200TFSI vs 170TDI - Power Curve Calculations Complete

[southpaw66]

I've created a graph to show how the 200PS TFSI and 170 TDI distribute their different power and torque curves to actual road speeds and gear selections.

[URL="http://i134.photobucket.com/albums/q100/vaststorm/power_curves_tfsi_tdi.jpg"][/URL]


You'll see that the TDI has more power in gears 1-3 upto 4000 rpm and about equal in 5-6 (dropping off a little a higher speeds). TFSI gains advantage staying in gear longer and using the extra 30hp 4200-6200rpm.

For in-gear acceleration they should be about equal upto around 4000rpm.

TFSI only need 2nd gear to reach 60mph, TDI requires 3rd gear.

From this data the best shift points for maximum acceleration to top speed are;

TFSI (6200rpm)

2nd 36mph
3rd 58mph
4th 82mph
5th 110mph
6th 140mph



TDI (4200rpm)

2nd 23mph
3rd 41mph
4th 64mph
5th 93mph
6th 119mph


No question the TFSI is faster. The additional torque does give the TDI some good/comparable in gear figures but sustained acceleration will suffer due to more gear changes.

For everyday driving the two cars are quite similar and the fuel ecomony advantage (10-15mpg) of the TDI could be a good compromise to loss of top end. Which is my choice.


Thanks to Dave (h5djr) for Gearbox ratios.

 

[C_Audiboy]

Useful info there....... :thumbsup:

 

[h5djr]

Would the same be true if both cars are fitted with S-tronic as the gear changes are made so quickly and with no loss of power?

I can provide the ratios for the 02E (DSG) box if you would like them.

 

[FreddieS3]

Great work! Thanks...

 

[steve184]

Yeh interesting that - as according to audi figures - DSG takes .4 of a second off 0-60 time whereas on the petrol you only get there .2 of a second quicker - so DSG benefits the diesel much more than the petrol - mind you i guess thats cos on teh diesel you are saving time on two gear changes whereas the petrol you are only saving time on one.

 

[HeliChris]

Good data - Thanks Steve

In the real world the DSG advantage might be even greater. I did some performance tests on a TT 225 some time back using a datalogger. It showed a 1 second stall in the cars acceleration each time a gear change was made using the clutch. To get a respectable gear change time a crash change was required (good job it was not my car). Therefore the DSG fast swapping would actually yield more return than just .2 of a second per change, I suspect it's more like .5 to .6 per gear change assuming you use your clutch.

 

[southpaw66]

The comparison data shows how the power is mapped to wheel speed so it does follow that DSG would have the same curves with similar ratios. If you send me the DSG ratios I'll see if it maps the power any differently, but I suspect it looks like audi have been aiming for a similar performance (at least for normal driving).

 

[h5djr]

southpaw66 - I have copied and made pdfs for the 02E (DSG) gearbox and the 02Q-quattro gearbox.

Here are the links....

gearbox-02E - DSG

gearbox-02Q quattro

 

[southpaw66]

Cheers Dave. I'll put something together over the next few days depending on workload.

 

[southpaw66]

Managed to spend a few minutes this morning updating the figures with the new data from h5djr (thanks again Dave)

Here's the updates for DSG and Quattro

DSG



Quattro




Best Shift Points are

TFSI (6200rpm)

DSG
2nd 34mph
3rd 55mph
4th 80mph
5th 109mph
6th 139mph

Quattro
2nd 34mph
3rd 54mph
4th 77mph
5th 103mph
6th 132mph

Manual
2nd 36mph
3rd 58mph
4th 82mph
5th 110mph
6th 140mph

170TDI (4200rpm)

DSG
2nd 22mph
3rd 37mph
4th 59mph
5th 84mph
6th 113mph

Quattro
2nd 22mph
3rd 39mph
4th 61mph
5th 88mph
6th 112mph

Manual
2nd 23mph
3rd 41mph
4th 64mph
5th 93mph
6th 119mph

So DSG and Quattro are geared slightly shorter than the manual. This would be expected to overcome additional loses in the driveline, especially for the Quattro. It does not mean they will be naturally faster infact they may be slower in-gear, but the DSG has shorter shift times and the Quattro has better traction. Nevertheless, given the shorter gearing of the DSG and the 'instant' shifts I'd expect a bigger advantage 0-60mph.
This makes me wonder, do they achieve the 0-60 using launch control, therefore removing the initial delay so many of you talk about. How fast are they changing gears in the manual cars to achieve those 0-60 times (see HeliChris' comment about crashing gears)

You'll see on the DSG graph the TDI has a power advantage over the TFSI in the first 4 gears upto ~4000rpm rather than the usual 3 for other gearboxes.

DISCLAIMER: All these figures are based on data assumed to be correct from reputable sources, but as always it may not always reflect the exact build conditions of past, current or future models - not to mention errors and typos.

 

[mfspen]

Very useful and interesting plots.

Have you produced similar plots for the torque at the wheels for each engine, in each gear ?

In principle, it is the torque which governs acceleration, rather than power (Newton's 2nd Law, etc). The power would determine the maximum sustainable speed, for given mechanical and aerodynamic losses.

 

[HeliChris]

0-60 is an art, and a car killer. If it’s your car, I will suspect you will never get close to the manufactures claimed 0-60 figures, because most will fall part after a couple of good attempts.

Some tips, the manufacture is allowed to remove anything from the car that’s not fixed, so that mean carpet mats spare wheels, boot carpet etc, but not seats. Next fuel and oil level, fuel just enough for you performance tests, and oil on minimum, who cares about a bit of oil starvation. Tyre pressures dropped to around 8-10 psi are good, it’s a trade off between top end drag and launch grip, so you have to experiment. The tyres need to be warm, very warm, so some smoke drag car style is required, I have found three smaller smokes are better at warming than one big long smoke (personal experience). The must be the same size, but you should select the tyre with the most grip. The Launch this is where DSG comes into its own because it has a programme to do this, but if you have a clutch you need to side step it, i.e. let the move your foot to the side, not bring it up, also the revs need to be high enough not for the engine to bog, this can be very high in a 4wd car, and often lead to clutch failure. No clutch gear changes, as hard and fast as you can move the stick, the gearbox but won’t last long but who cares. Lastly when and where, you need a special tarmac high grip surface (like a drag strip) and perfect conditions.

If you fancy it than take your car to Drag Strip open day and have a go.

PS The driver need to weigh 75Kg

 

[southpaw66]

Torque is an instantaneous force applied to the object, whereas power is the work done (energy consumed) by the force in moving the object (WD=F.d)
Nevertheless Power and torque are related by a linear equation so the results are the same curves effectively 'rotated' on the plot, but the differences between TDI and TFSI are more obvious in lower gears. You will note TFSI still slightly better 5th and 6th Gears - so much for TDI's legendary better motorway overtaking (It's just they use less fuel doing it)

I've converted the Torque at the wheel to total available forward force for 225/40R18 wheels.

 

[mfspen]

Excellent, thanks.

It would interesting to see the same torque curves for TFSI vs TDI 140, since many have commented on the apparent better low-end pulling power of the TFSI (eg. when exiting a corner in 3rd gear at low revs).

 

[southpaw66]

I'd be happy to show more comparisons (even remaps...).

If anybody can provide the torque curve in Nm in 200rpm increments. I'll see what I can do - but I really must get on with some real work so no promises it'll be quick.

 

[RobinA3]

0-60 is an art, and a car killer. If it’s your car, I will suspect you will never get close to the manufactures claimed 0-60 figures, because most will fall part after a couple of good attempts.

Some tips, the manufacture is allowed to remove anything from the car that’s not fixed, so that mean carpet mats spare wheels, boot carpet etc, but not seats. Next fuel and oil level, fuel just enough for you performance tests, and oil on minimum, who cares about a bit of oil starvation. Tyre pressures dropped to around 8-10 psi are good, it’s a trade off between top end drag and launch grip, so you have to experiment. The tyres need to be warm, very warm, so some smoke drag car style is required, I have found three smaller smokes are better at warming than one big long smoke (personal experience). The must be the same size, but you should select the tyre with the most grip. The Launch this is where DSG comes into its own because it has a programme to do this, but if you have a clutch you need to side step it, i.e. let the move your foot to the side, not bring it up, also the revs need to be high enough not for the engine to bog, this can be very high in a 4wd car, and often lead to clutch failure. No clutch gear changes, as hard and fast as you can move the stick, the gearbox but won’t last long but who cares. Lastly when and where, you need a special tarmac high grip surface (like a drag strip) and perfect conditions.

If you fancy it than take your car to Drag Strip open day and have a go.

PS The driver need to weigh 75Kg

Most manufacturers record their performance times by having half a tank of fuel and 2 passengers on board, this will be listed in the car Brochures.

Also manufacturer 0-60 times are usually slower than the real times as they have to allow for differences between cars.

In VW/Audi driver magazines when they test a car they test the 0-60 times and these figures are always faster than the manufacturers quoted time. Audi quote that the 2TFSI 2WD does 0-60 in 7secs but the magazine quoted approx (can't remmeber the exact figure) 6.7secs but it was faster than the manufacturers quoted time.

 

[HeliChris]

Great so 0 – 30 buy the TDI, and all the rest TSFI wins, but only if are prepared to drop/hold a cog.

But to balance this

TDI wins or draws all “in gear” acceleration with the TFSI up to 110 mph.

 

[HeliChris]

Most manufacturers record their performance times by having half a tank of fuel and 2 passengers on board, this will be listed in the car Brochures.

Also manufacturer 0-60 times are usually slower than the real times as they have to allow for differences between cars.

In VW/Audi driver magazines when they test a car they test the 0-60 times and these figures are always faster than the manufacturers quoted time. Audi quote that the 2TFSI 2WD does 0-60 in 7secs but the magazine quoted approx (can't remmeber the exact figure) 6.7secs but it was faster than the manufacturers quoted time.

VAG and German car in general are exceptions to this because the focus for them is top speed, not acceleration.

Ask a German how fast is his/her car they will tell you the top speed, ask the same question in a English pub and 0-60 gets quoted.

Strap some timing kit onto your car and see how close you get, it might suprise you, but nice if you can proven me wrong

I suspect VW/Audi driver mag was a lot harder on the car than you may think. I know an editor of a car mag that binned three M3's (going back a few years now) at a press launch trying to match lap time Tiff's, did BMW care, no they gave him a M5 to drive home in (also lanuched on the same day).

Chris.

 

[Amchlolor]

IMO,Audi have changed the gearing in the DSG gearbox to chase a good 0-60 time.
This helps them sell it as a performance gearbox.
Put it this way,it would be difficult to sell it if it made the car slower...

I bet the 0-100mph times are massively different between the 170tdi and the Tfsi.
The 140tdi dies a death after 60mph,for example.
According to my own tests,it takes just under 9 seconds to get to 60mph,then a whopping additional 17 seconds to get to 100mph.
26 seconds from rest to 100mph is an eternity,I can assure you.
Glaciers move faster.
There are those that will argue that it's academic but,then again,who stops accelerating at 60mph ?

 

[h5djr]

Out of interest, I wrote to the Audi Driver magazine to see if they could find out the gear ratios and mph/1000rpm for the 2.0TDI with DSG. They have just published part of my letter together with the answer in this months magazine.

A copy of part of the letter and the data can be viewedhere

 

[RobinA3]

ah it was you who wrote in!

i was reading it last night and thought hold on that question was asked on the forum!!

 

[southpaw66]

Out of interest, I wrote to the Audi Driver magazine to see if they could find out the gear ratios and mph/1000rpm for the 2.0TDI with DSG. They have just published part of my letter together with the answer in this months magazine.

A copy of part of the letter and the data can be viewedhere

The comment about 4th and 5th gears being swapped is wrong, it's because there's a different final drive ratio for 5 & 6, not just the one as listed. So I guess they don't know everything. Perhaps you could write a follow-up.

Needless to say the data you supplied me was spot on. Thanks again

 

[h5djr]

The comment about 4th and 5th gears being swapped is wrong, it's because there's a different final drive ratio for 5 & 6, not just the one as listed. So I guess they don't know everything. Perhaps you could write a follow-up.

I must admit that, after looking at the information about the various gear boxes I found on Elsawin and seeing the different final drive ratio for 5th and 6th, I did wonder if that was the explanation. I will have to drop them a line.

 

[southpaw66]

Having compared the figures I can see that they've used the final drive ratio for 5 & 6 for all 6 gears so it's 1-4 mph/1000rpm that are wrong. The final drive for these gear is 4.06.

 

[southpaw66]

From my spreadsheet

1000rpm 2.0DSG 225/40R18

5.2
8.8
13.9
20.1
26.8
32.4

 

[h5djr]

What would the mps/1000rpm figures be for an A3 Sportback 2.0TDI 170 DSG running on 7.5Jx 17 wheels with 225/45 R17 tyres. Thanks

 

[southpaw66]

Essentially the same as circumference is 1993mm compared to 2001mm

1000rpm 2.0DSG 225/45R17

mph
1st 5.2
2nd 8.8
3rd 13.9
4th 20.1
5th 26.7
6th 32.3