Building second DD w/ FAI GRRT
10-08-2002, 03:18 PM
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Building second DD w/ FAI GRRT
i've only got a 1/2 tunned MVVS 40 on my dust and its just not happy on the smaller props, 9x7 is the best it runs on. quick enough tho.. for now.....
10-08-2002, 08:42 PM
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Building second DD w/ FAI GRRT
ermmmm i have no idea... i know its not quite a Q500, but its not standard, the box has one of the MVVS *GRRT* type numbers, PSQ maybe, but its dark outside in the shed and i cant see 
i've got a Just Engines purple baffled pipe on too.
its not slow, i can keep West 50 Magnums honest and match the WXL 46's. Any Rapier is game
cant be above 16k
i've got a Just Engines purple baffled pipe on too.
its not slow, i can keep West 50 Magnums honest and match the WXL 46's. Any Rapier is game
cant be above 16k
10-09-2002, 03:48 AM
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Building second DD w/ FAI GRRT
Well still working on my DD. Its driving me crazy not having much time to work on it as I would like. The urge to go flying is killing me. I still have a bit more to do but getting alot closer to completing my DD. Cant wait!
I attached an updated photo in my gallery since it was to large of a file to view on here.
I attached an updated photo in my gallery since it was to large of a file to view on here.
04-27-2003, 08:04 PM
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Building second DD w/ FAI GRRT
i've been making my pipe shorter using SSAN's susgestions and swapped from 8x8 to 8x7, i've gone from 14K when i had the 8x8 on a uncut pipe to 18 with 8x7 and cut as much as i dare pipe.
im using 5% Prosynth and a glowing plug, i'll get a cold one when i can. but 18k? i had 16.8 with the 8x8 so i've gained 1k and lost an inch in pitch... thats not really worth it is it.
i cut almost an inch off today and got about 1k from uncut on the 8x7, thing is, my pipe looks WAY shorter than any other propper GRRT pipe,m mines not a MVVS item, but is full wave. is this just too short now? much more and i'll just have a stinger
im using 5% Prosynth and a glowing plug, i'll get a cold one when i can. but 18k? i had 16.8 with the 8x8 so i've gained 1k and lost an inch in pitch... thats not really worth it is it.
i cut almost an inch off today and got about 1k from uncut on the 8x7, thing is, my pipe looks WAY shorter than any other propper GRRT pipe,m mines not a MVVS item, but is full wave. is this just too short now? much more and i'll just have a stinger
04-28-2003, 04:19 PM
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Building second DD w/ FAI GRRT
Phillybaby,
After reading all your post, I don't believe you have a GRRT FAI .40 racing engine. My recommendation would get your engine up there in the RPM's department if you truly have a GRRT engine. You may want to check the sleeve/liner for the exhaust timing on that engine and find out more. Most likely, it will not be a GRRT FAI .40 because the RPM you're running are NOT even come close to the intended GRRT design. Also, the an FAI racing engine will turn at least 21,000 on the ground when it's loaded with 8x7 prop (for Sport flying), but in racing, one will mostly use a 7" diameter by 7-7 1/2 pitch and get the engine up there 25,000+ while running on the ground.
Another thing to, since an FAI racing was intended for high RPM, running a big prop like you've mentioned would never work because it's too much loaded for a high timing engine. The GRRT exhaust timing is probably somewhere around 190 degree if not more. Your engine timing based on your RPM statement sound to me more like 165 degree +/-. I hope this clear it up a little bit.
Good luck!
After reading all your post, I don't believe you have a GRRT FAI .40 racing engine. My recommendation would get your engine up there in the RPM's department if you truly have a GRRT engine. You may want to check the sleeve/liner for the exhaust timing on that engine and find out more. Most likely, it will not be a GRRT FAI .40 because the RPM you're running are NOT even come close to the intended GRRT design. Also, the an FAI racing engine will turn at least 21,000 on the ground when it's loaded with 8x7 prop (for Sport flying), but in racing, one will mostly use a 7" diameter by 7-7 1/2 pitch and get the engine up there 25,000+ while running on the ground.
Another thing to, since an FAI racing was intended for high RPM, running a big prop like you've mentioned would never work because it's too much loaded for a high timing engine. The GRRT exhaust timing is probably somewhere around 190 degree if not more. Your engine timing based on your RPM statement sound to me more like 165 degree +/-. I hope this clear it up a little bit.
Good luck!
04-28-2003, 06:33 PM
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Building second DD w/ FAI GRRT
it really really is a GRRT.
front mount lugs, tho.. it looked like the main lugs had two more drilled giving 6 total. rear induction rear exhaust, now.. wether the guts are GRRT i cant be 100% sure, but if you look at my pic the pipe is stupidly small. i stopped cutting cos it was getting stupid not because i had stoped gaining. I've seen a pic of a propper GRRT pipe next to the engine and mine was about that length, but only 14.8 on the 8x8
what i might do for a try is put on my 4" silicon joiner, then the pipe, band on the taco, and start up, don my oven gloves and push the pipe about to see what happens to rpm
front mount lugs, tho.. it looked like the main lugs had two more drilled giving 6 total. rear induction rear exhaust, now.. wether the guts are GRRT i cant be 100% sure, but if you look at my pic the pipe is stupidly small. i stopped cutting cos it was getting stupid not because i had stoped gaining. I've seen a pic of a propper GRRT pipe next to the engine and mine was about that length, but only 14.8 on the 8x8
what i might do for a try is put on my 4" silicon joiner, then the pipe, band on the taco, and start up, don my oven gloves and push the pipe about to see what happens to rpm
04-28-2003, 07:40 PM
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Building second DD w/ FAI GRRT
phillybaby,
Try cutting it down some to get it on pipe. With it being a 8 X 8 the way it came it will never get on pipe. Even if you cut your pipe to diff lengths it still wont get up on pipe.
Your rpm's are way off and it will just run like a regular sport engine with a prop that size in diameter. Cutting it down will get the rpm's up and once you hit about 17,000 or so it should kick in. If you have several props laying around you may want to try that.
Do this, cut the tips off your prop about 1/4 inch and balance it and put it on the engine. Crank it up and see if you get up on pipe. If not take prop back off and cut it down a little more and then try it again. This is what I had to do to finally get my GRRT to kick in full rpm's. Your not going to loose speed but cutting it down so give it a shot.
Once you have it cut down and it does get on pipe sand the edges to shape it like a regular prop. This is what it is going to take is a little cutting.
On my GRRT is runs to 17,000 or so like a regular engine. Then with a slight delay the pipe kicks in and it jumps to 24,000. When you do this at 17,000 rpm's it will sound like a sport engine, after that short delay it will kick in completely and really scream and make a super high pitched sound. It should sound like it hits WOT 2 times, once before pipe then second on pipe. So it will sound like it is toped out and then pipe kicks in and it revs up instantaneously again. It is not a gradual rpm's gain to where to see it on Tac gradually gaining rpm's. It goes 17,000 or so to instant 24,000. There is no in between.
Give it a shot and see how it does and let us know.
I wish I had a wave file of the engine running and getting on pipe so you will get an idea.
Try cutting it down some to get it on pipe. With it being a 8 X 8 the way it came it will never get on pipe. Even if you cut your pipe to diff lengths it still wont get up on pipe.
Your rpm's are way off and it will just run like a regular sport engine with a prop that size in diameter. Cutting it down will get the rpm's up and once you hit about 17,000 or so it should kick in. If you have several props laying around you may want to try that.
Do this, cut the tips off your prop about 1/4 inch and balance it and put it on the engine. Crank it up and see if you get up on pipe. If not take prop back off and cut it down a little more and then try it again. This is what I had to do to finally get my GRRT to kick in full rpm's. Your not going to loose speed but cutting it down so give it a shot.
Once you have it cut down and it does get on pipe sand the edges to shape it like a regular prop. This is what it is going to take is a little cutting.
On my GRRT is runs to 17,000 or so like a regular engine. Then with a slight delay the pipe kicks in and it jumps to 24,000. When you do this at 17,000 rpm's it will sound like a sport engine, after that short delay it will kick in completely and really scream and make a super high pitched sound. It should sound like it hits WOT 2 times, once before pipe then second on pipe. So it will sound like it is toped out and then pipe kicks in and it revs up instantaneously again. It is not a gradual rpm's gain to where to see it on Tac gradually gaining rpm's. It goes 17,000 or so to instant 24,000. There is no in between.
Give it a shot and see how it does and let us know.
I wish I had a wave file of the engine running and getting on pipe so you will get an idea.
04-29-2003, 08:33 AM
#36
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Building second DD w/ FAI GRRT
did you see the pic i posted of just how short the pipe is now?
when it was full length, and looked like the GRRT pipe lol, i got 14.8 on the 8x8, my mate had a tipped prop so i cut it to about 7x8 and got 15.6, that flight was crap to say the least, that day we cut about 1 1/2 off the pipe and eventully got it quick, but my taco at home shows that was about 16.8 on the 8x8, now i've cut another inch and swapped to the 8x7 i'm getting 18-18.3 i really don't want to cut the pipe more because its just getting far to short, nothing to do with space, i'm just way past the lead into the pipe, im now cutting the expansion part!
when it was full length, and looked like the GRRT pipe lol, i got 14.8 on the 8x8, my mate had a tipped prop so i cut it to about 7x8 and got 15.6, that flight was crap to say the least, that day we cut about 1 1/2 off the pipe and eventully got it quick, but my taco at home shows that was about 16.8 on the 8x8, now i've cut another inch and swapped to the 8x7 i'm getting 18-18.3 i really don't want to cut the pipe more because its just getting far to short, nothing to do with space, i'm just way past the lead into the pipe, im now cutting the expansion part!
04-29-2003, 09:10 AM
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Building second DD w/ FAI GRRT
Well, that can't be right...if you're cutting into the divergent part of the pipe, and you're still not getting anywhere, you must have the wrong pipe.
The pipe you have probably has too much volume, or the distance between the expansion and reflection cone is too long.
Get yourself a proper pipe....you will be stunned by how the engine reacts to it...
Now I have a question too...
Would it be possible to put some sort of muffler AFTER the pipe on an engine like this?
Would the resonance frequency of the engine-pipe combo still be the same with a muffler hooked up to the pipe? I think so, but what do other people think?
Provided I can construct a muffler with plenty of tailpipe area (so I get a very low flow resistance), how badly would engine performance be affected?
Has anyone even tried this before?
The pipe you have probably has too much volume, or the distance between the expansion and reflection cone is too long.
Get yourself a proper pipe....you will be stunned by how the engine reacts to it...
Now I have a question too...
Would it be possible to put some sort of muffler AFTER the pipe on an engine like this?
Would the resonance frequency of the engine-pipe combo still be the same with a muffler hooked up to the pipe? I think so, but what do other people think?
Provided I can construct a muffler with plenty of tailpipe area (so I get a very low flow resistance), how badly would engine performance be affected?
Has anyone even tried this before?
04-29-2003, 09:15 AM
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irvine make a thing called the mouse, it fits on over the muff exit, performance is lowered slightly because you are restricting the airflow out.
i know its the wrong pipe, and it does look a little fatter than a GRRT one, but not that much.
i dont really want to have to spend 37 quid on a new pipe, thats not me lol the engine cost 15 and the magnum 35 lol
i know its the wrong pipe, and it does look a little fatter than a GRRT one, but not that much.
i dont really want to have to spend 37 quid on a new pipe, thats not me lol the engine cost 15 and the magnum 35 lol
04-29-2003, 09:38 AM
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I took another good look at the pic you posted in post #30, and I think you have your pipe set way too short...
Take a look at this pic and the length of the pipe (and take into consideration that this thing is tuned to run up to 30000 rpm)...:
Take a look at this pic and the length of the pipe (and take into consideration that this thing is tuned to run up to 30000 rpm)...:
04-29-2003, 09:49 AM
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Building second DD w/ FAI GRRT
right, 4" joiner time it is.. just gotta change my sisters car stero first.
i keep saying im gonna clean my room, its a mess, looks like i'll never get round to it what with all the GRRT tuning and Micro-jet prop playing i gotta do
i keep saying im gonna clean my room, its a mess, looks like i'll never get round to it what with all the GRRT tuning and Micro-jet prop playing i gotta do
04-29-2003, 08:37 PM
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phillybaby,
On my last post I meant to cut down the prop not the pipe. I would'nt mess with the pipe until you tried cutting down props. Get the rpm's up then start tunning. Give this a shot.
Also I always understood you cut down the header and not the actual pipe. I may be wrong
On my last post I meant to cut down the prop not the pipe. I would'nt mess with the pipe until you tried cutting down props. Get the rpm's up then start tunning. Give this a shot.
Also I always understood you cut down the header and not the actual pipe. I may be wrong
04-30-2003, 04:28 PM
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if i cut down the headder i would no longer have a engine!
also i did try a cut down 8x8 which was about 7x8, to say the least it was CRAP!! the 8x8 kicked its sorry ass, i got shown up by a Wattage Mig for pittys sake lol
also i did try a cut down 8x8 which was about 7x8, to say the least it was CRAP!! the 8x8 kicked its sorry ass, i got shown up by a Wattage Mig for pittys sake lol
04-30-2003, 08:18 PM
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It sounds to me like it never got on pipe if you say it ran like crap. I would just keep cutting down until you hear it kick up on pipe. By just cutting it and flying it you wont be able to tell a difference if it is never on pipe.
Also don't go by how hard it pulls on the ground. That has nothing to do with the speed in air.
If not your pipe may already be useless by all the cutting. If I were you I would go out and buy the MVVS GRRT pipe that way it is matched with engine. The way it is going now your never going to get the full benefit of the engine by a stubble of a pipe. It sounds like you done tried everything but that.
Telling you when that thing kicks in you will know it and you will laugh at the way it is running now.
Also don't go by how hard it pulls on the ground. That has nothing to do with the speed in air.
If not your pipe may already be useless by all the cutting. If I were you I would go out and buy the MVVS GRRT pipe that way it is matched with engine. The way it is going now your never going to get the full benefit of the engine by a stubble of a pipe. It sounds like you done tried everything but that.
Telling you when that thing kicks in you will know it and you will laugh at the way it is running now.
