456 vs 550. Could someone explain

Immense difference? I wouldn't call it that way but my bet would be the variable length intake (which is also where most of the performance gains come from), in combination with different aerodynamics. And of course that the 456 was designed less hardcore to begin with.

 

immense difference ?? the 456 perform 1km in 23.3 s, the 550 in 22.6..tha'ts less than one seconde for one kilometer..
the main difference is in the "reprise" due to more power in 550 and the 456 is a GT..4 seats..

 

I wouldn't call 20km/hr huge. That is like 12 MPH or about 5% of top speed. Am I missing something?

Yes, ignored the fact that you can't really drive it that fast anywhere.

 

The 0 to 60 difference is due to the gearing: in the 456 there is a shift needed, while the 550 gets to 60 in 1st and then needs a shift.
In real life the differences are smaller than the numbers may suggest.

 

What about which car could be put on a diet more? I think the prodrive guys got the 550 without going to a tube frame to something like 2500-2700lbs range? How are the car's suspension designs different? That difference could make for serious speed in corners. The 456 was designed for 4 people and cruising. What does that mean? There have been a couple of 456 racecar attempts but not like prodrive. At the low prices we are seeing 456's around the price of a 348/355 gutting a 456 out and making a racecar is very appealing.

 

Since the force to push something through air is a function: speed*speed*drag.

This means that if a 456 = 302 kph and the 550 = 320kph the extra force needed with the same drag would be:

320*320*drag/(302*302*drag)= 1,122 which is about 12% more power, this would give the 550 = 1,122*442=496hp

but since the maranello only has 485hp the it only needs 485/442= 1,0973 more power to achive the actual 320kph

since the force needed to reach 320kph for the 550 was 12%(using the same drag) but it only has 9,7% the drag has to be less that than the 456, would need to be 1,122/1,0973 = 1,022 which is 2,2% less than the 456 this would give the 550 the full speed of 320kph.
Yes I know you also need to add other friction factors like tyre resistance but at these speeds it is neglitable.

One must not forget that the drag is equal the Cd (drag coefficient)* the frontal area. I would assume by looking at the two cars that the 550 has less frontal area which is what give it the extra speed, the 456 looks alot more slippery.

This is really simple and quite funny formula to use when tuning a car for improved top speed.

 

these two cars were designed for completely different purposes. the engines are not alike despite having similar hp and 12 cylinders. the gearing is different too. so is the suspension, the wheels/tires, the spoilers, etc etc.

 

Just to play devil's advocate: a German magazine tested top speeds and measured the 550 at 307 km/h. I have no idea what the 456's top speed would be but I guess it would also be lower than claimed.

BTW - the formulae quoted above are not valid as fluid mechanics do not work on linear equations in turbulent conditions. You can't work with percentages.

All in all, do we really care? Both cars are phenomenally fast for their time and certainly my 550 has always satisfied any craving for speed I've had. It's a phenomenal engine (whether 456 or 550) - just enjoy the heck out of it!


Onno

P.S. I do have to disagree with Ross that the engines are not alike - the 550's engine is the same engine as the 456 except for the application of titanium con rods, hydraulically adjusted tappets, redesigned combustion and exhaust systems.

 

well, it is accurate enough I said it was an approximation..

 

Then it's not the same engine. Don't forget the 550's engine produces it's power at higher revs as well. (Hence the Ti rods).

 

From a quick search, I have the Cd of the 456 as 0.345 and the Cd for the 550 as 0.33. Anyone have better numbers?

 

Hello everyone

I have in my posession a book called

Ferrari 456, 456GT/GTA-456M GT/GTA

by Ippolito Alffieri, Paolo Murani, Stefano Pasini and Eugenio Zigliotto. Copyright by www.carbooksautomobilia.it in 2002.
This is a beutiful 112 pages book with the complet Ferrari 456GT story.

On page 72 in this book there is an extract from the original Ferrari test documentation relative to high speed trials of the 456GT on the Nardo ring in Italy on 09-02-1992.

This documentation states that the 456GT F116 P39 test car made a topspeed of 316.16 Km/h at 6.665 rpm on the 1 run. And 308.68 Km/h at 6.490 rpm on 2. run. This is a media of 312.4225 Km/h.
It also states that the "Velocita teorica" at rpm 6.578 is 309.7 Km/h.
The "fun" part is that 456GT F116 P39 test car "only" had 426 CV/HP at 6.510 rpm on tap. Not 442 CV/HP as the production 456GT ended up with.

This was faster than the Ferrari "flagship" at the time the 512 TR. And it is rumored that it was Ferrari politics that stated that the 456Gt topspeed was declared as "over 300Km/h" not to upset the Ferrari 2 seater crowd

 

having vmaxed both the 512tr and the 456mgt a couple times, i can tell you i would MUCH rather be sitting in the tr than the 456 at that point. i would also prefer to be sitting in the 512tr if the road gets twisty, or if i need to brake hard. the numbers may tell one story, but the seat of my pants likes the 512tr in nearly every situation better - except maybe parking and being subtle.

 

i think that the engine volume is different, the firing order is different, and bhp is different and comes in at different rpm.....so if the only physical difference you note is the titanium rods, well then they make a huge change !

where is tazanjan when you need him !

 

I think someone here stated earlier that at around 250 km/h, the hood open warning light comes on, a real disincentive to keep the pedal to the metal.

 

see post #20.
yes i have. the hood doesnt do that unless the adjustment is off.
the scariest thing about the 456 at vmax is the brakes. the 512tr at close to 200mph still feels planted like a vault - altho wind noise is high. the 456 feels a bit more skittish, and when you do want to slow down, the brakes dont inspire a lot confidence - better have a long road ahead of you.