Volkswagen under investigation over illegal software that masks pollution

**Ryeman** · 18-01-2017, 08:18 PM

After the DPF - before the catalyst
What is SCR? | Diesel Technology Forum

**Greg Roles** · 19-01-2017, 06:03 AM

Yeak OK, perhaps with SCR systems they can do away with inlet EGR, but also reduce or displace the big NOX cats in the DPF itself, which became individual cannisters in the MK7. I admit I'm not that really into SCR technology as I don't have one, nor do I expect to anytime soon. They have better power figures in the latest engines, but the emission control is becoming so complex, and they often play up at some point...well I'll be sticking with the "old" MK6 technology I have for the mid term at least. I can control, rebuild and fix what I have now!

**Ryeman** · 19-01-2017, 06:46 AM

^^^^ yep
Have a REAL fix instead instead of a stitch up!
(at least the cleaner burning SCR engines put less particulates into the DPF. As long as they don't reduce it's capacity that is)

**Ryeman** · 19-01-2017, 03:54 PM

He appears in an orange jumpsuit and chains.......bit of a comedown http://goautomedia.cdn.on.net/gan_pr..._038.pdf#page7

Wouldn't happen to an American banker though

**gldgti** · 19-01-2017, 04:11 PM

For those of you still wondering about peak torque and the rpm figure in that graph - if you've ever been involved with cars and dyno's, you will know that the start of the run is quite variable -

The operator can literally be sitting in the car, simultaneously loading up the dyno and feathering the accelerator, gradually adding more load until a point at which he decides the load being provided by the dyno is enough to fully load the engine but still allow it to accelerate, at which point full accelerator is applied and hopefully, the engine revs up through the full rev range. Operators often seem to err on the 'low load' side of things so as not to simulate accelerating your car whilst towing a 3T trailer up a hill.

Anyway, with a turbo diesel, that peak torque figure is at about peak VE for the engine, + max boost. You can make max boost at those kinds of RPM, but you really need to have been trying to make max boost from just off idle to get it - i/e, if you are cruising at no load at 1500rpm and you go to full throttle, you wont get max boost at 1750rpm - it will still be building (lag) - that is unless you are actually towing that 3T trailer up a hill).

All of the above to say that dyno runs for turbo cars (especially diesels) are easy to introduce variance in at low rpm, and you need to see a plot of the exhaust O2 level as well as the manifold boost pressure if you want to actually compare runs - otherwise you are only getting half the story.

TL/DR
> You gotta also have a graph of boost pressure and exhaust O2 to compare the dyno runs.

**Ryeman** · 19-01-2017, 04:35 PM

It's the same tester(?) and same car (before&after), so you'd hope as professionals they would know what they are doing.
We await VW's version

**Ozsko** · 19-01-2017, 07:06 PM

I would want to see EGT's as well, in fact more so than anything else. Dynos especially water brakes have real issues, we used to boil the water in the one I worked with and that alone stuffs any engine readings. If the car has run multiple pulls then it depends on what sort of dyno it is.