AUDI Fined 800 million Euros by German prosecutors, for 6 and 8 cylinder diesels

[Zak33]

Not so much any more, to try and avoid nox emissions the compression ratio has dropped a lot, the mjet diesel engine in my last car was 16.8:1 which is well down on old school diesels which were in the 20's. My current turbo petrol engine is about 9.8:1 but there is a big difference thanks to the higher red line of the petrol engine which for me makes the car nicer to drive.

But that compares to the old 3.0v6 petrol engine in my kit car, which despite only a 9.0:1 compression ratio feels like it can tow small moons. The gear selector failed once, so I manually stuck the car in 3rd and happily drive it around like that for the day just using the clutch

true story...but the new "lower" 16 to 17 :1 ratio are because modern turbo's boost higher and the rev requirements of the engines needed pushing up a tad to increase BHP figures.

Still... an older 3litre V6 petrol is always gonna feel awesome. They often had lower lift cams, and even 12 valves!!! instead of 24.... and were designed for grunt... But put an old one like that in a newer car and it will struggle. New cars are HEAVY and the fuel consumption will be horrific.

[DanceswithUnix]

Still... an older 3litre V6 petrol is always gonna feel awesome. They often had lower lift cams, and even 12 valves!!! instead of 24.... and were designed for grunt... But put an old one like that in a newer car and it will struggle. New cars are HEAVY and the fuel consumption will be horrific.

The wife's car has the last version of the same basic Busso engine, so 3.2l with sequential rather than bulk fuel injection and 24 rather than 12 valves. It copes very nicely indeed with 1500kg of car to lug around. It does struggle to get 30mpg though, but then if you keep a modern engine on boost they don't really fare much better. The whole point of a modern turbo is to get economy by not using it (boo! ). eg, my current 1.4l engined car does 50mpg on the motorway in economy mode where the turbo doesn't kick in until 2100rpm. In reality, I get about 30mpg out of it else I feel like I'm going to die of boredom driving. Had I bought the 1.7 turbo engined version of my car I'm sure I would get exactly the same real world economy as the wife's V6. I know which one I would rather drive (and listen to for that matter).

[watercooled]

WRT my comment I wasn't very specific what I was on about; rather than the nature of turbocharged engines, I meant more outlier like shown here (pinched from a forum but I couldn't find the original post):


Note the curve of the 163TDi, and remember that's in Nm not lbf⋅ft!

It was an very non-specific comment I made about a fairly specific issue, but yeah I can imagine (without any proof, mind) that the 'optimal' RPM range for the test would be way down in the torque band before boost is really able to make a difference. And that's fine if you're cruising in top gear, not so much when you're driving around town, and I imagine being overly-aggressive with up-shifting would be... annoying.

I drive a turbo petrol myself and it did take me a little while to adapt to the torque band - it's not so much the turbo lag that's evident, rather the fairly steep (vs NA petrol) torque band around about 1500rpm. I really quite enjoy driving it now!

[DanceswithUnix]

Note the curve of the 163TDi, and remember that's in Nm not lbf⋅ft!

That just looks, wrong.
That engine appears to have less power than the 140, though I can't think of a fault that would give a graph like that.

[watercooled]

Hmm yeah something does look wrong, perhaps it's a fault with the ECU or air intake? I'd say ignition timing too were it a petrol. Err, maybe injectors, bad fuel, etc?

And yeah the curve around and above the peak looks almost identical to the 140 engine.

For some reason that graph just stuck in my mind after I saw it a while ago, had to find it again with Google image search but it seemed to have disappeared from the post.

Edit: Found the original post: https://talkford.com/community/topic...ke-the-plague/

[philehidiot]

Often these things will just default to a limp mode map (although this doesn't really look like I'd expect) in the case of a sensor failure or weird fuel or something. I wonder if that's what's happening there?

[kalniel]

That just looks, wrong.
That engine appears to have less power than the 140, though I can't think of a fault that would give a graph like that.

Looks to have more power to me - fractionally less peak torque, but power is torque x revs and what torque the 163 has is sustained for higher revs. Eg at 4k revs the 163 looks to have about 285nm, while the 140 has more like 260nm. Ditto looking at revs when they cross the 300nm mark - the 163 is higher.

Lovely smooth curve though, almost like a NA engine

[badass]

Lovely smooth curve though, almost like a NA engine

I know you're being facetious but come on!

Torque more than doubling in less than 1000 RPM on all engines - that's the polar opposite of a nice smooth NA torque curve!

EDIT: However absolutely right on the 163 clearly being more powerful. It simply holds its torque for longer.

[watercooled]

They both look about the same to me, capping out at ~225Nm torque at ~4500rpm? Ignore the modified blue line.

They also both peak at just over 350Nm at roughly the same rpm too.

[badass]

They both look about the same to me, capping out at ~225Nm torque at ~4500rpm? Ignore the modified blue line.

They also both peak at just over 350Nm at roughly the same rpm too.

Try plotting the power on a graph of them both. You'll see

[watercooled]

They're both available at superchips. 154 vs 163bhp peak. And the power graph is on the same scale helpfully.

http://www.superchips.co.uk/curves/2...CI%20163PS.pdf
http://www.superchips.co.uk/curves/2...deo2.0TDCi.pdf

The power from the 140 engine is higher right until you get above about 3000rpm, then fractionally higher for the more powerful engine from there.

[DanceswithUnix]

The power from the 140 engine is higher right until you get above about 3000rpm, then fractionally higher for the more powerful engine from there.

That's about what I was expecting from the torque graphs, the 163 engine is better over 3500rpm which with a piddly 9bhp measured difference in those plots which isn't worth the cripplingly bad low rpm torque.

[badass]

Random google image for the 3.0TDI from an Audi A6 (c7)presumably with one of the engines mentioned shows:

Torque at 1000 RPM being significantly over 200 lb ft!

The peak is around 370 LB ft at 1400 RPM :-S held till about 3000 RPM where it drops off but not fast enough for the power to stop increasing. Peak power of 240 PS looks to be around 4000 RPM

It looks like the engine is usable from idle (albeit presumably sluggish*) so they could have had the efficiency setting short shift with the expectation that the engine would be incredibly unresponsive albeit efficient.


* Dyno graphs always show peak torque on turbocharged vehicles lower than you think and feel from driving the cars. In the real world, revs are rising from acceleration as the boost rises so full boost isn't hit as early on a dyno.
Also, turbo lag at low revs on all diesels I have ever driven, no matter how modern is dire. Literally a 2 second delay from pressing the throttle before meaningful boost is reached at 1500-1800 RPM on any moderately powerful 4 cylinder engine. Compared to about 1/2 second at 1600 RPM on my 200ps 2.0 TFSI

[watercooled]

Just to understand what you mean - you're saying peak torque when driving is in fact higher than generally shown on dyno, due to e.g. turbo lag? (just for clarification, not disagreeing)

WRT turbo lag there are two real factors at play causing what is perceived as lag, spooling lag and the low-rpm dip in torque due to backpressure, in turn due to lack of airflow through the engine. Many of the modern small, turbocharged engines have fairly small spooling lag due to small, low-inertia turbos, but also that fairly steep low-down torque curve both due to back-pressure and due to the engine being smaller than an equivalently-powered NA engine, and down that low the turbo won't be doing much to compensate.

In addition, I've noticed in mine, there seems to be some sort of throttle lag, where there's I'd say a few hundred ms delay between moving the throttle and getting any response. Apparently it can be tuned out and isn't present on the performance versions of the same car, so presumably some sort of input smoothing for efficiency?

[DanceswithUnix]

In addition, I've noticed in mine, there seems to be some sort of throttle lag, where there's I'd say a few hundred ms delay between moving the throttle and getting any response. Apparently it can be tuned out and isn't present on the performance versions of the same car, so presumably some sort of input smoothing for efficiency?

Yeah, that was pretty bad in the generation before turbos took off, say 20 years ago. I guess playing with turbo boost is a far better way of getting economy figures than tricks where you ignore the accelerator so I haven't driven a modern car where it is noticeable. Thankfully Alfa never implement things like that, or lie in the trip computer about the economy as their target market isn't buying for economy

[watercooled]

I'd say it's about 100-200ms on mine; it's definitely noticeable and took some getting used to, especially when trying to rev-match for a downshift.

Interestingly, something else related to the throttle I've noticed is how the engine seems to 'hold' revs to match for a smooth upshift, if you take your time about it. E.g. shifting up it will hold the revs at say 1500 with the clutch down rather than dropping back down to idle. Apparently it all comes under the heading of throttle damping?

Edit: I've also noticed the delay on lifting off e.g. when changing gears - if I'm accelerating e.g. on a slip road and I'm too quick with the clutch, revs will blip momentarily even though the throttle is all the way out.