OS .18 TZ glowplug ?

[bjacobsen71]

Just looking for some advice here, i've gat a couple of JAE .12 based riggers that i'm getting close to finishing, running OS .18 TZ engines (max power listed at 29 to 31,000 rpm depending on source) with Macs 1324 pipes, planning on starting with a pipe length at about 8 to 8 1/4" and V-940 props, question I have is the plug OS recommends is an ultra hot (turbo style) plug, and this engine was really designed for around 20-35% nitro, keep in mind I'm at 6000' here in the Reno Tahoe area and planning on running 50% home brew (Klotz TechniPlate/BeNOL blend), I'm thinking the altitude should lower the compression enough that I shouldnt have to open up the head volume or add shims, but should I go to a medium or cold plug also, they have cold, medium, hot and ultra hot as the choices? I've got lots of car experience but only up to 30% in those, and havnt played with the boats in almost 30 years now, should be fun!

-Thanks

 

[gil sonsino]

for 50% nitro cold plugs will work fine..... MCOY 9, KB HP.,O'Donnel .... etc.

Gill

 

[shoboat]

Brett,

I would run a hot plug like a O'Donnell T-77 Turbo Plug which is hotter.

These engines love Nitro and hotter plugs. Just keep them rich so you

can make maximum power.

Thanks For Reading,

Mark Sholund

 

[bjacobsen71]

Thanks for the info, think I'll start with a medium plug and go from there. I have converted these engines to water cooled and know I'll probably have to limit the water flow to get the temps up, but any other info will be appreciated. Anyone else run the OS 18 TZ in the small boats? Will add a couple pics when I can figure out how to attach them!

 

[bjacobsen71]

 

[Jeff Barnhart]

I've been running it water coolled and it takes 66% nitro and either an odonnel 97 or 99 turbo plug just fine. I've never run anywhere near that altitude so i'm not sure how it acts in that environment. Which water cooled head are you using?

 

[bjacobsen71]

Machined my own design cooling head, uses the stock head button. Jeff, did you add any head shims for the 66% or run it stock? Also did you have any problems tuning the carb for the hi nitro? Thanks for the info.

 

[camaroboy383]

Brett,

I would run a hot plug like a O'Donnell T-77 Turbo Plug which is hotter.

These engines love Nitro and hotter plugs. Just keep them rich so you

can make maximum power.

Thanks For Reading,

Mark Sholund

i could not have said it better mark...... the hotter the better.....

 

[bjacobsen71]

Also Jeff or anyone else running the .18TZ, what prop are you able to pull, I figured on starting with the v-940 just as a starting point? I don't have the tools yet to work on props so I kinda have to stick to stock props with minor mods (no repitching or cupping).

 

[Jeff Barnhart]

Machined my own design cooling head, uses the stock head button. Jeff, did you add any head shims for the 66% or run it stock? Also did you have any problems tuning the carb for the hi nitro? Thanks for the info.

Mine is pretty much stock, with the exception of the water cooled head which is adapted from an aq .18 to fit the stock tz head. I haven't added any head shims to it, and no problems tuning the carb but I am at about sea level in the Northwest which makes a significant difference in tuning characteristics.

As for props, I'm not really sure because I have been running it in a vegas until i finish my JAE .12. I think people have had good luck with the 1440 (possibly backcut?) for heat racing. I would talk to Mike Hughes or Mark Anderson about props on that boat as I know they have run the tz in the JAE .12 boat and had it running very well. Mark Sholund would be one to ask about props as well.

 

[bjacobsen71]

Thanks!

 

[camaroboy383]

start with a 1440 and go from there....

 

[shoboat]

Brett,

V-937/3 would be a good start and then the V-940/3 or

A reduced 1440 B/C or ABC 40x53 B/C.

These will get you running very well.

Engine temps. Can go into the 260*/F range

without any trouble at all. We run the smaller

motors with no water and adjust the cooling

with our needle valve setting.

Have Fun Testing,

Mark Sholund

 

[bjacobsen71]

Thanks Mark, all this gives me a solid place to start, with a little luck might have these on the water by the end of the month! Looking forward the the testing and tinkering!

 

[gil sonsino]

we are running same engine in a Jae .12 with an Irwin .21 pipe and both V's V 937/3 and V940/3......... up to .53mph!

Gill

 

[Christopher Moore]

Running 99T plugs with 45% 18% fuel. Little video of my Jae 12 with a OS18tz with the water head. Hydro Rob built it This video is of him running it some time last year. Prop is a Mod V940/3

  http://youtu.be/Z6qrH2nz0Hc

 

[bjacobsen71]

Looks like a strong runner, what prop mods were done?

 

[bjacobsen71]

Also, what pipe and pipe length are you running?

Thanks

 

[Christopher Moore]

On the prop you would have to contact Hydrorob on that, its a Mac pipe measuring at 7 3/4"

 

[bjacobsen71]

Thanks, nice vid! Here's a couple pics of the running surfaces, essentially JAE with some additions, just for tinkering sake, don't know if they will help or hurt, but the shoes, and the "trip pads"(??) on the sponsons should run clear of the water at top speed, we'll see!