What determines the mid engine adder?

[quadzjr]

On anecdote, I'd initially *think* that if anything, balance would tend to go more in whichever direction it starts. When we cleaned out the Golf shell, it ended up being a big box of air in the back. We couldn't take much at all out from the dash forward.

K

That is pretty much I think happens to most vehicles. Having a longer wheelbase would lessen this effect a bit.

[ekim952522000]

OK so I know some of you guys don't like LapSim but I decided to run some simulations with a 2500lb RWD car.

Here are the results.

Watching the simulation it looked like the rear weight biased cars had slightly slower mid corner speeds but later breaking and were able to get back on the gas sooner.

[Knestis]

OK so I know some of you guys don't like LapSim but I decided to run some simulations with a 2500lb RWD car.

Here are the results.

Watching the simulation it looked like the rear weight biased cars had slightly slower mid corner speeds but later breaking and were able to get back on the gas sooner.

Veddy interrrresssting.

Thanks!

K

[Andy Bettencourt]

I asked Mike to run these to see what the results were for a mid-rear bias vs. a 50-50. Seems the SIM sees value in the layout.

[quadzjr]

Watching the simulation it looked like the rear weight biased cars had slightly slower mid corner speeds but later breaking and were able to get back on the gas sooner.

Which pretty much details exactly what I have seen on track. I was able to pull up to a friends miata, mid corner I was busying tryto to catch the car he would pull me, and at corner exit I was on the throttle trying to reduce the damage. All teh advantage seemd to go out the window mid corner. Having LAPSIM with a perfect driver is one thing.. driving that car on thr ragged edge in real life is a whole other ball game.

[Chip42]

Having LAPSIM with a perfect driver is one thing.. driving that car on thr ragged edge in real life is a whole other ball game.

in all fairness, that's not the ITAC's problem.

LAPSIM is not what we base our rules on, as has been repeated countless times. it is a nice sanity check, though. as we are discussing a subjective handicap, it's as good a place to start as any.

th big standout, to me, is that the "preferred format" of the mid-rear engine,(using the 150hp example) @40/60 F/R distribution, is roughly 1s faster than the VERY common 50/50 cars, while the FWD 60/40 (or more front) car is an additional 2s slower (getting worse as % shifts forward).

again, noting that LAPSIM is simply a sanity check, it appears that we are penalizing the MR cars an equal amount as we are "helping" the FWD guys, for half the benefit. and the case is stronger in the 200hp column.

the handicap as a percentage of overall "process" weight, as discussed recently with regards to FWD and high torque is the way to go. additionally, it would appear that the MR adder should be ~half of the FWD weight break, assuming a 50/50 car as the baseline. as no one can predict with better than ±5% accuracy what the as-raced weight split will be in a given car, it's not worth the effort of trying to do so in the classification process. Noting a significant forward weight bias (FWD) or rearward weight bias (ME RWD, RE RWD) as is done now seems sensible and simple enough to use, with a determinate classified weight% adder or different IT power gain multiplier for these cars. the current process is good, but could be tweaked to be better. let's not throw the baby out with the bathwater.

[ekim952522000]

Keep in mind all the cars in this simulation were RWD.

[Chip42]

Keep in mind all the cars in this simulation were RWD.

probably for a new topic, but would you care to run 120/150/200 hp cars with the weight split 60/40 through 35/65 RWD and 70/30 through 60/40 FWD? Obviously a front-heavy RWD car would have a few traction issues thus influencing the results.

nothing but a sanity check.

[ekim952522000]

probably for a new topic, but would you care to run 120/150/200 hp cars with the weight split 60/40 through 35/65 RWD and 70/30 through 60/40 FWD? Obviously a front-heavy RWD car would have a few traction issues thus influencing the results.

nothing but a sanity check.

I did run some FWD weight balance numbers in this thread
https://improvedtouring.com...t=25407&page=9

Post #174 It is not the same car or track but should answer your questions.

[Chip42]

thanks mike - I knew I'd seen that before.

as a matter of lap time % difference from "ideal" 50/50, given what mike has posted now and in the past (with all of the caveats that go with it):

layout, weight\hp 150hp 200hp
FR 50/50 0% 0%
MR 40/60 -0.082% -1.35%
FWD 65/35 +1.13% +1.40%

so it appears the effect IS roughly simillar, though mid-rear engined is simulated as slightly less beneficial than FWD is detrimental. I think we tweaking of the parameters, this could be minimized on either front.

the ITR rule might need to be rethought, but the 50 lbs is likely adequate and fair given the above.

[tderonne]

Neat results with LapSim. I haven't used it. Does it assume some nominal wheel rate or something such that the "setup" changes the weight distribution? What does it use for grip/tires? More weight is going to need more tire, but we're limited by rim width. A 50:50 car has an advantage there.

And no has mentioned the Fiero. Which is an ITA car now. I think weight was added in it's transition from ITS. Are these 50 pounds in there? Or did the ITA classification come before the new process?