How much does cold advance change timing?

[BrianX128]

So as the title states is there a set degree change? If I'm at 2* and it kicks on does it go to 8*?

I'm just wondering as while re wiring my manual high idle in to my overhead console I was thinking if I had a switch that also kicked the cold advance on and that was say.. 9* for power and towing but with the switch off it stayed at 4* or something for fuel economy?

Maybe it changes it by 14* or something absurdly not feasible and that's why no one has done this, but I've never definitively heard how much it effects timing so I figure I'd ask.

 

[bbjordan]

I've read anywhere from 3 to 6 degrees advance. The last time I checked it on my 6.9, it was a little over 4*.

 

[Golden Helmet]

I'm curious to know this too. I have mine unplugged because it makes my engine run really rough between 700-900 RPM (like a gas engine with a bad vacuum leak), I've always wondered how much extra timing it takes to make that happen.

 

[pelky350]

From what I've read before it it's between 3-6 degrees and varies between pumps, and fuel pressure in, it does other stuff internally to the pump that makes driving with it on undesirable also. I'm set at 5' right now and with it on it messes with my 1500rma and above acts all jumpy. Mines on a switch with the high idle

 

[BrianX128]

I found an old thread on here from 2012 where Mel said factory spec was to advance the timing by 3* but it depends on the fuel pressure at the lift pump. I'd assume the way that works is the higher the pressure into the pump the more the advance would allow in.

I might try and wire my last toggle switch on my console into the cold advance directly [after the diode used in the high idle toggle switch mod I have that a lot of us have done], and see what it does. I have a good isspro pyro so I can make sure I don't nuke the engine and try pulling hog back hill's giant grade in it with it on once and see if it does any thing.

Unless anyone comes on here and says awful idea by when I get home from work tomorrow lol

 

[Macrobb]

Honestly... if you *gain* power using the timing advance, advance the base timing by that amount - it means you are retarded.
Generally, you'll see good power right where you see good fuel economy, because that's where the engine is fighting itself least and using the least fuel to do so.
Which also results in lower EGTs and coolant temperatures...

 

[79jasper]

^ Yes, yes, precisely.

Sent from my SAMSUNG-SM-G935A using Tapatalk

 

[BrianX128]

xc_hide_links_from_guests_guests_error_hide_media

Well I added the switch since it was too easy not to and I wanted to see what it did. This was just testing it in the driveway. I thought it was pretty interesting how changing the timing by hitting the advance toggle switch like that changed the rpms up so much the way they did without me touching the throttle at all. Even in the last example, I held the throttle at 2350 roughly while re-watching the video and when I hit the advance toggle it revved it up to 2800. I did this again after taking the video and it did the same thing and held it at 2800. Never moving the throttle.

Then I went out for a road test, and basically my smartphone screwed me and recorded nothing valuable, just the first 5 minutes of me driving to the nice flat spot where I could hammer it through third and fourth and see how it acted. It definitely helped. With the switch on, I could feel a good bit more pep in the engine between 1500-2500 rpms. Up until 1500 it felt exactly the same but the moment the fuel was really getting pushed in there it felt good. egts seemed to stay the same. Makes sense to advance the pump some more and not keep the switch, but I guess as long as I watch my gauges I'm not gonna blow anything up, its just stupid basically. Not like if I don't like the timing I can't change it back as I still have the center punch mark from the only time I ever advanced my timing, I just hate even looking at my injection pump. Ever since my #2 line broke (with clamps) and I had a fun time changing that and fuel everywhere, I just kinda let what seems happy be.

 

[bbjordan]

Honestly... if you *gain* power using the timing advance, advance the base timing by that amount - it means you are retarded.
Generally, you'll see good power right where you see good fuel economy, because that's where the engine is fighting itself least and using the least fuel to do so.
Which also results in lower EGTs and coolant temperatures...

I get what what you are saying here, but just a couple of points...
- He is not retarded. His engine timing is retarded. (Yes, I am being a smart-ass. )

- Peak Torque is where the engine produces the best fuel economy. Torque is a measure of the efficiency of the engine. Peak Torque is where it is most efficient.

Power is the product of Torque x RPM. Essentially Work/Time. If you read HorsePower vs Torque graphs you will see they always cross at 5250 RPM. IDIs rarely go above 5250 RPM, so you are not incorrect. It's just my OCD kicking in. lol

 

[Macrobb]

- Peak Torque is where the engine produces the best fuel economy. Torque is a measure of the efficiency of the engine. Peak Torque is where it is most efficient.

However... that also depends on torque divided by fuel used, especially when dealing with turbos.
a NA engine, yeah, you can use Peak Torque for that. According to the graphs I've seen, torque peaks at around 1400-1600 RPM. That's a reasonable number for effeciency.

On the other hand, with a turbo, I make /more/ torque at 2800 RPM than I do at 1400, by a great deal. So, what, is my engine most efficient at 2800 RPM? Or is that simply the crossing point where the turbo shoves the most air into the cylinder and where the IP fueling curve meets?

 

[bbjordan]

On the other hand, with a turbo, I make /more/ torque at 2800 RPM than I do at 1400, by a great deal. So, what, is my engine most efficient at 2800 RPM? Or is that simply the crossing point where the turbo shoves the most air into the cylinder and where the IP fueling curve meets?

Yes to both.
Your engine, now turbo charged, runs more efficiently at 2800 RPM. Even if it produced the same torque as at 1400 RPM, it would produce more power because of the RPM multiplier effect.
You are probably right about the fueling curve. I think it does drop off rather quickly after 2800 RPM. Mel, or one of the other pump guys would know. Turbo might also be getting out of its island of efficiency.

Gotta love turbos, eh?

 

[chillman88]

I might try and wire my last toggle switch on my console into the cold advance directly [after the diode used in the high idle toggle switch mod I have that a lot of us have done], and see what it does. I have a good isspro pyro so I can make sure I don't nuke the engine and try pulling hog back hill's giant grade in it with it on once and see if it does any thing.

Unless anyone comes on here and says awful idea by when I get home from work tomorrow lol

I realize it's already done but I actually did that intentionally the other day. Technically I just unplugged the high idle and jumpered the temp switch...

I know my timing is retarded and I had to tow my buddy's Dakota an hour each way. Made a huge difference for me. I bumped my timing up a hair after that and I'm done messing with it until I get a timing meter lol

 

[79jasper]

Just remember, too much advance will burn the tips off the glowplugs.

Sent from my SAMSUNG-SM-G935A using Tapatalk