For outright quickness you can go with power to weight ratio, and it's universal to test for 0-60(/62) and 60 - 0 and slalom or lateral grip, but can you put these things together and have a formula about what car is going to be faster around a track and do a reasonable ranking with that?
How fast it will be or how trackable? Trackable has a lot to do with brakes and cooling and durability. Hard to set a fast time if you're in the tire wall with flaming brakes.
Figured it was the SPH more than anything
You can go look at times different cars get on different tracks, I suppose? I mean, you can probably use Google to find out what any sporty car has ever run on VIR or the Glen or whatever.....
mazdeuce - Seth said:How fast it will be or how trackable? Trackable has a lot to do with brakes and cooling and durability. Hard to set a fast time if you're in the tire wall with flaming brakes.
This. Trackable means it can take the punishment of being tracked, to me. Start with something light and you can always upgrade things like brakes and cooling, IMO.
In reply to P3PPY :
Rule 1 about a track car: do you like it.
rule 2: make it fast.
I suspect the answer to the question is "NO".
Too many variables and even more unknowns.
If I had to pick two of those variables that I could control, I would chose a stiff chassis and light weight as a good foundation for a track car.
Pete
Weight!
Less weight = better track car *
*some exceptions may apply
Can you afford to walk away from the wadded-up remains?
mazdeuce - Seth said:How fast it will be or how trackable? Trackable has a lot to do with brakes and cooling and durability. Hard to set a fast time if you're in the tire wall with flaming brakes.
"How fast" was what I was really getting at. Also nice screenname
What is SPH?
You probably could put them together and make a decent estimate, but it would be a lot of work and not very useful. You'd also need to use differently weighted formulas to get estimates for different tracks, since you need very different cars to be fast around Road America vs. Ebisu's touge course.
I seem to recall Andy Hollis saying he has some kind of spreadsheet just like this for autocross... Had to do with things like suspension type, fwd/rwd/awd, track width, power to weight, weight to tire ratio, etc.
I think personal tolerance is the deciding factor, along with how deep you pockets are.
With little disposable income and quite tolerant I could have fun in any car, but for a long term ride it would need to have a good base.
My M3 made it onto a track a handful of times and handled it very well and handled well. I could not afford to make it faster and it was worth too much to wreck or beat on too much.
Currently I'm running a fox chassis Mustang, it has seen hundreds of laps, its handling is tolerable at best. It was cheap to buy, even cheaper to build, and now is faster than the M3 at least by lap times. If it gets wrecked I can sell off all of the parts or just find another fox chassis to move them to. A 350 hp extra motor is costing me about $3500 with Aluminum heads and a stout bottom end. The stock motor with bolt on goodies is still running strong with over 100k miles on it. With the M3 it was about $2500 for 20 horse added to the same motor and forget about a rebuild or upgrade.
Seriously, I would look for weight distribution and suspension design as a key factor in a track car. A 525 or 535i would be a good start, or older Honda even though I don't appreciate FWD. Power and brakes can come later, a robust power train will keep you on the track and having fun.
PS - it turns out that pretty much any vehicle is trackable:
Tracking a car is all about cooling. Sure, you might be able to set a flaming fast lap (and I say that literally) but you'll be in the pits with cooked brakes and... Well, there are a number of maintenance mods worth doing for consistent track time. I'd argue you only get those fast laps in a car with consistent performance, which makes cooling mods well worth the money
Look at an HPDE event on motorsportreg and see what everyone is tracking. The more entries a given type of car has, generally the more trackable it is. I.e. Miatas, E36M3s, and Corvettes.
Track days are about making the driver fast, not the car. Speed is relative.
Just uh, add up the front and rear track of the car. That'll get you the total track value, which will tell you how well the car will do while cornering on a track. Cause as that weird Hawaiian dude in those old Pontiac ads used to say: "Wider is better."
In all seriousness, I tend to agree with Matt. If you so desire you can make anything trackable. Cars that cook their brakes, have weird suspension behaviors, frail engines, and have costly consumables take more work, but in a relatively rules-free track day or time trial environment you have a lot of tools at your disposal to correct whatever issues you might encounter. I've seen a guy complete 2 hours of trouble-free track time in a Ferrari Testarossa. If he can do that, you can do anything.
Personally I like to look at production-based touring car classes to get a gauge of how much work it would take to make some of these cars work. For example, the previous gen Honda Accords ran in surprisingly close to stock trim in PWC (for a World Challenge TC Car), with the only rules-excepting components being a few adjustable control arms for the rear suspension. On the other hand the 2010 Nissan GTRs running in PWC GT needed tons of cooling and transmission modifications as well as comically fender-jutting tyres to last the length of a race.
Needless to say I'm currently looking for an affordable Accord V6 to use as a cushy and unique track car while avoiding old GTRs like the plague.
I'd also throw in there that you need to have fun in it. If you hate driving FWD cars, then the fastest one isn't going to make you like it more. In fact it may be the opposite - I remember when I was in high school trying to autocross my camry (V6 yo!!!)... It was more fun than I can have on the street, but man that thing sucked. I vowed to never buy another FWD for fun and that was that...
It seems to me the question could only be answered with testing. Like a Top Gear format with a designated driver on the same course for each car times 50 or 100 laps but I dont think that's what the OP was asking. Seems like a formula could have variables plugged in like a points system:
power to weight=9 (4#perBHP)
Braking=7 (60 to 0 in x ft 25 times in a row avg)
Coefficient of drag= 6
Skidpad=7.5
Total for car A = 29.5 ranking is 17th
Or something like that?
I think lap times are a good indicator of how trackable a car is.
(tee hee)
The problem is the question relates to a complex multi variate equation and you seek a single answer when in fact there is many answers. But what do I know? I am just some stupid courier riding in your elevator.
I think the closest publicly available comparative approximation would probably be the formula used for calculating the NASA Super Touring "adjusted" lb/hp ratio used to level the performance playing field across wildly different types and builds of cars.
now just so we're clear, I'm not actually looking in terms of what I can personally buy or race, I'm just kind of a statistician hobbyist nut too.
In reply to P3PPY :
Got it.
I guess reading up on vehicle simulation might be a good way to approach what's been quantified, and how it affects things.
Being wide reduces the amount of weight transfer to the outside wheels, so gets more work out of the insides, but increases frontal area, reducing acceleration and top speed. Lowering CoG height helps with the same thing, without the downward side effect. But a big engine may pay off in acceleration and speed despite raising the CoG AND the frontal area.
Basically, you want to know the formula for a race car, more or less without a specific rulebook. It's a popular question that's been asked since the dawn of the motorcar, with a complicated set of answers.
P3PPY said:..."How fast" was what I was really getting at. ..
While there are certainly a bunch of other factors lateral grip and power to weight will give you a pretty good idea of how fast a car would be around a road course.
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