'Petrol efficiency experiment; an increase of 20%' blog discussion

Tojo_Ralph

pault123 wrote: »

VW, Audi and Skoda Estates are commonly fitted with the superb 1.9 TDI diesel turbo injection engine, some common rail, other pumpe duse (faster and more efficicient) its easy to achieve 50-60mpg :beer:

Having driven the A4 Avant 1.9 TDI, the A4 2.0 TDI and the Passat 1.9 TDI Passat, I would never dare to claim that you could ever get 50-60 mpg out of any of them easily, even pootling along a motorway it would be hard earned.

harryhound

pault123 wrote: »

VW, Audi and Skoda Estates are commonly fitted with the superb 1.9 TDI diesel turbo injection engine, some common rail, other pumpe duse (faster and more efficient) its easy to achieve 50-60mpg :beer:

Can you explain these technologies in laymans' terms ?

Did GM take over Saab to get its hands on European diesel technology? (In USA they don't like driving what they see as "trucks".)

pault123

Tojo_Ralph wrote: »

Having driven the A4 Avant 1.9 TDI, the A4 2.0 TDI and the Passat 1.9 TDI Passat, I would never dare to claim that you could ever get 50-60 mpg out of any of them easily, even pootling along a motorway it would be hard earned.

I've been in many private cabs with the TDI engine and cringe when I see the driver taking the revs above 3000-3500 on the shifts and not using the superb pull the low torque range gives.

They stay in 1st gear far too long and don't flow when they shift gears.

They accelerate up to traffic lights and slam the brakes on. The worst waste of fuel leaving the car in 3rd gear when doing 35mph - 50 mph on duel carriageways, 4th or even 5th would be best here. I've never seen their mpg readout exceed 45.

I have the pumpe duse varient of the engine, 130 bhp with 6 speed gearbox - so its certainly not one of the slow versions of this engine (vs the 90bph, 110, and 115)

I don't know how hard you drove these cars- or how many of the above cab driver traits you follow? But when reading the road well ahead and not needlessly revving 50mpg comes easy. Once a constant speed is achieved on dual carriageway or motorway it climbs to 60 without a lot of effort.

pault123

harryhound wrote: »

Can you explain these technologies in laymans' terms ?

Did GM take over Saab to get its hands on European diesel technology? (In USA they don't like driving what they see as "trucks".)

Jeremy explains well >>>

"Now, among its vast range of engines there was a diesel rejoicing in the name of TDI 110, the 110 referring to horsepower. That's no more because it's been replaced by this, the 1.9-litre TDI PD 115; same price, five more bhp and the PD standing for Pumpe-Düse which, loosely translated from the German, means Unit Injector.

Because I've been economic with words thus far, I can now explain a little about what this means. So standby for an update of the latest in diesel technology and I'll try and slip in some jokes in an attempt to hold your attention.

PD is an advanced fuel injection system which can operate at much higher pressure - up to 30,000psi (10,000 more than contemporary 'common rail' systems). The injector and pump are now combined into one camshaft-driven unit for each of the four cylinders. Previously there was one pump feeding the four injectors.

This means lower emissions, more horsepower, more torque (up from 193 to 210lb ft at the same 1,900rpm), improved performance (0-62mph to 10.7secs from 11.3) with no penalty on fuel consumption at 53.3mpg (combined). In addition, the PD costs no more (from £17,465) and gains ASR traction control as standard."


explained here

http://www.topgear.com/drives/E8/A4/roadtests/02/01.html

harryhound

:oI've not even got a common rail.

So to sum up the CR technology allowed all the cylinders get a uniform injection service, thus reducing the juddering.

Now those clever German engineers have worked how to do the job with individual electronically controlled pumps thus getting 3 times the pressure.
This squirt gets the engine operating faster, with more power and increases its ability to accelerate?.

Harry

pault123

acceleration, better fuel economy, less startup clatter when cold, an awesome amount of "pull" at low revs and the ability to overtake without dropping down a gear

Tojo_Ralph

pault123 wrote: »

I don't know how hard you drove these cars- or how many of the above cab driver traits you follow? But when reading the road well ahead and not needlessly revving 50mpg comes easy. Once a constant speed is achieved on dual carriageway or motorway it climbs to 60 without a lot of effort.

My comment was naturally based on driving all of the cars in Eco Driver mode. ..... And whilst 50 MPG was achievable, it never ever came easy on non Motorway journeys.

Anyway, just for fun I drove home tonight in Ultra Eco mode, I got all the breaks with the traffic, used no lights accept the always on side lights, no air con, no music (never again) and making sure I kept the onboard eco recommended gear change thingy happy by trying to change gear in the 1400 rpm to 1800 rpm range and the onboard computer told me I was getting the following figures from the 2.0TDI engine, which from experience reflects the actual consumption... 50.4mpg... Ave Speed 34 mph... Time 20 mins... 11.5 miles.

bigpat

redrabbit29 wrote: »

I don't think it is the same - someone correct me if I'm wrong.

Coasting - keep foot on clutch. No torque on engine and no labour for it.

Neutral - Still has to run the engine. Someone even said that at a traffic light it's better to be in first than neutral as it's less work for the engine.

So in that sense coasting is better than neutral - plus it's probably safer too.

Hmmm....the bit that confuses me is when you say "still has to run the engine" in neutral. Isn't that the same as when you just keep the clutch pressed? The engine is still running? Are you saying that the engine runs LESS (somehow) when you hold the clutch down to coast, rather than coasting in neutral?

You could be right I suppose, but I always thought that pressing the clutch was temporarily disengaging the gear and was therefore the same as putting it in neutral except - I suspect - that you'd wear out your clutch doing this.

Does anyone else know about this?

pault123

bigpat wrote: »

Hmmm....the bit that confuses me is when you say "still has to run the engine" in neutral. Isn't that the same as when you just keep the clutch pressed? The engine is still running? Are you saying that the engine runs LESS (somehow) when you hold the clutch down to coast, rather than coasting in neutral?

You could be right I suppose, but I always thought that pressing the clutch was temporarily disengaging the gear and was therefore the same as putting it in neutral except - I suspect - that you'd wear out your clutch doing this.

Does anyone else know about this?

you share my thoughts bigpat!

pault123

Tojo_Ralph wrote: »

My comment was naturally based on driving all of the cars in Eco Driver mode. ..... And whilst 50 MPG was achievable, it never ever came easy on non Motorway journeys.

Anyway, just for fun I drove home tonight in Ultra Eco mode, I got all the breaks with the traffic, used no lights accept the always on side lights, no air con, no music (never again) and making sure I kept the onboard eco recommended gear change thingy happy by trying to change gear in the 1400 rpm to 1800 rpm range and the onboard computer told me I was getting the following figures from the 2.0TDI engine, which from experience reflects the actual consumption... 50.4mpg... Ave Speed 34 mph... Time 20 mins... 11.5 miles.

Lights and radio i've found to have no measurable effect whatsoever. Climatronic Aircon even when on full Low cool setting only knocks 1-2 mpg off the total.

5-15 mpg on the other hand are easily knocked off with a bad shifting technique and a lead weighted foot.

I'd say your gear change made the biggest difference in tonights ultra eco drive

A quest should you choose to accept it on tomorrows commute - radio, aircon and headlights ON but keep the "gear change thingy" happy and let me know what mpg you average?