I have the URD mods for assetto corsa and love them. Is it worth me buy them for rf2 as well? How does it compare to AC. How is the egt mod in comparison to the BES 1.0 mod?
How is the URD mod for rF2?
- Thread starter Greg Latty
- Start date
David O'Reilly
A bad quali means I can go forwards in the race.
Hi Lgel.
I was pretty balanced with my views that many like the URD GTE and it was just a preference of mine that I dont. Thats just an opinion I guess.
Re the Darche.
I have read the same article that you quote here. However it seems very hard to find an actual weight distibution on the current model.
http://www.racecar-engineering.com/cars/porsche-991-gte/
On close reading of the changes we see that:
The engine is unchanged (the rear-most heavy part in the 911)
The lighter gearbox actually lives near the middle of the car so won't have a huge effect on weight distribution IMO.
The other changes including carbon fibre panels and light weight windows occur everywhere not just at the rear. In fact there are more bits forward of the rear axle to lighten so while overall weight is lower its not a big change in distribution.
The one item that would help is the new transaxle that allowed Porsche to move the engine very slightly fwd but it still hangs over the rear axle.
The lighter battery lower weight at the front.
Ironically the lowering of the overall weight makes the engine position more problematic. Bit like in the final scene in the Italian job, if a couple of the bank robbers hopped off the bus.
So the literature claims a lowering of centre of gravity but doesnt specifically say a movement forwards of weight distribution.
But lets say we allow it 1 (or 2% which is HEAPS) when the big heavy bits are still at the back.
I have the figures for the real world 2009 GT3RS its Front 38.5 / rear 61.5
The BES 911 GT3 which feels about right* is Front 41/ rear 59 C of G = 0.275m
The URD Darche is Front 44/ rear 56 C of G = 0.31m
Now even if Porsche performed miracles and got a 2% fore aft weight distribution change its still less than 41/59.
They didn't make it a mid engined car with a V engine (which sits much higher). Its rear mounted and its a flat 6 which with dry sump (no sump) it sits on the floor and also has huge implications for the C of G.
The numbers dont lie. But I started on my investigations because the car just felt wrong.
In a 911 if you have a little bit of steering lock and brake hard you will quite suddenly be facing the wrong way. Its all due to polar inertia. The heavy rear end will just obey Newtonian physics and attempt to keep travelling where it was travelling before hand. If the rest of the chassis is not perfectly aligned under brakes it will slow and farewell the rear as it passes. Thats what 911s do. The Darche behaves like a mid engined car. It just slides it doesn't swap ends. So i started digging and the numbers above are the result.
The C of G is also too high. It cant possibly be essentially the same as a mid mounted V8.
Have a look at a Ferrari engine position and the 911. It cant be the same.
Conclusion:
I appreciate that you took the time to cite a reference to enlighten me but my central point remains the same.
In my view the Weight distribution and C of G in the Darche at exactly the same as the Ferrucio are just plain wrong (if it wants to be a 911 GTE anyway) . It might be a nice car, (hey people like it) but its not anything like a 911.
If URD saw fit to fix it they would possibly have something very unique (which is what the 911 is)
Sincerely
David
* I have driven the 911 GT3, 911 Turbo and early 911s on race tracks in timed events. The one thing thats very evident is the mass at the rear. I have also driven Ferrari 355, 360 on many occasions on public roads.
Hello David,
Interesting reading, I understand and respect your point of view, and it's not my intention to start a silly discussion as those so frequent on ISI forums.
I trust Porsche when they say "One of the priorities in the development was the more evenly balanced weight distribution" to achieve their objectives.
I still believe that in real world, a works Porsche GTE has an incredible road holding (perfect tuning) and isn't significantly harder to drive at the limit for a professional driver than a Ferrari F458, if not the results of endurance races would be very different.
An AM GTE due to BOP rules is allowed around 100 HP more than a Porsche (source Porsche) and end with comparable lap times.
But, and this is a great but, URD cars are made to be raced in leagues, and what you would see if one car was much easier to drive than the others for the same lap times, would be a monotype series.
I feel that RF2 has already to many monotype series.
For me a very limited pilot, a Darche at Suzuka is difficult enough to drive with the type of setups I design (little wings, equal temps between front and rear axles, that don't allow driving errors). Suzuka setup still a WIP for me.
Cheers.
P.S.
And I have also driven an historic Porsche turbo (no abs, no traction control in this time, big turbo lag) on wet roads (better know what you are doing and drive according to your limited abilities).
Interesting reading, I understand and respect your point of view, and it's not my intention to start a silly discussion as those so frequent on ISI forums.
I trust Porsche when they say "One of the priorities in the development was the more evenly balanced weight distribution" to achieve their objectives.
I still believe that in real world, a works Porsche GTE has an incredible road holding (perfect tuning) and isn't significantly harder to drive at the limit for a professional driver than a Ferrari F458, if not the results of endurance races would be very different.
An AM GTE due to BOP rules is allowed around 100 HP more than a Porsche (source Porsche) and end with comparable lap times.
But, and this is a great but, URD cars are made to be raced in leagues, and what you would see if one car was much easier to drive than the others for the same lap times, would be a monotype series.
I feel that RF2 has already to many monotype series.
For me a very limited pilot, a Darche at Suzuka is difficult enough to drive with the type of setups I design (little wings, equal temps between front and rear axles, that don't allow driving errors). Suzuka setup still a WIP for me.
Cheers.
P.S.
And I have also driven an historic Porsche turbo (no abs, no traction control in this time, big turbo lag) on wet roads (better know what you are doing and drive according to your limited abilities).
Last edited:
David O'Reilly
A bad quali means I can go forwards in the race.
Hi @lgel
I dont think we are really in much disagreement at all. Also there is nothing to fear from a principled discussion on line between enthusiasts
On handling.
I totally agree with your statment...
My subltle point is that the 911 is driven with a slightly different technique due to its weight distribution. Once mastered its very effective. The top pros use it to their benefit.
I quote the respected US road and track publication in its piece on the 911 RSR.
30th April 2012.
"Patrick Long is a study in concentration, finely modulated aggression and economy of movement as he wrings out the high-performance sponge that is the production 911 GT3. Reflexive steering inputs arrest mid-corner twitches of yaw almost before they happen. His right hand darts from wheel to shifter to wheel again in milliseconds, recalling those slow-motion biology films where a frog zaps a hapless insect with a flick of its tongue. And always, always to the throttle early, taking keen advantage of the Porsche's tail-heavy weight bias and sticky, wide Michelin Pilot Sport Cup tires to stabilize the chassis mid-corner and rocket out of turns. It's as if he's always two steps ahead of the car, precisely why he's a Porsche factory driver and I'm not."
and
By the team's own admission, its GT3 RSR isn't the fastest car out there, but it may have some advantages in corner entry, exit and managing the tires. Says Long: "A lot of it is utilizing the differential to turn the car, where going to the throttle in a lot of the other cars could create understeer on exit. We can also trail-brake quite a bit, which has helped us overtake during the race...with the engine in back we can load the nose and not overpower the front tires." Spoken like the true champion he is."
This different style of driving is the unique flavour and allure of the 911. Once mastered its incredibly satisfying. To get that pendulum swing just as much as you want and no more with a tiny bit of lock under trailing brake then control it with the slightest of opposite lock and early and progressive throttle.
I can remember 18 months ago in the corner with no name after Rivage at Spa doing it in the BES 1.0 911 GT3 and a big smile broke out on my face and I said out loud "it is a 911 "
This style is needed on the 911 as well as being perfectly perpendicular to the braking forces when braking hard from high speed.
There is a benefit to be gained from braking progressively. The initial bite transfers the weight forwards to the fronts allowing them to bear much more load. Now the uneven weight distribution is an ally as the rears remain far more loaded than a mid or front mounted engine. This is the secret to the stunnig braking performance of the 911. Simply put the rears can do more work.
BOP and league Racing
I accept your point that the cars need to have similar performance for multiplayer or only one car would be chosen. That's exactly why I havent been pedantic about weight and drag co efficient. This is of course how BOP is managed. But I do believe we are wanting the same thing when you make you point about a mono type series.
I just want the 911 to be what it is. That little bit different and true to its favour embedded in its engineering roots.
David
I dont think we are really in much disagreement at all. Also there is nothing to fear from a principled discussion on line between enthusiasts
On handling.
I totally agree with your statment...
.
My subltle point is that the 911 is driven with a slightly different technique due to its weight distribution. Once mastered its very effective. The top pros use it to their benefit.
I quote the respected US road and track publication in its piece on the 911 RSR.
30th April 2012.
"Patrick Long is a study in concentration, finely modulated aggression and economy of movement as he wrings out the high-performance sponge that is the production 911 GT3. Reflexive steering inputs arrest mid-corner twitches of yaw almost before they happen. His right hand darts from wheel to shifter to wheel again in milliseconds, recalling those slow-motion biology films where a frog zaps a hapless insect with a flick of its tongue. And always, always to the throttle early, taking keen advantage of the Porsche's tail-heavy weight bias and sticky, wide Michelin Pilot Sport Cup tires to stabilize the chassis mid-corner and rocket out of turns. It's as if he's always two steps ahead of the car, precisely why he's a Porsche factory driver and I'm not."
and
By the team's own admission, its GT3 RSR isn't the fastest car out there, but it may have some advantages in corner entry, exit and managing the tires. Says Long: "A lot of it is utilizing the differential to turn the car, where going to the throttle in a lot of the other cars could create understeer on exit. We can also trail-brake quite a bit, which has helped us overtake during the race...with the engine in back we can load the nose and not overpower the front tires." Spoken like the true champion he is."
This different style of driving is the unique flavour and allure of the 911. Once mastered its incredibly satisfying. To get that pendulum swing just as much as you want and no more with a tiny bit of lock under trailing brake then control it with the slightest of opposite lock and early and progressive throttle.
I can remember 18 months ago in the corner with no name after Rivage at Spa doing it in the BES 1.0 911 GT3 and a big smile broke out on my face and I said out loud "it is a 911 "
This style is needed on the 911 as well as being perfectly perpendicular to the braking forces when braking hard from high speed.
There is a benefit to be gained from braking progressively. The initial bite transfers the weight forwards to the fronts allowing them to bear much more load. Now the uneven weight distribution is an ally as the rears remain far more loaded than a mid or front mounted engine. This is the secret to the stunnig braking performance of the 911. Simply put the rears can do more work.
BOP and league Racing
I accept your point that the cars need to have similar performance for multiplayer or only one car would be chosen. That's exactly why I havent been pedantic about weight and drag co efficient. This is of course how BOP is managed. But I do believe we are wanting the same thing when you make you point about a mono type series.
I just want the 911 to be what it is. That little bit different and true to its favour embedded in its engineering roots.
David
Hello David,
I 100 % agree with your post, which is informative and fact based.
And yes, you can say , I am a racing car enthusiast.
I have spent some hours with the URD mod, and to me the Darche doesn't drive as the F458.
My current setup at Sebring and Suzuka for the Darche uses near min rear wing setting, I don't know if it is the faster, but is the one that gives me the higher driving satisfaction (what I care about).
Thanks for your time.
P.S.
Drove the Blancpain 911 just after URD at Sebring.
I agree with you, it's a pleasure to drive (much less understeer). But the undertray catches invisible objects on the track (at least the version I have 1.5, and not at every lap), in the esses before the main straight. I tried a setup which rode higher but it still occurred from time to time. Do you have a version not affected by this problem?
I 100 % agree with your post, which is informative and fact based.
And yes, you can say , I am a racing car enthusiast.
I have spent some hours with the URD mod, and to me the Darche doesn't drive as the F458.
My current setup at Sebring and Suzuka for the Darche uses near min rear wing setting, I don't know if it is the faster, but is the one that gives me the higher driving satisfaction (what I care about).
Thanks for your time.
P.S.
Drove the Blancpain 911 just after URD at Sebring.
I agree with you, it's a pleasure to drive (much less understeer). But the undertray catches invisible objects on the track (at least the version I have 1.5, and not at every lap), in the esses before the main straight. I tried a setup which rode higher but it still occurred from time to time. Do you have a version not affected by this problem?
Last edited:
David O'Reilly
A bad quali means I can go forwards in the race.
Ill check which I have and let you know.
Hello David,
did you try to adjust the weight distribution of the darche in the setup-settings? It allows you to set the weight distribution form 44:56 up to 39.5:60.5. I personally drive the Darche with a 40.5:59.5 setting and it drives in my opinion very darchy.
By the way i think URD should set the front-heaviest (default) value up to 42:58.
Regards
did you try to adjust the weight distribution of the darche in the setup-settings? It allows you to set the weight distribution form 44:56 up to 39.5:60.5. I personally drive the Darche with a 40.5:59.5 setting and it drives in my opinion very darchy.
By the way i think URD should set the front-heaviest (default) value up to 42:58.
Regards
David O'Reilly
A bad quali means I can go forwards in the race.
No I havent, thanks for the idea. I will try it.
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