ULTIMATE Petrol vs Diesel thread is incoming!!!





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  1. #1
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    Default ULTIMATE Petrol vs Diesel thread is incoming!!!

    Background (Read first): http://www.4x4community.co.za/forum/...ad.php?t=79935

    I've had enough of diesels now...
    It's time to crush some myths, and maybe spawn a few more

    This common argument that engine torque > everything, has now had it's last day. Time for some facts. How much of that "huge" torque actually gets to the wheels, when it counts.
    All this "oh, the low down torque is this good and that good", NO! None of that anymore!

    I'm currently looking at doing a head to head comparisons between the V6 Rubicon and the CRD Rubicon. The manuals will go against each other, and the autos will go against each other.

    I would've loved to stick the 2011 Jeep Grands against each other, but the CRD engine hasn't been released yet.

    If anyone wants a comparison done, I will need the following info:
    1) The vehicles have to be the same make and model, with comparable engine variants in naturally aspirated petrol and turbo diesel.
    2) I will need engine torque curves from the manufacturer for both engines.
    3) gear and diff ratios for both
    4) standard tyre sizes for both
    5) It would be nice to have factory performance specs of each vehicle as well, to use as a control.

    Something from the Appliance camp will be nice, and anyone else is welcome to add competing models!

    The barney is on, and it's not behind the pub, but behind the science lab.
    Last edited by RedLineR; 2011/03/25 at 11:32 AM.
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    I can't wait for some results, RedL.
    I have a suspicion that once this gets going, we will be hearing a lot of "but diesels are so fuel efficient"

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    Quote Originally Posted by ThysleRoux View Post
    I have a suspicion that once this gets going, we will be hearing a lot of "but diesels are so fuel efficient"
    I'm expecting that...
    Planning to hit back with a google site:www.4x4community.co.za injector failure, injectors replaced, problem with my td, turbo failure again, and similar search terms...
    I already have Herman saying he exports large quantities of turbos and injectors for the kzte engine into africa (can't remember the country). Yesterday I saw a guy here with a Ford (I think), 60 000km on the clock, on his 3rd turbo.

    So I'm actually hoping it goes that way... Will draw up some averages from info garnered here, and maybe translate that to R/km, including capital costs on MadMan thingies and UDF systems etc etc etc.
    SWAMBO
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    we are waiting!!!

    still can't find the torque/power graph for the 2.8CRD though...

    did you get the ratios? I would compare the V6 sahara vs the CRD sahara - the lower ratios in the Rubicon will skew things a little...

    either way the diesel will win

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    I still need the graph for the 2.8 CRD
    No probs, will use the Sahara.
    The petrol will win!

    But I can't get started without a full set of data for any 2 vehicles
    Was hoping the Toy-boys would jump in
    SWAMBO
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    It's a pity that the manufacturer's power and torque curves for DIESELS are so scarce. I have no been able to find any for Jeeps from the web ! I wonder if they're hiding something from us.

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    I've found a torque curve for the 3.0 CRD WK, and a chart for the 3.7 petrol!!!!
    Can anyone help with gear ratios and stuff?
    I'm looking on www.wkjeeps.com at the moment.

    Don't see much regards gear ratios and diff ratios.
    Nor some basic performance figures like 0-100 etc?
    SWAMBO
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    The vehicles have to be the same make and model, with comparable engine variants in naturally aspirated petrol and turbo diesel.


    What do you consider comparable engine variants? Surely a 3.7 petrol cannot be regarded as comparable to a 2.8 diesel?

    How about this for a first excercise: BMW 4.0d (that is a 3 liter diesel with twin turbos) compared to a 3l petrol BMW (or even the 3.5 which is the 3 liter petrol with turbos)? By the way, in this instance, the petrol (3.5) and the diesel (4d) have exactly the same power output (225kw), but significant torque difference. The figures are on the BMW website.

    C
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    Quote Originally Posted by RedLineR View Post
    I still need the graph for the 2.8 CRD
    No probs, will use the Sahara.

    The petrol will win!

    But I can't get started without a full set of data for any 2 vehicles
    Was hoping the Toy-boys would jump in
    Arent these tests supposed to be done un bias? My money is on the CRD all the way
    -

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    Quote Originally Posted by C Africa View Post
    The vehicles have to be the same make and model, with comparable engine variants in naturally aspirated petrol and turbo diesel.


    What do you consider comparable engine variants? Surely a 3.7 petrol cannot be regarded as comparable to a 2.8 diesel?
    I consider a slightly larger NA petrol as comparable to a slightly smaller TD. As we see the manufacturers produce them.
    Like with the WK Jeep example. a 3.0TD and a 3.7 petrol.
    Like Toyota. a 3.0 TD and 4.0 V6
    and so on and so forth.
    Not a 3 litre with twin turbos slapped onto it compared to a 3 liter NA.
    Then I'd rather use the 3.5L twin turbo petrol, and take a 15% knock on the curve, to compare it to the 3.0 twin turbo TD.

    But, why not? Lemme dig up the figures!
    SWAMBO
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    Quote Originally Posted by C Africa View Post
    The figures are on the BMW website.

    C
    Trying to find graphs and gear ratios now.
    Did you mean bmw.co.za or some other one?

    http://www.bmw.co.za/products/automo...edan/facts.asp

    Which 2 are the twin turbo 3 liters? The 535's?

    No torque curves so far though
    No gear and diff ratios either.
    Last edited by RedLineR; 2011/03/25 at 10:18 AM.
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    Dit kan al so bietjie help http://www.diskdrive.co.za/ dit ook dalk http://www.um.co.za/specifications/ soek nog net na die ratio's

    Jeep Commander 3.0 CRD Sport
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    Interestingly, when I search for the graph specific to the Wrangler CRD I get a lot of hits on this forum and naked women

    maybe the diesel kept breaking the dyno..

    a better graph of the 3.0 WK motor here (post 40) , but it relates to speed not rpm

    http://www.jeepgarage.org/showthread.php?p=173163

    as to comparitive - I think it's fair to compare the 2.8 to the 3.8 petrol...

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    So far, the closest we have to all the data is the WK Jeep 3.0 CRD vs WK Jeep 3.7 Petrol.
    Just need gear ratios and diff ratio.
    SWAMBO
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    Interesting how a bigger petrol is chosen (bigger = more NM) as the same sized petrol engine has way more kW than the diesel
    -

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    Sorry Red, I thought you needed only torque power and performance figures.

    WEhich models? Lets stick to the 4x4's and use X5 4.0d and 3.5i (both 3l with turbos).

    Oh, and these are all fitted with 8speed gearboxes so don't know how that affects your story.

    C
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    Here are the figures (all except torque graphs) , tyres are 255/55 18.

    C
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    Quote Originally Posted by RedLineR View Post
    So far, the closest we have to all the data is the WK Jeep 3.0 CRD vs WK Jeep 3.7 Petrol.
    Just need gear ratios and diff ratio.
    The gear and diff ratio's for the 3.0 CRD are on the WKJEEPS site that you looked at earlier. Look under SPECIFICATIONS. I am sure I saw the ratio's for the CRD there as well yesterday, but it could have been those for the WK2 CRD. Don't see any for the WK

    Here is the spec's for the 3.7:
    W5A580 AUTOMATIC, FIVE-SPEED OVERDRIVE
    Adaptive electronic control or Electronic Range Select (ERS) driverinteractive manual control and electronically modulated torque converter clutch.
    Gear ratios:
    1st - 3.59
    2nd - 2.19
    3rd - 1.41
    4th - 1.00
    5th - 0.83
    Rev - 3.16
    Axle: - 3.07, 3.55 optional

    Final Drive Ratio: 3.07:1 with 3.7-liter engine

    Overall Top Gear: 2.55 with 3.07 axle or 2.95 with 3.55 axle
    Tyres on LTD models: Petrol and Stinkers
    P245/65R17

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    Quote Originally Posted by C Africa View Post
    Here are the figures (all except torque graphs) , tyres are 255/55 18.

    C
    Great stuff! Thanks!
    Will need the torque curves though, as I want to do the comparison in 1000 or maybe even 500 rpm increments.
    I'll have a look around.
    Are those both twin turbo engines (the 35 and 40)?

    8 speed is fine, as long I have all the ratios for all the gears and the diff.
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    Quote Originally Posted by Sennin View Post
    Interesting how a bigger petrol is chosen (bigger = more NM) as the same sized petrol engine has way more kW than the diesel
    The TURBO makes up for the difference in capacity - between 30 and 50% IIRC.

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