I have a G-Tech Pro, and have run my old Crossfire and my new SRT with it. I also drive a Mazda 3 as a daily driver. Here are my times (all at around 50 degrees F):

2004 Crossfire> 14.81 sec @ 95 mph *** 60 foot = 2.31 sec *** 0 - 60 mph = 6.54 sec
2005 SRT------>13.14 sec @108 mph *** 60 foot = 2.19 sec *** 0 - 60 mph = 4.66 sec
2004 Mazda 3-> 16.69 sec @ 86 mph *** 60 foot = 2.71 sec *** 0 - 60 mph = 8.54 sec

My 2004 had the Upsolute Chip and Borla exhaust. SRT and Mazda are stock.

This is at 1,100 feet of altitude in Phoenix...if you correct these to sea-level, the 1/4 mile times will drop right at 0.2 tenths. That means my SRT ran about a 13.0, and the other Crossfire a 14.6, and the Mazda3 a 16.5.

The Gtech is pretty accurate, but depending on how you set it up (rollout and pitch factor), it can be a bit different than an actual 1/4 mile run. I set the rollout in the middle of the range (8 inches), and the pitch stock at 2 degrees.

My initial thought was that a 13.0 is too fast for an SRT, but I ran the Mazda3 and the SRT on the same night within an hour of each other. The reason why that is significant is because that the Mazda3 is said to run a 16.0 at 87 (C&D), and I ran a 16.6, so that would mean the Gtech is slow, not fast. Also, the non-SRT Crossfire ran a 14.6, which is right where it should be with the upgrades that I did. Also, the MPH numbers all were within 1 MPH of where I expected them to be.

I know these numbers from the Gtech aren't carved in stone and can be debated, but I do believe they are accurate to probably within 2/10's.

 

Is the Mazda a manual transmission? If so, maybe the guy from C&D could of just shifted faster, or they got a better launch, etc...

 

I can run consistent 13.0's in the SRT-6. Two trips ago to the strip I put down 4 13.0's in a row. Went to the strip a couple of weeks ago and was hoping to break into the 12's but track and weather conditions did not cooperate.

BTW I am stock (unless you want to count the SL55 y-pipe as a modification).

 

That's pretty impressive for stock. What are your tires, and how old are they (mileage)? Have you had problems hooking up & if so, what might help at launch?

 

I think people have broken into the 12's in stock srt-6's, not here, but i've heard of it...

 

I have hit 13.0's on the stock tires. They had ~19k miles on them at the time and only had a couple thousand miles of life left.

Traction is an issue. The keys to a good run are track prep, weather, and launch technique. You can not slam the throttle open, you have to squeeze it. You will also need to brake torque to build up enough revs for a launch but be careful not to launch too aggressively or you will just spin.

 

SRT6_Roadster...At what rpm level did you load the tranny before letting off the gas to get those 13.0 sec quarter mile times?

 

I am trying to remeber I think my best launch as been barely loading the trans in the 700-800rpm range. Some people have claimed better times loading up to ~1200 rpm but the couple of times I tried it my times were not as good as they should have been. Although both weather and track conditions were not what I would have liked so I do not know if it was the rpm or other conditions conspiring to keep me out of the 12's.

 

I have a traction issue as well. I have to modulate the throttle most of the way through first gear, only flooring it after about 3/4ths the way through the gear. I also found out that loading the engine at about 1,000 rpm then slowly depressing it all the way to the floor gives the best result.

I ran it through the Gtech a few more times with a few different pitch factors (the pitch factor takes into account the rise of the front end of the car: the more the car pitches, the more the Gtech is fooled into thinking the extra G force that the rising front end is actually acceleration, resulting in a time that is faster than reality). The outside air temp was 48 degrees (it snowed just outside Phoenix this weekend!) and Phoenix is 1,100 ft, so take off 0.2 sec from all of these numbers for the sea level correction.

2 degrees (stock setting)
13.099s @ 108.46 mph
13.235s @ 108.56 mph
13.306s @ 107.45 mph

3 degrees
13.672s @ 106.13 mph

4 degrees
13.695s @ 103.35 mph
13.734s @ 104.17 mph

Which is right? I don't know. Car and Driver reported a 13.5s at 107 mph.

I do know that I am losing a few tenths trying to get the car to hook up in first!

 

Stock tires being Michelin PS2s?

Some cars, including mine, came with Conti all season performance tires, which seem to have inferior traction even though they cost extra.

 

The pitch on a non-SRT6 XF is quite dramatic - hard to figure in degrees and even harder to measure, I suppose one way is from outside the car with a high speed camera?

Stiffer springs on the SRT6 probably limit pitch?

 

Good point. I think you are right in that the lighter springs give more pitch by unloading when the weight transfers to the back on takeoff...I think bracket racers and other 1/4 mile junkies take advantage of that.

I think leaving the pitch at 2 degrees is about right...my times line up pretty good with reported numbers, although mine might be a bit fast. The 3 and 4 degree settings gave me numbers that seem too slow to me, so the 2 degree number is probably about right.

Another factor that comes into big play is the "rollout". It is a number in inches that represent how far the car rolls before the timer is started. This is to simulate where in the staging at a dragstrip your car is when you lineup to stage. It can be set in the Gtech from 0 to 16 inches. The difference in ET's of using 0 vs 16 inches in a car that runs in the 13-14 second range is about 0.45 seconds (from the Gtech manual). I have the Gtech set to the midrange value of 8 inches. According to the manual, if I had set it to 0, you would have to add 0.3 seconds to my times, and if I had set it to 16 inches, you would have to subtract about 0.2 seconds off my times.

Point being is that with the Gtech, it really is an estimation of what the 1/4 mile times really are. And even if you go to a track, unless you stage the exact same way each time, your times typically vary about 0.2 seconds through each run. So even at a track, it is not a simple number. There are just so many variables going into it.

I am going to stick to saying the SRT6 is a 13.5 to 13.2 second, 106-108 mph car on the street tires. With slicks, it most likely dips into the 12's.

 

When your running the 1/4 mile, are you guys leaving it in drive or are you shifting manually? Does anyone have an opinion on where the tank should be, 1/4 tank for less weight or near full for maybe some extra traction? I've been thinking about going to the local track one night and seeing what it'll do.
Thanks, John

 

Just leave it in drive.

The less gas in the tank the better.

 

I just purchased my first Xf. It's a 2004 with now 17,000 miles.
Love every mile of it. I now need to get the lead out <grin>.

Where do I find information about high performance options?
You mentioned the GTech Chip... What is this and are there ways to program or control the on-board performance computers?

Who are the vendors for performance items?

Thanks,
Tim Crammer

 

Hey ... Sorry about that. I'm new to the forum and found several suggestions on performance.

Still any advice is appreciated!

Tim