Quote:
Originally Posted by ztan
I haven't looked at SOI parameter, but it does make sense that the injection window would be (SOI - spark timing). We'd have to assume that SOI and spark would be referenced off BTDC in the ROM.
Does anyone have the RAM address for SOI?
Kodename47 has had up to 5.8ms on the DI injector - anyone else gone higher?
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Great thread!
Usually the SOI is about 40deg after TDC during the Intake stroke to avoid piston wetting. Normally the injection should end atleast 60deg before TDC firing for good mixture preparation (thumb rule). Essentially we have about 360-40-60 = 260deg. At peak engine speed of 7500rpm we have 8ms per 360deg. This reduces to 5.77ms for 260deg. So the number @
Kodename47 is referring to is the absolute max PW that should be used before running into issues. At this time it is beneficial to start relying on some PFI for better mixture preparation (improves flame speed) instead of relying heavily on DI for knock relief. Saying this because at those high speeds we have seen combustion only a few degrees away from MBT considering this was calibrated on premium fuel.
From what I can see there will be more benefit from reducing enrichment for thermal protection than anything else. This is exactly what @
shiv@vishnu has done. OEMS go crazy on thermal protection and sometimes run ridiculously high FAR (closer to 0.10) From my experience a FAR of 0.088 to 0.09 is enough to protect CAT and Exhaust at peak power. I think the OFT tune puts the engine just there.
For those running CATless headers they probably can push the AFR even a touch leaner. For those with OEM header I would not recommend any leaner than 0.085 at peak power.
There are certain engine speeds where engine is more knock limited than others. You can see this by looking at the stock spark timing. If at certain engine speed the spark advance is less than the adjacent speeds it indicates that this speed is more knock limited in normal setting. At these speeds you need a tad more enrichment since the spark is more retarded. In general the more spark you add the less enrichment you need.