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- VIDEO - Ok.. I know I love the SR20DET powered 240Z.. now it's in action!


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You should be pretty light, my 71 I had ages ago, with full interior, spare and ac, with about a half a tank of gas weighed in at 2250.

 

So you have the figure the SR is lighter and you lost a lot of spare parts with the car as well, I would no doubt think you are at least in the 2000 range.

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  • 2 weeks later...
I'd be interested to hear what the differences are with that engine and a higher ratio. I'm of the opinion that lower ratio is better for turbo engines, but I'm always willing to hear of others' experiences.

 

 

In my experience, thats not true. Sure, the longer gears help spool the turbo, and thats great. But, the faster you go across your power band and get into the next gear, the faster your car is moving down the street. Longer gears make the engine rev slower, and that makes the car slower.

 

In my 180sx, I ran a two-step rev limiter to spool the turbo off the line. It would boost 1.6kg (~22psi) from the moment I shove the gas to the floor. Coming off the line with a 4.90 rear end, an OS Giken close-ratio tranny (with a taller 1st gear than stock) it took off like a bat out of hell. :icon44:

 

Just to give you some perspective, heres a link to the dyno video of my old 180sx with SR20DET with a Tec3 ECU, and a T04S turbo. It made 399.8ps at the wheels which translates to 395 rear wheel horsepower. (at 1.4kg of boost)

 

http://72.29.75.31/~videof6/features/hugh/HughDyno399.mpg

 

Notice how short the run on the dyno is. From the moment the wastegate opens until he stops is very short. It's also 5th gear, because thats the only gear that would hook up on the dyno. (and I still had smoke from the tires, even with people in the trunk for extra ballast - so power was being robbed on the dyno) The short gears make it want to rev so quickly, the tires couldn't push the rollers fast enough.

 

Now if that car winds up that fast in 5th, and the Z pictured here winds up that slow in 4th... which car do you think will win in a race? I think the answer is obvious.

 

Granted, top end suffered. It would only go about 150-160mph. However, it would rip all the way to redline in 5th gear without a hint of hesitation. (hitting top speed was EASY)

 

You don't want something crazy like a 4.90 on a stock transmission, though. A 4.66 maybe, 4.36 is best I think. Too short = crap for first gear. The OS trannies have tall 1st and 2nd gears, making a shorter rear end a necessity.

 

Now with a short final gear, you must shift very quickly to see the real benefits of it. If you granny shift, you will suffer. I was a shifting fool in my 180sx.

 

 

A side benefit of short ratios is less stress on the drivetrain. When you launch a 3.90 VS a 4.90, the abuse hitting the gears is much worse. Think of starting out uphill on a bicycle in top gear. :)

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Im sorry but a 4.90 rear with a 400whp car is just a waste of power and way to much shifting going on. A 4.90 will make your car "feel" extremely fast since traction is not there until 3rd maybe. I could understand a 4.90 for a very quick exit out of corners on a NA autocross Z, but not on a turbo high WHP Z. No matter how much power you're putting down you always waste time when shifting. I have a 494whp Evo MR that I drive everyday and the stock gearing is too quick to actually put the power to good use. Sure your revs build up quick but a 400whp Z should do perfect with a 3.90 or maybe even a 4.11. So if you were to line up with a Z with the same mods you have exept for a 3.90 rear you would lose in the 1/4, specially up top.

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  • 3 weeks later...

SR240,

I saw this car a while ago, and never got around to saying how f-ing beautiful it is. I love the wheels and the flares. I always thought 17's looked perfect on a Z until I saw those 16's, they look gorgeous! Excellent fit and finish on all the fabrication. So did you ever get it weighed?

 

Hugh and Superz,

You guys shouldn't argue over rearend ratios without including the tranny ratios that you're using. Its like one guy with a .75:1 top gear and a 4:1 rearend, arguing with another guy who has a 1:1 top gear and 3:1 rearend ratio (both have the same wheel-speed). Just trying to help :D

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Sweet mother mary of Jesus!!! I saw that car on the front page of Wheelchoice when I was looking for some Wats and it's my wallpaper on my puter. Now to actually read about it and see more pics of it instead of just that one pic is like breath of fresh air. I love my NA L28 and not a v8 fan I think when the time comes I know where my money is going for the 280's new powerplant. Sorry if I missed this but what did you have to do for mounts?

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