Originally Posted by anielsen71
Thnx for the explanation.
Can you then confirm that with an optimal mapping, that takes care of the changed backpressure will be a performance gain by removing the DPF and "tell" the engine management that it's gone?
At least that is what I hear from you guys, from Promotec in South Africa and from the tuning my car.
Our pipes are manufactured with specific bends to provide a slight but consistent backpressure. This is then matched to the geometry or duty cycle maps in the software... once this change has been made in the software and the turbo is no longer racing for the boost limiter there is a gain of around 10-15hp on all m57n2 variants.
At this point further software modifications result in enormous power gains.
One thing these engines do not lack at stock settings is airflow... they run a lambda of around 1.25-1.3 standard... for this reason any modifications such as intercoolers etc will give no gain whatsoever... certainly not without further tuning.
Once the downpipe is installed you can really advance the injection timing to give the fuel more time in the cylinder to burn(Where some of your economy improvements come from), the first few degrees of advance actually reduce the EGT as DPF installed cars are set up to keep the DPF very warm as much as possible... think of the positive chain reaction here..:-)
You can then add significantly more fuel with a smokeless result without even asking for more boost, mainly due to the cooler running EGT and charge temp.
When more fuel is injected and the lambda starts to aproach 1.0 you can add more boost and inject more fuel if desired. This is when the party starts :-)
Finishing up with a lambda just over 1.0 means that you have improved the pumping efficiency of the engine by providing the correct amount of air required rather than an excess... additional strain on the turbo to provide more air than is required is done for emissions reasons by the manufacturer but has a real negative effect on the efficiency of the engine and the life of the charger.
We are trying... and failing to be be honest to get hold of a USA downpipe so we can provide an off the shelf solution to our USA customers... so far we have provided this service to a few in the states but they have have had a downpipe manufactured within our guidelines locally.
FYI - 335D Graphs
Injection relative to backpressure in mbar
Injection relative to Exhaust Gas Temp in degree C.