LS-7 200MPH

[syuek]

Hi to all I'm new to this forum but been ghost reader for quite a while. I'm about to start my build soon as builder is decided. Specs are about set. I have a question about LS-7 and 200MPH top speed.

(Corvette Z06)
ENGINE
Type: V-8, aluminum block and heads
Bore x stroke: 4.13 x 4.00 in, 104.8 x 101.6mm
Displacement: 428 cu in, 7008cc
Compression ratio: 11.0:1
Fuel-delivery system: port injection
Valve gear: pushrods, 2 valves per cylinder, hydraulic lifters
Power (SAE net): 505 bhp @ 6300 rpm
Torque (SAE net): 470 lb-ft @ 4800 rpm
Redline: 7000 rpm

DRIVETRAIN
Transmission: 6-speed manual
Final-drive ratio: 3.42:1, limited slip
Gear - Ratio - Mph/1000 rpm - Speed in gears
I - 2.66 - 8.4 - 59 mph (7000 rpm)
II - 1.78 - 12.6 - 88 mph (7000 rpm)
III - 1.30 - 17.3 - 121 mph (7000 rpm)
IV - 1.00 - 22.4 - 157 mph (7000 rpm)
V - 0.74 - 30.3 - 198 mph (6500 rpm)
VI - 0.50 - 44.9 - 160 mph (3600 rpm)

C/D TEST RESULTS
ACCELERATION: Seconds
Zero to 30 mph: 1.6
40 mph: 2.2
50 mph: 2.8
60 mph: 3.6
70 mph: 4.5
80 mph: 5.5
90 mph: 6.7
100 mph: 7.9
110 mph: 9.3
120 mph: 11.0
130 mph: 12.8
140 mph: 15.0
150 mph: 17.5
Street start, 5-60 mph: 4.3
Top-gear acceleration, 30-50 mph: 12.9
50-70 mph: 10.6
Standing 1/4-mile: 11.7 sec @ 125 mph
Top speed (drag limited, mfr's claim): 198 mph

with curve weight of 3147 lb Z06 is almost at 200MPH, now for sake of argument same gear ratios in a Ultima GTR with better aero then Corvettes Cd (0.34) versuses I believe Cd (0.333) with 0 degree wing angles for the Ultima and about 2200 ibs for Ultima where as Z06 is at 3147ibs. So with base Z06 engine and similar gearing as in Z06 should produce an easy 200MPH car am I wrong?? my car will have more HP but just trying to figure out my gearing for the 6speed. I'm definetly going to use taller first gear something in the neighborhood of 2.250?? any advices will be appreciated.


Stan

[CarMad426]

I worked out using a program called Cartest 2000 that you should be able to go 202mph with the ZO6 engine and gear ratios with 325/30ZR19 tyres same as the Zo6.

[syuek]

Thanks for that I thought it will go little further top end wise with diffrence in weight and other things considered. Quite interesting!

[peterpsg]

Don't assume any figures for the aero, since as the factory have yet to publish any, and given the design is now 8 years old, one would have to assume that they don't know either, otherwise they would have released them by now !!!

Optimal gearing would help, but I had 510 bhp, and 470ft, and with my gearbox, a 6 speed G50/21, I'd to be perfectly honest I'd have been surprised if the car got to 200, although getting to 180 was a doddle... so if you add a 100-200 NOS kit for the top end, you'll see 200 easy...

Edited by peterpsg on Monday 1st October 20:33

[Steve_D]

peterpsg said:

Don't assume any figures for the aero, since as the factory have yet to publish any, and given the design is now 8 years old, one would have to assume that they don't know either, otherwise they would have released them by now !!!

I have posted this before but can't be asked to find the thread so here goes again.
This was the mail I received from Ted.
"Steve

Just thought I would let you know in light of recent postings on Piston Heads that I am unable to recall anybody that has actually ever asked the factory for the wind tunnel figures pertaining to their Ultima so I thought I would let you know some of the more relevant results so that you could pass them on if anybody is interested.

Basically the CD of an Ultima is not a fixed figure like it is on the majority of cars but varies considerably with the wing settings and splitter options.

For the record a standard Ultima GTR with no wing or splitter but with standard grills, door mirrors, wiper and standard ride height variation front to rear is 0.336 according to MIRA.

Perhaps the most relevant figure for the purposes of the V max recently discussed is the power required for 200mph.

For an Ultima with an Ultima front splitter and with the standard wing set at zero degrees without the flap the rear wheel bhp required to overcome the wind resistance alone is 404 rear wheel bhp according to the MIRA results. The friction losses and any power lost through the drive train will have to be estimated and added to this figure.

With regards to down force the highest figure that the double element wing and Ultima front splitter recorded was 940lbs at 200mph but the best combination for a balanced front and rear down force was achieved using the front splitter and the rear wing set at zero degrees with no flap. This gave 123lbs down force on the front with 134lbs on the rear and this is our recommended settings for high speed runs.

The results of the wind tunnel test do not of course estimate the time required to reach 200mph or the distance that will be covered during acceleration.

Incidentally the power to overcome the wind resistance with the same configuration at 100mph is only 50bhp.

If anybody with an Ultima wants specific figures for particular set ups all they have to do is ask the factory.

Our aim is to provide the highest levels of customer service possible at all times.

Best regards
Ted Marlow"

Steve

[peterpsg]

Once again, SteveD is the man!

[syuek]

Hi peter
My question still is based on given specs of Z06 and some of the advantages Ultima has
in weight to power ratio with better or similar aero package GTR should see 200 MPH quite
easily. After all numbers for the Z06 have been tested enough times by reputable outfit
to be taken seriously. Because if you striped close to 950ibs off of current Z06 weight I'm sure it
will touch other side of 200MPH.

[GTRCLIVE]

Getting any decent gear ratios on a box that will take the power is very expensive. 545bhp is enough to break 200 mph as long as the gearing as right, but on the aero front I think a GTR maybe worse on the Drag front... the vette is very streamlined...
We need to convince Tremek to make a transaxle, then it may be cheaper....

[andygtt]

weight has little to do with top speed (within reason)... its the CD and bhp that really matters.

Of cause you need the correct gearing to ensure the power is in the right place to acheive the desired speed which is why the gearing is very important.

Gear it right and given enough distance a Z06 powered ultima will do 200mph quite easily IMO.

[rduart]

Before I start I am not a aerodynamic engineer. I found these formulas in a book I have been reading by Simon McBeath. You might find these two formulas useful or at least interesting. You will need the coefficient of drag (cd), frontal area, bhp, and expected max speed. As Ted said, you will need to estimate the power loss you will have in the drive train and add it back. Of course this will only provides a theoretical answer to the question. Others have already provided the most meaningful information on this topic already.

          _____ 
        3/
vmax = \/((bhp * 146600)/(cd * Frontal Area in Sq Ft))

                 3
bhp = cd X Frontal Area in Sq Ft X (Desired Max Speed)
      ----------------------------------------
       146600  

Randy

[rduart]

rduart said:

Before I start I am not a aerodynamic engineer. I found these formulas in a book I have been reading by Simon McBeath. You might find these two formulas useful or at least interesting. You will need the coefficient of drag (cd), frontal area, bhp, and expected max speed. As Ted said, you will need to estimate the power loss you will have in the drive train and add it back. Of course this will only provides a theoretical answer to the question. Others have already provided the most meaningful information on this topic already.

          _____ 
        3/
vmax = \/((bhp * 146600)/(cd * Frontal Area in Sq Ft))

                   3
bhp = cd X Frontal Area in Sq Ft X (Desired Max Speed)
      ----------------------------------------
       146600  

Randy

Sorry I just noticed, on my monitor at least, for the bhp calculation that the "3" for the cubed is hanging out in space. The (Desired Max speed) is only thing cubed in the calculation.

Randy

[crafty]

http://www.youtube.com/watch?v=hnpEG8dGkQY

[LuckyP]

crafty said:

http://www.youtube.com/watch?v=hnpEG8dGkQY

Ok. That was quick. Width of road makes it somewhat interesting!!

What happened to the brakes in the last 3 secs??

[Builder]

LuckyP said:

Ok. That was quick. Width of road makes it somewhat interesting!!

What happened to the brakes in the last 3 secs??

The road was narrow, crowned, and dusty. Yes, it was very interesting. The brake bias was WAY off.