Talked to Bob Davis today. looks like TT did an upgrade on the 07, it was a wimp. Bob is going to see if how it is as a diesel, it is a screw on head he has not decided on a complete screw in head or a button iinsert, Don't get you hopes up yet but this could be an answer for a half A diesel a little over 3oz if all goes well martin
would maka great park flyer conversion, to complement the OS10 and TT10

After Bobs move th a bigger shop, the CNC, set up, he has decided to take a week off .Have fun Bob

I have ordered the new GP 07 after looking at the parts listing,, they show a head and a combustion chamber thus 2 parts I would guess a combustion chamber is the glow insert for the plug. As soon as I get it its going to Davis he thinks a diesel insert can be done with the thumb screw and spring ala the OS 10 and should be inexpensive $20 ?? this engine has both beam and radial mount
features nice for small stuff, no engine mount beams, just bolt to the firewall and its only 3 oz martin

WARNING this the the new one GP 07 do not buy the old one if you are thinking about this , I will report back if this all cones together
test run and let you guys know how it does

Nice to see some more people having a "go" at this engine.
I've seen reports on the newer version and the performance is not better than the "old" one...
The only visible changes are cosmetic to the case, the rest looks the same.

The glow version is weak but quite easy to bring up proper power, the head is a two piece (as said above) and it is therby quite easy to remake the combustion part as there are no threads to make.

Places to get more power from on the older glow versison:
- make a head that takes turbo plugs
- enlarge the throttle barrel
- enlarge exhaust outlet
- remake the case so that the ports in the case and liner are matching

These changes will take the power right up to pair with the Norvel .074, i.e. around 16700 rpm on APC 7x3.
Here is a short movie of it pulling a work bench: http://www.rcuvideos.com/video/Film-TT-Gp07-wmv

I've since then used it a scooter and the power is more than enough, rogs of grass at 1/2 throttle and idles around in the sky for a long time...

I do have one issue though. The plain bearings are rapidly being worn out! [:'(]
I've used fuel with 20-25% of castor and the crank gest sloppier for each flight, just a warning as a diesel version may put even higher forces on the crank. Both from higher compression and larger prop. I don't want to discorage anyone here but just be aware of this weak point.

I had another question, will you be running in the engine on glow?

Would be interesting to see what numbers you get. The old ones would do about 16500 rpms ( 10% nitro) on 6x3 props and from what I've heard the news ones are not any better...

I really like the way this engine runs though, it draws attention at the field and people at the field ask about the size and seem surpriced by the performance, it really runs like a much larger engine with easy hand starts and reliable idle etc. If only they had made a pro BB version also...

Just thought I would throw in a picture of the head part that one would remake. The left one is the stock one for a regular plug, and the right hand one is the one that I've made for turbo plugs.

Mr Cox, you are misunderstangng since here are forum for Diesel engine lovers "Everything diesel"..

AMB asked after the cylinder head with contrapiston inside instead the cylinder head with glowplug to run as diesel engine.

I has the Thunder Tiger 07 GP converted as diesel engine

Motoboy- How does yours one as diesel,? As far as Mr cox goes , we have a starting point, it will have to be run in on glow first anyhow so it is useful info
we will have an A/B comparison glow/vsdiesel martin

This could be the Norvel 074 replacement, The video was useful seems to throttle ok I do not know about the porting but as diesel the carb should be fine yiu want a smaller one anyhow. I did notice the purple anodizing the one shown on the TT site is plain now, guessing this is the newest version so maybe improved on the breathing

Just checked the TT factory site 4:30 PM the show about 5 pix of this engine looks goodIT IS NOT ANODIZED heence the newer version it is bronzed bushed

It will have a home the Goldberg lightnin Bug

Yes I'm aware of which forum we are on, I too like the diesels but I'm having a hard time finding any fuel locally.
Some people break/run in their engines on glow as it is easier to not have to fiddle with a compression screw at the important early stages of running in the engine.

What performance do you get with yours as a diesel?

AMB, the picture on Ace website show something that looks unanodized but it is also a black and white picture. The only real changes I can see are cosmetic changes to the logo on the case and the upper fins of the case. Everything else is the same including the bonze bushing, which is wearing away quickly on mine.

TowerH seem to be selling the newer version, at least it has the new case but it is still anodized:

Mr Cox the bushing wear is a puzzle, I do not have this with the GP10 Davis diesel head, does seem strange you have plenty of lube with high castor content and quite sure you do not have high vibration issuemaybe a bad bush to start with>>?? or over bored would create slop martin
Have you checked the shaft for any rough spots??

never thought about that it is a B/W pix anodizing

The older TT 07 GP engine has bronze bushed bearing with purple anodized head. But the fit between crankshaft and bronze bushing are a bit loose fit as new engine.. Do not affect leakage since the engine get enough oil to seal between crankshaft and bronze bushing.

My engine has cylinder head in steel with contrapiston in steel with O-ring. The purple head are a ring retainer for the cylinder head.

The engine are running well as a diesel engine, much better than running as a glowplug engine.

JENS As with any conversion it should have more torque than glow and swing a bigger prop no surprise here I would also guess it would hold heat more with a steel head and contra
I do not know if the rods are bushed martin

Mistake 2 in my life selling my 23ft north sea design open boat with 2 cyl Bukh diesel fuel consumption about a gallon an hour, I had bought a blank hull and finished it off myself

Yes, I should take mine appart and check the crank to see what is going on. I also have a spare case but if the crank is the problem I should replace that one too. Might be better to just get a new one then...

From memory the connecting rod is made from aluminium, "dog-bone" type without bushings.

I would just like to clairify a few things regarding power in glow version. The stock head uses a regular plug and this is a great power robber as the threads of the plug are included in the combustion all the way up to the copper gasket. This is one major difference to e.g. Norvel .074 wich uses a glow wire integrated in the head. Using a turbo plug eliminates this and gives an extra 1500 rpms. This would not be an issue with a well made diesel head, the power should come right up.

The mods to the throttle barrel were minor. The bore on mine was conical, which made the engine run to lean on the low end. I simply enlarged it slightly to an even diameter of 3.5mm which is still small enough to maintain a good idle.
The exaust was also enlarge a little and these two changes gave around 1000 rpms as compared to stock.

Together with matching the channels the power is then on pair with the Norvel and this is promising also for a diesel version.
I think the transfer channels can be left alone and the breathing could be improved on depending on the application, so just go for it...

I almost forgot what I wanted to say here (please stop me if I ramling). I took my engine appart tonight and the connecting rod looks much better than I remembered. It is not bushed but it looks strong and has a lubrication hole (see pict below).

I cannot find anything wrong with the bearing surfaces of neither crank or case. Both parts look shiny and well mated, it is possible that the mating prosses is what I have felt and misstaken for a large wear, but still I cannot believe that it is meant to be this sloppy. I can clearly wiggle the crank in the radial direction. [:'(]

Fitting the crank in a new case gives exaclty the same sloppiness, I find it hard to believe that it would be the crank that has been worn rather the bronz bearing though. Guess I will just have to run it some more and see what happens...

The rod looks quite robust compared to the norvel or paw this should make a good diesel conversion ( Jens already done one) martin

An other thought is the 18 done the same, a button???, you guys know where I am going with this idea martin

MDS15 killer

The TT18 does not seem to have the compression that a diesel needs.

THX so much for the 18 martin

So the piston-liner fit is not tight enough (?) is that a general problem with ABC engines turned into diesels?

Mr cox it is NOT a problem, conversions are from glow (check to Davis Diesel site) Even ringed engines work well my ST 40 has a davis head and it light s right off with an electric starter
it will not hand flip start due to leakage past the ring on hand start with a fast spin with a starter it lights right off . my OS 1.08 conversion has very little issue and flip starts
The "cream of the crop" are my irvine MRKllls Davis heads they are true ABC and as glow they had great compression martin

Okey, so what is the problem with the TT GP-18 then?

Good question do not know the answer on that one . Is it just a few engines or the whole series of 18s design? Fit piston/liner anyone have an answer?? martin

Finally located one at Tower Hobbies in stock, and on the way 49.95 . I will send up to Davis Diesel to see if a diesel insert button can be done
We will see it is not noted as the strongest (power) for its size but is light and has a radial mount , maybe as a diesel it will pick up some punch martin

thats the GP07

The low power comes mainly from the use of a standard glow plug, the threads of the plug becomes a part of the combustion chamber. With a proper glow plug like a turbo (or Nelson) one the power is fine on glow. As a comparison all cox and Norvel all have a button plug, and loose a lot of power if one would put and adapter for a regular plug, like the ones sold by Meccoa for instance.

So the low power of the stock engine is not a good measure of the potential. It can quite easily be put on pair with the Norvel and it should work very well as a diesel.

The only thing do I have an issue with is the sloppy crank, there is a clear radial play straight out of the box...

I think it is an excellent project, please keep us updated on the progress and good luck!

Mr Cox it should make a good conversion, In the same catagory are the OSLA series a good long lasting sport engine but not known as a powerhouse,As a diesel with the Davis heads its a whole new ballgame they turn on lots of torque, big props, there are many posts on these if you go back on this site martin