So this weekend i swapped to a 3.3VLSD since i had to drop mine to replace a broken Diff mount stud. And i know that this swap has been debated on at what power level you should consider this swap so i figured i would post my results. Last Sunday i was at the Dragstrip with my 3.5VSLD, had all day and got plenty of runs. After finishing the swap this Sunday i went back for the last hour of test and tune.

Here are my results,(all on street tires) im posting multiple runs to show what i consistantly ran, on the 3.5 i was pretty consistent at ~12.6 but i had one great run and ran a 12.42
*RIGHT LANE*






With the 3.3VLSD installed i still had the same wheel hop issues at before and didnt have as many runs to get a perfect launch (without hop) but here are the results




Here are some pics from the install





Conditions were nearly identical between the 2 days, so based on just the timeslips it appears the 3.3 slowed me down with 484rwhp/440ft-lb. But i honestly thing i just didn't have enough time to get the launch right, you can see that based on the 60fts, or maybe the 3.3 hurt my 60s. The car feels quicker especially in the seemingly never-ending 4th gear. I wanted to post this info to see what everyone has to say and to possibly help people make the decision of when to do this swap.

Rob

 

You are allowed to circle your car number on the time slip for easy reference.

I give you a thumbsup for running 400 plus horsepower on street times. 1.9 seconds is good.

 

Sorry didnt do that, but i was always in the right lane

 

Nice! Thanks for the comparison. I'd do the swap if it didn't kill cruise control, that's my favorite OEM part lol.

 

It doesn't, Cruise Control and VDC are still 100% functional, trust me thats the first thing i confirmed after the install

edit: the light is out of view in that pic but i was actually on cruise control when i took that

 

did you see an improvement in traction in earlier gears???

 

On the street there is a noticeable improvement in traction in first gear.I hardly even spin in 1st now. (warm day)

 

your traps dont seem high enough for said power levels. im right around 480whp on forged's dyno and im trapping 125mph.

 

+1 on my low boost at 470 whp i trapped at 124 ^

 

i have another thread about my surging problem, i believe im going to have to switch to a MAP based EMS because the car falls on its face between shifts. But as far as a comparison goes for the gears the surging was unchanged between the runs.

 

With the 3.5 were you shifting in 5th? Same queston for the 3.3FD?

The big advantage for most is the ability to stay in 4th with the 3.3 and avoid a shift after 113mph or so.

If you run a large rear tire like say a 285/295/35 then you are already effectively elongating the gearing, so combine that with the fact you are a litte under somebody who truly needs a 3.3FD power wise IMO, and the result of you being slightly slower is right on. When I made the change my car "only" made 525whp/490ft/lbs at low boost and that seemed like JUST enough to not feel slower and be slower as I compared to several vehicles.

On the street though, where you used to spin in 2nd, now you wont. And thats worth more than the 1mph you seemingly lost the back half of the track.

You arent launching as well with the 3.3FD though so if you did the traps will go back up. As it seems now the car isnt quite hitting its sweet spot in 4th yet, as can be seen by the back half numbers below.

3.5 FD

26.4mph

26.3mph

26.2mph

3.3 FD

25.4mph

25.2mph

Shift slightly higher in the rev range next time with the new gears (especially 1st and 2nd gear), that will help overall. Where is your rev limiter?

**For all the people chiming in with what you trapped, you also have to share your 60ft and 1/4 ET, as anybody can spin to a high trap and $hit time.

 

Im running a 295/35R19 rear so i had that advantage but with the 3.5 i was hitting the limiter in 4th (7k) crossing the line almost everytime.

I realize i probably didn't NEED longer gearing right now, but i was dropping the diff anyway, will be building a block in the near future and figured if i throw DRs on it the gears will keep me from having to shift into 5th.

I know that i need to stretch out my gears more by shifting higher but my RPM gauge is off just enough to make that tricky, and since i am stock block i try to stay off the limiter as much as possible. I consistently shift at 6750 (via logs) except 1st when im spinning or hopping.

With the 3.3 when i cross the line i feel like i have alot left, before it would start to fall off right before the line, now it feels like i'm in peak TQ (not sure @what rpm i cross the line now)

Those back half numbers are interesting, never thought of comparing those.

I'm hoping to get the surging problem resolved, fix the wheel hop and make it back out at least one more time before i build it.

 

wouldn't more people have compressor surge on the aps tt kits if it were a huge problem? not saying you aren't getting some but just wondering if it's actually compressor surge ur seeing.

i trapped 121mph and ran 11.8 with a 1.8 60' on an aps st making 425whp on grd's dyno...keeping that thing spooled in between gears would be more difficult than the smaller twins i'd imagine...

 

well i call it surge but i think we have decided its something with the EMS, its pulling timing back to -7* for a couple seconds after shifts, it looks like the MAF is getting crazy readings due to the BOV being right next to it and quick spool right after the shift. So it looks like im going to have to switch to something MAP based.

edit: was your run on street tires?
I didnt intend for this thread to become a d*ck measuring contest, i know my car isn't to its full potential for the power, this thread was just for the sake of a before and after the gears.

 

what ems are you running, the unichip that comes with the aps kits?

i certainly didn't take this thread as a "who has a bigger *******" thread at all. i think the others in here, as well as i, were just trying to toss in something to compare your times and hp with.

that run was on an 18" bfg drad radial.

 

Im on Osiris (Pmas) now, it did the same thing on the unchip but not as bad or as often. Boost level doesnt affect it, it does the same at 10psi as at 8psi. The only thing that affects it is IAT, when its below 70* outside it stutters terribly, and gets worse the colder it is. But when IATs are hot, or in a 3-4th shift it hardly stutters if any. We have tried several different things with the tune with no improvement. It does fine on the dyno, its only during a sudden change in flow. In the cold it even does it when going WOT in gear from a roll.

 

1/8 was 97 mph and 0-60ft was 1.9

 

What was the ET? Tires?

 

11.7 on 295 street tires

 

Awesome! But wasn't Alberto's and others' cruise control not working after the swap? Supposedly it was the mph not agreeing with the expected rpm. Is there a Difference between the g and the z? I really have got to find out because if so I'll be in the market for a 3.3.