2016 VF SV6 Twin Turbo

[SuckSqueezeBangBlow]

Turbos love load to spool which equals more torque anyway, so high diff ratio isn't needed.
Barra turbos have 2.73:1 ratio

 

[harrop.senator]

Depends on box ratio and how much it loves to rev. The manual falcons run 3.23 and 3.45 , skylines and silvias run 3.9-4.3 pending model and almost anything else jap is around 4:1 heaps of guys put shorter ratio diffs in falcons and never heard anyone complain. I swapped my 3.23s for 3.45 and wished they were 3.7's.

Yes the taller gears help spool but its not that larger difference at where it will spool and shorter gears are always heavily amplified by the butt dyno. Turbo or na it'll still make its peak power up top and being able to hop scream to scream will always feel more impressive. Sometimes will help with track numbers to pending spin and change speeds.

Some cars are faster with longer rear end ratios but they never feel as impressive in my opinion. I always like to aim for 60-70 out of 1st and 90-100 out of second ive found in street cars thats a great set up.

 

[SuckSqueezeBangBlow]

Depends on box ratio and how much it loves to rev. The manual falcons run 3.23 and 3.45 , skylines and silvias run 3.9-4.3 pending model and almost anything else jap is around 4:1 heaps of guys put shorter ratio diffs in falcons and never heard anyone complain. I swapped my 3.23s for 3.45 and wished they were 3.7's.

Yes the taller gears help spool but its not that larger difference at where it will spool and shorter gears are always heavily amplified by the butt dyno. Turbo or na it'll still make its peak power up top and being able to hop scream to scream will always feel more impressive. Sometimes will help with track numbers to pending spin and change speeds.

Some cars are faster with longer rear end ratios but they never feel as impressive in my opinion. I always like to aim for 60-70 out of 1st and 90-100 out of second ive found in street cars thats a great set up.

You are right about the speed in 1st & 2nd gears.

I guess I have had both ends of the scale, 2.73 in the falcon but I had 4.33 in the turbo ke20 (which was quick in 3rd and 4th gear but let down severely by too short 1st & even 2nd to a degree) so I always preferred the taller gears of the coon.



By chance they both had very similar power/weight ratio.
280rwkw/1715kg for the xr6t
130rwkw/860kg for the ke20

 

[monstar]

Nailing ideal gearing power to weight yet not altering weight, and having some mechanical sympathy for realistic engine rpm bandwidth... not hopping from scream to scream... leaves the primary factor being level (and shape) of torque that determines best rear gears.
In an auto V8 VE/VF 2.92 works ideal without going over 6k rpm:
1st 64 kph
2nd 109 kph
3rd 167 kph
4th 222 kph
The caveat is you genuinely need around 675 Nm to pull that off in a competitive time (my 1961 EK would also wind to 167 kph in third). So 90% of us don't bother building torque because it's much easier and impressive to push HP out screaming rpm past 6k.

 

[MYVESSV8]

I'd rather have torque available down real low

 

[harrop.senator]

Not driven a ve v8 do they really only pull to 6? Thought with all the new tech itd atleast pull 6.5-6.8?

 

[SuckSqueezeBangBlow]

the 6.2 LS3 in the commode redlines at 6000 with cut at 6600.

 

[monstar]

Not driven a ve v8 do they really only pull to 6? Thought with all the new tech itd atleast pull 6.5-6.8?

the 6.2 LS3 in the commode redlines at 6000 with cut at 6600.

Yeah once engine's VE is sorted / no choke, going on piston speed a 6.0/6.2 really stresses at 6625. Calculating maximum RPM based on the point of fastest piston acceleration taking rod length into account, 6820. Redline typically 10% below the proven risk of failure threshold.

Although lots of guys ditch engine protection via a tune, whereas I keep most stock stuff active and chose to line hone, TPP bores, forged conrods and pistons, custom ring set, and Spintron test the valve train harmonics for a safer raised 6400 redline. Shifts always below 6k unless TUTD mode.

 

[SuckSqueezeBangBlow]

TUTD?

 

[harrop.senator]

Are the modern pistons still just everyday casties with a 3500 fpm barrier or are they atleast a high silicone count hypereutectic and can handle some higher short bursts? Ive heard all the factory new ls rods are a forged type and assumed they'd upgraded how they made the pistons as well and would be able to handle a few more feet per minute then the slugs of old. I remember the original cast slugs in a 350 were doable to 6k safely but not much more before skirt damage and the ls2 strokes not much longer.

Anyway i should probably stop asking ls questions on a tt v6 thread old mate probably wants to choke me out haha.