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4.39 gear ratio not short enough
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Author:  beached [ Mon Feb 27, 2017 12:26 am ]
Post subject:  4.39 gear ratio not short enough

My rev limiter is set to 8300 2nd gear goes to 100kph 3rd takes me to 160kph.
Can I have a final gear custom made to make the gearing better?
To me 2nd should go to 80kph and 3rd to 130kph or less to make the car perform better.
Even the 4.39 seems way to long for me.

Author:  Mr Murf 59 [ Mon Feb 27, 2017 11:36 am ]
Post subject:  Re: 4.39 gear ratio not short enough

SRD has some custom ratios. I got boned pretty hard by them so I don't do business with them. Also you might get a holed of Dattman both on here and at GMF. He might have a line on some. What about changing this size of your tires? Its the cheapest and easiest to do.

Author:  codyb76 [ Mon Feb 27, 2017 5:21 pm ]
Post subject:  Re: 4.39 gear ratio not short enough

Would oversea gti trans gear ratios be an option? It would give you closer 2/3/4 ratios I believe. Dattman will know this like the back of his hand

Author:  Dattman [ Mon Feb 27, 2017 8:00 pm ]
Post subject:  Re: 4.39 gear ratio not short enough

beached wrote:
My rev limiter is set to 8300 2nd gear goes to 100kph 3rd takes me to 160kph.

Welcome to the wonderful world of suzuki gearboxes :lol:
1st and 2nd is the same between all boxes, changing to gti 3rd, 4th and 5th gears might mean doing 150kph in 3rd instead, a 50kph spread is better than a 60k spread.


beached wrote:
To me 2nd should go to 80kph and 3rd to 130kph or less to make the car perform better.
Even the 4.39 seems way to long for me.

Personally 1st gear should do 75kph, 2nd 105kph, 3rd 135, 4th 165 and 5th gear should max out at 195, 30kph spread between all gears means you are always in the power band, however this requires a full close ratio gearbox, if you are interested then I know Rougeracer is looking to sell a set of my close ratio 1st & 2nd gears with gti 3rd & 4th gears which will get you pretty close to my ideal depending on tire size.


FDGTI often has custom final drives and this will lower your road speed for any given rpm, however to get 2nd down to 80kph means 1st gear would only do about 45kph which means it's almost unusable and you're still stuck with massive gaps to 3rd and 4th.

Author:  beached [ Mon Feb 27, 2017 9:55 pm ]
Post subject:  Re: 4.39 gear ratio not short enough

I thought the 4.39 was shorter than gti? :huh:

Author:  Dattman [ Tue Feb 28, 2017 12:56 am ]
Post subject:  Re: 4.39 gear ratio not short enough

You're confusing diff/final drive ratio with gear ratios.

Gti ( not North American ) are lower ratio gears with a slightly taller diff ratio, ie 4.1
Using standard gears with a lower 4.389 gives similar speeds in 5th but a wider speed gap for each gear.

Heres a graph plotting standard gears with different diff ratio's using 195/50/15's, as you can see the road speed changes in each gear but the amount of rpm you drop when changing gears is exactly the same.
Image

So changing from a 4.389 to a custom 5.1 final drive would change 1st gear from 60kph at 8200 to 51kph and 2nd gear would drop from 107kph to 92kph, the big problem there is 1st gear is way too low and the shift from 1st to 2nd means the revs drop from 8200 to 4500.

Heres a plot of what you have (red line) compared to a sqs close ratio gearset.
Image
Notice 1st gear is taller but when changing into 2nd gear the rpms only drop to 6000 rpm, when I look at my dyno chart my engine only makes 65hp at the wheels at 4500rpm, at 6000rpm its making 90hp atw, thats 35hp more power to accelerate with :twisted:

Author:  TGstring [ Tue Feb 28, 2017 4:57 pm ]
Post subject:  Re: 4.39 gear ratio not short enough

lemme tell ya Levon,
There is no inexpensive or budget solution to this issue.
It's inherent to the car and options.
None of them are easy, cheap, or readily available.

There are very expensive solutions to this, but it's unclear what the real problem is (that is to say, what does it really matter ...is the car not fast enough? or are you losing tarmac rallies due to the setup?.... )

Enjoy the car and stop dumping money into it.

I tried a bunch of different tranny setups when I had it and none of them made any real difference. Truth.
Other than a NOS OEM SuzukiSport LSD which made going around turns "fun", there were no real differences between the "closer" Gti gears, the 4.39, or whatever other combos I tried. I found the 4.39 made 1st gear useless as I was plagued with traction problems. It's a give and take.

Author:  t3 ragtop [ Fri Mar 03, 2017 7:28 am ]
Post subject:  Re: 4.39 gear ratio not short enough

what tommy said is true.

even with its short comings my favorite gear set is the 4.39 in both my turbo3 and twincam verts. the turbo3 develops power and torque differently than the twincam where a really short 1st gear helps to spool the turbo and get the engine rpms up very fast for the shift to 2nd.

the twincam is in my street car and if i am to aggressive with my right foot the tires just smoke. i have a faux lsd in the transmission so both tires spin. about the only things i find useful from the 4.39 is that my top speed is higher (yes i know that the gearing is lower. my theory is that the engine's higher rpm makes a fractional difference in power output at wot which pushes through the wall of air ahead of the car just a little bit harder.) the other thing is that when i shift to 2nd it fakes out the honduh boy racer next to me and he short shifts 2nd. my engine rpm is right on the money for 2nd gear while the honda's engine rpm is too low for his 2nd gear shift point.

all the custom special ratio gear sets i see out there are incredibly expensive. that money probably would be better spent on liquor and women of ill repute. =)

Author:  suprf1y [ Fri Mar 03, 2017 12:31 pm ]
Post subject:  Re: 4.39 gear ratio not short enough

It's a small motor with little torque that will rev. It wants gear. Lot's of gear. There's a reason that those final drive ratios are available aftermarket.

The 4.39 was probably the best addition to every G series car I've ever worked on and they still wanted more, but Tommy's right, it doesn't make sense to keep putting money in it. You've reached the point where a lot more money will be required for not a lot more gain.

Quote:
all the custom special ratio gear sets i see out there are incredibly expensive. that money probably would be better spent on liquor and women of ill repute.


Despite his suggestion otherwise, Tommy still spends more money on Trannies than anyone I know.

Author:  suprf1y [ Sat Mar 04, 2017 7:10 pm ]
Post subject:  Re: 4.39 gear ratio not short enough

Want to see what kind of difference more gear will make? Put some 20" diameter tires on it, and see how you like that.

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