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Normally, even stock 4.8 N62s have about 230-235 whp or like 330-335 bhp instead of 350 claimed bhp. I saw a dyno chart with 225 whp AFTER remapping. On the same dyno my 4.6is with Hartge headers cats delete and "sporty" resonators showed 242 whp with 95-100 hp driveline loss but immense 500 nm (368 lb fts) of tourque only at 2700 rpm, the N62 4.8 could acchieve only 440 nm or 325 lb ft.
In near future I'll put the cats back (because supercharged engine needs even more back pressure) and will do another measurement before supercharger installation.
Removal of resonator (or even both - muffler and resonator) on n/a engine will cost you a loss of another 20 whp, so the result will be a loud car wich sounds like 600 hp, having like 60-70 hp less, than manufacturers claim.
With very few back pressure you flush the cylinders with the fuel-gas mixture, so the burning process is wrong and also your cats won't last long due to very wet AND air-rich exhaust gases, which will burn in exhaust and not where they supposed to burn. The lambda sensors first will read wrong parameter and then also die, because of overheating.
If you considering of removing the parts of exhaust you have to correct the lambda values AND shift the lambda sensors further from the engine (but still it will be just a give a ball park action with very iffy result).
So IMO if you're considering a exhaust tuning the only appropriate way is to play with the muffler.
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12-14-2012, 04:31 AM
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