Modified IDM and tuning

Colt · #1 Tue, September 14th, 2010, 12:08 AM

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*** · #2 Wed, September 15th, 2010, 10:16 PM

Quote:

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.

Colt · #3 Thu, September 16th, 2010, 01:06 AM

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

***907DAVE*** · #4 Thu, September 16th, 2010, 01:49 AM

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

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.

***cleatus12r*** · #5 Thu, September 16th, 2010, 08:43 AM

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.

Shaw · #6 Thu, September 16th, 2010, 11:14 AM

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?

***cleatus12r*** · #7 Thu, September 16th, 2010, 10:06 PM

***907DAVE*** · #8 Fri, September 17th, 2010, 12:34 AM

LOL.........

Quote:

Originally Posted by cleatus12r

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

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?

***cleatus12r*** · #9 Fri, September 17th, 2010, 06:54 AM

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.