GTI tuning modifications - what would you do?

[Maverick]

Maverick is risking a lesson from Bugracer with his 'not accurate for comparison' comment

To explain what I said a little better.

Cars run on the same dyno with the same operator, same tie down tension and same tyre pressure are a fair comparision but to compare cars that are run on different dynos, in different parts of the world, under different conditions, with different tyre pressures and tie down tensions are pointless.

[Maverick]

I don't need to explain myself to a guy that has no idea, because you just wouldn't get it...This isn't the only thread you have shown this on...I'm leaving it at that...Can you?

Pretty pathetic blitzen, you made the claim that dyno's are accurate and can be used for comparison and you can't back it up

[G-rig]

It's not that easy to compare dynos is it, unless someones got a program to type in the differences in intake temps, tyre psi and other factors? I'm trying to do the same thing myself at the moment.

[Maverick]

Some more information on why Dynos are not accurate.

http://www.sdsefi.com/techdyno.htm

"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."

http://www.pumaracing.co.uk/POWER3.htm

"Some time ago I had three almost identical race cars set up together in a group session at a rolling road. The engines were very similar except for minor differences in the camshafts fitted. One showed 118 bhp at the wheels, another showed 124 and the third showed only 98. The operator spent ages I'm told (I wasn't there) trying to find why the third car was so poor. It wasn't till the next day when that particular owner was checking things before the race that he noticed that the tyres only had 7 psi in them - the car had sat unchecked over the winter and no-one had bothered to standardize the pressures before the dyno test. In the race, that car went just as well as the other two and if anything was slightly the fastest of the three. That gives you some idea of how much power a set of flat tyres can absorb."

"Also called chassis dynamometers, these are used to measure power at the driving wheels. This avoids the inconvenience of having to remove the engine to test it if a tuning modification has been made. However, it means that the power figures obtained will be lower than the flywheel power because of the frictional losses in the drivetrain and tyres. This leads to one of the biggest sources of confusion, error and plain misinformation in the tuning industry. You see, as discussed above, all major manufacturers quote flywheel power so it is understandable that people want to know if the hard earned cash they spent on tuning mods increased the power of their engine and by how much. To know this for certain means knowing how much the transmission losses are. There is enormous pressure on rolling road operators to be able to quote flywheel bhp rather than wheel bhp and most operators now run proprietary software systems which "supposedly" print out flywheel power.

PROBLEM !! - THESE SOFTWARE SYSTEMS DO NOT AND CANNOT WORK !!"

http://www.sportcompactcarweb.com/editors/technobabble/9907scc_technobabble/index.html

[G-rig]

Some good information in there.

"The Sound of Silence" was also a good song by Simon and Garfunkel.

[Bug_racer]

Seriously maverick what planet you off , or should I say timeframe ??
Dynos have correction factors for temperature and altitude so the reading wont matter about air temp or where you are .

Everything else youve stated is all inaccuracies due to operator error . The dyno is a measuring tool and only is as good as the operator using it . If you cant get a dyno from X place with Z car and take Z car to Y place and get within 1% you dont know how to use the dyno !

Just remember hp is a series of calculations based on inputs , if your inputs are wrong then your answer will be wrong . Dont go blaming the way everything is calculated !

[shaneth]

Dynolicious is easy to manipulate, put in an incorrect weight and you will get a higher power figure. If the calibration of the accelerometer is not done exactly correctly or at a different temperature it will give misleading figures.

Id like to know if you have every calibrated dynolicious? and how does temp affect it?


On another note Mav Grow up, put the e-penis away (we arent all keyboard warriors) and take a chill pill. You dont need to teach everyone what you think you know. Just my 2c.

[Mischa]

On another note Mav Grow up, put the e-penis away (we arent all keyboard warriors) and take a chill pill. You dont need to teach everyone what you think you know. Just my 2c.

thats the most sense i've heard from this forum in weeks

[Bug_racer]

here is some more info to ponder over , this is for you Shaneth , let me know if its accurate

http://www.stealth316.com/2-calc-hp-et-mph.htm

[Maverick]

Seriously maverick what planet you off , or should I say timeframe ??
Dynos have correction factors for temperature and altitude so the reading wont matter about air temp or where you are .

Which is listed in what I wrote.

Everything else youve stated is all inaccuracies due to operator error . The dyno is a measuring tool and only is as good as the operator using it . If you cant get a dyno from X place with Z car and take Z car to Y place and get within 1% you dont know how to use the dyno !

What you've written doesn't make any sense. Since when did Dyno operators let the user operate the dyno? I assume you mean the dyno operator can't operate but even if you had good operators I doubt you could get consistent results closer then 10% across a range of cars.

Even the big manufacturers states that dynos vary greatly from site to site but you claim that they are accurate within 1%.

The biggest problem with dyno's are the operators! I had a dyno for a stage 1 GTI with 574.1nm and ~123kw of power, he checked and couldn't get it to read any different to that.

CES have a bosch dyno (old unit that plots directly onto paper) and I get a figure of 148kw. Stock GTI 123kw. No correction, no bs. Cars at the dyno day that had no changes from the previous year had the same figures.

Just remember hp is a series of calculations based on inputs , if your inputs are wrong then your answer will be wrong . Dont go blaming the way everything is calculated !

There are many variables with a dyno, even Dyno Dynamics recognise this and have shootout mode so that there can be some consistency across different sites. A car could still be strapped down harder or tyre pressures/grip could be different.

Here's an example

http://72.14.235.132/search?q=cache:t3E3--K8pW0J:www.fordxr6turbo.com/forum/index.php%3Fshowtopic%3D7654+shootout+mode&hl=en&ct=clnk&cd=5&gl=au

"1. Said Test Vehicle produces 282.1 rear wheel kilowatts @ 14 psi boost.
2. Said vehicle is then driven approximately 300 metres to another workshop where it is placed on a current model Dyno Dynamics chassis dynamometer equipped with the latest Dyno Dynamics Shootout Mode software. Software designed, we’re told, to ensure an absolute level playing field between every Dyno Dynamics dyno in the country (when fitted with the Shootout Mode software).
3. Once said vehicle is strapped onto the dyno and the software is set to the ‘Shoot6’ Mode (for six cylinder powered cars), a power run is performed for a relatively consistent result of 288.5kW @ 14 psi.
4. Said vehicle is now run with the ‘Shoot8’ Mode (designed for V8 powered cars), with the power run resulting in 304.9kw @ 13 psi.
5. Said vehicle is finally run on ‘Shoot81’ Mode (designed for turbocharged/supercharged or nitrous facilitated V8 powered cars) with the power run resulting in 317.8kw @ 12.5 psi."

"I have seen 30rwkw lost and gained by the way a car was strapped to the rollers ...

the key variables (that haven't been mentioned yet ) are temperature, barometric pressure and tyre pressure

if the dyno has a full weather station ... atmospheric variables are automatically fed in and should only act to standardise the results .... some dynos however only have a "local" weather station which requires the variables to be read and then fed into the dyno ... there is scope for variation there"

[Mischa]

we dont need a coroners inquest into every single post. just shoosh and accept that theres people out there that actually know more than you about something you cant get a degree in everything known to man just from browsing the net.

[Maverick]

Id like to know if you have every calibrated dynolicious? and how does temp affect it?

Yes I have and I also took a few minutes to check into it's operation. Try reading the manual.

http://www.dynolicious.com/docs/manual_2_0_0/setup.php

"NOTE: Although it is imperative that you calibrate the iPhone before using Dynolicious for the first time, you may want to take note that the accelerometers in the iPhone are somewhat temperature sensitive. For best results, you should consider recalibrating Dynolicious in the same environment in which the test will be performed."

"The iPhone’s accelerometers are not calibrated from the factory. For any given axis, the value returned from the accelerometer may be off by as much as 33%. The calibration function allows Dynolicious to compensate for this error and generate accurate results."

http://www.dynolicious.com/Dynolicious_Manual_v1_0.pdf

"The accelerometers in the iPhone are somewhat temperature sensitive. For best
results, calibration should be performed in the same environment in which the test will
be performed."

http://www.forums.gtechpro.com/viewtopic.php?f=38&p=457

"Dynolicious is not a bad application. However, according to our testing, the accuracy is not that consistent. This is due to the fact that the accelerometers inside the i-Phone need to give adequate signal to determine if the i-Phone was rotated or moved. They were not intended for a high-accuracy and high-speed application like vehicle dynamics.

The key is in calibration of the sensors. With the i-Phone you do a simple zero-out before the measurement and if the conditions don't change during the run you results won't be that bad. But if the conditions (mainly temperature) do change in the course of measurement you will be off. Most of the time conditions do change, ever so slightly, but enough to render the 1/4mile result inaccurate."

On another note Mav Grow up, put the e-penis away (we arent all keyboard warriors) and take a chill pill. You dont need to teach everyone what you think you know. Just my 2c.

My apologies for posting up arguments based on facts when there are too many people that want to believe their wildly inaccurate dynos and results from $12.99 iphone applications are accurate to within .001%.

[geoff_gti]

Good God, is this still going? All I hear is noise

Thanks for the youtube link Polar, I enjoyed that the most out of this thread.

I am not going to weigh in on this debate as it's all just numbers to me, I'm not doubting there are variables (and hence potential inaccuracies in meaurement techniques / tools) but perhaps someone should just take a chill pill to work tomorrow, or a colostomy bag...

But what would I know, I drive a Mk IV.

PS Tinto, you are a funny man. Is your ego feeling better by now?

[mrx]

But what would I know, I drive a Mk IV.

Yeah, I heard dyno's don't work on them.

[tinto]

PS Tinto, you are a funny man. Is your ego feeling better by now?

I'll live - just taking it day by day at the moment.
(and just to introduce ANOTHER tangent...) How is the gearbox?