gtr is a great simulation but...

tuxy

gtr is a great simulation but its not the best online multiplayer sim racing
it just does not have anywhere near as many features as live for speed

just a few examples

before connecting to a server you can not see if its gt or ngt

you can not restart a race

the reply system is very poor, in live for speed in the replays you could see how much someone was accelerating and breaking in gtr you can not even see speed, gears or revs

there is no official site to upload lap times
there is gtr rank but that is just peoples career.blt file that they have uploaded
that file can be edited in notepad so who knows if the times people have uploaded are correct
in lfs you have to upload a replay to submit a time and anyone could download that replay

in live for speed you can send and receive car setups while in race

im just a bit disappointed because the game is so good but missing allot of the features i enjoy

BlueShaun

yep,
Its because GTR is a mod, an excellent one but just a mod, of F1c, which itself is a slightly improved f12002.

Regarding the features, they are insignificant given that the net code is so terrible.

Im a lot more concerned with the aero model appearing to be a rather loose approximation at best, and the damping appearing to be complete rubbish. I`ve yet to see a GT car bounce for 50 metres on acceleration in real life.

Balfa

What are the most important physics that GTR doesn't model? Or is that something that users aren't really privelidged to, besides conjecture?

Can you give a little more detail on the poor aerodynamics?

BlueShaun

My views on the aerodynamics are based on the F1C hdv files.

They were quite basic models, with 3 lifting elements; the wings and the underbody.

I am fortunate enough to have wind tunnel tested a f1 car, and spent literally weeks analysing the data produced during 6 runs.

The data included information on the car in all pitch and roll configurations, unfortunately yaw wasnt available in the tunnel used( RJ Mitchell....University of southampton).

The most striking element of the test, is the influence of the front wing on the rest of the car. Moving the front wing through its entire range of angles for example, can affect REAR downforce produced by the underbody by up to 9%, things like this are ill accounted for in the ISI engine.

Theres also a big issue with pitch stability in GT racing, producing a model of this (within the constraints of the ISI engine) is next to impossible.

Example, the new chicane at magny cours, hit it hard. GT car flipping at 40mph. Dont think so.

My view is that the whole thing shouldnt seek to model individual influences, but to include an entire aero map as a lookup table. Unfortunately, even sophisticated wind tunnel data aquisition tools cannot record the influence of vertical motion(We were told by Mike Gasgoyne that ferrari can do this though).

Balfa

BlueShaun wrote:

The data included information on the car in all pitch and roll configurations, unfortunately yaw wasnt available in the tunnel used( RJ Mitchell....University of southampton).

You would think that actual_downforce=Cos(angle_of_yaw)*straight_downforce would be a (very) basic model that would suffice. I guess there's no accounting for cross-winds if it doesn't model yaw angle downforce

The most striking element of the test, is the influence of the front wing on the rest of the car. Moving the front wing through its entire range of angles for example, can affect REAR downforce produced by the underbody by up to 9%, things like this are ill accounted for in the ISI engine.

Argh. This is one of the first things i considered about aerodynamics in F1, a long time ago. I'm pretty sure that even Crammond's GP2 models this.

We were told by Mike Gasgoyne that ferrari can do this though).

Heh, i was pretty sure, before the start of this season, that advances in aerodynamics (particularly by ferrari) over the last 3 or 4 years had made them at least as important as tyres. But ferrari's tyres don't seem to be standing up too well this season

BlueShaun

Nope, not at all.
Eg wingtip vortex of front wing, is shed parallel to the flow, so you will find that the force augmentation from ground proximity(of this vortex) goes haywire, while in yaw, or in a crosswind. This is less true of the new high wings, however it is more critical with the new diffusers.



We did a test of a tyrrell wing(straight data above), it could be run at yaw and this was proven to be true.

The force enhancement is due to narrowing of the wingtip vortex core, due to ground proximity. If you know much about the anatomy of a vortex, this causes an acceleration normal to the plane of rotation (at roughly constant helicity) but with increased velocity attached flow under the wing. So more downforce :-)

However, if the vortex is shed away from the wing...it moves into that ugly stall region, at a much greater ride height. But it will only tend to stall on one side. so the downforce is asymmetrical as well as reduced.

As you can see, there are a lot of things happening, and no sim has ever come close to modelling them. Its why i say have a lookup table, based directly on wind tunnel forces in every concievable configuration.
As for yaw, even ferrari can only go to 3 or 4 degrees, the wheels must be touching the rolling road (even a tiny tiny gap produces crazy results) which produces forces on the belt(which is already under massive load from both above (car underbody wants to lift it) and below (vacuum system to keep the belt down).

Also None of the vertical motions can be recorded even by the very top teams at sufficient frequency...the movements are just too slow in the tunnel.

But the improvements of the top teams are due to improving aerodynamic stability; benign aerodynamics are achieved by keeping all flow regimes stable as the car goes through its normal motions on the track; ferraris peak downforce may be no greater than any other teams. This improvement is mainly down to advancements in testing the car during these motions.

Balfa

Whoops. Now i've gotten way out of my depth. But the bits that i do understand are interesting