onagao

I've been trying really hard to find some comparison - either visual or quantified - between stock gears and any FD gear modification.

Granted, there is one set of 1/4 mile time slips around here that shows a difference of almost 0.3 seconds. But that's really all I've found. Well, that and this video:
http://www.youtube.com/watch?v=e32gozeyXLo

Unfortunately, the video shows just about zero difference.

I'm the kind of guy that really cares about results, and the lack of any quantified results is somewhat bothering. I don't doubt that it's faster, and 4.08 gears are next on my list of mods, but this issue is giving me pause.

Can somebody please either provide me with some numbers or a video other than the one 13.0 1/4 mile run already on here?

Z1 Performance

iTrader: (564)

with all due respect, what good is a video going to do? I would venture to say that every car that has the gears installed has other mods as well - so as those mods change, so will the nature of the car in general, and thus the video. The car is quicker by virtue of the math change alone

here is my car with 3.9's - can't see it doing anyone any good unless they also have all the other stuff as well though

http://www.youtube.com/watch?v=QMnVkpxuurM

Lakeside

iTrader: (5)

You doubt? Alot depends on rim size and tires used for traction! Not to mention Diff

Its clearly going to be faster................. Your only looking for 1/4 mile times? Seriously...... Don't be a DB

You can read almost any car forum if your looking for 1/4 mile times and see the results! it doesn't just have to be a Z to prove one's point.

micmicmotorbike

iTrader: (13)

i was thinking the same thing.

i'm not trying to be a wise a**, but gearing involves no theoretical thinking. it's factual. your acceleration will be faster in each gear. i guess if u need #s performance wise, quarter mile times can show them, but even then, there are many variables. someone that's consistent, similar conditions, so on and so forth, before and after the gear install.
if u really need factual data, all you need is the gear ratio # differences.

Z ELIMINATOR

iTrader: (3)

Cats + intake + stillen exhaust + 4.08 gears = 12.8009 @ 110.33
7 AT on stock 19 inch tires.
Just missed going 12.7's.

Intake + stock set up car ran 13.2098 @ 102.9
Base line 265RWHP
intake 285.6 Rhwp
intake. cats. CBE + 292 rwhp ( bad day at the dyno) Hot and humid day
it chould have been around 305 to 310.

Thread is in drag section (12.8 @110.33)

onagao

Whoa, whoa, whoa.

I feel the need to hold my hands up and stop you guys for a second. I don't doubt the math of shorter FD gears. I KNOW they improve performance. Physics dictates that.

Okay. Read that again if you have to.

Lakeside, you completely misread my post.


Okay. So now that I've established what I'm NOT doing. Let me rephrase and retry. The video that the guy posted, that I reposted here, wasn't intended to be some sort of debunking BS - it was an example of what would be a great way to show before-after performance gains while minimizing the numerous variables. All I'm asking for is some quantified performance results. I know you can show how much shorter the gears are, and I've found ONE graph showing 3.5vs3.9 in terms of TQ versus SPEED (which seems really helpful, but it's difficult to understand how that translates into real world performance results).

Everyone says they're the best mod you can do for an NA car, and it makes sense. I'm just trying to make a polite request for some more information that quantifies what everyone is feeling. Can you guys help me out with that?

onagao

I guess if my post lacks anything potentially incendiary, I don't get a response? My first question got 4 responses within minutes. Now that I've revised my request for the sake of clarity, I get 0 responses in 5 days?

[Z1, that car is just mean, btw.]

Z1 Performance

iTrader: (564)

No one has answered because you answered your own question essentially - the math proves they work. You're asking someone to prove the difference in how something feels. I don't know how possible it is to "view" ~14% while watching a video of a car that doesn't even have sound? I'd submit that the video posted is essentially worthless but that's neither here nor there. Ask anyone that has them - a car with 4.08's feels remarkably different than a car with the stock final drive. This thread is full of testimonials that say the same thing. To have some prove it to you, you would need to just experience it for yourself. Perhaps the best thing for you to do is to simply post a request in your local forum, and see if someone who has the gears can take you for a ride.

The graph that you have, assuming it is accurate, will simply show you, in raw data, the difference between them based on rpm and speed. The rest will depend on rolling diameter of your tire, weight of the car, etc.

onagao

On the local bit. Yeah, I already did that on the state Z car club forums, but with no luck.

I mentioned the math and physics of it. I'm putting out 260 ft-lb wtq, and the math says that I'll be putting out almost 300 ft-lbs wtq if I switch to 4.083 gears (15% increase). That sounds amazing. I don't doubt it at all.

The question I'm asking isn't whether or not it would increase torque, or what the math says in terms of how much. Like I just mentioned, I know that aspect of it. What I mean to find out is how that performance would translate into real-world performance (as opposed to just WTQ numbers).

And if there are no before-after comparison videos or performance statistics, that's fine. I'm just asking in case there are so that I can take a look at them. I'm excited about the mod, and am seeking out as much info as I can on it. I can read all day about how everyone is going nuts over how something feels, but you're right. I'll really have to experience it for myself to truly appreciate it. That won't really stop me from trying in the meantime, though.

...

Maybe I'll just wait until my copy of Forza Motorsport 3 eventually gets in, make the modification there, and race it.

Z1 Performance

iTrader: (564)

You're overthinking this tremendously

It does not add torque - the only thing that adds torque is a change to your engine, and unless you change something internally there, no torque is being added. Gears are a torque multiplier. Think of it like a 10 speed bike. Try putting the bike on speed 10 and moving from a dead stop....it's difficult. Then try putting it in gear 1...it's easy. The transmission in your car is a perfect example as well. There is a reason why 1st gear has a far shorter ratio than 6th. Try acceleration from a dead stop in 6th - the car will stall. Try it in 1st, and it pulls away quickly. Same theory applies here. The 4.08 will accelerate quicker in every gear vs the 3.54. However, it will reduce top speed in every gear as well. Refer to page 1 for these numerical effects

I would post up in your regional forum on this site for the best results

Lakeside

iTrader: (5)

My install didn't go as smooth as planned... Stilll stuck on L.I. Hoping it will be done today so I can enjoy my 4 hr drive home in the rain...... Ughhh

Must have messed up a bearing or something and waiting for parts. My car only has 7kmi on it. I'll take it easy on the way home. Weather here is pretty ugly.

Edit: Performance Motorsports stated that the issues had to do with the Quaife Diff not having the correct clearences needed for install. So machining had to be done. I purchased the direct replacement for the VLSD which was not an easy swap out.

onagao

I hope you don't feel that I'm dragging this out, but I don't feel I'm overthinking it. The torque at the wheels is definitely increased. Horsepower at the wheel stays the same because the wheels are not rotating as quickly. I'm not suggesting an increase in engine torque.

I get the whole concept. I'm just trying to quantify the performance increase.

Z1 Performance

iTrader: (564)

like I said, go for a ride in a car that has it - short of that, all the info one could ever want is in this thread

Yes the torque at the drivewheels changes, relative to engine torque. The torque output of the engine itself remains the same. The change will vary from gear to gear

King350Z

iTrader: (1)

lol @ all the posts. I just can't wait to get my 4.08 gears. Z1 Performance rocks =) have never ever done business or anything but by reading, this guy sounds educated on this

Lakeside

iTrader: (5)

Made it home with the car late lastnight. Highway speeds alot more enjoyable. 5th and 6th gear now provide much improved passing acceleration.

I haven't really romped on it to hard yet. Allowing the diff to break in but pulling out of Tolls the car pulls very nicely. I honestly didn't notice any increased shifting in traffic.

Z1 Performance

iTrader: (564)

there is no break in on a Quaife - there is nothing to break in, it's just gears, no clutch disks

Z1 Performance

iTrader: (564)

output shafts on HR's (and some revups) are different from previous gen cars, so often, one output shaft has to be cut down, or swapped out. Not something that's unique to Quaife, it can be an issue with all the diffs...just depends what output shafts the car has stock (no way to tell in advance without removing them)

onagao

Disclaimer: I don't get very many opportunities in Law School to put my mechanical engineering degree to work, so forgive me if I get overzealous with the calculations and take it an extra mile.

I've been doing a lot of calculations and looking at the results comparing stock gearing to 4.08 gearing for my car. I've mapped out the actual Wheel Force (lbs) versus Vehicle Speed (mph), and it's making me wonder about some things.

[I've attached the graph]

For instance, between 34mph and 41mph, the stock gearing will provide substantially higher acceleration. Same goes for roughly 55mph to 67mph. It just alternates back and forth, and granted... it's not Speed versus Time or even Force/Acceleration v. Time. I can't really get into that without busting out differential equations, and those are just gross.

So unless the straight-line race starts out in 1st gear, where the geared car will obviously have the advantage, it seems that the average acceleration is roughly the same. This would explain a bit of what was in the video I posted earlier. My question, though, would be how much the early acceleration (the getting to a higher speed sooner) overcomes the detrimental effect of having to shift sooner while the other car would be accelerating faster - in practical application?

Again, I'm not doubting the reality of torque multiplication. But it seems that the only reasons to get the gears are:
- Optimal RPM at 1/4 mile finish
- Track racing
- More torque available in each gear than before
- A car that feels quicker

Again, that last one, the omission of the car being actually quicker after 1st gear is predicated on the fact that I don't have any real-world before-after comparison (aside from the video I already posted) to come to any conclusions about the effects of the gearing versus time.

Can someone help fill in my blanks here?

cturnbull802

- More torque available in each gear than before

/thread.

onagao

I mean, sure. I guess you can just copy and paste something I said and be dismissive... it's easier than actually applying critical thought to what I said. Thanks.