Thread: Why does the M112 engine's torque fall off at 4,750 rpm?
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Old Aug 18, 2009 | 11:38 AM
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DeepSurge
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Default Re: Why does the M112 engine's torque fall off at 4750rpm?
Originally Posted by dyezak

Go to http://www.rceng.com/technical.aspx and you can put in 240hp (our guestimated crank HP), our BSFC (good guess of .45), 6 injectors, 56psi, and .80 max duty cycle and see it comes up with a 19.xxlbs injector. We really don't have the fuel available to go higher safer without larger injectors. If you increase the airflow to the engine and thereby the HP all we are doing is running our injector's past .80 duty cycle, and at that point most injectors spray pattern is getting wonky and the injector will wear out faster causing leaks and the possibility of one sticking open.
(...)
So as you can see all the factors hurting the HP and torque are because of engineering trade-offs to lower the emissions. There's a lot of things coming together to rob this engine of power... But the damn thing sure does burn clean!!!!


Thanks for the info dyezak. I did replace the tiny injector for new ones (19lb/hrs from TVT) added more air to engine bia bigger airbox (c-class) and retuned the ECU (LET Motorsports) to keep that AFR in check. I went to the dyno (speed industry, Troy, MI) to get results. The Stability control got on our way, so only AFR values were obtained up to 3500rpm. OEM claims 14.7 AFR and we were lingering around this value in our test. But it’s obviously partial.

Regardless of all of the factors here listed hurting HP it’s my personal experience that injectors, more air and ECU reflashed provided more HP. It’s over a month with the mod’s and a joyous car to drive.

“If you increase the airflow to the engine and thereby the HP all we are doing is running our injector's past .80 duty cycle,” I’m quite ignorant on mechanics, but isn’t the ECU supposed to prevent injectors to max-out past that 80% duty cycle hence the need, among other reasons, of a ECU retune when swapping injectors?


Respectfully.
 
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