Return of a Tuning Tale. Chasing classic knock

[XfireZ51]

Thx Erik. Glad u find this informative. As we all know, an ICE needs air/fuel/spark. Just as we expect each spark plug to provide the same level of combustion ignition, we can?t overlook how the injector is providing the necessary proscribed fuel. Uneven fueling leads to compromises in the tune. In our case, the 16 injectors actually makes it a bit easier to even things out when both primaries and secondaries are in operation. That?s why I think this exercise has highlighted an additional benefit to deletion of running in Valet mode or on primaries only. Of course, its not necessary to yank everything out. Simply have the secondaries begin operating just off idle.

[XfireZ51]

As a number of you know, I?ve been ?struggling? w eliminating a particular area of the SA table free from knock. It happens to take place right where the motor runs during highway cruise. And it seemed that the slightest change to MAP could bring on knock retard. Sometimes minimal, other times 1-2*. Basically, it made me hesitant to even take long trips in the car.
Recently, I have been focusing on AE delivery as an primary area for modification. Altho I was doing this primarily to eliminate knock, I have found that the process has also produced a real improvement in how the motor responds to accelerator input. Its just that much smoother accelerating and more responsive. I should say that re-configuring and balancing the injectors has resulted in much tighter control of fueling and results in much less ?compromising? of the disparity (split BLM) between left and right cylinder banks. And finally, along w a slight reduction in SA in that ?cruise? area, I was able to either completely eliminate knock or reduce it to a couple of knock counts invoking minimal ECM intervention. That was not the case in earlier attempts of reducing SA. It was a matter of getting the AE correct which then allowed me to get the SA right also. Its allowed me to get BLMs throughout VE table to 128 +/- 3. As a result, the car is sooooo much more fun to drive. Motor and exhaust are also noticeably quieter and smoother sounding. Additionally, MPG has improved by 1.5-2mpg. Just as a note, my LT5 has significant mods from the stock configuration, and so the calibration that ?works? represents a substantial modification from the stock calibration.

[jss06c6]

Great news Dominic!

I've been having fun tuning a 1996 supercharged LT-4 that I've almost finished.. Just a "blast" working on a system with a '95 ECM. Alcohol injection, ARP 195 heads, Tick Performance MAGA 2 blower cam... Etc. Etc, etc.. Speed Density, no MAF. 2 bar MAP.

Very close now. Will finish WOT on Mustang Dyno hopefully this week.

Sent from my SM-G950U using ZR-1 Net Registry mobile app

[XfireZ51]

Steve,

Sometimes I just can?t keep things alone. Pulled a couple of plugs which are the
BKR6Es gapped at . 035. I looked at a previous set of BKR5E-11 gapped at .044? and thought they looked pretty good. So I tried them again, and even better results re:knock.
All of this makes the ZR so much more fun to drive. Acceleration is very responsive and very smooth. All u hear is the exhaust note which is monotone, as it should be.
Now I?m considering going to the dyno for some WOT tuning.

[jss06c6]

That will certainly be a benefit! Each engine has it's own fingerprint. Mine wanted AFR to be at 13.1 at WOT..

I'll be doing same with the LT-4 this week, if I can get on the dyno schedule. Target is 11.5 AFR at WOT. Alcohol injection comes in at boost and cools IAT from 115F to 84F!

Sent from my SM-G950U using ZR-1 Net Registry mobile app

[XfireZ51]

Steve,

Yes my previous WOT tuning also pointed to an optimum AFR of ~ 13:1.

[Paul Workman]

Fascinating thread! Anyone would be pressed to find a better example of the proper application of the "scientific method" - i.e., discovery resulting from cause & effect analysis! . Very thorough, Dom.

[XfireZ51]

Thx Paul. I?m glad u have found the thread informative. Like the rest if us on here, I look to share information about our great cars, and how to maintain and have them run better especially when modified. We keep pushing the edges of the envelope on a ~ 32y/o platform, which demonstrates the forward thinking that went into it.

[XfireZ51]

An additional update. This weekend I had the opportunity to take the ZR for a 600+ mi round trip to Michigan. Car ran flawlessly. And when I checked gas mileage I was pretty amazed. 25.5mpg at least 75-80mph average, which include the the typical I80/I94 traffic jam thru Gary, IN. Not bad for a modified LT5 w 4.10s and cams.