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Any kind of cetane boost is bad...

The higher the cetane level the lower the BTU's become so the lower the MPG's become...

http://articles.mopar1973man.com/general-cummins/36-fuel-system/67-diesel-fuel-cetane-rating-and-the-effects

IMHO, the only time you should need a "cetane improver" is in very, very cold climates. Maybe.........a big maybe on that also. Higher cetane theoretically improves/increases the fuels ability/tendency to spontaneous combust under certain conditions. I've never used one. More important in very, very cold climates is an additive that will lower the "pour point" of your fuel so it doesn't gell in your fuel lines and fuel filter canister.30 degrees is not cold either!!!!!!!!! That's for you "Rebels"!!!!!!!

I'd be a Rebel and I agree 30* aint cold. I have had my truck in 0* weather and not had any gelling problems. Granted not for a steady diet at all, but that kind of weather has not given my truck any problems. At one time used Kleen diesel in mine and never saw any differance in the way the truck ran. When I started 2 cycle it imediatlely got quieter and have been using it since. No mpg gain, but quieter. I dont recoend anything that would make the fuel any thinner and the 2 cycle will stay in mine untill it is not mine anymore.

No problems here... I know with the research of local fuels I do not need to add anything more to the fuel...

I never could understand this fully. If cetane makes fuel burn slower it should get better mpg? If 2 stroke oil adds btu's and helps mpg....i am lost

High cetane = Faster burn, early ignition, higher cylinder pressures, lower BTU's

Low cetane = Slow burn, later ignition, lower cylinder pressures, higher BTU's (Better for MPG value)

From the ASTM testing labs...

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 insure maximum fuel availability."

Cetane improvers modify combustion in the engine. They encourage early ignition of the fuel. They encourage premature combustion and excessive rate of pressure increase in the combustion cycle.

Hence the knock cetane boosters produces where 2 cycle oil a cetane reducer doesn't do that.

.Hence the knock cetane boosters produces where 2 cycle oil a cetane reducer doesn't do that.

Mike, remember all the threads on "the other forum" when the '04.5's came out about the 1800rpm rattle/pre-ignition knock??? IMHO, a lot of it was fuel related. As much as some folks like to say the 3rd gens were designed for ULSD,..........I'm really not so sure on that. For one, why all the need for reflashes etc. on trucks???? My "knock" stopped when I stopped using PS+MMO and started using 2 stroke oil exclusively. I had the Edge J w/A on the truck at the time of the change over also. The switch stopped the rattle. The rattle I'm refering to sounds like a "pre-ignition" sound in gassers. It seemed to turn on about 1800rpm. I think it had something to do with the multiple injection events of the 3rd gens and too much cetane in the fuel. Just my humble theory!!

High cetane = Faster burn, early ignition, higher cylinder pressures, lower BTU's

I still haven't swallowed, what your saying hook line and sinker. So I will need some more schooling If we take for example simple engine building for power. High cylinder pressures are highly sought after under the right circumstances. BTU's high or low should be decided at the time of design. And Cummins did that and it seems to me that I read that the 24V was designed for a Cetane value of 45-55 (will see if I can find that again). If cetane acts like octane and inhibits burn. How does it foment early ignition, which is not always a bad thing. A faster burn too early is a bad thing, but a slow burn causes it's share of problems too. Lower BTUs equals less energy to burn, Higher = more energy to burn. That does not always mean MPG is directly related to BTUs for every engine type. Just haven't figured out if the cylinder pressures are high enough to overcome lower BTU rating. After all cylinder pressure = torque.

I still haven't swallowed, what your saying hook line and sinker. So I will need some more schooling If we take for example simple engine building for power. High cylinder pressures are highly sought after under the right circumstances. BTU's high or low should be decided at the time of design. And Cummins did that and it seems to me that I read that the 24V was designed for a Cetane value of 45-55 (will see if I can find that again). If cetane acts like octane and inhibits burn. How does it foment early ignition, which is not always a bad thing. A faster burn too early is a bad thing, but a slow burn causes it's share of problems too. Lower BTUs equals less energy to burn, Higher = more energy to burn. That does not always mean MPG is directly related to BTUs for every engine type. Just haven't figured out if the cylinder pressures are high enough to overcome lower BTU rating. After all cylinder pressure = torque.

OCTANE=ability of fuel to resist "pre-ignition". CETANE=ability of fuel to "spontaneous" combust IOW, cetane and octane are inversely proportional!! Not arguing, just saying!!!

I ran Cetane boost for about 8K miles and developed a nasty knock, stopped using Cetane boost and stopped knocking. I don't feel it was a coincidence as the knock hasn't returned in 20 months, and I stopped using Cetane boost 21 months ago. Well, that's 99% true. I was running a 7 point bump for that time frame and will on occasion run about a 3 point bump, but it hasn't produced the knock. I only do it 2-3 times a year, and only on well thought out tanks. Cetane will help low load and low temp ignition, and improve the quality of combustion in those low load/low temp instances. I used it for the week or so I spend at elk camp where I won't break 20 mph in 300 miles, and never more than 7 miles at a stretch, and it seems to help the motor warm up a little better and mileage isn't effected in that kind of driving. I will also use it for winter tanks where I expect to spend a lot of time idling to keep the cab warm for the kiddo's, i.e back road sledding/camping/x-mas tree hunting trips. It's not always super cold, but idling for a couple hours at 30° isn't the best either, so a little more Cetane is a good thing. One must also consider that the Cetane requirement from Cummins is different for above and below 32°F.99% of the time I am in the same boat as Michael, but there are a few times when it's actually a good idea.Higher cylinder pressure is not always best (think HG), it's just a by-product of additional, or proper, fuel/air/timing. More powerful/effecient motors do have more cylinder pressure, but they also have more emissions from the pressure. It is possible to make more torque with less pressure, it just takes more fuel. The pressure doesn't create the torque, the length and timing of the burn does (more heat (aka energy) being absorbed by the piston and not flowing out the exhaust valve). Additionally higher BTU's means less fuel is needed to make the same hp. So if one Cetane has 120K BTU's it can make 47.15 HP, but another has 110K BTU's and only makes 43.22 hp. If it takes 50 hp to go 60 mph, the Cetane that makes 120K BTU's is burning less fuel per hour, and thus better mileage. On the other side of it, if the motor can push 35 GPH thru the injectors it's also making more power.

Dorkweed, thanks for clearing up the octane, cetane issue.What happens when you buy fuel from a high sales volume outlet, that is .13 cents a gallon cheaper than anywhere else in town. Whenever I fuel there my milage goes to crap. Is this a sign of low quality fuel? In my opinion yes, since there is not enough water in the fuel to detect. Would Cetane booster help in this situation or hurt?Yes the high cylinder pressure, being a good thing comments were more or less with purpose built engines in mind. But still as you pointed out high pressure at the right time, regardless of how it happened is a good thing, as long as the design parameters of the components weren't exceeded.My point being with my '06 with three injector events, may see a benefit from early ignition, especially on the third event. Which as I understand it was to cool the exhaust temps for emissions reasons. If there is a fuller ignition event because of the pre ignition tendencies of higher cetane on the third pulse, the timing could be spot on for an added boost in power. :pray:I'll quit now before I stick the rest of my foot in my mouth.

If you want to modify your timing I would get a Smarty Jr and set it on SW1 TM2, TQ1. That is 100% stock fueling with better timing.

If you want to modify your timing I would get a Smarty Jr and set it on SW1 TM2, TQ1. That is 100% stock fueling with better timing.

This^^^^^^^

--- Update to the previous post...

AH64ID.....

Was it you that posted about this a while back about the 3rd gen timing???? I think you said; or I read somewhere, that right around 1800rpm, the timing on the stock programming of our trucks is "retarded". It then goes back to normal (for lack of a better word) at around 2100rpm. Do you think this could be the cause of the early '04.5's 1800rpm rattle or knock?????

Thinking too much again.

Yeah the way the OEM timing is above and below 2000's it's evident that Dodge want's you to pull hills over 2K rpms. One of the things I want to do with UDC is remove that 2000 rpm power point. I am not sure if it causes the rattle, but I can tell you that changing turbo's eliminated all of my timing rattle, until I added the 6.7 damper (which quieted the engine so now I hear a trace of rattle again).

Dorkweed, thanks for clearing up the octane, cetane issue.

What happens when you buy fuel from a high sales volume outlet, that is .13 cents a gallon cheaper than anywhere else in town. Whenever I fuel there my milage goes to crap. Is this a sign of low quality fuel? In my opinion yes, since there is not enough water in the fuel to detect. Would Cetane booster help in this situation or hurt?

Yes the high cylinder pressure, being a good thing comments were more or less with purpose built engines in mind. But still as you pointed out high pressure at the right time, regardless of how it happened is a good thing, as long as the design parameters of the components weren't exceeded.

My point being with my '06 with three injector events, may see a benefit from early ignition, especially on the third event. Which as I understand it was to cool the exhaust temps for emissions reasons. If there is a fuller ignition event because of the pre ignition tendencies of higher cetane on the third pulse, the timing could be spot on for an added boost in power.

I'll quit now before I stick the rest of my foot in my mouth.

No.. because the problem is that cheaper fuel use heavier doses of xylene and benzene to water down the fuel to make it cheaper. Adding more cetane on top just drive the already high cetane higher making matters worse.

Refer back to the ASTM testing grid. Higher the cetane the lower the BTU's. Give you point of reference gasoline is roughly 110K to 120K BTU's.

Ok, I've mostly been what if'ing with my last couple of posts, just to see if anything would shake out of the tree. :tongue:But I still say that, the logic shown on the graph is flawed somehow, when it's used to to discuss CTD's. If the statement is made that the engine was designed to operate with a cetane value of 45-55. 50 being optimum iirc.Why would operating the engine using 30 cetane fuel, not cause operability / longevity issues. Yes a diesel can operate over a wide range of cetane values and fuel types, but operating any type of equipment outside of it's design parameters always causes problems with operability or longevity.

Ok, I've mostly been what if'ing with my last couple of posts, just to see if anything would shake out of the tree. But I still say that, the logic shown on the graph is flawed somehow, when it's used to to discuss CTD's. If the statement is made that the engine was designed to operate with a cetane value of 45-55. 50 being optimum iirc. Why would operating the engine using 30 cetane fuel, not cause operability / longevity issues. Yes a diesel can operate over a wide range of cetane values and fuel types, but operating any type of equipment outside of it's design parameters always causes problems with operability or longevity.

Actually I would like to correct you...

If the statement is made that the engine was designed to operate with a cetane value of 45-55

Cummins is designed for 40-45 Cetane not 45-55... 50 is optimum for smog reasons not for MPG... For racing apps yes 50-55 cetne is require to have a fuel that can burn fast enough at 4K on the tach. So since 50-55 cetane is so low in BTU content that why most reacing/pulling rigs smoke like freight trains they must over fuel to obtain the power that is lost in the lower BTU's. Like the DieselPower mag has a article on a 1,500 HP engine requires 600 GPH lift pump just to keep it happy then the compression is reduced to 12:1 why??? Because high cetane fuel would pre-ignite so early with 150 PSI of boost it would either blow the head or gasket or start busting pistons. So now getting back to daily drivers like us... I typically see 1,500 to 1,600 RPM's for cruising speeds of 55 MPH so now I need a fuel that burns properly to the RPM and load of the engine. My engine load is typically 10-30% on the flats so a low cetane fuel would produce way more power than a high cetane fuel would. Hence why my MPG's are much higher than most people... Then for fun I called the local Chevron station and got a copy of the fuel data and plugged it into the ASTM grade scale. So when you average it out its about 45 cetane.

Mike, thanks for the schooling. Now I have my pea brain wrapped around what you have been saying.

Here are some excerpts from the owners manual of my 2005. If available in your area, a high cetane “premium” diesel fuel may offer improved cold-starting and warm-up performance.Number 2 Diesel Fuel Specifications Cetane Number - 40 min. (ASTM D613)Number 1 Diesel Fuel SpecificationsCetane Number - 40 min. (ASTM D613)I didn't see it in the manual, but I believe 45 is the min for <32°FCetane is similar to Octane in that there are design specs for a certain number, which is why 30 may have more BTU's but doesn't operate as well based on design specs.

Here are some excerpts from the owners manual of my 2005.

If available in your area, a high cetane “premium” diesel fuel may offer improved cold-starting and warm-up performance.

Number 2 Diesel Fuel Specifications

Cetane Number - 40 min. (ASTM D613)

Number 1 Diesel Fuel Specifications

Cetane Number - 40 min. (ASTM D613)

I didn't see it in the manual, but I believe 45 is the min for <32°F

Cetane is similar to Octane in that there are design specs for a certain number, which is why 30 may have more BTU's but doesn't operate as well based on design specs.

Correct... 30 is too slow of a cetane level to burn properly...

And yes 45 cetane is suggeste for winter use (Below +32*F)

From my cetane page...

http://articles.mopar1973man.com/general-cummins/36-fuel-system/67-diesel-fuel-cetane-rating-and-the-effects

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Cummins Cetane Requirements for 1st, 2nd and 3rd Gen Trucks

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A Cetane rating of 40 is recommended at temperatures above 32 degrees.

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A Cetane rating of 45 is recommended at temperatures below 32 degrees.

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