ULTIMATE Petrol vs Diesel thread - Comparisons - Page 5





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  1. #81
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    Quote Originally Posted by HeinrichC View Post
    This thread makes me think of someone that once said a certain Rugby team looks good on paper and the other replied that the game is not played on paper it is played on grass.

    Get out there and actually do a physical comparison else what you have here are just figures...
    I have figures based in science, on mechanical devices whose performance is consistent and can be imperically measured...

    Someone once said... I have this atomic bomb designed on paper, and a Japanese general said, bombs explode on battlefields, not on paper. That assertion did not work out so well.... Every single piece of technology that makes our way of life possible, comes from paper. Hasn't failed yet.
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  2. #82
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    my diesels are running fine. the Wrangler and the TD5.

    both petrol powered V8 land rover monsters have power steering issues, idling issues and overheating issues...

    the petrol powered bakkie also cost a few beans a few weeks back.

    AND THEY KILLED MY PETROL CARD WITH A VENGEANCE

    they are also always in for a bloody service, I like 20 000km diesel services thanks....

    I'll stick to my diesels...

    gear ratios are on that spread sheet I posted, will look at work for the nominations tomorrow...

  3. #83
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    Thanks Apoc!
    Here's what I have for Jeep so far.

    I'll use the ratios you supply for both models fitted with those engines, as they are the only curves I have for Jeep.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Attached Files Attached Files
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  4. #84
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    Quote Originally Posted by Estee View Post
    And turbo petrol V8s are even betterer

    I would love one but cannot risk it when running the ramblas here when they are flooded.



    regards

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  5. #85
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    Quote Originally Posted by RedLineR View Post
    Thanks Apoc!
    Here's what I have for Jeep so far.
    I'll use the ratios you supply for both models fitted with those engines, as they are the only curves I have for Jeep.
    um. neither motor is fitted to the Wrangler...

    but I guess it's fair enough...

    would love to get the 2.8 specs...

    I think the 3.8 petrol curves were on the sheet?

    the 5 speed auto diesel vs the 4 speed auto petrol will help...

    when you start seeing some of the specs - like gearboxes and so on and how it affects the performance, I do think there is a lot of room for maximising the performance of petrol and diesel...

    I was shocked to find out the other day that a V6 Tuna is more expensive than the D4D

    what happened with that from Toyota? they got something wrong...

  6. #86
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    Quote Originally Posted by RedLineR View Post
    thanks very much!

    Here are the gear changes drawn in.
    Just changed all the diesel graphs to blue, and all the petrol to red lines.
    The change line I had to draw in.
    And then my awesome colouring skill to highlight the areas.

    RLR - that red/blue grapg is most insigthful. I am most interested to see the graph if you would limit the red petrol graphs to 4000rpm to reflect the real world driving scenario.


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  7. #87
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    Quote Originally Posted by RedLineR View Post
    I have figures based in science, on mechanical devices whose performance is consistent and can be imperically measured...

    Are you conducting actual practical tests on these vehicles?



    Someone once said... I have this atomic bomb designed on paper, and a Japanese general said, bombs explode on battlefields, not on paper. That assertion did not work out so well.... Every single piece of technology that makes our way of life possible, comes from paper. Hasn't failed yet.
    Nope, I don't think this is true as the Jap's would have run like hell...

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    Quote Originally Posted by RedLineR View Post
    Thanks Apoc!
    Here's what I have for Jeep so far.
    I'll use the ratios you supply for both models fitted with those engines, as they are the only curves I have for Jeep.
    Not Wrangler specs though...

  9. #89
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    JIC - thats not fair to the petrol people

    if you are going to do it, drop out everything over 3000rpm for the diesel too

    actually, I'm surprised. a few things over the last few days in fact...

    the Tuna V6 advantage is huge with the gearbox attached.

    but it's more expensive too which really blew my mind...

    and it services more often....

    I for one am going to relook at it all very carefully.

    in reality the only ones I've driven back to back was the Wrangler V6 vs CRD, and with the 5 speed box vs the 4 speed petrol, the diesel is better.

    the D4D is a fine motor. and we haven't seen the manual numbers, but with a 4 speed auto bos and a 5 in the petrol, it's clearly not a winner.

    Pajero was surprising for me too....

    hmmmm....

  10. #90
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    Quote Originally Posted by HeinrichC View Post
    Nope, I don't think this is true as the Jap's would have run like hell...
    funnily enough, I suspect they would still have stood there...

    they may have raised a finger to the plane as it flew over though...

    tough crowd are the Japanese...

  11. #91
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    Quote Originally Posted by Apocalypse View Post
    funnily enough, I suspect they would still have stood there...
    they may have raised a finger to the plane as it flew over though...
    tough crowd are the Japanese...
    Banzai!!

  12. #92
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    You need to index your RPM range, where the petrol start to show an advantage the diesel does not rev to that range... Apples with Apples

  13. #93
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    Quote Originally Posted by Jeepiscool View Post
    RLR - that red/blue grapg is most insigthful. I am most interested to see the graph if you would limit the red petrol graphs to 4000rpm to reflect the real world driving scenario.
    Sorry, but that was not part of the mandate.

    The purpose of this was to show that petrols deliver more torque at low rpm, as used for 4x4'ing, and that they will outperform their diesel sisters.
    In this, I think the figures are pretty conclusive.

    You are of course welcome you interperate the figures as you wish, draw your own conclusions from your own criteria.
    You can for instance, simply choose to only accept data between 1500 and 3000 rpm, and I'm sure the TDs will come up tops.

    I can't however force the TDs to change gear at 6000rpm, by simply extrapolating the drop in torque beyond 4000. It's just not in the mandate I set out.
    Just like I can't limit the diesels' torque output.

    I also cannot see myself setting up a scenario, where two cars involved in an acceleration test, both running wide open throttles in every gear (as those curves only represent wide open throttle, and the guy in the petrol decides to shift at 4000rpm.
    But, if it makes you feel any better. If you cut the nuts off a petrol, and force it shift at 4000rpm, a TD would beat it everytime, since we are not applying a torque limit or similar handicap to the diesel.
    Last edited by RedLineR; 2011/03/30 at 10:05 PM.
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  14. #94
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    Quote Originally Posted by HeinrichC View Post
    You need to index your RPM range, where the petrol start to show an advantage the diesel does not rev to that range... Apples with Apples
    1 engine, within it's capabilities, compared to another engine (in direct competition with the first from the same make and model) within it's capabilities. Apples with Apples.
    Like I said in the beginning. The TDs cannot backtrack once the results are in.
    And that was the very point I set out to make. That a petrol's wider rev range holds a larger advantage than a diesel's higher torque.

    Else I can just index the rpm range from 4000-6000rpm. How the TD get's there is not my problem?

    Or I can simply torque limit the diesels, to the petrol's torque limit, then limit the petrol to the diesel's rpm range. But that would prove nothing.
    Why should I limit the petrol's rpm range, but not the diesel's torque?
    Apples with apples?
    Or are we trying to to limit the petrols so the diesels look better? And then trying to justify such a handicap?

    I actually don't think the diesels did bad at all. I was expecting it to be worse.
    I cannot alter the figures to suit people's expectancy.
    Last edited by RedLineR; 2011/03/30 at 10:05 PM.
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  15. #95
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    Jeepiscool,
    There is nothing "real world" about limiting my V6 Pajero to 4000rpm.
    4000rpm is 67% of the revs to max power for the 3.8V6. 67% of max power revs for the DiD is 2500rpm. Thus, if you want me to limit my engine to 4000rpm, the diesels should limit their's to 2500rpm.
    Lets consider a real life example: I'm on holiday with my good mate who owns a DiD (which is a true example) and we are relaxed and want to obey the 67% rule. We are cruising at 120 in 5th and we come up on a long truck cruising at 100. If we both engage Tiptronic to remain in 5th and floor the pedal, he will accelerate faster than me. He will reach his 67% limit at 130km/h, where I will be able to continue to 186km/h if I so wish before reaching my 67% limit.
    If we were on the N14 on our way to the Righterveld we would need to overtake a long truck every 5 minutes heading towards Kuruman. Now the sums become interesting, we need to get past those trucks quickly or end up spending hours stuck behind them. Still obeying the 67% rule, he can not gear down to 4th at 100 behind the truck, so he has 1237Nm wheel torque available to get him past the truck. I can slip into 4th and have 1406Nm wheel torque available to do the job and can accelerate to 136 before getting to the mystical 67% limit.
    So I still have the advantage even if I chose to pussyfoot along at low revs.
    The beaut of the matter is that I do have 6000revs on tap and believe me if I were to stomp on it behind that truck, the box will snap down to third and propel me past that truck with 1955Nm wheel torque at hand. Similarly, the diesel will kick down to 4th and have 1645Nm at hand. Of course now both of us would be breaking the 67% rule.
    And yes, we all know that at the next town I'll be pulling in for petrol and he will stop at the road side cafe for an ice cold Coke.
    I think the purpose of this thread is not to say petrol is better than diesel, all we do is putting the figures on paper and dispelling the myth that diesel has the torque edge on petrol.
    I had three DiDs in a row and bought my current 3.8V6 as a "dummy" to make me feel better after the last kid moved out of the house. I actually wanted to buy a sporty SUV and got within inches of buying a Volvo X/C (petrol with a big turbo), when SWAMBO put a stop to it and insisted on another "we can trust it" Pajero.
    If you were to wake me up in the middle of the night and ask me which Pajero I prefer, it would be the 3.2DiD every time - simply because of the fuel consumption and associated longer range.

  16. #96
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    RoelfleRoux's reply now was the best thing to happen to the thread since it started.
    Putting things into perspective and just guiding some of the bloodthirsty intentions back on track and the purpose of the thread. I am going to bed to dream about my diesel hardbody which I don't want to trade for anything else. Goodnight.

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  17. #97
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    Beautifully put Roelf!
    Not as harsh as my comments!

    And, to be fair, I really am still planning to incorporate fuel consumption and purchase price. I absolutely have to do it, it's in the initial mandate.

    And with your permission, I'll use the sheet you modified, in order to include the graph. I recently upgraded MS Office, and the new graph interface has changed so much, that I'm battling to create graphs with custom x and y axis intervals and labels.

    My apologies for my lack of patience when I perceive a veiled "bending the slide rule" request.
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  18. #98
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    RedL,
    Of course you have my permission you use your hard work

  19. #99
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    Well, as I diesel fan, I've just been informed that come 2012 there will be a 5.7Hemi available in the Wrangler. the one with the fuel saving 4 cylinder cruising mode....

    which is 5 aces as far as it goes beats the diesel every time

    the biggest surprise for me is actually the way the diesels are set up by the manufacturers - gearbox and ratio wise...

  20. #100
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    Quote Originally Posted by Apocalypse View Post
    the biggest surprise for me is actually the way the diesels are set up by the manufacturers - gearbox and ratio wise...
    Same here...
    And what was more of a surprise, is how successful the Triton setup is, using the exact same gearbox, only changing the diff ratio.
    I was of the opinion that the gearboxes and diffs would have to be totally different (increase in production cost).
    Granted, that the Pajero setup is even better. I thought the Triton setup would be a lot worse.

    But the Fortuner setup really blew my mind. I can only imagine that Toyota is full of petrols heads.
    "What gearbox will we pair with the D4D?"
    "Who cares, it's a tractor. Give it the old 4 spd. Owners won't notice. It's a diesel, it's slow. And we price it cheaper than the V6 then!"
    Last edited by RedLineR; 2011/03/31 at 08:43 AM.
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