Right then, yesterday I took the Leon down to Thor Racing in Coventry for it to be tuned.
First of all we had the standard car on the dyno (which is a hub dyno, so figures are at the wheels rather than at the engine).
The standard car made
130.7bhp and
236.9lbft at the wheels which equates to roughly
150bhp at the engine - pretty much bang on the manufacturers stated power.
We then ran the car without an air filter to replicate the very best airflow to see if fitting a high flow panel or cone filter could potentially make a difference. Over four power runs the car made identical power (within the tolerances of the dyno). Thus bringing us to the conclusion that on these PD150 engines, as standard an aftermarket filter offers absolutely no performance gains whatsoever - the only difference was a more noticeable induction note.
We then had the car back out in to the workshop and performed a "mufflerectomy" which involves cutting off the backbox just after the exhaust pipe runs over the rear beam. The backbox is then repaced with a straight 2.25" pipe and a new tip (i'm running a Cupra R style oval). We were all very surprised at how little difference in sound there was once the backbox had been removed. On startup there's now a slightly lower growl but on idle there is no audible difference between stock and no backbox - the difference comes when changing gear and you can hear a slight "chirp" from the turbo from outside the car (which I quite like). Inside the car you wouldn't be able to tell if it had been done or not and there's no droning on the motorway either at any speed or RPM.
The car was then put back on the dyno to see if the mufflerectomy had made any difference to the car's power and we were quite shocked to see that by this simple £60-£100 mod had actually made
6.2bhp at the wheels and
8.4lbft of torque. Over four more dyno runs we saw the power figure staying at a consistent
136.9bhp and
245.4lbft torque which equates to approximately
160bhp at the engine.
Now that the car was clearly breathing better, we removed the air filter again to see if an aftermarket high flow filter would make a difference. But once again the dyno results showed no gains in power. Leading us to the conclusion that the standard induction system provides sufficient airflow.
Conclusion
So all in all a very good days work having leveraged an extra 6.2 wheel BHP and 8.4lbft torque from just a simple, cheap modification. The added benefit was that I saw my average MPG increase by 6-8mpg on the motorway run home.
The next stage is remapping the car and I'll report back on Friday with the results of that.