Mr Cox

I realize that there are only a few of us interested in small engines here, but I just thought I would post some numbers from my TT GP07 engine. It has been modified to take a turbo plug which helps the high end. On 12% nitro fuel and an APC 7x3 I get the following:
max: 16700 rpm
Idle: 3500 rpm

There is also a movie of it [link=http://www.youtube.com/v/F5sXWplWBrY]here[/link] pulling a workmate....

jeffie8696

Mr Cox. About time you joined me over here. Thought I was holding up this thread by myself. Great numbers and on just 12%, great. Can you post some additional info like your base line readings and perhaps a short description of what mods did how much to improve the performance.[8D]
Have you checked out my Aviastar.46 readings? Can you get them where you live? I believe someone associated with Aviastar is a forum member (aviapilot) . Mine isn't big on high rpms but bolt on a really big prop and watch the numbers, most engines would be choking on a 13" !![X(]
Again, glad to see you here.
And by the way, I have at least a dozen engines at or below .07

Mr Cox

There is a really loooong thread on the engine already on 1/2a forum (as you know): http://www.rcuniverse.com/forum/m_6720213/tm.htm

In summary the engine will do around 16000-16500 rpm on a 6x3 as it comes out of the box.
I've then done a few mods without being very scientific. The highest gain comes by fitting a turbo plug, this will give 1000-1500 rpms alone.
I then also did a few other things to improve the breathing, enlarge the throttle barrel and exhaust slightly. This gave about another 1000 rpms, so that it would do 18700 rpm on a 6x3 without even having touched the "inside" of the engine.

I could have stopped there but then also had a look at the tranfer channels and saw a missfit between the liner and case. I then had a go at those too (scary stuff...) and then ran it a on a 7x3 and got 16700 rpm. I haven't really dared to put on the 6x3 after the latest mod, but maybe I should just for the scientific part of it. Anyway this engine should now be able to pull something up there.

jeffie8696

Thank you for the info. Now we need to get the manufacturer to take notice.

Mr Cox

Regarding the Avistar I haven't seen any around here. But my largest engine is an SC12, so a .46 is a bit out of my leage...

jeffie8696

The Aviastar is no lightweight. It is designed for the beginner so it is large and robust. And it puts out great power!!

buzzard bait

What do you have to do to get it to take a turbo plug? Is there a commercial adaptor? How much difference does it make?

Jim

Mr Cox

You have to make a new head for it. The head is a separate part though which is held by a larger theaded clamp part, so you do not have to make any threads only a disk shaped part using a lathe. The gain on these small engines are typically around 1500 rpm and this is also why you cannot use regular plugs in e.g. cox engines although these adapters are actrually sold commercially (rip off IMHO). With a turbo plug you get a performance that is very similar to the stock heads of cox and Norvel etc. The key things seems to be that the threads of the regular plug is disturbing the combustion.

There are several guides on how to make turbo plug fittings on the 1/2a forum.

jeffie8696

OK somebody please call Thunder Tiger and ask why they don't offer Turbo heads for all their engines. I think it would be a handy accesory.

Mr Cox

Yes, I don't get it either. For the car engines they supply extra heads so why not do it for the small air ones too? [:@]

jeffie8696

You would think a forum this size would have a member connected to Thunder Tiger! I happen to know that there is a member here associated with Aviatronics, and they rock.