TL;DR Version - Part throttle tune on the bird has been no bueno forever, decided to finally get serious and have it corrected. No time, sick wife and too much job. Called Dave @ EFX to see if he wanted to get into this mess. He said yes and did a bang up job getting it all dialed in. Car tried to fight a bit but overall we persevered. I'm happy and really enjoy how the car drives now.
Long Version:
As some may know, my car has been to a few tuners in the relative area as I have progressed with the build. Overall experiences haven't been bad but the issue that's been bugging me for some time is the cars normal driveability. The car idles and certainly holds together at WOT. The issue has almost perpetually been the normal acceleration. If I attempted to accelerate moderately, fueling would go lean quickly before correcting but it would bounce back and forth. This would result in pops, bangs, "breaking up", etc.. If I tried to accelerate very lightly to avoid the "bad zone", it would be smooth. Conversely, if I gave it some decent throttle (35-50%), it would be smooth as well but def made a bit more noise than I wanted.
Now granted, I have been dealing with this for years and should have pressed this with the prior tuners. Normally there is some other issue on the dyno, schedule conflict, or desire to get done within a day. In hindsight, not the best way to do things for all parties.
I've been dabbling in the tune game a little bit but far from an expert. My other issue is time. I simply don't have a lot of it to take the car out, make some changes, and continue to do that over and over. I decided it was time to get the tune corrected by a professional. After seeing the recent review regarding Dave at EFX, I reached out to discuss my issue and see if it was worth figuring this out on the dyno vs email/log/email/log/etc. He asked to see the file, made some quick adjustments and said try that. I drove the car and immediately it was soooooo much better. Part throttle mild acceleration was much smoother.
He admitted the quick fix is not the ideal way to get it done and recommended a retune to do it the right way. We set a date for a Saturday which was much appreciated due to my hectic schedule. I got the car down there, Dave strapped it down and got to tuning.
He did a couple power pulls to see where WOT stood. The first pull resulted in some tire spin. Dave smirked a bit (yes Dave, this silly LT1 can make a little jam). Some grape soda/dyno juice/sticky later, the tires were grabbing just fine. The OG tune results were "ok" but needed some clean up. For one, it looks like my injectors were over 100% duty cycle (sweet
) but AFR was reasonable. As I understand it, Dave made a number of tweaks to how the car provides fuel per the HPTuners tables which takes longer worth the effort. To be clear, the goal was not to find more power but get the driveability sorted. The graph below is just for the fridge but she did put down respectable numbers. I do not know how these compare to another dyno and honestly, it doesn't matter.
As dyno days tend to go for me, issues were bound to happen. The first was my drivers side breather decided it didn't want to live in this engine bay any further and committed suicide. The rubber o-ring "holding" the base didn't hold and pitched itself into the drivers side header. The image below shows the result and what my mind thought of after it happened. Not too much oil found its way on the header or engine bay thankfully. I jokingly blamed the revised tune (this will be a theme for the day).
Dave made a custom shop rag breather to get us by for the day. The next few dyno pulls were done to confirm things were OK however it seemed all of a sudden, the car wasn't making any of its normal power. Turns out the charge pipe popped off the blower on a prior pull. I blamed the tune
. Again, not phased by the usual "car being annoying" despite all this prep, the car was unstrapped from the dyno, jacked up and Dave reattached the pipe. Let's continue....
Next and before Dave went further, he wanted to get a fresh 02 sensor for his logging so that was ordered. We hung out in his office for a bit while I learned more about him, the business and what he enjoys outside of his work. Turns out we have a few interests in common and yes, we then followed each other on IG later after the day was done.
The new sensor arrived and back to the car we went. Dyno day crap struck again. The car would fire and die immediately. I blamed the tune and perhaps mystery VATS reared its ugly head. He reflashed to a prior tune, etc and nothing. Same result. And here....we.....go..... I kept a level head but as typical, the car wants to fight me/us every step of the way. Dave grabbed a code pointing to the MAP sensor taking a dump. Again, this is definitely the tunes fault
. The MAP sensor was pulled and tested on his dyno comp....yep....she dead. Miraculously, Dave was able to track down a new sensor at NAPA 8 miles away. I left to go grab the sensor and was back within the hour. Unfortunately, the connector for the new MAP sensor requires a different connector. It looks the same but the slots on the plugs are different. The sensor plugs into the connector he has with his dyno so Dave didn't say anything, depinned the MAP connector, installed his and continued on his way.
To my surprise, the car actually fired back up so he could continue and really get into the part throttle tuning. After a fair number of flashes but nothing ridiculous, the car was really working. The pops, bangs, etc are now gone. The car fuels part throttle properly without the lean or dead rich spots. The car was unstrapped and he said take it for a ride. I have to tell you, it's been a long time since I've really enjoyed driving the car. The throttle response was snappier and it just felt "normal" minus all the blower/exhaust noise. Acceleration was smooth and I found myself having to relearn how I normally drove the car since I was used to driving around the issue. This is a big win and really gives me renewed interest and enjoyment with the car.
Dave was very hospitable, personable, accommodating and spent the time to address what I was after all the while my car tried to throw a wrench in the plan every chance it could.
Here are some dyno graphs to review, analyze and critique but honestly, I'm just happy how the car drives.
