The fuel I've been picking up finally went to winterized diesel and the cetane really jumped in the last few tanks. Found that you have to retard timing a wee bit to gain the edge again. A lot of people consider the air temp like I did too thinking cold air will take more timing to ignite the fuel. Actually the cetane has more weight that air temperature. Even though my morning run is at about +10°F my IAT is about 62°F. I tried advancing timing found the MPG dropped hard to 17.6 MPG. Now after retarding jumped back to 19.5 MPG.

 

This follows the same rules that the MPG of the Mopar1973Man High Idle. Just I'm programming a tune to take advantage optimal timing. Still the MPG switch helps for during your warm up mode till the Quadzilla goes into full run mode.

IAT really isn't even much a factor for cold weather in the when IAT is floating the 60's degree range. Even with my thermostat at 180°F and intake temperature been fair consistent at 62°F in the morning. EGT's haven't changed really. With the cetane rising up in Idaho and winterized diesel fuel for sure in full swing now the BTU's content are at the there absolute lowest point. 

 

The ASTM Standard Specification for Diesel Fuel Oils (D-975) states, "The cetane number requirements depend on engine design, size, nature of speed and load variations, and on starting and atmospheric conditions. Increase in cetane number over values actually required does not materially improve engine performance. Accordingly, the cetane number specified should be as low as possible to ensure maximum fuel availability."

 

 

Basically, cetane makes the fuel capable of igniting in colder temperature with little heat. Then the stock ECM we found out jumps +3° to +4° advancement of timing when the temperature falls below +80°F which is why the winter MPG on our truck is rather poor. Timing should slightly retard allowing the fuel to do its job properly. Now after thinking about it this is what my MPG mode of the switch does is trick the ECM to believing its 143*F in the intake. This prevented the timing advancement from occurring and promoted better MPG's with winterized fuels. 

 

Now back to the Quadzilla you going to want to retard your timing at least 1° to 2° worth. Test and watch your MPG numbers. All these years trying to keep MPG numbers up through the winter and using trickery or foolers to keep things on track. Now doing the study work to find out Mopar1973Man MPG mode will still aid in warm-up timing and keep the ECM down where it belongs. Once the Quadzilla takes over you tune should cover these changes. I highly suggest you create a "Winter Tune". Like I'm set up for 170°F warm-up mode on the Quadzilla so the MPG switch still keeps the ECM in check during this warm-up phase. The high idle feature works great in kicking in when firing up after a shortstop like breakfast in the morning.

 

The 17.6 MPG was with 20.8° to 21° of timing at 2k RPM cruise state. The 19.6 MPG is now at 18.7° to 19.0° timing at 2k RPM cruise state. Also shifted down -1° on my MAX timing across the board. 

 

Edited November 18, 20186 yr by Mopar1973Man

I dropped my timing 2.5* a few weeks ago after noticing a drop in MPG's. 

3 minutes ago, BBHD said:

I dropped my timing 2.5* a few weeks ago after noticing a drop in MPG's. 

 

What is your 2k RPM timing at cruise set for?

18.5 right now. I'll run it on my trip back to Colorado at the end of the week to see if it's still where I want it. I average 2.5-3k miles a month. Every other week I travel back and forth between Colorado and New Mexico. 

49 minutes ago, BBHD said:

I dropped my timing 2.5* a few weeks ago after noticing a drop in MPG's. 

 

Interesting. Looking forward to the results

So far things are looking good. 20.1 CO to NM last Tuesday. 

I don't recall where I read it, but I did read that fuel that has the Cetane chemically altered doesn't have the BTU change, which does make sense. 

 

I've also read that many places now just treat #2 as their winter fuel, instead of mixing it with #1. So the Cetane may increase, if they chose to, but the BTU's don't have to decrease. 

 

I'll run a Cetane booster for a few tanks a year when I want the benefits of improved starting and low temp/pressure combustion. 

6 hours ago, AH64ID said:

I'll run a Cetane booster for a few tanks a year when I want the benefits of improved starting and low temp/pressure combustion. 

 

Could you expand on that a bit? What brand? How much? How often?

Edited November 19, 20186 yr by notlimah

9 hours ago, notlimah said:

 

Could you expand on that a bit? What brand? How much? How often?

 

 

The main time I use it is for elk hunting. I spend anywhere for 7-21 days in the woods and the truck never gets above 20 mph, and 1/2 the miles are all downhill. So I want to help improve that low temp and low load combustion, the starting help never hurts at 8K feet in the cold either.

 

I use Amsoil Cetane Booster and enough for about a 3-4 point increase. Nothing huge, but hopefully helpful.

 

If we’re going to be in the woods in the winter I’ll also add a little, but that’s not an annual thing like hunting. Sometime it gets added for Christmas tree hunting, yurt trips, or hot springs trips. 

 

https://www.amsoil.com/shop/by-product/fuel-additives/diesel/diesel-cetane-boost/

 

 

Edited November 19, 20186 yr by AH64ID

15 hours ago, AH64ID said:

I don't recall where I read it, but I did read that fuel that has the Cetane chemically altered doesn't have the BTU change, which does make sense. 

 

Never seen this before. When you change the cetane of the fuel your basically changing the API gravity of the fuel and making it lighter. Which is going to move the vertical axis to the right as high cetane. When you look at the scale provided by ASTM labs it rather difficult to keep high BTU content at the same time of having high cetane levels. The horizontal axis is the cloud point of the fuel and how soon it will gell up. 

 

 

 

I just don't see it possible to chemically alter the cetane and BTU value high. impossible to change the API gravity of a fuel and have if both heavy and light at the same time. Just for point of reference right around 115k BTU is where super unleaded starts. 

11 minutes ago, Mopar1973Man said:

 

Never seen this before. When you change the cetane of the fuel your basically changing the API gravity of the fuel and making it lighter. Which is going to move the vertical axis to the right as high cetane. When you look at the scale provided by ASTM labs it rather difficult to keep high BTU content at the same time of having high cetane levels. The horizontal axis is the cloud point of the fuel and how soon it will gell up. 

 

 

 

I just don't see it possible to chemically alter the cetane and BTU value high. impossible to change the API gravity of a fuel and have if both heavy and light at the same time. Just for point of reference right around 115k BTU is where super unleaded starts. 

 

My understanding is that chart applies to fuel that is refined differently, not chemically changed. 

 

It makes more sense to me that chemically altered vs refining will have different effects. 

Kind of like dropping gasoline in diesel or waste oil. Still it chemical altered but you can still measure the API gravity change. Really common for WEO and WVO running that are chemical altering fuel to meet the needs fo the season and you can still measure a chemical altered fuel with a API gravity. Hence API gravity goes up the BTU's go down. Still if you can measure API change then there a cetane difference. If there is no API gravity change then cetane didn't change. 

 

Edited November 19, 20186 yr by Mopar1973Man

2 minutes ago, Mopar1973Man said:

Kind of like dropping gasoline in diesel or waste oil. Still it chemical altered but you can still measure the API gravity change.

 

I wouldn't call that chemically altering, that's mixing. 

Still the fact remains API gravity MUST change to alter cetane. Being Cetane and BTU are directly related you can have high cetane and high BTU's together scientifically impossible... Like the most common PPD used in US diesel fuel is Xylene typically at the 8% to 12% levels in winterized fuels. Xylene is also used in some cetane boosters as well again there is all kind of chemicals on the market to change the fuel. Still even after the adding of these chemicals, you can still measure a change in gravity. 

 

BTU's come from the fact of long carbon changes in the fuel long the chain the more BTU's. Cetane is the ability to ignite easily in cold weather. The only way I know how to do that is cut the carbon chains shorter. When this happens the API gravity can measure the density of the fuel now because the carbon are no longer long then have been shorten. As you make longer carbon chain length you start heading towards oils and high BTU's as you shorten the chains you start going to light distillates like gasoline which have lower BTU's. This is a primary reason why gasoline has a high API gravity and lower BTU's content that diesel. 

 

Edited November 19, 20186 yr by Mopar1973Man

Absolutely, but the article I read was talking about how additives change the cetane/pour point vs different refining. 

 

Additives aren't making #1 out of #2, which is why it doesn't have the same effect. 

 

I'll have to see if I can find it again. 

who wants some...

How much of a drop did you see with winter fuel before you made any changes. I went from about 17.7 to 16.4 or 16.6 in the two weeks or so. Stock truck with bhaf.

Typically for myself it about a -2 MPG loss. I'm floating at the top end of 18.1 to about 19.0 MPG for the winter.

Alright good. I was just wondering if it was just the winter fuel or something going wrong on my truck last year didn't effect my fuel mileage as much but i am driving more this winter too. Thanks you sir. 

Don't forget about all the increased parasitic drag in winter too. Dense air, colder grease, colder fluids, and such.