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Re: Has anyone done the VL commo auto swap?
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I was going to be sneaky and use the stock 3N71B T convertor .. Well that killed my brain fart .When you say custom torque converter, helps with take off, What do you mean not with acceleration once at road speed ?? Is it just the same as stock or does it suffer ??

Posted on: 1/14 5:58
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Re: Has anyone done the VL commo auto swap?
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It's the same effect with stock or custom converters

* At low RPMs the torque converter multiplies torque (maximum of 2:1 for the stock 1200 automatic), and as the revs come up you'll get less and less converter torque multiplication

* The automatic 1st is 2.458:1
* The manual first is 3.757:1
Without the converter's torque multiplication, less torque would get to the ground. So it's strong at initial takeoff, but less strong as the RPMs rise


Here's where a custom converter is beneficial. Let's say you order a custom 3000 rpm stall converter from KEAS (stock 1200 stall is a low, low 1875 rpm, compare to 2625 RPM for stock 300ZX Turbo)

* When taking off, the engine will immediately run up to 3000 RPM where the A12 makes 9.8 m/kg torque at full throttle (compared to 8.8 at 1800 RPM) -- that's 11% improvement right there. This is similar to a Manual where revving the engine while letting out the clutch results in faster acceleration

* An off-the-shelf 3000 RPM stall converter won't work exactly right. What is needed is a custom 3000rpm-behind-70ft.lb.engine stall converter. If you were to use the 300ZX converter behind an A12 it will stall at a much lower speed than 2625

You can make up for this torque shortage by fitting a higher number rear diff gear (if you want to match the manual's acceleration). If acceleration isn't important to you no need to change anything -- just live with the slower acceleration of the Auto. The automatic's only got 3 gears (overdrive is not used in 0-100 or 1/4 mile runs) and while the torque converter multiplication helps, it doesn't help as much as the extra gearing

Posted on: 1/14 6:57
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Re: Has anyone done the VL commo auto swap?
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Ha , you read my mind. My next question was about 280zx converter 2400 - 2700 stall. I,ll spend the extra and go custom. I know higher the stall the more heat. Better quality stall less heat. Im thinking bout 2500 stall and cooler just in case. 4.6 lsd sounds good. and will suit the cam. I think its Wades 1009. Should give me cruise speed on freeway of 2800 rpm at 100 ks in 4th. Can always try 4.8 later and give me a cruise speed of 3150 at 100ks As I do alot of long trips. And I want to tow one of those old Tear drop lil caravans.

Posted on: 1/15 5:38
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Re: Has anyone done the VL commo auto swap?
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The great thing about the L4N71B is no need to worry about stall heat in 3rd and 4th -- it's a Lockup converter. The efficiency of a 5-speed on the highway. The R31 Pintara version doesn't have this feature (it's 4N71B) but R31 Skyline does. Don't know which one the GM version has

Overdrive 0.686
Final drive 4.625
100 kph @ 2800 RPM
-------------
That means tyres 23.6" diameter
* 175/70R14
* 175/55R16
* 205/45R17

Posted on: 1/15 6:35
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Re: Has anyone done the VL commo auto swap?
No life (a.k.a. DattoMaster)
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Yes chasing the overdrive legs for the highway but stil want good acceleration.

Posted on: 1/15 19:45
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Re: Has anyone done the VL commo auto swap?
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Really !! I got 23.2"= 588 mm .. 13"> 215 x 60 @ .700:1 = 2800 rpm/ 100 kms approx

Posted on: 1/15 21:40

Edited by nickmitty on 2017/1/15 22:15:26
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Re: Has anyone done the VL commo auto swap?
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Yes, with the Overdrive Auto and 4.625 diff, you can have both (equivalent to 3.2 final ratio). Less RPMs on highway than stock 1200 = more fuel economy, quieter, and engine lasts longer. It'll have to shift down to 3rd to pull hills


215/60R14 is 24.2" diameter per manufacturer

23.2", for example 195/60R14 is 900 revs/mile (measured on a 6" wide rim). Air pressure will alter the diameter too

Posted on: 1/15 23:08
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Re: Has anyone done the VL commo auto swap?
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4.8 would take it upto 3000 rpm @ 100 kms and 4350 rpm in 3rd .. very tempting. Would help hill starts etc whilst towing . And could rekindle my youth as the burn out king unloaded.

Posted on: 1/15 23:30
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Re: Has anyone done the VL commo auto swap?
No life (a.k.a. DattoMaster)
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hahahaha yes there will be a line locker added to the build as well as being fully manualised for those wet weather skids.

Posted on: 1/21 9:33
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Re: Has anyone done the VL commo auto swap?
No life (a.k.a. DattoMaster)
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Nick got to footscray autos if they are still around
best trimatic and jatco place anywhere in melb for prices and honesty

Posted on: 1/23 8:39
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