PeterSellers

iTrader: (1)

What I mean to say is that in a drag race, there is no advantage to having 4.08s vs the 3.5s when you remove 1st gear from the picture. From a roll, all other things being equal, they will have roughly the same acceleration.

Yes, the 4.08 car will have more "passing power" when you compare 5th gear vs 5th gear with the 3.5 car, but keep in mind that the 3.5 car can be in 4th for quite a while longer while the 4.08 car needs to shift to 5th much earlier. While the 3.5 is in 4th it will pull harder than the 4.08 car that had to shift to 5th (until the 3.5 car shifts to 5th, then the 4.08 car should be slightly faster. It's a back and forth kind of thing).

My last car (mazdaspeed 3) had CRAZY short gearing. 2nd gear effectively ended at 55mph. The car FELT way faster than my HR, but I got a chance to drag them both against each other (had a friend driving my old mazda) and the HR, even though it felt slower due to the longer gearing, was actually faster.

Gears are one of those things that really screw up your butt dyno. They feel a lot faster but in reality they aren't really, except in a few certain cases (like 1st gear).

Lakeside

iTrader: (5)

I haven't search or done any research on this but I should. There are many complaints on how wide the gear ratio's are on the 6MT.

http://youtu.be/XFAyCQlhPlk In this video he complains how wide the gear ratio's are on the Nismo 380RS

Curious how the car would be with:

http://www.osgiken.net/products/closeratiogear.html

PeterSellers

iTrader: (1)

Those short ratio gear kits would be interesting but it would totally depend on the ratios they chose for each gear. If it were up to me I would shorten gears 1-2 a little bit for faster off the line acceleration but would make 6th quite a bit longer for better gas mileage (how often do you really push it in 6th gear anyways?)

A re-geared transmission would be the best of both worlds: faster off the line acceleration without hurting your cruising rpm and gas mileage.

Ataru074

iTrader: (19)

actually... with more that 300hp at the crank 1st and 2nd gear SHOULD be way longer... for launch and acceleration.

the "ideal" top speed in each gear should be something like
60mph
85mph
110mph
125mph
143mph
165mph

you'll be ALWAYS in power zone with a limited drop of rpm.
the problem you have today in a 1/4 mile or road course is the excessive drop of rpm between 1st and 2nd gear and 2nd and 3rd.

same on a road course...

AadosX

iTrader: (10)

PeterSellers I think you're crazy or something.. your logic is flawed. If a car feels faster, it is faster, unles the person feeling has issues. Gears make the car faster in every way, and there are plenty of 1/4 mile times to back this up. Yes you will have to shift more, but if you don't have to shift an extra time before you get to the 1/4 mile marker, your times will be greatly reduced.

They don't only affect 1st gear, they affect every gear.. that's what a final drive does. It multiplies each gear in the transmission by it's ratio. Of course it is more noticable in 1st gear because the gearing there is already so short.

Simply put, the 4.08's are faster than 3.5's all the time, no matter what speed or what gear. Feel free to line up against a 4.08 car on the interstate with your 3.5 and tell me that it doens't walk you. This "back and forth thing" you're talking about wouldn't happen because the transmissions gear ratios aren't that far apart.

And the reason your MS3 felt faster is because it was turbo. The power comes on more quicly on turbo cars.

PeterSellers

iTrader: (1)

Aadosx, with all due respect, I'm going to have to disagree with pretty much your entire post.

First, I think you should read this thread (the good part starts at the end of page 30):
https://my350z.com/forum/engine-and-...talled-30.html

onagao made a very useful analysis of exactly how the gears change the drivability of the car in a straight line.

Please re-read what you just said. "If it FEELS faster, it is faster." Do you realize how ridiculous that sounds? Why do you think people bring up time and time again how inaccurate butt dynos are?


You are comparing single gears in isolation which is totally unrealistic. You have to compare the gears as a set, after all, no races that I know of only last 1 gear. 4.08's are NOT faster all the time no matter what speed. As soon as the 4.08 shifts into its higher gear, it will be slower because its torque multiplication is now LESS than the 3.5 gear since the 3.5 car is still at a lower gear (remember, at the same speed since the 3.5 gear is longer!) Do not forget the fact the 4.08 car has to shift earlier into a higher gear with LOWER torque multiplication.

1/4 mile times are irrelevant because like I said, gears definitely help in 1st gear, therefore they would help in the 1/4. But from a roll it's a totally different story.

I would love to line up against a stock Z with only 4.08 gears to compare but I don't know of any around my area.

Sorry, but I owned that car for three years and I knew its powerband inside and out. I can guarantee you that the super short gearing played a huge role as to how the car felt.

PeterSellers

iTrader: (1)

With gears that long, say you start off in first, it's going to take you longer until you get into the Z's power band. I think you'd definitely be slower with a longer first gear assuming you can maintain traction in first with a shorter gear.

doshoru

iTrader: (3)

Guys, Peter is right.

When you're comparing cars with different FD ratios, the critical factor that often gets left out is that the shift points are different -- A 3.538 geared car can be in 2nd at 60mph where a 4.083 car is forced to be in 3rd.

Let's compare a race at 60mph between Car A (stock geared HR Z) and Car B (4.083-geared HR Z):

- Car A starts in 2nd gear
- Car B is forced to start in 3rd gear, b/c his 2nd gear tops out at 60mph.

Which car is going to accelerate faster from 60-70mph? The stock-geared car! Why? Because when you multiply the gear that each car is in by his final drive ratio, the stock car's net torque multiplier is higher: (2nd * 3.538) > (3rd * 4.083)

Now...Let's say the race is from 70-80mph:

- Car A starts in 3rd gear
- Car B starts in 3rd gear

Geared car wins, since they are both in 3rd gear: (3rd * 4.083) > (3rd * 3.538)


You can continue this example indefinitely on your own, but I'll sum it up for you:
1) 4.083 is always faster than 3.538 if BOTH cars start in the SAME gear (edit: for the duration of that gear)
2) Since neither car can go lower than first gear, the 4.083 car always has the advantage if the race starts in 1st.
3) If the race starts above 1st gear, the outcome depends entirely on the speed that the race starts AND ends at.
4) If the race starts above 1st gear and continues to infinity, the lead will change several times, but the average rate of acceleration will be the same.

doshoru

iTrader: (3)

If you're reading Peters' and my posts and getting discouraged about gears, DON'T BE.

Gears are still an incredible mod for fun and daily driving, which is what I am personally more concerned about. The car will certainly "feel" different. What gears will do for you is give you more acceleration without having to downshift (or downshift less gears).

Here's some real world daily driving scenarios where I would LOVE to have gears:

I'm putting along at 25-30mph and want to pass some shmuck, post-haste. At that speed, I could double-clutch rev-match down into 1st, but let's be honest -- that's kind of extreme. More than likely I'll just throw it into 2nd, well out of the powerband.

If I had gears....I'd be much further into the powerband downshifting to 2nd.

Same thing goes for passing cars at highway speeds -- downshifting to 2nd at 55-60mph is pretty extreme and abusive.

I guess my point is that the Z's gears are a bit too long for daily driving.

Z1 Performance

iTrader: (564)

the problem with your logic is that you're assuming every race takes place in a straight line, running through every gear, and that the redline of each car is the same

the fact of the matter is this - it's situational. There will be situations where a 3.5 may have the edge, and times where the shorter rations (3.7-4.3) will be more advantegeous. Taking weight out of the equation for a second:

RPM Limiter point
tire diameter/wheel
engine work
effective rpm range of engine/engine work
track type/layout or street type (winding, mount roads, vs straight highway)

all of the above determine whether gears are a worthwhile or not worthwhile mod for someone. Anything that does not take the above into consideration is anecdotal

angelo350z

iTrader: (3)

Great info on FDs, but not really relevant as they don't improve hp. I only have intakes, HFCs, and exhaust on my HR; no tune and no headers yet. 300 whp is definitely a lofty goal, but worth it IMO. Tomei cams seems to be the popular choice so I'll look into that.

PeterSellers

iTrader: (1)

doshoru, I agree 100%. You said it better than I ever could.

PeterSellers

iTrader: (1)

There isn't a problem with my logic. I am just tired of hearing people say how gears make your car accelerate faster at all speeds in any gear. This is simply untrue, and I figured I would try to clear things up for some people who might be interested in getting them. I never once said that gears are totally worthless.

Ataru074

iTrader: (19)

the biggest flaw in that logic is that the Z has the potential to fully use all the gearing.
for how it is stock a 350z (NA of course) barely use 4 gear and 1/2 considering that is unable to push 5th gear to the rev limiter (I'm talking about an HR engine)... at the point that even with more power and pretty much the same gearing the 370 has a shorter FD.

stock gears in 2010 economics are designed for fuel economy.

with a 4.08 you are able to use 5 and 1/2 gears (you'll never get at the rev limiter in 6th) and that makes obviously a better choice because when you need the power (higher speed, more aero drag and tire drag) you are able to spend more time in powerband...

de facto having 5 and 1/2 gear available instead of 4 and 1/2 gives quite some advantage, in a straight line and on a road course, just because you'll have more chances to be in powerband.

AadosX

iTrader: (10)

Maybe we will just have to agree to disagree. I would love to find a video of two 350Z's racing, one bone stock, and one with only 4.08 gears, on the highway. I can absolutely guarantee that at all points in the pull the 4.08 car would be pulling away from the stock Z.

There is more going on than just the gear ratio x the final drive.

The reason I said if it feels faster it is faster, is because it's true. Why are butt dynos inaccurate? Well I don't think they really are, other than the fact that sometimes people let their head do the dyno and not their butt.. for example when they spend $500 on a mod that might give them 5 hp, they are letting their head do the work and trying to subconsiously justify the money spent. Get in a turbo Z compared to a stock Z. The turbo Z feels faster. The turbo Z IS faster. Get what I'm saying? But that only works for people who have been in the scene for a long time and have a lot of driving experience, and can tell the difference between some boost suddenly coming on and how fast a car really is. That's really the only place it gets difficult in my opinion.. but anyways. How accurate the butt dyno is all has to do with how well calibrated and seasoned it is.

By the way, if anything, 4.08's HURT Z's in the 1/4 mile when it comes to 1st gear alone. But they make up for it in 2nd, 3rd, and 4th by giving the car much quicker acceleration. If you could just change only the subsequent gears, that would be much more worth while. On street tires my car has enough trouble not spinning all the way through 1st as it is. With 4.08's, if you floor your car at almost any point in 1st you will probably break traction.. that's not so good for a drag race. First gear is in no way the only place 4.08's help Z's, in fact I think it's the complete opposite and that's the only place they HURT Z's.

AadosX

iTrader: (10)

.. and here you go.

"Video comparison with two different s2000's. Same mods, except one has 4.57 gearing while the other has the stock 4.10"

<iframe width="480" height="390" src="http://www.youtube.com/embed/89rGbTbFfKs?rel=0" frameborder="0" allowfullscreen></iframe>

PeterSellers

iTrader: (1)

I take it you haven't looked through that thread I posted earlier?

Ok, well here's a chart from that thread which shows the theoretical torque at the wheels of a stock geared Z versus a 4.08 geared Z. From a dead stop to about 34 mph, the geared car puts out more torque (no surprise there, 1st gear should be that way). However, at 36 mph the geared car has to shift. From 34-42 mph, the stock geared car is putting out more torque (significantly more at that), until it has to shift. Same from 54-66 mph, the stock car is putting out more torque and will be accelerating faster. If you have a roll race start between those speeds, the stock geared car will pull ahead first.

Now after looking at that chart, do you understand why there's a back and forth and why it doesn't make sense to say that a geared car is faster at ANY speed?

And the reason that people relying on butt dynos are laughed at is because its a totally unscientific way to determine power. I don't really feel the need to argue that point any further.

PeterSellers

iTrader: (1)

Yeah, they raced from a dead stop, no surprise there...

http://www.youtube.com/watch?v=EW0xb...eature=related

Here's another bad video of a stock geared s2k beating a geared one from a roll (the only way I could tell what actually happened was to read the comments though)

AadosX

iTrader: (10)

This is getting beat to death lol.

So at what point in my video was the lower geared car pulling harder than the higher geared car?

Yes, you're right, at certain speeds for a few RPM's, a lower geared car will have more TQ.. but not enough to make up for the higher geared car's huge advantage everywhere else. Compare the area in between the curves in your graph..

So I shouldn't have said (if I did) "A higher geared car will always be faster at a given speed." I should have said "A higher geared car will always be faster at a given time in a race" which is shown in the video I linked, and is because the higher geared car will be at a higher speed at a given time in the race, and even if the lower geared car hasn't shifted yet and is "theoretically" accelerating at a faster rate, relative to it's own speed, the differential between the two cars' relative speeds is too great for the added acceleraton to make up for. The only time that a lowere geared car could possibly pull on the higher geared one is if they happened to start a point where the lowere geared car was at the top 500 RPM's before he had to shift.

PeterSellers

iTrader: (1)

And at what point in my video was the geared car pulling on the stock geared car? But an even better question is, why should one street video on youtube (with a ton of other variables involved) be the only proof you need? youtube racing is pretty pointless because of that.


No offense, but you pulled the 500 RPM number out of your ***. I'm glad you mentioned area under the curve though, because the total area under the curve for both sets is EXACTLY the same. Gears do not provide any power increase, they just move it around a bit. It would be physically impossible for gears alone to do that.

I can see that I won't be able to convince you so I'm just going to stop now. Hopefully this information is helpful to others who were on the fence like I was but needed more information (I will say that I have no doubt that gears will make the car more fun to drive. But it's up to each person to decide whether the trade-offs are worth it for them).