Car is a 2007 Z51 with manual transmission. Mods are Kooks headers and catted X-pipe, Callaway CAI, 160 thermo, Cartek Tune - 384.5 rwhp, 373.7 tq). Assuming the above AND a gear change to 4:10's, am I correct:

1. that the mathematical maximum speed (gear limited) that can be acheived with a six speed manual car is now approximately 205 mph?

2. that maximum speed will now be acheived in sixth gear?

3. that maximum speed should increase (above 186 mph) because of the more useable and, now useful, sixth gear? If you agree and YOU KNOW FROM EXPERIENCE what the new top speed is (appx), please advise.

4. that I should just stop worrying about it and schedule the damn appointment already?

(Really, I need answers to 1-3, I think 4 is a forgone conclusion)

 

1. Redline in 6th gear would be about 217 MPH.
2. Yes. 6th is the new 5th.
3. Maybe, maybe not. If the top speed was 186 MPH @ 5800 RPM in 5th with the 3.42 gears, then you're looking at 186 MPH @ 5600 RPM in 6th with the 4.10 gears. You should have a little more torque available at that point, so you should be able to get a little more speed. The same 5800 RPM would yield 194 MPH. So split the difference and call it 190 MPH.

Actual top speed is going to depend on the temperature, humidity and possibly phase of the moon.

 

1. 221 MPH using 6500 RPM redline in 6th gear. For any other RPM, divide 221 by 6500 and multiply by the new RPM. Using 6000 RPM gives (221/6500)*6000= 204 MPH.

2&3. Depends on your dyno curve. You'll get to 177 MPH in 5th at 6500 RPM assuming you have enough HP at 6500 RPM. I would guess you do but it might be close...either way, you'll accelerate very quickly through 5th. At 177 MPH, a shift to 6th will drop you to ~5200 RPM where you may not have the HP to pull it and you'll see your speed start dropping, but again I think you'll have enough. From there, it's a matter of the engine's HP staying more than aero drag HP (until you reach peak HP RPM) to keep accelerating but it'll be a very slow (almost painful) acceleration as you'll barely have more engine HP than aero HP required. It might take 10 miles or more to get there. A bump in the rev limiter to get more out of 5th may be needed to get the engine HP up on top of the aero HP in order to keep accelerating in 6th. Like I said, it depends on the dyno curve...if you have a peaky curve where HP comes up and falls off pretty quickly, your top end will be in 5th at less than 177 MPH. If its' fairly flat, you'll keep accelerating in 6th but you may not even make it to 186 MPH because aero HP will be increasing faster than engine HP and you'll never reach the RPM at which you make your peak HP. In other words, the car may have a slower top end. If you're making more than ~350 RWHP at 5500 RPM after your mods, then you'll keep accelerating past 186 MPH but not much more. To optimize top speed, you have to gear the car so that top end occurs at the RPM that peak HP occurs. If your HP peaks at the same 6000 RPM of the stock LS2, you would get 204 MPH in 6th with 4.10s, but there's no way 384 RWHP will push that car 204 MPH...the Z06 takes ~450 RWHP to go 198 MPH (and yes, I know it's not as aero as the coupe).

4. Yes, go for it and stop worrying about top end...not many places to do it and not many races go past 170 MPH and that's a place for fools anyway. At 180 MPH, it'll take you 1100 ft to come to a stop and that's if everything works right...think about it for a minute. Almost the length of a drag strip and even at the half way mark (550 FT) you're still going over 120 MPH.

 

Where in the hell are you going to be able to test at 200 mph?
The only place I know would be the open road races in Nevada and Texas, but your going to have to spend some money on safety equipment to make the 200 mph club. My ZR1 has run 182 mph in 5th gear at 7,000 rpms with 3:45 gears outback. The general rule of thumb with open road racers is, it takes at least 500 hp to run 200 mph and they don't run 4:10's outback. The car would way overheat on 100 to 130 mile races.

 

1. Mathematical maximum of 205- I'll agree there. It's only a mathematical max, however.

2. I do think your max speed will be achieved in 6th- however, as others have said, there are factors that will determine if the car can hold the speed for long, or if it'll drop off.

3. If the car can pull 6th, you should be able to see low 190's, if all the stars line up.

4. Don't know what your appointment is, but whenever you get a chance to run flat out, yes- schedule it!

I base my answers from a decent amount of experience running these speeds, and participating in events where these speeds are regularly run. I don't think you'll see 200. However, I have seen a mostly stock C6 Z06 run right at 200 for a brief period.

At those speeds, watch your oil temps, and diff/trans temps. And know that your tires will always be the most critical thing to consider, aside from keeping it on the road.

One thing I will offer, if you run into frustration getting into the high 190's- it ain't as easy as it looks on paper, believe me. People spend years and way too much money to get that 200 number- you won't be the first to encounter the difficulties of getting into the 200MPH club.

Cheers-
scotty
200MPH Club Member
Silver State Classic (217MPH)
US Autobahn Series (214MPH)
Big Bend Open Road Race (204 MPH)

 

Scotty what car were you running at the USAS events? I was at the Bonnieville 100 and the Pony Express 130. I ran the 07 at Bonnieville and the ZR1 at the Pony.

 

I used to have a vdeo of a front street tire shredding at right around 200mph on a Ferrari. It's not pretty. Stay safe guys.

 

If you have Excel, use this nifty spread sheet program to plug in different rear end ratios, ect.

BJK

 

Tranny and rear temps escalate greatly at those speeds. I have a gauge on both, and a tranny cooler, but my rear was getting close to 300 after a half hour of track time at 100+ . A diff cooler is a must if you want to run those speeds. When I slowed down temp went right down.

 

I'm sure we've met at some point! I was at the B100 this year helping run a speed trap for the timing and scoring crew (Dabney). Been doing it for years. Used to run with Todd in the black Camaro in UNL. We made a few fast passes.

I missed the Pony last year, but plan on running all MKM and BBORR events this year in my 06 C6 Coupe. No SSCC events any more for this guy.

 

i took my c6 out on a run with some local motorcyle friends and on a local bridge i hit 186mph according to the HUD..... and the car was still pulling pretty good considering the gear/speed..... wouldnt try it again on local roads because afterwords when i was swapping my street tires for my drag radials i noticed blistering and patches of rubber missing from my street tires

 

Max speed by the math at 6500 is 217 not 205. Mine is 100mph@3000 and it was 201 at 6050 or so. 6600 would be 220 so 217 at 6500 is about right. The power you will need is a different story though. My 2001 with 441rwhp and 404TQ took forever to get to 190 in sixth.

All of this of course assumes the transmission is not a base transmission which then adds 12% to the max speeds. The Z51 is 200 at about 6000rpms but the base transmission would be at 4800-4900 or so and wont do it. I had an M12 in the coupe and I have the MZ6 in the C6. The tire diameter is also a variable. A severely worn set of 305 pilot sports would be less than 25.6" while a new set of SC-runflats is 26.9.

Top speed in 6th with the base transmission would have a theoretical limit by gear in the high 230's. That transmission tends to need pretty close to 500HP to break through with 4.10's because its lower in rpm. The Z06 does it with a little less becasue of the higher rpm in 5th.

S/C guys have an easy time of it from the ever increasing power up top and most even with the base transmission report it is at or near 200. NeptuneBill is one forum member that comes to mind.

Basically the Z51 guys with 4.10's have an easy time of it. At that point I would assume any aggressive head/cam car would make it there. The biggest problem with a stcok cammed car is the 5800 rpm HP peak.

 

Here's my favorite gear ratio calculator.

http://www.xse.com/leres/ss/calculator.html

 

Please don't do those speeds on public roads without the proper safety equipment. Your stock belts just don't cut it, if it goes south on ya. The bright side is you do have venues to do those kind of speeds legally. Yes there are entry fees and safety equipment requirements for the speed class you choose to run in, but way cheaper than a ticket could be. They also have air ambulances and fire rescue on sight.

 

Scotty will make all three USAS events next year and the SORC. Hope to see ya there.

 

How would you go about calcualting top speed of an A6 w/ 2.56 gear and 6600 rpm red line? 450rwhp, so about 525bhp.Stock 19 inch rear tires.

 

You're selling yourself short! If you've got 450rwhp with an A6, you will be about 560bhp. Most use a 1.25x factor for the A6 to get rwhp to bhp.

As for speed... plenty!

 

Actual top speed really depends on the driver.....and how big his b**** are. It's faster than you think when you break 150 mph. Every 10mph seems like much more. That being said...when I put 4.10's in my car they told me the car could probably hit 200. I also had heads/cam and a 7000rpm redline. As far as I know the installer was speaking from actual speeds he had obtained with similar cars I don't have what it takes to hit 200 anymore....i'm a big chicken...or older and wiser with kids

 

I'm glad you find it useful. There's an update here -- http://bolero.csustan.edu/C6/C6_Gears.xls -- with a built-in tire diameter calculation. I added a ZR1 and my A6 w/Kumho 710s also.

--Dan

 

Everyone keeps talking about how fast they can go with certain gears. However, do not forget it takes more power to go faster. The amount of power required goes up on the cube of the speed. So if you are putting out 385 rwhp versus a stock car with 350, that is only 10% more power or 1.10. However, since it's a cube law, take 1.10 to the .33333 power gives 1.032. 1.032 times 186 mph gives 192 mph.

If you want to go 204 mph, you will need (204/186)^3 = 1.32 x 350 = 462 rwhp. And you need to put out this power at the rpm the engine is turning at 204 mph.