Boost vs compression ratio calculator11/28/2023 Once it begins making smoke, you have crossed that line, and are pushing incompletely burned fuel out the pipe. Adding #2 up to that point will yield more power. Adding more fuel (such as ethanol) will only increase power up to the point it uses all the remaining O2. Anyone trying this, any truth to it?If you aren't making smoke, you are burning all the fuel. He claims it burns the fuel more completely producing more power. Was just talking to a guy that says ethanol inj will have a dramatic impact on fuel economy. None of this takes into consideration the mechanical limitations of the platform involved (the point an efficiency increase start breaking things). On the charge-air side, you will hit a wall on compressor efficiency, at which point, it will fall off exponentially (the value of the fuel input compared to the output power depart very quickly). X amount of exhaust gas energy will produce X amount of charge-air energy. The principals, function and science are very simple. None of this will change the "efficiency" of a charge-air system. Most often, the ROI (Return On Investment) is far beyond what you will actually ever achieve. Mixing alternative fuels into any engine may have an economic advantage, but you'll have to consider all the costs involved. Also, consider that almost all fuels (capable of being used in an internal combustion engine) other than #2 Diesel have a significantly lower BTU potential (translates to less "efficient"). Adding more/other fuels until the combustion process uses all the available O2 available can be advantageous from an economic standpoint (if the alternative fuel is significantly less expensive than the primary fuel), but offers little more than that. Propane injection only adds to volume of fuel(s) already in the combustion. Please tell me can you make up for the loss of efficiency with the lower CR by introducing propane injection? Thanks.No. What effect does CR have on crankshaft harmonics? PS - Here's a question for the thinkers out there. They don't because of increasing durability issues with increasing CR. If a higher CR was a better compromise (for efficiency), they'd all have a higher CR. Certainly, tractors, OTR diesels, marine diesels and so on are also designed with efficiency in mind. Tractor, industrial and marine diesels are usually run at high load for extended periods, and tend to have a lower CR for improved durability. The marine 5.9L Cummins runs with 15:1 CR. The Duramax/PSD/Cummins ran at 17.5-18:1 (the LMM Duramax is now at 16.8:1). Its 3.0L DI siblings are, on the other hand, just over 18:1 CR.ĭiesel farm tractors with DI diesels (of those I've seen the data for) run at anywhere between 15 and 18:1 CR. It too is an IDI engine that has 20:1 CR. I did a short tech piece on the Isuzu C240 I-4 2.4L diesel recently. So, a higher CR was an IDI cold start compromise. A DI (Direct Injected) diesel (like the current Duramax, Cummins, PSD) starts well cold at a lower CR. The precups/prechambers cool the charge on a cold engine. And fuel economy is up 15% over the original GM 6.5L TD.įor an IDI (InDirect Injected) diesel to produce clean cold starts with short glow cycle times, and to produce fewer cold start emissions, the CR has to be somewhere at/above 20:1. Which is why I elected to get my new engine with 18:1 pistons. With a bit more fuel/air, the power will be nearly the same, but still with less stress on piston crowns and skirts.Ĭompression ratio is a compromise - higher CR results in higher theoretical efficiency, but at the cost of longevity - and sometimes it's too high, such that decreasing it raises efficiency. But this will decrease BMEP (Brake Maximum Effective Pressure) in the cylinders, which reduces piston head pressures and does, in fact contribute to longevity at the cost of a slight decrease in efficiency. The fuel-air mixture has, however, the same energy content, but it will be slightly less efficient than at the higher compression ratio. Without more fuel/air, with the larger volume, the density is decreased. Same DCR + Same A/F Density+ more A/F Volume = bigger bang per power strokeNicely said! Although the fuel-air "density" isn't the same, but the fuel-air ratio is - unless as you mentioned, more fuel and more air is introduced. Even though the dynamic compression ratio remains the same +/-, the lower height of the 18-1 piston crown creates a larger effective combustion chamber volume, which is now packed with the same density of air/fuel as the smaller area that was provided by the stock piston compression height. Add a corresponding amount of additional fuel and you have a more powerful combustion event. More boost = more combustion O2 avilable.
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