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Engine basics => Engine set up tips => Topic started by: Randy Powell on September 09, 2007, 09:17:19 PM
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Well, that's pretty much the question. I haven't run this engine in quite awhile and can't remember what pipe length I was using. Any suggestions?
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Randy, right now my Ro-Jett 65 is happy at 18 inches. I use a Gator 13x4 and new Powermaster blend recomended by RO. Its in a UHP Impact.
Wayne
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Thanks, Wayne.
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Thanks, Wayne.
Use 145 degrees on Randy's chart.
To be safe, time the engine and set the pipe to the exhaust duration of your engine using Randy's chart.
When in doubt, go a little long!!! Long pipes are much better than short pipes!!! Short pipes suck!!!
No pipes are even better...
...oops...
...did I say that out loud? ;D
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Brad,
I finally found my notes on the plane I ran this engine on with a pipe. Seems I started out with a 17.5" pipe length and ended up with 18.25". I'll probably start there.
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EX-TIMING AERO 40\51\61\65 AERO 75 & 85 OPS/OS/ST OPS/OS/YS OS/YS
RPM 130degree 135degree 133 degrees 140degree 145degree 150degree 155degree
9000 18 1/2 18.5-18.75 18.3-18.7 19 5/8 20.25 + 20 7/8 21 1/2
9500 17 3/4 17 3/4 -18 17.4-17.9 19 19.625 + 20 3/8 21
10000 17 5/16 17.5-17.75 17.25-17.5 18 3/8 19-+ 19 3/4 20 1/2
10500 16 3/4 17-17.25 16.9- 17.2 17 7/8 18.3125-+ 19 19 7/8
11000 16 5/16 17-16.75 16.7 17 17 5/16 17.875-+ 18 5/8 19 1/4
11500 16 16 5/16 16 3/4 17.375-+ 17 3/4 18 3/4
12000 15 3/4 16 1/8 16 3/8 16.75-+ 17 1/2 18 1/8
12500 15 3/8 15 3/4 16 1/16 16.375-+ 17 17 5/8
13000 14 7/8 15 3/8 15 9/16 16-+ 16 1/2 17 1/8
13500
PIPE TUNING CHART by Randy Smith
I hope this will stay in the correct rows
I would use the higher timed ex numbers for that engine
Randy
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Thanks, Randy
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Well, that's pretty much the question. I haven't run this engine in quite awhile and can't remember what pipe length I was using. Any suggestions?
17.5 is what Richard suggested I start with on my 51. Since majority of RoJetts(40-65) have same timing, I'd start there with the 65 as well. It runs in very comfortable constant 4.
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17.5 is what Richard suggested I start with on my 51. Since majority of RoJetts(40-65) have same timing, I'd start there with the 65 as well. It runs in very comfortable constant 4.
Hi Steven
I am curious ,What makes you think that the Jetts all have the same timing?
Regards
Randy
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I am curious ,What makes you think that the Jetts all have the same timing?
I didn't say all Jetts, just sub 65 ones. Not sure how I know that. I'll check archived email exchanges with Richard Oliver tomorrow at the office and report back.
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and report back.
Quick search on SSWF brought this:
http://www.clstunt.com/htdocs/dc/dcboard.php?az=show_topic&forum=103&topic_id=232053&mesg_id=232053&listing_type=search#232061
It looks like at least 61 and 65s are timed the same.
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Quick search on SSWF brought this:
http://www.clstunt.com/htdocs/dc/dcboard.php?az=show_topic&forum=103&topic_id=232053&mesg_id=232053&listing_type=search#232061
from Ricahrd
Lets put this to bed. Timming is 144/128. It was intended to be 136/126. When we made the first engine it turned out to be 140/130.
After flying this for a while I asked Dub to make one that was 4° lower to 136/126. When he programed the new liner he went the wrong way (remember we are making one at a time at this point) and made it 144. Not sure how he got the 130 down to 128 but there it was. Out to the flying field I went and it ran so well I never looked back or even checked it. Jett was told to run with the program in the production run and off I went to my first Nats. When some, certainly not all, can not make a motor run the first call I get is that the motor is bad or defective or in some cases we have been told we do not know what we are doing.
RO
Hi Steven
From your quoted thread. So there maybe could be multiple timings on the RO Jett 65 that Randy asked about.
Randy no matter what the timing. I would suggest just getting a 360 degree plastic protractor and see what the timimg on your engine is
Simple easy and that way you wll be sure.
Regards
Randy
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From your quoted thread. So there maybe could be multiple timings on the RO Jett 65 that Randy asked about.
I believe in the quote you to refer to, Rich was talking about the first 61 engine. 65 came later and used CNC program already setup for the 61 sleeves. He also wrote about having just the first 61 motor with odd timing.
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I believe in the quote you to refer to, Rich was talking about the first 61 engine. 65 came later and used CNC program already setup for the 61 sleeves. He also wrote about having just the first 61 motor with odd timing.
Hi Steven
No ,Richard was talking about the 65 not the 61, Randy asked for lenght on the pipe for the 65, from all I have read and heard from people who actually checked the timing on the engines,
I would stick with what I suggested for Randy to do.
Also Richard stated that they started to use the higher timing in the new engines about 2 or 3 years ago
Check the timing on the engine he has,
You stated that he should use the same timing as your Jett 51, on his 65, because most of the Jetts are timed the same.
Looks like their is a good possiblity that there maybe a big differance in timing between your 51 and his 65.
That was my only point, check it then you will know. Other people have and were surprised.
Richard and other are running longer pipes, (some out to 19 or 20 inches) and this makes perfect sense if the timing is higher than 135 degrees. It's just a matter of doing the math, higher timed run longer pipes, lower timed runs shorter pipes.
Randy
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That was my only point, check it then you will know. Other people have and were surprised.
Is there a HOWTO on how to get engine timing measured? You peaked my interest and I'd like to try checking timing on my motors.
I understand that there are also different PA75's configurations out there. I own two and am very curious as to which setup they are.
Steve
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There are no PA 75s out there with differant timing.
Randy
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There are no PA 75s out there with differant timing.
I just wrote that there are two different configurations, not necessarily timing configurations. Something to do with booster ports...
P.S. Randy, I hope you don't think I am trying to boo your products. I'm a happy owner of several PA's. As a matter of fact, next year I will have three new ships; all powered by your stuff(PA75, PA40Lite and AT36).
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I got curious about the timing differences between a 51 and a 65 RoJetts. Since I don't know how to check the timing with a wheel, I just unbolted the header from the 51, bolted it onto 65 and stuck it back in my current ship. At 17.5", it 4-cycled very nicely at 9800 with only a hint of 2-cycle. Same type of run as with the 51! I know is NOT scientific but it does indicate that 65 and 51 have similar type of timing and run characteristics! Cool.
Steve
P.S. I used to run 5.2 laps with 51 and was getting plenty of tension in all but extremely windy conditions(20+ mph). My hand never got tired tired from the pull. After dropping 65 in(still 5.2 laps), the tension increased SIGNIFICANTLY to the point where my hand gets very tired right around vertical 8's! I can't wait to finish my PA75 powered Eurostyle! I may be able to fly 5.5 laps in the wind yet!
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""I got curious about the timing differences between a 51 and a 65 RoJetts. Since I don't know how to check the timing with a wheel, I just unbolted the header from the 51, bolted it onto 65 and stuck it back in my current ship. At 17.5", it 4-cycled very nicely at 9800 with only a hint of 2-cycle. Same type of run as with the 51! I know is NOT scientific but it does indicate that 65 and 51 have similar type of timing and run characteristics! Cool.""
HI Steven
That doesn't really indicate anything about the timing. I can make most any stunt engine run in a 4 cycle 2 cycle at most any pipe lenght. And I have ran several engines from 14 inches to 21 inches all in a nice 4 cycle. What is missing was the governing-holdback in the wind, also some would hit harder or softer at differant lenght.
You really have to time the motors to find out the info you want.
Timing engines is not difficult, You can buy a Inexpensive round plastic 360 degree compass many places, Just drill a hole in the middle of it, Install it on your motor like you would a prop, and you are set to check the timing. It is easiest most times if you remove the head. A good technique to use is to make a pointer from a small piece of piano wire with a loop in it. use a head bolt to hold it in place to the top of the case and use another head bolt in front of it to make sure it doesn't move. You can then read where the pointer is in relationship to the compass, and for exhaust turn the motor over the entire range that the ex. ports are open for. read the compass and do the math for how many degrees it stays open.
The intakes are done the same way, just turn the engine over and read where you start and where you stop on the compass.
Many people will try to set the compass a zero degrees to make it easy to read, this is fine but not necessary, you can read where the ports open and then read where they close and figure from there.
Regards
Randy
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You really have to time the motors to find out the info you want.
Timing engines is not difficult, You can buy a Inexpensive round plastic 360 degree compass many places, Just drill a hole in the middle of it, Install it on your motor like you would a prop, and you are set to check the timing. It is easiest most times if you remove the head. A good technique to use is to make a pointer from a small piece of piano wire with a loop in it. use a head bolt to hold it in place to the top of the case and use another head bolt in front of it to make sure it doesn't move. You can then read where the pointer is in relationship to the compass, and for exhaust turn the motor over the entire range that the ex. ports are open for. read the compass and do the math for how many degrees it stays open.
The intakes are done the same way, just turn the engine over and read where you start and where you stop on the compass.
Many people will try to set the compass a zero degrees to make it easy to read, this is fine but not necessary, you can read where the ports open and then read where they close and figure from there.
This doesn't sound difficult at all! Thanks Randy!