[ARCHIVED THREAD] - Math is hard (Page 1 of 2)
Posted: 5/7/2013 9:08:46 PM EDT
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Pop quiz, couch commandos.
6x1200cc injectors (rated at 43.5 psi) running 55% duty cycle at peak power. Fuel pressure is 1:1 regulated and indeed 43.5 psi measured at atmospheric pressure (99 kpa). BSFC is .60 (turbocharged, gasoline). Manifold absolute pressure is 215 kpa @ peak power. How much power does it make? SAE flywheel will do. Let me know if you desire any additional information. Go. |
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Warmer. |
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One meeeeeeeeeeeeeeellion. http://www.netbooknews.com/wp-content/2011/09/dr-evil-1-million-dollars.jpg Getting colder. It does have freaking laser beams though. |
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About 600. You ballparkin'? Definitely getting hot now. Well, 628, if you believe the math totally. But there's always variables. Name them! I have freaking laser beams here. I was hoping for at least 2 pages before someone got pretty 4kin close, spoilsport. |
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the tricky part in the equasion that most people miss is that the injectors aren't rated at 1200 when under full boost. Fuel pressure is raising to 60.3 under boost which means those injectors are going to flow roughly 1663cc at that fuel pressure assuming that their flow increases linearly.
So when you plug in your new numbers into the equasion and that seup is good for 1266 hp assuming that your 55% duty cycle the setup is making 696.3hp in current tune. T |
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the tricky part in the equasion that most people miss is that the injectors aren't rated at 1200 when under full boost. Fuel pressure is raising to 60.3 under boost which means those injectors are going to flow roughly 1663cc at that fuel pressure assuming that their flow increases linearly. So when you plug in your new numbers into the equasion and that seup is good for 1266 hp T Easy trap to fall in sir. Pressure is 1:1 rise rail:manifold. I wish it was making that much. Fucker wouldn't be bitching that it felt slow. |
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6x1200cc injectors (rated at 43.5 psi) running 55% duty cycle at peak power. Fuel pressure is 1:1 regulated and indeed 43.5 psi measured at atmospheric pressure (99 kpa). BSFC is .60 (turbocharged, gasoline). Manifold absolute pressure is 215 kpa @ peak power. How much power does it make? SAE flywheel will do. . BSFC should be about 0.35 for a NA engine running at 99Kpa at stoichiometric. So this engine is runninig 7%-10% lean (and won't last long.) Missing information: 1) How many cylinders? (it could be 6, 3, or 2, possibly 1, or you could be dumping all 6 injectors into a plenum and feeding any number of cylinders you want.) 2) What kind of intake? (This can change the result in the range {-15% to +24%} ) 3) What kind of exhaust? (This can change the result by {-5% to +10%} ) |
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1:1 still raises the pressure, just at a 1:1 ratio not a 1:2 ratio like honda kids require to make up for their ecus not being mapped for positive pressure. 1:1 maintains the flow for any given manifold pressure. If fuel pressure was steady state, the injectors would lose flow as manifold pressure rose and rail pressure stayed the same. |
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6x1200cc injectors (rated at 43.5 psi) running 55% duty cycle at peak power. Fuel pressure is 1:1 regulated and indeed 43.5 psi measured at atmospheric pressure (99 kpa). BSFC is .60 (turbocharged, gasoline). Manifold absolute pressure is 215 kpa @ peak power. How much power does it make? SAE flywheel will do. . BSFC should be about 0.35 for a NA engine running at 99Kpa at stoichiometric. So this engine is runninig 7%-10% lean (and won't last long.) Missing information: 1) How many cylinders? (it could be 6, 3, or 2, possibly 1, or you could be dumping all 6 injectors into a plenum and feeding any number of cylinders you want.) 2) What kind of intake? (This can change the result in the range {-15% to +24%} ) 3) What kind of exhaust? (This can change the result by {-5% to +10%} ) The BSFC number is in weight of fuel per horsepower per hour. so, a larger number indicates it is using more fuel per horsepower and running richer. It is at max power rich fuel setting (nobody asked this).  Measured a:f by residual O2 was 11.5:1ish.
It is a 6 cylinder. Not sure what info you want for intake and exhaust. It has a log style intake manifold and a 6-2-1 exhaust manifold. |
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1:1 still raises the pressure, just at a 1:1 ratio not a 1:2 ratio like honda kids require to make up for their ecus not being mapped for positive pressure. It keeps the pressure differential the same. 43.5 PSI in the rail and 10 PSI in the manifold means your effective fuel pressure is 33.5 PSI. If you add a pound of fuel pressure for every pound of boost you cancel it out. Same goes for vacuum, more vacuum will increase the effective fuel pressure. |
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Pop quiz, couch commandos. 6x1200cc injectors (rated at 43.5 psi) running 55% duty cycle at peak power. Fuel pressure is 1:1 regulated and indeed 43.5 psi measured at atmospheric pressure (99 kpa). BSFC is .60 (turbocharged, gasoline). Manifold absolute pressure is 215 kpa @ peak power. How much power does it make? SAE flywheel will do. Let me know if you desire any additional information. Go. The answer. |
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One meeeeeeeeeeeeeeellion. http://www.netbooknews.com/wp-content/2011/09/dr-evil-1-million-dollars.jpg 
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This is not math. This is an exercise in jargon. Rewrite the problem statement in full English sentences. Define your acronyms or don't use them. P.S. - Marisa Tomei = heart throb BSFC is Brake Specific Fuel Consumption. The units for BSFC measurement are pounds of fuel per hour per horsepower. So, this engine uses .6 pounds of fuel per hour to make 1 HP. Fuel injector size is given in cubic centimeters per minute of fuel flow at 100 % injector on time and with a 43.5 psi pressure drop across the injector (fuel rail pressure to intake manifold pressure). It is also given that there are a total of 6 of these injectors total and they are operating at 55 % duty cycle. We are going to assume linear injector flow increase across the duty cycle range and that the specific gravity of the fuel being used is identical to the test fluid used to check injector flow rate. These are the variables the guy with the answer above mentioned. So, we will need to start off with some unit conversion. To get cc's per minute into pounds per hour, we need to divide 1200 by 10.5. That gives us 114.2857142857143. That gives us the 100 % duty flow rate of the fuel injectors (each) but, we are only running them at 55 % duty so, 114.2857142857143*.55 = 62.85714285714287 . Multiply that by the number of injectors and now we know there are 377.1428571428572 pounds of fuel per hour burning through this engine. We also know that this particular engine returns 1 horsepower per .6 pounds of fuel burned per hour. So, 377.1428571428572 / .6 = 628.5714285714287 horsepower. |
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Pop quiz, couch commandos. 6x1200cc injectors (rated at 43.5 psi) running 55% duty cycle at peak power. Fuel pressure is 1:1 regulated and indeed 43.5 psi measured at atmospheric pressure (99 kpa). BSFC is .60 (turbocharged, gasoline). Manifold absolute pressure is 215 kpa @ peak power. How much power does it make? SAE flywheel will do. Let me know if you desire any additional information. Go. 1:1 that doesnt rise with boost? You're doing it wrong. Have fun with that blown block. |
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Pop quiz, couch commandos. 6x1200cc injectors (rated at 43.5 psi) running 55% duty cycle at peak power. Fuel pressure is 1:1 regulated and indeed 43.5 psi measured at atmospheric pressure (99 kpa). BSFC is .60 (turbocharged, gasoline). Manifold absolute pressure is 215 kpa @ peak power. How much power does it make? SAE flywheel will do. Let me know if you desire any additional information. Go. 1:1 that doesnt rise with boost? You're doing it wrong. Have fun with that blown block. The kpa figure was absolute. IOW, 43.5 with the regulator vacuum hose off. Hose gets reattached to manifold after setting pressure. 
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Pop quiz, couch commandos. 6x1200cc injectors (rated at 43.5 psi) running 55% duty cycle at peak power. Fuel pressure is 1:1 regulated and indeed 43.5 psi measured at atmospheric pressure (99 kpa). BSFC is .60 (turbocharged, gasoline). Manifold absolute pressure is 215 kpa @ peak power. How much power does it make? SAE flywheel will do. Let me know if you desire any additional information. Go. 1:1 that doesnt rise with boost? You're doing it wrong. Have fun with that blown block. When did he say it doesn't rise with boost? He simply said at atmospheric pressure it's set at 43.5 PSI, the pressure most injectors are rated at. My truck has a fixed regulator, it's not ideal, but with big enough injectors and some tuning talent, it works. |
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This is not math. This is an exercise in jargon. Rewrite the problem statement in full English sentences. Define your acronyms or don't use them. P.S. - Marisa Tomei = heart throb BSFC is Brake Specific Fuel Consumption. The units for BSFC measurement are pounds of fuel per hour per horsepower. So, this engine uses .6 pounds of fuel per hour to make 1 HP. Fuel injector size is given in cubic centimeters per minute of fuel flow at 100 % injector on time and with a 43.5 psi pressure drop across the injector (fuel rail pressure to intake manifold pressure). It is also given that there are a total of 6 of these injectors total and they are operating at 55 % duty cycle. We are going to assume linear injector flow increase across the duty cycle range and that the specific gravity of the fuel being used is identical to the test fluid used to check injector flow rate. These are the variables the guy with the answer above mentioned. So, we will need to start off with some unit conversion. To get cc's per minute into pounds per hour, we need to divide 1200 by 10.5. That gives us 114.2857142857143. That gives us the 100 % duty flow rate of the fuel injectors (each) but, we are only running them at 55 % duty so, 114.2857142857143*.55 = 62.85714285714287 . Multiply that by the number of injectors and now we know there are 377.1428571428572 pounds of fuel per hour burning through this engine. We also know that this particular engine returns 1 horsepower per .6 pounds of fuel burned per hour. So, 377.1428571428572 / .6 = 628.5714285714287 horsepower. If you are running a SD system, that runs only a single MAP sensor, and you drive to the top of a 10,000 ft mountain, will the engine be running richer,leaner, or the same at the top. And why? |
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If you are running a SD system, that runs only a single MAP sensor, and you drive to the top of a 10,000 ft mountain, will the engine be running richer,leaner, or the same at the top. And why? That depends where I moved on my compressor map. 
If you'd like to know about an n/a engine where the baro pressure drops significantly without being accounted for, it will get richer because there is less pressure to push air past the throttle plate for a given manifold vacuum. Shut it off and restart if you have any driveability issues. They almost all take key on engine off baro readings. |