Timing Effects

[AH64ID]

Ah yes, I know that name... I'll see if I can hit him up.

[ISX]

Alright I read AH64's stuff some more and looked at that link. That dyno was very interesting. I guess what I don't understand is why 12V's get better mileage with static timing than VP's or CP3's with dynamic timing. They claim emissions and weight differences but I can throw 1000lbs in the bed of mine and still get 25mpg. There is more to this than just timing but for the sake of the thread I will just focus on timing. To me it's almost like mileage doesn't really change, even though boost and power are all different. It's like something is making up for the differences which causes the mileage to be the same. I admit it was a little less but hardly enough to say a few degrees timing will wreck havoc on your fuel tank. I read a huge article once on timing, not really what it does but what effects the degrees, like pop pressure and spray pattern and stuff. What I would like to see is a chart showing exactly where the timing needs to be for most efficient operation at each rpm and power percentile (which I would assume to be most powerful at that rpm as well) with emissions thrown completely out.

[AH64ID]

Your 3.54's and 4x2 make a HUGE difference, that and the weight.. even if you add 1K to your bed I bet I am still heavier, more wind resistant, and despite all my efforts still have a more emissions minded motor... and that doesn't even get into the terrain! I bet I could get 22ish out of my truck at 60 mph in your part of the country, if not more. You also have to consider the CP3 trucks have 2 or 3 injection events and based on EFI Live testing removing and reducing them makes a big difference, up to 3 mpg is reported.. thats a real world 3 mpg not a marketing ploy. 12V's are very efficient motors, any way you cut it. They don't turn the rpms that newer trucks do, which has an effect on mileage when accelerating. I have heard 15-15.5° is about optimal for economy, power, and driveability on a 12V manual trans truck. Timing does play a decent role in my economy. The setting I have now I see at least .75 mpg better when cruising at 75-80, and on more advanced see 1-1.25 mpg better.

[ISX]

Your 3.54's and 4x2 make a HUGE difference, that and the weight.. even if you add 1K to your bed I bet I am still heavier, more wind resistant, and despite all my efforts still have a more emissions minded motor... and that doesn't even get into the terrain! I bet I could get 22ish out of my truck at 60 mph in your part of the country, if not more. You also have to consider the CP3 trucks have 2 or 3 injection events and based on EFI Live testing removing and reducing them makes a big difference, up to 3 mpg is reported.. thats a real world 3 mpg not a marketing ploy. 12V's are very efficient motors, any way you cut it. They don't turn the rpms that newer trucks do, which has an effect on mileage when accelerating. I have heard 15-15.5° is about optimal for economy, power, and driveability on a 12V manual trans truck. Timing does play a decent role in my economy. The setting I have now I see at least .75 mpg better when cruising at 75-80, and on more advanced see 1-1.25 mpg better.

But a 2wd truck the same as mine gets 3mpg worse be it a CP3 or VP44. I know there are emissions things, but for a truck that is most efficient at all RPM's I would think they should be getting 30, as I know if my timing was dynamic I would probably have no problem hitting 30. At 55 I get 27.. I just see all these benefits on the newer trucks but it's like the thought process of having the benefits itself costs you mpg.

[AH64ID]

But a 2wd truck the same as mine gets 3mpg worse be it a CP3 or VP44. I know there are emissions things, but for a truck that is most efficient at all RPM's I would think they should be getting 30, as I know if my timing was dynamic I would probably have no problem hitting 30. At 55 I get 27.. I just see all these benefits on the newer trucks but it's like the thought process of having the benefits itself costs you mpg.

Unfortunately emissions has taken a lot of the efficiency away, any way you look at. The P7100 runs lower injection pressure, less fuel at less pressure takes less horsepower to pump. The CP3 pumping up to 23K takes a bit of hp to make. Unfortunately there are far more variables than just the timing. I do agree that a dynamic P7100 would be pretty cool and probably yield great results.

[dorkweed]

Come on guys...............everyone knows that in order to pollute less you have to burn more fuel!!!!

[Mopar1973Man]

Come on guys...............everyone knows that in order to pollute less you have to burn more fuel!!!!

DPF filter and regen mode...

[ISX]

Come on guys...............everyone knows that in order to pollute less you have to burn more fuel!!!!

Yeah I don't get that at all. A brand new cummins that is completely stock from what I have heard gets less empty than I do with our trailer. I might as well list how I think it is NOT cleaner.

[*]Cleaner now, blows the soot out during regen mode later. I can put a bag over my exhaust, collect the soot, and dump it in the creek when you're not looking as well..

[*]Worse fuel economy means you burn more fuel, how does burning more fuel even though burning cleaner, have lower emissions in the long run. My truck might be dirtier but I burn less fuel...

[*]Indirectly, we now have to make more fuel for these trucks that guzzle it, wonder where the soot during that process goes...

[AH64ID]

I agree!!Thou I do beleive the regen process does work.. look at the tailpipe of a new truck. 100% clean! Something is happening to actually change the soot to something else. But I agree, burn more natural resources to protect them?

[dorkweed]

[*] wonder where the soot during that process goes...

I'm thinking it may go to the same place those socks go that I lose when I toss them in my dryer!!!

AKA..........one of the mysteries of the universe!!!

[AH64ID]

I'm thinking it may go to the same place those socks go that I lose when I toss them in my dryer!!! AKA..........one of the mysteries of the universe!!!

:doh:

[bbraden]

Time to revive this thread!! :)I was curious if anybody else had anymore deep thoughts on the subject. I've read about the IAT fooler, and other things to create different timing. My question is, when you change the IAT reading, does it create an entirely different timing curve for all boost and engine speeds, or does it basically take a pre-determined timing degree and add or subtract X degrees based on IAT? I was looking at a timing table that Moparman put up a while back and it would make sense that it reads RPM & MAP, determines a timing degree, then adds a static X degrees based on IAT. I could be way off though. Any ideas?

[ISX]

Time to revive this thread!! I was curious if anybody else had anymore deep thoughts on the subject. I've read about the IAT fooler, and other things to create different timing. My question is, when you change the IAT reading, does it create an entirely different timing curve for all boost and engine speeds, or does it basically take a pre-determined timing degree and add or subtract X degrees based on IAT? I was looking at a timing table that Moparman put up a while back and it would make sense that it reads RPM & MAP, determines a timing degree, then adds a static X degrees based on IAT. I could be way off though. Any ideas?

Welcome aboard the SS unknown... That chart is ALL we have on VP44 timing. I don't think anyone knows exactly what the IAT changes other than it does change "timing". How much and does it change the map?, nobody knows. Who knows what else goes on that we don't know about. We can hear it knock louder so that is a sign of advanced timing, but my 12V doesn't knock like a 24V unless it is well above 20* timing, so does that mean a 24V is running that high? We have no exact digits, I can't even read that chart that is on here. I can see tendencies of the chart but I can't read it, I want numbers. I have had my timing all over the place and get the same mileage irregardless so I think there is something else going on with the 24V that we don't see, or it just advances it so far that it makes it inefficient. But nobody seems to know.

[CUMMINSDIESELPWR]

someone would have to crack the firmware on the computer on top of the vp44 and figure it out.

[bbraden]

So who all has a potentiometer IAT? I would think that those people should be able to scroll the IAT through all of its settings (say 0 degrees F to 140 degrees F) and see what the timing sounds like. Has anybody tried that? Going down the highway with a load on (say a trailer on flat ground) and then scrolling the IAT should give you a pretty determinable sound.This has probably been covered already, but my thoughts are that we could use the potentiometer for an "on the fly" timing adjustment. When idling, set it at a high temp, retarding timing for no knock. Then, when up to cruising speed, set the temp low for timing advance and better mileage. I know that goes against the original premise of the IAT and fooling it to retard timing for better mileage, but the whole thing confuses me...

[Mopar1973Man]

That what I've been doing... I've got a 5K rheostat down by my transfer case and been going through all the different temps looking for a high spot. But the colder I get the lower the MPG's get. If I flip on my high idle switch (IAT 13*F) then it drop considerable.But I find for the MPG's its best around 130-140*F range...

[bbraden]

Can you hear a significant difference when you set the temp low? With my Super X pump (advanced timing via higher injection pressure) I can definitely hear the difference in timing rattle at low temperatures.

[Mopar1973Man]

Combination of the Edge Comp and low temp mine rattles like there is a mechanic stuck in the bottom end with a sledge hammer trying to get out... Once I get some boost pressure built up the timing starts retarding and it dissappears.Or just turn the Edge Comp off and it goes away.

[bbraden]

That sounds exactly like mine with the Super X at anywhere below about 35 degrees. Except I can't turn the timing off. I was thinking either timing retard via the IAT sensor, or higher pop injectors that would put the event a little later in the compression stroke.

[bbraden]

I had a new thought on this a little while ago, and ya'll tell me if I'm way off.In a perfect world, the ECM on the 24v would advance timing (at low temps) just to the point that it offsets the timing requirement from the actual cold temps. This would basically create an even playing field between cold temps and hot temps because the computer compensates timing for the temperatures.Enter emissions crap. So how would the engineers at Cummins keep this thing making less emissions when it gets cold? Well... I figure they would do it about the same as they have done on all the other new diesels coming out - throw more fuel at it. (Richen mixture makes less NOx particles??)In the simplest, perfectly operating diesel engine, throwing more fuel at it creates higher RPM, as long as we're talking about an unthrottled engine. If you want to throw more fuel at a diesel without creating higher RPM, the only way you could acheive that is if you make the engine work against itself somehow. By introducing way too much timing advance, you create cylinder pressure sooner in the compression stroke, putting extra compression on the pistons BTDC, and basically working against the engine, almost like creating negative horsepower (in a sense). That's the only way that you could introduce more fuel without creating higher RPM's. Don't you normally have to raise the idle on a 12v when you advance timing? To test this, I think we could use the load function on the scanguage. (1) Warm the motor up to operating temperature. (2) Take a load reading at idle with IAT reading 140 degrees. (3) Take a load reading at idle with IAT reading 20 degrees. (Of course the grid heaters could not run as that would create excess alternator load.) If that doesn't read any difference, it might require a dyno load applied at a certain RPM and then see if the load reading changes. What do ya'll think?