Car is stable at 175 with the proper rake in it. I level my GS which ran 162, without the proper rake it was scary to say the least.

 

They move a bit but it's no biggie, till you lose your hat

 

That's good to know Yeah, when I took her up to 160 I was so focused on the road I didn't notice if the windows were shaking or not. I had the radio on medium volume too. If there is a next time I will run with the radio off and check the windows to see if there's any movement. It may be awhile though as I only go to Montana to see my brother once every two years or so.
Believe it or not, I really enjoy the long drive in my comfortable Corvette.

 

Does anybody know what the projected top speed will be for the upcoming ZR1? That baby should have no problem hitting the 200+ mark I would think. Unless they put a governer on it, which I highly doubt.

 

I know of a C6 and a C5 that hit 183each, same road, same day, same event,(its on u-tube) both said the cars were stable.

 

The C6 Z06 has a top speed of right at 200MPH with 550 HP, so you would only be a few MPH above that. As already noted, wind resistance can eat up HP in a hurry. A lot more HP to go a few MPH faster.

 

At 200 MPH it takes 6 ~ 7 more RWHP to go 1 MPH faster.

 

ZeeOSix,
It is closer to 100rwhp to get another 10mph or 10rwhp per mph.
Jeffy'

 

It really depends on what speed you're at. I specifically said "at 200 MPH". Here's how it plays out at different speeds.

@150 MPH, it's 4 RWHP/MPH
@200 MPH, it's 6 RWHP/MPH
@250 MPH, it's 10 RWHP/MPH
@300 MPH, it's 13 RWHP/MPH
@350 MPH, it's 18 RWHP/MPH

In 10 MPH increments:
To go from 100 to 110 MPH takes 20 more RWHP
To go from 200 to 210 MPH takes 65 more RWHP
To go from 300 to 310 MPH takes 137 more RWHP
To go from 400 to 410 MPH takes 240 more RWHP

RWHP is a function of velocity cubed ... so the required HP/MPH constantly changes and gets greater as the speed increases. You can see it's not linear by any means.

 

Once again you are talking paper and mathmatics. I am talking real life and I also mean at 200mph. Although yes the HP must go up at a cubed rate to keep incressing velocity. It is just your numbers are off. But you still continue to spout numbers like you have personal experience. This is the last time I will debate this with you. When you can say "I have been there and done that" come back and post your findings. Until then don't disagree with those that have. Just so there is no question that I have gone 200mph, see the link below first row third from the bottom. Also notice the number of times the Rick Doria is on there, he is Zsnnf in this thread that also attempted to set you straight.

http://www.openroadracing.com/html/200mph.html

Since the plaque only shows 203mph as the top speed here is the pic of my GPS that shows the 206mph in the upper right corner.


Jeff Dugan

 

Well, for starters I don't have to whip out my "credentials" to voice my opinions … I might have much more knowlege and experience than you think. Fact is, the physical and the mathematical aspect of this discussion can't be totally discounted because of your personal experiences.

In order for someone to accurately measure exactly how much more RWHP is required while doing a real world top speed run leads to more unknown variables and real world measurement challenges that can skew what's really going on. Sorry, but this top speed physics model accounts for every major factor involved. Obviously there is going to be a slight “disconnect” with someone's real world perceptions that may contain all kinds of unknown factors that can lead to erroneous understandings of the physics involved. If it takes 100 more RWHP to go from 200 to 210 MPH, then there are other factors going on that are not understood -- like gearing, aerodynamics, traction, elevation, air temp, air density, RH%, produced motor HP based on air conditions, etc, etc. You have to understand that the numbers I quote are based on a "perfect world" of the physics involved and the gearing of the vehicle ... no need to get twisted up over it.

So let's make this interesting. Please state exactly how you have determined that you can make the statement that it takes 100 more RWHP to go from 200 to 210 MPH. Give me more proof than your "I'm an expert because I've tired it" statement.

Be specific on the exact aerodynamics of your car, as well as the measured dyno RWHP curve, along with the exact gearing, the road surface you were on, and the elevation and air conditions you were running in. Also be specific on exactly how you accurately measured the actual produced RWHP during each of the 200 and at 210 MPH top end runs.

Yes, I noticed he never came back to answer my response ... seems as that branch was stronger than he thought.

http://forums.corvetteforum.com/show...8&postcount=59

 

Those of you who have stated that sixth gear in the Tremec T5600 trans will not survive the horsepower to propel a C5 beyond the 171 mph that a stock C5 Z06 does in fifth gear, I have data that says you are incorrect.

About three years ago I had Liberty Tranmission build me a custom 5th and 6th gear. 5th gear remained at the MN6 ratio of 0.74:1 and 6th gear was cut for a ratio of 0.563:1. After the gears were cut they were Micronited for durability and strength. I also installed a 4.10:1 final drive ring and pinion set.

The following chart shows the RPM loss in each gear, assuming a 6,500 rpm shift:



Notice that only the Custom MN6 with the 0.563:1 sixth gear keeps its rpms above the torque peak after the 5th to 6th gear shift. You can see by the chart that both the standard MN6 and the MN12 let the rpms drop far below the torque peak. That's part of the reason Corvettes with standard or close to standard horsepower cannot pull as much speed in 6th gear as they do in 5th gear.


This next chart outlines the changes in gear ratios that I have versus the stock MN12 with a 3.42:1 final drive:



My LS6 has a little over 400 RWHP, and it peaks power at 6,250 rpms. I have been over 180 mph here in Michigan - 700 to 800 feet above sea level - several times in 6th gear and the Z06 was still accelerating. Each time I ran out of road and had to slow down. My goal is to add enough horsepower to be able to exceed 200 mph. With my existing gearing, I will be turning ~ 6,000 rpms at 200 mph in 6th gear. I believe I need approximately 475 RWHP at 6,000 rpms to achieve my goal.

I agree with Jeff. You need to experience the real world in order to understand what it takes in terms of gearing, aerodynamics, and horsepower to go really fast.

 

Interesting.

 

Well, believe it or not the physics say you would need about 425 rwhp at sea-level. Of course this would have to be right at 6000 RPM in your 6th gear as you've described. So what RPM were you at when you hit 180 MPH … and how does that equate to the actual RWHP being made at that RPM and in the air conditions you were running? These factors are what skews the model (which takes these things into account) unless all those parameters are known.

I agree ... but it is also helpful to understand all the physics involved in order to make your car take full advantage of the RWHP. In your case, your car will be geared near perfectly to achieve 200 MPH, and therefore you probably won't need quite 475 RWHP @ 6000 RPM in 6th gear. Of course, having extra is always a good thing for the unknowns.

 

But since your 5th and 6th gear sets are custom made, it isn't really possible to say that bone stock 6th gear will also survive just because yours do. It's really an apples to oranges comparison. BTW, I'm sure the stock 6th gear can take some abuse.

 

what is the cost of custom 5th and 6th? why not leave the rear end stock and cut 6th to say .64 or what ever is required to hit 21x mph with out altering the 3.42s?

 

...

 

You could leave the diff with a 3.42:1 ring and pinion and change 5th gear to 0.80:1 and 6th gear to 0.667:1. This would give you the same final overall gear ratio that I presently have.

If you went with that package, you would loose the greatly improved acceleration that I have through the first four gears with the 4.10:1 gears.

Liberty Transmission charges ~ $2,300 for the package they made for me.

 

Running the numbers says you would need about 325 rwhp to do 180 mph at that elevation and air temp … but you said you were still accelerating which makes sense because you were still making about 45 more rwhp than you need at 180 mph.

As you can see, this stuff correlates pretty well.

 

This has been an interesting thread I haven't said much lately because I don't really have any experience in this field. Especially the technical part of it. It's been a good read though~thanks