Hi guys, new user here. I have an 81 280zx that I did a turbo swap on for about the last 6 months. Right now I still have the stock 3.9 out back which kinda sucks for straight line/top end but i'm wondering if it might be good for the track? I have an 82zxt parts car that I can pull the 3.54 from. I've only heard that the higher gears for drag racing, but what about road courses? Thanks for any input. check my car out here

Brandon

 

it really depends on the track, nissan also made a 3.75 as well for these cars, your setup will depend on the track. now correct me if im wrong here guys, but ive also heard that the open diff is better for road racing around sharp corners, simply because the car needs less hp for the car to turn, if you had lsd, it would need mmore power, and more potential to spin, hence the need for the lsd in the drifting world. so if its a short tight track, use the 3.9, if its a long smooth course use the 3.54, or the 3.75.

 

Yes, 'real' road racers have a number of different ratios that they use depending on the track they're competing at.

There's no 'one ratio fits all conditions'.

An advantage of the 3.545 gears in the turbo cars is to keep the car in the same gear and the boost on for longer periods of time. This is better for long sweeping tracks but can affect your exit speeds on tight corners.

As Shady mentioned, the LSD needs to be setup properly for the type of track as well. You get more initial understeer with an LSD going into a tight corner until the back end starts to come around and then you have more oversteer which people like to call a power slide which has now turned into drifting...

For my purposes, I prefer a 1.5 LSD with a 3.7:1 gears for general road racing my 240z and I have a 1.5 LSD with 3.545:1 gears for drag racing.

 

Speaking of which... Do you know if the stock Z31T LSD was a 1 or 2 way?

 

Use a helical ATB LSD diff center like a Quaife if you can, they are better for road racing than the clutch type LSD's. This assumes the suspension basics are right eg no rear wheel lifting in corners.

 

I believe it's a 1 way, but it may be a 1.5 way. '87 may be too early for the 1.5 way, but it's definately not a 2 way. I'll have to check.

 

The Quaife is substantially more expensive, like on the 2.5 to 3x range.

You can get a new Precision Gear - Power Brute clutch LSD center section for a little under $600 and have it installed and the pre-load set for your driving style and still be under the $1000 mark.

The Quaife will be nearly $1300 minimum and then you still have to have it installed by a knowledgeable diff guy easily driving the final price into the $1700 to $2000 range.

 

Thanks for the input guys. I think i'm gonna still with the open 3.9 for a bit right now...get some track time and see what will work. Anybody here familiar with Infineon raceway? Thats where I plan to go in the next couple months.

Brandon

 

Man I wish I lived near some of these awesome tracks. I'd love to take a run on Infineon.

 

This is part of my problem... I want to move out of Cali, but I can't stand being somewhere that doesn't have SEVEN world class race tracks within driving distance...

From north to south: Thunderhill, Sears Point, Laguna Seca, Buttonwillow and Willow Springs in California with Reno-Fernley and Spring Mountain next door in Nevada!

All these tracks are on the ZDriver Frappr site at:

http://www.frappr.com/zdriver

 

Move to holland, we have the Dutch TT track ( world GP) the Zandvoort track ( F1 A1 DTM track), Spa Francochamp ( F1 and DTM and whatnot), Hockenheim (F1 DTM) Nurbergring Nordsleiffe ( does it need explenation???)

 

Can I bring my gun collection?

 

i love to drive nurburgring on gt4 in my 280z, its a blast out running the vipers!!

 

Problem with high rpms on the highway is that the car goes into open loop the minute the engine goes over 3500rpms.....or is it 3700.

Either way, you're just running on the map provided by the spring in the airflow meter and the temp sensors once over that speed.