Stock '08 IS350. Removed the spare..here are a few questions regarding what it takes to get the best 1/4 mile times:

1) Power switch on/off?
2) Sport shift or automatic?
3) Slam gas and let it rip or hold break and rev engine to some rpm?
4) Any other tips?

Also, what kind of times can I expect?

 

Oh well here's a couple tips and to answer your questions.

Make sure you remove ALL unnecessary weight as you did with the spare. Remove the tools too while you're at it. Definately leave the powerswitch on as you'll get better response. Also I'd recommend you to use automatic as the timing of the shifts on WOT are very precise and quick and sport shifting might cause a mess up if you shift too late or early unless you're REALLY good at it. Also definately hold your brakes and rev to get off the line quicker.

Also something you should do is raise the PSI of your tires. If anything at least make sure they're properly inflated. This'll give you less rolling resistance which means better times. You should expect mid to low 13's for a time. Good luck! Be safe! And most importantly HAVE FUN!!!

 

put in sport and shift up to 6th so it will sport shift till 6th, windows and sunroof closed a/c off all electronics off, idk about the break stand you might just spin you wheals in place and loose time

 

Power button *off*, ect pwr holds the gears longer than is desirable
No reason to have it in sport mode, at best you're going to shift just as perfectly as the cpu, the cpu knows straight lines pretty well.

As for brake torquing, I'm not sure, I haven't seen people posting gains from it I definitely wouldn't go past 1500 rpm's personally.

Edit: also, against what a previous poster said, lower the PSI on the rears a few pounds from recommended, raising the fronts by a few pounds is sound advice though.

 

thanks guys, i'll let you all know how it went and put up some times.

 

Yup... ECT power -off- is faster, Gernby has measured and datalogged this to prove it.

The computer shifts better than you do, leave it in drive, or if you want to be paranoid you can put it in S-4...in which case it'll automatically shift up through 4 and avoid using any overdrive gears which'd slow you down. Shifting yourself will significantly slow you.

Brake torque, as mentioned I don't think I'd go much past 1500 or so...

One thing nobody mentioned- have TRAC/VSC off, not doing so will reduce power on launch.

And yes, -lower- pressure in the rear tires, higher pressure on the fronts, means better weight transfer too. When I used to drag (in a different, significantly more powerful, RWD car) I ran 40 psi on my front street tires and 15-20 psi on my rear drag radials for best times

 

Nice info on this. Im not 100% sure, but i think front psi should be around 40 (max tire spec) and rear tire psi somewhere in low to mid 30's.
I tried 30psi one time and that felt a little too low. As far as I know the RPM's whenever you launch should not bog or stop. at 30 psi they kinda bogged a lil bit. I think the IS needs a liiitle bit of spin to get better jumps.

 

will turning the trac/vcs off make my tires spin at launch? if so, won't that hurt my times?

i'm a bit nervous to reduce my rear tires PSI by that much. how much of a difference are we talking about in terms of improvement on the 1/4 mile time? also, what is the reason for more in the front and less air in the back tires?

 

You'll have to play with the launch, depending on both the traction of your tires and how sticky the track is.

If you're getting a bunch of wheelspin on launch by torquing to 1500 then don't do that (or get stickier tires)

higher PSI on front wheels for example help with both rolling resistance and weight transfer

Lower PSI on the rear give you a better contact patch for more traction... Here's one tip on finding the right pressure I've seen-

You should lay a nice smoky burnout (in a parking lot or somewhere open) and then observe the marks left behind. If they are darkest on the edges then you could use a little more air. If the middle is darker then you should let some air out. You will have the correct air pressure when you see an even black mark.

 

Hahaha - This is a funny thread with sooooo many opinions. My opinions are below.

Weight Reduction - Remove as much as possible - Spare, Jack, Tool Kit, Spare cover, First aid kit, cargo net, Floor mats, Owners manual, Other junk, Engine bay covers (except for the very front one) & you could even remove the head rests with the exception of the driver seat which would not be safe.

Make sure you have less the 1/4 of gas.

Resistance - The FM state that you can add ~7psi above the stock rating if you plan on doing high speed driving. You could also inflate the tires to its cold max that is printed on the side wall. The reason for having a lower tire pressure for the rear is so that you can get better traction at the line. You will have to just experiment with this in combination with a brake torque method. Close all windows.

Keep the A/C off. Even in the pits. the A/C could leak water condensation onto the track so it is just a courtesy to the others at the track.

The transmission should be in the normal auto mode for best results.

Turn traction control off so that you can induce a small bit of wheel spin when launching. The added momentum seems to help 60' times etc...

You could even try folding your outside mirror back so they catch less wind.

Typically you are required to race with a helmet if you break into the 13's.

 

Another tip- Assuming you're using street tires-

avoid the waterbox

Don't bother with a huge burnout, you'll just waste rubber. Do a bit of one to clean the tires off and you'll be fine.

Now, if you've got drag radials or something better feel free to do your best John Force impression to heat em up.

 

do i just hit the traction control button to turn it off, or hold it for 3-4 seconds like i've read in other threads?

 

Hold it down till both the Trac and VSC lights come on on the dash, should be a few seconds

 

i know a dumb question, but what is the diff b/w trac and vsc?

 

a rough idea is in my experience: traction contrllets you spin the wheels if you are going straight but as soon as you go a little sideways the VSC cuts the power off. so the VSC lets you spin no matter which direction you are going. hehe