One of the hardest things to get rid of in an Evo is understeer - or push. Like most cars from the factory, the car is front heavy and is setup to understeer once you turn up the wick. You have to drive the car pretty hard to find this barrier, but once you do it will drive you crazy!
In mid 2010 I was so fed up I decided to jump classes and upgrade the
rear diff. I chose Shep's version which is a 1.5 way 12-plate. Oh my
god; the car freakin rotated now! I was now able to better control the car, and hold a 4-wheel slip angle. Instead forcing the rear to come around with tricks, I could get rotation with just the gas pedal.I was able to Especially in the wet, the car was so much more fun and controllable.
At my first event, I could carry a small drift ~80mph for over 100ft w/o
drama! The car now rotated through the turns and I could pick up the
gas soooo much quicker. Times dropped and no side-affects. I did a lot
of refining the car and really liked where I had it sitting at this
After awhile though, as I put on wider and stickier tires, my speeds
continued to increase and some of the push came back. I had heard about
ACD updates a few years ago but never really believed anything about
them. This was one of the reasons I got the Shep unit originally and
not some fancy software that did not have a lot of feedback out there,
at least not from many people I knew.
But I heard something about a newer company - ACD-Tuning
- and I started researching them in late 2011. I talked awhile over
email with Matthew and I explained how the car has progressed and what
would make it better. We decided to team up and I quickly received an
updated ACD unit for testing. I have to say it came quickly and was
packaged very tightly - A+!
Now I've received a lot of offers to test products in the past. Some
are new, some are proven, some have been offered at a discount and some
even free. A majority of the time I do my homework and end up going a
different direction. Meaning just because it's free, I'm not slapping
it on the car. The same goes for stickers/decals. I keep the car
pretty clean and prefer it that way. But this ACD-Tuning I really wanted to see if it could help so I pulled the trigger.
Test weekend #1 - Road Atlanta
In March 2012 I made my first trek to Road Atlanta. I ran Day #1 with
my normal setup using 245 Hoosier R6's and had a time of 1:32.8 I
think. For day #2 there I swapped in the updated ACD unit and ran it in
map #1, which had the smallest change as compared to the factory Tarmac
mode. Overall I did not notice much of a difference. I only ran a few
sessions that day given the 11hr drive but I did better my time to a
low 1:32x. The good news is that the updated ACD unit did not cause me
any problems or issues at all. There was no bind-up, no loss of grip,
no crazy understeer or oversteer, no wheel spin or wheel hop or anything
negative. Now being a new track I only ran about 8/10's so I didn't
push the car incredibly hard or drive 'on the edge', so the ultimate
decision on the ACD-Tuning software would need more testing.
I talked with Matthew about the event and Map #1 and he assured me it
was the smallest change and said everything was good. He recommended to
start with Map #2 next time, especially since I'm running Hoosiers and
all. So that was the plan!
Test weekend #2 - Autobahn.
Although a small facility, a lot of people know this place as Redline
and GTA and One Lap have all been here. It's actually one of my closest
tracks and a great facility. The track is pretty wide and mostly
smooth with some difficult corners and a few oddly placed bumps - and is
known to be hard on brakes. I ran the first day with Map #2 on the
same tires and the car rotated well but felt a little 'skaty'. In
retrospect, I attribute this to some other factors including the new 6pt
cage I had installed, and the fact I was pushing hard on a familiar
track with skinnier tires than my last trip. The car
still rotated well.
With day #2, I switched classes and bolted up my wider 255 A6's from the
previous year. In my first hotlap I ran a new personal best of 1:31.9
(vs 1:32.1 in April/2011) on Map #2. The car felt great. It was so
much more stable and sure-footed on the wider stickier tires and it
again felt like my 2011 setup - the rotation felt good and I even played
around with Map#3 which Matthew put on there for insane drifto! Even
that map wouldn't turn the car into a drift-machine which is actually
good. I didn't want to sacrifice grip in the front in order to gain it
in the rear. I wanted the whole system to work together... just better -
and it was.
Test weekend #3 - Putnam.
Back to another track I know well - running those same 245 R6's which
was nearing the end of their useful life! I ran the car in my favorite
Map #2 and tossed down some low 1:17's. Despite a gearing change from
2011 the altered my shiftpoints for the worse, everything felt great.
Putnam has 2 long L-hand sweepers that can be torture to run -
especially T4. They used to be torture with understeer frankly, and
I've seen many a RWD car have trouble getting the power down here
Leaving the car in Map #2 all weekend - as the grip from the tires got
worse, the car dynamically changed in T4. Keep in mind, that because of
the reduced grip I was pushing really hard, close to 10/10's and the
car was a handful with lots of steering inputs and corrections needed to
keep it literally on-course. As the weekend progressed, the rear was
beginning to rotate more and more in T4 specifically and it was great! I
never adjusted my line, I just kept my foot down and adjusted the
steering angle by opening up the wheel earlier as the rear rotated more
Now I wouldn't really call my car overly developed or refined. It's
running a ton of factory OEM parts still and some off-the-shelf items.
There's no trickery and nothing really custom on it. I'm saying this so
anyone reading this can put themselves in my shoes with regards to how
the ACD-Tuning has helped further refine and aid the rotation in my car.
Now what I can't tell you, is how much the ACD-Tuning
will help a car on the stock rear diff. I can only guess, and that
guess would be enormously! With my car already having an upgraded
rear-diff, coilovers, an aggressive alignment and setup to rotate well -
it only made it better, more controllable and more predictable.
Matthew has been very easy to work with. We exchange a lot of emails as
I send him my thoughts on the car along with turn specific information
and video. He takes all that in, and I believe they are continually
refining their tuning solutions to help the entire market get an even
better product. They even offer an exhange program, but no worries as
our Evo's work w/o the ACD unit in them anyways if you're in a pinch for