The Great Dyno E-Doodle debate

[Quinny]

I am not sure if this is really the best place to post this question, but I would like to know how a dyno can read differently from another.

My understanding is that a dyno uses calculations based on variables such as torque, temperature etc.

So, if everything is done correctly (i.e. sensors in the same place, car strapped down correctly etc), how is it that one dyno can read differently from another? I realise that there are environmental factors (temp, humidity etc), and they will make some difference, but they are still giving an accurate figure based on the conditions.... Maths doesn't lie, if the same calculations are used, and the same testing procedures are used, then the cars should get similar outputs.

[justin911]

paul, were debating if a stock r33 gtst (a manual one i think were talking about) makes 125kw... or 140kw stock...

[paulr33]

and again if the still have the same power curve, which i highly doubt unless its remapped its still the standard ecu. it has the speed cut, excess airflow protection, knock pickup drops timing and richens up, you dont get any readout on the various sensors, you cant control 02 feedback, you cant get notificaiton of knocking, airflow and injector limits, you cant monitor any of the values (without console cable).

so i still fail to see why u would want to stick with the stock ecu, but if you want to, then do that. i can only see benefits changing away from the stock ecu (to a suitable one).

right and with a bucket load of suspension work and good weathe conditions i could probably manage similar times on good radials at similar mph. maybe he has weight reduction, maybe he has different rubber, maybe it was warmer, maybe it was colder. there's a billion maybe's. the point is, its a much worse basis for comparison than dyno runs as theres a stackload more factors, including the driver.

[paulr33]

I am not sure if this is really the best place to post this question, but I would like to know how a dyno can read differently from another.

My understanding is that a dyno uses calculations based on variables such as torque, temperature etc.

So, if everything is done correctly (i.e. sensors in the same place, car strapped down correctly etc), how is it that one dyno can read differently from another? I realise that there are environmental factors (temp, humidity etc), and they will make some difference, but they are still giving an accurate figure based on the conditions.... Maths doesn't lie, if the same calculations are used, and the same testing procedures are used, then the cars should get similar outputs.

you are correct, in questioning how they can read differently. they have a bunch of sensors that obtain atmospheric conditions and car conditions (or settings) to give a power at given wheel speed. these include things like;

ambient air temp

air intake temp

ramp rate

air pressure

humidity

and so on. if its locked in shootout mode most of these can't be altered however it still has room for error. there is big document on the shootout mode procedure and how it needs to be done. a simply ommision such as not using the air intake sensor properly can affect the result. ie: having a hot pod sucking in hot air but placing the air temp sensor on the dyno pc printout stand. the car will make less power as its sucking in hot air but the dyno thinks its 18deg in the air intake so it corrects based on that. likewise if you were to put the air intake sensor near the pod (not attached to it) and did the run its likely to make more power than perviously as all of a sudden in ambient temp is say 22deg and then the intake temp is 55deg (sounds about right) it will go ok it makes xyz power, but because its sucking in mega hot air, it really makes xyz + 10 power.

shootout mode corrects to an even playing field so that someone in syndey on a hot day that does a power run and someone in tasmania in winter that gets a power run, they are both in comparison even playing ie. ie: it lets say pretends the airtemp for intake is 20 and ambient is say 25 for both dyno runs. it will increase the sydney run as it was in hotter air, whereas it will drop the tasmania run as it was in colder air.

maths certainly dont lie, but human intervention with the systems will affect it. there are other manual corrections you can apply such as ramp rate adjustment (pull the car tighter to the rollers, this can affect boost build rates). selecting different shootout modes for the wrong car, ie choosing SHOOT8 for a 6 cylinder, choosing SHOOT4 for a v6 turbo and so on, these have inbuilt base line corrections and values.

im yet to this day see any workshop use the airtemp sensor correctly and place it in the air intake or near the air intake inlet and have the bonnet closed in melbourne. again im pretty sure thats the right way to do it (anyone care to correct?)

[nfi]

Everyones missing the point paulr33 was trying to make earlier which is the point of this topic.

The number of kw's a car makes on 1 dyno is completely irrelevant. The only way any number on a dyno is useful is if you change something and run it on the same dyno again. All dynos will show different readings because of temperature, ramp rate, humidity, temp sensors etc. This is on top of how long ago the dyno was calibrated.

Therefore dyno readings are only useful to measure an increase in power if a baseline run is done, then the mod completed and then another run on the same dyno set up the same way. People need to stop getting caught up in the number and use the same dyno the whole modifying process and simply watch the increase.

I am still not sure that is explained very well but I tried.

A good tuner doesn't even care about the peak figure anyway. That is just a by product of tuning for the most amount of torque across the rev range.

My 2c.

[paulr33]

here is a drill down (that i know of) for the dyno dynamics settings at the bottom of each run.

BP - pressure

RH - uknown

AT - air temp

IT - intake temp

RR - ramp rate

TN - unknown

This pic is taken from one of my runs and you can see the AT and IT are almost identical.

my car has a pod in the engine bay which sucks in hot air. so its likely that the IT is wrong as if its sucking in hot engine bay air, then it wont be 17deg. 50deg odd sounds about right. so because of this omission or error, it guess you could made less power compared to an identical run, but with the intake sensor in the right spot.

[mad082]

i never said it was in a skyline, i was just proving that times and speeds are 2 different things.

also have you even had much to do with stock ecu's? you automatically dismiss any decent power from one saying it must be remapped, or the dyno is incorrect. it is possible to get decent power from them. you just have to know how to treat them. but then you have to take into account all the variables in the motor, like how well the fuel pump is working, how the compression is, how well the afm is working. sure the stock ecu runs rich, but if someone has a dirty afm then that will lean it out and give it more power.

and average power doesn't matter that much on the strip. all that matters is from about 4500rpm up. so who cares if one car makes more power at 2500rpm, i'd just drop it back a gear. i plotted my graph against my mates and i hit his max power at 5500rpm, then i continue up for another 20hp. and they were done same day, same dyno. 1 after the other. sure you could say that the dyno operator did something different, but on the road mine feels a lot stronger.

but the whole point of this depate is that 1 person came and made a statement that he believed to be 100% true. we are simply pointing out that there is plenty of proof to suggest otherwise.

and how do you figure that a stock ecu can't have a smooth power curve? especially if it is running rich.

[Birnie]

I think 2 points we're trying to clear up (maybe 3)

1) What does the stock R33 GTS-T get at the wheels (no mods)

2) A stock ECU cannot make it over 150rwks

The maybe 3) - How much extra power do you get from after market ECU (peak has only been discussed i guess, but obviously the whole shape of the curve would be nice to compare like you said)

Been an interesting read so far, including the dumby spits

And the source of all these arguments being dodgey dynos of course.

Go the 190 at the wheels on the standard ECU

[justin911]

i dunno why you guys are giving the life story of dynos.............

everyone knows diff dyno/diff day/diff car you get a differant reading...

the hole thing only started because themafia said anyone who gets over 150kw with blahblah mods "is talking shit"

[2rismo]

This thread is dumb because of comments like;

"a manual gearbox generally takes roughly 12% drivetrain loss, "

"manual gearboxes lose 60kW"

Wake up please. Dynos are for tuning.

Adrian

[paulr33]

paul, were debating if a stock r33 gtst (a manual one i think were talking about) makes 125kw... or 140kw stock...

so do you feel his 125kw run is wrong? do you feel its right?

i certainly feel its correct, i paulr33 believe jono took his car to a dyno in a factory configuration and plonked it on a dyno and it came out with max reading of 125rwkw. this doesn't mean all factory configurations will make that level of power. i also believe i took my car r33 plonked it on a dyno and came out with 141rwkw. it doesnt mean all r33's will make that either. its just a given power level and nothing more. what is certainly likely is that jono's run had different settings to mine. different air temp, intake temp, ramp rate, tyre pressure, different shootout mode (if it was infact in shootout mode) and so on. many many many factors, we could go on for hours, we also saw an r33 near stock make 187rwkw (wrong gear). again if the parameters had been entered correctly i think it would have corrected it to a 1:1 diff ratio readout instead of the higher gear ratio, which skewed the results. someone said if the parameters were spot on, it wouldnt have mattered (which sounds acceptable)

but the point is, it doesnt matter. it only matters if you compare xyz run to xyz run on the same dyno, on the same settings, ie: jono makes a change and then goes to the same place and same settings, then its useful, i dont think he's been to the same place each time he has made changes, heck i havent either. most of us dont i think.

not having a stab at you, just it was easy to clear up with your direct question

[mad082]

what you have to realise with a pod in an engine bay is that it doesn't suck that much hot air. also when it starts sucking air fast then the air cools as it is creating a vacuum. and as it sucks more air, it may be sucking more hot air, but it is also sucking cold air. the pod is surrounded by metal, alot of which isn't affected by engine temp, so as the air passes this it is cooled.

[paulr33]

to summarize;

1) What does the stock R33 GTS-T get at the wheels (no mods)

depends on dyno settings + if it in fact is true stock.

there could be mods the owner doesnt know about

my stock run i had a larger muffler, maybe that added more power.

the happy medium seems to be somewhere between 120 and 140

2) A stock ECU cannot make it over 150rwks

a stock ecu can. a stock ecu can make 300rwkw.

that doesnt mean its good or going to great to drive.

stock ecu is not limited to power.

if you can work around the excess airflow, it will make as much power as airflow you dial in. its not like it will turn off the engine if it makes 320rwkw. it will just keep going about its business, but it will certianly be much crapper compared to a properly tuned ecu, or even a remap.

you cant change injectors, airflow meters and alter the cold start, warm start etc so you would be limited by hiflow injectors and some form oh hiflow hack afm, one that could flow more but run on the same voltage scale.

The maybe 3) - How much extra power do you get from after market ECU (peak has only been discussed i guess, but obviously the whole shape of the curve would be nice to compare like you said)

changing to a different ecu the power gain would be zero.

changing to a different ecu and having it tuned would be "reasonable" power gains. but if you have say 180rwkw on stock ecu and then decide ok time for powerfc, and make the same peak power, does that mean youve wasted your money? of course not as we all know airflow makes power, to get more power you need more air. but you can certainly tune the pants off to get superior response and economy and some additional features in an aftermarket ecu

[paulr33]

what you have to realise with a pod in an engine bay is that it doesn't suck that much hot air. also when it starts sucking air fast then the air cools as it is creating a vacuum. and as it sucks more air, it may be sucking more hot air, but it is also sucking cold air. the pod is surrounded by metal, alot of which isn't affected by engine temp, so as the air passes this it is cooled.

id be interested to know how youve tested this? my car runs a pod in the engine bay unshielded. i made up a poor mans cold air intake pipe (removed the pod) to run from the afm out through the stock fmic hole downards for my last attempts at heathcote. the result was sucking in much cooler ambient air from behind the front bar. just doign warm up laps on the track (track was wet) i could feel better response and more beef in the car as it wasnt sucking in hot air. i can feel it sucking in hot air, it bogs the response and doesnt perform as well when on full load, with given air "flowing" into the pod area. i simply believe sucking hot air in from engine bay is bad. i had a poor mans heat sheild which had lots of gaps and i need to really fix it properly. the stock airbox came out as the fmic piping blocked its path

[wolverine]

"when it starts sucking air fast then the air cools as it is creating a vacuum"

this isn't right mad082.

[mad082]

so do you feel his 125kw run is wrong? do you feel its right?

i certainly feel its correct, i paulr33 believe jono took his car to a dyno in a factory configuration and plonked it on a dyno and it came out with max reading of 125rwkw. this doesn't mean all factory configurations will make that level of power. i also believe i took my car r33 plonked it on a dyno and came out with 141rwkw. it doesnt mean all r33's will make that either. its just a given power level and nothing more. what is certainly likely is that jono's run had different settings to mine. different air temp, intake temp, ramp rate, tyre pressure, different shootout mode (if it was infact in shootout mode) and so on. many many many factors, we could go on for hours, we also saw an r33 near stock make 187rwkw (wrong gear). again if the parameters had been entered correctly i think it would have corrected it to a 1:1 diff ratio readout instead of the higher gear ratio, which skewed the results. someone said if the parameters were spot on, it wouldnt have mattered (which sounds acceptable)

but the point is, it doesnt matter. it only matters if you compare xyz run to xyz run on the same dyno, on the same settings, ie: jono makes a change and then goes to the same place and same settings, then its useful, i dont think he's been to the same place each time he has made changes, heck i havent either. most of us dont i think.

not having a stab at you, just it was easy to clear up with your direct question

have you ever though of being a politician, because you are so good at talking about complete and utter crap and avoiding the point.

the whole point with this is that themafia said, and i'm going to quote,

There is NO WAY a standard, run of the mill R33 will make 140 true rwkw. They are only 125rwkw standard.

that is saying that he is 100% correct and we are all wrong, and any car that makes more than 125kw has been on an inaccurate dyno. what we are saying is that it is more than possible for a car to make more than that and still have the dyno accurate.

and the other point we are disputing is this ripper

Anyone that says you can make over 150rwkw WITHOUT an aftermarket fuel controller or ecu, is full of shit.

frankly i find it hard to believe a 68kw gain from a powerfc, as the average is 30kw.

[paulr33]

well i have nothing further to add. like most internet chat and communication it is open to interpretation. i suspect if we had this conversation from scratch a local pub the outcome would have been different

[Sydneykid]

Wake up please. Dynos are for tuning.

Adrian

Hi Adrian, your car is probably a good test of dyno losses.

How much NOS you running?

What's the power with NOS?

What''s the power without NOS?

cheers

[2rismo]

Hi Adrian, your car is probably a good test of dyno losses.

How much NOS you running?

What's the power with NOS?

What''s the power without NOS?

cheers

LOL! It's a perfect example.

255hp @ tyres no gas

355hp @ tyres with 100hp gas.

lol

Adrian

[Sydneykid]

LOL! It's a perfect example.

255hp @ tyres no gas

355hp @ tyres with 100hp gas.

lol

Adrian

For the metrically minded

190 rwkw no NOS

265 rwkw with NOS

100 hp NOS = 75 kw

That means added 75 rwkw without loosing 1 extra rwkw in losses.

Yet another example of the % method for losses being 100% BS.

cheers

Edited July 18, 2006 by Sydneykid