Turbo Jett on OS 1.08 BX1
02-09-2005, 05:59 PM
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Turbo Jett on OS 1.08 BX1
I am currently putting a new plane (Funtana 90 I think about 10pounds all up) together and am using a O.S 1.08 BX1 motor I already have. I was about to order a slimline pitts but then got to thinking about your turbo jet in cowl muffler. The motor turns a 16 x 6apc 9300 with a stock muffler and 9600 with Jtec pitts.
1)What kind of performance gains would I expect with the turbo jett?
2)Will I experience a more non-linier throttle curve (a peaky tuned effect from muffler) That would be detrimental to 3D flying?
3) I was planning on running a VP30 perry pump and moving my gas tank back about 6" from the motor. Reading some posts on this forum I see the turbo jett puts out more tank pressure I may not have to use the pump. Am I correct? How far back do you think I could move it if I do that? Do you use a 1 way check valve to keep pressure up when motor rpms are down?
Thanks,
Steve GPS
1)What kind of performance gains would I expect with the turbo jett?
2)Will I experience a more non-linier throttle curve (a peaky tuned effect from muffler) That would be detrimental to 3D flying?
3) I was planning on running a VP30 perry pump and moving my gas tank back about 6" from the motor. Reading some posts on this forum I see the turbo jett puts out more tank pressure I may not have to use the pump. Am I correct? How far back do you think I could move it if I do that? Do you use a 1 way check valve to keep pressure up when motor rpms are down?
Thanks,
Steve GPS
02-10-2005, 11:23 AM
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RE: Turbo Jett on OS 1.08 BX1
Hi Steve,
Thanks for writing....
The 108 BX1 resonds quite nicely to the turbo-jett. With this size engine and props, you will not see a huge rpm gain (takes a lot of HP increase to move bigger blades), but on average you can expect 400-600 rpm gain from your stock set up, with the same prop.
The big advantage is a torque increase. We have found it is sometimes better to increase te prop rather than to push for more RPM. Typically, you can increase the prop size a bit (ex 16x8) and keep the rpm you currently have. We found this to be very much the case with our BSE-120 and also with the ST2300. The OS160 provided similar results.
On the Funtana, I would probably stick with the 16x6 at first.
As far as pipe step, that does not tend to be an issue with the turbo-jett. With a regular pipe, and to decent extent with the Jett-stream muffler, yes, there is a notible pipe step that occurs as the engine stages into the tuned range.
The turbo-jett is tuned, but is is very broad band. And due to the unique design, there is no real decernable pipe step. This results in a much smoother, more linear throttle response.
Tank pressure......
Yes, the turbo-jett does put out some substantial tank pressure. And on my aircraft, I have managed to slide the tank back a bit from the engine, closer to the CG. But not all the way to the CG. You can get away with an extra 3-4" or so. Maybe a bit more if you maintain a higher power setting in vertical manuvers (higher power = more tank pressure). A few of us have found that adding a 2oz hopper tank up right at the firewall, and using the check valve, permits fuel draw from somewhat greater distances (for momentary operation - not for hovering nose up 3 minutes at a time).
If you are going for a CG mounted tank, you may want to consider the pump.
I hope this is helpful
Bob Brassell
Thanks for writing....
The 108 BX1 resonds quite nicely to the turbo-jett. With this size engine and props, you will not see a huge rpm gain (takes a lot of HP increase to move bigger blades), but on average you can expect 400-600 rpm gain from your stock set up, with the same prop.
The big advantage is a torque increase. We have found it is sometimes better to increase te prop rather than to push for more RPM. Typically, you can increase the prop size a bit (ex 16x8) and keep the rpm you currently have. We found this to be very much the case with our BSE-120 and also with the ST2300. The OS160 provided similar results.
On the Funtana, I would probably stick with the 16x6 at first.
As far as pipe step, that does not tend to be an issue with the turbo-jett. With a regular pipe, and to decent extent with the Jett-stream muffler, yes, there is a notible pipe step that occurs as the engine stages into the tuned range.
The turbo-jett is tuned, but is is very broad band. And due to the unique design, there is no real decernable pipe step. This results in a much smoother, more linear throttle response.
Tank pressure......
Yes, the turbo-jett does put out some substantial tank pressure. And on my aircraft, I have managed to slide the tank back a bit from the engine, closer to the CG. But not all the way to the CG. You can get away with an extra 3-4" or so. Maybe a bit more if you maintain a higher power setting in vertical manuvers (higher power = more tank pressure). A few of us have found that adding a 2oz hopper tank up right at the firewall, and using the check valve, permits fuel draw from somewhat greater distances (for momentary operation - not for hovering nose up 3 minutes at a time).
If you are going for a CG mounted tank, you may want to consider the pump.
I hope this is helpful
Bob Brassell
11-30-2005, 12:25 PM
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RE: Turbo Jett on OS 1.08 BX1
Here I am thinking about moving the OS108 from the 10 pound Funtana to my 9 pound Yak now and am reconsidering the Turbo jet muffler. The inverted jtec pitts I have now is giving me good #'s, but I am sure the Jett would be quieter (at least at lower throttle settings) and would be worth it if I could step to a larger prop or get more RPM's (more power).
Has the turbo-jett been tested against open face readings? Does it deliver results that are better than open face? My guess is with the noise level of the J-tec that it is free flowing & delivering close to open face #'s(also I am getting significantly better #'s than stock muffler about + 300) and just want to make sure that I will see a power boost if I go with the Turbo-Jett.
BTW I am running a VP30 perry pump with a bypass back to the tank just before the needle valve.
Thanks for your help.
Has the turbo-jett been tested against open face readings? Does it deliver results that are better than open face? My guess is with the noise level of the J-tec that it is free flowing & delivering close to open face #'s(also I am getting significantly better #'s than stock muffler about + 300) and just want to make sure that I will see a power boost if I go with the Turbo-Jett.
BTW I am running a VP30 perry pump with a bypass back to the tank just before the needle valve.
Thanks for your help.
11-30-2005, 05:03 PM
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RE: Turbo Jett on OS 1.08 BX1
Hi Steve.....
I have not run a 1.08 open exhaust. Most modern engines do not perform well with an open exhaust - they require some backpressure regardless if you are using a pump or not - so it is not much of a useful measurement. Plus its LOUD !!
So I can not really address your question. Compared to the engine on a stock OS exhaust, or a Bisson muffler, you will see a notible gain in both rpm and torque.
I will see if Dub has any specific notes on the 1.08 tests he did.
My experience with the OS 1.08 with the turbojett is it ran nearly the same as the Jett 1.20 with the turbojett. Its just a physically larger engine.
Some of the pitts mufflers are little more than directional manifolds. They provide limited backpressure, and not much volume or directional porting to get things quiet.
Bob
I have not run a 1.08 open exhaust. Most modern engines do not perform well with an open exhaust - they require some backpressure regardless if you are using a pump or not - so it is not much of a useful measurement. Plus its LOUD !!
So I can not really address your question. Compared to the engine on a stock OS exhaust, or a Bisson muffler, you will see a notible gain in both rpm and torque.I will see if Dub has any specific notes on the 1.08 tests he did.
My experience with the OS 1.08 with the turbojett is it ran nearly the same as the Jett 1.20 with the turbojett. Its just a physically larger engine.
Some of the pitts mufflers are little more than directional manifolds. They provide limited backpressure, and not much volume or directional porting to get things quiet.
Bob
