1QwkSport2.5r

The problem with the bigger car engines is the fact they are mainly aimed for big heavy monster trucks. A high strung revver is going to be way too loaded down to perform well. That's why the 'real' racing class is 5-7 pound buggies that will do 60-70mph with .21's. I don't know of any reasonable big block that can (stock) beat the pants off a race .21.

I don't care what the manufacturer claims. I use a tach to determine just how fast they're turning, that is a real world comparison tool. Not the 2.5hp it makes today and 1.4hp tomorrow. Blah blah.

I'll have to get some bearings for that little HPI .15 of mine and try getting a prop on it. I'd like to compare it to the K&B .18.

Is there a transfer port drilled in the skirt of the piston in either of those engines you have pictured, Mr. Cox?

Mr Cox

Yes, the boost port goes through the piston while the two transfer ports are in the case. It is the same/similar for the two engines.

The piston skirt kind of blocks the two transfer channels though (at BDC), and it would have been good to raise the piston skirt in those regions I think.

1QwkSport2.5r

Yeah, these engines were not designed to be powerhouses as has been noted so far. I'm sure some time with a dremel and a lathe could make these engines run a lot better/stronger.

But if the price is right, by all means... Take the blue light special and run with it.

airraptor

My Feedback: (66)

most all ot the large big bore car engine even the 21s have a pilot shat on them for the clutch. very very hard to put a prop on them but can be done.

1QwkSport2.5r

The clutch and flywheel mount directly to the crankshaft. The pilot shaft is only installed if using a pullstart or electric spin starter. The bump start engines have a normal backplate like aircraft engines do, and no pilot shaft. The remedy for the short crank is either swap in a long crank or use a crank extension. Or make your own flywheel/prop driver.


Where there's a will there's a way.

jeffie8696

He is referring to the long shaft at the crank snout (SG)for mounting the clutch not the starter shaft. A lot of RC car engines use the long shaft crank but not all.

mtntopgeo

My Feedback: (12)

As has been stated earlier. the engine is a Toki. Fairly lite, no bad manners, easy start, & not very powerfull. Exhaust is the biggest problem. Almost any muffler, including the stock unit really pulls the rug out from under the performance show. Got tired of trying different mufflers, so set up a small mousse can. Didn't gain anything, but didn't lose any thing either. However, the can was just as loud as open exhaust. Finally remembered a muffler that I put on an old Enya .15 baffled piston unit. It was quite effective, so tried that on the K&B .18. it actually wokked great. Almost no loss in performance, & very quiet. Looked at the squish distance; 'bout a mile & a half !!!! But by this time I lost interest in the thing & just used it with the enya muffler (SM 154). Can't remember if the bolt pattern was exact, or if I had to drill out the engine case a few thou oversized. Performancewise, consider it a nice 15 size engine. (Works great on a Lil' Extra) Mine gets 16,600 RPMs while spinning a MAS generation 2 (not the GF3) 8x4, & 19,200 with a 7x4. Both figures were with the Enya muffler attached. .......... If you play with ports &/or squish, let me know what your results were. I just might have to fire up the lathe & start looking for the dremel, too. .................... George K.


EDIT; Forgot to list the fuel.............. 15% nitro 20% oil (1/2 make-believe oil, & 1/2 real oil). ...... No difference in Performance when fuel mix was changed to 25% nitro. ..... George K.

Mr Cox

Thanks for the numbers, those are certainly fine for a .15 engine in terms of both size and weight.
The muffler bolt distance is the same as most .15 engines (it comes with an OS .15 muffler with baffle), so the Enya .15 muffler should be a direct drop-in too. There is also the ASP .15 muffler that one could try, it doesn't have any baffle in it.

Sport_Pilot

Actually most sport .15's get only about 14 to 15 K on most 8-4 props, not the 16+K he reported.

airraptor

My Feedback: (66)

if you do go and mess with the engine the crank timing is off also.

proptop

My Feedback: (8)

It must be fairly conservetively timed too then...? Although 16K+ on an 8x4 is pretty good...
Even with the tuned pipe on it, the Toki .18 in the DF unit didn't exactly set the world on fire...the rather choked internal passages don't help.

Several years ago, I did a little massaging of the innards of the HPI .12SS in my RS4-3SS...it looks very much like the pics shown here. The engine responded quite nicely...(I didn't do anything to the timing...just cleaned up the areas in the flow path )

Mr Cox

Have you measured it then?

proptop

My Feedback: (8)

Here's a little something I just stumbled across:

http://www.mecoa.com/toki/brands/brands.htm

1QwkSport2.5r

So perhaps the HPI/K&B engines Mr. Cox has are made by Shuwa, and the HPI .15 I have is made by Toki then.. Interesting read.

Mr Cox

Just a little update on this engine. I've had it put away in box with a few other engines that I haven't been happy with...

I have it running fairly well now and there is nothing really wrong with the engine, it just doesn't perform well straight from the box with the supplied muffler. I've tried to measure the timing and intake is fine (opens about 38° ABDC and closes 49° ATDC), while the exhaust is quite long (around 157°) due to a large chamfer on the piston. So long story short, it mainly just needs a better exhaust.

The carb also has a rather strange restriction in the lower part which is smaller than the barrel opening. I've removed that but ended up reducing the barrel opening instead.

So with a Mac's header, and a car style muffler, it now spins an APC 7x4 at around 20000rpm (10% nitro and an extra head shim) and throttles fine (low end is a little too rich though). So I guess it runs as well as a good .15 engine and there is probably more room for improvement too.

airraptor

My Feedback: (66)

20,000 with a 7x4 isn't super strong but is good power for a stock engine. open the card up see what it will do with a 7x5 APC. open the carb on a LA15 and add another port in the sleeve and the case and can get 19,500 open exhaust with it.