I don't usualy use it (hence the fact that it's not on my computer with LFS)
I used it just to see what one of my ratio sets would do one day.

Big edit: according to GRC, shifting at 6 reduces acceleration even though the speed of the rear wheels is the same. not sure how that works.

In regards to what GRC says, The XRT doesn't benefit from shifting at 6k.
I was sure it did.

So I apologize for stepping on peoples toes. I'm used to other sims where you can squeeze the engine abit and get better resaults.
apparantly, LFS models the engines a bit more realisticly than I knew.

I still can't understand why my car was faster when I shifted at 6k before.

Even bigger edit!: I overlooked something, I'll have to run the calculations again. (my dad reminded me that it matters where your RPM ends up after shifting, thus I have to re-do my calculations)

Ok after alot of tinkering I'v found a shift point for the XRT. I balanced the gears so that the top speed is still the same but you shift at 6.5k and it stays within the power range of the engine.
My main problem sometimes is that I overlook some of the aspects of a problem.
The torque curve of the XRT falls off at 6.5k not 6k, thats what I had wrong, along with overlooking gear entry RPMs.

The best way I find of getting the best performance out of a car is by keeping it within its optimal power range as much as posible. I think I did a good job on my last calculations since going to 7 now doesn't make any difference in acceleration.

Quote from DragonCommando :

The torque curve of the XRT falls off at 6.5k not 6k, thats what I had wrong, along with overlooking gear entry RPMs.

But doesn't that depend on the boost, since the XRT is turbocharged?

You generally wanna shift the moment more power becomes available in the next gear--even a fraction of a second after that as speed will drop during the gear change (your reaction time to the shift light is usually more than enough).

The light happens to come on when more power is available in the next gear. Kinda cheating, eh? It has been suggested that we get a realistic (adjustable) one in replacement.

The thing is, the gear ratios actualy make up the difference between 6.5 and 7. the gears I tested actualy work at 6.5k.
The shift light is sort of adjustable, but it's done with the gears. So it still comes on when more power is available, but for my setup thats at 6.5.
The car actualy accelerates faster with the 6.5k setup than I'v ever seen it at any of my 7k settups. But then again, my 7k setups are all real ratios from race transmissions, I didn't use any self calculated ones for my proper setups.
I preffer that method over tinkering with the trans because I like to spend my time adjusting everything else and driving.

Edit: the shift light isn't adjustable at all, it comes on at 7k regardless of what you do, even if there is more power in the next gear before 7k.
GRC just shows that it should, but it doesn't.