200% nozzle = great tow pig

Big Bore · Oct 24, 2011

I thought the lag was added to the PW desired, not subtracted, in addition to timing.

Chvyrkr · Oct 24, 2011

Tarm, I ran 27-28 degrees on my PMR motor with hotter injectors for 28k. I wouldn't expect 28* to be a problem on forged rods.

TARM · Oct 24, 2011

Chevy,

Yes but was that only SOI or was that entire PW? Also was that with the delay factored in or not? I think 28 is safe as well but figure the limit is somewhere close maybe 30 degree max. There are also a number of other issues I will bring up down a bit that I think make all of this and the equip needed if you really want to consistently tune these engines correctly an issue.

BB,

Yes that is correct you add it in. Did I make a mistake somewhere or mis type something to indicate otherwise? In the end what is improtant to take away is just how small and short the actual real injection event itself is as RPMS increase. The actual spray time that is. Its all well under 2 ms

Since Chevy brought up the 28 degree which may even be closer to 30 as a limit if the readings are correct lets roll it out for both 3500 and 4000 rpms with 28 degrees.

We will go with a fixed 28° of crank BTDC that is actual no delays accounted for. Not adding anything extra ATDC. Lets also split the injector delay dif and call it 0.65ms to put a single number to it.

3500 rpms works out to 21 degrees of crank for every 1ms so 21°/1ms 28°/21°=1.33ms
So actual spray time is a mere 1.33ms@ 3500 RPMs BTDC Now add in the delay 1.33ms+0.65ms=1.98ms Now to convert that to degrees we have to convert the delay as this varies with rpm changes. 21°*0.65ms= 13.65° injector delay. Complete SOI 28°+13.65= 41.65

4000 rpms same deal. It works out to 24° (quick formula rpm to degree/ms (rpm/60000)*360=degrees/ms) Injecting for a total of 28° BTDC 28°/24°=1.16ms Delay 0.65ms 24°*0.65=15.6° delay. Complete SOI 28°+15.6°= 43.6°

How do you accurately know any of this and whats going on in the actual engine though. IMO that is why as I see it to effectively and consistently get the best out of these engines to correctly tune them you need: Of course good tuning software, Oscilloscope, CP sensor or system, Load Dyno time along with a host of mechanical gauges to confirm readings if need be.

The more I dig into this stuff the more I understand why you simply can not trust anything you see coming out of that ODBII port i.e. the PCM. At least not without knowing what is really going on at the mechanical level to get a proper correlation between the two.

As an example: Look at all the issues we have had with the cam position sensor ( CPS) with various models doing this or causing codes on that. What if what the CPS is sending us, a far as data, is not exactly what is going on mechanically? If that's the case then..............????? Is the ICP sensor output really what we would find with a mechanical gauge. Basically what its comes down to is you can not trust anything that comes from the PCM/out the ODBII port at face value.

Of course all of this kind stuff has been know by some for years; at least pre '08 based on where I have found it looking for confirmation of things. Its nothing new.

V-Ref · Oct 24, 2011

Big Bore · Oct 24, 2011

V-ref, theres two things missing in that pic.

oke:

V-Ref · Oct 24, 2011

Don't click on the pic, unless you can resist committing 7.3 treason!

Didn't mean to derail the thread guys. Sorry!

BB-I'm a rookie on this thing too, so I'll guess pump gear and fuel shutoff solenoid. How'd I do?

TARM · Oct 24, 2011

You couldn't resist could ya!?!

How different things would be right now if I knew what I know back then. LOL LOL

Jason · Oct 24, 2011

Looks like it's missing the ability to feed 2 more injectors...

Big Bore · Oct 24, 2011

TARM said:
Formulas to compute number of crank degrees there are per millisecond @ any specific rpm:

[(Revolution Per Minute / 60)/1000 = Revolutions Per Millisecond]* 360 degrees = Crank Degrees per MS @ RPM

[(4000 RPMS/60)/1000 = 0.06666 RevPerMS]* 360 degrees = 24 degrees of crank per 1 ms

Wouldn't it be a lot easier to understand and use if you compute ms per degree?

Hotrodtractor · Oct 24, 2011

Big Bore said:
Wouldn't it be a lot easier to understand and use if you compute ms per degree?

The problem is that ms per degree (or degrees per millisecond as I like) varies with RPM. At say 1500 RPMs its a certain number of degrees per millisecond at 4000 RPMs is significantly more degrees per millisecond.

Big Bore · Oct 24, 2011

Hotrodtractor said:
The problem is that ms per degree (or degrees per millisecond as I like) varies with RPM. At say 1500 RPMs its a certain number of degrees per millisecond at 4000 RPMs is significantly more degrees per millisecond.

Once you do the stoichiometry then invert the answer it makes more sense to me for whatever reason. Either way it varies by rpm as you say.

However the PW Tarm is coming up with is much less than what I've understood was available. But based on degrees available at 4000rpm and the math, I can't argue with him.

It's important because it affects the injector size I want to use, or at least the nozzle size. Like 300/400.

Chvyrkr · Oct 25, 2011

TARM said:
Chevy,

Yes but was that only SOI or was that entire PW? Also was that with the delay factored in or not? I think 28 is safe as well but figure the limit is somewhere close maybe 30 degree max. There are also a number of other issues I will bring up down a bit that I think make all of this and the equip needed if you really want to consistently tune these engines correctly an issue.

I understand the issues...

The fuel went boom at 27-28 commanded.

TARM · Oct 25, 2011

Got it LOL I figured you got this stuff. Much was said for others benefit to better follow.

I can see 28 commanded being just fine anyways.

Charles · Oct 26, 2011

It depends on the rpm...

28 degrees is all the rage at ~2800rpm. At 3500rpm it's almost too retarded to keep temps in check, while at 2000rpm it's pretty damned harsh, getting into the danger zone pretty well.

TARM · Oct 26, 2011

Right but that is because we have to include the injector delays. Otherwise the actual window to correctly stay inside the bowl BTDC is a fixed number of degrees with a fixed SOI. The window of actual time changes with corisponding changes in rpms but not the actual degrees or SOI of the window if there is not any delay to account for. Only when you have to adjust for time other than when there is actual spray coming from the nozzle does it effect the degrees when looking at by degrees. This is done to make it easier to cunderstand I guess or maybe something with how the tuning tables are presented. Otherwise what you woulddo is compute that fixed window of degrees into ms based on the rpm and then add in the delays to that real ms inkection window giving you the total. If there was no delays to deal with I think it would be much easier to grasp. It would also make the table to hold at a specific SOI without a pcm adjustment more clear. It can be confusing to say the leastwhen you have a advancement table zero'd yet yourr osciliscope still shows a SOI degree change as rpms increase. That is until you realize that change us to account for the injector delay which is going to cause a advancement with rpms of SOI to keep that actual same degree point of spray at those rpms. Might have been nice to have delay separated or at least made clear what us going on rather than having to work it out as to the reason and correlation. I hope I have said all that correctly LOL

Chvyrkr · Oct 27, 2011

Charles said:
It depends on the rpm...

28 degrees is all the rage at ~2800rpm. At 3500rpm it's almost too retarded to keep temps in check, while at 2000rpm it's pretty damned harsh, getting into the danger zone pretty well.

3000 RPM's, 3000 ICP, 28*. Ish, as no scope was used.

Charles · Oct 27, 2011

TARM said:
Right but that is because we have to include the injector delays. Otherwise the actual window to correctly stay inside the bowl BTDC is a fixed number of degrees with a fixed SOI.

The point of timing is to have the rapidly increasing combustion pressure act on the piston at it's most advantageous positions. If the injection event commenced with zero delay you would still be required to increase timing with increased rpm due to the time required for the combustion pressure to build, peak and fall vs the position of the ever increasing piston sweep velocity.

The window of actual time changes with corisponding changes in rpms but not the actual degrees or SOI of the window if there is not any delay to account for. Only when you have to adjust for time other than when there is actual spray coming from the nozzle does it effect the degrees when looking at by degrees. This is done to make it easier to cunderstand I guess or maybe something with how the tuning tables are presented. Otherwise what you woulddo is compute that fixed window of degrees into ms based on the rpm and then add in the delays to that real ms inkection window giving you the total. If there was no delays to deal with I think it would be much easier to grasp. It would also make the table to hold at a specific SOI without a pcm adjustment more clear. It can be confusing to say the leastwhen you have a advancement table zero'd yet yourr osciliscope still shows a SOI degree change as rpms increase. That is until you realize that change us to account for the injector delay which is going to cause a advancement with rpms of SOI to keep that actual same degree point of spray at those rpms. Might have been nice to have delay separated or at least made clear what us going on rather than having to work it out as to the reason and correlation. I hope I have said all that correctly LOL

What you are describing is the equivalent of a mechanical advance. Just like what you see in a Sigma pump for instance, or any variable timed engine. It is based on a need to accomodate a flame front propogation of a given duration with respect to a piston cycle with a varying period. The combustion must commence sooner relative to the piston cycle as the period between cycles decreases.

Even if you set the injection offset table to zero, you would still have to increase the SOI with increased operating rpm even with an injector that had 0.00ms of lag in order to maintain the same cylinder pressure peak relative to TDC. Or conversely, you would have to reduce the SOI as rpm fell in order to keep the rods inside the block.

TARM · Oct 28, 2011

Charles said:
The point of timing is to have the rapidly increasing combustion pressure act on the piston at it's most advantageous positions. If the injection event commenced with zero delay you would still be required to increase timing with increased rpm due to the time required for the combustion pressure to build, peak and fall vs the position of the ever increasing piston sweep velocity.

That makes sense but how does the need for that injection cone to stay inside the bowl? The reason I likely have these questions is because I have not played with hands on tuning for myself as I would likely be able to better visualize and understand looking at the files and tables. So what it comes down to is with slower rpms you are going to be injecting at less advance that what is the max you can hit the bowl as you have more time for the combustion event to go thru its cycle and only as rpms really start to get faster are you approaching the max number of degree you can fire the injector and have the spray still make it all into the bowl?

Even if you set the injection offset table to zero, you would still have to increase the SOI with increased operating rpm even with an injector that had 0.00ms of lag in order to maintain the same cylinder pressure peak relative to TDC. Or conversely, you would have to reduce the SOI as rpm fell in order to keep the rods inside the block.[/QUOTE]

SO what is the maximum degrees you can have the piston at BTDC (statically) that when you fire the injector the spray cone will be contained inside the piston bowl? That of course is without the delay to fire from when commanded as well I guess the short period it takes from when the spray first leaves the nozzle holes till they arrive at the piston bowl. Those times obviously are going to change with rpms. I just want to know if I set it up statically into position what would be the position that if the injector was fired it would all go into the bowl? I would assume someone or plenty of people (injector manf and perf shops) have tested. No matter how fast the RPM you would never spray at a more degrees than that max static piston position that the spray is contained in the bowl correct?

I can see once that is known that then we can compute everything else. I still think to do as you say, which I agree with, you have to have a way to monitor the combustion event i.e. CP sensor. You can know you are inside the physical limitations but to know you are "keeping the same CP peak" with all those factors that may not be perfectly accounted for you have to be able to see that curve in time,SOI etc... You would look to your actual CP curve to make your final adjustments while staying within those physical limits.

TARM · Oct 28, 2011

Charles said:
The point of timing is to have the rapidly increasing combustion pressure act on the piston at it's most advantageous positions. If the injection event commenced with zero delay you would still be required to increase timing with increased rpm due to the time required for the combustion pressure to build, peak and fall vs the position of the ever increasing piston sweep velocity.

That makes sense. The reason I likely have these questions is because I have not played with hands on tuning for myself as I would likely be able to better visualize and understand looking at the files and tables. So what it comes down to is with slower rpms you are going to be injecting at less advance that what is the max you can hit the bowl as you have more time for the combustion event to go thru its cycle and only as rpms really start to get faster are you approaching the max number of degree you can fire the injector and have the spray still make it all into the bowl?

Even if you set the injection offset table to zero, you would still have to increase the SOI with increased operating rpm even with an injector that had 0.00ms of lag in order to maintain the same cylinder pressure peak relative to TDC. Or conversely, you would have to reduce the SOI as rpm fell in order to keep the rods inside the block.

SO what is the maximum degrees you can have the piston at BTDC (statically) that when you fire the injector the spray cone will be contained inside the piston bowl? That of course is without the delay to fire from when commanded as well I guess the short period it takes from when the spray first leaves the nozzle holes till they arrive at the piston bowl. Those times obviously are going to change with rpms. I just want to know if I set it up statically into position what would be the position that if the injector was fired it would all go into the bowl? I would assume someone or plenty of people (injector manf and perf shops) have tested. No matter how fast the RPM you would never spray at a more degrees than that max static piston position that the spray is contained in the bowl correct?

I can see once that is known that then we can compute everything else. I still think to do as you say, which I agree with, you have to have a way to monitor the combustion event i.e. CP sensor. You can know you are inside the physical limitations but to know you are "keeping the same CP peak" with all those factors that may not be perfectly accounted for you have to be able to see that curve in time,SOI etc... You would look to your actual CP curve to make your final adjustments while staying within those physical limits.