Escort GT/LXE to ITB?

Flyinglizard said:
Funny. I was asked about 12yrs ago about the very cars we have been talking about.
" Mike Do you think that the Rocc and Rabbit GTI are good with 50#?"
"yes. they are about right with 50#".
Click to expand...

I would like to see that on the real world, there is a measurable difference between these two cars. I couldn't get MkI numbers, but for MkII cars-

88 Golf GTI- .35 CD and 1.91m^2 frontal = .6685 m^2 drag area

88 Rocco- .38 CD and 1.74m^2 frontal = .6612 m^2 drag area

When looking at the two cars, *I believe you* when you say the Golf should be lighter because of an aero issue. HOWEVER, the numbers don't seem to bear that out. According to those numbers above, the aero is about 1% worse on the Golf, equating to about 25 lb. of weight reduction, not 50. And then what about all the other areas on track when lighter weight is another advantage? Is throwing 50 or 100 lb at the "slipperier" car to slow them on the straightaway going to also affect them other places? Yes. And at the slow, technical tracks, it's a double whammy because you'll never have the straightaway to gain and make up for the loss you suffer through every corner...

I think there are some other significant unaccounted factors that should be addressed long before aero. Even on those factors, I'm not sure the cost/benefit ratio is going to make it worth the risk...
 
"Weight" is mass, which factors into the mass-momentum math of performance, in terms of acceleration in ANY direction - fore, aft, left, and right.

Aero drag can be measured in pounds or horsepower (negative, of course).

The two have NOTHING to do with one another - that is, decreasing weight does NOT make a car more slippery...

What we're doing here is trying to make up for an apple shortage in our pie factory by shopping for oranges.

There's LITERALLY no way to do the math to convert Cd and frontal area in to some equivalent volume of lead bolted to the floor of a car. The only way to make that conversion - and Mr Ogren is doing it - is by bootstrapping some weight onto the higher drag car, based on experience from observed on-track performance. I'm not saying that his experience is somehow flawed but the INSTANT we have a process that requires the application of that kind of pseudo-scientific "evidence," the category is DOOMED to the competition adjustment (bleah!) trap that people complain about in Prod and elsewhere.

K
 
ShelbyRacer said:
According to those numbers above, the aero is about 1% worse on the Golf, equating to about 25 lb. of weight reduction, not 50.
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First off, great post by Kirk above.

Second, the math above is simple in a vacuum but who could ever say that a 1% difference in 'areo' should be 100% linear to a 1% difference in weight? Should cars with 10% more HP weight 10% more? Should cars with a 5% more brake rotor size weigh 5% more?

It's an impossible task.
 
Please don't think I was in any way trying to make a statement about what I thought was right or wrong. Andy and Kirk you actually made my point. By trying to "simplify", we could make things exponentially worse.
 
I could simply take the base car, and come up with cars that are 1)the same, +-10%
2)Way better, -11% or more
3) way worse, +11% or more.

It not rocket science. Just a relative value resulting in a usable adder based upon # per hp that you come up with, times aero value.

Not a big deal , just crude numbers that would move 50# here and there.
Too many engineers trying to live in a perfect world that doesnt exist.
let me know. I have plenty to do.
MM
 
Knestis said:
"Weight" is mass, which factors into the mass-momentum math of performance, in terms of acceleration in ANY direction - fore, aft, left, and right.

Aero drag can be measured in pounds or horsepower (negative, of course).

The two have NOTHING to do with one another - that is, decreasing weight does NOT make a car more slippery...

What we're doing here is trying to make up for an apple shortage in our pie factory by shopping for oranges.

There's LITERALLY no way to do the math to convert Cd and frontal area in to some equivalent volume of lead bolted to the floor of a car.
Click to expand...

There is literally no way to rely on a precise formulaic, here are your inputs and you don't need to do any thinking to generate that result. Drag is increasing with velocity in a non-linear fashion.

...the application of that kind of pseudo-scientific "evidence,"...
Click to expand...

We already rely on a pseudo-scientific process.

Please be kind enough to provide the exact formulas and data used to check the accuracy of those same formulas that are the basis for the already adopted adders used in the scientific method to process the cars. If I recall correctly, weren't these determined via software whose internal workings could be correct or determined by newts?

Please be kind enough to provide the scientific calculations that demonstrate that equating HP:weight ratios alone generates similar performance. As observable data are viewed as taboo, the actual outcomes of IT races are not permitted to be submitted as validation.

Don't sell the process as the equivalent of plotting a ballistic trajectory.
 
You make the mistake of assuming that I am going to try to defend the Process with claims of accuracy or certitude. I wouldn't ever do that because its value is that it doesn't TRY to be "valid" - in the sense that it spits out perfectly "right" answers. It's more important - and I've been arguing this online for a dozen or so years now - that it be "reliable." Repeatable, transparent, and diddle-proof. I'd propose that pretty much everything we've done to try to make it "better" has ultimately been a small step in the wrong direction.

K
 
So?


Knestis said:
EDIT - Readers' Quiz Time!

How much difference do you think this air dam made at Road Atlanta, in back-to-back testing with the stock configuration? It included a to-the-max undertray:

ARRC10.JPG


Here's stock...

vir0902.jpg


K
Click to expand...
 
Flyinglizard said:
I could simply take the base car, and come up with cars that are 1)the same, +-10%
2)Way better, -11% or more
3) way worse, +11% or more.

It not rocket science. Just a relative value resulting in a usable adder based upon # per hp that you come up with, times aero value.

Not a big deal , just crude numbers that would move 50# here and there.
Too many engineers trying to live in a perfect world that doesnt exist.
let me know. I have plenty to do.
MM
Click to expand...


Mike, first off (with no disrespect), you need to get a girl friend.......... and if you're married.......... you need to get a girl friend................... :)


90% of the drivers in IT are not good enough or consistant enough to make a difference with 50 lbs more or less. We're not pros. I consider myself a so/so driver and i can't tell the difference in handling when I have a full tank of gas and an empy tank of gas. Again, if 90% of the guys say they can tell the difference........... I call bull shit.......

And to figure aero on 300 cars?? Our energies as a class are better spent else where............

And we won't EVEN start discussing how most of the cars out there are NOT even 10/10ths builds.......... seriously???? 50 lbs??? Let it gooooooooooo.
 
LMAO!!!

90%? You're being way too nice.

One area that I think still should play into the equasion more is torque. I recognize this has been discussed several times already though.

Kirk, I know the point you're getting at but do think there are benefits to be had with a well constructed air dam / undertray design. Some cars have features that would make it more beneficial than others. Take for instance my Prelude. It would be very interesting as we (Gulick and I) looked at it and thought there's some really good potential.
 
...point being, you are "looking" and "thinking" and aero doesn't play that way. We were "sure" that the Talledega-spec air dam would make Pablo faster at RA. It made (drum roll please) exactly NO measurable difference in DL1 data in back-to-back sessions on the same day.

We already have way to many opportunities for people to be "sure" of things about IT cars, just by looking. "That car can make more horsepower." "That head will never flow as good as this one." "That suspension is a fustercluck and won't ever work." "Miatas are magic."

Adding opportunities for subjective determinations of aero drag is a fool's errand. And make no mistake that reverse-engineering decisions from on-track performance is precisely that - subjective.

K
 
Jeff, thanks. You are very funny. A guy races a Miata and would give away 50#? BS.
50# in my Miata is 1+sec on Sebring.
The Rocco is the same weight as the A 1 Rabbit, not the Golf-2. The G 2 has 12 more HP,not the same car at all.
FWIW the A1 cars are both heavy around 60#, the G2 is pretty close, the MK 3 is 50-60light.
#/CC

Kirk, what did my est say? maybe spot on. There is a reason that I did not ask for air dam info, just the total sq in and hood line height, glass angle.

The front dam that works, needs to be snow plow shaped and at least 6 in front of the bumper area. Email me for pics if you want . Not legal for any SCCA stuff.

Try this tho;
Take the same golf. Raise the rear 2in . run the car watching terminal V.
Lower the car until the axle hits the body. Run
the same pass. You will have a hard 2-3mph gain.(info from my book)

Some stuff matters, some doent. I am pretty good at the stuff that does.
I will go back to fixing my Chumpcars/HPcars
Ignoring aero is still a mistake.
 
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Thats funny. Yeah 50# is over 1 sec, either the Miata or the HP car.
I can loan you a baseline driver if you want. It's kinda what we do. help guys/car combinations, go faster.
As soon as you think that you cant possibly go faster, well for sure you cant.
 
JeffYoung said:
No, 50 lbs is not one second. At least not on a repeatable basis attributable to the weight alone.
Click to expand...

X2. Spec Miata dicked around with weights plenty over the years, and NEVER did 50 lbs equate to one second with ANY of the cars I ran against. (And I'm pretty sure the Saferacer guys didn't leave any stone unturned the years they were giving a full effort.....)
 
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