[radz28]

I've been following DSX's FB posts for their Atlas PI Controller they're releasing soon, and was trying to understand one of the images Dave shared. I'm trying to understand if it's something to be concerned about, or - if it's no biggie.

In the image that he shared, I'm following the IPW trace. One can see the inflection point where the PI starts coming in, and at the end of the run, where the DI IPW comes down to. He shows a DI IPW of 4.68,s, which, to my humble understanding, sounds fine. BUT - you can see it peak, maybe, around 3500 RPMs (my scaling is just an approximate), but it's considerably higher than 4.7ms, where the run ended. I don't see any Chart scaling in the image (maybe that was done purposely), but that seems like it's gotta be higher than 6ms.

So - if we accept it's some amount higher that where it ended, and maybe make an assumption it's at least 6ms, my question becomes how high is safe in the lower RPM band? Dave doesn't show RAIL PRESSURE either, so we can't see what's going on there, but would there be any concern that IPW would go to 7, 8, 9, 10, etc. ms, as long as it recovers, as we see in the Graph? Does it matter, too much, what happens with IPW that low? Is there a circumstance where that could be an issue (I could imagine a scenario where lugging the engine down there could keep RPMs low and IPWs could be taxed, and that's not how I would operate an engine, but I'm trying to explore any scenario where something like this could be detrimental to the health of the engine).

Is the current thought, after a decade of mainstream DI in our V8s, any different than the convention of thought from years ago? I remember seeing a post (https://www.camaro6.com/forums/showthread.php?t=600436) by toohighpsi, where Mike explored SOI and it's relationships to IPW, and if DSX's Atlas stretches IPW too far, is that something to be concerned about? E.G. - Mike showed it seemed safe to run IPW, around 3500 RPMs, to about 11ms, before the need to be concerned, so is there any new theory or experience to this?

I'm just curious. I already changed my torque model, and don't really retard my airflow such that my set-up requires replacement. I'm just experimenting, and trying to understand where I'm at, and where I should be. Does it even matter if we see 11ms at the height of IPW so long as it comes around, and under control well before the top of the RPM band?

Thanks, as always, for your comments, thoughts, and time.

[jlaudio11]

Originally Posted by radz28

I've been following DSX's FB posts for their Atlas PI Controller they're releasing soon, and was trying to understand one of the images Dave shared. I'm trying to understand if it's something to be concerned about, or - if it's no biggie.

In the image that he shared, I'm following the IPW trace. One can see the inflection point where the PI starts coming in, and at the end of the run, where the DI IPW comes down to. He shows a DI IPW of 4.68,s, which, to my humble understanding, sounds fine. BUT - you can see it peak, maybe, around 3500 RPMs (my scaling is just an approximate), but it's considerably higher than 4.7ms, where the run ended. I don't see any Chart scaling in the image (maybe that was done purposely), but that seems like it's gotta be higher than 6ms.

So - if we accept it's some amount higher that where it ended, and maybe make an assumption it's at least 6ms, my question becomes how high is safe in the lower RPM band? Dave doesn't show RAIL PRESSURE either, so we can't see what's going on there, but would there be any concern that IPW would go to 7, 8, 9, 10, etc. ms, as long as it recovers, as we see in the Graph? Does it matter, too much, what happens with IPW that low? Is there a circumstance where that could be an issue (I could imagine a scenario where lugging the engine down there could keep RPMs low and IPWs could be taxed, and that's not how I would operate an engine, but I'm trying to explore any scenario where something like this could be detrimental to the health of the engine).

Is the current thought, after a decade of mainstream DI in our V8s, any different than the convention of thought from years ago? I remember seeing a post (https://www.camaro6.com/forums/showthread.php?t=600436) by toohighpsi, where Mike explored SOI and it's relationships to IPW, and if DSX's Atlas stretches IPW too far, is that something to be concerned about? E.G. - Mike showed it seemed safe to run IPW, around 3500 RPMs, to about 11ms, before the need to be concerned, so is there any new theory or experience to this?

I'm just curious. I already changed my torque model, and don't really retard my airflow such that my set-up requires replacement. I'm just experimenting, and trying to understand where I'm at, and where I should be. Does it even matter if we see 11ms at the height of IPW so long as it comes around, and under control well before the top of the RPM band?

Thanks, as always, for your comments, thoughts, and time.

Really thinking about what you're asking I think ipw max has been a generalized statement put out there for awhile as a basic guideline. What I think is actually more critical is the soi and eoi. By nature with an engine spinning lower rpms you have more time before getting into ignition, to get fuel in and a reasonable eoi. I don't think I've seen anyone really break it down as to how much you can get away with at what rpm. Dave has been doing this testing and would probably be the one to have that information, Im not sure he would share it though.

[radz28]

Originally Posted by jlaudio11

Really thinking about what you're asking I think ipw max has been a generalized statement put out there for awhile as a basic guideline. What I think is actually more critical is the soi and eoi. By nature with an engine spinning lower rpms you have more time before getting into ignition, to get fuel in and a reasonable eoi. I don't think I've seen anyone really break it down as to how much you can get away with at what rpm. Dave has been doing this testing and would probably be the one to have that information, Im not sure he would share it though.

Exactly.

I'm not a person that thinks I'm entitled to information he (or anyone else) has invested time in for free, or at all. I respect that, completely. Would it be nice to learn about? Absolutely. Will he? I doubt it, lol.

Fortunately - during these hits (I'm at about 75% pump E'), I see my SOI not get much out of the mid-370* and EOI never gets below around 190*, so I'm kinda' pushing SOI (as far as the information I've found [I saw a post or two by megahurtz showing OEM LT4 cam should be okay up to around 370* or so, I think]) about as high as makes sense (for a stock cam LT4), and EOI is plenty safe (being higher than around 180*), so I'm not spraying where I shouldn't.

If I can get another account of (or recent account) a sense of what is considered "safe", RPM-wise, I can feel better. Shoot - if it doesn't really matter, and SOI and EOI in these events prove that out (like I'm seeing in my logs), then I can feel good about that, too.

Maybe THAT'S the question I should be asking: If SOI and EOI are within safe bounds (not spraying into open intake and exhaust valves), then does IPW really matter? When IPW goes high, and RAIL PRESSURE drops, but SOI and EOI are okay, maybe I'm concerned about nothing?

[KingLT1]

You are overthinking this.

If IPW is <5.5ms on the DI side 99% chance your injection timing is in range.

Normally don't start seeing the edge of where the injection timing should be until pulse widths get north of 5.8ms.

IPW is the biggest thing to watch. SOI/EOI getting on the edge will simply cause power to start falling off but it doesn't mean that it's not "Safe". It's just getting past the point of optimal efficiency.

My IPW run 5.7-5.8ms with a 371 SOI and 160 EOI. This is a SBE LT1 with 10-11psi for 5+ years now.

You would have to be doing some real dumb shit to blow up a LT4 at your power level.

[radz28]

Originally Posted by KingLT1

You are overthinking this.

If IPW is <5.5ms on the DI side 99% chance your injection timing is in range.

Normally don't start seeing the edge of where the injection timing should be until pulse widths get north of 5.8ms.

IPW is the biggest thing to watch. SOI/EOI getting on the edge will simply cause power to start falling off but it doesn't mean that it's not "Safe". It's just getting past the point of optimal efficiency.

My IPW run 5.7-5.8ms with a 371 SOI and 160 EOI. This is a SBE LT1 with 10-11psi for 5+ years now.

You would have to be doing some real dumb shit to blow up a LT4 at your power level.

I think I understand why you'd say this. I haven't shared much...

I'm d1ck1ng around with some stuff, experimenting. With the Scanner logging SOI/EOI at ~ 370*/190* (I'm commanding about a max' of 370*, including the Alcohol Adder) the whole hit, I will see IPWs jump to ~ 9ms, and RAIL PRESSURE fall to 9-MPa. Starting the hit at about 2200-RPMs, IPW-HPFP goes crazy to around 3500-RPMs, BUT - do start coming back from there to where they need to be by around 5500-RPMs (<5ms and 20MPa [commanded]). So I get a recovery of where they need to be, presumably, after the engine's spinning fast enough for the HPFP to be pumping fast enough for the demand. This is also where my LSFP drops to bottom 50-psi, as described in the other thread...

OK - after adding all that, it sounds like you're saying my SOI/EOI is probably showing a safe condition in this area of concern, even though IPWs/HPFP is going a little nuts? I don't mind if I'm losing a little efficiency down there as much as I am safe. I'm not going to be lugging the car that low on purpose, so this is just more for safety than anything.

I just don't want to do stupid shit in my experimenting, lol.