I am very pleased with the VG30DETT setup, it does make great power and is incredibly flexible. However, after living with the car for well over a year I feel it could use some improvements, most notably in off-boost, low RPM situations. For the most part it's not a big enough deal to worry about dumping much effort into improvements on the VG - just about everything would increase power at the expense of lag and no increase in off-boost torque. However, in 2002 Nissan came out with the VQ35DE - all aluminum, 3.5L V-6 with 240HP in the Maxima. In 2003 they released the new 350Z with a RWD version of the VQ35DE and it was rated at 287HP and it came with a 6-speed transmission. The VQ35DE is about 70lbs lighter than the VG30DE, and the 16% increase in displacement + more modern design comes out to a very realistic increase in torque of about 20% vs a VG30DE.

When I initially lmentioned going VQ35DETT in my second-effort 510 (Redux) to several friends, they accepted the choice but also questioned why not just develop the VG30DETT further. This is a reasonable question given the following conditions of the current VG30DETT 510:

1) The current VG30 has enough torque to run 4th around town at 1000-1200RPM with no problems.
2) Full throttle is effectively worthless in the lower 2 gears, and 3rd too if it's below 60deg outside.
3) RPM @ 60MPH is about 2300 and could be a little lower and still provide adequate punch off-boost.

However, looking at the VQ35DE I feel reasonable and noticeable gains can be made since the rear suspension will be redesigned and able to handle wider tires.

VQ DRIVETRAIN GOALS:

1) Increase peak power by a reasonable amount [estimate 70-80RWHP]
2) Increase off-boost (i.e. cruise throttle setting) response and torque
3) Increase torque available below 2500RPM
4) Decrease highway cruise RPM by about 200RPM - goal is 2000RPM@60MPH
5) Decrease lag
6) Decrease overall weight
7) Improve F/R weight distribution
8) No significant loss in MPG (#4 should help here)

Tonight I finally sat down to see what the gear ratio effects will be - mainly because I knew already that 1st gear is 14% shorter than my Z32 5-speed.

Given the following:

The LAST thing Redux needs is shorter gearing, but the 6-speed out of the G35/350Z has exactly this, including 6th (.79) being shorter than 5th in the Z32 (.759). In fact 1st gear is 14% shorter! Add the 15% more off boost torque and that's 30% more torque to the ground when off boost.

The planned tire for Redux is 7% taller (245/45-16), which does actually two beautiful things: 1) Effectively increases gearing by 7%. 2) Adds a wider contact patch than my current 225's. This 7% is even enough that the RPM@60MPH is lower by a fraction (about 70RPM).

The net effect of the 245's is still 6% more torque to the ground via gearing, and with another 15% more torque due to displacement I would imagine the 60-70# lighter Redux should come close to feeling like a V-8 car when off boost - you'd notice 20% more torque I'd think :-).

Attached is the chart I came up with, and I even threw in data for 245/45-16's with a 3.15:1 axle ratio. While that sounds ridiculous, the 1st gear overall ratio comes out almost nuts on (0.14%) with what I have with Red currently....so I would STILL expect it to pull harder in 1st because the extra 15% displacement. This would also drop RPM@60MPH to 2100RPM, and by my math that's a 9% drop, so even this would be more than offset by the 15% torque increase of the VQ35DE when off boost.

As near as I can estimate 245/45-16's with an ever taller-than-now 3.15:1 axle would STILL get me more torque to the ground off-boost from a dead stop a well as at 60MPH than I have now. The only gotcha I see is if the VG30DETT makes more torque at 2300RPM than the VQ does at 2100RPM (unlikely). I might just have to hunt for the rare 3.15:1 R200.

It turns out that, in my opinion, anyone doing VQ35/6-speed who uses stock-ish 510 tire diameter and the ever-popular 3.7:1 Subaru LSD will be one shifting, poor MPG bastard comparatively. But they'd have about 40% more torque in 1st gear than I have now.

What the hell does all this mean, anyway?