Barometric Pressure Levels

[MKDR33]

Just wondering if Barometric Pressure levels can affect dyno readings/results?

If so, do dyno tuners take this into account and calculate the results against the BP levels?

[GTR1993]

when ever my car is dynoed it is entered from a BP guage. I can then assume that it does effect the final HP as it is used as a correction.

Edited August 10, 2006 by GTR1993

[R31Nismoid]

yes it will alter it, especially in the all hailed shootout

[Guest 40th-edition]

i wouldnt think it would affect a turbo charged car..

[MKDR33]

A turbocharger helps at high altitudes, where the air is less dense. Normal engines will experience reduced power at high altitudes because for each stroke of the piston, the engine will get a smaller mass of air. A turbocharged engine may also have reduced power, but the reduction will be less dramatic because the thinner air is easier for the turbocharger to pump.

So this statement is true?

Edited August 10, 2006 by MKDR33

[discopotato03]

I think the way it works is that there is less atmospheric pressure with which to feed the compressor wheel . Just the same as an NA engine doesn't "suck" in its charge air neither does the turbocharger . Technically there is no such thing as suck , just movement of air from an area of higher pressure to an area of lower pressure . So in other words there comes a time when there is not enough weight or mass of air (oxygen actually) available to feed the engine all it wants so power drops .

Its interesting to note that piston engined aircraft often seek to only provide sea level manifold pressure up to about 40,000 Ft . In the last world war RR used multi staged two speed radial compressors (technically superchargers because they were mechanically driven) to get high altitude performance from their Merlins and Griffons . The Americans used large low pressure turbochargers for Allison V type and Pratt and Whitney radials though they were not very high tech devices .

Sea level atmospheric pressure doesn't vary a whole lot arount the 1000 millibars/100Kpa/14.7 Psia so charge density would move around a little but not by a huge amount . Since we have no say about atmospheric pressure and temperature (air density) the only things we can bias our way are compressor efficiency and effective charge air cooling (intercooling) .

Cheers .

[MR331307]

shootout mode only changes due to the AIR TEMP not the temperatures entered they are only to list on the corrections part of the SHEET

The tune also changes where the air is more or less dense so this determines more or less power.

Edited August 10, 2006 by MR331307

[Robo's]

BP does effect dyno readings. My dyno tuners BP was always low , around the 980 mark and subsequently readings where higher than normal. When he was getting his Dyno serviced they didnt check this until a guy said your BP is very low. He now rings the local airport which is just around the corner for there readings before he puts a car on. Subsequently, dyno numbers arent as generous as what they used to be,

[R31Nismoid]

shootout mode only changes due to the AIR TEMP not the temperatures entered they are only to list on the corrections part of the SHEET

The tune also changes where the air is more or less dense so this determines more or less power.

wrong

Robo's is correct

[MR331307]

it doesnt

ring dyno dynamics

A dyno tuner should have a Weather station in the room of the dyno

To input the different temps ETC

[MR331307]

wrong

Robo's is correct

and sorry i dont know everything like you do

maybe you should open a shop

PS that photo SUITS ya big time

Edited August 11, 2006 by MR331307

[Kinks]

A turbocharger helps at high altitudes, where the air is less dense. Normal engines will experience reduced power at high altitudes because for each stroke of the piston, the engine will get a smaller mass of air. A turbocharged engine may also have reduced power, but the reduction will be less dramatic because the thinner air is easier for the turbocharger to pump.

So this statement is true?

Wrong. A turbo wastegate operates on relative, not absolute, pressure. 10psi boost is 10psi above atmospheric. If your atmospheric pressure drops so does the absolute pressure you are stuffing into the engine, hence power will drop in proportion.

discopotato's comment about 2-stage compressors is correct - they ran a "high boost" level at altitude, to compensate for the reduced air pressure. Running high boost at sea level would have blown up the engine.

[MKDR33]

so the BP levels have no affect with the dyno results, as they enter these into the dyno, but the temperatures surely must, as in winter my car goes harder due to the colder air outside, whereas in summer there is a deffinate power decrease..

anyone recommend dry-ice intake setups?

[FATGTS-R]

but the temperatures surely must, as in winter my car goes harder due to the colder air outside, whereas in summer there is a deffinate power decrease..

anyone recommend dry-ice intake setups?

Hence the reason why shootout mode software was developed. It compensates by either adding power when temps are high or reducing when they are cold. In theory, if you ran on the dyno in winter and then on a 40 deg day in summer results should be the same using the shootout method.

Dry Ice? Pointless for a car that sees any street driving as you would have to constantly fill it up. My mate has a 800rwhp dyno warrior with a large dry ice setup and 3 power runs later its empty. And its hard to find and not cheap.

[MR331307]

All you need is an ECU which runs a Air temp sensor and it compenstates the difference

If your temps are cooler you can run more timing and modifying fuel

if they get hottier you reduce the timing

When i data loged my car at the track and the dyno they were no different so this means the tune doesnt change.

you also have to have an intercooler Sufficent to your engines needs

if you had an aspirated engine Yes this makes a huge difference

but with an intercooled car nothing changes if its setup right.

The reason why the Hp changes on shootout is because the air temps go up and down

when i enter the temps the Correction Factor doesnt change

but if i put the sensor near the Exhaust or in a bucket of cold water it does.

like i said before the temps entered are only for the Corrections table

The reason for this is when you have the car on my dyno it might read 250 rwhp

but on someone else same dyno reads 260 hp

you can have a look on the sheet and see what temps are different.

Shootout mode also has a set RAMP RATE which you select and on turbo skylines will be SHOOT 6F which has a pre set Rate which you run your car on

When a dyno isnt run on shootout mode the Ramp rates need to be entered in and if the ramp is too much it will read less power and have a different tune to what its supposed to

and if its set really low will show higher HP readings and same the tune will be out by not being Enough.

People should respect Shootout mode and stop banging it as dyno dynamics didnt invent it for nothing.

I find tuning in shootout mode you wont need to do a ROAD TUNE as well.Because it loads the car up perfectly.I have done alot of reasearch into dynos and have found the Dyno dynamics to be the best for PERFORMANCE.If you want the extra DATA LOGGING computers like mainline ETC its just a extra option

Edited August 12, 2006 by MR331307

[Cubes]

And which shootout mode are you talking about?

There's many and as the number rises the ramp rate is less to prevent wheel spin.. i.e the difference between SHOOT6 and SHOOT81. The Shoot81 is much softer than shoot6 and for some strange reason shoot81 also reads around 30rwkw higher, well in a back to back run that I've seen.

[Robo's]

so the BP levels have no affect with the dyno results, as they enter these into the dyno, but the temperatures surely must, as in winter my car goes harder due to the colder air outside, whereas in summer there is a deffinate power decrease..

anyone recommend dry-ice intake setups?

Hang on, if they enter in the wrong BP levels,it will have an impact on the result, just like what i stated above when the weather station was wrong.

[MR331307]

And which shootout mode are you talking about?

There's many and as the number rises the ramp rate is less to prevent wheel spin.. i.e the difference between SHOOT6 and SHOOT81. The Shoot81 is much softer than shoot6 and for some strange reason shoot81 also reads around 30rwkw higher, well in a back to back run that I've seen.

SHOOT81 HUH

never seen that before

The shootout mode has 6 modes

SHOOT 4 (NA 4 cylinder)

SHOOT 6 (NA 6 Cylinder)

SHOOT 8 (NA 8 cylinder)

SHOOT 4F (turbo,NOS,Supercharged 4 cylinder)

SHOOT 6F (turbo,NOS,Supercharged 6 cylinder)

SHOOT 8F (turbo,NOS,Supercharged 8 cylinder)

theres a mode for rotary too

All have pre set Ramp Rates.If your not using the correct ones it isnt the Dynos fault or problem.Just bad Dynoing.AND if you can Brake Traction on a Dyno Dynamics dyno you have problems as i have had mark Hayes on my dyno Running 1142 RWHP and it didnt have a problem.Maybe suggest NEW TYRES

Like i said If its used correctly its the best method for TUNING AND finding out how much hp your cars got.

Just remember A DYNO IS A TUNING TOOL :sorcerer:

[Cubes]

All have pre set Ramp Rates.If your not using the correct ones it isnt the Dynos fault or problem.Just bad Dynoing.AND if you can Brake Traction on a Dyno Dynamics dyno you have problems as i have had mark Hayes on my dyno Running 1142 RWHP and it didnt have a problem.Maybe suggest NEW TYRES

Like i said If its used correctly its the best method for TUNING AND finding out how much hp your cars got.

Just remember A DYNO IS A TUNING TOOL :sorcerer:

Yer typo...

I do think you missed my point though.