NCCAR IS38 Shakedown Day - July 2024
A lazy day of straightening out the ECU/DSG tunes
Background:
NCCAR (the North Carolina Center for Automotive Research) is a large test facility with a track where some groups run HPDE/TT on, and is actually the very first place I ever did a track day back in 2016 in my Mazda2. You can rent track time at the facility for a pretty reasonable rate if you get enough people together to do it. A long time HPDE friend of mine contacted me and asked if I wanted in… so naturally, I said yes since it would be a month after the prior auto-x event giving me plenty of time to swap the IS38 on beforehand. I figured this would be a great opportunity to do some 4th gear pulls without the risk of getting arrested for that kind of street tuning which I’m not a fan of.
Why the IS38?
More power, duh.
Honestly, I think it might be a good choice when tuned conservatively. While I have plans to throw an oil cooler on very soon, there’s a small chance I may do a day on track without it to see if a really low boost tune (basically equivalent to IS20 power) with an IS38 is easier to keep cool on track. The larger exhaust housing should allow heat to escape a bit more efficiently. This experiment may or may not actually happen because I only have a finite amount of free time… but it’s a thought that’s been on my mind.
I have no desire to go E85 or anything like that. In my opinion as soon as you start screwing with the fuel system is about the point that reliability tends to go out the window. Keeping power levels within the limits of the stock fuel system I think gives the best bang for the buck vs overall speed - plus this thing should be good for nearly 150mph on the back straight at VIR… that’s kind of terrifying in a non-caged car and will likely be run on a lower boost level majority of the time on track. The last factor is that E85 isn’t sold at the pumps at VIR, and there’s only a single pump nearby my home so it’s somewhat inconvenient to want to run. If I get more serious about autocross and less serious about track, that is subject to change but not at this time.
How did it go?
Leading up to the event, the weather was not looking great. Projected rain all day long. And it had been raining for multiple days prior to the event… so I put my narrow 215 wide Conti ECS on the car and brought the Kumho V730s as well just in case it dried out.
Lo and behold, it was damp in the morning with a light mist but turned out to be a HOT day. I was really only wanting to get the ECU/DSG tunes dialed in, so I never swapped to the V730s just out of sheer laziness/exhaustion. I ran into some issues which took the entire day to get straight, and was ultimately sorted by the help of a friend in the Simos Tools Users community.
The only real downside of NCCAR is the incredibly abrasive asphalt. It’s an OEM level research facility and as a result has DOT grade asphalt. The tires took a beating even not pushing the car that hard for maybe 15-20 laps total all day.
ECU Tune
The ECU side was really not a big change from the IS20. I had 128 revisions on the IS20 tune over the course of the past 18 months and was really happy with it overall. I went through a few revisions via street tuning when I swapped the IS38 on - extending out my TTA/ATT (torque to airflow and airflow to torque) tables and making adjustments to the wastegate tables, plus copying a bunch of Golf R turbocharger efficiency related tables to at least be in the ballpark from the get-go.
On the ECU side since most of the work was already done, it was really just playing with boost and timing curves.
DSG Tune
The DSG (DQ381 to be exact) was a bit of a headache. I had started playing with it several weeks prior to the IS38 swap just to get familiar with it while still on IS20 power. I got the Drive mode shift points where I wanted them along with experimenting with a Sport mode that would automatically always hold the lowest gear possible just to verify it was doable. I spent some time in Manual mode as well, but never ran it out real high in the RPMs on the street.
Once I took it out on track, my biggest problem, immediately noticeable, ended up being the car auto-upshifting WAY early in manual mode.
The second issue was that the first lap out I limp-moded the transmission (Emergency mode warning on dash). That’s always fun. It turned out that the DSG clutch pressure spiked just a bit higher than expected and so it was just barely setting that warning. This was an easy fix.
For the auto-upshifting issue though: I went through a ton of different tables, used multiple different definition files, and continued to have problems not being able to hold a gear to 7500rpm. After about 5 revisions and some help from a friend in the Simos Tools community it was straightened out and was able to rev the car out.
Other changes
While the turbo was being swapped, I also took that opportunity to install the JXB Spherical LCA bearings to replace the rear bushing and add back some caster. I’ve been unable to keep those bushings alive, so just decided to be rid of that problem entirely. Anecdotally, the car feels much more solid overall. The steering more “direct”. I can’t really say there’s a noticeable NVH difference though I’m sure is some change. Without the 200TW tires on, this really wasn’t the best place to assess them, so I’m looking forward to doing so at the next autocross event.
I am still running a poly forward LCA bushing to add camber so there is at least some level of NVH isolation. Big thanks to 529 Innovations for the bearings - Pete was able to split up what is normally a “kit” with both front and rear location sphericals since I had no need for the forward ones.
Summary
All in all, it was a successful day:
Car didn’t blow up
No wild changes were needed to the ECU tune
Nothing from the turbo install leaked or had any signs of problems
No signs of problems from the MK8 PCV full retrofit. The BMS can that’s installed inline between the Venturi + TIP only captured about 1mm of fluid all day, and the PCV sensor readings are not wildly higher than IS20 levels.
Lastly, big thanks to Paul Diaz Photography for getting some shots of the GTI on track!
Changes made from last track event
