"Safe" Launching

[turbowop]

Quoting bazeng:


I'm running a TRE spool without a viscous coupling.

If you look at the dyno graph, it shows that the rear makes quite a bit more power than the front wheels.

I'm not sure why, I would have thought that if it were 50/50, I would have exactly the same power front to rear.

Anybody have access to a dyno who can dig up a old run with a locked centre, and set the graph to show front and rear power?




TRE spool is essentially the same thing as a welded center diff. I'm not sure why your dyno graph shows that power difference, but it has nothing to do with your transmission or center diff being locked with a TRE spool.

 

[Brianawd]

Yes the gvr4 1st gear is weak. I would not put one back if my trans even if some one payed me to. Why take the chance of it braking. When that brakes it brakes the teeth off the intermediate shaft.
As for the 4spider

click
click
click

 

[bazeng]

A guy here in Aus had a spare centre diff, had his housing machined to suit 4 spiders.

I believe this is the way to go. I've heard the Quaifes arent holding up these days due to manufacturing change.

TRE do this.

 

[turbowop]

Quaifes were never really meant for drag racing anyway. The shock load from launching can break them. 4spider or welded is the way to go for drag.

I've blown up a gvr4 first gear before also, but have yet to mess up a stock 2spider center diff. It is one of those things that worry me about launching the car, something I haven't done since the twin disk install. The transmission in my car now also still has a gvr4 first gear. /ubbthreads/images/graemlins/uhh.gif

One of the main reasons I haven't raced the car in so long is because I want to build a tranny with all Evo3 internals. Better synchros, stronger gears. It's like having all the best parts of the various years of DSM transmissions put together into one gearbox. I just have a hard time paying so much money just so I can race again, especially having just bought a house this year amongst other things.

 

[Brianawd]

^^^^^^^^^^^^^^^^^^
Its all good. Keep it a show car. You make us proud /ubbthreads/images/graemlins/hsugh.gif

 

[turbowop]

Hey Brian, how many miles did you put on your car this year? Not including jackstand miles. /ubbthreads/images/graemlins/hsugh.gif

 

[Brianawd]

Quote:
Hey Brian, how many miles did you put on your car this year? Not including jackstand miles.



Under 600. It was a good year /ubbthreads/images/graemlins/frown.gif

 

[turbowop]

/ubbthreads/images/graemlins/rofl.gif

/ubbthreads/images/graemlins/frown.gif

 

So am I going to hate a center spool? Let's say I go to the DSM 1st gear, but leave the center diff alone what (if any) is a "safe" launch rpm? Now what about with the DSM 1st and a center spool? Again, the car won't be drag raced, but it'd be nice to launch a bit at the AutoX or from a stoplight.

Thanks,

TJ

 

[turbowop]

For what it's worth, I have a lot of timeslips that show 1.7x 60' times, as well as a few 1.68's, all done with a stock center diff and a gvr4 first gear. Hell, I even did those with the stock 3bolt rear end. /ubbthreads/images/graemlins/dunno.gif

Launch RPM differs with changing track conditions, which is why ideally it should be adjustable. If you're not going to be drag racing it, I wouldn't worry too much. If you go out and do a bunch of launches on a well prepped track, however, there's a higher chance of breakage.

 

[bazeng]

Turbowop,

I've got 2 VR4 RS gearbox's mate...
Did you want me to send you one?

I believe they have all the goodies of the evo box's...

 

[scooter]

I originally thought the rs gear boxes were the same as the evo III also, but I think after talking with John that I learned different. Im pretty sure the gears go as follows.

Gvr4rs evoIII
1st 2.571 2.750
2nd 1.600 1.684
3rd 1.160 1.160
4th 0.862 0.862
5th 0.617 0.617

The third and fourth might be the same pieces, but first and second are not. Even being close, John told me the 2.57 was not all that good. I was assuming he meant not as strong as the real evoIII piece. I would also like to know any of the other pieces that are the same, as in forks or whatever. See if its really all its cracked up to be, or just some different gears.

Ive had the rs tranny in my dsm for awhile. I never had a problem with it, just thought it was interesting it wasnt what I always thought it was. Ive went a 1.69 60 foot on the 2.57 first, but it for sure takes some getting use too. To get the same 60's as with the 1g first, the clutch life would be almost non existent. An act disc would last about 1000 miles with hard abuse. This was with a fp red, so you had to really slip the clutch to not bog. I still think they are great trannies, just wanted to throw what ive learned out there. Anybody else with info on the tranny would be great.

EDIT: I spaced the gear sets apart, but it always went back to that.

 

[gtluke]

the evo gearboxes have the steel shift forks and the evo3 has a LSD front
i have an rs box in my car with an evo rear end for the complete package. its AWESOME. its such a thrill to drive with the short geared close ratio transmission. it pulls HARD and is really fun.
I have a 4 spider diff in there that bean at turbotrix did for me.
safe launch = load the drivetrain up before applying full power.
slip the clutch just for a moment. don't slam the clutch, the jolt and wheelhop is what breaks sh*t, not raw power (until a point)
my friend brent put a rally style handbrake in his car so he can easily load the car up on the brakes while he slips the clutch to avoid hitting the drivetrain too hard. helps build boost too.

 

[H05TYL]

Not every Evo3 box has an lsd front diff, it was an option on all evo's, and they are pretty rare.

The only guaranteed safe option is not to launch the car.

I tend to launch the car off the rev-limiter, the wheelspin doesn't make alot of difference to 60' times, but when the wheels are spinning there's less resistance so your less likely to break anything.

Welding the centre diff is cheap insurance, but not ideal for auto-X, although if your competing for fun, rather than going all out to win, you can always do it in rwd and have an absolute ball!

do US spec vr4's have different first gears to JDM ones? I've never heard of anyone breaking one - it's usually stock centre diffs, shift forks, or 3rd gear in big hp cars (620awhp 10sec cars).

Alloy transfer cases are pretty weak too.

and of course 3 bolt axles.

The thing to remember is anything that fails inside the gearbox is likely to make a mess of everything else in the 'box, and probably a nice hole in the casing as well.

 

[3rdstrikedsm]

Launch off the factory 2-step (revlimit) and slip a good clutch and you should be ok for a while as the spin takes a little of the load off the drivetrain. Poly or solid mounts will also help loads to control wheel hop.

 

I launched 5500-6000 RPM on the stock transmission at autocrosses run after run for season after season. Shepherd rebuilt the transmission using the original stock 1st gear at my request because I like ratio. But that was also when Jeremy built my 2.3. After that, that stock 1st gear lasted not even one season. Needless to say the replacement was a DSM gear although it is a bit short for my taste, also an upgraded center diff. Live, spend, and learn.
Mike R.

 

[gtluke]

oh cool thanks for the tip on the lsd evo transmissions, I was wondering which ones got it. Didn't know it was an option.

 

When I had my 16g and 14b I launched at 4500 slipping the clutch some. with my 35r I have to launch at 5750 (with 2step) and I still slip the clutch some. after over a dozen launches like that (with zero wheel spin) on a stage 2 tre, 2600 street disk, stock 3 bolt and tcase I am confident I will not break anything. I'm not launching slow either. If you are really scared of breaking stuff, just know that you should only put your launch rpm as high as is needed to not bog, and since you are not just dumping the clutch but rather slipping it, your launch rpm is much lower. preloading with the e-brake also takes a massive strain off the drivetrain. I worry more about second gear breaking than anything, and I still doont worry about that much with my No lift to shift. (I really like DSMlink /ubbthreads/images/graemlins/smile.gif)

 

[bustedsm]

On a stock 22 spline trans and case and stock 3 bolt I beat the living SNOT out of the car. 22lbs off the line with an ACT 2600 6-puck (sprung) I had no problems. Only thing I had problems with was the axle boots...they just ripped like butter /ubbthreads/images/graemlins/frown.gif