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      12-05-2012, 02:59 PM   #9
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Drives: 2011 BMW 335d
Join Date: Sep 2010
Location: Murland

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Originally Posted by anielsen71 View Post
I have several sources saying it DOES have an effect. Promotec from where I bought my bigger IC has done some testing on it. Without DPF, bigger IC and a remap the 330d delivers 300hp/700+nm. With DPF, bigger IC and remap they typically delivers 260-280hp and 600-620nm.
My own has been dynoed several times to 265-270hp and 615-620nm and I still have the DPF installed.
Ecotune who has the DPF removal pipe has the same experience.
You DON'T get any gain by only removing the DPF. You need to do a remap.
If your friend did not do a remap I can understand why he did'nt get any more power.
Okay to be clear, you have not removed your DPF and comparied the results (before and after) on the exact same dyno, under similar atmospheric conditions at a shop independent of the tuner? Right?

I do not doubt what some tuner is telling you about the gains to be had when removing the DPF in conjunction with a tune they sell, I just doubt removing it improves HP/TRQ (40hp/100 torques!) whether a car has a tune or not.

Think about it,,, what your shop is saying is, if your car has a tune and a larger IC that by simply removing the DPF your car will gain 40hp and 100 ft lbs of torque! This would imply that the DPF IS a restriction regardless of whether a car has a tune and as such I would expect to see SOME improvement in a car without a tune.

Arguably increasing the down pipe diameter can influence horsepower output in particular when engine temps are running hotter and there is more back pressure, but frankly speaking I do not think the stock downpipe/DPF will have a significant restriction effect on airflow(because that's what we are really talking about here) when running a tune that only generates an additional +/- 60hp - 75hp. I believe engine output would need to increase substantially in order to exceed the flow capacity of the stock downpipe in order to see any significant gains from removing the DPF, which seems to be supported by the other member's findings.

Call me a cynic until proven otherwise - and I am not talking about showing me some tuner's dyno graph.

Last edited by cssnms; 12-05-2012 at 03:06 PM.