View Full Version : EJ-22 RPM question and poll.
01-02-2005, 11:57 AM
I have my EJ-22 turning 5250 on take off and I usually cruise at 4350 at 70 mph in the winter. Any thoughts on the best RPM setting to efficiently and safely get the most HP on climb out and what can I run the EJ-22 safely at when I cruise as a maximum setting.I pose this question as a Magni owner said he climbs at 5600 out of his rotax 4 stroke and cruises at 5200. Woud they be safe numbers for the Subie with similiar reliability?
01-02-2005, 01:00 PM
Larrye I run my ej-22's at about the same as yours. Most of the US Raf instructors have them running at 5500 according to the Raf manual.
There does not appear to me to me much, if any gain, by going from 5200 or 5300 to 5500. The hp curve is quite flat by then. Every rpm extra puts more stress. The rule of double the rpm and you quadrupple the forces on everything in the engine.. realy counts at high rpm.
By being able to cruise at 4350 instead of 4600 means that the reliability factor will be better.
I would like a comment from Don Parham re this.
Aussie Paul :)
01-02-2005, 06:15 PM
Larry: I get about 5150- 5200 on climb out.
After switching to my Sportcopter rotor...my engine rpm's are 200 less at my normal flying speeds.
I have 13 degrees pitch in my Warp drive prop...and I am seriously considering trying 14 degrees so as to lower my cruise rpm even further. I am guessing my cruise speed will go even higher with less rpm. I realize that I will have less climb performance....but my climb rate has increased a lot with the rotor change....so much so that I am willing to give back some of this climb performance for lower rpm's at cruise.
01-03-2005, 12:11 AM
I agree. Max H.P. (or torque) is at 5400, I believe, but I feel no difference at 51 or 5200. 5400 seems to be overkill with little benefit. I can really play with the numbers with my IVO cockpit adjustable prop. By cutting the engine rpm a little and going not quite to full cruise-pitch on the prop, I can cruise close to 90 m.p.h. Full cruise-pitch slows me down to in the lower 70s. The gas burn ain't worth a crap, but it sure is different plowing along at 500' AGL and 88 m.p.h. I should really place pitch-limiting washers at both ends, but just haven't had the time to play with it.
01-03-2005, 02:57 AM
Ken, do you run a fuel flow gauge?
Aussie Paul. :)
01-03-2005, 11:12 AM
Nope, Paul. I have one, but it won't fit the line that I'd have to place it in. There is a pressure take-off on my flow-block that sends the fuel to each cylinder and I have a graph that shows how much fuel flows at what pressure, but again, I don't have the time right now to get to it. I really do need to get it installed so I can check the fuel-flow at different settings.
01-03-2005, 12:30 PM
Thanks for the input. Sounds like we RAFers are pretty much on the same page. Ken, what is your cruise RPM?
01-03-2005, 01:51 PM
When I'm up there gittin' my fix, I've got a 15-20 mph wind on my nose and I look down at the 4 wheel traffic and they're passin' me at a pretty good clip...I'm happy cause I'm up here and they're down there.
And you know what...I'm only burnin' 5 gal/hr. for my fix. ;)
01-03-2005, 02:30 PM
That's what it is all about Harry. That "magic" 3 letter word, "FUN" !!!!!!!!!!! LOL
Like these pics below of my trip to the center of Oz where Birdy hangs out!!!
Aussie Paul. :)
01-03-2005, 05:48 PM
Larry, I can get down to around 3700 engine rpm in cruise with the IVO. But without a fuel-flow, I don't know yet where my best settings are for speed to economy.
01-06-2005, 05:29 PM
I would agree with a broken in engine with 10+ hours I would set my static warmed up engine to 5350 which should unload to 5400 neighborhood on climb out. The colder weather really has an impact (good) on engine rpm, hp, cruise and lift. I have had my engine down to 3900 holding 60 mph ias at 500' steady. 1person 2 place machine.
and I do not have an adjustable prop. with 180 lbs ballast it will cruise at 46-4700. same figures. 5500 seems a bit high but the raf has a pod and may need that upper rpm.
TORQUE moves your ship, not horsepower.
2 place air command type tandem ej 22.
I agree with you on the fact that running the engine at 5500 is a waste of fuel. The engines will run full bore without excessive stress, but there is no use to turn more than 5400 unless you have the Stratus cam grind. If so, then you can turn 56-5700 for maximum hp.
BTW--the SOHC EJ25 makes its max power at 5600 instead of 5400 like the EJ22 and DOHC EJ25. The new turbocharged EJ25 for the Legacy, Outback and WRX make their maximum power at 6,000 rpm. The new H6-3.0 engine in the L.L. Bean edition of the Outback makes 250 hp @ 6600 rpm.
Also, the new Rotax 200 and 300 hp, four-stroke V-6 aircraft engines are rated at 6,000 rpm. Engine technology (metalergy) is getting much better and stock auto engines are running much higher rpm than older technology stuff. One of the new Honda engines makes its rated hp @ 8500 rpm!
An endurance run made in 1992 with three Legacy autos using turbocharged EJ20 engines in the Arizona summer heat went 100,000 km (62,000 miles) at full bore (average engine rpm of 5600 rpm) over an 18 day period. The cars only stopped to refuel and/or change drivers. That equates to 432 hours of running at pretty high rpm and high manifold pressures without a single problem.
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