XR A box testing/tweaking on K03s (long) - FATS time 4.2
04-04-2005, 01:54 PM
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XR A box testing/tweaking on K03s (long) - FATS time 4.2
My favorite street chip for the A box is the AMS, but I got my hands on an A box XR chip to try out with 100 octane.
<b>General Observation</b>
This A box XR chip is very different than the XR I had for my 2001 (in a good way). No overboosting/surging, no throttle cut, no hesitations. It is VERY smooth - hits 19-20psi and holds steady, even in the lower rpm / high gears (before gradually tapering to ~14-15psi by redline). No cutting. This is even in contrast to the A box X chip I had where boost frequently surged in higher gears.
<b>Fueling</b>
The A box XR has more preferable fueling and air/fuel ratio (IMO) than the 2001 X/XR chips. I had suspected this based on the Atlanta dyno day results (search archives) where RobC's A box XR had dynoed air/fuel ratios in a more ideal 11:1-12:1 range, whereas both other 2001 X chips on the same day were quite rich (10:1). We've logged injector times before on GIAC 2001s and they are very high - reaching over 100% duty cycle well before MAF airflow is at peak. Here's a 2001 XR as an example (X also peaks in the 30's ms):
<img src="http://pictureposter.audiworld.com/16111/max_inj.jpg">
Here are the injector times from this A box XR, which as you can see are much lower for similar airflow values, and even dip below 20ms as you approach redline.
<img src="http://pictureposter.audiworld.com/16111/xr2.jpg">
I logged O2 voltages and they were right in the 0.85v range. So I didn't think any fueling tweaks were necessary.
<b>Timing:</b>
The XR A box timing program is aggressive as expected, but I noticed in the low-mid range I was not seeing knock correction on some cylinders even on 100 octane. I added 3 degrees of timing in lemmiwinks. Here is both timing and MAF logged for my FATS run after the lemmiwinks changes. Up top the changes didn't matter since there was already knock correction, but notice I'm already over <b>20 deg advance at around 4000rpm</b> - which is extraordinary at that rpm based on other K03s logs I've seen. I believe this added extra mid-range torque which helped my FATS time in the early part of the RPMs. Also as expected I saw a nice airflow increase especially in the 4200-5500 range. The Bosch MAF logs typically lower g/sec values than Hitachi in my experience, so approaching 270 g/sec by 5000rpm was pretty darn good compared to other A box K03 logs I have.
<img src="http://pictureposter.audiworld.com/16111/xr1.jpg">
FATS time was 4.2 (which was actually 2 runs averaged both ways). Weather was 41 degrees F, and other mods include milltek superdual, airbox hole, new stock filter, de-screened Bosch MAF, lightweight wheels and battery, no spare.
<b>General Observation</b>
This A box XR chip is very different than the XR I had for my 2001 (in a good way). No overboosting/surging, no throttle cut, no hesitations. It is VERY smooth - hits 19-20psi and holds steady, even in the lower rpm / high gears (before gradually tapering to ~14-15psi by redline). No cutting. This is even in contrast to the A box X chip I had where boost frequently surged in higher gears.
<b>Fueling</b>
The A box XR has more preferable fueling and air/fuel ratio (IMO) than the 2001 X/XR chips. I had suspected this based on the Atlanta dyno day results (search archives) where RobC's A box XR had dynoed air/fuel ratios in a more ideal 11:1-12:1 range, whereas both other 2001 X chips on the same day were quite rich (10:1). We've logged injector times before on GIAC 2001s and they are very high - reaching over 100% duty cycle well before MAF airflow is at peak. Here's a 2001 XR as an example (X also peaks in the 30's ms):
<img src="http://pictureposter.audiworld.com/16111/max_inj.jpg">
Here are the injector times from this A box XR, which as you can see are much lower for similar airflow values, and even dip below 20ms as you approach redline.
<img src="http://pictureposter.audiworld.com/16111/xr2.jpg">
I logged O2 voltages and they were right in the 0.85v range. So I didn't think any fueling tweaks were necessary.
<b>Timing:</b>
The XR A box timing program is aggressive as expected, but I noticed in the low-mid range I was not seeing knock correction on some cylinders even on 100 octane. I added 3 degrees of timing in lemmiwinks. Here is both timing and MAF logged for my FATS run after the lemmiwinks changes. Up top the changes didn't matter since there was already knock correction, but notice I'm already over <b>20 deg advance at around 4000rpm</b> - which is extraordinary at that rpm based on other K03s logs I've seen. I believe this added extra mid-range torque which helped my FATS time in the early part of the RPMs. Also as expected I saw a nice airflow increase especially in the 4200-5500 range. The Bosch MAF logs typically lower g/sec values than Hitachi in my experience, so approaching 270 g/sec by 5000rpm was pretty darn good compared to other A box K03 logs I have.
<img src="http://pictureposter.audiworld.com/16111/xr1.jpg">
FATS time was 4.2 (which was actually 2 runs averaged both ways). Weather was 41 degrees F, and other mods include milltek superdual, airbox hole, new stock filter, de-screened Bosch MAF, lightweight wheels and battery, no spare.
04-04-2005, 02:18 PM
#7
I don't care what snails you have, FATS under 4.5 sec is a damn fast car......
I know we all gripe about a tenth or two of a second, but when you compare 4.5 and under to what's on the road, that's damn fast!!!!
That being said, when can you come over and make my car another tenth faster?
That being said, when can you come over and make my car another tenth faster?