Sounds to me like a classic network replication issue.
The server should be handling the acceleration for the clients in order to allow exact measures for both clients.
seems like you have it set that way by what you wrote…
In reality, there is no exact fix for this.
On the client you are running one simulation.
On the server another.
The server drives the client, so in the event of a desync the server tells the client to reset to the position he has.
thus, lag, stutter, etc…
Usually, you go around this by having the client drive the server, and having the server drive additional clients.
this is still prone to lag. However.
A client driving who has a high ping is still somewhat accurate since he’s driving the changes you propagate to other players.
Perhaps less obviously, allowing a client to drive the server is an immediate cheat. You can hack your way into changing the location of the player, and the server just has to take it as gospel. Thus, you make it (somewhat) easy to cheat (Hi there Rockstar!)
The player experience is obviously better.
The default plugin’s Net Code could probably be updated for your specific use case, so that acceleration is handled faster/at higher ping rates, etc. But you basically need to be a videogame network engineer with 3 years of work on the subject to improve what is there.
you can hope that the new changes brought about by Chaos will provide you (eventually) with a better solver and a better network code. Since for the most part Fortnite doesn’t have glaring issues except for some specific server.
That said, perhaps someone more versed on both network and car racing can give you a better fix.
Also, maybe its possible to scale by the client ping in some way. Meaning: The server drives everything, but adjusts what is what for the clients based on the local ping.
make everyone automatically lag as much as the lowest connected ping.
NOT optimal, for sure, if not just a stupid idea…