Modified IDM and tuning
 

I ordered Minotaur a few mins ago, so obviously I haven't had a chance to tune a diesel yet..

I put this subject here, because I'm interested in hearing the responces of guys that tune, not the guy running "canned" tunes ( not that there is anything wrong with that )..

Running a modified IDM to crank out 140 volts instead of 120, well obviously it allows for quicker injector opening times, which would give you just a tiny bit of room to add more fuel. With a canned tune, I can see where you may see a gain from it. It's the same thing as modifying a sensor to fool the ECM.

But what about when your able to custom tune? If you wanted the same result, all you'd do is add pulsewidth and maybe timing?

With the millisecond ( give or take ) of increase opening times, would someone custom tuning be able to take advantage of that? Obviously in the lower RPM ranges you'll have more time to inject a certain amount of fuel, the more RPM's your running, the less time you'd have..

I can see where that might be an advantage. Just like with forced induction gas engine's ( turbo's ), I can add more fuel down low making the mixture rich, advance the timing and get quicker spool times. The same could be done with a diesel, and is done quite often.

Any thoughts?

The IDM mod has a little bit of effect on a stock truck with no aftermarket calibrations from a programmer or chip. Some folks can really feel a difference, but usually they are in the 95-97 model year crowd. There are great write-ups that Jonathan and Dave of Swamps Diesel Performance have put up over at Powerstroke Nation about how and what the IDM is doing after modification. "golfer" is Dave and "Swamp" is Jonathan.

IDM?? - Powerstroke Nation
Swamp's Hi-Voltage / Hi-Frequency IDMs - Powerstroke Nation

7.3 Power Stroke IDM



Which is why a lot of 7.3L trucks are not competitive. Here is a list of available pulse width times (this is only from an electronic standpoint, not including the mechanical lag inherent in the injector design that hovers around half of a millisecond or more).

750 19.22
850 16.85
950 15
1050 13.5
1150 12.2
1250 11.2
1350 10.3
1450 9.5
1550 8.9
1650 8.3
1750 7.8
1850 7.4
1950 6.9
2050 6.5
2150 6.15
2250 5.85
2350 5.55
2450 5.25
2550 5.25
2650 5.05
2750 4.7
2850 4.45
2950 4.35
3050 4.1
3150 3.95
3250 3.84
3350 3.7
3450 3.6
3550 3.45
3650 3.35
3750 3.23
3850 3.12
3950 3.08
4050 2.9
4150 2.82
4250 2.71
4350 2.6
4450 2.55
4550 2.5
4650 2.45

The above values are why anybody that wants/needs to make big power (higher RPM) uses huge nozzles. There is very little time to inject the needed fuel once you get above 3000 RPM, and larger nozzles are the only way to get the fuel out in that short amount of time.

With any aftermarket calibration, the start of injection (timing) is already advanced by any number of a few methods. There's nothing to compensate for while running a 140V IDM, nor will you see much if any benefit either way while running aftermarket programming.

As far as the whole fuel/"timing" thing goes, you can forget some of the stuff you've learned about a gasser. Too much fuel down low will "snuff out" the turbocharger and you will not get fast spool-up. The same goes with the start of injection; by advancing the "timing", more heat is retained in the cylinder which can slightly delay spool-up. It's good for fuel efficiency and performance once the turbo "lights", but given two identical calibrations but running one with a global offset of a few degrees of retard (from calculated total advance) usually results in faster spool-up due to more exhaust heat being introduced to the turbine inlet.

Nice post, that's some good info right there.

What would you guess the injector delay is at max ICP, still around .5 ms?

It's hard to say without a flow bench and some $$ equipment. I wish I knew.....I just know that it is quite a delay.

I did not realize how big of a difference SOI makes until a few minutes ago.

I have been trying to resolve a engine "ping" that just started to develop recently, which for now I am going to blame on our new winter blend of fuel they started selling us.

After many failed attempts to get this noise figured out I switched back to an older tune that I have not ran in many months. The current program had a very aggressive ICP map which resolved most of my smoke issue, but until now I did not realize how much it hurt turbo spool time.

At about the same acceleration rate (cant base this off APP because it is too different) the boost was over 10psi more than it was before.:yikes2: However there was a very slight haze and EGT's were a tad higher.

Interestingly, the power felt about the same even with 10psi more boost.

There is defianatly a trade off/ balancing act to SOI.

I knew the theory behind it, and used it on my '01 when goofing off. But I played a "trick" on my friend and his truck.

He's got a 99.5 6-speed truck. I put two (and they were the only two) identical tunes on it and he ran it all summer while I was in Georgia. The only difference between them was that I set the global timing offset to -5 on #2 position. Keep in mind that he "short shifts" his truck and all of the driving he does is around town.

I asked him which tune he liked better and why......

He didn't like #2 when cold as it produced a bit of excessive blue smoke in the morning. That's understandable though. However, he was much more impressed with the truck in the #2 setting as it was far less laggy in every driving situation. He also liked that the engine was quieter, but he really didn't care about that since his shift boot is torn out and his 99 is just inherently loud on the inside (unlike the 01-up trucks).

Thanks for the informative post. I've got a bit of reading to do on the IDM thing, and wrapping my head around it.. The only "advantage" I can see to the mod is to open the injector quicker, which allows a bit more time to inject fuel due to mechanical delay. But in reality, it would be minimal gain, and probably wouldnt do anything use your looking for max effort ( drag racing, tractor pulls, trying to squeeze every little bit of power you can )...

I actually figured the opening time for a 7.3 injector would be higher than .5 miliseconds. I have a set of 160 # gasser injectors with a opening time of .4. But then again, these run on 12 volts, not 120 LOL.. You'd probably miss the injection event all together waiting for the injector to open up LOL..


I've got a lot of stuff to "forget" with the gassers when it comes to diesels. The gassers can run a 2 step, skipping ignition events allowing some unburnt fuel to enter the exhaust, then igniting it in the exhaust system. ( kinda like retarding the timing ALOT ). Kinda hard to skip ignition events with a diesel :smiley_roll1:

You mentioning keeping heat in the combustion chamber by advancing the timing. Your absolutely correct there, and it didnt even cross my mind. Heat = Expansion. If all the expansion is taking place in the combustion chamber, you lose heat in the exhaust which means you lose expansion that would be used to spin the turbo.. So yeah, you'd have better fuel economy, but the turbo would spool slower...

It's funny, I work on diesel's everyday, I know all to well how they operate. Yet when I think tuning, the way things are done with gassers runs through my mind. Thats going to take a while to get used to.

So I was looking into ways to exploit this a bit and realized the majority of the base SOI maps already have a pretty significant drop in the low RPM - high MFD ranges - then timing picks back up as the RPM's climb.

Is this in there just for this reason (turbo spool), or is there more to it?

Sorry Colt, little off topic.:)

Bah, I never believed in staying on 1 topic, when things get off topic, thats when ya really start learning things and how they relate to one another. I could never stay on just 1 topic anyways, too many other things to talk about ;)

To those who have not seen the stock PMT1 base SOI map, here is what I am talking about.

http://i619.photobucket.com/albums/t...9/untitled.jpg

Then from there on out the timing advances to a whopping 7 deg. - then factor in the delay (18ish) and you are up to around 25 BTDC @ 3200 RPM.

Mods, I am not sure what maps I am allowed to post.

Please delete if necessary.

Post away. I've gotten much more in detail than that.

Wanna know why the SOI map does that?

Take a look at the desired ICP map and ask yourself what ICP does to the start of combustion event depending on pressure.

hmm, since you brought that up, Ive been wanting to ask. Why the drop in the middle of desired ICP map? Does it have to do with the stock hpop not being able to handle it?

http://i619.photobucket.com/albums/t...7dave9/dip.jpg

LOL.........



When I raise or ramp up the ICP I will try and drop SOI a degree or two in those ranges because of its affect on SOC.

Based off the stock SOI map it appears that they are dropping close to 10 degrees. Is this drop ALL because of ICP, or could some of it be for turbo spool?

I certainly wouldn't worry about dropping the base SOI map due to ICP changes.

I'm stupid-conservative when it comes to my SOI. I smooth out the map and give it a nice, flowing look which will raise the map ever-so slightly right in the center but lowers it a little in others......just so it looks like a smooth, rolling wave. As far as values go, none of them are changed more than 2 degrees in either direction.

First off I like to know about the fritos dip - is it any good?

Next why wouldn't the map look like this? HPOP is my guess.

http://inlinethumb39.webshots.com/45...600x600Q85.jpg

When I run it with this map It doesn't seem to have any problems but I do have big oil?

You can run it all day like that on a stock pump too. But really, there's no need; maybe HPOP may not be able to keep up....or because Ford wanted to do it for other reasons.

The desired ICP map is based on mass fuel desired and RPM.

Here's an exercise for you (do this in your head while looking at the map).

From an idle, punch the accelerator pedal.
MFD is above 70
RPM starts at <700

Where is ICP?

What do we know about the relationship of ICP and injector pulse width for a given MFD?
(Hint: check the pulse width map)


Now, using the ICP map, pulse width map, and any given MFD, you can figure out what is happening when you replace that drop with a straight line.

Bonus points for showing work......:D

Oh, and bean dip is THE BOMB.....

Both when you eat it and also a few hours later!

Well it depends on what bin I look at. If its one that Bill wrote, it would hold the PW thru the dip, if its the stock bin then you would drop PW for a short period thru the dip. Am I seeing this correctly?

(Ill pass on the bonus points for now)

Here ya go.......

http://i619.photobucket.com/albums/t.../Photo0094.jpg

Pretty sure I missed something though, too early for all this thinking.

No, it's that the bench you used is FAR too clean. Has someone been building automatic transmissions on that one lately?

That will work. This obviously is not factoring in the PW multiplier (which on a stock truck at operating temperature is 1 anyway).

Now, since we have a bit of information here, why would we go about increasing the injector on-time instead of maintaining higher ICP to get the same MFD?

Maybe........

http://i619.photobucket.com/albums/t.../Photo0061.jpg

Just a spare for the pickup.

Good question.

Maybe because the injector is too slow, even with the higher ICP.

I would only be able to venture a guess to that one. Basically, you're accomplishing the same thing either way, but I assume that the lower ICP/higher PW is accomplishing the task of introducing a bit of heat to the turbocharger turbine........

OR

The power will come on a bit more slowly and with less aggressiveness with your foot to the wood.

Which reason? Heck, I don't know. It thought that you might have an idea.

So then - back to my original question, how to decrease spool time.

Looks like dropping ICP in the low RPM's, or pulling some timing out would both help this situation.

Would you venture to guess this is what Ford had in mind when designing these maps?

Seems like there would be a trade off, crispy clean throttle - or faster spool up. :hmmm:

And how the heck are you replying when you are offline?:hehe:

I fixed the offline thing just for you.

Silly Mods with all your superpowers.:smiley_roll1:

Wanna see me fly?

About the timing/fuel thing......

You have already experienced the "crispy" nature of high ICP and I think that the dip in the high MFD/low RPM range of the ICP map is to minimize the actual start of combustion and also "soften" the low-rpm acceleration slightly.

Those are just my thoughts though and I could be way off.

Try adding too much fuel at lower RPM's. What happens? You get lots of smoke, and a turbo that seems to take forever to light.

Adding more fuel at lower RPM's doesn't increase the spool up of the turbo. In fact, it can be quite the opposite, increasing lag time until the turbo finally catches up, then you get a neck snapping response after you've killed a few hundred polar bears with the exhaust trail left behind :evillol:

In the mean time.... with all that fueling and no air, EGT's rise quickly. It's especially troubling if your driving up a hill and the engine loses speed. That's when you start seeing smoke pour out the tailpipe, and the EGT gauge rises quickly.

That's why I like my tuning to have pretty much bone stock fueling for the first half of the pedal.

Think of it in terms of pulsewidth... not so much ICP and timing (although those are important too). The main thing to look at is how much fuel is being called for right off idle, and in the RPM range before the turbo spools.

You are correct, however I am not looking to add any more fuel - just retard the timing to help the turbo out a bit. I was looking to do this by pulling some timing out of the base SOI map, or by dropping the ICP to slow the SOC.

I do understand that by dropping the ICP you indirectly increase PW, which I dont think will have a great effect on the total quantity of fuel delivered - it just wont be as complete of a burn.

I have had a bit of time to play around with this the last few days and it seem to be working. It doesn't have that "neck snapping" crispness, but instead a smooth progressive feel.

Have not decided which I like more, but I do like the reduced engine noise.

Colt, now that you thread it bit off topic..........

How Minotaur treating you?