Lies, damn lies, and rolling road print-outs.

[Bird dog]

An article that you may want to read before you depart with your hard earned for that all important piece of paper.

Puma Race Engines Technical Guide - Measuring Engine power - engine dynos and rolling road dynos

[bettyswollocks]

You`d be better of with a sandwich board

[Bird dog]

Originally Posted by bettyswollocks

You`d be better of with a sandwich board

It's not meant to put people off tuning their engines. It's meant for them to be wary of perceived power outputs that some rolling roads produce on print-outs.

I wouldn't trust a flywheel figure any more than I'd trust a Fox to keep guard of some Chickens.

Road wheel figure minus 15% is as good as anything to go by on your front drive Peugeot. Assuming that the rolling road actually got that bit right. Cheer up!

[stevoxsi]

Can't believe I actually took the time to read to read that....

[Bird dog]

Originally Posted by stevoxsi

Can't believe I actually took the time to read to read that....

Was that because you agree with it? Or don't agree with it?

Or that you didn't understand it?

Or maybe it's that you believe that all rolling roads tell the truth?

It also appears that you read it twice.

[john_h]

i have to admit i didnt understand it...

[Bird dog]

Originally Posted by john_h

i have to admit i didnt understand it...

Basically what it says is that the way in which most rolling roads calculate the flywheel bhp and torque figures is dubious to say the least. The only real way to get the flywheel bhp and torque figures is to take the engine out of the car and put it on a dynamometer.

The only figure worthy of attention is the road wheel figure because this figure is what the rollers actually measure. But even then, things like tyre pressures, tyre and wheel size, gear ratio used, etc, can alter the results quite alarmingly. There again, the best way to get the road wheel figure is to remove the wheels and use a hub dynamometer. Not many about though.

The 'cheat' at the bottom of the article is also done on a regular basis. Particularly if you bought the 'modification' at the place where you also got the rolling road figures done. These guys are only out to make a living too!

That's not to say that things like remaps and tuning boxes don't increase power, because they clearly do. The only way to get a true reading of that power increase is to do a 'before and after' run on the rolling road, preferably on the same day. Taking your car along after it's had a remap or whatever, will only tell you what figures the car is achieving over and above what you didn't know that it had before. Some diesel cars that I know of varied by 20bhp for the same engine type before any modifications were done!

[bettyswollocks]

Just like the one they use on my cars

Everyone has known for years rolling roads are not completely accurate .

Home | Torquetronix

[Bird dog]

Originally Posted by bettyswollocks

Everyone has known for years rolling roads are not completely accurate .

You wouldn't think that "everyone" knew.

People still go along, and pay their money, to find out how much bhp removing their 'Cat' or DPF has given them.

[bettyswollocks]

It`s not accurate but its pretty damn close , and if you`re getting your car mapped from 110 to 140 you can feel it , all men exaggerate about how big things are