wstar's Journal

wstar · 03-16-2014, 12:59 PM

Here's those even-lower drives vs 4.083:

In that 4.636, the 4->5 upshift would be at ~87mph, 5->6 at ~122mph, and 6->7 at ~142mph

wstar · 03-16-2014, 07:58 PM

I've now found mention of a 4.90 that came in the 2004 Xterra, which might also fit in our diff

New graph of just those lowest-two found so far (4.636 + 4.900), with 7th gear added since max speed limit is (finally) becoming an issue at these ratios. I have feeling there are probably other tradeoffs I'm ignoring if I push this too far, also (like time lost to the 7AT's relatively-fast shifts if I'm shifting much more often), and that aside my max speeds in 7th with those gears are ~160 and ~150. I'm not hitting 150 anywhere yet, but I probably could eventually (esp, again, with the gear change itself helping out).

VoBoy · 03-17-2014, 10:23 AM

^- you know at some point you're gonna be spinning the tires because you got so much torque with the low ratios! IMO I wouldn't want to go too low or else you're gonna have to have more throttle control... even worse in rain. maybe i'm just lazy and like to put the pedal down as soon as possible

wstar · 03-17-2014, 10:37 AM

Well, I was planning to re-work my throttle map for better control in the bottom half of the pedal anyways, but, yes

There are actually a whole lot of reasons not to go extreme on the final drive ratio. More-so than the traction issues I worry about the wear-rate fallout with the 7AT.

According to those who've run FI on their cars, 6 and 7 (and maybe 5, too) aren't as strong as 1-4 in terms of torque-handling and get burnt up when you put too much power through them. I have no idea if moving a larger percentage of my track-time to redlining in those gears will have a similar effect even though I'm NA, over time, and eventually kill those upper gears.

And again - more shifts = more time lost to shifting, and I can't always shift mid-corner if I'm on the edge of traction, so a strategy that requires more shifting may result in more delayed shifts waiting for the car to straighten up and be a net loss.

Still, it's tempting to just slap in that 4.90 and see what happens. It would be a fun experiment, but possibly a costly one if I have to go back and put a different gear in soon afterwards

VoBoy · 03-17-2014, 10:43 AM

^- that's what gran turismo is for! they need to get that gps overlay stuff in there asap so we can get the texas tracks in the game lol.

VoBoy · 03-17-2014, 10:47 AM

Got any thoughts on 3.5 gearing? I have a 3.5 vlsd pumpkin taking up space... I could sell it to you for pretty cheap.

wstar · 03-17-2014, 10:52 AM

Quote:

Originally Posted by VoBoy

Got any thoughts on 3.5 gearing? I have a 3.5 vlsd pumpkin taking up space... I could sell it to you for pretty cheap.

I think I have to pick up a used pumpkin no matter what I do, either off someone or off a junkyard. I need to look into that more, but it seems like there's some minor difference in the interior shape of my 7AT pumpkin vs the standard 6MT pumpkin on 350's and 370's, which is why a lot of the LSD mfgs only make it for the 6MT? It could also just be that it's a problem with gear circumference on the gear I'd be swapping out anyways, I don't even know yet.

wstar · 03-17-2014, 10:50 AM

Another thing is a lot of my analysis with regard to upper speed ranges is based on TWS because (a) it's my closest track now and (b) other than *maybe* the back straight of COTA (which I probably end up doing once a year tops), it has the fastest straights around here for my car. If TWS goes away, that probably has significant effect on what speeds I care about on a regular basis

VoBoy · 03-17-2014, 11:04 AM

My diff is from a 6MT, and there is the exterior flange that bolts up to the drive shaft that's different, but swappable.

Review 4.08 Ring & Pinion Swap, she's alive! - MyG37

Here's a compiled list for VLSD drop ins:
List of aftermarket LSD for VLSD cars - MY350Z.COM Forums

For the wavetrac, looks like you need an open stud and a different stud (which might work with one side of the vlsd stud)
nasaforums.com • View topic - Wazvetrac issues/discussion

wstar · 03-17-2014, 11:20 AM

Quote:

Originally Posted by VoBoy

My diff is from a 6MT, and there is the exterior flange that bolts up to the drive shaft that's different, but swappable.

Some of those things change between the G37/370/350. I'm pretty sure both 6MT and 7AT 370Z rear ends have the same input flange on the driveshaft side. And no matter what pumpkin I'm using, I need at least one axle-shaft if I'm switching from VLSD to aftermarket LSD (but not open to aftermarket LSD). But for some reason other than those issues, there's a difference between the 7AT and 6MT 370 rear ends (enough that LSD mfgs generally are 6MT-compatible only, or make a separate model for 7ATs). It's either that the much-higher ratio in the 7AT is actually a different diameter (in which case I don't care, that gear set is being tossed anyways), or it's that the inside of the pumpkin has an odd shape for some reason I can't fathom. In any case, though, it seems the common solution others have employed is to grab a used 6MT pumpkin and slap it into their 7AT car. I think the 350Z and G37 6MT pumpkins both work in that case. Anyways, I really don't know, something to research later in the week

wstar · 03-18-2014, 11:09 AM

My rain tires arrived! These are the discontinued Continental-brand "Wet Radial Race Tires" that Hoosier's selling for $100/tire in 265/645R18 (if you order these, be sure to note there's a Left and a Right, get two of each!):

Now the interminable wait for the wheels to mount them on. I can't wait to see how these feel in the rain.

wstar · 03-17-2014, 11:15 AM

So, to sum up the (perhaps obvious to some!) things I've confirmed from looking at gears lately:

Given the shape of all VQ horsepower graphs, the things that really matter in the end, once you've seen the data, is "How do the gear gaps relate to each other" and "what's my max speed in top gear". As long as the gear gaps get shorter as you go higher in the box, and you don't run out of top speed, you're winning by going to a lower rear end ratio in terms of area-under-the-curve on the HP-vs-Speed graph (subtleties about shift points/delays notwithstanding).

In both the 6MT case and the 7AT case (ignoring the useless 1st gear, anyways), the gaps do get smaller all the way up the gearbox. While both exhibit the same basic narrowing of the gap as you go higher, the 7AT has significantly wider gears at the bottom and narrower at the top, vs the relatively-stable profile of the 6MT's gears, meaning there's probably less advantage to extreme gearing in the 6MT (but it's still there).

The percentage change in gearing per upshift looks like this:

7AT: 35.1% -> 36.0% -> 30.9% -> 29.2% -> 13.8% -> 10.4%
6MT: 38.7% -> 30.1% -> 21.7% -> 21.3% -> 20.6%

Top speeds in top gear with various rear ends discussed above, assuming 275/35R18 and a 7500rpm redline:

7AT:
3.357 -> 220
3.692 -> 200
3.917 -> 188
4.083 -> 180
4.364 -> 169
4.636 -> 159
4.900 -> 150

6MT:
3.357 -> 214
3.692 -> 194
3.917 -> 183
4.083 -> 175
4.364 -> 164
4.636 -> 154
4.900 -> 146

Mike · 03-18-2014, 02:37 PM

I just bought 5 sets of the continental 285/645 slicks!

wstar · 03-18-2014, 02:43 PM

Nice!

Any idea how the 285/645 slicks compare to DOT tire sizes? I've heard that the slick sizes vary quite a bit from what one sometimes expects, sometimes wider? I'm *hoping* my 265/645 wets will fit well on 10's, but I wasn't sure enough to bet on the 285 slicks yet until I see how this looks.

DR_ · 03-18-2014, 02:48 PM

Those look wide for 265.

03-16-2014, 12:59 PM	#1 (permalink)
wstar A True Z Fanatic Join Date: Mar 2009 Location: Houston, TX Posts: 4,024 Drives: too slow Rep Power: 3596	Here's those even-lower drives vs 4.083: In that 4.636, the 4->5 upshift would be at ~87mph, 5->6 at ~122mph, and 6->7 at ~142mph __________________ 7AT Track Car! Journal thread / Car setup details Last edited by wstar; 03-16-2014 at 01:01 PM.

03-16-2014, 07:58 PM	#2 (permalink)
wstar A True Z Fanatic Join Date: Mar 2009 Location: Houston, TX Posts: 4,024 Drives: too slow Rep Power: 3596	I've now found mention of a 4.90 that came in the 2004 Xterra, which might also fit in our diff New graph of just those lowest-two found so far (4.636 + 4.900), with 7th gear added since max speed limit is (finally) becoming an issue at these ratios. I have feeling there are probably other tradeoffs I'm ignoring if I push this too far, also (like time lost to the 7AT's relatively-fast shifts if I'm shifting much more often), and that aside my max speeds in 7th with those gears are ~160 and ~150. I'm not hitting 150 anywhere yet, but I probably could eventually (esp, again, with the gear change itself helping out). __________________ 7AT Track Car! Journal thread / Car setup details

03-17-2014, 10:37 AM	#4 (permalink)
wstar A True Z Fanatic Join Date: Mar 2009 Location: Houston, TX Posts: 4,024 Drives: too slow Rep Power: 3596	Well, I was planning to re-work my throttle map for better control in the bottom half of the pedal anyways, but, yes There are actually a whole lot of reasons not to go extreme on the final drive ratio. More-so than the traction issues I worry about the wear-rate fallout with the 7AT. According to those who've run FI on their cars, 6 and 7 (and maybe 5, too) aren't as strong as 1-4 in terms of torque-handling and get burnt up when you put too much power through them. I have no idea if moving a larger percentage of my track-time to redlining in those gears will have a similar effect even though I'm NA, over time, and eventually kill those upper gears. And again - more shifts = more time lost to shifting, and I can't always shift mid-corner if I'm on the edge of traction, so a strategy that requires more shifting may result in more delayed shifts waiting for the car to straighten up and be a net loss. Still, it's tempting to just slap in that 4.90 and see what happens. It would be a fun experiment, but possibly a costly one if I have to go back and put a different gear in soon afterwards __________________ 7AT Track Car! Journal thread / Car setup details

03-17-2014, 10:50 AM	#8 (permalink)
wstar A True Z Fanatic Join Date: Mar 2009 Location: Houston, TX Posts: 4,024 Drives: too slow Rep Power: 3596	Another thing is a lot of my analysis with regard to upper speed ranges is based on TWS because (a) it's my closest track now and (b) other than maybe the back straight of COTA (which I probably end up doing once a year tops), it has the fastest straights around here for my car. If TWS goes away, that probably has significant effect on what speeds I care about on a regular basis __________________ 7AT Track Car! Journal thread / Car setup details

03-18-2014, 11:09 AM	#11 (permalink)
wstar A True Z Fanatic Join Date: Mar 2009 Location: Houston, TX Posts: 4,024 Drives: too slow Rep Power: 3596	My rain tires arrived! These are the discontinued Continental-brand "Wet Radial Race Tires" that Hoosier's selling for $100/tire in 265/645R18 (if you order these, be sure to note there's a Left and a Right, get two of each!): Now the interminable wait for the wheels to mount them on. I can't wait to see how these feel in the rain. Mike, Megan370z and carlitos_370z like this. __________________ 7AT Track Car! Journal thread / Car setup details Last edited by wstar; 03-18-2014 at 11:18 AM.

03-17-2014, 10:23 AM	#3 (permalink)
VoBoy Base Member Join Date: Mar 2009 Location: Chicago/Houston Posts: 37 Drives: 06 350z Rep Power: 18	^- you know at some point you're gonna be spinning the tires because you got so much torque with the low ratios! IMO I wouldn't want to go too low or else you're gonna have to have more throttle control... even worse in rain. maybe i'm just lazy and like to put the pedal down as soon as possible

03-17-2014, 10:43 AM	#5 (permalink)
VoBoy Base Member Join Date: Mar 2009 Location: Chicago/Houston Posts: 37 Drives: 06 350z Rep Power: 18	^- that's what gran turismo is for! they need to get that gps overlay stuff in there asap so we can get the texas tracks in the game lol.

03-17-2014, 10:47 AM	#6 (permalink)
VoBoy Base Member Join Date: Mar 2009 Location: Chicago/Houston Posts: 37 Drives: 06 350z Rep Power: 18	Got any thoughts on 3.5 gearing? I have a 3.5 vlsd pumpkin taking up space... I could sell it to you for pretty cheap.

03-17-2014, 11:04 AM	#9 (permalink)
VoBoy Base Member Join Date: Mar 2009 Location: Chicago/Houston Posts: 37 Drives: 06 350z Rep Power: 18	My diff is from a 6MT, and there is the exterior flange that bolts up to the drive shaft that's different, but swappable. Review 4.08 Ring & Pinion Swap, she's alive! - MyG37 Here's a compiled list for VLSD drop ins: List of aftermarket LSD for VLSD cars - MY350Z.COM Forums For the wavetrac, looks like you need an open stud and a different stud (which might work with one side of the vlsd stud) nasaforums.com • View topic - Wazvetrac issues/discussion

03-17-2014, 11:15 AM	#12 (permalink)
wstar A True Z Fanatic Join Date: Mar 2009 Location: Houston, TX Posts: 4,024 Drives: too slow Rep Power: 3596	So, to sum up the (perhaps obvious to some!) things I've confirmed from looking at gears lately: Given the shape of all VQ horsepower graphs, the things that really matter in the end, once you've seen the data, is "How do the gear gaps relate to each other" and "what's my max speed in top gear". As long as the gear gaps get shorter as you go higher in the box, and you don't run out of top speed, you're winning by going to a lower rear end ratio in terms of area-under-the-curve on the HP-vs-Speed graph (subtleties about shift points/delays notwithstanding). In both the 6MT case and the 7AT case (ignoring the useless 1st gear, anyways), the gaps do get smaller all the way up the gearbox. While both exhibit the same basic narrowing of the gap as you go higher, the 7AT has significantly wider gears at the bottom and narrower at the top, vs the relatively-stable profile of the 6MT's gears, meaning there's probably less advantage to extreme gearing in the 6MT (but it's still there). The percentage change in gearing per upshift looks like this: 7AT: 35.1% -> 36.0% -> 30.9% -> 29.2% -> 13.8% -> 10.4% 6MT: 38.7% -> 30.1% -> 21.7% -> 21.3% -> 20.6% Top speeds in top gear with various rear ends discussed above, assuming 275/35R18 and a 7500rpm redline: 7AT: 3.357 -> 220 3.692 -> 200 3.917 -> 188 4.083 -> 180 4.364 -> 169 4.636 -> 159 4.900 -> 150 6MT: 3.357 -> 214 3.692 -> 194 3.917 -> 183 4.083 -> 175 4.364 -> 164 4.636 -> 154 4.900 -> 146 __________________ 7AT Track Car! Journal thread / Car setup details Last edited by wstar; 03-17-2014 at 11:24 AM.

03-18-2014, 02:37 PM	#13 (permalink)
Mike The370Z.com Sponsor Join Date: Jun 2009 Location: Loganville, GA Posts: 5,944 Drives: 370z Rep Power: 2188	I just bought 5 sets of the continental 285/645 slicks! __________________ NISSAN: 75 280Z / 86 300ZX GLL /87 Sentra SE / 03 350Z / 23 Z Porsche: 93 968 / 23 Macan GTS / 93 968

03-18-2014, 02:43 PM	#14 (permalink)
wstar A True Z Fanatic Join Date: Mar 2009 Location: Houston, TX Posts: 4,024 Drives: too slow Rep Power: 3596	Nice! Any idea how the 285/645 slicks compare to DOT tire sizes? I've heard that the slick sizes vary quite a bit from what one sometimes expects, sometimes wider? I'm hoping my 265/645 wets will fit well on 10's, but I wasn't sure enough to bet on the 285 slicks yet until I see how this looks. __________________ 7AT Track Car! Journal thread / Car setup details

03-18-2014, 02:48 PM	#15 (permalink)
DR_ Track Member Join Date: Jul 2009 Location: Dallas Posts: 981 Drives: Touring/Sport M6 PG Rep Power: 18	Those look wide for 265.

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