While I was researching for this thread...

Let's Talk Injection Timing, TQ, HP, & EGT...
https://www.ford-trucks.com/forums/731480-let-s-talk-injection-timing-tq-hp-and-egt.html

... I came across some information on Biodiesel that I decided to post as a separate thread because of the increasing interest in alternative fuels and additives to regular #2 Diesel.

A good general reference on Biodiesel's lubricity, emissions, and other properties is here...

What are Biodiesel's Advantages?
http://www3.me.iastate.edu:80/biodiesel/Pages/biodiesel8.html

... and if you click on the Digressions tab at the lower left, you'll see a number of tech papers that discuss Biodiesel and diesel engine combustion in general.

The thoughts discussed here relate primarily to fuel cetane number, volatility, flash point, and other combustion characteristics that control the shape of the cylinder pressure versus time curve, like the curve shown in the injection timing thread, and also repeated here for easy reference. This pressure-time curve, and the location of its peak relative to TDC crankshaft position, is key to understanding how various types of fuels and DFAs effect HP and mileage.

The effect of higher cetane number is to shorten the ignition delay interval between when the fuel is injected and when it actually ignites. The effect of shortening this period is to decrease the amount of fuel that is prepared to burn at auto-ignition, so that when auto-ignition actually occurs the combustion event will be less severe. This results in a lower rate of pressure rise and less engine noise.

For a given amount of injected fuel, it's the area under the pressure-time curve that determines the Mean Effective Pressure, MEP, and as discussed in the injection timing thread, it's the MEP that determines the TQ & HP. Also discussed is the requirement that the injection event be correctly timed so that the curve reaches a peak at a crankshaft position of about 20* ATDC.

The reference curve shows how adding a DFA to improve the cetane number of regular #2 Diesel can increase the area under the pressure-time curve, and smooth it out, which results in less combustion noise. The cetane numbers of Biodiesel are generally between 46 and 60 compared to regular #2 Diesel fuels which range between 40 and 45.

So based on this, I'd expect Biodiesel to produce a broader shaped curve, which would increase its area, but due to the lower BTU content the curve would have a lower peak value, which would reduce its area, and since mileage is lower with Biodiesel, the net effect of higher cetane number and lower BTU seems to be a slight reduction in area.

I'm wondering if Biodiesel shifts the peak of the curve (and thus the effective timing) enough so that tweaking the injection timing to optimize it for Biodiesel might improve mileage? Also, the widely reported reduction in engine noise with Biodiesel is often attributed to less injector noise due to Biodiesel's higher lubricity, but I think it's mostly due to less combustion noise due to Biodiesel's higher cetane number.

Due to Biodiesel's low volatility, there's an increased risk for contamination or dilution of the engine oil. The mechanism for the dilution is the same as for dilution with the lower volatility compounds in regular #2 Diesel, which are slow to vaporize after injection into the cylinder. Some of these low volatility compounds will be deposited on the cylinder wall where they can be swept down into the crankcase by the normal scraping action of the piston's oil control rings. Biodiesel consists almost entirely of these low volatility compounds, whereas regular #2 Diesel has a much smaller amount.

So in summary, it seems to me that DFAs can potentially increase HP and mileage by increasing the area under the pressure-time curve, and possibly by effectively adjusting the injection timing by shifting the peak of the curve to a more favorable crankshaft position. Another way of explaining this is that roughly only 1/3 of the fuel heat energy is converted into HP, with 1/3 absorbed by the coolant, and the remaining 1/3 going out the exhaust. By increasing the pressure-time curve area and shifting its peak, a DFA might slightly increase the amount of heat energy converted into HP, while reducing the waste heat energy by a corresponding amount.

 

Don't have time to digest it all now, but I'm signing up so I don't miss this one.

 

Gene please keep your hat on so all this info don't escape. Good point on the cetane and the noise level of motor, i think it's both, the btu and lub for reduced noise. Bio is quieter. Cetane levels do make a diff. My truck loves B5 B10 With Dipetane, also were we live you can by 47 cetane at BP station. Get back to your discussion is there any way you can hook up your lap top to the motor and play with this inj timing to get this power out of Bio. There has to be a sweet spot.

 

How much of an adjustment in timing do you think it would take to adjust to the bio? There's a blue CPS out there that's supposed to have a different timing (don't remember if it's advanced or retarded, or by how much)

I'll assume your graphs are based on B100 vs D2. How much steeper do you think the Bio curve would be with a B20 mix? I've noticed the quieter engine with with B20, but if it's based solely on combustion characteristics my simple mind tells me that the D2 curve would only lessen it's slope by 20%. I would guess there is some ideal slope representation in your graph that would give the quieter engine performance with optimal fuel burn and MPG's.

Any chance of you figuring out for us what mix Bio would be best to run in these engines?

 

That graph compares untreated #2 Diesel (red curve) with #2 Diesel that's been treated with the Amsiol Cetane Booster product (green curve), and I borrowed it from their web site.

I suspect that B50 and higher would have an even higher cetane number, and thus an even broader shaped pressure-time curve than the green one, and a peak that's somewhat more advanced in time, so that possibly the timing might have to be retarded a little for optimum performance. On the other hand, OEM timing might be slightly retarded from optimum due to emissions requirements, and in that case advancing the pressure peak with a cetane booster would bring the timing closer to optimum.

I can't give any specifics regarding timing, I no longer have a PSD, and I never got around to trying Bio before I traded it for my CAT C7. I've been thinking of trying Bio in my CAT, but for now I'm just using a hefty dose of Stanadyne Performance Formula.

 

Yea I know you've traded up, and I wish you better luck with your C7 than I had with a 3206, but I kinda figured the ignition & timing principles would be the same for autoignition diesels. I did talk to a guy running a CAT in a big truck a few years ago that was using B20. He really liked it. Said it blew all sorts of crap out his exhaust stack for the first few tanks. He figured it was just cleaning things out. Didn't make sense to me at the time, but when I ran it in my farm tractor I blew all sorts of crap out my pipe for the first tank. Ended up taking a power washer to it to clean it up. After the first tank no more junk out the exhaust pipe.

If you're still going to hit that campground in Weatherford later and need to look at a stock engine for any data for your posts shoot me a PM. I'm about an hour away and will volunteer my truck for you to play with if you can do it on a weekend.

 

This is "Gene", and I'm not even close to being in the same league as "Jody", and if you were foolish enough to let me mess around with the timing on your PSD (assuming I could figure out how), it's likely to wind up like Jeremy's! I just try to figure out how things work for the fun of it, not actually try to make them work.

As a rolling stone, not only do I gather no moss, but bio is hard to find, and that's the main reason I've never tried it.

BTW, I was in the Cowtown RV Park just a few miles east of Weatherford from March 16 to 30, and I visited the Dr Performance shop several times. A guy there said he had a CAT C7, and towed heavy, long, and hard with one of their CAT C7 pressure boxes with no problems, but then he was trying to sell me a box! Next time I'm at Cowtown I'll let you know.

 

I wasn't thinking of actually adjusting anything, but I do have an AE and a 7.3. I was thinking you might be able to gather enough information for another one of your posts.

As for Jody, no disrespect, but I'm one of the strange few individuals who is satisfied with stock performance.

 

Just to add a small tid bit to your info Eugene. The last fuel analysis I did for a local school district running 20% biodiesel. The cetane # on the report was 50.77. considerably higher than the average ULSD level.