From: Dave <david.staten@gmail.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Fri, March 4, 2011 11:03:17 PM
Subject: [FlyRotary] Re: Knock sensor and indicator
I will bet a coke or two that this is related to intake charge temp, which in his installation may be unmonitored. I cant remember if we (when I was actively working with him on his build) put a thermocouple on the intake or not - the Mistral Intake I bought had 3 ports on the throttle side for "stuff". I remember putting two of them to the intake manifold pressure sensors, and may have put the third one to a thermocouple, but unknown if Chris had wired up and calibrated that, or if it actually was just plugged with a threaded blank/cap.
Couple that
with a boosted engine, minimal airflow over the intercooler. Also... how many inches of MP is Chris actually getting? I remember he says he has 3lb springs in the wastegate, so that SHOULD be 6" of boost.. so a max MP of 36". If he's getting anything more than that, then something is out of calibration or its not a 3lb spring.
Using universal gas law, PV=nRT, and playing with a gas law calculator calculator, I dont know if I missed something.. but a 70F degree day (294 degrees Kelvin), standard pressure 29.92" (760 torr) boosted to 36" (914 torr) and keeping the volume constant, I got a charge temp of 175 F. If you boost to 45" (15" extra boost, 7-8 lbs) you get a charge temp of 336 degrees F. This does not account for waste heat from the turbo wheel heating up the compressor by direct conduction.
That means (if my numbers are right), the air leaving the turbo to the intercooler is 175 degrees F or more. With no airflow over the
intercooler, the only heat loss minimal radiation and conduction, so you still have VERY HOT AIR going into the combustion chamber, which predisposes you to detonation tremendously.
On 3/4/2011 10:39 PM, Kelly Troyer wrote:
John,
Chris is using Tracy's apex seals (2mm) which are fairly tough and is only using
about 3 psi boost so any ideas on what is causing detonation ?............Perhaps too
much ignition timing or mixture problems such as spending to much time at best
power mixture (1700+ f EGT) instead of richer than best power before leaning
quickly to lean of peak EGT..........What EGT temps do you routinely see during
takeoff, climb and cruise ?..........Do you aggressively lean at cruise ?............
Thanks,
Kelly Troyer
"DYKE DELTA JD2" (Eventually)
"13B ROTARY"_ Engine
"RWS"_RD1C/EC2/EM2
"MISTRAL"_Backplate/Oil Manifold
"TURBONETICS"_TO4E50 Turbo
From: John Slade <jslade@canardaviation.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Fri, March 4, 2011 4:30:29 PM
Subject: [FlyRotary] Re: Knock sensor and indicator
On 3/4/2011 4:43 PM, Kelly Troyer wrote:
> engine runs reported by Chris at high manifold pressure, high coolant temps and as you mentioned
> probably high intake temps with little or no airflow across the intercooler.............
I did many, many
engine runs and high speed taxi tests prior to flight, often with the temps at the limits. On occasion I was able to hear "pre-ignition" and back off the throttle. There was no sign of damage to my seals - but mine are 3mm 'indestructible' seals from Tracy.
John Slade
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