Yeti power curves

[prodata]

Some weeks back, someone posted a link to some engine power/torque curves for the Yeti. But I can't seem to trace these now - conceivably they went missing during the forum revamp? Does anyone have a note of the link(s) please?

[aerofurb]

Scroll down on the Auto.CZ page linked below, torque and power curves are there:

http://magazin.auto....i-z-kvasin.html

[prodata]

Many thanks - would never have found these again myself.

I'm trying to make a final decision between a 1.8TSi and a CR170. I'm undoubtedly more used to and would ideally prefer the petrol option but its emissions are high and MPG possibly poor. But it's accelerative power that I'm most interested in and I guess that the diesel might be a worthy competitor here. But there's a dearth of published/detailed/reliable acceleration figures. So I'm reduced to looking at the power curves to try to get some idea of what's likely to happen.

Unfortunately the 1.8TSi and CR170 data are on different graphs with different scales, hence not too easy to compare. So I decided to transcribe them on to the same chart to get a better idea. Here's a copy in case it's of interest to anyone else:

NB The transcription has been done manually together with some automated line smoothing, so there's some scope for human error and also scope for some artefacts in the details of the curves - don't worry too much about very minor imperfections, they may well not be real but shouldn't amount to more than 1-2% deviations from reality (eg the slight kink in the CR170 curve at around 1850rpm).

Take-home message is obviously that the CR170 does deliver significantly more power right across the 1200-4400 rev band. And just to illustrate this more clearly I've replotted the difference between the two curves as the CR170/1.8TSi power ratio, slightly adjusted to allow for the extra weight of the CR170:

which obviously confirms that the CR170 delivers >100% of the 1,8TSi power over 1200-4400 and >120% over 1300-3500. (Of course, this graph can only be generated for the rev range covered by the diesel, whereas the 1.8TSi carries on out to 6500. But personally I don't often push petrols over 5500 and limiting the max rpm to 5000 might be a small and acceptable sacrifice.)

For completeness, I've also done a like-for-like comparison of the torque curves:

which shows the expected advantage that the CR170 possesses in the low to mid range. But I still struggle to understand the relevance of torque to acceleration (any engineers here like to explain? I understand the definition, but it's the connection to 0-60 where I struggle). Power, on the other hand, seems directly related to acceleration. Power, AIUI, is the maxium rate at which energy can be transferred from the engine to the vehicle as a whole, which surely must be a direct correlate of acceleration.

Edited 22 March, 2010 by prodata

[StewartK]

I have always driven petrol engined cars but I decided to try the CR 170, my local dealer happened to have one as their demonstrator. On my test drive I was a bit cautious when I started out but after a few minutes decided to give it a bit of welly. I was pushing the accelerator pedal with the same force I use on my Volvo V40 (115bhp, 165Nm) and found I was hanging on to the steering wheel for dear life as the g-force tried to push me back through the seat. It goes like brown stuff off a stick, the last car I had that was as much fun was my Fiat Barchetta (130bhp, 158Nm) and it weighed as much as a leaf. I was sold on the diesel in this car and I've ordered one. It was actually a better drive than my wife's MINI Cooper.

Why not have a comparison test drive of the two?

Stewart

[aerofurb]

Thanks prodata for the graphs, interesting stuff. Now go buy a CR170 - you know you want to....

[Agerbundsen]

I have to preface this with telling you that I have not driven the 1.8 petrol.

I do have a 170 hp TDI and have spent a fair amount of time at speed on Autobahns in Germany and the other motorways down through Europe. The 170 gives you the best of both worlds. Superior acceleration in-gear of the turbo Diesel and freely revving up to the 5000 rpm limit.

At speed in 6th, there is just so mych torque that you just put your foot down and it easily keeps up with all the road warriors in the left lane on the highway. Combine this with cruizing at 90 mph at 2600 rpm - nice and quiet.

Your graphs do tell the story - the Diesel ios definately the superior fighter in the comparison.

0-60 mph is just a number. You are so busy swapping cogs that you don't notice that you are past 60 just after changing from 2nd to 3rd.

My biggest concern is cost - in just normal tooling around on the small roads, it feels very comfortable and quiet, but the speedo tells you that you are at risk of reprisals from the local gendarmes.

[prodata]

Why not have a comparison test drive of the two?

Yes I would if I knew of a CR170 demonstrator not too far away (live in East Cambs). Most seem to be CR140's which is obviously something of a guide to the 170, but not the real thing, or other lower performance models. I have tried the 1.8TSi and - as previously reported - felt fairly underwhelmed by it, not got the performance of my present Accord for instance. But I could only get a fairly short test drive and it was a newish, maybe tight, car.

But this experience, despite my preference for the quieter, more transparent power delivery of a petrol engine, is what's made me look towards the CR170. The question for me is whether the potential extra power of the CR170 outweighs its extra harshness (NVH overall) under acceleration. I know I'm taking a while to come to a decision, but this will probably be the only car I will ever have bought from new with my own cash, so I kind of feel entitled to take my time and weigh the pros and cons.

It really would have been nice if there had been some reliable in-gear acceleration figures (eg 30-50, 50-70) for the different Yeti models in the motoring press, but even when figures do exist (eg the Autocar CR140 full review) there's no real note of the test car's mileage, road surface conditions etc, all of which have to have some impact on the numbers. (And quite apart from apparent discrepancies in the numbers that are published.)

So this is why I found myself looking at the power curves, just to try to get some objective idea of the likely accelerative feel of the CR170. But even so, I don't quite understand why the CR170's power superiority over the 1.8TSi in the 1200-4400 rev range isn't translated into a noticeable margin in 0-60 times (which is the only performance figure in the Yeti brochure - anyone seen a CR170 review with data anywhere?). I guess it must have something to do with gearing and when gear changes are made in the 0-60 sprint (but this is really why I prefer to see in-gear figures)

@aerofurb: Yes I probably will end up going for the CR170 soon - just one or two final steps in the decision making process to go

Edited 23 March, 2010 by prodata

[Regorip]

Thanks for the graphs Prodata - nice work!

You mentioned the possibility of harshness in acceleration of the 170 CR.

I have no previous experience of diesels (either turbo or non), but have owned a turbo petrol and I don't find the 170 CR at all harsh in accelaration - just a decisive and continuous push in the back up to 3500 rpm (my max for the moment). I find the car very responsive and so far, ( only done 2000 km ) a sheer pleasure to drive.

RP

Edited 23 March, 2010 by Regorip