Camaro XV

[David Pozzi]

Braking would improve too.

[MAP]

Indeed!

Some other quick thoughts:

1. Total vehicle mass might be reduced by about 5%, other things being equal (which they rarely are...!) Cost in production might come down similarly due to this packaging efficiency and reduced redundancy of parts - rather like FWD, in reverse. The rear engine/tranny/suspension cradle might even go down the same production lines as existing FWD platforms. The '80's Fiero comes to mind inside the GM camp...

2. Izz would probably come down even more -maybe 20% or so. This, plus shifting the yaw center farther back, should result in a much snappier steering response (but I'm guessing this isn't critical for the kind of driving Mark might be most interested in?)

3. The desire for rear traction, and the desire for steering neutrality, could finally converge under the hotrodder's favorite theme of narrow tires up front, and wide in the rear. RWD with a front-heavy bias tends to demand conflicting, opposing width parities.

4. From above, it would be easier to package really wide tires when they don't have to turn the vehicle as opposed to when they do.

5. Crash worthiness may be a big issue, however...

Anyway, I'm probably missing a bunch, but that's what I get off the top of my head (?)

Best,
MAP

[Chad-1stGen]

Originally Posted by MAP

Indeed!

Some other quick thoughts:

Cost in production might come down similarly due to this packaging efficiency and reduced redundancy of parts -

Best,
MAP

Ok you lost me there... Are you talking about building a custom car or manufacturing a line of cars lol

[MAP]

Apologies admittedly for a curve ball on that last post.

It's just a thoroughly ingrained habit with me to think about how to make the next 100,000 just much as making the next 1. It's my job in a very different field, actually. Please feel free to dismiss it as idle daydreaming!

Best,
MAP

[MAP]

Hi Folks,

I'm starting to suspect my post had the effect of halting further thread progress, and this absolutely wasn't my intention. I'll just add this point to my penultimate post and then invite everyone to carry on: as to steering neutrality, if an engine/tranny/suspension rear assembly can be made on a FWD line and per FWD methods, then with admittedly added cost, the steering function could be conserved. If so, then yaw dampening could be made constant irrespective of speed within reasonable limits, and it could be programmed to provide a direct dampening effect as well. The result would be highly predictable and stable handling with a tendency toward oversteer at low speeds, and understeer at high speeds. Maybe +/- 5 deg of rear-steer is all that's needed.

Again, please ignore and my apologies if this is unwanted input; I don't want to detract in the slightest from Mark's amazing work described in this thread.

Best,
MAP

[bdahlg68]

Originally Posted by MAP

Hi Folks,

I'm starting to suspect my post had the effect of halting further thread progress, and this absolutely wasn't my intention. I'll just add this point to my penultimate post and then invite everyone to carry on: as to steering neutrality, if an engine/tranny/suspension rear assembly can be made on a FWD line and per FWD methods, then with admittedly added cost, the steering function could be conserved. If so, then yaw dampening could be made constant irrespective of speed within reasonable limits, and it could be programmed to provide a direct dampening effect as well. The result would be highly predictable and stable handling with a tendency toward oversteer at low speeds, and understeer at high speeds. Maybe +/- 5 deg of rear-steer is all that's needed.

Again, please ignore and my apologies if this is unwanted input; I don't want to detract in the slightest from Mark's amazing work described in this thread.

Best,
MAP

Porsche is doing this already. Porsche credits the active rear steering in the 991 GT3 with ~ 15s improvement in 'Ring time. The development of the system though is quite pricey....

[MAP]

IMO GM is very good at finding simple, clever, low-cost solutions to complex problems. Best - MAP

[Ummgawa]

Originally Posted by bdahlg68

Porsche is doing this already. Porsche credits the active rear steering in the 991 GT3 with ~ 15s improvement in 'Ring time. The development of the system though is quite pricey....

At 130+ large, it ought to do more than that. You should be able to toss your W-2s in that sucker and come back the next morning and find a refund check, even if you didn't have one coming.

[GregWeld]

Originally Posted by MAP

Hi Mark,

I came across this thread yesterday and haven't had the time to digest it all just yet (!) but some simple math tells me that a rear-engine design with something like a 40/60% F/R weight distribution might do wonders for forward acceleration. I know this is a huge transformation, but at the rate you're going, I might imagine you're not many iterations away from something even this bold. Assuming mu(s) is 1.4 from the braking data, then your attainment of 0.85(ish) g's long. accel. is right at the theoretical limit given your weight distribution and ignoring transient effects from anti-squat (I'm assuming WB is 108" and the COM height is 21".) Go 40/60%, and you could attain 1.15g's.

Best,
MAP

If you want 63% rear weight bias he could just buy my Lotus 2 11..... Just be real mindful that the weight wants to lead the car... i.e., don't do a big throttle lift IN a corner... LOL

Everything has a trade off.

[MAP]

Generally speaking, when the center of thrust is forward of the center of mass, we have dynamic stability under forward acceleration. Under braking, the reverse is true. The former correlates more closely to a rear-heavy design, and the latter front-heavy. If accelerating while cornering, it does get more complex as you say.

Thx,
MAP

PS: I do hope we hear from Mark again soon. Please feel free to ignore all my posts about a rear-engine design if I crossed into a corporate no-talk zone.