3.15 R200 LSD with 2JZ-GTE and 5spd R154?

[ShaggyZ]

I recently acquired a 3.15 LSD R200 from slow old car for more money than I should have spent on anything extra I knew I wanted to go lower than the 3.7 LSD, which I bought for $500 with CV's a few months ago BEFORE finally settling on the 2JZ over the L28ET or 4G63 of the GS-T Eclipse.

 

AFTER agreeing to buy it, I finally did research on what a 3.15 final drive ratio will do to my overall gearing and speeds. Aerodynamics, tire stretching, and skidding aside (ha!), at 7k RPM I could hit 208MPH. Of course, I'd have to be making at least 800HP, no doubt; but that's not up to discussion right now as there are so many factors involved there.

 

I really just want to get your thoughts on: how "livable" and streetable will it be, including traffic?; is the gap between gears going to be too great to keep me in the powerband?; will this be sucky for 1/4 mile racing? will this suck for possible road racing I may do in the future?; anything else I need to consider. I fully intend to drive this thing fairly regularly, which is one HUGE reason I went for the 2JZ over L28 - reliability at those power levels.

 

I've just seen too many Z's with too little (read "short") gear through 1st and 2nd, making them completely useless - 1st doesn't even get a chance to load up the engine and turbo. Obviously, a good, sticky, wide tire (at least 245mm) will be in order and the LSD is going to be helpful.

 

Notice that the R154 gearing with reasonable height tires (245/40/17) and the 3.15 rear end is fairly close to the stock Supra setup with its 6spd and taller (stock) tires and similarly geared rear; however, that is spread across 6 gears instead of the 5 of the R154. Also, the Supra weighs in at a minimum 500lbs more than my 280Z (assuming a ~2600lb weight) and I've heard upwards of ~3400lbs for stock twin turbo, 6spd Supras, which makes it ~800lbs difference.

 

I plan on sticking with stock twins for now and will shoot for low 400HP at the wheels minimum and possibly aiming for low 500's eventually. I'll likely upgrade to a T61 or the much-loved-as-a-street-turbo T67 before long.

 

Pay particular attention to the gap between shifts (assuming 7k RPM redline). Lets also assume that the 2JZ can make just over 200HP by 2500RPM and hits 400HP by 5500RPM and the torque isn't far off. I really need to get a dyno graph out - I'm mostly gaging off of dyno vids of Supras, Clifton's powerband, and various other, uh, things.

 

 

3.15 LSD R200 with R154 gearing (if link dies, ratios are decipherable in link)

http://www.car-videos.net/tools/speedrpm.asp?Car=Select&Num1=245&Num2=40&Num3=17&AxleRatio=3.16&Ratio1=3.25&Ratio2=1.955&Ratio3=1.31&Ratio4=1.&Ratio5=0.753&Ratio6=&Ratio7=&Redline=7000&Increment=500&B1=Recalculate

 

Stock MKIV Supra Twin Turbo (specs taken from here: http://mkiv.supras.org.nz/specs.htm)

http://www.car-videos.net/tools/speedrpm.asp?Car=Select&Num1=255&Num2=45&Num3=17&AxleRatio=3.266&Ratio1=3.827&Ratio2=2.36&Ratio3=1.68&Ratio4=1.312&Ratio5=1.1&Ratio6=.79&Ratio7=&Redline=7000&Increment=500&B1=Recalculate

 

 

For reference, here's the speeds for the 3.7 LSD R200 with R154 in the Z.

 

http://www.car-videos.net/tools/speedrpm.asp?Car=Select&Num1=245&Num2=40&Num3=17&AxleRatio=3.7&Ratio1=3.25&Ratio2=1.955&Ratio3=1.31&Ratio4=1.&Ratio5=0.753&Ratio6=&Ratio7=&Redline=7000&Increment=500&B1=Recalculate

[IdfMF]

ShaggyZ

 

I have a 3.15 R200 LSD but am using a T5 World Class, Chevy 350 and 235R/50/16s. My engines power band, according to the cam spec is 1,500 RPM to 6,500 RPM. No dyno numbers yet, but I should be around 350 RWHP. No 1320 times yet

 

Here's a comparison of gear ratios between the T5 and the R154

 

Gear: T5 R154

1 2.95 3.251

2 1.94 1.955

3 1.34 1.310

4 1.00 1.000

5 .63 .750

 

The T5 is bit tighter going from 1st to 2nd, but otherwise the gear patterns are pretty close. I LOVE having the 3.15 rear end. I can really take advantage of torque and am not constantly shifting. My combo is a blast to drive, mainly because I do not run out of gear too fast. I have seen videos posted on HybridZ where guys are doing 1-2 shifts almost as soon as they come off the line. Another plus is that I am not spinning tires when I stand on it in 2nd and 3rd. The Z just digs in and pulls.

 

My car is mainly going to be street driven. I would think that as long as you do not build your engine to be too peaky and can still maintain good torque above 2,500 RPM, you will have a good combo with the 3.15. I broke the law last week and jumped on it from 35 mph in 2nd. I was shocked how fast I got to 120 mph in 4th with revs to spare.

 

I guess the only complaint with the 3.15 is that the revs drop off a cliff going into 5th at anything below 75 mph.

 

Have fun!

 

Tom

[calpoly-z]

I've got a spreadsheet from back in my ground vehicle dynamics class that would probably help you out with this. it takes hp and torque curves and gear ratios and final drive ratios along with loading (both aero and rolling resistance) to calculate power requirements at various speeds and rpm. It also plots out tractive effort and horsepower in each gear. It makes a lot of simplifications, but it also uses a lot of detail so I feel its pretty accurate. I don't know if I host this on hybridz or if I need some other hosting site. Otherwise I'll just email it to whoever wants it.

 

oh and it also estimates time to speed so you can see how fast your car is based on traction available

[rudypoochris]

Is that the same spreadsheet at the "Quarter2" calculator in this download forum here?

[calpoly-z]

I don't know what the quarter2 spreadsheet does, but I went ahead and attached my spreadsheet. It will probably be pretty confusing as there is a lot of data to be input and some of the abbreviations are a little strange. Feel free to ask me if you have any questions about something.

 

Just to give credit where it is due, Cal Poly professor John Fabijanic designed the template, but all formulas were put in there by me so there may be some error, though I think I did it all right.

Performance Workbook, Template.zip

[rudypoochris]

Check this one out, I think it has less of a learning curve. I cannot attest to the accuracy, but it seems to work pretty well. Requires macros on.

QuarterMileCalculator.rar