bob62

My Feedback: (28)

We have installed a pipe on this engine. On open header with a 10-6 prop we are getting 11,900 rpm's. We installed a cliped wood prop that was a 10-6 cut to a 9-6 and 1" of header pipe off and we are know turning 12,400 rpm'. Our question is should we cut more or leave it alone. We have some apc props coming in a 9-6 but don't have it yet.

Cyberwolf

My Feedback: (4)

I keep cutting as long as the engine is gaining RPM's. You will reach a point where it will stay the same or may drop a little, if it drops add the last piece back inside the tubeing to gain back what was lost. I only cut it 1/4 of a inch at a time towards the last so not to cut it off to short.
Macs tuned pipes and mufflers has very good detailed instructions on how to do this very thing.

Diesel Fan

Wait, let me get this right.
You have a G 21/46 Tigre with just 'an open header pipe' for the exhaust?

No muffler or other kind of plumbing anywhere? Or is it with a tuned pipe included?

Wouldn't have thought that those older engines really responded to pipes but have you considered the MVVS style mini pipe at all?

jaka

Hi!
If my memory is correct that is a .46 engine? Right? 30-40 years old...!?
I would think a 9x6 prop is too small for most applications... if not ofcourse in a pylonracer. For most sport planes a 10x6, 10x7 or 11x6 APC or RAM are more suitable

Instead of using a full lenght pipe I would recommend a mini-pipe like the MVVS or Nelson pipes. Those are plug-and-play typ pipes where no adjustments are made.

As has been said earlier if you use a full lenght pipe you have to cut the header centimeter for centimeter,one at a time, and try what works best, but this is both time consuming and bothersome as many factors like prop size, head clearence, glowplug and nitro content also play their roll in the equation.
Using a mini-pipe you only have consider head clearence (shimming the head) for max performance and choosing the correct size prop...nothing else!

When using a tuned pipe have in mind that the compression rasies in the engine due to the pressure build up in the pipe and as so do not use too much nitro. 5% is a good start and is all our modern engines need to perform just perfectly. Using 15% nitro can make life difficult when using a pipe and is also much more costly!!

OS 8 or Enya 3 are good glow plugs to use that allways works!

Sport_Pilot

Just cutting the prop and reading the RPM will not tell you what you need.  If you are racing you have the wrong engine.  For sport you probably need an 11 " prop.  A cut down prop will usually not perform as well as a non cut prop of the same diameter.

bob62

My Feedback: (28)

To Jaka and Sport Pilot

What we are doing is most likely dumb, we wanted to make some thing fast, the Super Tiger is a engine i brought on a used airplane when I got into radio control. We have purchased a Great Plane P-51 Combat plane to install this engine on. We thought by installing the pipe we could get a little more power out of the engine. This plane has no landing gear so we purchased a set of electric retracts from Hobby People and installed them. I am not much on hand lanch. We will look into the pipe you are talking about. I have a flying buddy that has some Jett pipes for 40 size engines, we might try one of those. I appriciate your imput

Bob

Recycled Flyer

Hi Bob,
please bear in mind that the MVVS mini pipes tune cuts in at about 13 000 rpm and the full length pipes probably about 3 000 rpm higher than that.

Find out where the tune starts with the Jett pipe firstly and see if that compliments the torque curve of your engine - my guess is that it probably won't due to the fact that Jett engines (and similar modern engines) are designed to rev much higher and thosepipes suit those engines.

Anyway, get the info on the Jett pipe first!

1QwkSport2.5r

The red Jettstream pipe isn't going to work for you much unless you're turning 15,000rpm or better. The pipe doesn't really start working until you get over 15k with the peak performance in the 16,500rpm area. To get an older engine turning rpm like that is gonna require modifying the exhaust timing to be able to use a prop that's flyable. I have one on a thunder tiger pro .46. It gives up 15,300rpm on a 10x6 APC. Stock muffler gives 14,250rpm. It really shines on a 9x7 at 16,800rpm. Though a 9" prop is a bit small for a 40 sized plane probably.

Recycled Flyer

Precisely why I recommend the MVVS pipe, just start off with a longer header than normal as you want to match the tuned volume of the pipe to the engines capabilites.
(The longer the header the lower the rpm necessary to "get on the pipe.")

dennis

My Feedback: (90)

Your wasting your time trying to make a performance piece out of this engine. It's timing is mild and will not do much in the speed department. It was highly prized by the c/l stunt community for it's well behaved manners with reasonable power levels and it's ability to deliver a 4-2-4 run. A speed engine it most definitely isn't.
Also consider that parts are getting really scarce for this engine and if your unlucky and break something you just might be out of luck.

Dennis

cutaway

The G.21 35's cranks and stock rear main bearing were notorious for grenading when run hard with small props. The .46 is a similar engine with a lot of commonality between the .29-46 sizes.

I put a .46 in an Voodoo with the .35's wide open pressure venturi a while ago running a 9x8 and it was a pretty wild ride on just 80/20 FAI fuel. I don't expect the engine would last being run like that though.

If you want a vintage Tigre that was designed to be a screamer, look around for an old G.40 or X.40.

MetallicaJunkie

is it a baffled type crossflow scavenged or Schnuarle ported.... for a tuned pipe setup those numbers are low , especially if it is a Scnualre ported abc type engine

a stock 45 will do mid 13s easily with a 10x6 prop

w8ye

My Feedback: (16)

The G21/46 is a cross flow design

MetallicaJunkie

that explains it...


i remember the first time i disassembled a crossflow type engine, i thought it had the coolest looking piston, and that i had a special engine....

bob62

My Feedback: (28)

After 2 hours in the oven the liner would still not come out, so we are going to run it like it is. If it blows it blows

w8ye

My Feedback: (16)

My experience with the oven is that you cannot let all the parts get heat soaked. If you can just have it in there for 15 min so to heat the outer aluminum jacket up without getting the sleeve too hot will work better.

bob62

My Feedback: (28)

I did that the first time, say about 20 min.. It would not give, tried socking all night and that did not work either. Second time in oven for two hours on very low heat. Would not move, gave up and put back together. Will run like it is, engine runs good, but after a couple of run compression not so good

Bob

w8ye

My Feedback: (16)

What about a new ring?

You can get a new ring from Frank Bowman


I guess if you cannot move the sleeve, you cannot put a new ring on the piston either? I forgot!

Cyberwolf

My Feedback: (4)

When I get an engine that has a stubborn sleeve like that, I use a propane torch on the outside of the case to heat things up. But before that I have a prop installed and use a popsickle stick pushed through the exhuust port when I figure I have enough heat on the case I turn the engine over with the stick in place as a rule the sleeve will move just enough to break the crusted seal it has on the case and from there on it will remove fairly easy. I don't know if there is an alignment pin on that particular engine or not, but if not use a scratch all and make a mark across the top of the sleeve and case for reassembly, plus an arrow to the front on the top of the piston. Just a witness mark is all thats needed. By all means do wear some heavy gloves while doing this or you will get some severe burns. You may need to heat it up a few times in order to get it out. Also make sure you move the torch around the case in order to get a better overall expansion. I have found that this works better than the oven for me, your milage may vary.

downunder

As Cyberwolf says but with a ringed engine that has many divided ports I use a match in every port to spread the load and take special care if it's a Dykes ring.

bob62

My Feedback: (28)

I will put some STP in it and build up the compression