Alfa Romeo Forum banner

Why is the 156gta quicker than the 147gta?

3K views 37 replies 14 participants last post by  Alexandrus 
#1 ·
Even tho they share the same engine and the 147 is lighter?
 
#4 ·
Looks like the difference in weight is about 50kg in the 147GTA's favour.
However that weight is probably with the 147GTA's std cloth interior, the weight difference would be less once it gets the optional leather seats. No lighter cloth option for the 156GTA.

So well under 50kg difference.

And the 156GTA is probably more aerodynamic at higher speeds.

But both are probably limited to 155mph anyway, so it makes no difference.


The GT 3.2V6 comes up as the same weight as a 156GTA
 
G
#5 ·
156 is a lot more aerodynamic at high speeds. The roof profile of the 147 is as tall as a treee, and the steep decline at the hatchback creates a lot of turbulence.

Always wondered about the GT though..it looks even more slippery. If you got the "missing" 10 bhp back in there, it might be the quickest of the lot?
 
G
#28 ·
The roof profile of the 147 is as tall as a treee,.....
Steady on mate! Its not that BAD!:lol:

Seriously though drag is no just the upper body shell, the underside has alot to do with aerodynamics too. The 147 actually is far better than the 156 in this department due to the careful positioning of the rear suspension ancillaries which good explain why the 147 is a little more stable at higher speeds than the 156. I guess though that 147's excellent underside is not to enough to make it beat the 156 at the top end.
 
#7 ·
147 is defintely quicker to 60 in any test I have seen.

..but I have seen several German tests of 0-100 for the GTA with a time of 14s, exactly the same as the 147 GTA (98 octane petrol), so I guess the saloon gradually catches up.
Autocar did only get 15s for the 156, but with using some environmentally friendly fuel (bah phooey!).

After 100mph in my totally non biased opinion (of course) I would expect the saloon to slowly waltz away from the less sleek hatchback since wind resistance is hugely important above 100mph

The speedo only going up to 180mph in the 147 GTA - didn't know that! That would be inconvenient.

TB
 
G
#8 ·
If we're talking about top speed, no, they are not limited to 250km/h. Only the 156 GTA reaches 250km/h due to it's better aerodynamic shape. It is well know that sedans are generaly more aerodynamic than hatches.
As for the GT, it has a pretty Cx or something, otherwise it's hard to explain the lower performance figures, and I mean both acceleration and top speed.
But regarding top speed, who cares ? The 147 GTA reaches 246km/h, the 156 GTA reaches 250km/h, it's only 4km/h, and that is in theory.

PS. The speedo is the same for the european versions, 300km/h. Pretty high for a car that won't even reach 270km/h, but it's nice anyway.
 
#11 ·
since we are talking speeds, you guys with oem 156 gta cars, have you tried to reach the limit? if so is it only my car that simply stops @ 210km/h and then it takes like 5weeks untill you reach the rest, if even that...

the car blows away to 210km/h without any problems but after that its dead, i dont even have a memory of reaching speeds higher than that with my GTA, while my old 2,5 v6 i went to 235kmh according to the meter, without problems.
 
#14 ·
Doesn't sound right to me, sure things slow down a lot in 6th for a standard car, but you should still be motoring reasonably well throughout 5th gear, obviously slower than 4th though.
At that speed though any inclines or wind can slow things down a suprising amount.

You don't really feel a strong push in the back like you do for 4th though, just more like steady indicated speed progress - every mph more consumes a lot more energy than at lower speeds due to the wind resistance.

Am sure some of our derestricted autobahn specialists can give their opinion.

Just a thought, maybe try high octane next time you plan such an assault on a derestricted area.

Cheers,
TB
 
G
#24 ·
Strangely enough guys i found my GTA to be reaching high speeds very quickly indeed. No joking last Sunday i pressed the accelerator about half way with 6th gear and the 230km/h came staggeringly quick i was left with the feeling that if i would keep my foot down i would see at least 270. The car should be capable of more than 250km/h if you would consider that my old vauxhall Omega 2.5v6 used to do flat out 245km/h with 38 degrees ambient.
 
#17 ·
It's aerodynamics, as has been stated. I think I'm right in saying that the 156SW is actually the GTA that is most slippery through the air, bizarrely!

I've never maxed mine, since I tend to do such things abroad and the French have caught our sense of humour failure about speeding (not been to Germany in the GTA), but I can report that mine pulls very strongly at 130mph and more, even in 6th. Suprisingly, and rather pleasingly, strongly.... I have been quite a bit quicker than that once but was not paying that much attention to the speedo, more to the scooby that I was cruising steadily up behind, then past - he was at his vmax, I would guess...
 
#18 ·
i think mine as some kind of fault on 5th cause it really just stops @ 210kmh nothing happens on 5th gear havent tried 6th that much but if i remember right its the same. might be something wrong with it :( il take her out now for a test, so i wont think about it all night.
 
#22 ·
hmm strange, i checked the airfilter+maf just to see if its really connected, since its a cdabox, i noticed that the maf and cda box are connected but im not sure if air might get it since i dremeld the cda box to fit and well i could have done the hole a little smaller, might be air getting in on the sides. Anyway i just filled her up with some more oil and checked battery water levels since i filled the cells a few days ago.

took her for a spin and well she runs great but after 4th gear she goes slower, its noticable. but i got her passed 210, went to 250kmh. didnt go as slow as before but still. So the question remains, can people in her tell me from 4th to 5th gear and now im talking speeds, does it really move in the same tempo towards higherspeeds? cause sure the rpm indicator goes on as normal but the speed isnt pushing on like 1-2-3-4 after 5 its not the same powerfeel right? or shall i just trash my car :D

something extra :p
http://bunmaster.mine.nu/GTA.wmv
 
#25 ·
I just want to make a comment on some of these observations regarding the velocity rate dropping off, coefficent of drag (CD) etc.

1.Yes the sedan has a better CD than hatch and the wagon better again. Despite the marketing angle that is why they ran Volvo SW in the BTCC in the 90's.

2. As was mentioned earlier wind resistance plays a part and these tests done by manufacturers are conducted taking into account wind direction (tail or head or side) and have an effect so unless your conditions were perfect, you had tyres as original spec (overall height is exact to original -and not wider otherwise increased drag) and tyre pressures are up then trying to replicate specified speeds by the car maker is near impossible on public roads (need to be flat and 0 gradient).

3. The problem with top speeds is not just CD as above a certain speed it is the inability for air to move fast enough out of the way. Thus you get a "wall" effect. To clarify, an F1 car has the CD of a brick...really. That's because it has downforce as a major requirement so it can turn corners as fast as a GTA goes in a straight line. The bulk of the 800+ bhp is used to push the car against the air "wall" that naturally builds up infornt of the car.

So in some of the responses you get a variation of the impressions of individual drivers due to varying conditions/circumstances...but don't worry about top speed...enjoy the GTA acceleration.
 
G
#27 ·
All I can say is I love my car. I always wanted an alfa V6 and am so glad I got the GTA, sure it was a big waste of money really but I don't care.

Never measured it but it hits 100mph very quickly, and I have inadvertantly had 130mph out of the car, it just doesn't feel it is going that quick.

I also love that it can be a real lazy car if you want, with no need to change down to overtake. And on a run 30+ mpg, really is my dream car.

Ahhh if only I got to drive it more.
 
#29 ·
What you should remember though is the 3.2 GTV has a higher top speed than both of the GTAs - despite having less power ;)
 
#31 ·
Ahh we could strap on an optional go-faster spoiler/diffuser to the back of a GTA to gain a few mph too :p

As I remember they introduced the GTV style spoiler origonally as an option for the 3.0V6 GTV in an atttempt to claim 150mph capabilities to keep up with Ze Germans a few years ago with the spoiler adding 5kph or something.
So by the same logic Without the spoiler the GTV will lose a few mph from its top speed and the fact it is heavier and less powerful than the GTA wouldn't help its cause then.

These were an option on previous GTV's but it could be that they came with the 3.2V6's as standard and were just as a delete option.
I don't really see many of these around as opposed to the more classically styled non-facelifted GTVs but have seen one facelift model with no rear spoiler.
 
#33 ·
Google wasn't iluminating in this regard :rolleyes:

nybody know what the Cd for both the pre-facelift and the facelift GTV's are?
I suspect the facelift one will be quoted with the spoiler, and the pre-faclift one without.

Cheers,
TB
 
G
#34 ·
I ment the GTV has a lower Cx than the 156 GTA, 0.28 compared to 0.31 if I remember correctly.

As for the above statement alfa_147_jtd_16v, what can I say, you've just contradicted every aerodynamic law there is. A hatschback cannot be more stable at higher speeds than a sallon due to it's shape, the same shape that is keeping the hatchback from reaching higher speeds than a saloon. The most aerodynamic shape for a car is a round big nose and an elongated lower tail.
 
G
#37 ·
Actually, a hatchback is more stable as the turbulance at the rear pushes the rear of the car down, hence why spoilers are fitted.
Even the team boss for Seat UK said this on the BTCC the other week about their Leon. Hatchbacks=more stable at higher speeds, but slower in a straight line. Remember the more slippery a shape is the less stable it is.
 
#35 ·
Normally sticking a spoiler on increses cd, but also downforce...hence the reason the Veryon's top speed is done with the spoiler down.
 
#36 ·
It depends on the type and purpose of the spoiler, which relates to the topography of the area it is trying to shape the air over.
The GTV's spoiler design is to smooth the air over its stubby rear which it obviously is pretty good at, or the top speed would be reduced.
The Alfa blurb at the time the spoiler design first came out (for the non-facelifted model) stated the claimed top speed could only be achieved with the optional aerodynamic aid of the spoiler.

The Veyron obviously needs downforce as a priority, it has power to spare plus it would be well airborne at 230mph if it wasn't stuck to the ground - remember those impressive loop the loops at Le Mans a few years ago!

As an aside I don't normally like spoilers, but the GTVs one is very tasteful indeed.

Cheers,
TB
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top