AE Pilot

OS .12 TZ? Sheesh, that engine friggin' rips! [X(]

I wonder what the compression ratio is? Is the combustion chamber smaller in diameter and deeper in depth compared to "normal" engines?

Yeah, I'm jealous.

AE Pilot

Thanks for the description. By nature, I like to tinker with things too, so I'm perfectly content fabricating, building, tinkering and tuning as opposed to actually driving. We've been dealing wih 2-stroke race engines for years (dirt and road race bikes), so tuning is definitely my thing.

Looking forward to the pictures. [sm=wink_smile.gif]

[quote]ORIGINAL: Xyzzy

Wide Open

yep, the chamber is small around but it has a fairly long piston and stroke. (i can take a picture of the chamber this afternoon if you want me to) they also bored out the crankshaft a bit for smoother fuel flow. ive got it limited to 90% throttle out of 120% on my transmitter for full throttle and it still overpowers the chassis. when i was driving it out in the desert i was driving it on very loose sand. it would wheelie at full throttle after it cant speed up anymore by the slightest bump even though i had the slipper clutch loosened.

i can definatly say that the compression ratio is quite high because when it was new my starter box couldnt even turn it over with the glow plug out. i had to put after run oil in it, heat up the engine block, and turn it over with a drill connnected to the crankshaft to loosen it up enough to start the first time. once you do get it started, though, its awesome!

driven_by_demons

Ok, my GT2 RS came last week, I spent the weekend breaking the engine in. Now I am going to break it down and clean it and check all screws. Any suggestions on what would need adjusting since it is still 'out of the box'. Going to try and race it this summer, so any suggestions would be appreciated.

Xyzzy

TZ:

bore = 13.8mm
stroke = 14mm

Some people might say that is a long stroke engine but I'd call it square. The TG uses the itentical dimensions.

I had TZ initially, but since we are newbies to stadium trucks we sent it back for the TG. I could only get the TZ to turn over after hitting the heatsink with a heat gun to 180F. The pinch was very tight. The TG uses a different (cheaper, but more newbie friendly) construction (ABL versus ABC) and has less pinch. And, the TG has a warranty. The TZ doesn't.

Supposedly, the hot trick is to put the 5 port TZ crank in the ROAR-legal 3 port TZ. There isn't anything in the ROAR rules that says you can't do this, but they do specifically prohibit 5 port engines.

Xyzzy

Our goal is to actually race this GT2 on-road. My son is only 6 so we have a year or two of basic learning to do. There is a real nice on-road track nearby we can practice at. We wouldn't be remotely competitive with a 2wd truck, but we'll have fun practicing. I was going to get a NTC3, but the 4wd made it much more complicated, plus the ride height is so low we'd never be able to drive it in the huge parking lot behind our house. Unlike 15-20 years ago when I raced buggies, there are no off-road tracks close by.

Obviously, there are a few modifications I need to make to get this ready for on-road use. We are looking at some road tires and some geometry changes. Like, for example, the toe-in (?) on the rear wheels scrubs a lot of speed off to get stability. That's fine in the dirt but on pavement it will be a problem (I think). We also need to stiffen up the shocks a bit and lower the ride height a bit

WRT the wire routing: If it did become a problem I could just drill a small hole in the side and secure the wire with a bit of a rubber band or something, but as it is now, it is no issue. I've also included the preliminary wire routing for the rear battery. I'm not sure it is the cleanest way to do it. I'm open to suggestions.

The only mods we have made so far are Lunsford turnbuckles, hinge pins and front axles. The servos hopefully will last for life. We run them in "HRS" mode and they are scary fast. We bought a synthesized Tx/Rx combo. The last radio I owned was made in the early 90s. Things sure have changed. We also bought the FT starter box and a pile of rechargeable batteries. I feel like I have more batteries now than when I ran electric!

To tame the engine for my son we are running a low power engine (0.7HP), the tallest gearing available, 0.8mm clutch springs, a rotarty carb (We have a slide carb, by accident, sitting here) and we have a "smoothy" pipe on perpetual back order. I figure the above combo will give it a soft takeoff. The neighbor kids all have Revos and stuff like that but all they do is go 50mph and hit stuff. Our goal is to not crash.

I apologize for the crappy quality of the pictures. My camera has very poor macro capabilities.

PS - Just to give you an idea of how old school I am, I sure miss the beadlock tires on the original RC10! Too bad they don't make beadlock tires for the GT2. Gluing tires is something I have always hated.

rclynx

If you look hard enough you will find bead locks for it

Xyzzy

Even for the Posi-Lock rear wheels? I know I can find front ones.

AE Pilot

Unfortunately, you cannot adjust the rear toe on the GT2's. How it arrives or assembles is how you run it. You can adjust the camber to accomodate a set of on-road tires, but that's about it.

Personally, I think the TG's are great and with the price of nitro fuel, the fuel economy is great. I run a tank out in about 6 minutes flat, but the TG's are supposed to run a tank out in about 15 minutes or so.

I would think that the GT2 would do ok in the corners against a TC, but if you're racing on a circuit with a long straights, forget about it.

Thanks for the pictures. The Macro was fine.

Xyzzy

It began life as a SG crank, slide carb TG. (I ordered the wrong one.) So I ordered a rotary carb for it. Setting up the clutch and stuff was pretty easy with the SG crank, but I'm not sure it was $40 easier. (The rotary carb is usually $60 but I had a $20 off of $50 coupon.)

http://www.osengines.com/engines/osmg1986.html

(Anyone need a 12D slide carb?)

AE Pilot

Sorry about that. I looked at your other post and realized that you had a TG and adjusted my post accordingly.

Xyzzy

This is where we hope to practice:

http://www.thercspeedway.com/

AE Pilot

I think you'd be ok. The only other general problem I see are the lane barriers. Since the wheels / tires are tucked into the fenders on TC's, they could come in contact with and/or rub against a barrier without really impacting the speed or momentum.

With an ST, since the wheel would be in direct contact with the barrier, the decrease in speed would be substantial, not to mention the possibility of rolling the truck over, spinning out of control or simply going right over the barrier.

Xyzzy

Any tips on how to set it up for pavement? I'm thinking, for starters:

http://www.prolineracing.com/product...wproduct&id=16
and
http://www.prolineracing.com/product...product&id=186

(Ultra firm foam would be less squirmy, right? And we don't need the impact cushioning of a soft foam?)

I haven't been able to find any "set up yer GT like a TC" web sites yet so any tips are appreciated.

I know less than zero at this point.

xenergyx

The ultra firm foam is a good idea. Most on-road cars have low profile tires so they are naturally sturdy but with the high profile on most 2.2 ST tires you may need the firm foam to help hold it up when you are gripping through turns.


Cleaned my truck today just to drive it and get it dirty a few minutes later.
Anyone else familiar with denatured alcohol? From what I read it did not affect plastic parts but it seemed to give some of my plastic parts a cloudy shine to them till I wiped them down with a dry shop towel...

AE Pilot

I haven't seen any of those articles ether, but I definitely think you're on the right track. I have the RTR and if I'm not mistaken, you have the Factory Team with the threaded shocks, so our shocks are different and I'm not entirely familiar with yours. However, if I was doing a complete on-road conversion, I'd start with lowering the ride height, thicker shock oil, stiffer springs and take it from there.

The Speed Hawgs are absolute jokes, so get the Road Rage tires. They will probably be closest to what's being used on TC's. The tires on the TC's are far stickier than the Proline tire compounds, which is probably why Proline doesn't produce a TC tire.

We use the dual-stage foam, but for an entirely different reason. Since we use the low profile Road Rage tires, we use the firmer foam inserts to prevent the tires from bottoming-out or compressing against the wheels from hard landings to prevent shock transfer into the chassis, but moreso to protect our investment in aluminum wheels.

The dual-stage or ultra-firm foam would work great for what you described too.

Xyzzy

Okay, I'll get the Road Rage tires. Do I run the front and rear? If the tires are lower profile does it change the gearing much?

I'm curious why the Speed Hawg tires suck so much. They look a lot more aggressive and they use the same M2 compound. Is it the tread pattern?

Should I be looking at aluminum wheels? Are there Posi-Lock aluminum wheels?

I'll probably order the tires and foams and some wheels (plastic or aluminum I don't know) this weekend. I have a bit more building to do but I hope to get this thing operational soon.

If I ran *strictly* on-road, and in clean parking lots, would this air cleaner be adequate?

http://www2.towerhobbies.com/cgi-bin...I=OSMG2384&P=K

(The kit air cleaner doesn't fit.)

AE Pilot

Yes, front and rear RR's and no changes to the gearing ratio are needed.

In regard to the Speed Hawgs, that's just my opinion, but just looking at them, I originally thought exactly what you thought, but that was definitely a mistake. We went to several parking lots to try different surfaces and couldn't get any traction. Between the RR's and SH's, I had better traction with the RR's, but that was just my experience.

If you're racing, stick with dish / plastic wheels. I use aluminum wheels just to zip around in parking lots when we're not at the track practicing. If you're looking for something other than dish, but just as durable for racing, RPM makes a wheel called the "Bully" and a few others that look decent.

That filter looks fine, but what's goal, more air flow or keeping the motor tame for your son? In general, if you're driving in a relatively clean and debris free enironment, you can use a single-element filter to promote better air flow into the carburetor. If you're trying to keep the motor tame, use a dual-element filter.

AE Pilot

Other than tuning, the RTR's really don't require any adjustments. For racing, you should start looking into a .12 engine.

xenergyx

^^^ The only thing I adjusted after break-in and my first quart was tightening up my differential a quarter turn.

Other than that, be sure to pop the white plastic restrictor out of the carb if you haven't already...

AE Pilot

By the way, why aren't you using the slide carburetor?

aaron2u

My Feedback: (2)

A good on-road setup back when I was racing, was stiffer springs, higher weight shock oil, and limiters inside the shock bodies, some people ran sway bars as well.
I used to run indoor carpet gearbox class and did pretty well with a FTt3 by setting it up this way. We also ran foam tires, but when we did parking lot races, we didn't change a whole lot, other than gearing.

I just fired my FTGT2 off last night with a fairly new tz 5 port.... This thing is soooo sick! Wheelies on ashpalt? Wow, and only half throttle! Speed hawgs hook good on warm ashpalt!

dannthenitroman

Xyzzy- Check my thread here, you will want to go with less rear toe and front toe out.

Lay the shocks down and go with much smaller shock pistons and much thicker oil.

read this perhaps.

http://www.rcuniverse.com/forum/m_5521163/tm.htm

Dann

xenergyx

Xyzzy - I was looking around on the site and saw someone with an old GT that used NTC3 shocks in it to lower their ride height for on road.

Dont know if they would still work with the GT2 but its something to think about.

Maybe some anti-roll bars even?

Xyzzy

Less low-end hit. Simpler linkage. I can always add it back later. Or put in a a TZ I suppose.