Predator 212cc 8400rpm max with torque converter clone, will it work?

[smooth90]

Hi everyone,

I have a question about my predator engine and torque converter:

I'm waiting on UPS for the parts to completely upgrade my Hemi Predator 212cc for a big RC car that I'm building. I purchased a Dynocams 308 billet cam, 32lbs spring set, new stainless steel intake valves, billet flywheel, air filter kit, new exhaust system. vacuum fuel pump, new racing tank, and other supporting hardware. The only part I'm not replacing is the piston because I don't want to have to rehone the cylinder.

I'm using a torque converter clone that I purchased here:

http://www.ebay.com/itm/191398033297?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

I'm worried about utilizing the torque converter at the new max ungoverned speed of 8400rpm. In the past I made a drift trike with some friends and in testing we redlined the engine. There is a part that expands with two guide rods inside one of the parts that expanded too much and got stuck caused the guide rod came out too far.

The standard speed is 3600rpm, and with the governor off it can hit 4500 rpm or something like that (though dangerous with the original flywheel). The torque converter can handle this but jumping up to an 8400rpm max is a big step.

In short:

If the engine revs up to 8400rpm will the torque converter simply stay locked in the final "high speed" ratio, or will it fail like our drift trike torque converter?

Also, if its too high of a speed is a jackshaft or gearbox reducer on the engine a good idea?


Any help would be greatly appreciated!

Thanks,

-Justin





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Here's s what I'll be using this engine in:

I'm currently working on building a very large scale (around 1/3 scale) RC car/kart. I'm designing it completely in the Autodesk Fusion and will be having steel laser cut, then I'll use the laser cut steel as a template to cut square/circular tubing to reinforce it.

Thus far I've dumped a lot of money into this project around $2200! I bought a set of four brand new 18in x 9.50-8 Kendra Knobby Tires with a 4x4 rim. I also purchased a hydraulic brake caliper on the rear axle (its a $220 brake kit at bmikarts). The steering system is an 8.5in mini billet rack with 24t splined shaft (I found it on ebay, it's really nice). This rack uses a coupler and a flexible coupler to attach to a very powerful nema 43 stepper motor (1584 oz in of torque!). The front suspension will be independent and the rear will move up and down as one piece with the engine.The master brake cylinder will be actuated by a linear motor and the engine throttle will be controlled using a large servo. The car won't have reverse at first but I'm going to work on that in the future once its finished.

 

[mckutzy]

I think youll need to be more worried about the rod letting go than the flywheel earlier...

In the end, Id think you'd be better off with a different engine altogether... a 2 stroke perhaps from a dirt bike, much faster rpms and lighter weight for the power it makes.....

 

[Whitetrashrocker]

And already has a trans and clutch that could be easily controlled. Then the drive train is just a couple sprockets.

 

[Scout]

If you have a way to control the clutch and shifter via radio. A centrifugal clutch or TC on the other hand needs no extra controls. Now maybe, possibly, one could use the dirt bike engine with the TC, you wouldn't need to worry about shifting, and could manually shift gears between runs to fine tune it.

 

[smooth90]

Ah, thanks for your input. I forgot to mention that I'm replacing the connecting rod in the engine with a billet one as well. I don't plan on really hitting and sustaining 8400rpm. If I do get up there it'll only be for a short sprint at max speed. I'm already pretty invested in this engine so I'm gonna go forward with what I have.


I looked at other engines too but I went with the Predator because it was cheap, easy to work with, and the fact that I'd used one before. The total cost of the engine with all the upgrades is about $650-700. The Lifan engines looked good and maybe I'll use one in the future. The whole process of automating a manual transmission was a bit complicated. I found one for $400 (just the engine) that was a 200cc four stroke with a 5-speed manual transmission built in. In the future, I'm definitely gonna build something else like a mini-bike and when I do I'll take a look at another type of engine.

Engine upgrades/modifications:

Hemi Predator 212cc
.037 carb jet with bored out emulsion tube
Angled air filter
New exhaust with screw on muffler
Billet flywheel
Billet connector rod .308
DynoCams 308 cam
28mm (exhaust) and 32mm (intake) stainless steel valves
32lb dual valve spring set
Fuel pulse pump
One gallon aluminum racing tank
No governor
Oil sensor bypass
Throttle linkage kit from OMB

I haven't found any videos of a torque converter fitted to a modified engine like this. I'm just not sure if its gonna be too fast for the torque converter.

Engine aside....if I drive a torque converter at 6500-8400rpm (max) will it simply lock up or will it expand so far that the mechanism fails?

Has anyone had problems with the torque converters (original or clone) at higher ungoverned speeds?

---------- Post added at 07:19 PM ---------- Previous post was at 07:07 PM ----------

If you have a way to control the clutch and shifter via radio. A centrifugal clutch or TC on the other hand needs no extra controls. Now maybe, possibly, one could use the dirt bike engine with the TC, you wouldn't need to worry about shifting, and could manually shift gears between runs to fine tune it.

In theory, I can RC anything but it could get pretty expensive. The steering motor alone was $200 plus $150 for the driver/flexible coupler for it. In order to RC the shifter/clutch I'd really have to have the engine in front of me. I think the bigger problem is that I'd have to either shift manually with an RPM/speed readout on the remote controller or I'd have to make it automatic with a custom circuit/software to do the shifting. I think making it automatic would be best for an RC setup. I like the torque converter because it's better than a standalone clutch in terms of speed/torque and plus its automatic, one less thing for me to worry about when RC'ing this thing.

 

[Whitetrashrocker]

Once the TC hits 4k or so it's not gonna go anymore. The travel is only so much.

 

[smooth90]

I think I'll go ahead and give it a try then. I guess the worse case is that the torque converter partially fails again (described below). If it doesn't work I'll make a jackshaft reducer to reduce the rpm range.

Anyway thanks for the input

I had a torque converter sort of fail once before, it wouldn't work until we opened it up and fixed it (no new parts needed). There are these two guide rods (about 1/4" diameter and 2.5-3" long) inside the pulley (engine side) on the torque converter. As it spins faster the centrifugal force expands the two "halves" (against the spring that's wrapped around it). The guide rods keep the two halves aligned (one-half has the two rods screwed or press fitted into it, the other has holes that the rods slide in). These might not even be visible unless the halves are partially separated but they are in there.

The torque converter stopped working when the halves expanded so far that one of the rods actually came out of the hole it slides into (in the other half). Once the rpm was lowered the rod wouldn't go back into the hole and got stuck. I took it apart and had to remove the spring, bend the rod back a bit, and reassemble. It worked after that but it was kind of an odd problem.

 

[KartFab]

I got the 40 series up to 5500 rpm, and the 30 series to 4400 rpm with no problems so far.

 

[bob58o]

My Predator 212 / 30 series TC Minibike used to see 7000+ RPMs everytime I took it out.
But it seems as tho that is more RPMs than most feel comfortable with.

Most people building an engine that is going to turn 8400 RPM will try a more expensive clutch over a TC because belts tend to slip at high RPMs

 

[ezcome-ezgo]

Belts slipping at 8400 rpm = fail/fire/danger/fun (or FFDF)

 

[KartFab]

I'd at least put a nice guard on the torque converter and tgreadlocker on the drive unit bolt. Seems like a lot of 'failures' on these units are caused by the bolt coming loose.

 

[smooth90]

I'm gonna have steel and possibly aluminum parts laser cut for the whole frame so I should be able to put together a nice guard for it. The stock plastic guard would probably fly apart. If I have problems with the belt slipping then a jackshaft reducer should work depending on how much torque it creates. I guess the one real benefit to this project is that its RC so if any of the parts fail I'll be at least 50-70ft away instead of being inside the cart.

I have an old clutch that was about $175 that still might work. I worked on putting an 800cc 2 cylinder Onan boxer engine into a Chinese 2 seat kart frame a while back. The clutch burnt out once for maybe 5 seconds after which I scrapped the whole project because I couldn't find a drive train for the torque (at a decent price). There was lots of smoke but the clutch pads still looked good. I guess worse case I can replace the pads/shoes inside it. It also had a number of spring upgrades available for higher engagement ranges.