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How the PCM and IDM work

53K views 169 replies 45 participants last post by  F250Hoss 
#1 ·
From another thread maybe you guys that have a much better understanding then I do of this can school up the masses on how the pcm and idm work and how they work together? Make me smarter then the PCM is the brain and the IDM is the electric engine to fire the injectors.

Tom
 
#53 ·
what good does this do once you are outside the bowl on the down stroke and even way before this....



That's my point.......just wanted a point of reference to picture the 90ish degrees of crank angle during questioned PW.
 
#55 ·
Let's not turn this thread into with name calling and what not.
Dennis, I was making the point that what good does having megapulsewidth do if you are way past your mechanical window. If you are commanding 3ms of pulsewidth at 4000 rpms and getting 2.5ms of actual injection time from that you are injecting for (360*4000/60/1000=24 degrees per ms). You would be injecting for 60 degrees of crank rotation.... How much more pulsewidth than this is useful anyway?
My only point is that Jody found some settings and was able to document that changing them no longer caused the PW to drop to next to nothing when trying to rev over a particular RPM. We may not be able to use 3.5ms at 4500rpm, but if we can modify the PCM to prevent the PW from dropping to almost 0 when crossing the previously set limit we can probably command a useable PW at 4000+ using the PCM and no other external electronics.
 
#56 ·
Regardless, the PCM doesn't have to be in the equation to verify this "multiplier" theory. If you use ANY controller that gives a valid FDCS and CID signal, the IDM will interpret it accordingly. It has no idea that the device controlling it is not the factory PCM. The Ecolizer guys proved that there is nothing but a 1:1 ratio across the entire RPM band.
"Ecolizer" guys? Sorry, I must be out of that loop???
 
#57 ·
My only point is that Jody found some settings and was able to document that changing them no longer caused the PW to drop to next to nothing when trying to rev over a particular RPM. We may not be able to use 3.5ms at 4500rpm, but if we can modify the PCM to prevent the PW from dropping to almost 0 when crossing the previously set limit we can probably command a useable PW at 4000+ using the PCM and no other external electronics.

Was this accomplished by finding a secret table or setting, or by adjusting the pw to a length which would not completely piss off the idm/pcm. The pcm, as i understand it correct me if im wrong, understands the limits of the idm, so if you ask for so much more pw than it can accomplish, it will pull it way back. "begging and pleading" the pcm to give the right pw isnt a terribly new concept and it has been working well for some tuners. however, the 6.xxx ms at 4000+ rpms is not possible, even if the obd2 port is saying so. neither is the 3.7 or whatever. 4000 rpms with 80% duty cycle is capable of 3.0xx ms pw.
 
#59 ·
There are a couple of guys around here that build a device controlled by a PC that interfaced to an IDM and simulated a PCM. You called for rpm, # of shots, and pulsewidth you pressed "go" and it ran the IDM accordingly. It is a huellva setup to run a flowbench....
:D

Kevin:
At what rpm would you not be able to inject any fuel. If you go down to .5ms, how many rpms would it go to before it would flat line?
Not sure if this helps, but when I sat down the one day, I could not get the injectors to fire below something like .85ms. RPM's don't matter at that point. You can still get 1.7 ms at 6k rpm...
 
#60 ·
Was this accomplished by finding a secret table or setting, or by adjusting the pw to a length which would not completely piss off the idm/pcm. The pcm, as i understand it correct me if im wrong, understands the limits of the idm, so if you ask for so much more pw than it can accomplish, it will pull it way back. "begging and pleading" the pcm to give the right pw isnt a terribly new concept and it has been working well for some tuners. however, the 6.xxx ms at 4000+ rpms is not possible, even if the obd2 port is saying so. neither is the 3.7 or whatever. 4000 rpms with 80% duty cycle is capable of 3.0xx ms pw.
I'm not at liberty to specifically answer that question, Jody is a member and if he wants to be specific he can but I will not step on his toes in that arena. I will say that it's far from "begging and pleading" with the PCM.
 
#61 ·
And nobody is doubting that Jody has improved his tunes and can run the rpms very nicely. HotRodTractor (Jason) has been running rpms for a good while on the stock PCM.

Everyone was simply calling BS to the claimed amount of pulsewidth being run.
Our reasons are:
1. It can't happen
2. It isn't useful at that rpm anyway.
3. Someone was running a Dual IDM setup Jody tuned and it didn't work as well.... was it because the mega pulsewidth was actually command overlapping injection events, dumping way too much fuel after it could actually be used, and consuming all the HPOP oil?

There is another thread talking about high rpm power that is talking about the injection "rate" required to make high rpm power since mechanically we have less time that what the IDM is giving us to get the job done already....
 
#62 ·
There are a couple of guys around here that build a device controlled by a PC that interfaced to an IDM and simulated a PCM. You called for rpm, # of shots, and pulsewidth you pressed "go" and it ran the IDM accordingly. It would be a huellva setup to run a flowbench....
Matt,

Are you one of those "couple of guy"? Is Charles? I know Charles had something running on his work bench, and I commend both of you for the work you've done. Was any of the specific "ecolizer" data published by whoever did it in the forums somewhere that I didn't see? Links?
 
#64 ·
Matt,

Are you one of those "couple of guy"? Is Charles? I know Charles had something running on his work bench, and I commend both of you for the work you've done. Was any of the specific "ecolizer" data published by whoever did it in the forums somewhere that I didn't see? Links?
Check out these threads (the second one is more current).

http://powerstrokenation.com/forums/showthread.php?t=6348

http://powerstrokenation.com/forums/showthread.php?t=10563

Also refer to Andy's sig (the author of these threads), as he has lots of info about the IDM on that site (or at least he did).
 
#65 ·
And nobody is doubting that Jody has improved his tunes and can run the rpms very nicely. HotRodTractor (Jason) has been running rpms for a good while on the stock PCM.

Everyone was simply calling BS to the claimed amount of pulsewidth being run.
Our reasons are:
1. It can't happen
2. It isn't useful at that rpm anyway.
3. Someone was running a Dual IDM setup Jody tuned and it didn't work as well.... was it because the mega pulsewidth was actually command overlapping injection events, dumping way too much fuel after it could actually be used, and consuming all the HPOP oil?

There is another thread talking about high rpm power that is talking about the injection "rate" required to make high rpm power since mechanically we have less time that what the IDM is giving us to get the job done already....
This will be the only post I make here. For specific information Jody can post it if he so desires.

You are incorrect here. Jody did not do the tuning for the dual IDMs set up on Carson's truck. Only for the single IDM with new tuning he worked on for him based off of what info he gave Jody about his truck.

Diane
 
#66 ·
Andy built the controller that is running Jim's flowbench. I supplied the IDM connectors to further the understanding of the IDM/PCM setup as well as with the intentions of finding fuel at RPM.

Sorry guys there is no magic. This is how the IDM works. There are no secret tables that change these facts. There are things that can be done to make a truck run smooth at RPM, but that does not mean you are getting the PW that you see from the PCM out of the IDM.

I spin some RPMs at the pulling track. My run at Schied's was 4200+ RPMs, 4th LO. My run at London was 4000+ RPMs, 5th HI. The tuning was improved more after these runs, but the output shaft on the tranny couldn't take it. All runs were with 33" STS tires, 3.73 gears. Vidoes are on YouTube. My truck adheres to the laws of the FDCS, no matter what the OBDII port says.

Does anyone have the contact info for Carson? I need a dual IDM setup as I do have a use for it and can make it work if it is set up properly.

Jason
 
#67 ·
This will be the only post I make here. For specific information Jody can post it if he so desires.

You are incorrect here. Jody did not do the tuning for the dual IDMs set up on Carson's truck. Only for the single IDM with new tuning he worked on for him based off of what info he gave Jody about his truck.

Diane
Oh... sorry then I misread something in the other thread...

Please tell the stenographer to "strike that from the record" please.....LOL
 
#69 ·
WOW, Andy (and Steve it looks like) have done some pretty in-depth work. Most of that means nothing to me, an electronics wizard I'm not.

It will be very interesting to see what the scope shows when Jody and Kevin get together.
 
#70 ·
I'm not at liberty to specifically answer that question, Jody is a member and if he wants to be specific he can but I will not step on his toes in that arena. I will say that it's far from "begging and pleading" with the PCM.
Sorry, the question was meant as more of a hypothetical to further help understand how the pcm/idm work.
 
#72 ·
Thanks for posting those videos and for helping me to better understand this stuff. It makes more sense then when I watched those originally by a long shot.

Tom
 
#73 ·
thanks to everyone who has posted useful information in this thread, along with others... Im pretty good with the mechanical side of how every thing works, Electronics i lacked, but i'm getting some good stuff here, keep it up. Now i've got some big-boy toy stuff in my truck now i'd like to learn how to make it run better.
 
#74 ·
Regardless, the PCM doesn't have to be in the equation to verify this "multiplier" theory. If you use ANY controller that gives a valid FDCS and CID signal, the IDM will interpret it accordingly. It has no idea that the device controlling it is not the factory PCM. The Ecolizer guys proved that there is nothing but a 1:1 ratio across the entire RPM band.
So should it be taken as fact that from this testing that theory that Dennis presented is not a valid theory while still a darn good concept.

Tom
 
#75 ·
WOW, Andy (and Steve it looks like) have done some pretty in-depth work. Most of that means nothing to me, an electronics wizard I'm not.

It will be very interesting to see what the scope shows when Jody and Kevin get together.

I have been way behind on the forums lately as i have been sick I just got caught up on the one that got locked and found this one a while ago. I was digging up the vids just as i got to the point where mattr66 beat me to it. It has been a while but and i havn't watched the vids (dial up) but i'm sure that one of them show how the IDM freaks out when its asked for too much.

We also have a bunch of screen shots on the page in my sig.

We are planning on starting back into the project this winter so the page should get some more updates in the next few weeks.
 
#76 ·
So should it be taken as fact that from this testing that theory that Dennis presented is not a valid theory while still a darn good concept.

Tom
Andy can comment on this more directly, but look at the scope closely for the 3900RPM/3.05ms run in the 3rd video. He states that the divisions are 500us, and the signal appears to be exactly 6 divisions (kind of fuzzy, but you can make it out if you pause the video at the right time). This tells us that the output of the IDM for this scenario is ~3.0ms, or a 1:1 ratio with the input.
 
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