Corvette Z06 Forum banner
1 - 20 of 22 Posts

·
Registered
Joined
·
644 Posts
Discussion Starter · #1 ·
While driving thru the AZ desert on I-8, I reached 150mph at about 6200 rpm, the HUD displayed shift up, so I did - then went into 6th, I could not pass 165mph.

On the next few runs, I ignored the shift up and stayed in 5th and achieved in the ranged of 165 - 175mph.

I gather 6th gear is a fuel saving/cruising gear?
 

·
Registered
Joined
·
2,388 Posts
6th gear is too high so the engine will not "pull" like in 5th gear. In other words, the aerodynamic drag at high speed is too high to overcome when in 6th gear.

6th gear is a "double overdrive" gear, and is strickly for economy.

The Z will pull very near red-line in 5th gear, which is ~175 MPH :D.
 

·
Registered
Joined
·
644 Posts
Discussion Starter · #3 ·
ZeeOhSix,

thanks for the confirmation. Yeah, I was in 5th gear when I hit 175mph. Is this the absolute max speed on a stock Z06, going in 5th gear?
 

·
Z06 Maniac!!
Joined
·
1,541 Posts
At the rev limiter in 5th (6600 rpms), my speedo showed an indicated 177. When I checked my speedo against a GPS at 100 mph, they both read the same, so 177 is probably very accurate as the rev limited top speed. I think a stock Z06, either an '01 or '02, would be able to pull to the rev limiter in 5th and hit 177. Some on this Forum calculating tire size, gear ratios, rpms, etc. theorize that while my speedo showed 177, I may have been going about 180 at 6600 rpms. I haven't yet tested the GPS to that point, but maybe next summer.:cheers:
 

·
Registered
Joined
·
2,388 Posts
Rippied -- I've also ran the theoretical top speed using gear ratios, engine RPM and rear tire's actual rolling circumference (80.50 inches).

I got 175.1 MPH at 6600 RPMs in 5th gear.

Only thing I didn't account for was tire growth at top speed, which might add a few MPH.

You need to bring your GPS next time you go rev-limiter in 5th :D.
 

·
Registered
Joined
·
2,616 Posts
TOP SPEED IN 6TH GEAR WITH A MODED Z ??

Has anyone with a highly modded Z tested top speed in 6th gear?

Still limited to 165mph?

Assuming stock tire size and gears does anyone know how to calculate top speed mathematically? I suppose you'd need to know air drag #'s, frontal area and coefficient of drag, AND assume no wind?

Anybody know the answers?!

:cheers:
Barrie
 

·
Registered
Joined
·
2,388 Posts
Re: TOP SPEED IN 6TH GEAR WITH A MODED Z ??

01ZEE06 said:
Has anyone with a highly modded Z tested top speed in 6th gear?

Still limited to 165mph?

Assuming stock tire size and gears does anyone know how to calculate top speed mathematically? I suppose you'd need to know air drag #'s, frontal area and coefficient of drag, AND assume no wind?

Anybody know the answers?!

:cheers:
Barrie
Yup, I know the answers :D.

In order to pull 6th gear above 175 MPH, you would need ALOT of RWHP! This is how the stock Z is geared for speed at 6600 RPMs (red-line). This is using gear ratios and rolling circumference of 80.50 inches (measered this myself).

1st gear .... 49.5 MPH
2nd ........... 71.1
3rd ............ 102.9
4th ............ 147.1
5th ............ 175.1
6th ............ 262.7

Now this is the required RWHP to go these speeds. This is accounting for aerodynamic and rolling resistance of a Z06.

49.5 MPH ... 27.4 RWHP
71.1 ........... 47.3
102.9 ......... 92.9
147.1 ......... 202.6
175.1 ......... 309.0
262.7 ......... 896.0 <---- :eek: now you see what I mean!

You have to keep in mind that the required RWHP has to occur at the engine RPMs which the gearing allows the car to travel. The peak RWHP is not at rev-limiter, but below it slightly. So at 6600 RPMs (175 MPH in 6th gear) the RWHP is probably pretty close to the 309 figure shown above. A good dyno chart should show what the RWHP is at 6600 RPMs :D.

Anyway, you can clearly see that GM did not intend to use 6th gear to obtain max speed that the RWHP would allow -- its really just a "double over-drive" gear for econmomy only.
 

·
Registered
Joined
·
508 Posts
hmmmm a 260 mph 900 hp z06....

EEK!

gotta go walk around a bit to shake off the heebie jeebies

:lol:

Could you imagine how jittery that would be... heh heh


ps. cool stats BTW
 

·
Registered
Joined
·
2,616 Posts
ZeeOhSix,

WOW!! Thanks for the fast feedback.....Real Kewl info :cool: That would be about 1,054 crank hp......!!

Can you calculate how much rwhp it would take for 6th gear to equal 5th gear's max of 175.1 mph? And what would it take top out at 200mph in 6th gear?

I promise this will be my last request! It's really great to have someone who knows how to cook these numbers!




:guiness:
Barrie
 

·
Registered
Joined
·
2,616 Posts
Roger,

How did you take that picture. Looks like the Camera had to be in your mouth.....you did have both hands on the wheel didn't you?

I don't think I'd wanna go that fast on such a narrow road with a lot of TREES on the sidelines. Were those speed limit signs coming up on both sides of the road? Gotta be there for a reason.....like an upcoming Hazard area.

Looking down the road, it looks like a curve coming up in say 800-900 feet. At 177 miles per hour that's 260 feet per second. So in 3-4 seconds you'll be there? WOW, too fast for me. Some poor farmer could be crossing the road.....or a lady taking her kids to the store.....I dunno, looks pretty damn scary to me.

I thought the HUD also displays the Tach and some other gauges.....don't see 'em in your picture.

Just like the jet in your rear view mirror, I don't think it happened!! Are you convicted?! Also, at 177mph, I wonder why the picture is so clear.....seems like things would be bouncing an jiggling too much for such a clear shot!

You playing with us Roger?!

Just hard to believe,
Barrie
 

·
Registered
Joined
·
508 Posts
01ZEE06 said:
Roger,

How did you take that picture. Looks like the Camera had to be in your mouth.....you did have both hands on the wheel didn't you?

I don't think I'd wanna go that fast on such a narrow road with a lot of TREES on the sidelines. Were those speed limit signs coming up on both sides of the road? Gotta be there for a reason.....like an upcoming Hazard area.

Looking down the road, it looks like a curve coming up in say 800-900 feet. At 177 miles per hour that's 260 feet per second. So in 3-4 seconds you'll be there? WOW, too fast for me. Some poor farmer could be crossing the road.....or a lady taking her kids to the store.....I dunno, looks pretty damn scary to me.

I thought the HUD also displays the Tach and some other gauges.....don't see 'em in your picture.

Just like the jet in your rear view mirror, I don't think it happened!! Are you convicted?! Also, at 177mph, I wonder why the picture is so clear.....seems like things would be bouncing an jiggling too much for such a clear shot!

You playing with us Roger?!

Just hard to believe,
Barrie
:lol: :lol:

Barrie try here... he pulled this one a while back and there is thread:
Link to Roger Ramjet record speed shot

Bet he is laughing that the debate is struck up again.
:cheers:
 

·
Registered
Joined
·
2,616 Posts
YOU GOTTA WATCH OUT FOR ROGER RABBIT!!

Ice,

Thanks Bro, I missed that thread.:D

Now we know "the rest of the story" :lol: :lol: :lol: :lol: :lol: :lol:

:guiness:
Barrie
 

·
Registered
Joined
·
2,388 Posts
01ZEE06 said:
ZeeOhSix,

WOW!! Thanks for the fast feedback.....Real Kewl info :cool: That would be about 1,054 crank hp......!!

Can you calculate how much rwhp it would take for 6th gear to equal 5th gear's max of 175.1 mph? And what would it take top out at 200mph in 6th gear?

I promise this will be my last request! It's really great to have someone who knows how to cook these numbers!




:guiness:
Barrie
I'm not quite sure what your after here, but here's my answers :D.

Regaurdless of what gear your in, it takes a certain amount of RWHP to go a certain speed. For instance, it takes 309 RWHP to go 175 MPH, and it takes 433 RWHP to go 200 MPH in a Z06.

In 6th gear at 175 MPH, the engine RPMs is 4400.
In 6th gear at 200 MPH, the engine RPMs is 5030.

So, with stock gearing, the engine would have to be able to supply 309 RWHP at 4400 RPMs to go 175 MPH in 6th gear. Likewise, with stock gearing the engine would have to be able to supply 433 RWHP at 5030 RPMs to be able to go 200 MPH in 6th gear.

Obvioulsly the LS6's peak HP is higher than 5000 RPMs, so for a stock geared Z06 to go 200 MPH in 6th gear would probalby be putting out about 500+ peak RWHP :D.

Hope that's what you where asking :)

:cheers:
 

·
Registered
Joined
·
644 Posts
Discussion Starter · #16 ·
GM says that the top speed limit on the Z06 is 170+. So far we have 177mph (w/o mods?) BTW, my 175mph included 2 passengers and some luggage in the rear compartment. Has anyone reached the limit, regardless of whether or not in 5th or 6th. The avg. outside temp at the time of my run was clear skies at 56F degrees.
 

·
Registered
Joined
·
2,616 Posts
200 mph in 6th gear.....

ZeeOhSix,

Yup!! Thank You :)

It seems to me that if you want to go faster than 177 mph with stock gearing, you'll need to achieve this goal in 6th gear. So, I was wondering how much rwhp(approx.) you would need to reach 200mph in 6th gear.

I've seen a couple of reports of Z06's with 446 rwhp with heads and cam work, and just about every bolt on known to exist. I believe our friend Darth Vetter claims 446 rwhp, but I don't see any Dyno Data in the PDC.

Horsepower peaks at close to 6,000 rpm.....

Soooo, to go 200mph in 6th gear, we will need all of the above and more displacement or some form of forced induction or Nitrous.

But, it could be done :D

THANK YOU!!

:guiness:
Barrie
 

·
Registered
Joined
·
2,388 Posts
z06175mph said:
GM says that the top speed limit on the Z06 is 170+. So far we have 177mph (w/o mods?) BTW, my 175mph included 2 passengers and some luggage in the rear compartment. Has anyone reached the limit, regardless of whether or not in 5th or 6th. The avg. outside temp at the time of my run was clear skies at 56F degrees.
Z06175 brings up a good point, and that is that air density does have an effect on top speed. The colder (denser) the air, the more HP is needed to go the same speed. But wait you say .... a NA engine makes more HP when its cold out. This is true, BUT the extra HP required to go a certain speed is nearly identical the extra HP made by the engine when cold. The end result is thats is basically a wash. It may not seem apparent at first, but the obtainable top speed is basically the same (within 1~2 MPH) at sea-level as it is at say 5000 ft. Believe it or not, you will go a few MPH faster when its very hot outside -- like 90+ deg F air vs. say 50 deg F air.

BTW -- the only thing added weight in the car does is make it take longer to obain top speed and add just a hair more rolling resistance. Added weight does not effect the aerodymanic drag, which is ~80% of the total HP requirement. Rolling resistance at say 200 MPH is ~20% of the total RWHP :D.
 

·
Registered
Joined
·
2,388 Posts
Re: 200 mph in 6th gear.....

01ZEE06 said:
It seems to me that if you want to go faster than 177 mph with stock gearing, you'll need to achieve this goal in 6th gear. So, I was wondering how much rwhp(approx.) you would need to reach 200mph in 6th gear.
Thats correct ... or you could put in lower ratio rear end.

If you put a 2.73 rear end (basic coupe rear end), then in 5th gear at 6000 RPMs you would be going 200 MPH. You would still need the 433 RWHP at 6000 RPMs of course ... which would be easier to achieve than 433 RWHP at 5000 RPMs in 6th gear per my previous example :D.
 
1 - 20 of 22 Posts
Top