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#4557166 - 10/28/17 12:18 PM DI/TGDI Response to Spark Knock
Danh Offline

Registered: 10/16/10
Posts: 1710
Loc: .
It seems understood that OEMs program their DI/TGDI engines to richen the fuel/air mixture in conditions where LSPI could occur. This question isn't about that.

All modern engines have knock sensors that detect "pinging" or spark knock other than LSPI. In the pre-DI/TGDI days, the response to detected pinging was to retard engine timing. Is this still true with DI/TGDI engines or are they programmed to enrich the fuel/air mixture instead?

In my DI Honda using the specified 87 octane fuel and driving long distances into a stiff headwind at Interstate speeds (think westbound I80 across Nebraska ) will result in a noticeable increase in oil level, presumably from fuel dilution. After considerable experimentation I've found that 91/93 octane fuel seems to prevent this. This leads me to believe that low revs/high load under these conditions does induce some pinging with 87 octane, the mixture is richened in response and fuel dilution results.

I know we can't look into PCM programming, but does this make sense?


#4557311 - 10/28/17 02:23 PM Re: DI/TGDI Response to Spark Knock [Re: Danh]
kr_bitog Offline

Registered: 10/06/07
Posts: 878
Loc: South East Asia
Yes, and most of the time Honda engine will not perform well with low octane gasoline

#4557539 - 10/28/17 06:27 PM Re: DI/TGDI Response to Spark Knock [Re: Danh]
yugrus Offline

Registered: 04/06/04
Posts: 437
Loc: ON, Canada
Our Mazda DI Skyactiv does retard timing, down to negative values under such circumstances. It never occurred to me to check fuel trims at the same time. Will do at some point. Forscan app is great for things like that on Fords/Mazdas.
'14 Chevrolet Tahoe
'15 Mazda CX-5

#4557691 - 10/28/17 08:14 PM Re: DI/TGDI Response to Spark Knock [Re: Danh]
SilverFusion2010 Offline

Registered: 06/29/11
Posts: 1543
Loc: Crawfordville FL
It probably does both.
2010 Ford Fusion SE 3.0L V6, 178k miles M1 AFE 0w-20