If i test a 100hp car or 600hp car, in stock form, you measure manifacturers numbers within 2% all day. I not argue adding a user defined losses %, that is totally rubish

[@CorpseExplosion]

Great stuff

[@tajypops123]

Just curious, how come you mentioned 'you should always load it up to build some boost before starting the ramp run'? Would it not be more relatable to real-world driving to floor the throttle and hit the space bar at the same time?

[@MotiveVideo]

remember the dyno is accelerating the car, so once you press the apace bar and it star the run, you need load on it like real life👍

[@tajypops123]

@@MotiveVideo but if you're going to load it up in steady-state before starting the ramp run - wouldn't that be like brake-boosting for a second before every pull you do on the street?

[@gabriel_lim82]

Good video

[@muskytuned]

Awesome video as always! At the 6:15 mark you mention when the tire deforms on the roller it will decrease the diameter which in turn will change the rpm. Regardless of increasing or decreasing the rpm, that will influence the speed of the roller. Wouldn't that mean that it cancels out the change in diameter since the parasitic losses of the dyno increase with roller speed. Since the dyno only calculates hp by the rate in which it accelerates a roller or a load cell, then determines torque output based on the rpm where the hp was acheived. That's why you can get a hp reading on a dyno without an rpm signal but not a torque reading. The deformation of the tire of course will increase the rolling resistance which in turn will reduce the power transfered to the roller. That being said ignoring the increased rolling resistance, the tire deformation should only alter the torque reading and not the hp reading because the rpm of the engine is no longer in sync with the roll speed (unless you sync'd the rpm based on the speed of the dyno roller) Man this turned out to be a much larger post than I originally planned. lol

[@carlton8546]

You are incorrect in saying " dyno only calculates hp by the rate in which it accelerates a roller or a load cell", this is true for an Inertia dyno but not a load bearing dyno i.e. retarder, which measures the torque reaction of the retarder in the load cell and calculates power using the rpm reading. The extra strapping lowers the power by inducing more load into the tyre that is not measured or accounted for in my opinion

[@spelereen4511]

Is retarder dyno also known as a load dyno?