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Monark injector nozzle results
Took a while to get the Monark injectors built as I was busy with work and other projects. The 760 sat dead for about the past 6 weeks with the injectors out of it. Finally got them put together over the last two weekends. Set all 6 to ~2400 PSI breaking pressure and got them installed Monday night. The results so far have been excellent. The car did not have more power immediately -- without changing anything else, the only effect of the injector nozzles was smoother/quieter running, easier starting, and no smoke at all. Power was about the same. This is relative to new Bosch injector tips, not worn ones. The improvement in running and driveability was noticeable.
Today I got around to replacing the transmission fluid and once that was done I was ready to try putting some additional power down, so I turned the pump up. The major difference with these injectors is they are able to flow much more fuel and produce a huge amount of power with no smoke. I turned the fuel quantity screw in all the way until it bottomed against the protective sheetmetal collar that prevents it from being screwed in too far. With the previous injectors (new Bosch 293s), turning the screw in that far resulted in large amounts of black smoke. With the Monarks, there is still no smoke and the power is remarkable. The car now can smoke the tires through first gear and spin them again in second. In the rain even third gear is dangerous and first and second are almost unusable unless the pavement is perfectly smooth. I am going to cut the collar off the fuel screw and experiment with turning it in further still. Already this change has had the effect of making the car feel like it is 1000 lbs lighter. Highly recommended.
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86 745 D24T/ZF 345k lifted 2.5" 83 764 D24T/M46 155k |
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So these are the 273s correct? Pop pressure is where I set mine to as well. I'm quite happy with the results. Sounds like its time for a bigger turbo!
What do you have in it for a clutch? Jason
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Back again with a '84 760 GLE D24T/ZF SOLD but not forgotten! 1984 760 Sedan, built D24Tic/ T-5 swapped My engine build: http://www.d24t.com/showthread.php?t...t=engine+build T-5 swap: http://d24t.com/showthread.php?399-W...to-quot-w-pics! |
#3
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Quote:
Exhaust currently is the stock size with both stock mufflers removed and one straight-through muffler at the rear. Quite loud, louder than I want it really since it attracts too much attention, but it sounds mean. I think there is still some restriction from the small size of it, since the motor seems strongest from 2500 to around 4000 rpm, but then still begins to run out of breath as you approach 5000. From a rolling start in 1st, most of the time it is a little slow to pick up but then once the tach hits about 3000 it often breaks the tires loose! The M46 has a very short first gear which is part of the reason for that -- I think a taller first would be better, since it runs out of revs very fast in first if you launch hard. Does do nice brakestands now though. Jason, what is the power band on yours like now that you have a big turbo and exhaust on it? Probably a little doggy below 2000 but then strong right up past 5000? I guess you wouldn't know how it is below 2000 at WOT since your torque converter masks that... once you get the manual gearbox swapped in you'll see, these things do require a fair amount of shifting to keep them on the boil if you are trying to move fast. Clutch is still the original one with 122k on it. Seems to be holding up OK for now but its live just got quite a bit harder now that I've turned the heat up on the motor (can't seem to keep my foot out of it ). Trying to minimize the amount of abuse I give it but it's hard...
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86 745 D24T/ZF 345k lifted 2.5" 83 764 D24T/M46 155k |
#4
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So you guys set your breaking pressure at 2400 psi (~163 bar)? I've read - somewhere - that the greater you set this value the longer it takes the injectors to inject, thus retarding the injection timing. Is the idea here that if you advance the pump timing you retard the injectors to "even out" the fuel delivery timing?
Or is setting a higher breaking done to achieve a better fuel atomization?
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Jim 1985 Volvo 740 GLE turbo diesel |
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Right, that is certainly true, and I suspect that in addition to retarding effective in-cylinder timing the higher breaking pressure also causes less total volume of fuel to be injected for a given setting of pump piston travel (aka the "smoke screw"). Both of these can be compensated, by altering pump timing and increasing injected quantity by turning in the screw.
Better fuel atomization is the intended result, and there is a reason that in the case of our modified engines the normal TD setting value of 155 bar might not be high enough. Part of my rationale for running the higher injection pressure is that ultimately this engine will be ending up with higher in-cylinder pressure right before the moment of injection, due to increased airflow and manifold pressure. The combination of the upcoming changes -- D24 cam with earlier lift and longer duration, D24 intake that flows more air, larger turbo/increased boost, intercooler -- will all ultimately have the effect of cramming more air into the cylinder, and when it is compressed it will mean that there is considerably higher pressure in the combustion chamber for the injector to overcome as it begins to spray the fuel in. You want the pressure differential to be a given ratio for optimum atomization. Making the fuel/air pressure ratio greater (as in higher injection pressure at a given in-cylinder pressure) is fine for atomization, but increasing combustion chamber pressure without also increasing injection pressure is a recipe for compromised atomization, which leads to more smoke, less power, worse efficiency etc when running under boost. This is the same reason there are different specs for setting breaking pressure on D24T vs NA D24 engines. Higher compression pressure and more air volume requires higher injection pressure or else complete atomization will not occur. That is why you can run turbo injectors in a NA engine, but it is not a good idea to run NA injectors in a turbo car. So, short story is that when I was building the injectors I anticipated the fact that in the future I intend to increase the amount of air and compression pressure in my cylinders, and figured I should therefore slightly increase the injectors' breaking pressure as well to keep their pressure differential closer to what was intended.
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86 745 D24T/ZF 345k lifted 2.5" 83 764 D24T/M46 155k |
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What he said^^^
Mine really picked up some low end torque with the addition of the NA manifold, but with the way the torque converter slips, I really cant tell how much of a difference there is below 2k rpms. The engine revs to 2k as soon as you step on the gas if you are taking off. The top end power difference with the larger turbo is very obvious. Even before the intercooler, the NA manifold, or even the 2" charge pipe I had going into the front of the original manifold the top end power was much better. Mine was the same as yours, it fell off above 4k rpms. Now it pulls strong all the way to 5k untill it starts to defuel. I really think it has most to do with the tiny stock exhaust housing. Hell when I was pushing over 20lbs with the stock turbo it actually slowed down above 4k rpms... You could feel it plain as day! With the way the torque converter slips, my best power band is from 3500 to 5000, though I can build full boost by about 2800 or so once the converter is locked. I just adjusted the pump up a little more and burried the boost controller. I cant make more than 20 to 21lbs of boost, the trans just slips more. It will build more once the converter locks on the highway, but that doesn't do me much good. My clutch should be here any day... Jason
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Back again with a '84 760 GLE D24T/ZF SOLD but not forgotten! 1984 760 Sedan, built D24Tic/ T-5 swapped My engine build: http://www.d24t.com/showthread.php?t...t=engine+build T-5 swap: http://d24t.com/showthread.php?399-W...to-quot-w-pics! |
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