A8 1.2TDI is alive registered and running lean

[oldtamiyaphile]

Originally Posted by UFO

Diesel engines do not regulate AFR, there is no throttle. As long as the turbo supplies enough air, the AFR will be lean under all load conditions.

Although the mechanism differs from petrol, diesels main party trick is changing AFR to suit load conditions. A diesel can run 100:1 at idle and 14:1 under load. If diesels always ran lean, they wouldn't make smoke under heavy load - even the latest BMW will put out visible smoke if driven hard.

[oldtamiyaphile]

Originally Posted by elhigh

That's an awful lot of mass to tow around with a 1.2. I reckon once it gets up to speed it isn't too bad though. God knows the TDI engines make good torque for their size, if you have the time I don't doubt it'll accelerate up to highway speed eventually.

Renault is one of the first in modern times to go to a really small engine for a really big car, in the Trafic, you get 1.6 litres to move a 1700kg van. It still does 0-62 in 10.8 seconds (still faster than some hatchbacks), and is rated for a total train weight of 5 tons

Looking at Vekke's figures, his car has the same power for less weight and a better frontal area. I thought the first tank was a disappointment, but the second tank shows promise. I'd have hated all that work to have gone to waste. But it looks like a 'fast enough' car that will do 60mpg now

[UFO]

Originally Posted by oldtamiyaphile

Although the mechanism differs from petrol, diesels main party trick is changing AFR to suit load conditions. A diesel can run 100:1 at idle and 14:1 under load. If diesels always ran lean, they wouldn't make smoke under heavy load - even the latest BMW will put out visible smoke if driven hard.

Sure, I see plenty of overpowered diesel pickups that smoke like trains, but that's because they've chipped them to make more power by adding fuel. But in a factory setup, it's difficult to make them smoke because they are designed to be clean. Volkswagens are some of the cleanest around. When I get mine emissions tested (at load), it regularly turns less than 6% opacity. They are designed to run lean of stoichiometric.

[cRiPpLe_rOoStEr]

So, what are you considering to do in order to overcome the smoke issue?

[Vekke]

Its just a matter of ecu tuning in my case. ecu tries to get more boost even its not capaple to deliver so it injects more fuel. The Turbos vnt control is not fully in use due to program is for smaller turbo whichs boost peaked a lot so its not closing totally the vanes in current program.

There are 3 "programs" in depending on my gas pedal position.
0-70% is at the moment very efficient but no boost is the 2 liter fuel consumption range. 70-90% is efficient acceleration with 0.8-1 bar boost
90-100% is flat out acceleration (all in) with 1.5-1.7 bar boost

at the moment the car goes on to that 90-100% range on bigger uphills and gives smoke.

[kafer65]

If I remember right from my mark 4 VW days the 1749 was an up sized turbo for those 1.9 liter TDI and even in factory form they would go just fine with 90 hp and 177 Ft/Lbs.

[elhigh]

Got the vehicle weight down to under 1500k - WOW. That's a lot of dieting!

I don't think I had accurate numbers to look at for the 1.2's output. If it's going as well as all that, I think the numbers I saw were either old or just flat wrong.

[kafer65]

I let the large size of that car distract me from the fact that it is an aluminum monocoque platform. Its very light for its size! There is even a picture of one with polished aluminum--no paint.

[Vekke]

Today tested acceration and result was 10.5 seconds average for 60-120 km/h acceleration.

Weighted the car in corner weigth scales and resuts were:
Front Left....Front Right
420............430kg

Rear Left......Rear Right
300 kg..........320kg (12V battery is in this corner.)

Total 1470 kg with full tank in this measurement.

[UFO]

That's not bad for a big car. 3240 US pounds for the metric-challenged.