LS into a CESSNA airplane
07-24-2021, 12:17 AM
#22
The prop design is custom for the application, and matched to gear box specs. Gear boxes present a lot of issues with props, especially pulse stress and symmetric prop blade loading and vibration. We plan on installing another V8 flat rated to about 300HP on a larger plane with a variable pitch prop which further complicates things, but a larger/heavier prop helps with pulse fatigue.
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G Atsma (07-24-2021)
10-23-2021, 11:16 PM
#23
try to answer some of the above questions….. the cooling was a challenge due to cooling drag coefficients at the 100-130 MPH speeds….we had enough flow there, but taxi speeds were not enough and tried to redesign air intake better to increase flow but added too muck drag at cruise. This is a common challenge for aircraft and most use cowl flaps on ground to help. We didn’t want to redesign the cowl for a number of reasons and used elec fans controlled by ECM that normally shut off shortly after takeoff. We also played around with intake flow shapes that increased pressure differentials each side of radiators, as well as experimented with waterless coolant.
as far as P factor (which is yaw and banking cased by prop, mostly at high power settings and low airspeed and higher angles of attack)…. The C172 has a big rudder so it wasn’t too difficult, just took time. The problem we did foresee was what if pilot got slow on a go-around (a maneuver where pilots aborts landing at last moment and applies full power to climb). Although the engine is flat rated to less than 220HP, the engine gets there very quick and can become a hand full if the pilots applies full power rapidly and is a bit slow in airspeed (below approach speed, which decreases airflow around the planes controls surfaces and makes them less responsive). So we made some changes in the tune that reduced just how fast the power can increase from normal approach throttle settings……so even if throttle was shoved to full quickly, the engine would increase power a bit slower to allow additional time for pilot to maintain control with inputs. This was a challenges as it’s a mechanical throttle controlling the EFI (needed to eliminate potential failure of a throttle by wire setup). We spent a lot of time trimming rudder and although yaw is opposite of original engine, it’s now intuitive.
About DA question…..stock Cessna engines are norm aspirated and lose rated power as soon as leaving sea level conditions. Figure about 3% per 1000 ft DA. By flat rating the V8, there is so much more airflow capacity for combustion, what is lost in decreased air pressure, is made up for in volume, allowing it to maintain the rated thrust to higher altitudes without turbos. As far as any issues with flat rating, nothing too challenging other than break in procedures as we are using new blocks. BTW, the prop pitch and design also limits max HP just above ECM soft and hard limits.
as far as P factor (which is yaw and banking cased by prop, mostly at high power settings and low airspeed and higher angles of attack)…. The C172 has a big rudder so it wasn’t too difficult, just took time. The problem we did foresee was what if pilot got slow on a go-around (a maneuver where pilots aborts landing at last moment and applies full power to climb). Although the engine is flat rated to less than 220HP, the engine gets there very quick and can become a hand full if the pilots applies full power rapidly and is a bit slow in airspeed (below approach speed, which decreases airflow around the planes controls surfaces and makes them less responsive). So we made some changes in the tune that reduced just how fast the power can increase from normal approach throttle settings……so even if throttle was shoved to full quickly, the engine would increase power a bit slower to allow additional time for pilot to maintain control with inputs. This was a challenges as it’s a mechanical throttle controlling the EFI (needed to eliminate potential failure of a throttle by wire setup). We spent a lot of time trimming rudder and although yaw is opposite of original engine, it’s now intuitive.
About DA question…..stock Cessna engines are norm aspirated and lose rated power as soon as leaving sea level conditions. Figure about 3% per 1000 ft DA. By flat rating the V8, there is so much more airflow capacity for combustion, what is lost in decreased air pressure, is made up for in volume, allowing it to maintain the rated thrust to higher altitudes without turbos. As far as any issues with flat rating, nothing too challenging other than break in procedures as we are using new blocks. BTW, the prop pitch and design also limits max HP just above ECM soft and hard limits.
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G Atsma (10-24-2021)
10-24-2021, 06:20 AM
#24
Great info and undertaking! Can you comment on run hours before tear down and refresh?
and what sort of Ls specific preflight checks? If any?
rocker arms can be problematic if after market
sourcing quality lifters etc
do you pre qualify vendors to avoid knock off ls parts? Ie Amazon fakes.
and what sort of Ls specific preflight checks? If any?
rocker arms can be problematic if after market
sourcing quality lifters etc
do you pre qualify vendors to avoid knock off ls parts? Ie Amazon fakes.
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G Atsma (10-24-2021)
10-27-2021, 12:14 AM
#25
With the engine flat rated to less than 220HP, expect at least 3000 hours before block replacement. Only time, and oil analysis and inspections will tell. We programmed the display and ECM you see in videos to monitor dozens of engine parameters, and set dozens of alert triggers, so there is little preflight needed, other than selecting the backup EFI system to make sure it works if needed, and have a test switch which shuts down the main fuel pump to see if the backup pump automatically turns on…. Or pump must be turned on manually for critical phases.
using only OEM parts to avoid the unknown.
using only OEM parts to avoid the unknown.
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G Atsma (10-27-2021)
11-14-2022, 12:46 AM
#26
400+ hours so far and oil analysis results normal. Trying for 200 hr oil change intervals with Mobil 1 oil, lab results will tell. Plane still flys better than original and even had a couple of pilots get there private and commercial pilot training and check rides in it at a cost less than 50% than with original Cessna engine.
wanted to ask for feedback on LS3 max coolant temperatures….. on hotter summer days at high altitude airports with thin air about 9-10K ft DA, reached temps up to 230F on climb out. Using 50/50 antifreeze with 22 psi cap (actual cap release pressure is effected by lower ambient air pres so it’s about absolute pres equivalent 16 psi cap at about 10k ft) so boil over point about 265 ish. Running 160F t-stat and stock pump. Norm op temps 180-220F depending on OAT and prop load, but 220-230F rears it’s head on hot days…… what is really considered upper sustainable limit for LS3 temps??
wanted to ask for feedback on LS3 max coolant temperatures….. on hotter summer days at high altitude airports with thin air about 9-10K ft DA, reached temps up to 230F on climb out. Using 50/50 antifreeze with 22 psi cap (actual cap release pressure is effected by lower ambient air pres so it’s about absolute pres equivalent 16 psi cap at about 10k ft) so boil over point about 265 ish. Running 160F t-stat and stock pump. Norm op temps 180-220F depending on OAT and prop load, but 220-230F rears it’s head on hot days…… what is really considered upper sustainable limit for LS3 temps??
11-14-2022, 10:07 PM
#28
ModSquad
iTrader: (6)
I agree with this. 230 for short intervals isn’t a concern from a longevity perspective. I’ve sat in stop and go traffic for very long periods in a C5Z and watched the fans turn on at over 235. It would in turn, bring the oil temp up with it some, but it wasn’t alarming. Coolant temps drop very fast in these aluminum LS engines, when fans fire up.