argon39 wrote:
: In fact, the presenting problem is that I have not been solidly below
: 400?F. The hottest peak CHT just after takeoff on a standard day would
: be more like 430?F, and the coolest about 40?F. On really hot days I
: have seen even higher values, albeit for only a short time. I think I
: have solved this problem at this years's annual by installing a fairing
: around the big gap between the PowerFlow exhaust pipe (much smaller
: than the standard Cessna exhaust). With the fairing installed, peak
: CHTs just after takeoff are now between 400?F and 37?F as a result
: of better airflow inside the cowling.

What type of CHT probes? If they're the spark-plug type, then you're still
pretty much fine. They tend to read 50-75 degrees hotter than the "official" locating
of the cylinder well lug type.

The other indirect reading of fuel flow will be the EGT. How much lower than
high-power cruise peak is it on full-rich takeoff? In my O-360-A3A Cherokee, I read
1600-1650 peak EGT in cruise, but 1400 on full-rich takeoff. In fact, during a long
climb I'll lean to that 1400 as I gain altitude. From what I've read, with 200-250
degrees between the two, I should be more than fine... might want to check yours

: Regarding design limits, I do appreciate that Deakin was referring to
: bigger engines. But I still wonder what a limit for the O-360 might be
: as a result of adding the tuned exhaust.

Probably not getting more than 5-10hp out of it. Although, with the
scavanging effect of a tuned exhaust, the max fuel flow could certainly require that
additional 5-10hp's worth. Making more power takes more fuel.

Of course, all that assumes the tuned exhaust actually works... ;-)

: One step at a time, let's check the prop governor and maybe the
: wide-open mixture.

... and EGT. It's the best way (short of a wideband O2 sensor, etc) to
determine the *actual* mixture of the engine on takeoff.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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