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Thread: Jaguar XFR

  1. #31
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    See I woulda thought it'd take longer for the turbo to wind up - 2,000 rpm is still pretty low rpm to me - maybe I'm thinking too much from a gasoline car standpoint.

    Great summary there Clive many thanks.

    Do diesels idle lower than gasoline cars?

  2. #32
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    The turbo spools at a lower speed (2000) not because it is idling lower, but because it doesn't have as high a top speed.

    A turbos max flow rate is dependant on size, and with the lower max revs of a diesel the turbo is smaller, allowing it to build pressure at a lower engine rpm.
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  3. #33
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    Quote Originally Posted by Kitdy View Post
    See I woulda thought it'd take longer for the turbo to wind up - 2,000 rpm is still pretty low rpm to me - maybe I'm thinking too much from a gasoline car standpoint.
    Consider that most diesels have their redline at 5k rpm. 2k rpm is nearly half way through that rev range.

    In a petrol car, the equivalent would be revving the car to about 3k rpm just to get enough power to move...!

    The disadvantage of trying to compensate for lack of displacement with turbochargers, I'm afraid!

    Quote Originally Posted by Kitdy View Post
    Great summary there Clive many thanks.

    Do diesels idle lower than gasoline cars?
    No worries mate, and yes: Diesels do idle at lower revs, too.
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  4. #34
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    Quote Originally Posted by Soloracer View Post
    fail.

    ^ yeah, are you familiar with this organization known as the police. they have a relatively large impact on the issue of speeding. in fact they can restrict your ability to drive permanently if you disobey their rules. which to an enthusiast of high performance driving such as yourself, you might as well be dead.
    I never got a ticket in my 5 years of license, nor I do intend to get one, I just described the way cars are driven here, not the way I drive.

    Quote Originally Posted by henk4 View Post
    so this 5 liter supercharged engine produces a whopping 625 NM. Wow. A week earlier Jaguar presented a 3 liter turbo engine, producing 600 NM (and probably 50% less fuel consumption). That version of the XF is also limited at 250 kph. May reason win....
    1 Supercharger Vs 2 Sequential Turbos + direct injection, an unfair comparison!

    EDIT: I saw even the new petrol engine has DI, still, it's afirst in their petrol engines while in diesel engines it has been a must since almost 15 years I would say

    Even if a diesel always produces more torque regardless of the technology adopted, it's the only thing it can give you.
    with the same tech the fuel consumption of petrol engines will be heavily reduced, and they would still perform better. you know better than me that having more torque doesn't mean something as a given fact.
    and providing a diesel engine that could deliver the same kind of performance of this new 5.0 V8 (which we know is going to be faster perhaps on track, even if the car won't likely see a track period) the fuel consumption would drop, and the emissions raise.
    but for everyday driving, yeah, props to the new diesel rather than to this one (even if it's probably heavier)

    Quote Originally Posted by Kitdy View Post
    Off topic, my question to you is how is power delivery with your new sequential turbo C5? I've always heard diesels have lots of low-end torque and are good for low-engine speed grunt yet they have turbochargers which can delay high end throttle response. Does the mid- and low- end torque make the power surge more linear in a turbo diesel than say a turbo gas car? Is there a lot of turbo lag in modern diesels or a car like yours?
    low end torque as said by Clivey can be frustrating, as driving a smaller petrol engine perhaps, you have to rev a little.
    with variable geometric turbos the situation is much better know, and with two turbos (sequential or not) I guess there are no issues at all.

    Quote Originally Posted by Kitdy View Post
    See I woulda thought it'd take longer for the turbo to wind up - 2,000 rpm is still pretty low rpm to me - maybe I'm thinking too much from a gasoline car standpoint.

    Great summary there Clive many thanks.

    Do diesels idle lower than gasoline cars?
    even if the red line in a diesel is between 4500 and 5000 rpm, you would change gear at 4000 at most, because the trust disappears quite quickly, and the noise is, well, noise.
    My diesels both idle at about 850/900 rpm
    Last edited by LeonOfTheDead; 01-11-2009 at 07:01 AM.
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  5. #35
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    Quote Originally Posted by Clivey View Post
    The disadvantage of trying to compensate for lack of displacement with turbochargers, I'm afraid!
    And I guess that's even more evident the smaller the engine is.

    It's not like normally aspirated diesels ever made decent power though.
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  6. #36
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    Quote Originally Posted by Ferrer View Post
    It's not like normally aspirated diesels ever made decent power though.
    I wonder what sort of mileage you'd get with a naturally aspirated diesel engine in a car. It'd be weak yes but the mileage difference of adding a turbo is what piques my interest.

  7. #37
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    Quote Originally Posted by Ferrer View Post
    And I guess that's even more evident the smaller the engine is.

    It's not like normally aspirated diesels ever made decent power though.
    MB 2.2 liter was good for 86 bhp in the old E-Klasse, don't remember the torque figure
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  8. #38
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    Quote Originally Posted by Kitdy View Post
    I wonder what sort of mileage you'd get with a naturally aspirated diesel engine in a car. It'd be weak yes but the mileage difference of adding a turbo is what piques my interest.
    Well probably better. Then again modern turbo petrols sometimes get (officially that is) better fuel consumption figures than it's normally aspirated counterparts so who knows...
    Quote Originally Posted by LeonOfTheDead View Post
    MB 2.2 liter was good for 86 bhp in the old E-Klasse, don't remember the torque figure
    The old W124 had a 3 litre 4vpc normally aspirated diesel with 150bhp. That's the most powerful N/A diesel ever installed in a passanger car, AFAIK.
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  9. #39
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    Quote Originally Posted by Ferrer View Post
    Well probably better. Then again modern turbo petrols sometimes get (officially that is) better fuel consumption figures than it's normally aspirated counterparts so who knows...

    The old W124 had a 3 litre 4vpc normally aspirated diesel with 150bhp. That's the most powerful N/A diesel ever installed in a passanger car, AFAIK.
    without the turbo, diesel's efficiency drops substantially.
    even if the mileage can seem better, the performance are highly mortified, and the emissions very high too.

    that 3.0 liter wan't so bad, considering the first 3.0 liter turbo from BMW was good for 184 bhp (again regardless of the torque).
    probably the difference was more evident on the road than on the sheet.
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  10. #40
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    Basically, the main reason you'd drive a diesel is that it's cheaper to run than the equivalent petrol.

    My choice was also influenced because the 1.6 Diesel C4 is just as quick as the petrol - as long as you have the boost...and the ECU can easily be remapped so the engine then produces 140BHP.

    It has more torque than the petrol, but the petrol is a lot more responsive.

    In most other cars, I'd rather have a petrol of the equivalent price because of the enhanced drivability, but the C4s weight (1,270 kg) would crush a 1.6 N/A petrol.
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  11. #41
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    Quote Originally Posted by Clivey View Post
    Basically, the main reason you'd drive a diesel is that it's cheaper to run than the equivalent petrol.

    My choice was also influenced because the 1.6 Diesel C4 is just as quick as the petrol - as long as you have the boost...and the ECU can easily be remapped so the engine then produces 140BHP.

    It has more torque than the petrol, but the petrol is a lot more responsive.

    In most other cars, I'd rather have a petrol of the equivalent price because of the enhanced drivability, but the C4s weight (1,270 kg) would crush a 1.6 N/A petrol.
    You are the ultimate combatant against henk for the never ending diesel-gasoline war. Throttle response is critical to me, and the simple fact that diesels are chosen I don't think for driving pleasure but for economical reasons by a vast majority of drivers is pretty damning. Not saying there aren't diesel fans out there, but if you guys in Europe paid what we paid for gas would diesels be anywhere near as prevalent? I doubt it.

  12. #42
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    For everyday use, in modern day congested traffic the 3 liter Jag would be greatly preferable. No hustle, no nervous revving, just power when you need it. I would not care less about the sound of the V8. You know that when you start enjoying it, your fuel tank is being drained.
    With regard to the question of my personal experience with the biturbo engine, the turbo lag is totally gone, average fuel consumption over the first 6500 km is around 7 liter per 100 km. Set to improve during warmer periods and also following the latest tweaks which have increased torque to about 470 NM and BHP well over 200. Torque may not be too important for those who like red line driving, but it greatly helps to get maximum acceleration in about any gear you want.
    Turbo charging in diesel engines is much older than for petrol cars, all post war marine engines are fitted with turbo, and my armoured vehicle from 1965 had a diesel turbo as well. It is just as well part of the technology as sparks plugs are for petrol engines. My first two diesel cars did not have it though, and I got about the same mileage as with the current C5, (in a car weighing 1050 kg and just capable of 100 mph).
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  13. #43
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    Wiki has the 2L diesel C5 rated at 47 mpg, yours is the 2.2 I think which they have listed at 43 which is a bit away from 7L / 100 km I think. 47 mpg in a car that weight is pretty impressive.

  14. #44
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    Quote Originally Posted by Kitdy View Post
    Wiki has the 2L diesel C5 rated at 47 mpg, yours is the 2.2 I think which they have listed at 43 which is a bit away from 7L / 100 km I think. 47 mpg in a car that weight is pretty impressive.
    my version is supposed to do 6.2 on average, according to the ECE ratings.
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  15. #45
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    Quote Originally Posted by Clivey View Post
    Basically, the main reason you'd drive a diesel is that it's cheaper to run than the equivalent petrol.
    Indeed.
    Quote Originally Posted by henk4 View Post
    My first two diesel cars did not have it though, and I got about the same mileage as with the current C5, (in a car weighing 1050 kg and just capable of 100 mph).
    I wonder what a normally aspirated diesel with modern technology could do.
    Lack of charisma can be fatal.
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