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Well ghostwalker, I may be trying this out.
Good thread but whats missing is the real world testing, at least from someone who doesn't have a product to sell.
I would still love to see some data, not necessarily showing FE improvements, but showing that there is meaningful backpressure in an exhaust system at light loads and normal driving RPM ranges. With that demonstrated, some improvement in FE could be found by reducing backpressure without fiddling with other aspects of the exhaust tune. Perhaps then it's still only something for a master ecomodder looking to get every last little bit out of their mill.
I have a V6 with a 3-2-1, and the 2-1 is *very* restrictive, with a U-bend looping back on itself, and a tiny outlet into the main cat. It makes the engine much quieter. I still don't understand how and why this has been designed like this, since I imagine at low RPM it's sending exhaust back into the cylinders. I'd love some explanation on that.
On this Nissan VQ engine, an well known aftermarket "y-pipe" mod shows improvement in before and after dyno charts as low as the dyno pull will go, usually 1750rpm. Most show "area under the graph" improvement from 2200 upwards, topping out at about 7-10% improvement, which shows this damn thing really chokes the exhaust flow right down low. Now dyno runs are at WOT of course... so is it still unrealistic in this circumstances to see improvement in normal driving?
Can any of the more knowledgeable folk here say that reducing exhaust restriction, without changing tuned lengths and diameters really isn't worth while? If I get some low end torque in a automatic, there's a also little to be gained in avoiding kickdown?
This mod is good for ~10% power on an otherwise stock engine, is cheap, affects the whole power band ... it's going to be fun bang for buck at worst, and at best is a mod that might get a whisker of FE back.
I will be getting a before and after dyno done. I'll consider doing FE testing and post a proper thread.
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