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NoDOHC · 07-09-2010, 06:11 PM

I agree that your low pressure pulses are due to improper fuel mix at your single point of ignition (since you are using the one spark plug hole for a pressure transducer). The flame front velocity is greatly reduced in improper mix, so the flame front propogation is too slow from a weak initation event.

What are you using for ignition? The spark energy appears to be too low.

What is your ignition timing? Peak cycle efficiency for a piston engine is typically with peak combustion pressure occuring at 12 degrees ATDC, so I would look for 18 degrees on a rotary. It seems that your 45 degree peak pressure is running a terribly retarded ignition.
Have you tried adjusting your fuel mix to improve your combustion?

That is cool that you found some high speed trasducers.I have been wanting to get some for a while now, we use cylinder pressure transducers at work to maximize horsepower and efficiency, as well as emission predictions.

Area under the pressure curve is your friend (indicated torque).

Speaking of that, it is very low. I see where you mention that it is wrong. You should be seeing somewhere around 210 Lb-ft for two rotors, 105 lb-ft for a single rotor based on my output dyno findings.

Your blowdown (pressure at exhaust open) will decrease if you get your ignition timing corrected. Still this blowdown number argues for a later exhaust port opening...

You should see combustion initiation (blue and red diverge) slightly before TDC. (Not too much obviously).

Thank you so much for posting this awesome information! I really like seeing data like this.

Your peak cylinder pressure is low, but very good for 45 degrees (although that is only 30 on a piston engine). I am guessing that this is a 9.0:1 Compressiion ratio engine...

I am guessing that the sensor is in the leading plug hole, as you couldn't read pressure to the end of the power stoke in the trailing plug hole.

I would love to drill an additional hole at the bottom of the housing to monitor so that I could observe effects of leading/trailing split.

07-09-2010, 06:11 PM	#16
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 17	I agree that your low pressure pulses are due to improper fuel mix at your single point of ignition (since you are using the one spark plug hole for a pressure transducer). The flame front velocity is greatly reduced in improper mix, so the flame front propogation is too slow from a weak initation event. What are you using for ignition? The spark energy appears to be too low. What is your ignition timing? Peak cycle efficiency for a piston engine is typically with peak combustion pressure occuring at 12 degrees ATDC, so I would look for 18 degrees on a rotary. It seems that your 45 degree peak pressure is running a terribly retarded ignition. Have you tried adjusting your fuel mix to improve your combustion? That is cool that you found some high speed trasducers.I have been wanting to get some for a while now, we use cylinder pressure transducers at work to maximize horsepower and efficiency, as well as emission predictions. Area under the pressure curve is your friend (indicated torque). Speaking of that, it is very low. I see where you mention that it is wrong. You should be seeing somewhere around 210 Lb-ft for two rotors, 105 lb-ft for a single rotor based on my output dyno findings. Your blowdown (pressure at exhaust open) will decrease if you get your ignition timing corrected. Still this blowdown number argues for a later exhaust port opening... You should see combustion initiation (blue and red diverge) slightly before TDC. (Not too much obviously). Thank you so much for posting this awesome information! I really like seeing data like this. Your peak cylinder pressure is low, but very good for 45 degrees (although that is only 30 on a piston engine). I am guessing that this is a 9.0:1 Compressiion ratio engine... I am guessing that the sensor is in the leading plug hole, as you couldn't read pressure to the end of the power stoke in the trailing plug hole. I would love to drill an additional hole at the bottom of the housing to monitor so that I could observe effects of leading/trailing split. __________________ 1986 GXL ('87 4-port NA - Haltech E8, LS2 Coils. Defined Autoworks Headers, Dual 2.5" Exhaust (Dual Superflow, dBX mufflers) 1991 Coupe (KYB AGX Shocks, Eibach lowering springs, RB exhaust, Stock and Automatic) Last edited by NoDOHC; 07-09-2010 at 06:28 PM.