Skeptical of "blade" exaust tip FE / emissions claims

[diesel_john]

spring loaded flapper

Oh, you mean like this one on my F250.

The jury is still out on any MPG improvement.

[ankit]

Originally Posted by diesel_john

spring loaded flapper

Oh, you mean like this one on my F250.

Could you tell us your results with this mod?

[Cd]

Originally Posted by hondaworkshop

Howdy neighbors - bastrop/austin here

Keepin' Austin wierd ? I'm doing my part.

[tasdrouille]

Originally Posted by diesel_john

spring loaded flapper

Oh, you mean like this one on my F250.

Exactly, but with a one inch or so hole in it and a spring tuned to let the flapper gradually open from 3000 or so rpm.

My bet with this thing is to affect the flow during valve overlap. If there is more restriction in the exhaust, hopefully more of the gasses with stay in the chamber.

[dremd]

Originally Posted by jpgmtech

On my diesel I can pick up almost 10% highway economy by opening the VVT right up for cruising over and above the factory settings.

How did you achieve this? Pull the vacuum line? I'm interested in testing/ using this myself.

[jpgmtech]

Originally Posted by dremd

How did you achieve this? Pull the vacuum line? I'm interested in testing/ using this myself.

The D-max has a fully electronic controlled VVT. I did this in software. Does the VW TDI have a VVT turbo? And if so, how is it controlled?

[dremd]

The MKIV+ TDI (99.5 and newer) do have VVT Turbo's.

They are controlled in software. Basically the ECU tells the N75 (vacuum switching valve) to open/ close and the vacuum actuator moves the vanes.

I don't know of an easy way to do this in software, but I'd like to give it a shot by manually actuating it.

The chip tuners can probably do this, and probably do . . . Most people claim about 5~10% increase in FE, I'll bet that this is one place that they find that extra economy.

[tasdrouille]

dremd, I would look more deeply into the electric bleed mod performed on the the ALH, it might be akin to this mod. Chances are you can achieve what you want, to some extend, with just a resistance.

[Duffman]

Originally Posted by jpgmtech

Been there, tested that... at least in principle. Less exhaust backpressure is almost always better, with the exception of very specific circumstances, i.e. modifying the sound pressure wave tuning of the exhaust to optimize efficiency at a specific RPM. This is assuming the vehicle has equal-length headers too... and the tuner has an understanding of Helmholtz resonators.

Typically though adding backpressure effectively "throttles" the exhaust. Why not just throttle the intake, like we always do???

BTW, on a variable-vane turbocharged diesel, the vanes act as an exhaust restriction at higher vane angles. On my diesel I can pick up almost 10% highway economy by opening the VVT right up for cruising over and above the factory settings. The factory settings are there to intentionally create some backpressure for the EGR as well as making the turbo spool much quicker.

As for this "fuel economy" device - smoke and mirrors....

So does opening up the VVT result in less boost then or more?

[tasdrouille]

Who's got a dual exhaust on his N/A daily driver and can keep it below 3000 rpm and light/mid loads most of the time?

Could you please plug one of the ends real good and drive for a while like that? Then report back with results on low end torque (seat of the pants) and FE.

Thanks