Bloopdog

Hello, recently been doing some research on differentials and ratios, mainly the 4.77 kia sportage swap. I've found lots of info on it, but cant seem to find videos comparing the acceleration. Does anyone run a high ratio like this and mind getting some footage of acceleration and shifting for us? A lot easier to perceive rather than looking at charts.

Z_WAAAAAZ

I have nothing to contribute here, but am curious (and think this information should probably be listed). What’s the power level and intended use of the car?

rjacobs

I had a 6spd and 3.6 rear end in a basically stock powered NB2... That setup is supposed to be "similar overall gear ratio's" to a 5spd with a 4.30...

My buddy has a 5spd, 4.77 in an NA with a VVT motor, so "basically" same power level...

I held him up around a turn, never lifted and when we got around the turn I pointed him by and he went by me like I was standing still... Im sure I have Garmin video of it, but not sure I want to look for it.

The acceleration difference is DRAMATIC. I have a 6spd, 4.30 now, but I dont think it made the car any faster because I went from a 2, 3, 4 gear car with the 3.6 rear end to a 3, 4, 5 gear car...

5spd, 4.77 I think is a GREAT N/A setup... if you had more HP, I think its probably to low of a gear.

Z_WAAAAAZ

That's actually really cool to know there was such a notable difference in acceleration!

Not apples to apples, but I noticed roughly the same thing when I went from my 6 speed/4.30 to a 3.6 rear end. Couldn't tell any massive difference in speed, now I was just a gear lower in most parts of the track. This is on a higher powered car, though, and being measured by the butt dyno, so take it with a grain of salt haha.

Might be worth playing around with this and/or Padlock's tractive force calculator if you really want to get into it.

https://kpower.industries/pages/gear...2C1%2C0.843%5D

rjacobs

Im still trying to learn the car with the new gears.

Last year at Eagles Canyon with the 3.6 I was able to run 2:19 laps with 2:18 optimum's on the Garmin... Im not a great driver and a good driver could probably get 3-4 more seconds out of the car based on my buddy who's car is very similar to mine mod wise and hp wise, but he's a far better driver and can run 2:15's on a similar tire(and 2:13 on hoosiers).

First time out this year I was over braking quite a few corners and my fastest time was a 2:21, but I think I only got one lap like that on day 1, mostly like 2:23's... was disappointing as the car felt slower. Day 2 I went out for some "advanced coaching" and the 1st instructor really helped me with my gear selection and where I was over braking simply to grab a lower gear and to trust the car more in a higher gear. I forgot to start my Garmin so no clue, but im sure my times were nothing to worry about since we were trying things. Second session with a different "advanced coach" and we worked on that plus a few other little things and I ticked a 2:20 with a passenger. HOWEVER I will say, overall, the 3.6 to 4.30 swap was IMO a neutral swap on my "stock" powered VVT car. I made some money selling my 3.6 and moving to the 4.30 so I'm not mad, but it was a bit of a disappointment to go out and go "well that didnt do what I thought it would"... I felt the car was lazy out of some corners with the 3.6 where 2nd was to low and 3rd was lazy. The 2 to 3 ratio difference in the 6spd is pretty dramatic. 3-4-5 is pretty close. I was expecting better things, and maybe they will come. I wont be on that specific track again until at least the fall unless I go out there this summer(which I doubt).

Thats probably the last change I make to this car as I have an LS/TKX/8.8 swap on deck for next off season if I can get all my parts by then...

cabowabo

At a 136whp it was awesome *at the right tracks*, some of my tracks (Texas at that time) it actually put me between gears so much I don't think it helped vs 4.1. I was constantly running out of 4th at the end of straights and holding it vs shifting was about the same whereas the 4.1 was in the meat of 4th still pulling. So, really, it depends on gearing of the tracks you're going to imo and what your dyno looks like. The more peaky your power the more it should help, the flatter your power the less it'll help. If it's a street car then 4.77s suck, made being on the interstate miserable.

Bloopdog

Try not to grill me too hard here.
2002 vvt 5spd stock power, give or take 5hp, exhaust intake that sort of thing. This is my daily driver. I have seen plenty of differing opinions ("You're going to be shifting more than driving!!!!!!!!!!!" , "it was the best upgrade for my n/a car!")
No track use, I deliver pizzas in it. However I RARELY highway drive it. 99% rural driving as i live in a smallish town. Just want to add a bit of pep to the car without boosting it ( reliability concerns ), as most of my acceleration is low down in the gears from stop signs.

also the "constantly shifting" is not a problem to me it tends to give my adhd mind something to do.

Z_WAAAAAZ

Not here to grill at all! Just curious. Your situation makes sense.

Not the same setup but, FWIW, running a 6 speed/4.3 ratio in my car didn't make it awful for daily driving. It was suboptimal on the highway compared to my current 3.6, but didn't bug me at all. Again, different setup, the car was running 270whp at the time, but I didn't feel like I had to shift too much either. ADHD here as well lol.

Have you considered dropping in a lighter weight flywheel? Dropping in a 9lb flywheel when my car was N/A made a big difference in acceleration in 1st and 2nd gear and (IMO) wasn't too hard to drive.

cabowabo

Imagine having a manual car and being afriad of shifting. If I wasn't lazy and poor I'd be putting a 6spd/4.1 in my ~200whp turbo racecar. 4.78 isn't appreciably increasing how much you shift at stockish HP, it's just a bit more fun/peppy imo. If you're not cuising at 65+ often (or ever) then let 'er rip tater chip. I loved 4.78s EXCEPT for sitting at 4700rpm on interstate (non optimal gearing on some tracks aside)

rascal

Hmm, your two quotes contradict each other.

changing your gearing isn’t going to magically add 50hp to your car.

changing to a shorter (Numerically higher) ratio doesn’t really change your acceleration at a given speed because you’ll be in a higher gear to make the same speed which negates the torque multiplication advantage of the lower gear.

Where it can benefit you is by reducing the fall off between gears as 3,4,5 is closer together than 2,3,4 ratio wise.
Eg changing from 4-5 at 7000rpm may only drop you to 6000rpm whereas changing from 3-4 at 7000rpm might drop you to 5500 so you are further off your cars power band.

if your buddy flew past you in his NA with supposedly similar power, then I’d suggest most of that was due to a weight advantage an NA has over a NB2 or he just got a run on you, or you were in different parts of your rev range.