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Post by LeeXS on Mar 11, 2005 5:05:16 GMT -5
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Post by PugGTi on Mar 11, 2005 6:44:26 GMT -5
For some bizarre reason they've measured the GTi's torque at 2600 revs - it's never gonna be a high figure there (not on a smallish petrol engine). Peak torque is somewhere between 4000 - 5000RPM and it should be around 140lb/ft.
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Post by Mitch on Mar 11, 2005 6:45:51 GMT -5
to the best of my knowledge...
Torque is the force of which the car can accelerate
and believe me, times have changed. The new generation diesels are more than a match for their petrol equivs! the diesel xsi gti is a 1.6 and they sell it alongside the gti in terms of performance which is based around huge in-gear acceleration (which in real world terms a rolling test accelerating in 4-5th gear, would leave our Xsi's for dead, id have to change down to keep up!)
And if you really want to see what the new diesels can do look no further than the skoda fabia vrs! I believe it spanked a cooper s around top gears racetrack and thats a 1.9 diesel
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Post by colonel-shoe on Mar 11, 2005 7:16:39 GMT -5
torque is the fundamental output of the engine, the fuel ignites, pushes the piston down which inturn exerts force on the crank turning the engine, this turning force is the torque. From this torque we can determine the power of the engine via the simple equation HorsePower=TorquexRPM/5252. The power is therefore the rate of work the engine can do. The power curve is easy to change, by improving the flow capacity ie better exhausts, induction systems etc. (hence the same 2L engine can range from 140 to 200 bhp. But changing the torque, which is pretty much a function of the engine geometry, is much harder without increasing engine size (aint no replacement for displacement ) so dont believe any claims of vastly improved torque by manufacturers of engine kits. Finally this brings us to Diesel v Petrol. The heavier design of the diesel engine due to the very high compression ratio and high temperatures means it cant spin up as fast, hence lower power at limited rpm. However the high temp and compression mean the fuel ignites with more force and burns for longer during the down stroke thus producing way more torque than a petrol. Torque is generally more useful for in gear acceleration, so most diesels wont beat hot hatches from a standing start, but on a motorway from 30-50 or 50-70 theyll leave em chocking on their exhaust. The latest hot diesles like the Fabia VRS can whoop a bmw 330 on the motorway and pretty much match a 206 GTi 0-60. I know ive talked round the houses but i hope i said something useful
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Post by LeeXS on Mar 11, 2005 7:46:57 GMT -5
Thanks for you explanation guys!! I understand now!!
So diesels are coming on in the World, are they still better fuel economy?
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Post by teddy on Mar 11, 2005 7:50:32 GMT -5
Finally this brings us to Diesel v Petrol. The heavier design of the diesel engine due to the very high compression ratio and high temperatures means it cant spin up as fast, hence lower power at limited rpm. However the high temp and compression mean the fuel ignites with more force and burns for longer during the down stroke thus producing way more torque than a petrol. Diesels don't rev high simply because it doesn't burn/ignite fast enough. With petrol engines you put the fuel air in and then add the spark so you can ignite it as fast as you want...with diesel it takes time to create the compression for the diesel to ignite itself...you physically can't reproduce this process any quicker... Can anybody explain to me why the 206 GTi HDi is so much slower to 100mph than the 138 GTi?
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Post by colonel-shoe on Mar 11, 2005 8:08:55 GMT -5
So diesels are coming on in the World, are they still better fuel economy? aye youll still be getting over 40 mpg even if you thrash em about all day
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Post by chi_chee on Mar 11, 2005 8:18:45 GMT -5
but dont forget that the petrol will redline at around 6200rpm - 6700rpm (for normal cars) and the diesel will redline much sooner, at around 5000rpm - 5500rpm....so therz more acceleration in any gear hence the faster to 100mph. by the time u wack 100mph in a petrol in say 4th @ say 4500rpm - 5000rpm (for arguements sake), you would prob be in 5th @ 2700rpm - 3500rpm (again for arguments sake) torque helps acceleration, so the diesel will win in most 0-30's, but over a longer distance the shorter rev range will allow the petrol to catch up.....thats y to get the most outta a diesel, you need to keep it preferably above 2000rpm! did that make sense....hehe?
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Post by LeeXS on Mar 11, 2005 8:18:48 GMT -5
How good is that!! So could be a diesel for me in the future then!!
Anythin to save money!! ha ha
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cduk24
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Post by cduk24 on Mar 11, 2005 13:46:00 GMT -5
I love my diesel ;D
The trick is not to rev the knackers off it when accelerating, and change up sooner than petrol. Overtaking rarely requires changing down a gear. Most of the acceleration has gone by 4250rpm.
This does of course mean that there's a lower power band than the petrol. But in that power band, those high torque figures explain themselves....!
Low insurance, good economy and good performance - it was a no-brainer as far as I was concerned.
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Post by Mitch on Mar 11, 2005 14:43:33 GMT -5
yup pretty much, poor ol KennyD got severe batterings for biggin up the diesels!
One thing I would note whilst everyone going on about fuel economy is that being life and the powers that be not liking people getting something for nothing, hike up the prices on diesel motors as they know people will pay the extra 1-2k for the fuel economy.
But heres how I see it with diesel pump prices higher than unleaded as well say my diesel xsi gti was doing 55-60mpg my petrol xsi does 40-45mpg you would have to own that diesel for at the very least 3-4 years (all this is from new of course) to make it worth the extra 1-2k premium when you bought it, and what do ppl do after 3 years when the warranty expires.....
BUY A NEW ONE!
So when jonny clever buys his new diesel thinking how much he saved by going diesel, unless he holds onto it as mentioned above hes actually paid about the same/probably more than owning a petrol from new.
Leaving only road performance to determine between two petrol/diesel alternative models.
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Post by BigOL on Mar 11, 2005 14:52:20 GMT -5
Never looked at it from that angle. How many people has that caught out.
Good to see you posting again Mitch!!!
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Post by chi_chee on Mar 11, 2005 14:55:23 GMT -5
u can try driving your car like the pope if on diesel......thus having even better fuel economy...haha
but tru what your saying mitch.......but dont diesel get taxed less aswell or is it more? but then the service interval on a diesel are much shorter.....so eventually will balance out.
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cduk24
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Post by cduk24 on Mar 11, 2005 15:24:40 GMT -5
True, diesels have a habit of costing more in the first place to buy. And yes, they cost more to service, simply because they need it doing more frequently. However this is again offset by the fact that diesel engines last longer. If someone changes their motor every 2-3 years, then it's probably not gonna save them much in the long run, unless they do galactic mileages (and it's not uncommon to see HDis/TDIs with 100K+ on the clock after 2-3 years). Tax can be quite cheap, and companies like them as emissions tend to be less than the equivalent petrol (=less company car tax). I pay £115 a year to tax my 2.0 lump, for comparison. It's all swings and roundabouts - and all depends what you want from the car in the first place. Me - I do high mileages, and therefore need good economy - but like that poke it has on motorways and general cruising. I have driven both petrol and diesel in recent years, and for me diesel is what I prefer, for the moment. In a few years when circumstances change, I may well change my mind.... The real question I have at the moment - why is our diesel more expensive than petrol?? (Obviously I'm biased, being a diesel owner.) Everywhere else in Europe, diesel is cheaper than petrol, and by quite a margin. It used to be the same here. Funny how that happened just as I bought a diesel car.....
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Post by Blackpug on Mar 11, 2005 17:16:40 GMT -5
Diesel became more expensive when more people began buying diesels - supply and demand!. After the govt. told everyone diesel was cleaner then petrol. LPG is cheap just now, Watch the price if more people convert. And if you want more torque... buy a turbocharged petrol car. I used to have chipped fiesta rs turbo....fastest car between petrol startions 20mpg!
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