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Old 07-16-2014, 09:04 PM   #197
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Originally Posted by Turdinator View Post
Thank you for your input guys. I was trying to do similar to what Jamesm was talking about as far as getting a good known maf scale on the DI to then scale the PI against. My car is pretty much stock so what I am doing is overkill but I figured it was a good way to learn more tuning etc.


I deliberately didn't change the cold port injection ratio table as I didn't want to mess with the normal warm up procedure.
Whenever i change the port ratios i just change all 3 tables at once. I've found that always running the minimum amount of port ratio necessary for a given setup will allow for significant gains in terms of knock suppression on pump gas.

I essentially monitor Direct Injection Time Final and/or DI requested volume (the latter of which is only available in an unreleased RaceRom beta, so not much use to most folks). I'll then gradually bring down the PI ratio until i'm ~10-20% under what i consider to be a safe limit (1ml or 6.5ms depending on the param that i have access to).

I used this technique on an NA tune last night and was able to make considerable horsepower up top in the most knock-proned area of the curve. With stock port ratios knock up there was an issue @ ~15-17whp over stock (can't remember the actual timing or AFR values, i'd have to look), and by the time i brought down the port ratio and added a couple other tricks we were at 29whp over stock with no knock in sight.

something to consider trying if you're fighting knock above 6500rpm or so. On an NA car you'll never get close to any limitation, even with 0% port ratio across the board.

Last edited by jamesm; 07-16-2014 at 09:15 PM.
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Old 07-17-2014, 03:46 AM   #198
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Something to consider trying if you're fighting knock above 6500rpm or so. On an NA car you'll never get close to any limitation, even with 0% port ratio across the board.
I'm sure I was once told that having more PI at the top end was beneficial as it allows for more aggressive timing, something to do with the DI firing angles/time being an issue.
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Old 07-17-2014, 10:04 AM   #199
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DI gives WAY more charge cooling though, which also lets you run more timing. I imagine that in knock prone areas a colder charge is way more beneficial.
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Old 07-17-2014, 11:15 AM   #200
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^ yep. i believe it's the charge cooling doing the trick, but it's definitely an observable phenomenon lol.
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Old 07-17-2014, 11:46 AM   #201
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Originally Posted by jamesm View Post
Whenever i change the port ratios i just change all 3 tables at once. I've found that always running the minimum amount of port ratio necessary for a given setup will allow for significant gains in terms of knock suppression on pump gas.

I essentially monitor Direct Injection Time Final and/or DI requested volume (the latter of which is only available in an unreleased RaceRom beta, so not much use to most folks). I'll then gradually bring down the PI ratio until i'm ~10-20% under what i consider to be a safe limit (1ml or 6.5ms depending on the param that i have access to).

I used this technique on an NA tune last night and was able to make considerable horsepower up top in the most knock-proned area of the curve. With stock port ratios knock up there was an issue @ ~15-17whp over stock (can't remember the actual timing or AFR values, i'd have to look), and by the time i brought down the port ratio and added a couple other tricks we were at 29whp over stock with no knock in sight.

something to consider trying if you're fighting knock above 6500rpm or so. On an NA car you'll never get close to any limitation, even with 0% port ratio across the board.
Might be a stupid question, but how do you figure the amount of ignition advance you can add safely besides the absence of knock detected? Or do you have to add advance incrementally until knock or the lack of power increase is detected then pull back timing?
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Old 07-17-2014, 12:03 PM   #202
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Might be a stupid question, but how do you figure the amount of ignition advance you can add safely besides the absence of knock detected? Or do you have to add advance incrementally until knock or the lack of power increase is detected then pull back timing?
You won't reach MBT on pump gas... you'll always hit knock first. But yeah, you basically got the idea.
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Old 07-17-2014, 12:14 PM   #203
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Quote:
Originally Posted by jamesm View Post
Whenever i change the port ratios i just change all 3 tables at once. I've found that always running the minimum amount of port ratio necessary for a given setup will allow for significant gains in terms of knock suppression on pump gas.

I essentially monitor Direct Injection Time Final and/or DI requested volume (the latter of which is only available in an unreleased RaceRom beta, so not much use to most folks). I'll then gradually bring down the PI ratio until i'm ~10-20% under what i consider to be a safe limit (1ml or 6.5ms depending on the param that i have access to).

I used this technique on an NA tune last night and was able to make considerable horsepower up top in the most knock-proned area of the curve. With stock port ratios knock up there was an issue @ ~15-17whp over stock (can't remember the actual timing or AFR values, i'd have to look), and by the time i brought down the port ratio and added a couple other tricks we were at 29whp over stock with no knock in sight.

something to consider trying if you're fighting knock above 6500rpm or so. On an NA car you'll never get close to any limitation, even with 0% port ratio across the board.
The stock port ratios are constrained by smoke/particulate emission and fuel impingement on the cylinder wall and piston. When you don't have that as a concern, you can run a lot more DI.
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Old 07-17-2014, 12:35 PM   #204
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The stock port ratios are constrained by smoke/particulate emission and fuel impingement on the cylinder wall and piston. When you don't have that as a concern, you can run a lot more DI.
I'd rather knock less. Plants wither when i drive by anyway lol.
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Old 07-19-2014, 06:33 PM   #205
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You won't reach MBT on pump gas... you'll always hit knock first. But yeah, you basically got the idea.
Are these the tables that control the PI to DI ratios? Looks like it only goes up to 5200rpm.


I'm still getting a bit of knock past 6300rpm with no modification to the Port to DI ratios. And my MAF scale with modified temp compensation runs really rich with cool IAT's and closer to 12.5:1 when IAT get hotter, in case you were wondering why it's so rich. I modified the MAF temp compensation to run with low amount of correction from 68f to 130+f IAT's in closed loop (1.1v ~ 2.8V maf volts). Open loop (2.8v ~ 4.2v)is not so ideal.

http://datazap.me/u/solidone/maf68-1...-1036&mark=971
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Old 07-19-2014, 07:11 PM   #206
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Well this thread answered my curiosity if Subaru still uses closed loop & open loop strategy. My last car was closed loop all the time.
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Old 07-19-2014, 07:41 PM   #207
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Are these the tables that control the PI to DI ratios? Looks like it only goes up to 5200rpm.


I'm still getting a bit of knock past 6300rpm with no modification to the Port to DI ratios. And my MAF scale with modified temp compensation runs really rich with cool IAT's and closer to 12.5:1 when IAT get hotter, in case you were wondering why it's so rich. I modified the MAF temp compensation to run with low amount of correction from 68f to 130+f IAT's in closed loop (1.1v ~ 2.8V maf volts). Open loop (2.8v ~ 4.2v)is not so ideal.

http://datazap.me/u/solidone/maf68-1...-1036&mark=971
Like all maps... the highest value is applied for any higher input value on each axis. i.e. '5200rpm' means '5200rpm or greater'. also of course you can rescale any way you wish.

Temperature compensations are one of the many things that subaru engineers probably did better than we can. They just shouldn't need to be messed with IMHO, and i've never been in a situation where i had to.
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Old 07-19-2014, 08:06 PM   #208
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Like all maps... the highest value is applied for any higher input value on each axis. i.e. '5200rpm' means '5200rpm or greater'. also of course you can rescale any way you wish.

Temperature compensations are one of the many things that subaru engineers probably did better than we can. They just shouldn't need to be messed with IMHO, and i've never been in a situation where i had to.
So values of 0.000 would be 100% DI, right?

Well, using the stock compensation table there was at least a +- 4~5% fuel trim variation in closed loop due to temperature in lower intake volume closed loop operation. I dialed in a maf scale at approximately 66~72f IAT's. When ran within that temp range fuel trim were below 2% in closed loop. Once the temperature gets higher the the fuel trim would change pretty proportionately to the amount of IAT increase leading me to believe the temp compensation needed to be adjusted.
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Old 07-19-2014, 08:30 PM   #209
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So values of 0.000 would be 100% DI, right?

Well, using the stock compensation table there was at least a +- 4~5% fuel trim variation in closed loop due to temperature in lower intake volume closed loop operation. I dialed in a maf scale at approximately 66~72f IAT's. When ran within that temp range fuel trim were below 2% in closed loop. Once the temperature gets higher the the fuel trim would change pretty proportionately to the amount of IAT increase leading me to believe the temp compensation needed to be adjusted.
Yes 0.000 is 0% port, or 100% di.

As for the temperature comp, I suppose you could split hairs trying to adjust comps beyond their factory effectiveness at every possible temperature range, but it'd be a lot of work for little to no material benefit. I've never found a need to do any of that, and my customers don't have temperature-related drivability issues that I'm aware of.

Principle of least intrusion is important. You'll save yourself a lot of trouble by minimizing the amount of opportunities you give it to arise. Only solve identifiable problems after they've been identified, in other words. The goal is better-than-stock drivability, not an arbitrary fueling error number. Just my .02.
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Old 07-21-2014, 09:29 AM   #210
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wondering does this maf scaling technique work for a blow thru FI like the JR kit?
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