Jump to content


An Unified 1967X International League?

13 Dec 2018

Posted by mcmirande in GPL-"Hey, anyone need a racer?"
Hello everybody

I noted that there are several enthusiasts of the 1967x mod world-wide, but we're geographically distant each other, which reduces the grid sizes.

I was thinking that maybe we, interested in racing this mod, could do some "ad hoc" league to do it with full grids in some consensed day/hour allowing people to race together.

I thought in a loose schedule of about one race a month or every 45 days during 2019. I would like to race them in pro mode and 60fps, but everything may be adjusted according to the preferences of the drivers.  The hosting and GPL-Weekly reports will not be problems (I could manage both things unless other guy were willing to do it).

At first, I would like to know who would join the league, in order to think about all details after that. I think it wouldn't make sense if we were 10 or less drivers for race.

Well, comment in the thread if you think you (or some other driver without SRMZ account you know) would join it.

Cheers and hoping see you on tracks ;)


  187 Views · 6 Replies ( Last reply by mcmirande )


Gpl Salisbury Limited Slip Differential

13 Dec 2018

Much has been written over the years here at SRMZ about car differentials and how GPL models them.  The vast majority of this information has been good, but there have also been a few inaccuracies and some misunderstandings.  This post is an attempt to clear up some things.

1.  The purpose of the differential is simple--it permits two wheels on the same end of the car to rotate at different speeds.  This makes it easier for the two tires to negotiate different radius curves when the car is turning a corner.

2.  Several different types of differentials have been developed.

A.  Open--this type allows the two wheels to rotate at different speeds at all times as they are never locked together.  Consequently, it handles corners very nicely.  Its main drawback is that if one tire is slipping on a slick surface such as ice, all the engine torque is directed to that wheel while the other receives little or no torque.  As a result the slipping tire spins while the other doesn't spin at all and the car won't move.  The open differential is rarely seen on race cars although it is almost universally used on passenger cars.

B.  Locked--this type is the complete opposite of the open differential.  The two wheels are always locked together and rotate at the same rate.  It is commonly used on trucks, dragsters, and karts.  Locked differentials are rarely, but sometimes seen on race cars as they promote understeer.  The 1970s Porsche 917 Turbo CanAm cars used a locked differential as other differential types of that era could not handle the car's massive torque.

What is really needed for a race car is a differential that is open for entering the corners and locked for exiting the corners and maximum acceleration on the straights.  The limited slip differential (LSD) was developed to accomplish these goals.  The two LSDs that apply to 1960s race cars and GPL are the Cam and Pawl and the Salisbury.

C.  Cam and Pawl LSD--this type uses a set of plungers (pawls) that move to lock the two wheels together completely when power is applied to the differential.  When power is removed, the plungers retract and the two wheels are free to rotate independently of each other.  The Cam and Pawl is one of the simplest forms of LSDs and is relatively cheap and reliable; however by its very nature, the plungers tend to wear quickly and have to be replaced often.  Also, the locking action is relatively quick so essentially it is either completely locked or completely open.

Cam and Pawl LSDs were used on all F1 cars of the 1960s.  Hewland in England and ZF in Germany manufactured their own versions of the Cam and Pawl LSD.  David Wright researched the subject and determined that the first use of a LSD other than the Cam and Pawl didn't occur until Ferrari used a Salisbury type LSD on their mid 1970s F1 cars.

This is all well and good, but strangely GPL does not model the Cam and Pawl LSD; rather, it models the Salisbury.

D.  Salisbury LSD--this type uses ramps and a series of clutch plates to lock the two wheels together.  The advantage of the Salisbury is that the amount of lock is individually adjustable when the power is applied and when removed.  Also, the two wheels are locked together up to a certain point, then are free to rotate somewhat independently.  The locking action is more progressive than with the Cam and Pawl.  By all accounts, the Salisbury is a vast improvement over the Cam and Pawl.

3.  GPL Salisbury LSD Model:

A.  GPL models the Salisbury LSD fairly well.  The player setup menu contains settings for the ramp angles for "power" and "coast" and the number of clutches.  These settings are applied to a formula to determine a "locking percent".  GPL's code continually keeps both wheels/tires turning at the same rate by apportioning torque from one wheel to the other; however, when the torque difference reaches the locking percent limit, the two wheels begin to rotate independently of each other.

B.  The formulae for locking percent are:

Power Locking Percent = Cosine(Power Ramp Angle) * (Number of Clutches + 1) * 5%
Coast Locking Percent = Cosine(Coast Ramp Angle) * (Number of Clutches + 1) * 5%

Note that ramp angle and number of clutches both contribute to the locking percent calculation.  Therefore, it is possible to have the same locking percent by using different combinations of ramp angle and number of clutches.  Figure 1 shows the locking percent for various combinations.

Note that the number of clutches affects both power and coast locking percent.

GPL Setup Manager displays locking percent according to these formulae.

C.  As best as I can determine from reviewing GPL's code, the car handles the same when using the same locking percent regardless of the ramp angle and number of clutches.  The ramp angle and number of clutches values are not used anywhere else in the code.

D.  The power locking percent is used when the player's throttle is on by any amount.

E.  The coast locking percent is used only when the player's throttle is completely off!  This has a major implication for left foot brakers as they will be using the coast locking percent only if they completely remove their right foot from the throttle pedal.  It's all too easy to keep a slight amount of pressure on the throttle pedal which causes the power locking percent to be used inadvertently.

F.  Disregard any reference to what real world cars used for ramp angles and number of clutches.  They may or may not correlate to what GPL needs for a good handling car.  Years of practical experience with GPL has determined that power ramp angles between 60 to 85 degrees, coast ramp angles between 30 to 45 degrees, and number of clutches between 1 to 3 can be used depending on the car characteristics and the player's skill level.  These values correspond to locking percents of 1% to 10% for power and 7% to 17% for coast.

Note that some "alien" drivers may use locking percentages that are different than these.  If you are an alien, you probably don't need to be reading this in the first place.  :)

  211 Views · 9 Replies ( Last reply by Lee200 )


Slowing The Ai In 67's

10 Dec 2018

I know that it's been asked before and probably by me. So apologies for asking again.

Can someone give me a qiuck synopsis of how to slow down the Ai in gpl 67. I'm not a fast driver and believe that gem can only alter the mod cars speed and not the 67's.

I would just like to be a bit more competitive at the back of the field, or maybe in midfield.

Thanks all :up:


  548 Views · 26 Replies ( Last reply by JonnyA )


Sandown 1968

12 Dec 2018

Posted by ginetto in GPL-Track Database
Sandown 1968 Round 7 of the Tasman Series

By Neil Lowe. ©2006

Credits :
  • Track mesh, objects, original textures and AI - Neil lowe
  • Sky - Scotty
  • Original program cover supplied by - David Shaw
  • Retouched program cover and mapset - BAPOM (John Bradley)
  • Additional research and info - GPL Tasman Mod team
  • Alpha and Beta testing leads - Paul Gatt and Ross Candido
  • Additional Beta testing - GPL Tasman Mod Team, Sandra Knight and OZ Races
  • Absolute patience and immeasurable understanding - Mandi Lowe
  • Information on the real track can be found at http://www.tasman-se...-series.com/  - The finest Tasman Series Website on the planet.
This is the "Standard" version of this track. It contains 98% 4bit textures and has been tested in D3d and OpenGL. It is also 100% Voodoo compatible.

  210 Views · 3 Replies ( Last reply by gliebzeit )


Proper Triple Screen Support :o

09 Dec 2018

So, i was under the impression that there were no proper triple screen modifications and the only possibility was to use something like eyefinity or nvidia surroud with the crappy single viewport over 3 monitors triple screen.
However watching this youtube video (recorded around 2002 no less!) shows a version of GPL with proper triple screen support with separate viewports for each screen. Notice how the angle changes on the angled side screens.


This appears to be done on multiple computers with the sidescreen computers each running copies of the game and spectating (does that mean it is only available for online play?). Details are short on the video.

Anyway, i never knew GPL had been modified in this way, proper triple support from a single instance on a single computer would be great. Obviously the FOVs, angles, positions of each screen would have to be configured in an ini file or something, but that would be great.

I just saw this randomly on youtube and was surprised! Especially considering how old it is and that i'd never heard about it properly or realised it was actual independent viewports.

On a side note, it's really annoying that that assetto corsa mod has called itself "grand prix legends" as it is making gpl content harder to search for. Just try searching on youtube for grand prix legends and sorting by date order for example. They really should change the name…

  273 Views · 6 Replies ( Last reply by robwmack )

Latest Donations

  • Lalethor ( $ 15.00 )
    Dec 02 2018 - 05:07 AM
  • webfoot ( $ 25.00 )
    Nov 18 2018 - 09:01 AM
  • Anonymous ( $ 25.00 )
    Oct 31 2018 - 06:14 AM
  • Offline Donation ( $ 15.00 )
    Oct 23 2018 - 04:41 AM
  • t3r ( $ 25.00 )
    Oct 16 2018 - 09:00 PM

Latest Discussions

Online Users

14 members, 123 visitors and 1 anonymous users

Bing, aolas68, Google, tikfas, Stefan Roess, Rich65, Strava, TvO, G.Spinning, italianracer, Andy Clegg, Wally55, Paddy the Irishman, BlackMax1992, Richard McC, Brett77

Portal v1.1.0 by DevFuse | Based on IP.Board Portal by IPS

Sim Racing Links