SOI?

[907DAVE]

Ok, so I know this is gonna sound kinda dumb.

Is there a magic number for max SOI?

Like a rule of thumb, dont exceed XX degrees at XXXX ICP at X.X PW at XXXX RPM. I realize this has been the mystery for tuners for quite a while, and probably varies greatly for different injector combo's and I'm sure no one wants to say. I have seen a few SOI maps that are extremely different and I am trying to establish some boundaries to play within.

Can you tell from engine noise when you have gone to far or is it not so obvious?


Thank you for being patient with me.

[F-127]

I can't help you too much, just maybe help point you in the right direction. Check out the forum for Analytune. The idea of Analytune from what I read is to make sure that your SOI, ICP, and PW are within safe parameters. My guess this will be to help make sure your small tweaks don't add up to a big change which could cause some problems.

[cleatus12r]

Oh boy.

This is going to sound real bad of me, but as far as the "magic number" goes, it is ALL dependent on so many things.

EOT plays a HUGE role in start of injection.
The SOI map is simply based on Mass Fuel Desired vs. Engine speed................

There's a map for an adder based on those but for low boost...............

There's a delay map that factors in the electrical/mechanical delay inherent in the injectors....................

The injection control pressure has an effect on the actual start of combustion........

Physical combustion chamber temperature has the same effect...............

Boost pressure (dynamic compression) has a similar effect on speed of flame travel......

Backpressure seems to have an effect as well...............

There are far too many variables to put a "magic number" in for any particular engine. Every engine is going to be different for a maximum or "sweet spot".

As for the ability to tell how much is too much; a trained ear can hear it but you probably don't want to hear it very long before fixing it. It sounds terrible...like marbles in a barrel at extremes.

Good luck.

[907DAVE]

Wow...boost and backpressure were two things I would have never even considered. I did not think there would be an easy answer to this, just trying to be cautious.

Is there any way to see the TOTAL commanded SOI, without the use of a labscope?

[cleatus12r]

Supposedly, the datastream will give you an actual "calculated" SOI. However, comparing that with a lab scope MAY show some discrepancies. I plan on trying it here in the near future.

[907DAVE]

I have never seen that PID before. Probably need the NGS or IDS to see it.