Technical guides Diesel & Petrol

[Anddenton]

Yawn!

[dieselV6]

Yawn!

Past your bedtime, perhaps? At least I am trying to make the best out of new Octy 3, we now know it has full sized spare and the option codes for it, and that in the diesel vRS guise will be much faster than current diesel Superb. What have you contributed?

[Kiwibacon]

Yes I can.

The 3.0tdi v6 has 50% more cylinders and hence 50% more internal friction than a 2.0tdi 4 cyl. It also has exhaust manifolds which lose more heat and velocity before they can feed the turbo.

Both are efficiency killers at part load. At full load the efficiency might be comparable, but you are burning ~50% more fuel, so economy has gone out the window.

I also have a pd 2.0tdi scout. No DPF lights or forced regens yet, VCDS shows 9% full DPF. My average is right with Addentons fuelly results.

[dieselV6]

Both are efficiency killers at part load.

BSFC maps for 2.0CR and 3.0CR please or it did not happen. I will also gladly accept 1.9TDI IP and 2.5TDI IP maps instead.

Basically, you only present graphs and numbers when it is convenient for you, I presented numbers for 2 comparable engines and real life usage over tens of thousands of miles each. If anything, for the numbers I posted odds were stacked in favour of 1,9TDI as it was in a lighter car, and 2.5TDI is known to be less efficient over most of rpm range.

Plus from the single map you posted, you can very clearly see that at 4k rpm 75% part load is more efficient than full load, contradicting statement you just made. This is because of pumping loss (even with free flowing exhaust) and limited flame front speed. .

Edited 19 January, 2013 by dieselV6

[k.young]

Would the two of you just meet up and have a game of chess to see who is the smartest !!!!!

[Anddenton]

Past your bedtime, perhaps? At least I am trying to make the best out of new Octy 3, we now know it has full sized spare and the option codes for it, and that in the diesel vRS guise will be much faster than current diesel Superb. What have you contributed?

Yep.

Oh and also I come on here to find out what the Octy 3 might be like. All I have learnt so far is that it isn't as good as a mk1 superb for blasting at stupid speeds around German Autobahns. So what.

[Kiwibacon]

Well pardon me for not providing graphs that aren't publicly available for engines which aren't available in the cars being discussed.

Yes 3/4 load is more efficient than full load at 4000rpm. By a whole 2% (~220g vs 225g).

I'd love to know how you can attribute this to pumping loss when the engine is turning the same rpm. The difference in boost and airflow between 75% load and 100% load is minor and Turbochargers are more efficient when fed exhaust at higher temperatures.

It is the longer injection time and earlier start of injection which is reducing the efficiency.

You should be aware, that BSFC plot is for a 140hp cr engine. Not a 170hp and not the new 150/184hp engines either. Is is however going to be a lot closer than any 1.9 or 2.5 data.

[dieselV6]

The difference in boost between 75% and 100% load at 4k rpm is not minor, in fact looking at an old 2.5TDIV6 boost map from the actual ECU of my Superb's, it is a difference between 1.62bar and 2.28bar, a whopping 29%. It would make no sense to keep pressure constant as it takes extra effort and would require injecting vast quantities of exhaust via EGR to prevent high temps and NOx emissions.

Also, I am trying to make a point that at high rpm and close to full load for a 2l engine, a 30%-50% bigger engine is a bit more effcient. As is evident even from your map of a relatively unstressed 140bhp engine. More stressed engines (higher boost pressure) will generally show more impact of pumping loss. Turbocharger does not generate power, it still saps power from the engine, just a bit less than a supercharger would thanks to exhaust gas energy recovery.

You seem to be bent on proving that 2.0CR is more effcient than 2.5TDIV6, both close to full load. I do not need convincing on that, 2.5TDIV6 was one of less effcient engines in the VW lineup. But please stop denying actual fuel economy numbers that I got on the road over thousands of miles because you expect a different result.

[dieselV6]

Oh and also I come on here to find out what the Octy 3 might be like. All I have learnt so far is that it isn't as good as a mk1 superb for blasting at stupid speeds around German Autobahns. So what.

So you did not learn that there is a full size spare option (I provided option codes for that), that Octavia vRS diesel will have 184bhp while vRS petrol will have 220bhp (I provided that info again), and that it will be available in May somewhere in Europe (me again). I provided this information for your benefit, as well as pointed out that Skoda's PR is hoodwinking most customers into accepting worse rear suspension than it promised, and that 2.0CR is the engine to take any day over the 1.6CR.

The efficiency/power discussion keeps going only because Kiwibacon is hell bent on denying my long term fuel consumption numbers at high speeds, and that a bigger engine is better at 2/3rd power than a small engine at full power.

Edited 19 January, 2013 by dieselV6

[Anddenton]

So you did not learn that there is a full size spare option (I provided option codes for that), that Octavia vRS diesel will have 184bhp while vRS petrol will have 220bhp (I provided that info again), and that it will be available in May somewhere in Europe (me again). I provided this information for your benefit, as well as pointed out that Skoda's PR is hoodwinking most customers into accepting worse rear suspension than it promised, and that 2.0CR is the engine to take any day over the 1.6CR.

Sorry, missed most of that in amongst the detail on how fast you can travel across Germany with how many fuel stops.

[dieselV6]

Thank Kiwibacon for that. I stated originally that Octavia Mk3 has unneccessarily crippled fuel tank that might fit most people but punishes long distance/high speed drivers, you have to watch out which rear suspension you're getting, and that 1.6CR engine is worse than 1.9TDI or 2.0CR for that matter, plus SUK claimed space saver spare only was possible. In return, what we got is attempts to deny all these points, to which I responded with facts and figures.

Bottom line is, Octavia Mk3 looks set to be a good cruising car in top diesel versions (vRS and 4x4), except unneccessarily shortened range.

Edited 19 January, 2013 by dieselV6

[k.young]

Thank Kiwibacon for that. I stated originally that Octavia Mk3 has unneccessarily crippled fuel tank that might fit most people but punishes long distance/high speed drivers, you have to watch out which rear suspension you're getting, and that 1.6CR engine is worse than 1.9TDI or 2.0CR for that matter, plus SUK claimed also space saver spare only was possible. In return, what we got is attempts to deny all these points, to which I responded with facts and figures.

Bottom line is, Octavia Mk3 looks set to be a good cruising car, except unneccessarily shortened range.

I still maintain that the 2.0CR will have longer range than it's predecessor but I don't have any science to prove it, just common sense.

To safely cruise at 130-140mph for 2 hours+ I think you should start off with a car that is capable of maybe 160-170mph to start with and that is just a personal opinion not the basis for my next thesis!

Tapatalk'd from my HTC SXE Beats

[dieselV6]

Agreed, but 160mph (limited to 155) in a diesel means cars in Audi range. These have not so durable suspension, you have to either choose underbody protection or longer gearbox but never both, are a lot more complicated and prone to failure, no full size spares until A8, and in high power versions come with auto boxes. Plus they are overpriced and stick out as thieves magnet on the road.

Mk3 Octavia looks to be more durable, less expensive and looks like the vRS will still do the job that Mk1 Superb did so why not add 10kg to kerb weight and fit 60l fuel tank instead. Mk2 Superb is too slow with 170bhp diesel.

Edited 19 January, 2013 by dieselV6

[k.young]

Would the Superb 170CR remapped to 200-210bhp not fulfill your needs. When I remapped my PD140 to circa.185bhp it increased my topspeed by over 5mph but I suppose that really depends on the final gearing.

A remapped Superb with 200bhp and 320lbft would have to be good for 145mph, no??

[k.young]

What about a VW Phaeton 3.0tdi, I know it has complicated suspension and auto box but this car was made to be an Autobahn cruiser. Remap one of these with a de-limit and you have got yourself the ideal missile for your transcontinental trips.

[dieselV6]

Remapping 4-cyls and running them at around full power for hours at a time and for more than a few years, you have to factor the cost and hassle of head gasket job at some point down the line, though typically past 100k mile mark.

Phaeton is out exactly for reasons you described plus no underbody protection, otherwise yes, it is one of the best high speed cruisers around. There's currently a £7k off deal on the LWB version which is otherwise good. I do not mind paying a lot initially, but do not want a heap of running costs and constant trouble after 5-6 years ownership. Octavia Mk3 and Superb Mk2 fit my needs.

I need a car for all roads in Europe, not just autobahn. Skoda under VW started with exactly this spec for Mk1 Octy and Superb. It also made a good business for Skoda as it is popular in all countries alike, good roads or bad roads.

Mk3 Octy still almost fits the bill,closer than Mk2 Superb unless they put 184bhp stock in superb when Mk3 Octy comes out. If it's just the thimble fuel tank left on the annoyances list, I'll have to live with it. Let's see the long term pricing, though.

[k.young]

My 4 cylinder is remapped and gets regular 100mph+ for 2hrs although I would not be running it at 130mph. My head gasket has never had to be done and I am at 533,000kms.

Tapatalk'd from my HTC SXE Beats

[dieselV6]

At 130mph you use nearly double the 100mph run power, 100mph is comfort zone for the 2l-ish engines.

A lot of 1.9s after remap (on top of the ones after bodged TB/WB jobs) have a gasket problem down the line, though they were higher compression than current engines (19:1 compared to current 16ish:1). Anyway, why pay for a remap and extra for more expensive Mk2 Superb when Mk3 vRS Octy will do the job at stock power (and likely with better brakes).

There's also driver seating position to think about, Mk2 Superb is a lot less comfy for tall drivers than Mk2 Octy was, console bites in the leg and leg support is worse. I quietly hope Mk3 Octy will be more driver friendly than the Mk2 Superb. But I'll only check it when Octy 3 is at my local dealership.

Edited 19 January, 2013 by dieselV6

[k.young]

I think we are losing the foot rest on the throttle side.

Bummer.

Tapatalk'd from my HTC SXE Beats

[dieselV6]

Interestingly, ETKA lists 1 foot rest for LHD and 2 foot rests for RHD. Due to different layout, it is likely RHD will still have both, though possibly both too small.

[k.young]

This would make me very happy as I spend a lot of my day using cruise control.

[k.young]

It makes sense, the LH side is the gearbox side, probably creating footwell space issues.

[Kiwibacon]

Oh right.

We again have 2.5v6 tdi data presented as proof of what the 3.0tdi v6 would do. The 2.5tdi runs in a completely different emissions class and boost strategies have changed considerably since.

EGR is always off at full load. For many reasons which shouldn't need explained.

I have not denied any fuel economy numbers. Just the predicted ones based on a mythical 40% error.

I find it hilarious there is this much nay-saying over how unsuitable a car will be, based on assumptions made on prior models.

Lets go through your concerns

1. Car may not fit because you are quite tall. This is a very valid concern, but you will know as soon as you can test-drive one.

2. Car may not have enough internal space. Again you will know as soon as you can test drive one.

3. Cars range may not be sufficient. The data (which you don't believe) shows this won't be a problem. Within a few weeks of cars becoming available we will know for certain.

4. You don't like torsion beam rear suspension. So wait until the VRS and Scout models are out.

5. Car cannot take a full-size spare. I have no idea why you think this. All cars I have seen with a space-saver can fit the removed full-size wheel in the same hole. It is only cars with collapsible spare tyres which have smaller wheel-wells. All information points to it not being a problem.

6. Not enough power for high speed cruising. This is completely unfounded.

7. Higher fuel consumption than your 2.5tdi v6. This is impossible.

[Herschel]

What about a nearly new Touareg?

245ps 3L TDi

85L fuel tank

40mpg (at normal speeds)

£34k for a 1 year old car.

Edited 19 January, 2013 by Herschel

[k.young]

Q5