Modified IDM and tuning

[Colt]

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?

[cleatus12r]

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

Originally Posted by Colt

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..

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.

[907DAVE]

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

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

[cleatus12r]

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.

[907DAVE]

Originally Posted by cleatus12r

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.

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. 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.

[cleatus12r]

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).

[Colt]

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

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.

[907DAVE]

Originally Posted by Colt

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...

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.