Quote:
Originally Posted by Kodename47
Are you logging PI/DI injection volumes or PW at all? The only reason I ask is that I tested something the other day with 25% PI ratio through the whole of the table (SC car so more volume) and the PIs weren't actually used until quite late and mid/late load. I'm guessing down to minimum volume or PW parameters so something else. I've got more testing to do, I'm trialing an easy way to get PI/DI error minimised without having to run fully PI or fully DI.
I agree that there must be benefits to PI with regards to the mixture benefits, but if you're saying that you didn't feel the dip then you'd see that on a dyno. However I know someone who says that they tested various ratios on a dyno and found little to no benefit from changing them. You really need to test not just the different ratios but the extra ignition timing it allows you to put in as a result.
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Calibrating engines day in and day out at work (both dyno and vehicle) I can say one thing. It is extremely hard to verify changes accurately on the road unless you have dynamic calibration where you can change on the fly and feel the difference right away.
If it was my car I would not bother so much about DI at loads that are not knock limited. There is not much to get out of DI other than VE improvement and some added spark. I have experimented with injection timing for PFI from 50deg before IVO to 150deg before IVO and found that the earlier I inject the better the 0-10percent burn and HC at the expense of NOX. Which says if I had gone DI my mixture preparation would have been weaker.
At WOT I would go 100% DI. There is no reason not to unless at the highest of speeds where the spark is almost close to MBT (maybe 10deg from MBT in most cases). Here you may want some PI to reduce the PW of DI since the injection time available is pretty short as the speed increases. 5.8ms in our engine. So here we trade some spark advance for better mixture preparation to eek out better burn.
At idle it is always debated. Companies go DI and it can help hot restart. With engines with high effective compression ratio will get into huge Pre Ignition during a hot restart. Going DI it allows companies to run lean mixture in the first few (1-5) cranking cycles to avoid pre-ignition during cranking. This fuel control is not possible with PFI during cranking.
In my opinion once engine is up and running PFI is better for mixture preparation but companies have to do tradeoffs all the time and stick with one method and in the case of FA20 it is DI I believe.
Did the car come with PI during first cal release and then later get changed to DI? Or was it always DI during start and idling?