Question for a friendly set up and gearing expert...

I am (very slowly) teaching myself about set ups.

Using the Formula Trainer (not the advanced version) I've been racing at Adelaide 1988. I am using the default gear ratios with one change - a shorter final drive by two clicks.



Assuming a 22 inch diameter wheel/tyre, I have calculated that I would expect a top speed of roughly 180 KMH at 7000 RPM in 3rd. You can see in the first two screen shots below this is more or less what I'm getting:




But I also get this:


Same gear (3), same track speed (176), same set up but a much lower RPM (5400ish). At that RPM my calculations suggest it should be roughly 140 KMH. I don't understand this reading. I've obviously not understood something. Shouldn't the road speed and RPM in a given gear be consistent?

I'm NOT suggesting there's a bug or anything wrong with the sim. I'm just trying to learn and this has me stumped.

I realise this a bit technical but does anyone have any thoughts about what might be happening here?

 

My unqualified guess is that this is again an example of the sloppy coding bought over from Ian Bells pCars2.
And Im not surprised of your finding

 

It could be related to that gear ratio issue which I remember was talked about before

 

Thinking about it overnight I wonder if it has anything to do with being relatively late in the braking zone at the end of the longest straight. I would have been decelerating rapidly at the time.

I would still expect rpm in a particular gear to be the same speed though…

…unless I had lost traction and this is ‘GPS’ speed. In other words the rear wheels are rotating at a speed consistent with rpm of 5400ish in 3rd gear but as I have some subtle slide happening the car is still moving through space at 176 kmh.

I don’t remember any significant sliding but I was having some front lock ups as the default brake bias is too far forward (for me) and I hadn’t changed it.

I wonder if that might be an explanation?

Unfortunately I only have screenshots taken in the race. Didn’t save the replay…

 

Thanks for joining the discussion @CrimsonEminence, I hope I am not wasting your time.

Tyres would have been a little bit more worn in shots 2 and 3 (as listed below), especially the right front which I was locking up a bit:

* Screenshot with Gear 3 / 5400 RPM / 176 kmh taken at end of Brabham Straight on lap 1.
* Screenshot with Gear 3 / 7000 RPM / 175 kmh taken start of Brabham Straight on lap 6ish.
* Screenshot with Gear 3 / 7000 RPM / 177 kmh taken 1/4ish way down Brabham Straight on lap 3.

First screenshot (as listed) was first start of the race. Next two were taken in an immediate re-start of the first race with same set up.

The main difference is in the first screenshot I would have been shifting down the gears and braking at this point. The reading may be a momentary fluke during the transition maybe?

I have considered the possibility that the gearing set up was somehow different in the re-start but even if it was (I'm 99.999% sure it wasn't) the default set up (if it reverted to that) gives very roughly around 155 kmh in 3rd at 5400 RPM so that would also be unexpected. Also, I was also only mucking around with gear shortening and it would take some lengthening to get 176 kmh at 5400 rpm in 3rd.

I want to stress, as I did in the first post, I am NO expert on this and in fact I'm just trying to learn about this stuff for the first time. I am not suggesting a problem with the sim but I am intrigued by this reading because it suggests I'm missing something important.

Thanks for reading.

 

It’s possible and seems to me (as a non expert!) the most likely explanation.