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SOI Timing

Practical Diesel Tuning

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2.8 Duramax.My stock tune is retarded as much as -6.5 deg in the low to mid rev range and I understand this is for emissions and a quiet smooth engine but how much should I advance it here?If I do the timing math for 50/50 1800rpm @ 40mm3 I get 7.6 deg BTDC where stock is -6.2 deg ATDC this is a massive difference.How much would you go here?

Is it definitely that far out? Sometimes the way the numbers are expressed can be confusing. The way you've written it there, "after" tdc, but with a negative number, may actually be 6.2 before TDC, if that makes sense?

In any case, if you have access to a dyno, try adjusting it 2 degrees and see what happens. Try to monitor power vs a given fuel delivery, not just throttle position.

I wish I had a dyno but it gets a bit costly to hire one, I’m confident the negative numbers are retarded as you would expect at idle then working to advanced as the fuel and rpm increase, I have made some big changes to my timing but there is a max timing table and I have kept it to no more than this table, it feels more responsive still smooth.