Is There Such a Thing As Too Much Cetane ?

[MrMarty51]

I try to fuel at the Cenex station that has the Road Master Fule. This fuel is suppose to be like fueling with premium on a gasoline powered vehicle. Adding some performance with the higher cetane level.
I guestimate how much of the Stanadyne performance formula to pour in before fueling, this also adds more cetane to the mix.
Is there a point to where there can be too much cetane ?
Not knowing how much cetane is in the Cenex fuel There really is no base to start with on that formula.

 

[MrMarty51]

BUMPAROO

 

[dbrannon79]

I have wondered this too. not knowing what's in the fuel already not to mention each batch is made with different amounts. they just "try" to keep in within their own spec. different brands of fuel use different standards, especially with "unbranded" fuel like Citgo and others there might not be any standards.

 

[Will L.]

In short- yes.
but you calling that fuel supplier and getting the details is the only way you are gonna find out if you are pushing it to far.

This is the hardest part of diesel fuel to explain. You can do a days worth of reading from good sources and still be confused.
This is because there is a product called cetane and it is also a rating of burn rate.

The more cetane product meant the ignition point is delayed more, altering flash point and therefore burn rate as well. This also means it changes the btu or overall energy in each gallon of fuel. In the way back machine of yesteryear, they added more or less cetane and it made these changes, so they called it the cetane rating. Later it was learned there is like 6 things that all balance the teeter totter. So if they knew the details then- that name would not have been chosen. So the physical product and the effects of it agree at one point, are counter to each other on other points.

Adding the cetane boosters is like mixing in a little gasoline. You will get a feeling of more power. But its like a gas engine vs diesel. More hp, lower torque and lower mpg.
There is simply less btu (energy) in fuel with higher cetane.

 

[Will L.]

Different batch of the fuels is always more stable in crude. Just nature of the beast.

 

[MrMarty51]

So much like the lead that was once in our gasoline.
The more lead, the slower the burn/combustion in the cylinders. Giving the pistons push farther down the stroke.
Now I guess I will need to call the local Cenex and see if they have a printout of the chemical composition of their Road Master fuel, and, long as I am attit, get it for their plain old diesel fuel too.
I would think that there would be cetane in the pump grade of diesel.

 

[dbrannon79]

I found this tid bit of info on cetane in our diesels. it talks about adding gas but gives good info on how cetane works.

Mixing Gasoline with Diesel

My wise old mechanic who has worked on Mercedes for years told me that if I put one gallon regular gas to a diesel tankfull after about every four tanks that it would perform essentially the same job as a fuel injector cleaner at a fraction of the cost. I would like to hear a […]

dieseldatabase.com

 

[Will L.]

Yeahhhh....
They are not going to give you a print out. Your basically asking for McDonalds secret sauce recipe.
If you contact them with the info from stanandyne they might tell you an estimated et result or just say Yes/No if you should run them together.

 

[THEFERMANATOR]

Extra cetane won't hurt anything. Cetane is the rating of how quickly a fuel ignites. Higher cetane means faster ignition, lower cetane equals slower ignition. Unlike in a gas engine, the faster ignition isn't a problem since fuel is directly injected into the cylinder at the time combustion is wanted to occur where as in a regular gas engine the fuel is in the intake charge that fills the cylinder. The higher cetane can give a slight bump in power to an average diesel engine, but were talking maybe a few percent at best(most likely a fraction of a percent). There are race diesel fuels out there with cetane numbers in the 70+ range for engines that need it since they are injecting so much fuel so quickly that they can actually cool the cylinder off, and put the flame out, but this is for very specialized diesels operating under extreme conditions.

Now to go off topic, but I seen it brought into the conversation above in comparisons. Higher octane fuel does NOT make more power. The ONLY way that going to a higher octane fuel could make more power is if the engine setup requires more octane to resist detonation in order for it to run at optimal timing to make peak power. Otherwise running higher octane fuel simply lightens your wallet faster. And lead was used primarily as a lubricant but it also worked as a cheap octane booster. Adding lead to the fuel adds ZERO HP vs an unleaded fuel. The only way a leaded fuel makes more power is if you need a higher octane fuel than you can buy in unleaded.

Now E-85 DOES add power as it carries oxygen in it increasing the amount of oxygen in the cylinder. Engine Masters just did an episode on this to dispell all of the myths surrounding octane and power. There fairly high C/R test engine made the same exact power on 87 as it did on 91, leaded 110, and leaded 116 fuel. They also proved that octane has no effect on burn rate as each fuel made peak power at the same exact timing setting and each fuel wanted the same lambda fuel rate(lambda measures true air/fuel ratio taking the different stoich ratios for each fuel out of the equation).

 

[Will L.]

So 100 cetane rating would not hurt with ignition timing controlled engine- I am living in db2 world. Sorry.
And with modern diesels that are di, it still is ok for the new engines.
I will post a video from Bell Performance that sells cetane booster - so they want to sell it and won’t talk about the rare issues that can occur.

How is too high cetane bad for idi with alcohol added fuels? To early detonation in the precup of cetane before full compression is reached. Imagine piston coming up and at 14:1 ratio(really pressures are key but this is easier to explain) - the actual cetane in the fuel ignites. Then as it burns the heavy long chain of the diesel hasn’t lit but now the alcohols ignite and burn as the piston continues up as you get into 18:1 pressures. Finally at the top of the stroke the actual diesel is now burning.
Yes you will get a more complete burn of the fuel in the cylinder so less emissions and less visible smoke. But this burn just occurred several degress earlier in the cycle.
With modern diesels the computer reads the O2, compensates timing, and life is happy.
Does the ds4 get it’s timing retarded by too much O2? If so- great The db2 does not.
Same issue in the idi Ford and Mercedes.

The high cetane simply move the ignition point foreword- aka advancing timing. But also causes flame burn separation. This is a rare issue. It is known best in gasser world in the Hemi engine because the chamber spread is so big. Having the precup has same effect.

So pre ignition is no biggie- a timing bump, right? Why do tractor pulls have a ton more fuel spewing out the stack rolling coal than needed? Heat. All that wasted fuel helps drop egt a lot. On this forum we don’t have the roll-coal climate. But do some reading and you will see one after another person showing lower egt when rolling. Unburned fuel is simply colder than ambient temperature outside. Spraying out an injector it works like an orifice tube in a/c and the pressure differential causes cooling as the fuel absorbs the heat. Then the now heated liquid fuel gets pumped out the exhaust valve and through the turbo taking heat out the tailpipe with it.

Rolling coal in an idi does not lower egt, it raises it. Why? Because you are cooling the precup and stoping the misting of the fuel in the precup when there is too much liquid. Basically the first fuel coming out mists well, but then more liquid fuel sprays on the misted fuel ahead of it and causes it to condense. We need that high sustained heat of the inside of the precup. The way the precup affect the burn of fuel before it burns on the piston top completely alters that event. Same thing with he flame front not burning all the fuel as it goes and leaving nothing behind the flame front. but flashing the fuel in precup and atop piston at same time means you are creating two flame fronts that crash into each other. Light one end of a football field afire and when it is done all will be burned out except maybe little patches. Light both endzones afire and still same grass gets burned. So a complete, even more complete burn occurs. But multiple flame fronts in a cylinder means over heated piston tops.

How did I learn these details? Well, I didn’t just jump from regular diesel to nitro propane without trying middle ground fuel. Wanting to burn all the fuel for every ounce of power while working at an oil/ fuel company where one of the guys in my racing team was a fuel engineer... yeah I learned a bit. Haha.
Yeah if you retard timing a hair- even idi could deal with it.

The funny thing is, more power and cleaner burn the higher the cetane- why is it they mandated ulsd but not cetane a lot higher. I promise you, many tests have been and still are being done. EU requires higher cetane than here in the name of cleaner exhaust. But still only a few points. When they first did it they mandated cetane up at 75. Reasearch why that went away and they are back down at 50 if still convinced no negative effects ever occurs.

Here is a descent description, but remember- he sells the stuff and is not going to talk about some outlayer obscure engine that they don’t even know exists anymore.

 

[dbrannon79]

so with that said on the video, the question is what is the cetane rating our 6.5 idi engines designed for. I would think that the rating the engines are designed for shouldn't be different weather equipped with a DS4 or a DB2 pump. if our specific engine is designed for 40 then there is no need to be adding anything but maybe some lubricant for the pump.

this brings me back to my first summer after I bought my truck. I actually acheived 16 mpg's consistent for about three tanks but as that winter season came in, it has not gotten any better than 14. what I did or didn't do I can't remember, but something is telling me that it was the fuel additives. when I first started driving it, I don't think I was adding anything but diesel. ever since I learned about the need for lubricants I have always been adding something. 2 cycle oil, power service, howes (got the worst mileage with). not to mention that I know I have been over treating thinking a little more was better. I think I'm in to test this theory out, where I have been causing my own mileage loss

 

[Will L.]

Correct, the cetane rating is easily met- cetane ratings were really low in the 80’s. And since the 6.2 met the multi fuel requirements of the military- that means it could run on anything from diesel #1 to diesel #4. Now days you can’t buy diesel that doesn’t have that amount of cetane, or it’s equivalent. It simply wouldn’t pass the emissions standards required since 07. And this is also why the cetane rating thing is a bunch of legal footwork more than practical application anymore.

To raise cetane rating back then, the plant (are you ready for this) added cetane. But they can’t do that now because actual cetane reacts with the heavier molecules and traps sulfur in the fuel. Strip out 95% of the natural cetane then you can separate the sulfur. So now you need a cetane supplement and a replacement. See, real diesel fuel had no additives- none. It was just hydrocarbons.

The numbers required by epa in the fuel standards went up with ulsd projection laws with the exception made for any fuels containing 10% ethanol. It really is like- do you verify your pharmacist is giving you exactly what the doctor said. Not just the name but the actual chemical composition of the prescription. You just have to take it on faith.

See, this is where it turns into chemistry class and gets about insane to follow.
You can not use the cetane scale for any fuels at 10% ethanol because ethanol flash point is lower than cetane flash point at that percentage. I through in snap shot from epa info sheet back in the day when ulsd was still getting worked out.

For those who enjoy a history read about q&a of upcoming ulsd:
But for the rest just scan the one page. This should show you anyone saying cetane boosters for meth fuel is just lying - it isn’t because it doesn’t chemically work that way. It is a term they are using because the public doesn’t understand so they keep misusing the wrong term of cetane. They say (like in that video) you could run 100 cetane. Cetane is a short chain molecular hydrocarbon liquid that is so high in the chart it is almost a gaseous product rather than liquid. Try running 100 scale gasoline or 100 scale nepthane. Your engine would not run. If somehow you got 100 cetane to ignite- your pistons would be under your crossmember. What is higher than cetane-propane. It rates like the richter scale or like a decibel scale — at a factor of 10. So the lowest propane is 10’points higher than the highest cetane. So use the reciprocal. Imagine propane that is 80% propane 20% nothing else. That is cetane. That is what was literally mixed into diesel fuel before sulfur fiasco to get it to burn hot enough to light properly. So now they do different concoctions to get the same effect and usually it is mostly nepthane (key element of gasoline) whenever alcohol isn’t used.

Go back and read old magazines about burning holes in the top of pistons and you will find it only in gasoline engines when ran lean and advanced timing. Figure out when it started becoming a problem for Diesel engines. Even injectors pissing a stream used to just cause a ton of white smoke from unburned fuel. Not anymore.


https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P1000KER.pdf

 

[MrMarty51]

Now that is a lot of mighty good information.
I guess Me adding the Stanadyne performance formula to the estimated gallons of fuel will not harm the engine.
When the tank reads 1/2 on tje gauge, I figure 18 gallons. It usually takes slightly more by a gallon or two.
I try to estimate the additive to the 18 gallons so it should not be over charging the mix.

 

[RI Chevy Silveradoman]

The fueling stations up here in NE show a minimum 40 cetane sticker on the pumps.
Should I be adding some unleaded to it?

 

[MrMarty51]

The fueling stations up here in NE show a minimum 40 cetane sticker on the pumps.
Should I be adding some unleaded to it?

Nnnoooooooooo. No gasoline. Get some diesel fuel additive that has cetane booster in the mix.
I use Stanadyne Performance Formula. There are others I am sure. I just go to the Stanadyne stuff cause theys the ones tnat designed and built the injection pumps.

 

[RI Chevy Silveradoman]

I run power service in every tank. I used to run Stanadyne, but Power Service is easier for me to get.
I thought Will said above to just use some gas? I'm confused now.

 

[Will L.]

If you are taking the time to test the fuel afterwards you could. But you would be adding lube as well.

Just adding the basic stanandyne to that fuel is the easy answer.

If you are fighting for all the power and willing to learn fuel mixing and testing, then you will get more power for less money. But just using the truck normally- my point is really don’t bother spending that much cash for the little gains. But for those who are going to push jt really hard, Maxing out cetane- going to 60 isn’t gonna hurt anything but when it gets pushed over 80 and contains all the alcohols - that is going to have effect on the flash point as well as ignition delay.

 

[MrMarty51]

Reading that one articel, it said do not use gasoline in Your diesel fuel.
They grow counter productive to each other and, it is much drier and will cause an accelerated amount of wear on lift and injection pumps. I imagine on injectors too.

 

[Will L.]

I am giving the short cut info. The simple answer is leave it all alone. Mess with nothing.

If you want to understand it- learn about a distillery tower and how it separates.
Heavy stuff on bottom light stuff up top, all progressively.

liquid cetane is lighter weight than nepthane. Nepthane is the primary component of gasoline. Cetane is more abrasive at its core than nepthane. You have to add lubricants when you add gasoline, just like when you add cetane. When you buy a cetane additive it should have the lubricant additive in it also like the stanandyne does.

Conversely, when you add a lubricant to your fuel- like when I add ATF, you are supposed to add a cetane booster.

This is like adding a turbo to a natural aspirated engine. Just adding more air doesn’t help- you have to add the fuel also. Or adding only more fuel won’t help, you have to add the extra air also.

There is a certain amount you can just shoot from the hip on. But if you are going to do this stuff frequently, you need to learn how to go through all of it. This isn’t the kinda stuff that gets shown on a forum- local or online college corses are the best answer.

 

[MrMarty51]

I am giving the short cut info. The simple answer is leave it all alone. Mess with nothing.

If you want to understand it- learn about a distillery tower and how it separates.
Heavy stuff on bottom light stuff up top, all progressively.

liquid cetane is lighter weight than nepthane. Nepthane is the primary component of gasoline. Cetane is more abrasive at its core than nepthane. You have to add lubricants when you add gasoline, just like when you add cetane. When you buy a cetane additive it should have the lubricant additive in it also like the stanandyne does.

Conversely, when you add a lubricant to your fuel- like when I add ATF, you are supposed to add a cetane booster.

This is like adding a turbo to a natural aspirated engine. Just adding more air doesn’t help- you have to add the fuel also. Or adding only more fuel won’t help, you have to add the extra air also.

There is a certain amount you can just shoot from the hip on. But if you are going to do this stuff frequently, you need to learn how to go through all of it. This isn’t the kinda stuff that gets shown on a forum- local or online college corses are the best answer.

Thats as plain and simple as it gets.
The jug of diesel fuel supllement, somewhere on the jug, it says it will treat XX, or XXX amount of gallons. I always take that number to be the gospel.
I estimate a number in My head about how many gallons of fuel it will take to fill the tank. I know that the gauge is a very long ways from being accurate but, I have that figured into the equation too. If the gauge is near a half of a tank, I know it is going to take about 18 gallons to fill that 30 gallon tank. So then I add in an approximate amount of the additive so that the numbers are real close. I try to not add more than what is recommended so that the additive will always be a little shy. Then I add the two stroke oil on top of that, before pumping in the fuel.
I keep on hand an empty two stroke quart jug, I fill that jug with the fuel supplement and then I have the measuring scale on the narrow side of the jug to estimate the additive that needs to go into a fill up.
It is a narrow clear window with measure marks on each side of the window, in ounces and in metric measure, CC I believe.