[WIP] Jaguar XJ13 1967

Discussion in 'Vehicles' started by mantasisg, Nov 26, 2018.

  1. Godwind Racing

    Godwind Racing Registered

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    Why did they not bothered to race this? Same scenario Ferrari had with the F50 GT in 1996. The XJ13 would've been competitive against the likes of the early GT40s, Ferrari 250 LM and the Porsches 904 (though they were of a different class) but not the 1966-onward generation cars, that was why they pulled it out

    BoP this and others so this can be as fast as the Lola T70, Ferrari 330 P4 and Ford Mk. IV is like butchering a film, based on a historical event, for the sake of entertainment
     
    Last edited: Feb 24, 2019
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  2. mantasisg

    mantasisg Registered

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    In actual rF2 I am doing quite simmilar laptimes with Howston in Goodwood (1'21). It is either too slippery, or I am too slow. I have also done 1'27 with Cobra, though in goodwood they does under 1'25 with Cobra 289. Too little grip in rF2 bias plys ? Jusr released test version of goodwood, so you can try :)

    Totally agree that BoP'ing classic cars is like butchering art. I want the car as authentic as possible. The best BoP is different skills of drivers, though does not work well because best drivers usually end up in best cars :D

    It is really sad that XJ13 never happened for real, they only made one serious testing in Silverstone in 1967, it already did better than GT40 then, and it had plenty of issues to get fixed and get faster. I think in LeMans with very low drag, decent power it would have been dominating with top speed, and the main challenge would have been reliability. In other tracks without any downforce and less straights it would have been difficult for Jag. Looking at GT40 program it is quite clear that making a reliable and good allround car was very tough, and without Caroll Shelby probably wouldn't even had happened. Jaguar had a lot of experience in sports car racing, so it should have been a bit easier for them than for Ford. It is indeed nice to wonder what if...
     
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  3. mantasisg

    mantasisg Registered

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    New version and ready for Le Grand Circuit 1967 !

    Top speed 341km/h without slipstream, perhaps a bit towards "too quick", adjustable later. Car feels very light at top speed, and not too stable - as intended. Use Final gear ratio 3.33. Much fun, 3'26 laptime as for now. Don't die at the kink ! I spun and went backwards at high speed and nearly flipped, as intended :D

    Adjusted a bit more grip for fronts, and a bunch more grip loss for overheating at front. Tiny bit less overheating grip loss at rear.

    About 5percent less engine braking.

    Delete old package and car files, instal new one: https://www.mediafire.com/file/f94mxi51fv19p62/jaguar_XJ13_01.rfcmp/file

    I am really missing headlights now lol
     
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  4. woochoo

    woochoo Registered

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    I think the Howston G4s I modified to be suggestive of a Ford MkIV get 341-342 without a tow, so it's nice that they'll finally have some company all the way to the kink :) The MkIV having a 7L / 427 engine
     
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  5. Godwind Racing

    Godwind Racing Registered

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    Love to have the GT40s, Ferrari 250 LM and the Porsches 904, 906, 907, 908 and 910 brought in one day. HistorX has the GT40s, 904, 906; CSGT has the other Porsches
     
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  6. mantasisg

    mantasisg Registered

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    I would not be against of having those cars :D
    One of the cars from same era which is under my radar is this
    [​IMG]
    30:00 starts in FOS
     
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  7. Alex72

    Alex72 Registered

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    I started looking at the Ferrari F40 again. Just as a personal Project anyway. The one i was making Before disappeared when my HD wrecked but i hadnt come very far anyway. Now with new Blender which is much more sleek and faster to work with maybe it can be done. I have a bunch of cars i want to do but gotta get over that bump of Learning to model properly first. :D
     
  8. jimagn

    jimagn Registered

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    I get this error message from Mediafire:
    "Download not available
    This file can not be downloaded because there was a problem with the upload. If possible, contact the person uploading the file to ask them to upload it again."

    BTW I just tried Goodwood with your first posted version of the XJ13 and was able to get similar times to what you recorded. However I made setup adjustments similar to what I made at Rouen. If you notice your actual tire temps at the end of a straight (so the tire temps "settle down" and don't just tell you a temporary surface temperature) after a few laps, you'll see that even after reducing tire pressures as low as they will go, the tires are still hotter in the middle than at either edge even after adjusting camber. That's why I reduce tire pressure. Otherwise the center of the tread is always way hotter than the edges. I hope this makes sense.

    Can't wait to try the updated XJ13. :)
     
    Last edited: Feb 26, 2019
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  9. mantasisg

    mantasisg Registered

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    Thank you for feedback :)

    I'll reupload later today when I will be on my simracing computer.

    As for tires temperatures, I don't think temperatures ever settle down till car stops and stands still, or rolls very slowly. We still only see surface temperatures in tire monitor. Naturally while going straight tire mostly works at the middle if pressure is good, also these tires has significant expansion with speed and I suppose most expansion happens at the middle, in corners you should see outside edges surface heat up if you use tires to the limit, if in turns whole tire heats up then it means camber is about right. It would still be interesting to check core temperatures, is there such function in rF2 ? Would be interesting to make a pitstop and get an info about tire pressures changes and core temperatures.

    Also I again forgot to try minimum tire pressure... I don't even kow what it is by now. But afaik cars usually does not have an option for ridiculously low tire pressures in rF2, so perhaps there are simply a range of logical pressures for cars and you can't have them that low that it would ride on sidewalls. It will be interesting thing to try today.
     
  10. mantasisg

    mantasisg Registered

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    Reuploaded: https://www.mediafire.com/file/deau98xrjrudbid/jaguar_XJ13_01.rfcmp/file

    I have also checked tire pressures now. It is shame to admit but I didn't pay much attention on them before, and they are a bit on lowish side already, being a legacy from Howston G4 they are too low, because Howston G4 is lighter car.

    I tested lowest pressures and improved my previous laptime by two tenths. Car was very slugish. Then I checked pressures higher than default, and improved low pressures laptime by half a second. Car was much sharper, but also more sensitive, it was easier to loose time with mistakes. I guess lower pressures are simply more forgiving.

    Car now is just tiny bit too powerful, I think.
     
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  11. jimagn

    jimagn Registered

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    Thanks for working link and tire clarification. I don't think there is a way to check core temps in rF2.
     
  12. mantasisg

    mantasisg Registered

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    As soon as I looked up for them, found them immediately. Funny thing how we miss such obvious things when we just don't look for them. I added red tone for them in this picture, so they are more apparent. You have all the info you need - real time pressure +, real time tire load +, real time Inside,Middle,Outside temperatures. And also brakes wear :)

    This is not from Jaguar
    [​IMG]
     
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  13. mantasisg

    mantasisg Registered

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    Having quite an awesome go with physics, learning a lot of things, really love rF2 and how physics are, physics are more complex, everything is just more, but I also find them more intuitive to work on, and more flexible.

    Big big thanks for @Bumble for best feedback that could be made. I still have to install Motec and the plugin and go through the data, that is incredible to me.

    I have made a jump into a geometry and suspension world lately, turns out it is not so impossible to understand. The challenging thing is accuracy and having it correct. Thanks to beautiful Leonardos physics modding tool I was able to visualize my changes, and how they affects camber gain/toe gain I could get pretty awesome results. As for anti-dive, anti-squat, and F/R anti roll geometrical stiffness, they are very approximate now, but feels great, perhaps have too little anti dive as fronts seems to lock a bit easily under braking in some times. Also in a special places car feels like it suddenly turns in harder, this happened in Oulton Hairpin mid turn, then I realized that I had too much rear wheels bumpsteer, thanks to Leonardos tool could made it to be very minimal. Later in Miseluk I had similar problem in a place where you enter a highway in fast narrow right hander, it is like if inside wheels had more traction at very instant moment under great compression. So it is interesting to work on those things. I also found it interesting who easily I could modify mechanical trail, I can easily make FFB to "fall-in" when car understeer (the effect that everyone freaks out about, but still I see people asking for understeer sliders in FFB options of the simulators), I can adjust steering to be more pneumatic trail sensitive, adjust scrub radius... so much things...

    Right now my geometry is not something in particularly great, I have to do some drawings to know precisely where all the centers are, how big are all the moment arms, how the forces travel through the chassis that makes it do things that it does. Also have to watch a lot of YT videos lol, and have a lot of reading. My values are now quite low decimal accuracy and yet to be tweaked, I see original values in the base PM which I use are like 5-6 digits decimal accuracy lol thats insane who would ever have this crazy manufacturing accuracy for whole chassis IRL ? :D And in 60s.

    The car pretty much uses front suspension of an E-Type. Rear end is more complex.

    Thanks to Building The Legend project, this car mod was made possible. Building the legend is making the replica of Jaguar XJ13 in original 1966 specs.

    Thanks to it I could see beautiful things like this:
    [​IMG]

    It definitely helps for me. I am also able to use 3D modeling to locate the points more accurately and reduce the guesswork. Still tweaks are necessary to make things to function as they should.

    By the way, one more interesting thing. I have found that historic racers these days are slightly faster, so if I aimed for reference best laptime at Goodwood to be 1'21 before. Now I have it lifted to 1'22-1'23. Still wondering maybe I should lower it slightly again, since car uses after crash setup - wider tires, for example. Late sixties cars seems to be less faster than they were in their time, and 50s cars such as Dtypes seems to be more faster, like they were ~1'33-1'36 originally, but in GW revival sub 1'28 has been done. However, Ferrari 250 GTO best laptimes in Revival and in 1964 are matching. Jim Clark did 1'20'8 with Lotus-Ford 30, Lola T70 was still in early stage though, but in this era sub 1'18 has been done...

    By the way, I am also very interested in 50s cars, and working on Woochoos 1954 Endurance mod, to make physics sharper on the subject. Currently was spending quite a lot of time on that too.
     
    Last edited: Mar 4, 2019
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  14. jimagn

    jimagn Registered

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    You have been busy! Sounds like you're enjoying it though. Your expertise is impressive. Thanks for trying to be accurate and period-correct. Can't wait to see the next iteration.
     
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  15. mantasisg

    mantasisg Registered

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    Having a blast discovering things about geometry, Jag now has almost totally unique geometry, except pushrods of suspension, because I got a bad crash when I edited them, I also didn't touch chassis.ini because I don't really get what is going on there, seems like it is automatically generated probably with some specific tool ? Suspension.pm is pretty much nailed, perhaps not super accurate as real thing, but it has to be really quite similar, I even got it to perfect IMO, car was handling so well that it was unbelievable to me, then I added a tiny bit of bumpsteer (toe gain is bumpsteer right?) grain back. Interesting thing about front camper gain, gains camber under compression, but stays neutral under extension. The car uses front suspension set of an Etype, which is front midengined car, is it logical that it would have too stiff geometry for a rear mid engined vehicle ? because I found out that I need considerably softer front ARB to make it neutral ? I like the car which is on the edge of understeer/oversteer when driven on the limit.

    Rear end geometry is a bit weird in terms of upper rear link, as the driveshaf seems to do that work. Didn't really followed that one to be very identical.

    Car driver great. Except bankings of Brianza, maybe there was a reason why they used chicanes and bus stops these years :). Can't wait to continue on it soon. Meanwhile, also have some work with other cars.

    And just my idea about "perfection".

    I also realized that I could be wrong about decimal accuracy (though it is obviously accuracy if numbers are dead same). Basically I realized that having 2-3 numbers after decimal point is exactly extremely accurate ! How on earth you could make all points to be 0.115000 away from reference point, and then exactly 0.115000 on the other side of the car. I think it is reasonable to say that real values would be something like 0.115154 and 0.114956, completely random distance in some theoretical error, which would be 0.2mm in this case. I would suppose that over very hard beating and curbs riding these errors could grow 2-4 times. And I suppose older technology had greater manufacturing errors. Not that it would change vehicle handling a lot, but would be noticeable, I'd say. I don't know if there are cases where a deviation of a millimeter would ruin the geometry, probably not.

    On the other hand you can reach absolutely accurate theoretical build and thats an advantage, however I would suppose that total accuracy is impossible. For example I would like to have left and right tires different in size by a millimeter or so and weights different by few grams , but perhaps that wouldn't make a difference, as different pressures are hardly noticeable. But I think it should add tiny bit of longitudinal instability. But maybe thats overthinking.
     
    Last edited: Mar 6, 2019
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  16. mantasisg

    mantasisg Registered

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    New physics. Rebuilt a lot, tried to keep essential way of how car handles. You'll find front arb rather soft for less understeer. A lot of settings for arbs for testing.

    Latest tweaks were on aero, don't want to make it flip at mulsane crest, but at the same time I want the car to feel on the edge of control when on crests, I think not without a reason days of downforce were dawning at that time.

    Please enjoy it, I find it very good now, but I can't cover everything so please give me feedback.

    Link (I call it 015 now)
    https://www.mediafire.com/file/2gj48p0kgvidis8/jaguar_XJ13_015.rfcmp/file

    A pic of real one, for colours and better taste:
    [​IMG]
     
    Last edited: Mar 6, 2019
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  17. jimagn

    jimagn Registered

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    Good work. Thank you. I tried it at Belgium and couldn't get rid of understeer on corner entry. Maybe just a bad driving day for me. :D
     
  18. mantasisg

    mantasisg Registered

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    In lower and medium speeds default setup is very neutral. At high speeds aero lift is a thing that challenges.

    You shouldn't be able to take them flat out there I guess, haven't tested there yet.

    I wonder could this splitter type of thing help a bit with front stability, or is it just to help to feed radiator more efficiently.
    [​IMG]

    Edit:

    On the second look, you can see that air escape vents are at the top of the bonnet, I also know that radiator is mounted in angle, this means air is directed upwards and should create some counter clockwise momentum generating a little bit of downforce. Am I thinking right ?

    picture from Neville Swales project:
    [​IMG]

    Though even if the element generates some negative lift, it still doesn't mean that front overall lift would not be positive.

    I have just dabbled with Aero so far. I also set up car so that front is a bit higher. And lift sensitivity too height is not the smallest, I think. So perhaps for highspeed track it would be usefult to lower front end ? Try that.

    By the way, anyone could try to guess why there is duct on the front bonnet ?
     
    Last edited: Mar 8, 2019
  19. jimagn

    jimagn Registered

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    Lowering the front is a good idea for high speed corners. Thanks. Might that duct be for driver cooling?
     
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  20. mantasisg

    mantasisg Registered

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    Will have to test myself too, I already got feedback about some strange aero behavior at some instant. I don't want the car to feel super planted, but don't want glitchy behavior too lol

    Good idea about driver cooling, there seems to be little opening where steering mechanism is. I also thought that it could be some sort of airflow redirecting away from window wiper, I suppose drag could break it, also drag is slowing down the car.

    Malcolm Sayers designer of the car was very strict about drag, Jaguar people wanted to put on Jag sticker on the front, but Sayers insisted that it would be painted haha

    @jimagn I have tried 60s SPA, I see how important is not to come in too fast. I have totally died once. I think the car is not that bad in terms of high speed understeer, if you simply don't go in too fast. Too bad there they had a brick wall right next to exit apex, and those tiny weightless hay bales didn't help lol I think it is kool if you take it gradually faster in classic spa, going over the limit and then readjusting for a bit slower speed for next lap doesn't really work there, because usually there is no second lap. However, I have spotted on real issue there, AI were 100% flying off at La Carriera.
     
    Last edited: Mar 10, 2019
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