Merlins Ralliart and EvoX TUNING GUIDE Version K.pdf - EvoScan

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MERLINS RALLIART & EVOLUTION-X TUNING GUIDE6.02-KNOCK TUNING – DEALING WITH REAL KNOCKSo, by now you will have been using EvoScan to log your wide open throttle powerpulls and have noticed some persistent knock in the KNOCKSUM column of thedata-log that is not associated with a gear shift. These four parameters, RPM,Spark_LOAD and SPARK and KNOCKSUM are the most important to log whentuning your EvoX or RALLIART. KNOCKSUM can vary from 0 to 36, with 36 as themaximum knock count that the ECU can register.When tuning your ECU it is advisable to tune timing, fuel, and boost withouttriggering an occasional KNOCKSUM more than one or two, three at the most. EachKNOCKSUM count will retard the spark advance 1/3 of a degree, thus a KNOCKSUMof 3 will pull 1° of timing.I tune for 1 to 2 occasional and sporadic counts of knock, three at most. Anythingabove that is unacceptable. Here is my take on knock:1. All cars knock on occasion. I have logged Evos that knocked the first log andthen gave me three knock free WOT runs, including my own. Generally speaking,the first WOT log that you do tends to be knock prone. You have to do at leastthree back-to-back logs to make sure that knock is consistent. I do not worry aboutan occasional log that has a single knock it. If the knock is transient and does notrepeat, I usually ignore it.2. Knock is a problem when it is consistent and repetitive, i.e., it happens every logand at the same point in the rpm range. That is the kind of knock to worry aboutand work hard to eliminate.So, the Evo being tuned has more than 2 counts of knock and the knock isconsistent and repetitive. What should I do to eliminate it? The common cause ofknock on an Evo is too much timing advance. Let us take a look at my stock Evo9with no tuning. My Evo9 consistently and repetitively registered 5-6 counts of knockfrom 5000rpm on. Below is a chart of a typical 3rd gear WOT run on my Evo9.Figure 27:IGNITION TUNING – WOT LOG, GRAPH #1, Evo9REV: 0.K merlin@three.com.au Page 58 of 134
MERLINS RALLIART & EVOLUTION-X TUNING GUIDENotice that the timing @ 5224 rpm was 10° and after 6 counts of knock the timingwas pulled to 8° by 5500 rpm. 6 counts of knock pulled 2° of timing, in line withour prediction that 3 counts of knock will pull 1° of timing.So what is the ECU telling us to do to combat knock?We know from MTBT (minimum timing best torque) theory that we should advancethe timing until we either stop making power or we see the onset of knock. In thiscase we clearly see the onset of knock. So what we have to do is pull 2-3° of timingto combat the knock in that rpm range.Here is the way the log looked after I pulled timing. The boost was almostunchanged and the AFR was slightly leaner in that rpm range. Pulling the timingfrom 10° to 7° @ 5200 rpm cured the knock in this instance.Figure 28:IGNITION TUNING – WOT LOG, GRAPH #2, Evo9So my first approach when tuning is to eliminate the knock. This means that youmust retard the timing numbers (read fire the spark closer to TDC) in the HI-OCTANE SPARK MAP.REV: 0.K merlin@three.com.au Page 59 of 134
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Merlins Ralliart and EvoX TUNING GUIDE Version K.pdf - EvoScan

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