Kendall, this does seem quite unbelieveable. Perhaps it is absolutely true but I want to see both these examples on the track for myself. (or ride along with Mark) I know the IRS is heavy and weight is a significant track factor as is handling which will be better with the IRS. But the Boss solid axle was pretttttty good. Tires make a big difference as well and the LS did come with R tires.
Making some distance assumptions from the quoted data, that would mean the new Mustang is a little over 5% faster than your LS around the whole track. Knowing what you know about the LS performance (as you have a lot of seat time) does that seem credible to you?
Well, I'm not sure to be the best qualified "driver" to make the comparison - although my goal is to get there some day! But that said, from an engineering perspective, it is relatively easy for me to believe. As others have said, I think that Ford had the executive nod and corresponding budget to develop the IRS for the Mustang. Having completed that, early testing of this "now good" rear suspension, the weaknesses of the front suspension became rather obvious. The engineers had to go back to request additional program money and approval to re-do the front suspension geometry. They got it and they did it.
What Ford accomplished with a live axle with the Boss 302/LS program was truly amazing. I don't think anyone could have predicted just how good of a job they pulled off with those "constraints". But, I can vividly remember multiple track sessions when I was chasing my friend in his M3 around the track. While I should have been looking and thinking about my driving, more than once I caught myself (the engineer) in total awe of what his rear IRS suspension was doing. Honestly, it was kind of mind warping. In a different context, I could have stared at it for hours instead of just seconds. It was literally just following/hugging the road. So as the road rose, fell and turned while the car dove, twisted and yawed about - the suspension kept total road-holding composure. Simply stated, in the "chaos" going on around it, the suspension was relentless in just keeping the entire contact patch of the tire glued to the road. It was really cool to watch. This was the ah-ha moment for me. In contrast, following my buddy in his Boss 302, there was two tires connected by a "stick" and in the chaotic environment of the pitching and yawing of the car with the simultaneous twisting and turning of the tarmac.... there was never the same "connection" between tires and asphalt. Hands down, IRS for a road-course car is just super-superior solution.
Engine performance between the Boss and the 2015 is really a wash. Hats off once again to Ford who managed to accomplish Boss-like HP/TQ numbers and curve shape in a mass-produced engine. And finally there is the braking - which once again is so clearly superior in the 2015 with massive 6-piston Brembos on much larger rotors. In short, massive suspension advantage. Comparable engine performance. Big braking advantage. = 14 car length advantage..... and likely even more with a curvier track.
