FDNewbie

iTrader: (10)

Dave, thanks for the info re: the 3.9. I hate to keep asking (simply b/c I don't know the calculations), but what are the top speeds for the V160 and V161 using a 3.9 rear?

Also, Dave, you mind sharing the sources for those prices for the benefit of the forum?

One more...please keep in mind that you should *never* buy US-rebuilt Getrag. I've heard horror stories about them. From what I've heard, when Getrag (in Germany) makes them, the tolerances are so small, that they bathe everything in hot oil, and install it AS SUCH. So stateside rebuilds have had all sorts of problems. I'd stick w/ new, low mileage used (if you can verify it from a trustworthy source), or factory refurbished - which is done by Getrag in Germany.

My $0.02,
~Ramy

patman

iTrader: (3)

ramy,

try RPM *1/gear ratio*1/rear end ratio*tire diameter (inches)*pi(3.14159)*1/63360 (inches per mile)*60(minutes/hour)=speed with no slipping.

pat

FDNewbie

iTrader: (10)

Patman...THANKS! Here goes...

The following was obtained assuming shifting @ 8500rpm, using a 335/30/18 PS2 (25.9" tall), and the following FD gear ratios:

1 - 3.483
2 - 2.015
3 - 1.391
4 - 1.000
5 - 0.719 (USDM)

...And the following stock Getrag ratios:

V160 (USDM)
First Gear: 3.830:1
Second Gear: 2.360:1
Third Gear: 1.680:1
Fourth Gear: 1.310:1
Fifth Gear: 1:1
Sixth Gear: 0.790:1

V161 (JDM)
First Gear: 3.724:1
Second Gear: 2.246:1
Third Gear: 1.541:1
Fourth Gear: 1.205:1
Fifth Gear: 1:1
Sixth Gear: 0.818:1

I hope my calculations are right!
~Ramy

RX-Heven

iTrader: (1)

A junkyard search engine and looking around on the Supra furums.
http://car-part.com/

New V-160 6-speeds for $4400. He also said V-161 are harder to come by and the price has gone up.
Ben Phillips
President/CEO
Phillips Research & Engineering, INC.
WWW.PRE-RACING.COM

FDNewbie

iTrader: (10)

Thanks Dave

Oh and re: my calculations above, I think a JDM Getrag (V-161) would be perfect on a 3.9 rear, but using a USDM (V-160) Sixth Gear (0.790:1 ). What are your impressions guys?

~Ramy

RX-Heven

iTrader: (1)

Perfect is in the eye of the beholder. Personally I like the 3.73 gearing with the PPG set.
Stock Getrag v-160 w/ 4.1
vs.
PPG Getrag w/ Cobra 8.8 and 3.73

RX-Heven

iTrader: (1)

I have a question for Carlos.
The Supras run a 2-piece driveshaft because of the flange on the tranny. Are we going to have to run a 2-piece driveshaft also or will a custom made 1-peice work?

FDNewbie

iTrader: (10)

Of couse it is. But I'm weary of using a dogbox set on the street. It definitely has it's fair share of dangers... Otherwise I'd be all over the PPG set.

Oh and I'm all ears as to what you see as perfect and why. It'll help me see what I'm overlooking

~Ramy

t-von

iTrader: (8)

Slightly off topic! What are you guys doing with all the wiring that comes from the Fd tranny in your 20b conversion? I know one is for the speedometer. What about the others? I'm curious since this wiring goes to the stock ecu. I'm going to move my engine back and relocate the shifter in the front cover section. When I took that front plate cover off the tranny, I noticed a 2 stage switch that gets activated when the gears are in 1st and second. I also noticed a mechanical arm underneith that gets actuated in 5th gear. Anyone have any info on this stuff?

red87tll

iTrader: (4)

not quite what you want, but for the TII tranny i just redid the wiring to the front harness. one set of wires is the reverse switch, one is the neutral safety switch...i would imagine that the FD also has both of those items. TII speedometer is mechanical so i dunno about that.

this is patman btw, im on my roommates laptop.

rarson

I agree! I've seen a lot of nice dog boxes for a lot of different cars and while there's a lot of things I would potentially like about them, I don't think they are worth it for a street car.

RX-Heven

iTrader: (1)

Again, this all depends on the application.

For road racing you want a really tall 1st gear, one that will put you at a desirable rpm (totally dependant on the engines power curve) through the slowest turn and upon coming out of the exit, ready to grab the next gear. Your lowest gear is the starting point and from there, you want each succesive shift to place you in the desired rpm range that will incrementally climb as you go through the gears and ideally, without having to change gears anywhere through a corner. This is where datalogging is crucial as you will be able to see what the speed is going into, through and out of a turn. This will enable you to select the appropriate gear ratio based on your power curve the and the gears (maximum allowable) multiplication of force to maximize acceleration.
Ideally these would be changed for each course and that is why places like Hewland and Jericho have a HUGE selection of ratios.

I'm not a drag racer but I'd imagine they would look for what rpm and speed they are at in 4th gear when they go through the traps and try to match that to their redline/peak power. Then maybe work backwards to first gear choosing one that is low as possible without multiplying the torque too much so barely maintaining traction will accelerate the car as quick as possible.

For the street, a first gear that is not to tall so you can get started on a steep hill (I live in SF) but not so low it becomes useless, a nice overdrive ratio for freeway cruising and a nice incremental climb through the gears in between. A compromise in all areas.

Then there is Howard, who wants to do the Silver State Classic....

Incremental changes can best be seen and described graphically.
The tractive force graph clearly supports why Howard believes 1st is useless with the Getrag and both graphs show why Crispeed thinks 5th and particularly 6th with the bT-56 is useless, except for fuel economy

Getrag v-160 w/ 3.90
vs.
T-56 w/ 4.10









Besides the practibility and hassle issues, what is the problem with them. Dangers???
I've built and driven dog boxes, though all in VW transaxle cases with Hewland internals in Star Mazdas. I don't see a problem.

Then again, my car, and it seems my life, is an excersize in inpractical absurdity.

FDNewbie

iTrader: (10)

That makes a lot of sense, but as you said, I think that's very track-dependent. If you're not starting out w/ a slow turn, then your biggest concern would be gearing in 2nd and 3rd, since that's what you'll spend a lot of time in around the tighter turns. Either way, thanks for bringing that to my attention. I honestly never even took that into consideration. I think that's a wee bit past my level of preparation lol.

Here ya go: http://www.espritfactfile.com/videos/racing/GT1-1.ASF. Notice at the very end on the video the driver looses control of the car from too many downshifts causing a lot of sudden and violent changes in shaft speeds. This change reflects upon the output shaft and input shaft even with the clutch disengaged. When he was at the limit of his tires' grip, a simple gear change with dog gears caused his tires to loose grip and spin out. This one of the prime reasons not to run dogs gears on the street.

~Ramy

RX-Heven

iTrader: (1)

The tranny, in all likelihood, probably had nothing to do with that spin. That was driver error. He either missed a shift (going to 1 instead of 3 for ex.), grabbed the gear too early or undermatched the revs when downshifting. From the sound of it, you can here the engine overrev as the tires lock up and hebegins to loose control. All of those scenarios can be matched with a normal synchro'd box.

Besides, no one should be driving like that on the street in the first place, thereby eliminating (or at ruduce) the chance of of error.

mirabile

Ramy do you know the driver in that video?

mirabile

Ps. Someone Should Sticky This Thread In The 20b Section

Howard Coleman

iTrader: (6)

yes, some good stuff in this thread. perfect solutions still await discovery.

just a couple of comments...

i ran a saenz non syncro'd box in the last 3 years of my racing. we changed gears for many tracks. for Road Atlanta we geared first so as to come out of the slowest corner (the Keyhole) at 7000 rpm which was to lowest rpm we ran the motor. so, yes, that's how you do road racing...

as far as 5th gear being unusable in the T56... i don't understand the logic. it is .74. that's a pretty decent (not perfect) spacing v 4th. 6th of course is an economy gear. the C5 has good looking ratios given many of the alternatives. we all have different objectives.

my car, with my twin TO4 setup, is making over 500 rear wheel hp at 6000 rpm. there is another 100 up the scale... the 500 is at 19 psi w pump & methanol. i don't need to shift at 7500+... (sure it would be nice, but i can live without it).

a properly set up and driven 500 rwhp fd will bury just about anything on a road course and given the fact i am not wanting to run a roll bar or fuel cell it is enough for me.

i will take the tradeoff.... a brand spankin new trans w 07 internals, easily available parts for a hair over 3K. it may work well for others.

color me non-hardcore.

hc

RX-Heven

iTrader: (1)

Exactly.

Why would a drag racer want an overdrive gear, or two for that matter?
Answer is he doesn't. Probably wouldn't want anything taller than a 1:1 and let the rear-end gearing do the rest.

Why would a road racer want a super-low first gear, except for MAYBE pit cruising as Carlos stated?
I don't. I also don't need to go faster than 180 mph (if even that) for any road course I will ever be on. I'd rather have a broader selection of gears within MY usable range.
Howard, I still think for your application, with the exception of the higher cost and availibilty, that the Getrag, in combination with a Cobra 8.8 and gearing 3.73 or taller would be better suited for you. The work and time just to fit the Getrag is already done and should make up some of the difference in cost (even with purchase of the conversion kit factored in). New factory Getrag's are available for $4400.
My $0.02.
I don't think you are fooling anyone with that statement
He changed his mind again.
I got the used (in need of a rebuild) tranny, upgraded output flange and the matching 1 piece aluminum driveshaft for $1800 shipped

FDNewbie

iTrader: (10)

Why the 3.73 gearing? The PPG gears are pretty nice as is, esp. w/ a 3.9 auto rear. Do you really think the improvement w/ the 3.73 over the 3.9 is THAT great? Moreover, you know you can request custom gear ratios from PPG, right? That way you can leave the diff untouched (if you calculate based on the 4.1 rear) or use a 3.9.

PPG Standard Ratios (custom ratios available upon order):

3.20 / 2.19 / 1.56 / 1.20 / 1.00 / 0.83

-------- PPG using 4.1 rear -------- PPG using 3.9 rear -------- PPG using 3.73 rear
1st ------------ 50 -----------------------------52 ------------------------------- 55
2nd ----------- 73 ---------------------------- 77 ------------------------------- 80
3rd ----------- 102 -------------------------- 108 ------------------------------ 113
4th ----------- 133 -------------------------- 140 ------------------------------ 146
5th ----------- 160 -------------------------- 168 ------------------------------ 176
6th ----------- 192 -------------------------- 202 ------------------------------ 212

RX-Heven

iTrader: (1)

I don't know what rpm's, tire size/diameter you are using and I'm assuming you are not factoring in any tire slip.

1. All tires slip and 3% is the accepted "standard" norm.
2. I'm running 345/30/18 ---> ~25.4" corrected diameter
3. Assuming a 7500 rpm shift

Also, I have an FC so stuffing an auto 3.9 ring and pinion into the TII diff is not an option like it is with the 3rd gen guys. It won't work. FC guys are stuck with 4.10's or 4.30's unless they run the weak-*** n/a diff's that have the 3.9 which really isn't an option. The 3.9 diff is really just too low for what I am looking for. I'm not interested in acceleration from a standstill.

So, instead, I am installing a Cobra diff as I mentioned earlier. They come stock with 3.55's that are also close to what I am looking for and may actually run it to try it out. The only available 3.9 is from Moroso and they whine like crazy (so I hear). That may sound silly since I'm considering a straight cut gear box. However, straight cut gear boxes actually get quieter (er, less loud) as you go up through the gears. Whiny diffs get louder the faster you go. There has to be some relative peace and quiet somewhere

I'm pretty sure PPG does not have different gearsets available for the Getrag without being special ordered ($$$$ to start with + $$$$$). The exclusive US distributor of the gearset is Powerhouse Racing and they mentioned only one gearset is available when I contacted them.

IronMdnX

iTrader: (1)

Any pictures or updates on this kit?

FDNewbie

iTrader: (10)

I'm actually not sure how you account for tire slip. Do you multiply the value you got by 0.97 to allow for 3% slip? (That's my guess, as the forumla Patman posted for me didn't include a variable or conversion factor for tire slip...

Also, is this variable affected by traction control systems?

As for your other factors, here ya go: Understood. But I was actually referring to your comment to Howard, re: suggesting he use a Getrag PPG w/ a 3.73 rear. He's running an FD, so he can use a 3.9 on the stock diff no prob.

Yes, it's by special order only, but it IS possible.

Re: availability (and more importantly price), see my post in your thread on the Supraforums.

Oh and btw Dave, please don't take my line of questioning as being confrontational. Rather, I'm just trying to learn about the things I'm overlooking

GT1-20b is busy ATM; give him a week or so.

mirabile

^^ he is always "learning" instead of answering emails

FDNewbie

iTrader: (10)

^^^^^ And attempting to bust my chops only displaces your email further down the list

patman

iTrader: (3)

yes, the speed * .97 would account for 3% tire slip, but tire slip is such an open variable that there really is no reason to include it in formulae (CONSIDERING STOCK tii is an H rated 205 serisw tire on a 7" rim, wheres I'm running a race compund 275 on a 9, and etc). generally you compute ratios with no tire slip included because that is a function of the specific car you are running and has nothing to do with gear ratios. it may limit top speed slightly, but when comparing trannies for street or road racing that isnt really a factor. as long as you use the same forumula for all trannies being considered the specigfic variables arent that important.

ps let me know if that made no sense, im really drunk right now.

pat