Right, but if MBT were very low, but you still couldn’t run within 10 deg of it, it wouldn’t make as much power as a higher MBT that you could run dead on? A combination of a high borderline and low MBT should yield the most power, hence my delta chart I posted above.
MBT of 0 is perfect HCCI, kinda like a diesel. There would be no chance of detonation.
More results. The scary part about all this is some "tuners" will say it is normal if Knock advance reads pulling 1* of knock from the borderline value at 0.
Do not use that 50% tune I posted unless you plan on not going above 50% throttle below 3k RPM, are running 4oz or more of boostane with a premium base fuel or some other high octane fuel(ethanol included).
I recommend multiplying the difference values I showed in that post by .5, giving you a 25% increase borderline tune. At least below 4000 and possibly less if you have bad premium gas.
With 4oz of boostane you should be fine. with a full 16oz you probably can get more aggressive.
I decided I was changing from 2k up so I wanted to see what I was changing. On the left is fresh 92. On the right is with a full 16 oz can. If you ever questioned does Boostane actually work, YES, yes it does.
Premium vs Boostane with 50% BDL.jpg
Premium gas.hpl
After boostane.hpl
Last edited by murfie; 04-22-2021 at 03:58 AM.
I?d like to understand your logic on this.Originally Posted by murfie
Hypothetically, lets say the Ford borderline table is calling for 10 deg of timing and MBT is 20. However, you put the crappiest 6 month old 87 octane you can find in the tank. It initially sends timing to 10 deg. Lets say the knock sensors are quiet, so knock advance starts adding. It adds 8 deg before knock is sensed and it pulls timing, so it winds up at 17. In this case, what would be the harm in changing the borderline to ~15? It would still reach the same 18 and knock just like the original settings, but it would get there much sooner.
It’s how I usually do my spark tables I see what the knock sensor is adding on its own throughout the log and if I see anywhere that it adds over 4 degrees on its own I’ll go in and bump that up so the sensors don’t do all the work
You make it sound like that's not what my borderline changes do/did.
I'm just saying starting at 50%, where that file I posted is, is too aggressive for premium pump gas. Don't just copy and paste with out using a better fuel or at least verify it after you copy. If you noticed borderline is climbing a step hill below 3000 RPM, increasing timing on its own as much as the fast rate of the knock advance.
The percent is referring to the time it takes the stock advance rate to reach MBT starting from borderline.
stock vs 50%. flatter borderline above 3000, and my method even shaped it to follow MBT better with out axis value changes. Meaning it relies even less on knock advance making that PID remain flatter, that usually doesnt happen until you rescale axis values for boost and enter completely new custom values. All with no modification to the stock mapped points angle values or VCT commanded angles. What more could you want.
stock vs 50%.PNG
Logic as to why I don't want to have borderline above MBT? On the Gen 2's any knock detected while final spark was lower than the borderline value seemed to be treated as full intensity knock and the max advance was pulled out. If these are the similar and I do encounter knock or false knock I want the appropriate change to the final spark advance to be made, not just for it to go into a emergency spark reduction like mode over a little noise. The ECU reacts the best when it has the most accurate information about what is really going on, and you are not trying to trick it or leave it in the dark, and I'm fully aware thats what I am doing out of caution.
Last edited by murfie; 04-22-2021 at 05:36 AM.
No worries, just trying to understand. I think we're on the same page but you're taking a more conservative path.
So one of my buddies stopped by with his 2019 F150 5.0 and we decided to do a similar test on it. 100% stock truck on 87 octane with something like 60k miles on it. The good news is that his air load was very high, peaking near 1.05. The bad news is it knocked like crazy and couldn't even run borderline at WOT, sometimes running as much as 4 deg below borderline. I don't know why, but perhaps the fuel sold in Hawaii is higher octane for whatever reason, since the octane rating is just the minimum. Or maybe his truck needs a tune-up...
19 f150.JPG
19 f150.hpl
Last edited by engineermike; 04-22-2021 at 03:17 PM.
I just wanted to jump in here and say this is the most enjoyable tuning thread I have read for many years.
Thanks for your efforts Murfie.
Last edited by Evolution Stu; 04-29-2021 at 03:19 AM.
+1!I just wanted to jump in her and say this is the most enjoyable tuning thread I have read for many years.
Thanks for your efforts Murfie.
2020 Mustang GT Daily driver
|Hellion Sleeper|10R80|Full weight, full exhaust, BABY seat in the back|
8.3@167mph
2014 Mustang GT
|Hellion TT|Powerglide|Ignite114|
6.87@200mph
Jordan Performance and Racing
Looking forward to a similar discussion regarding injection timing...
I think this is what the stock direct injection timing looks like. I'm going to have to play around with the 1-shot intake table and see if it moves in the direction that I am thinking and that my math is all correct.
720 injection timing.PNG
Update it moved exactly the way I thought it would. Now which way should it move.... Into the compression stroke for an artificial effective compression bump, or closer to the EVC for better splash/mix off the top of the piston.
1-shot intake -75.jpg
Last edited by murfie; 04-25-2021 at 09:04 PM.
That’s funny; I have that same chart built but mine counts the opposite direction (as spark and gdi events are), as opposed to cam timing counting forward. Obviously, neither are wrong.
Your log shows soi at 420. 720-420=300, which is what the 1-shot table calls for at wot. Though I think Ford revised this to 330 later, I would have to check. I’ve tried 340 to get more window but found a mysterious limit that seems to reduce as rpm rises, and I can’t figure out what’s causing it. It will hit 340 as commanded but by 7500 rpm it becomes erratic and drops to ~331.
SOI minimum is 410, and SOI vs ECT is 370. That pretty much covers exhaust cam movement for starting injection right as the valve closes. Even if you moved those, I would think you would still need to enable OVI to inject in the overlap with the exhaust valve still open. Too far open and the cat temperature probably will not like that, so there also might be a hidden limit to protect those.
Then there's the EOI limit, that 100-160. thats not that far into the compression stroke, 20-80* from BDC. Based on lift pump pressure falling. going into the compression stroke has to be hard on the high pressure pump.
Last edited by murfie; 04-26-2021 at 04:03 AM.
Working out the timing using your numbering system....EVC at "0" is 369. Max EVC phasing is +50, making max EVC 409. I don't know if the "SOI Minimum" is counting backward or forward for sure, but if it's counting forward the stock number of 410 makes sense. Either way, I've changed this to 390, which is more like the Ecoboost numbers, and it didn't change the SOI "hidden limit". SOI vs ECT clip of 370, whether counting backward or forward, wouldn't interfere with a commanded 1-Shot intake in the 330-340 range, as far as I can tell. To apply it specifically to our case, counting forward as you did, EVC at "0" being 369 and high rpm WOT exhaust cam retard being 18 means we wouldn't want the SOI to be before 387 deg. Therefore, you could command the 1-Shot Intake as early as 387 (333 in the 1-Shot Intake table frame of reference) using stock EVC, and you see that Ford skirts it with a 3 deg margin.
The issue I've observed, however, is that the SOI defies the 1-Shot Intake table and is pushed later at high rpm, while the exhaust cam is going the opposite direction (advancing). I've observed this on Gen3 Coyote and Ecoboost. For instance, at 6500 rpm, I've logged EVC of 387 and SOI of 384, starting injection 3 deg before EVC and everything is happy and working as commanded. However, at 7000 rpm, the exhaust cam might advance to 386, giving more time for SOI, but logged SOI is now not following the command, but only at 388. The logged signal also gets erratic when this mystery limit comes into play, appearing like spark advance when per-cyl is on. I'm sure this explanation of the problem is awful.
My understanding around OVI was that it is regarding the port injection side - an OEM attempt at getting PFI to act more like GDI by injecting into the cylinder through an open intake valve, which would allow more cooling of the air charge and less cooling of the valve. The challenge was phasing it correctly to the crank, which of course is very easy to do now. Note that this feature is enabled on the Gen2 but disabled on the Gen3 stock.
I had assumed the EOI limit table was a function of GDI rail pressure, which the values don't seem to line up well with. Either way, I'm glad you brought up EOI because the logged EOI limit doesn't seem to follow the table either way you look at it. I've played quite a bit with the EOI clip and been successful pushing it back. For instance, using an EOI clip of 30 deg at 150 psi resulted in a logged EOI clip of 76. Changing it to 25 resulted in a logged clip of 71. They are related but not 1-for-1. Let's say the pressure is the lift pressure, then linear interpolation would yield a limit of 130 deg in my case, so that doesn't make sense either. I'm not saying you're wrong, as being a function of lift pressure makes more sense for a couple of reasons, but the logged and commanded number still doesn't correlate well.
Regarding injection during the compression stroke, some quick and dirty math on isentropic compression yields that halving the volume results in about 25 psi in the cylinder, so you can easily inject well into the compression stroke without worrying about too much cylinder pressure. I'm more concerned with mixture distribution since the Coyote piston isn't designed for a stratified charge.
So I played with it more. Made it 100% DI at idle and tried all the tables I see available. The best I could get is 10* BTDC in the exhaust stroke at idle. As soon as I touch the accelerator pedal and raise the RPM, it goes to 10* ATDC in the intake stroke. I see what you mean by some thing we don't have control over. It could be some hard limit that we will never have control over as its the way Ford designed it.
As for end of injection, I have no trouble pushing the pulse into the compression stroke. With in 50*, and almost with in 30* of the spark event at times. I don't think I need to go closer, but it appears I could. This does great for helping with detonation limit in the low RPMS, but ruins peak VE and load. I might do a mid RPM shift in SOI. I might also play with the blend percentage to not have as much from the DI at points.
Ideally it would be split injection or this LSHL mode needs to be better defined. A conservative use of DI. Just enough to get the best VE the rest can come from the port injectors is what I'm seeing. It also kind of appears this is what Ford was going for, unless this LSHL mode is doing something I can't see in the scanner.
Late DI2.PNG
Which ever you perfer.
Inverse DI timing.PNG
Last edited by murfie; 04-27-2021 at 02:36 AM.
Thanks, Murfie. Interesting stuff.
It looks like in your posted snips that you reduced 1-Shot Intake SOI to hold the EOI relatively constant around 75 deg BTDC. Did you experience any mis-fires? Some time back I set my SOI to 180 to get all of the GDI to happen during compression and it mis-fired, my theory being that the fuel distribution in the cylinder was sub-optimal and there wasn't enough time for a homogenous charge to form.
You mentioned commanding SOI to 10 deg BTDC on the exhaust stroke; did the logged SOI data become erratic as soon as it broke from commanded? Not bad, but a deg or 2 of variation? Would you mind posting this log or screenshot? Ford commands a maximum of 330 deg SOI, which I have found just barely avoids this mystery "dynamic limit" that seems to reduce with rpm. The ecoboost motors command as high as 336 but they don't rev as high either, so less likely to hit it. It would be nice if we could make this follow EVC at high rpm to maximize window.
Can I ask what EOI clip numbers you used to achieve 50 -70 BTDC EOI?
I learned a little from looking at the ZR1/LT5 calibration. For instance, their EOI limit is based on a margin before spark and is set at only 5 deg in the stock cal. They start pushing SOI earlier once this is hit, but their injection strategy looks very different from ours. This does give me some level of confidence we are on the right track if knock reduction is the goal. Something else in the LT5 calibration is probably a better explanation of why the EOI table pressures are so low, and also keys into a point you made earlier. If the HPFP is not primed or otherwise functional, then the GDI rail pressure will only be at Lift pump pressure. So, the EOI clip table only has two pressures: one that is around where the lift pump pressure runs (for use when the HPFP isn't making pressure) and the other is well above what the maximum the lift pump can do (for use when the HPFP is clearly functioning). The very high EOI at low pressure (55 psi) prevents cylinder pressure from rising and overcoming rail pressure. Then at higher rail pressure (150 psi) when the HPFP is working, the EOI clip moves to where it lives during normal operation. It's almost more like a toggle.
I did a sanity check using your log posted above. Using the injector slope/correction, rough air flow, rpm, and injection duration at an assumed 90% blend, I calculated a lambda:
SOI - EOI = 97 deg
4980 rpm = 29,880 deg/sec
97 / 29,880 = 0.00325 seconds injector duration
0.0378 x 1.013 = 0.0383 lb/second injector flow rate
0.00325 seconds x 0.0383 lb/second = 0.000124 lb fuel/injection event
0.000124 / 0.9 blend = 0.000138 PFI plus GDI flow/event
From the prior log, MAF pw was 123 ms, equating to 35.7 lb/min / 4980 rpm = 0.00717 lb/revolution or 0.00179 lb/event at 4 events/rev.
0.00179 lb air / 0.000138 lb fuel = 12.99 a/f, or 0.92 lambda. Close enough for me, considering I made a few assumptions and neglected a few things.
By the way, I think I read somewhere that GDI doesn't hurt VE if it's injected during the intake stroke. If that's true you could leave the blend at 90% and just play with SOI to get the Intake/Compression split where you want it.
Last edited by engineermike; 04-27-2021 at 09:34 AM.
I halved eoi.
No blinking check engine light or perceived misfires. The car was noticably down on power. In the higher RPMs there's not enough time in the compression stroke, even NA. I was in the low 200s and it was getting closer to spark than I wanted to go.
I don't have any driving logs of higher than stock soi. Just idle and free rev. I can post a log of that when I get back to my computer. It was all set up for 100% DI and a static 1-shot across the table of 420, and just moving the limits and other timing tables to see if they had any effect and what it was. I think I have a dozen or more logs saved before I stopped saving and just observed what the changes did if any that I could see.
Log
420 all SI, 400 SOI vs ECT. SOI min 250, 400 limit.hpl
From SAE 980495(done by ford motor company) referring to a previous study. If you know of any good papers to read let me know, hard to tell quality from titles and abstracts. This was a great one applying to making power rather than emissions or fuel mileage. I know theres got to be something about piston top design and SOI related to VE increases.
-DI cools the air charge better than PFI. PFI relies on evaporation, which doesnt effect the charge as much.
-When it occurs early it can increase VE, when it occurs late it can benefit detonation. Based on the heat transfer rate change from the chamber surfaces to the charge. Increase when air and fuel are mixed during intake(PFI can cause a similar effect just to a lesser degree because of the first benefit), decrease when intake is purely air.
If you were wondering about the VE benefit found in the study here's a basic remake of the graph of what they found. It get worst than PFI after 180*, but only 2% decrease at max, kind of like it has something to do with the direction and speed of the pistons travel, going with or against the spray and how far away from the injector it is to have the fuel effect the air charge or the walls/ piston more.
And if you wanted to know the knock limited spark advance effects they found as well. Not exact, but a general representation of what was found. after 60-90* into the compression stroke, the effect levels off.
They were using a short 45* PW to obtain a AFR of 12.5. at WOT and 1500RPM.
Early DI VE.PNG
KLSA.PNG
Hence I want to keep the DI PW limited in the middle of the intake stroke, and avoid detonation with octane since I don't have control over a spilt injection to put the fuel where it needs to go to actually help with out effecting engine airflow too negatively.
Ford already kind of did this stock, but I don't think they limited the EOI optimally, and my theory is 90% DI might be too much when you are not detonation limited.
I don't think a PW from the DI spanning from EVC to as late as possible is benefiting at all, and most likely just hurting things. Put a small pulse middle of intake to improve VE, small pulse in the middle of compression to improve KLSA. PFI for the rest of the required fuel.
Last edited by murfie; 04-28-2021 at 03:41 AM.
From your log, this is a plot of the mystery SOI limit vs rpm:SOI limit vs rpm.JPG
I *think* the ZR1/LT5 does that but it's hard to tell looking at the cal file. Its a shame because the split injection capability is in the Ford PCM to do it and it appears to be used for cold-start in the 3.5 EB, but the coyote either doesn't have it or we can't modify it.
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