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Old 12-09-2014, 11:35 AM   #897
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Originally Posted by fatoni View Post
what is "better weight distribution"? the vette is already rear biased and thanks to a transaxle, most of the weight is in the middle of the car already.
For the record, C2 and small-block C3 Corvettes had more rearward weight distribution than the C7. Here's a test for a 1967 427 with 46F/54R weight distribution: http://media.caranddriver.com/files/...corvette-3.pdf Looking at the 3137 lb. curb and 3563 lb. test weights, I'm assuming that car had about 225 lb of test equipment in the back, but even accounting for that gives 49F/51R weight distribution for a car with a big iron-block 427!

Going to a transaxle with the C5 did not improve weight distribution. It stayed around 51F/49R, similar to the C4. The transaxle forced the rear wheels aft a bit, which hurts F/R distribution as much as or more than moving the mass of the transmission aft helps. It also forced a longer wheelbase, which hurts polar moment. Word is that they went to a transaxle for structural reasons, apparently related to the fact that they were forced by marketing to keep the fully removable roof available.
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Old 12-09-2014, 01:04 PM   #898
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Originally Posted by DantKR View Post
Which car are you talking about exactly? No one here really cars about the convertible. The C7 hardtop and C7 Z06 are what we're talking about. Neither of those run neck and neck with the STi.
Wow did you even read the original comment? Someone said the convertible automatic base C6 was a monster, not the z06, not the zr1. Read please before commenting.
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Old 12-09-2014, 01:05 PM   #899
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Originally Posted by jsimon7777 View Post
C6 is a monster too. Heck, a stock, non-Z06 C6 automatic convertible with base suspension is a monster.
There you go @DantKR
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Old 12-09-2014, 01:14 PM   #900
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Thanks for clearing that up. I missed the convertible part.
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Old 12-10-2014, 01:23 PM   #901
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Makes for some an entertaining read.

http://www.corvetteforum.com/forums/...vs-c7-z06.html
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Old 12-10-2014, 01:50 PM   #902
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Semi-related, for those that don't know the history of the small block in this Vette and its history, a good blog entry on that is here, related to the value (or lack thereof) associated with the school you went to.

The most pertinent portion...

Quote:
Originally Posted by Thomas Stanley, PHD Author of The Millionaire Next Door
...This discussion of success factors does have something to do with the highly touted 2015 Z06 Corvette featured on the cover of the January 2015 issue of Car and Driver. The Corvette is powered by a 376 cubic inch supercharged "small block V-8." This engine was originally designed [with 265 cu.in.] in the early 1950s by Ed Cole and his engineering staff at Chevrolet. It debuted in 1955 and was all new, high revving, durable, light weight, and compact. The crank shaft, according to Automotive News, was only 21.75 inches. Cole had the foresight to recognize that in the future engines would have to have even more power. His innovative design did in fact accommodate increasing the internal displacement of the motor and thus its horsepower. Over the years many modifications have been made to the "small block." Yet its basic design remains and it is still compact.

Ed Cole did not attend a top rated college, no not MIT, not Cal Tech either. According to Automotive News:
He attended Grand Rapids Junior College (later) enrolling at the General Motors Institute . . .
As a driver I have put more than a few miles on cars that were powered by "small block" Chevrolet V-8s. Where the designer attended college had zero to do with my choice of motor vehicle. And I'm certain that those who owned cars powered by the more than 100 million "small blocks" were of the same mind set..
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Old 12-10-2014, 01:57 PM   #903
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Makes for some an entertaining read.

http://www.corvetteforum.com/forums/...vs-c7-z06.html
C7 got spanked :O Those TA run about 127k. Wonder how much that C7 cost. I wonder if they changed drivers(I doubt because who the fuck would do that lol.) Wonder how they would do on the track.
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Old 12-10-2014, 02:15 PM   #904
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[ame="https://www.youtube.com/watch?v=DLa3l_UX77c"]https://www.youtube.com/watch?v=DLa3l_UX77c[/ame]

Lets see what's up next!
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Old 12-10-2014, 02:16 PM   #905
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Those TA run about 127k.
Nah, google Dodge Viper Markdown
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Old 12-10-2014, 02:19 PM   #906
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-15k right? Nice chunk off. I think that makes the Z06 with all the extra(forget what it's called) around the same price. Let's see what happens when they try it on LS and see if they can beat the TA's time.
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Old 12-10-2014, 02:49 PM   #907
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Originally Posted by serialk11r View Post
More rear bias. Also lower polar moment, which is hard to achieve with the engine at one end and the transaxle at the other.
I really wonder about the whole MR vs. FMR issue. Which is faster on the track. My biased no-data opinion is that if both are restricted to the same weight, FMR is better. I think the benefit of MR is not the rear bias, but the less overall weight.

I vaguely recall interviews about it back when it was JGTC and allowed both FMR and MR. IIRC being MR had a weight penalty associated with it, so all the top cars were FMR, but i'm not sure how much the weight penalty it was. Was it so they were heavier than the FMR cars because they didn't like honda? or just to make the weights equal?

If you look at the current "affordable" super-car beaters, the dodge viper, corvette z06, and the gtr, all are front midship. The z06 and gtr are both front midship with a transaxle, with the gtr being 4wd.

All the current Million+ super cars however are all mid engine 4wd hybrids, and clearly at the extreme end like F1, the weight benefit of MR is unbeatable.

I wish real professional engineers shared their mathematical models and would answer these types of questions.
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Old 12-10-2014, 02:54 PM   #908
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Gods do I hate Jonny Lieberman. That guy writes like me at 16 at acts like Lincoln at Disneyland.
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Old 12-10-2014, 03:13 PM   #909
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Quote:
Originally Posted by totopo View Post
I vaguely recall interviews about it back when it was JGTC and allowed both FMR and MR. IIRC being MR had a weight penalty associated with it, so all the top cars were FMR, but i'm not sure how much the weight penalty it was. Was it so they were heavier than the FMR cars because they didn't like honda? or just to make the weights equal?

I wish real professional engineers shared their mathematical models and would answer these types of questions.
? There is not much to model. MR moves the center of gravity back for more grip at the rear and decreases the polar moment so the tires have to do less work. I'm pretty sure a race prepped MR2 will outperform a race prepped Miata. Like the F1 cars you mentioned, race cars will often have a huge rear bias.

I'm pretty sure FMR is not inherently heavier than MR, at least with the torque tube setups you find on the higher performance cars. The torque tube only barely adds any mass. Having the engine at the front makes cooling a bit simpler.

The reason why FMR is popular is because the low polar moment of a MR car can bite you in the ass in the form of snap oversteer. A rear engined car like the 911 will also rotate easily because the light front end can change direction much faster than the rear. MR2s and 911s alike are known for losing control easily when pushed past the limit.
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Old 12-10-2014, 03:26 PM   #910
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? There is not much to model. MR moves the center of gravity back for more grip at the rear and decreases the polar moment so the tires have to do less work. I'm pretty sure a race prepped MR2 will outperform a race prepped Miata. Like the F1 cars you mentioned, race cars will often have a huge rear bias.

I'm pretty sure FMR is not inherently heavier than MR, at least with the torque tube setups you find on the higher performance cars. The torque tube only barely adds any mass. Having the engine at the front makes cooling a bit simpler.

The reason why FMR is popular is because the low polar moment of a MR car can bite you in the ass in the form of snap oversteer. A rear engined car like the 911 will also rotate easily because the light front end can change direction much faster than the rear. MR2s and 911s alike are known for losing control easily when pushed past the limit.
what if you made the mr2 and miata have the same weight and same engine and same tires?

why would an MR car have a lower polar moment? a 50/50 transaxle has much lower polar moment compared to the CG. But that's some imaginary CG, not how the car actually turns in most instances. If a car is over-rotating, like at corner entry, it is actually probably rotating more over its front wheels. So an MR car will have MUCH higher polar moment, and that is exactly why they have a tendancy of snap oversteer in corner entry.

i recall hearing an interview with a JGTC engineer saying that actually slight front bias is better for a race car, mostly because on track, when you let go of the brakes, you get on the gas almost immediately. He said basically you want close to 50/50 balance for the driver when you are mid corner, and to do this you actually need slight front weight bias since the driver is on the gas mid corner.

It kind of makes intuitive sense to me too, because to be fast you want to be at the traction circle on all your tires. in a RWD car, if you have extra traction on your front at corner exit, it does nothing for you.

FMR definitely has more weight by packaging.
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