Finished Tuning
On 5/31/2005, I finished tuning the GTP. I started after installing the 42.5-pound injectors on April 23rd. The first thing I had to do was get my Fuel trims to where they needed to be after installing the new injectors. That's didn't take too long to get them right. Next, I tuned the upper range of my RPMs to run the 3.4 pulley with good O2 values and no KR (knock retard). When I started tuning, I was running rich down low and lean up top. I was getting 16* of my timing advance. As I made small changes and tuned, my KR was slowly going away and my timing was going up. It wasn't long until I was seeing 18 and 18.5* of advanced timing with less and less KR. Finally I was able to get the KR to go away and it was time to drop from the 3.4 pulley to the 3.2.
I installed the 3.2" pulley on May 15th and scanned right away. I was getting between 2-3* of KR because I was running lean again. I added more fuel and the KR wasn't going down so I was beginning to look at other options to allow me to run the 3.2 with no KR. Before I started looking, I decided to add a little more fuel to see what happened since our short band O2 sensors are not accurate enough to trust......they more or less give an idea if we're running rich or not. Well after that little bit of fuel, all my KR went away! I was getting 18.5 to 19* of timing advance......it was dialed in!
So, just to see what it would do, I put the 3.0" pulley and scanned the car. To my surprise, I only got 2-3* of KR. So I added a little more in the power range and more in the upper range. I re-scanned and saw less than 1* with 19* of timing advance. Now it was dialed in for the 3.0 pulley! So that's all for now. If I plan on adding any more mods (which I don't right now), I will have to make small adjustments which won't take long.
So through this process I learned how important tuning is on today's cars. I went from running a 3.4" pulley with 2* KR on 16* of timing advance and crazy fuel trims.......to dialed in to a 3.0" pulley with 0* KR on 19* of timing advance. My fuel trims are perfect too. It took over a month to achieve, but it is something you don't want to rush.