3dog

iTrader: (1)

Do you have a V8?

Your profile shows an IS 300.

That might explain the slow times.


3dog

Lvangundy

Yes sir, 2001 GS430. 46K miles.

I also have an IS300 I'm trying to sell.

bitkahuna

iTrader: (20)

Maybe your G-Tech is fubar'ed?

bitkahuna

iTrader: (20)

Even if it turns out that the 3.76 gearing is not optimal for 0-60 sprints, in real world driving it keeps the car in the stronger part of the torque curve more often, and the lowered gearing means more 'twist' at the axles (at the expense of top speed). Plus, and this was absolutely huge for me, the VSC rarely kicks in. With the stock open diff, and particularly if you have the upgraded Precision (Dragon) TC, when turning right or left from a stop even with mild throttle, VSC wil engage, which can even be downright dangerous as your car is bogging and the car coming along the road you turned onto is barrelling toward you - this happened a bunch of times for me leaving where I used to work which had a parking lot that exited onto a highway access road. I got the Supra diff., and had a grin from ear to ear every time I left work after that. Not a peep from VSC as I ripped out of the parking lot making the 90 degree right turn onto the access road.

JBrady

Bingo. Zero to sixty is only a benchmark. Racing the clock is fun and interesting but when racing another car it is the PULL that matters.

I am jealous of you GS4xx guys. I am not certain but am not convinced that on my LS400 the car speedometer and odometer will be compensated like the GS4xx does.

FutureGS400

John, are you saying that a gear swap would throw off your speedo and odometer?
Bitkahuna's experience mirrors mine exactly-only on rare occasions does VSC kick in.
I feel that 0-100 is a more meaningful measurement of a car's capability. Lack of traction not as big of a factor; of course it's a little more difficult to do unless you're at the track...

JBrady

Yeah, I do not know if changing gears will change my LS400 speedo/odo readings. Honestly, I am surprised that the GS4xx compensates. Virtually every car I have ever worked on required a recalibration following a gearing change. My LS may or may not need it. I actually had what was SUPPOSED to be a Supra lsd 3.769 assembly. It was out of a 98 and the owner was POSITIVE it was a torsen. I opened it and it was not. Took me a month of pictures and emails to get him to take it back. Now I wish he had just given me a discount and I would have tried it.

Oh, well, maybe later.

Lvangundy

Yes, I do agree. The power band is much more accessible for those quick bursts. Especially at higher speeds.

I guess I should be looking at something other than the 0-60 time.

Bit, the VSC definetly stays off a lot more now. Also, the extra control you get from the LSD is amazing.

Are we sure the 3.76 doens't offset the tach and odometer? I can't see why it would not mess it up.

FutureGS400

It has to do with the way our cars read the speed and distance (wheel sensors I believe). Changing wheel/tire diameter will affect speedo and odometer reads however-for example going to 20s. Not a big change from what I've heard...
I have dealt with this issue on past vehicles on which I've done gear swaps (4x4 trucks) and had to change the speedo drive gear that comes off the trans.

Shogun

Gents,
There's a software program out there called "car test" that dials in all the parameters for a car (weight, wheel size, horsepower, torque, frontal mass, aerodynamics, gears, final drive, etc. and then runs simulated speed tests

This thing is really a slick piece of software. It comes loaded with 100s of cars in the database and the thing is - the test results are dead-nuts-on to what the magazines report.

Anyway, here's the deal...

You load in the 3.76 and then "race it" against stock and the software reports that the gears are not optimized for 0-60 or top end. I'll find a link for the software later tonight and post - it was free when I downloaded it.

It'll also show torque and Hp curves and let's you race up 5 cars against one another. Finally, it'll run an optimization test to let you know the best launch technique/rpm.

At a minimum, it helps you to understand how the gears interact with our engine specs and wheel sizes.

Eric

DrewGS4

Sounds like a really good program....looking forward trying it out.
Post up the link when you find it

bitkahuna

iTrader: (20)

It's not that the GS compensates, it just doesn't judge speed from the driveshaft or diff output shafts at all - it uses wheel speed sensors. Now changing rim/tire diameter DOES throw off the speedo/odo (and the nav, but this can be adjusted through a service screen).

Shogun

OK - there are two versions of the Car Test Program...

1> An Older DOS version (Free): http://www.cartestsoftware.com/cartest4.5/index.html

2> A Windows version (30 day Trial): http://www.cartestsoftware.com/cartest2000/index.html

FWIW, both programs accomplish the same thing...

While nothing approaches real-world results, from a theoretical/technical standpoint the program does a good job of showing how changes affect performance based on the car's specs.

"CarTest is an automobile maximum acceleration computer simulation. The user enters the specifications for an automobile and CarTest will mathematically accelerate the car from a standing or rolling start until maximum speed is reached. The simulation is time-based and event-driven. That is, the acceleration times are not explicitly calculated but, rather, time progresses at small increments and the usual events that take place during acceleration: clutch dump, wheelspin, shifting, etc. happen in proper course. The acceleration times are arbitrary milestones that are reached during the car's response to these events."

It has 877 cars to choose from. However, you can modify ANY of these to match your car in terms of HP, torque, gearing, tire width, etc. You can do drag races with up to six cars, get lap times for 50 World famous tracks, or just look at power/time charts. It is so cool you won't believe it!!!!! When you download it, you will get several items, the program itself is labeled as CT, it is a DOS program. Just follow the instructions from there.

cartechpr

can someone please verify how the ls400 judges (98) VSS.... as i have been looking into the diagrams and service stuff.. they both have a transmission VSS.... SO i guess the LS judges the same way....