Hello
preparing for my first drag race contest in my standard 2002 XJR, wanted to ask for advices on tires/launch tips!

Will be using street tires Pirelli P Zero. As far is I got now at 22 PSI pressure without any burnout/tire warming the pedal to the floor will not launch the car good as on my previous 4wd car . Iam practicing the smooth start however and trying to do it without any slip in 1st, Iam doing not bad at all but feel that it should be better!!! any advice on improvements to be done are appreciated. The event is just friendly drag contest, but still I'd like to get the best times possible and make some sport coupes shy

1. What tire pressure best for drag?
2. ASC on or off?
3. warm/burnout tires, yes or no?
4. any other tips?

 

1. Keep pressure about normal, around 30 psi or so. Street tires aren't built to take advantage of lower pressures like dedicated drag tires. Drag tires are built to have much less sidewall stiffness so that the sidewall can flex and allow the treadface to "bell" under load without adverse changes in geometry. The stiffer sidewall of a street tire won't compress as readily, so they usually fold inward under load when under inflated, cupping the center of the treadface away from the pavement and actually reducing grip.

2. ASC most definitely off. You're absolutely going to see some spin, and the ASC is way too aggressive in cutting power, it WILL make you slower.

3. No burnout. The compound of rubber that street tires are formed of operate best at normal temperatures. They aren't formulated to take advantage of excess heat like drag tires or road-racing slicks. Just avoid the burnout box entirely, you don't want your tires wet either. The only reason to do a burnout is because it looks cool

4. Make triple sure you're in sport mode! This enables first gear for launch, which launches MUCH harder.

Unfortunately, getting a good launch out of an XJR is down to luck. With no limited slip, it's either you get lucky and it hooks, or it blows off one tire for days. I've had the best luck with running it up to about 2000 rpm against the brakes at around 40% throttle, releasing the brakes, and after a tiny rollout at around 60% throttle to try and let it get some grip, going to full throttle. This usually yields consistently good results unless I blow off the tires. If this car just had some better gears and a posi, it'd be an absolute animal at the strip.

 

Do you have any power adding modifications on the car?

 

Hi Parwun,

Here's a tip that may potentially improve your times:

I don't know if this is true on an X308, but on an XJ40 if you remove the J-gate upper trim you can actually select 1st gear with the lever and run all the way to redline before you upshift.

If this works on your X308, you'll want to practice your shifts so you don't accidentally miss 2nd and shift from 1st to 3rd.

Let us know how it goes. Sounds like fun!

Cheers,

Don

 

no mods for now yet

 

thx for that, never tried to start from higher rpms holding the brake pedal, will try it out later, goddamn! its snowy and cold again for a week or so.

 

With no mods, I ran exactly the same time and mph at the 1/4 mile track. I ran 2 times, once with traction control and once without.

 

My experience was on a, let's say....indifferently prepped track on high performance street tires. If it gripped off the line, traction control was irrelevant. But if I got some spin, ASC would jump in and absolutely make the car fall on its face, whereas with ASC off, it would just spin some and not completely blow the run. I definitely think TC off is the safer bet if you're used to dealing with some wheel spin off the line.

 

What were the times?

I think I remember seeing some times somewhere, you should be aiming for around a 14 flat, possibly dipping into the 13's if you're lucky/have a grippy track.

When I took my old X300 XJR to the drag strip I found doing a burnout helpful, as it gets the temps back up after sitting around doing nothing between the rounds. Of course, if you're running reasonably often you might find the tyres stay sufficiently warm.

It's also great fun reminding people that these big cats know how to smoke it up

 

I think it was 13.82 and 13.84, then it dropped to 13.23 after adding a few mods.

 

Little update on the topic...

About launch trainings:
I've spent plenty of time trying to polish my launching skills to avoid wheel slip and I came to a simple conclusion: the road is the main factor, 95% of streets and parking lots gave results of huge slip when gas pedal smashed to the floor instantly, however I've found 1 supermarket parking in the city that gave a superb traction! also the last day I went to a highway and the traction was great, absolutely no slip again! the launch is in the road not the tires

However going to 1/4 mile event I relaxed and was oriented to check the traction when I arrive. The result was good, from 4 tries I've made- I only had a small spin once. I've also found that small burnout is helpful to cleanup and little warm up the tires.

Here are the results: 1/4mile time/speed
13.7547 165.5
13.9438 164.7
14.0478 164.4
14.1758 164.5

Pleased with the first result 13.755 seems good to me , achieved in very 1st recorded time run of the event coz smarter boyz arrive early times get worse when cooling in 1 to 3 hour lines to get your turn again

Videos can be found here


Plenty of things to polish still.

1. Reaction time:
Mine was terrible 0.63 to 0.78 three times, and the last run I got 1.1 after some self adjustments been made, due to no experience I've started acting on green light, the last try I did the footwork on last yellow- moving foot from brake to gas, gas pedal actions, drivetrain...all takes time so must be done earlier or Iam thinking here of using both feet next time...something like Cabezagrande said before.... any recommendations?

2. Throttle response:
However even if the road gave a nice traction and I could just smash the pedal to the floor I felt like there is a delay in acceleration at the launch in some of my tries, also the times are worse, what I'am thinking here now that instant flooring aint the way- a little lag appear, some smoother acting required on maybe working both feet will somehow help here? or maybe its a technical problem?

3. Getting to 13.5
The idea is simple- do the upgrade to the Cat to be closer to 13.5 1/4 time. there is a local championship this year with 4 stages of 1/4mile. I'am registering to ''street A'' class- cars not faster that 13.5- mostly to have fun, but why not the win? . The main idea is the lower pulley upgrade for now, any thoughts or experience how much will it cut from lets say 13.8??? I'am also fitting lowering springs soonish as required repairs.

cheers

 

If you add a +4 lower, also, for a mere $30, you can add this in front of the inter cooler radiator: Radiator Cooling Fan

This makes a HUGE difference!

As to timing the launch for better reaction times. Use both feet, one brake, one gas. Try leaving on the last yellow before the green. I've been able to cut times as close as +/- .05. On this video, I red lighted with -.06, but it was a tuning session so there was no disqualification, I was just sticking it to the loud firechicken in the next lane who was giving looks of over confidence. He wouldn't even look at me the rest of the day. Here is that video where I ran a 13.23