I wish I could have a highway all to myself for 2 minutes. One minute to run flat out, and another minute to slow down! It would require more than a mile, like 2-3? Maybe the proper way is one of those events in Nevada for like 100 miles, and sneak in a banzai run in the middle.

I use an old simulator called Cartest, it's reasonably accurate. It uses drag coefficient as part of the equation. With my setup it reports these numbers:

1/4 mile, 10.8 seconds, 137mph
1 mile, 27 seconds, 195mph
2 miles, 45 seconds, 210mph

I know the 1/4 is right on. I wonder how close the 1-2 mile numbers are.

 

Yeah sorry, I meant....Actually I don't know what I meant. I do know that the Procharger helps at all rpms. It pulls hard at 60 in 6th gear. In any gear at any time I feel a huge difference over stock. I worded it wrong but I guess I was saying the Procharger would help me gain speed in 6th & it really loves high speed rpms

 

Nice #'s Chris! That must be a blast to drive I'm pretty much right at the limit with the stock bottom end. I may go with a forged 346 w/ Heads & Cam + bump the procharger up to 15 psi in the future. We'll see. Anyway, thanks for the statistics

 

So you were at the top of 5th when you shifted into 6th? Did the car bog down at first when you went into 6th? Do you remember what rpm it drop to after the shift? Thanks...

 

That would be a great response to this thread... I would love to know what RPM he dropped down to when going into 6th with his power. I hope he see's this and answers your question.

 

Did it give an ultimate top end speed? Also, what Cd and A values where used?

My calcs say with 700 rwhp it's "capable" of going 240 MPH with gearing perfectly matched for top end runs.

 

ZeeOSix,
I don't care what your gearing is 700rwhp will not get you to 240mph. We have had many cars with over 1000rwhp race with us and the highest offical speed is 227mph and the highest GPS recorded speed is 232mph. Those speed calculators are fine, but are not real life.

This is the car that hold these records, It is not the car that holds the highest average though. That was a Chrysler LeBarron (ex Bush Grand National race car) at a 207.XX average for the 90 miles. The day that the record was set Rick Doria (owner/driver of red Vette below) was 2-5 mph faster through all the speed traps he passed to the 65mile mark. Then some how a truck pulling a boat on a trailer got through a locked gate onto the coarse. Rick got red flaged which threw out the fastest 1/3 of the run and he was going into the slowest(most turns) 1/3 of the course so was unable to set a new record.




I believe he was running about 850-900rwhp to post those numbers.
Jeffy'

 

Don't worry, I understand the models are only that ... BUT, I'm going to step out on a limb here and say I'd bet those cars were not geared perfectly to take full advantage of their RWHP, and/or they didn't have enough running room to achieve the true terminal speed. If the gearing is not setup perfectly for a true top speed run, they you will lose big MPH on the top end.

Also, the model does not account for tire spin when running on a surface like the salt flats. Of course this will hinder top end speed dramatically if traction is not ideal. The numbers I’m showing from the top end model are the theoretical maximum you could ever achieve if everything was perfect … that’s all.

 

Yeah the max speed showed like 220mph. It used 0.31 for the Cd of Z06, but did not ask for A.

 

To get anywhere near your perfect numbers you need a rocket shaped car.
These guys have been doing this for a lot of years and have played with many gear ratios. So this whole perfect gear ratio line I am not sure I buy. Running top speed is what we do and have worked at for years. As for not enough room to reach terminal speed, they are on a 16 mile straight. They are making turn at 200+ though, that is not a talent I have achevied yet(probably never will).
The factor you have not discussed and I will grant you is that we run at 4-5000 ft elevation. We are in the high desert of Nevada. The fastest of the courses we run starts at 5500ft and drops to 3000ft in the 90 miles.
Jeffy'

 

I've got an '03 Z06 making around 395 rwhp and have maxed it out at the top of 5th with a GPS indicated 174mph, 169 on the speedo. For grins, I dropped it down to 6th to see what speed it could maintained. With the pedal floored in 6th, my speed dropped to 160 mph. Car felt pretty good - it's lowered a bit running Pfadt coilovers and sways.

 

The top speed model accounts for the shape of the car through the CdA factor. Of course, actual wind tunnel data would be required for an accurate analysis. With a "rocket shaped car" (ie, streamliner) the same amount of RWHP would propel the car even faster. As an extreme example, if the CdA was cut in half, a vehicle could go the same speed with half the RWHP.

Gearing is everything in order to take full advantage of the true capability of the car (ie, HP and aerodynamics) in order to achieve the maximum possible top speed.

Yes, running at high elevation will cut the top speed down quite a bit as NA engines loose quite a bit of HP at higher elevation. Of course the aerodynamic drag is less also as the air is thinner. My calcs were running at sea-level.

 

450 rwhp took me to 189 stock body.

 

Hi John,

You reached this top speed in a Coupe I presume...what revs and what gearing??

Stock drive train stock tires in a ZO6 187mph is 7180rpm in 5th gear!!!

Christian

 

3:42 at redline which is 6800 or 6900. The road was ROUGH I think it went airborne and traction control shut down the engine, air bridge blew off and I about Chit so when it redlined I was done. I really could not tell you what happen first. Car went into limp mode I guess because of air bridge. Very rough track

 

I hope the limb is over a nice soft pile of leaves..... The car Jeffy is refering to has 2.73 rear gears and ran at 6200 rpm in 5th gear. (.75) This is where the motor made top HP. (630rwhp) And as Jeffy also stated our corner exit speeds were 200mph onto a 16 mile straight. Our in car data showed 232mph at some points, but we passed the official radar at 227mph.

As far as the whole 5th or 6th gear question goes, you need more info on the motor. *IF* your motor makes max HP at 6500 you will be maxed out at APPROXIMATELY 185 mph. *IF* you then shift into 6th gear your engine will only be turning ABOUT 4300rpm. My *GUESS* is you will fall way off the power curve and the car will SLOW DOWN. *IF* you are making over 500rwhp at 4300rpm (you must have a blower, right?) I *THINK* you *may* be able to hit 200 mph. (about 4600 rpm)

Rick

 

That makes sense. I agree that 200 should be reached with that kind of HP. As I said earlier, my Z06 is still pulling hard when I shift into 6th gear. I just haven't stayed on it for very long. I really believe I could go atleast 200 if not a little more. Maybe one day I'll find out after I get some aero mods.

 

Question......anyone experience the side windows trying to "pop out" at these speeds?
I spoke with a friend over the weekend, we were discussing how fast we've had our cars. He said that he's had his up to 173 with a few hundred rpm to go but he was afraid of breaking a window, as they were "sucking outward pretty bad". I asked if he was missing the window tabs (or what ever they are called) he said he wasn't missing them..........he did mention that the car felt pretty stable though.
Just wondering if aynone else has had this issue.

On a side note I asked about the 6th gear not being able to handle power for top speed runs..............he called BS....just as I figured.

 

Just because he was running in 5th gear at max HP RPM (6200) doesn't mean it couldn't do better if geared slightly higher ... unless of course 232 mph happens to be the ultimate top speed that 630 rwhp will overcome the aeros of that car in the air conditions he was in.

The way this works is you first determine theoretically how fast a vehicle is capable of based on the peak RWHP (at xyz RPM) and the aerodynamics of the car and air conditions, then you gear for that target top end speed. If the vehicle doesn't do it, then you regear to "tune" the gearing to match the peak RWHP to achieve the maximum speed possible.

Think of it this way. Lets say you had the ability to infinitely and quickly adjust the gear ratio on the fly. If you were out on an infinite straight road, and the engine was held constantly at the peak HP output RPM, then you would adjusted the gear ratio up and down until you found the peak top speed. This exercise would have matched the gearing perfectly to the peak HP and aerodynamic conditions of the vehicle.

Now from what I read about the car Jeffy's is talking about above, you said it did 232 mph with 630 rwhp. Well, that's basically in the same ball park as being able to do 240 mph with 700 rwhp. My calcs show a max top speed of 228 mph with 630 rwhp … only 4 mph off of what you actually measured ... so I guess that limb is pretty stout and in no danger of snapping as far as I can see.

BTW -- I originally didn't account for the vehicle's weight in the model for the rolling resistance factor on the 700 rwhp calc. The new number is 237 mph with 700 rwhp at sea-level type air conditions.

 

The most I ever took mine up to was 160. At that speed my C5Z felt very secure and stable, I was very surprised at how smooth she was I don't know about 170+ mph but from what I gathered at 160 I would amagine 170+ would feel the same way.
Maybe someone who has taken their Vette past 180 could chime in on that one.