Mark Shead

Thats correct and its the way I do it

Mark

Nash

iTrader: (3)

Mark Shead
Cool least i understood it correctly, Cheers Mark.

ECU Monitor Enthusiast

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I cant believe some of the replies on here by so called knowledgable people.

IMO, the dyno air sensor SHOULD be in the air filter as this is the air the engine is
consuming to make your horse power and thus is correcting the figure
for the reading obtained (assuming the correction alorithm is actually right)

The air to the filter should be ducted from OUTSIDE the cell
This will prevent the engine cell cooling air/exhaust heat from influencing the figures.

Placing the sensor away from the engine air flow supply is measuring the
WRONG air and giving you the wrong correction.

Its a bit like measuring the cars tyre pressure and saying thats the boost
pressure as its close enough to the engine

mechanic28

iTrader: (5)

well i be bumed,have not got a clue bout how rr work but did not know it takes into account the temp of air intake to compensate power readings out of interest how does it work out power at the flywheel

ECU Monitor Enthusiast

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Rolling roads calculate power at flywheel by working out losses.
This is done by pushing the clutch in after peak power and letting the
wheels slow down naturally, The time it takes and reverse load measured
on the roller load cells are used to calculate loss which is added to the
measured wheel power to provide a flywheel figure.

If the brakes are dabbed during the run down you get more power

mechanic28

iTrader: (5)

cool

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Matt,

Its a problem as the air in the cell is a mixture of temperatures and densities.

It ISNT the air going in the engine 100%

ECU Monitor Enthusiast

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What you saying is part right but what was mentioned above was not in
the line of the actual direct flow to the engine so any other place will
be an average or influenced either way.

If your going to measure it, do it in the right place otherwise any reading
will be wrong wether its too high or low a bhp.

Of course the air should be ducted from OUTSIDE the cell.

Mark Shead

Simon

Not on a Dyno dynamics RR this does not measure transmission looses so it would add any more power by touching the brakes,
The flywheel fig is a program/guess they worked out at the factory the bases I have been told its based on a Scooby that was tested on a engine dyno then it the car,
So a Ford running on one has a Scooby loss

Mark

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Mark Shead,

SUBARU

Fair comment about DD loss measurement though, not ideal though

rapidcossie

Why are the temps measured before the intercooler at all?

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Because the turbo will affect performnce as its an integral part of a
feedback loop. Hope that makes sense.

Mike Rainbird

iTrader: (3)

Actually what you have said is completely inaccurate, as measuring the air where you say is NOT measuring the air temp of the air going into the engine, it is just measuring the radiated heat soak that the engine produces .

The turbo is moving such huge volumetric amounts of air, that it will be pulling in the cooler air from outside the engine bay, with such high flow / speed, that within a few seconds of running, it won't have time to be heated up by the engine bay radiated heat (unless it is a cone filter (without the appropriate heat shielding from the obvious hot spots) which will be sucking a lot of the engine bay air in as well).

Due to where Cossie air filters are located, these are even more susceptible to giving exagerated readings and to prove the point, if Dave was to revisit the exact same rollers and ask them to repeat the run, but to just reposition the sensor to just outside the engine bay, then he would see a more realistic figure of 430-440bhp.

It seems strange in your earlier post that you deride the original figure, yet when this is explained to you how it is arrived at, you suddenly decide that this is the correct way .

All the DD RR operaters worth their salt have now taken to placing the sensor to measure the dyno cell temps (which is the temp of the air that the turbo will be pulling into it), as to do otherwise gives the grossly exagerated readings that RRs often get berrated for. If you want a figure for the pub, place the sensor as close to the engine as you can (and this goes for both RR and engine dyno ). If you want a figure that is more likely to be a realistic representation, then measure the cell temperature for correction purposes .

Also, I forgot mention that given there is a friendly rivalry that exists between Mark and myself - if there was a way we could disagree, we would be doing so . The fact that we agree on this, should be enough for anyone .

rapidcossie

Not really?

Surely the ONLY air temps that are important are the one that the engine is actually consuming?

mechanic28

iTrader: (5)

so what really is the poing in having a power run then

Mike Rainbird

iTrader: (3)

None what-so-ever, unless you know what to look out for to get a proper reading. However, as most people WANT high readings, there will be plenty of RR operators to accomodate .

Mark Shead

For me a RR is testing the actuall power the car is producing and the only correction that should take place is weather temp and pressure, As this is how the engine is working in its correct enviroment.

Mark

ECU Monitor Enthusiast

iTrader: (1)

Mike, if you dont directly measure the actual thing that affects calculations,
then its wrong simple.... Surely you can see that wether or not it makes
a positive or negative difference to whats expected.

And to clarify, the sensor shoudl be measuring the flow directly into the
air filter with air ducted from OUTSIDE the cell where it cannot be affected
by cell and exhaust heating. This surely is the IDEAL set up.

Only ever seen that at the Honda engine plant where I used to work.!!

rapidcossie

Why do you correct for presure Mark?

The pressure in the inlet manifold will be the same on a turbo car regardless of the barometric pressure will it not?

marco polo

iTrader: (1)

yo dave


you have turned the bullitin board upside down



great to see

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You correct for pressure as it does affect turbo efficiency.

The less pressure in the turbo, the harder it has to pump and the more
restriction there is in the exhaust turbine housing..

rapidcossie

We are measuring the horsepower the engine makes here, not turbo effciency

ECU Monitor Enthusiast

iTrader: (1)

Turbo efficiency affects horsepower if it didnt there would be no point fitting it !

You have to deliver a certain quantity of air to make a certain level of power.
If the air is less dense then it has to pump more to get the same density/pressure to make the same boost etc.....

Density is affected by temperature wether an engine has a turbo or not.

Less oxygen less power !

Jay,

iTrader: (4)

but its related is it not

rapidcossie

Flux Capacitor


I can see you point completly and understand how turbo effciency effects horsepower but I dont believe this needs to be tested for every power run?

Test the turbo during intial set up /development of that turbo but not during a 5 mins power run

dave cos4x4

iTrader: (5)

marco polo

i know.

but its very informative.

hello Pete.

i even joined back up to the gym tonight to get me away from all this.

i'm spending too much time on my arse.

ECU Monitor Enthusiast

iTrader: (1)

The more factors you measure correctly and take into account
the more accurate measurements will be.

Air temperature has a HUGE affect on power output of any engine.
Even more so on a turbo engine that consumes vast quantities of air
which magnifies the problem.

rapidcossie

I know that air temp is the most important factor in measurement of power on turbocharged cars thats why I cant understand correcting the figs rather than measuring at the temps you want.

ECU Monitor Enthusiast

iTrader: (1)

You correct the figures as you are measuring the engine running in its
natural state (as far as you can).

You dont provide it with perfect conditions as that never occurs on the road.

You measure it as it is......


Corrections are applied to provide a standard for everyone.

dave cos4x4

iTrader: (5)

i will have to check the housing,but iirc it may be a .70.

it is a bit laggy,look at the graph to see the spool up but i'm happy with that and i like it on track as its high revving anyway.

on the road it takes a bit to get it going if i'm honest,but when it does kick in you are going too fast for the roads.

you will have to get in to feel it for yourself Matt.

rapidcossie

Starting to understand a bit more now Simon

Just seems like the DD adds power on in perfectly normal situations, a ACT figure of 50 deg for example.

Staffi

iTrader: (1)

How's it going Dave....

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If an engines power output doesnt fall for the same steady state conditions
apart from the air temperature then its magically efficient so the power
readings are corrected upwards to show that.

ALso, if the sensor was fooled you get exagerated readings.

Corrections are used to standardise enviromental condtions so that
setups are easy to compare but obviously if not everyone follows the same
setup and rule, the standards are bollocks .... TUV....

dumped

So if you correct for pressure differences on an n/a engine for example they are of the order to deal with very small changes and effect the power in a certain way(whatever the calculation is) fluxuations of millibars etc.
Now you have an engine that is turboed - these fluxuations will change the end power but with what magnitude? I doubt they do it in an exactly related way and effect the end power reading in the same calculable(made up word maybe ) way as N/A due to different turbo operating efficiencies/boost used etc.
Such I believe may be the same problem with intercooling and efficiencies and still using straight temp corrections from n/a aplications.

I am not saying there are not differences as I believe there obviously are from running in different circumstances (temp/pressure) and these need to be considered, I just dont think that n/a corrections which are easier to calculate relates directly to turboed applications or that you get an accurate result.

hope that makes sense lol

ECU Monitor Enthusiast

iTrader: (1)

The calculations are the same turbo or not.

The quantity of air consumed is larger and will have a larger effect as the BHP figures get higher.

rapidcossie

I can see why the pressure correction needs to be done on N/A cars as i suppose a higher barometric pressure is forcing more air into the engine.

On turbo cars its the turbo that does this weather its effcient or not.

ECU Monitor Enthusiast

iTrader: (1)

If the air is less dense before the turbo due to the air being at a higher
temperature then the engines efficiency is lower.

Thus the "correction standards" are applied to express power figures of
any engine on any dyno as if they were all operating at the same conditions.

Hope that makes sense

dumped

I "doubt" that the corrections applied are correct. You are saying about working back to an engine in its natural state - to do that you should remove the turbo/intercooler etc - I "doubt" the same correction for n/a works back with turbo due to the different efficiencies of turbo/intercooler systems and the scales they effect at etc, these are not accounted for.