Custom Code Reflash dyno result

**shaneth** · 24-01-2009, 11:55 PM

here is my old one

and here is jasn78 with chip, fmic and exhaust.

Now what i fail to understand is how you can work out the car is loosing power (besides the heat) going on the Trap speed. Surely if you bog down at the beginning then you wouldnt make a good trap speed and if you get wheel spin and back off then you wouldnt get a good trap speed. Can you enlighten me please.

**Golf Houso** · 25-01-2009, 12:01 AM

Tune aside whats the been the difference between your car on those runs you have just produce to what you have run recently?

**gregozedobe** · 25-01-2009, 12:12 AM

Trap speed is largely dependent on how much power your engine produces (area under the graph).

A bad (or spectacularly good) launch doesn't make that much difference to trap speed, even though it can make a big difference to your ET.

If you back off for a significant amount of time (eg to regain traction) that will reduce your trap speed (but only because you aren't applying full power over the full distance). But off and on again quickly won't have that big an effect on your trap speed.

So comparing trap speed is a good way of comparing power, particularly for the same car with different tunes. That is why some people prefer to look at trap speed rather than an (adjusted) dyno figure when assessing whether a particular modification has improved power or not.

There are even a few calculators around that can tell you how much power your engine is producing just by entering your trap speed and weight (or how much power you will need to get a specified trap speed).

**Sharkie** · 25-01-2009, 06:33 AM

Have to agree here Shane, trapspeed is important and in your case down on where it should be.

Use the calculator here http://www.rpmoutlet.com/dyno.htmto get an indication and as stated at the bottom

"Our horsepower calculation is correct by the definition of horsepower. Horsepower is a measure of the force required to accelerate a weight to a known speed in a known distance. This means that the generated horsepower provided by this calculator, is the actual horsepower at the rear wheels."

The maths theoretically is fine and we can assume similar principle applied to FWD ? Correct me if I'm wrong since the maths involved shouldn't change.
The calculated provides a slightly higher figure than expected across the board and the error seems to increase exponentially. ... ?????

Weight of Polo = 1190kg = 2623 pounds

Your previous runs (stock 2007) all had your calculated kw atw around 96-97kw which is pretty much where it should be taking abovementioned error into consideration.

This time around it has your atw kw around 111kw.

Jason's for instance is 144kw atw which is pretty much where it should be taking abovementioned error into consideration. Since both your car and Jasons car is about 133kw atw, on the night here there was definately less power getting to the ground.

Did it feel down in power in any way? Not saying these calcs are in any way foolproof, and people can (and probably will) pick them to pieces, its just that they have been found over years to provide consistent usefull (if slightly inaccurate) results.

**gregozedobe** · 25-01-2009, 07:17 AM

I wonder if the consistent error is due to Polos (like most turbocharged VAG petrol engines) having a fairly "flat" power curve compared with a NA engine of the same power output ? This gives them more "area under the graph".

Regardless of this discrepancy, trap speed is still a very useful indicator of actual power output when comparing mods on the same car (unless you add or remove significant amounts of weight).

**shaneth** · 25-01-2009, 08:14 AM

Yeah I'm not say trap speed isn't usful, just can't quite get my head around it. I know how crap my launches were for whatever reason and know I could have gotten more out of it. Did it feel down on power, well yes thinking about it I guess it did but I would put it down to temp. Compare jasons to mine we are talking 16 degrees lower (what's the equation for how many kw you loose for every degree the inlet temp goes up.). Also the fact that I was sitting around for 30 min on time and 90min the other. So heat soak would also have been crap. And then you have the humidity, how much does that have an effect on power?

Golf houso only clutch mate.

Looks like I'm going to have to go to a private road and practice my launches like I used to in the old days. And get this fmic and down pipe fitted then go again. Would have been good if another polo was there to compare times against. But it's all for fun.