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Mod Specific Diff Settings (65 Mod In Particular)


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#1 stuboyle

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Posted Apr 06 2021 - 07:27 AM

So after all these years I'm going to buckle-down and understand what the damn diff is doing!  I'm relying on the advise and calculations of the "GPL Car Spreadsheet".  Unfortunately, I don't recall where I got it.

I'm looking at this advise about Brabham versus BRM, etc., then it occurred to me that you have significantly less power in the 65 mod than 67 and that should have implications with the power lock side of the diff setting.  All else being the same, it would seem you want a looser (not loser :) ) power lock diff on a 65 car than 67 because you have less power.   Does that make sense?

On the coast lock side, it wouldn't seem to make as much of a difference.  Though, the 65 cars are lighter than the 67 cars.

Any thoughts or comments on diff settings by mod?

Thanks,

Stuart

#2 MK3424

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Posted Apr 06 2021 - 08:21 AM

ErikGPL made a video about what diff settings do:

https://www.youtube....h?v=awLhSsy5IqY

#3 PTRACER

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Posted Apr 06 2021 - 09:11 AM

My diff settings don't change from mod to mod.

45/30 with 2 clutches. Everything else I tweak in the suspension.

#4 stuboyle

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Posted Apr 06 2021 - 10:58 AM

 PTRACER, on Apr 06 2021 - 09:11 AM, said:

My diff settings don't change from mod to mod.

45/30 with 2 clutches. Everything else I tweak in the suspension.

Hmmm.  Does the 65 mod have same low speed understeer behavior/problem as the 67 base?

Edited by stuboyle, Apr 06 2021 - 11:01 AM.


#5 Millennium

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Posted Apr 06 2021 - 11:20 AM

The original 1967 cars have much less grip at lower speeds than any of the mods.

You can (and probably should) use much looser diffs with the 1965 cars, because it gives much more agility while not being that much harder to control.
If often used 45/60 with 1 clutch for race setups, and 30/85 1c for hotlap. (the latter can cause high tyre temperatures)

#6 stuboyle

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Posted Apr 06 2021 - 12:33 PM

I calculated all the locking percent for all the combinations in Excel using the formula:  COS(Angle) X (Number of Clutches +1) X 5%.

It's useful for comparing setups with different clutches.  Though I don't notice much difference between 60 vs 55 or  even 60 vs 50.


Posted Image

Edited by stuboyle, Apr 06 2021 - 12:55 PM.


#7 DuncanS

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Posted Apr 06 2021 - 01:47 PM

As I've mentioned once before. Unfortunately there is a grave error in GPL's physics coding which means care should be taken when selecting a diff as this is one of the areas affected. Better to stick with fewer diffs and ramp angle combinations and find something that works, than to go out trying loads of different ones all the time.

Some of the mods appear to hide (neutralize this flaw somewhat), as where there is excessive (greater) grip modelled the effect of the flaw is more hidden. Perhaps this is why some mods have had too much grip designed into them. The '65 mod has too much grip modelled into it, so it is one that masks this bug to a degree. However you can always try harder if you want too.

Edited by DuncanS, Apr 06 2021 - 01:54 PM.


#8 Bo Bruce

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Posted Apr 06 2021 - 02:12 PM

Duncan... i have been racing GPL (95% 67mod) since the orig demo.
(or anyone who feels they have an answer)

i don't know, will never know how a 67 F1 'should' feel :P   closest i've ever come is 2010 goKart on a road course w/ an instructor observing/correcting for 3 hrs!  and it wasn't even a shifter kart :(

my question is when you (or anyone here that talks physics) ... how do you know? not being a smart ass, please don't interpret my 'tone' as being negative, i'm purely curious.
do you read about how an F1 car SHOULD feel? are there charts (like Stu Boyle's above) that can be used and compared with charts from 67? were there such in 67?

i'm always amazed at the intelligence of the GPL community when it comes to 'feels right/wrong'.....  but where does that knowledge come from? Surely we can't compare modern (any) cars- right?
help me understand (and please talk gentle) what i know about cars is when you turn the key in the ignition and you hear the engine respond, it must be working  :P

thanks...

#9 DuncanS

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Posted Apr 06 2021 - 04:41 PM

It's pretty easy to tell the '65s have too much grip overall by quite some margin, whilst recognising that the modelling of the grip in the mod is compromised in GPL because the physics model had it's limitations (grip is not changing with speed), hence my use of the word overall.

I haven't driven a 1967 F1 car. But I don't think you need to have done so to tell the '65 mod has this grip discrepancy.

A couple of fun videos, Antonio Giovinazzi being driven around the ring by Kimi, both F1 drivers but one completely at ease with the car.

https://www.youtube....h?v=JlD9lbWF5WQ

and Martin Brundle being driven around Fioarano by Kimi. Notice the reaction of Martin compared to Antonio. Some people can feel and are more comfortable at the edge of the grip than others. I know if it was me in the car, I would probably be like Antonio. GPL allows us to not worry about the fear of crashing. With that it makes it much easier to concentrate on what the car we are driving is doing and learn and improve our skills. At least that is what I did. Along with learning about setups and setup changes, characteristics and effects.

https://www.youtube....h?v=DODrROnEHyE

I once got to drive a modern iteration of the VW Beetle that had been race prepared. The most startingly difference to a regular car that I felt was the lack of roll through the corners. It literally remained horizontal to the ground, it was really disconcerting at first. Once you got over the shock of that new sensation, you could then concentrate much more on the car itself. The key thing that stood out to me, was that with the lack of roll it was much easier to concentrate on the tyres and feel when and where you were reaching the limits of the grip than say in a regular car with all the other forces going on. No doubt a skilled and practised racing driver could focus on that sense of the grip limits far better, even if they were driving a regular car demostrating a lot of roll, because they will have had a lot more experience and no doubt developed a far higher level of skill.

I did watch a guy who flew plane simulators, go and fly a real cessna, prep, take-off, circuit and land, first time out (he did have an instructor in the plane with him for safety obviously and did pre-flight checks/tests to show he knew what he needed to know).

Regarding the problem in GPL's physics, it's not easy to discover but I have been able to confirm my findings.

#10 DuncanS

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Posted Apr 06 2021 - 05:46 PM

If you want to test out the '65 mod yourself. Go to Goodwood, throw the car into the chicane before the S/F straight. What do you feel?

Another test if you like, go to Monza get up to tyre temp, brake as late as possible into Lesmo 1 and immediately downshift. What happens?
What should happen is that the wheels should immediately lose traction, the back end of the car would come around and you would head off into the trees or guardrail and end up in a 1000 pieces along with your car. What should also happen is that the engine should blow in an incredible way. None of that happens.

#11 Arturo Pereira

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Posted Apr 06 2021 - 05:48 PM

Of course a green driver would consider the 1965 mod has too much grip. Let´s take the Ferrari brand. The 1967 Ferrari showed 410 BHP and it´s weight was 1129 lb. The 1965 Ferrari showed 225 BHP and it´s weight was 1050 lb. Almost half the power and almost the same weight.
More grip? Give me a break.

#12 DuncanS

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Posted Apr 06 2021 - 05:51 PM

 Arturo Pereira, on Apr 06 2021 - 05:48 PM, said:

Of course a green driver would consider the 1965 mod has too much grip. Let´s take the Ferrari brand. The 1967 Ferrari showed 410 BHP and it´s weight was 1129 lb. The 1965 Ferrari showed 225 BHP and it´s weight was 1050 lb. Almost half the power and almost the same weight.
More grip? Give me a break.

Too much grip. Like I say, do the tests aboves and then say that. Observation is better than blind arrogance to simply numbers. What sensation/effect does GPL produce in game?

#13 stuboyle

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Posted Apr 06 2021 - 05:52 PM

Thanks everyone for your input.  Regarding the accuracy or lack of with regard to the physics, I don't really care, I just want to go fast and beat all you guys :checkeredflag: :)  We all know there a limitations.  Also, the problem with whether it "feels right" is that you can't feel much of anything which is one reason that makes this sim so damn hard.

Edited by stuboyle, Apr 06 2021 - 06:02 PM.


#14 Bo Bruce

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Posted Apr 06 2021 - 08:23 PM

Hey Stu.. that is exactly how i see/feel about GPL :)
you said it about as plain and on the money as it could be said ~




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