which engine do I use???
09-29-2005, 12:06 PM
#1
Junior Member
Thread Starter
Join Date: Sep 2005
Location: Baton Rouge, LA
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
which engine do I use???
I have a plane that requires 16-17 lbs thrust sung a 13:4 prop. I need the lightest weight glow engine possible, and I think Jett looks like it has the best power to weight ratios. Can someone suggest a motor?
Joe
Joe
09-30-2005, 10:32 AM
#2
My Feedback: (19)
Join Date: Apr 2002
Location: Cleveland,
OH
Posts: 5,576
Likes: 0
Received 0 Likes
on
0 Posts
RE: which engine do I use???
Joe,
Thanks for writing.....
Jett does provide some of the best power-to-weight engines you will find anywhere.
I cant specifically help on the thrust numbers. Static thrust means very little in the engine business. About the same can be said for HP numbers - they are usually meaningless since they are rarely measured the same way.
Can you tell me more about the aircraft it will be installed on and what you are looking for for performance (speed, heavy lift, hover/3D stuff/scale ??) That will be very helpful
Some basic information, since you noted the 13x4 prop. Perhaps this will be useful for comparisons.
The Jett SJ-60L is a ".40" size engine - same size and appx weight of an OS .46. This turns an 11x6, 12.25x3.75 or 12x4 APC around 14,700 - 15,000 with the stock jett-stream muffler. Turns a 12x5 or 13x4 prop just short of 14,000 (those are big blades). Configured as a FIRE (rear exhaust) the engine can create some major torque, and will turn up to 13x6 props around 12,000.
The Jett BSE-76L is a ".40" size engine - same size and appx weight of an OS .46. This turns a 14x4W or 14x6 around 10,500 with the Lite-Jett untuned muffler. Due to the nature of the engine, we typically like to keep its max RPM below 13,000, and max static rpm below 12,500 rpm. Configured as a RE engine and a long pipe, this engine can turn more prop while maintaining 10,000 rpm at peak.
Moving up to the "60" size engines, the real moster powerhouse is the BSE-120L. Same size as our SJ-90L and the OS 61/91FX. This will turn a 16x8 up around 9500 rpm or a 15x8 around 11K rpm. Again, this engine should be set up to run between 9000 and 12,000 rpm for best performance, however pushing it to 13K is possible.
If you want killer rpm and power in a '60' size engine, the BSE-90L engine combined with the stock jett-stream tuned muffler will turn an APC 13x4 probably around 15,000 rpm - however I do not believe the APC props of that size are rated for that type of RPM. The 90L typically turns a 12x6 prop up to 14,500 rpm peak, and gets a 12x8 or 13x6 up over 13,000.
Again, let me know a bit more about your application and I can guide you a bit more clearly.
Bob
Thanks for writing.....
Jett does provide some of the best power-to-weight engines you will find anywhere.
I cant specifically help on the thrust numbers. Static thrust means very little in the engine business. About the same can be said for HP numbers - they are usually meaningless since they are rarely measured the same way.
Can you tell me more about the aircraft it will be installed on and what you are looking for for performance (speed, heavy lift, hover/3D stuff/scale ??) That will be very helpful
Some basic information, since you noted the 13x4 prop. Perhaps this will be useful for comparisons.
The Jett SJ-60L is a ".40" size engine - same size and appx weight of an OS .46. This turns an 11x6, 12.25x3.75 or 12x4 APC around 14,700 - 15,000 with the stock jett-stream muffler. Turns a 12x5 or 13x4 prop just short of 14,000 (those are big blades). Configured as a FIRE (rear exhaust) the engine can create some major torque, and will turn up to 13x6 props around 12,000.
The Jett BSE-76L is a ".40" size engine - same size and appx weight of an OS .46. This turns a 14x4W or 14x6 around 10,500 with the Lite-Jett untuned muffler. Due to the nature of the engine, we typically like to keep its max RPM below 13,000, and max static rpm below 12,500 rpm. Configured as a RE engine and a long pipe, this engine can turn more prop while maintaining 10,000 rpm at peak.
Moving up to the "60" size engines, the real moster powerhouse is the BSE-120L. Same size as our SJ-90L and the OS 61/91FX. This will turn a 16x8 up around 9500 rpm or a 15x8 around 11K rpm. Again, this engine should be set up to run between 9000 and 12,000 rpm for best performance, however pushing it to 13K is possible.
If you want killer rpm and power in a '60' size engine, the BSE-90L engine combined with the stock jett-stream tuned muffler will turn an APC 13x4 probably around 15,000 rpm - however I do not believe the APC props of that size are rated for that type of RPM. The 90L typically turns a 12x6 prop up to 14,500 rpm peak, and gets a 12x8 or 13x6 up over 13,000.
Again, let me know a bit more about your application and I can guide you a bit more clearly.
Bob
09-30-2005, 10:46 AM
#3
Junior Member
Thread Starter
Join Date: Sep 2005
Location: Baton Rouge, LA
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
RE: which engine do I use???
Without going into too much detail (the competition plane is still under design), it will be a heavy lift application and will most probably use a ducted prop for propulsion. We are looking for the smallest (lightest) engine possible to get the job done, because that's where all the points are to be made. Also, do you discourage using a Nitro engine supercharger (Such as one from RB Innovations) on your engines? Can they handle it? We will probably be porting the motor in-house, but only if we see any sloppy surfaces. Also, we plan on sending all engines to HPC for thermo and lube coatings. Like I said, we need the absolute lightest engine that can lift our plane.
Thank you so much for your time, and the info you sent already helped a bunch.
Sincerely,
Joseph
MSU Heavy Lift Propulsion
Thank you so much for your time, and the info you sent already helped a bunch.
Sincerely,
Joseph
MSU Heavy Lift Propulsion
09-30-2005, 01:01 PM
#4
My Feedback: (19)
Join Date: Apr 2002
Location: Cleveland,
OH
Posts: 5,576
Likes: 0
Received 0 Likes
on
0 Posts
RE: which engine do I use???
Hey there......
There are a number of HL teams that have used the Jett engines in the past. A few so far are using the engines this year too. They work well when installed and operated properly, and with a good fuel system.
Bear in mind, Sport-Jett engines are designed and built to the same standards used for the Q-500 and QM40 racing engines, and the World Championship engines Dub built and flew on the US team in the early 1990s. The bigger engines derive from the standards set by the Fan-Jett 95 and famous SJ-120 big block. All are very capable and very durable. You will not break one. The carb, throttle response and idle are second to none.
Which class are you flying in? Which engine size are you permitted? I understand the rules were changed a bit this year.
Consider carefully your ducted prop design. Sometimes the benifit of the duct/prop tip efficiency is more than offset by the weight penalty. Also keep in mind the airspeeds and prop-tip speeds you will be working with.
I would strongly discourage any re-work or coatings on any of the JETT engines. They simply do not require anything else. Dub has designed some of the finest engines in the world, precision machined, and incorporating some very fine metalergy refinements on the piston/sleeve fit. Use good quailty model fuel, 15% nitro, 18% total lubricant with at least 3% of that being castor oil... and you can not go wrong.
If you have a specific/estimated rpm target, the engine timing and exhaust system can be somewhat customized to your application.
Supercharging - not worth it on a 2-cycle engine of this size and type. The tuned exhaust is essentially a supercharger, and is the best way to extract the best power from a 2-cycle engine. Inlet side charging is more useful for high altitude work, where inlet air density is important.
A word of advise - and a common error made by many heavy lift teams in recent year. Keep it simple. Innovation is good, but its not worth re-inventing the wheel. You want reliablity first and formost- that means tried, trued components. All of the innovation is of little use if the engine does not run 100% or causes you to not get in the air. Consider integration and testing of the powerplant as significant part of the design effort. I also strongly recommend (Regardless of which engine you choose) the use of a bubble-free fuel tank such as the Bubble-Jett tanks. It eliminates 90% of many common fuel system issues.
I have attached a flyer for the recently released LX series Jett engines. These represent the two highest power output sport engines Jett offers in the ".40" size and ".60" size class. These are RPM engines. RPM is key to their performance, prop selection must be made accordingly. As previously noted, several other engines and variations of these engines are available that are best configured for larger prop/lower rpm setups, and other balanced applications. A photo of the BSE-76L with the lite-muffler is also provided.
Bob
There are a number of HL teams that have used the Jett engines in the past. A few so far are using the engines this year too. They work well when installed and operated properly, and with a good fuel system.
Bear in mind, Sport-Jett engines are designed and built to the same standards used for the Q-500 and QM40 racing engines, and the World Championship engines Dub built and flew on the US team in the early 1990s. The bigger engines derive from the standards set by the Fan-Jett 95 and famous SJ-120 big block. All are very capable and very durable. You will not break one. The carb, throttle response and idle are second to none.
Which class are you flying in? Which engine size are you permitted? I understand the rules were changed a bit this year.
Consider carefully your ducted prop design. Sometimes the benifit of the duct/prop tip efficiency is more than offset by the weight penalty. Also keep in mind the airspeeds and prop-tip speeds you will be working with.
I would strongly discourage any re-work or coatings on any of the JETT engines. They simply do not require anything else. Dub has designed some of the finest engines in the world, precision machined, and incorporating some very fine metalergy refinements on the piston/sleeve fit. Use good quailty model fuel, 15% nitro, 18% total lubricant with at least 3% of that being castor oil... and you can not go wrong.
If you have a specific/estimated rpm target, the engine timing and exhaust system can be somewhat customized to your application.
Supercharging - not worth it on a 2-cycle engine of this size and type. The tuned exhaust is essentially a supercharger, and is the best way to extract the best power from a 2-cycle engine. Inlet side charging is more useful for high altitude work, where inlet air density is important.
A word of advise - and a common error made by many heavy lift teams in recent year. Keep it simple. Innovation is good, but its not worth re-inventing the wheel. You want reliablity first and formost- that means tried, trued components. All of the innovation is of little use if the engine does not run 100% or causes you to not get in the air. Consider integration and testing of the powerplant as significant part of the design effort. I also strongly recommend (Regardless of which engine you choose) the use of a bubble-free fuel tank such as the Bubble-Jett tanks. It eliminates 90% of many common fuel system issues.
I have attached a flyer for the recently released LX series Jett engines. These represent the two highest power output sport engines Jett offers in the ".40" size and ".60" size class. These are RPM engines. RPM is key to their performance, prop selection must be made accordingly. As previously noted, several other engines and variations of these engines are available that are best configured for larger prop/lower rpm setups, and other balanced applications. A photo of the BSE-76L with the lite-muffler is also provided.
Bob
