K90 KINGCRAFT in JAPAN

[Anders]

Ian and Hammer , i got them from the Swedish dealer.

They use it mainly for the 20 and 30 min heat in FSR-V here in europa.

I think Al can order them if he want`s.

The problem might be that they don`t do them anymore.

The last time i got a engine with that carb is now almost 2 years ago.

But they work good.

Why i don`t use it for riggers,easy.... the only time i mill is before start and after the finish line in between it`s wide open ;D

BUT there is some other things that you need in a rigger and that is ALOT of fuel when you throtle down alittle.

That is controled by the pipe but it`s to looong story to explain........ that`s why i don`t like them in riggers........

I never use the lower ring on the engine.(problems)

So far the best pipe when it comes to power is MUCK 15cc pipe.( Pb 95mph with a K90 and 1667 with 6,4"cup )

That pipe generates some problems so therefore my reccomendation is Mac 13cc pipe reworked.

To noicy in STD muffled shape.

Mac 15cc pipe is good,it gives you a wider torque band but my feeling is that you loose some power.

We have to use muffled only.

Anders

 

[Ian Inverarity]

Anders,

Thanks for the info! 8)

What is re-worked on the Macs 13cc pipe, just the muffled section? Also the header section on the pipe is too small for the K-90 exhaust header?

What problems did you encounter with the Muck 15cc pipe?

I also do not use the lower cooling ring. I have increased the cooling on the head button a bit tho.

Ian.

 

[Twin_k90]

Anders,

we use all the cooling rings, always have,

what are your reasons for doing this??

to try to stop them nipping up?? we found running more oil stopped this problems.

Dale

 

[Anders]

Ian , reworked means that i have extended the muffled section and mad my own "back plate" so you can`t see throu the pipe.

Otherwize STD.

I have another tip here to solve the manifolder problem.

Order a MAC 67/84 manifolder and silicone pice (with spring) put that on the K90 "fitts like a glove" and then take a 20mm (20,2mm is perfect but you have to special order them) reamer (i think it`s called in english) and make the hole alittle bigger in the pipe and WAM!!!!! you have a super combo that will fitt on top of each other.

I use Rossi 45 silicone fitting on that also and it works SUPER!!

Dale , why i don`t use the lower ring is that after 5 or more piston that have been pulled apart i half ( per year ) i tested to not use the lower ring and the problem whent away (almost).

Now i kill a engine every 2 years and that is good for me.

I think that the STD head gives you enough cooling,i have not changed my at all..........

I try to cool my engines with fuel instead.

ALWAYS 20% castor oil in my fuel. BUT only 40% nitro :-[

http://medlem.spray.se/smbf/fotoalbum/Pole...sm_dscf0092.jpg

Tryed to post a link :-

Anders

 

[Anders]

I think this is better ;D

http://medlem.spray.se/smbf/fotoalbum/Pole...AM/dscf0092.jpg

Anders

 

[Hammerhead]

I tried the Macs 13cc straight tuned pipe with the the K90. It was the same size as the K90 header, but it wouldn't slide over it. It was at 28 inches. It was a dog compared to the titanium pipe I use at the same length. Didn't test it at other lengths though.

Hammer

 

[Twin_k90]

Anders,

Thats interesting about the pistons sticking, i have stuck one and a mate has stuck 2, the problem went away after i went to 17% klotz oil and 5% caster oil,

Are you running water through the header and the lower case to pre heat it??

Thanks for getting on here and giving us some ideas!!

Dale

 

[Ian Inverarity]

Anders,

Interesting info, thanks! 8)

I have talked to a guy here who runs MAC 84's, he made a larger diameter header for them and actually gained performance. Thus I would be reluctant to reduce the header size on my motor!

What pipe length would you recommend for the Macs 13cc pipe? (and where do you measure it?). I presume you are using the liner shim?

I use fuel with 7% castor, 13% Klotz Techniplate and 25% nitro. I have made my own head button to suit this nitro level. You must have messy boats and pipes with 20% castor!

I run the water through the header and under the exhaust port before the head, but run no restriction on the outlet. The engine runs quite warm. I have not had the engine long, but have had no trouble with the piston.

Hammer,

When you say 28cm, where did you measure that to?

Ian.

 

[Hammerhead]

Hey Ian! I use the standard method. From the center of the plug to the widest point of the pipe.

If the pipe has a chamber like the titanium one does, then to the first edge of the chamber.

Hammer

 

[Ian Inverarity]

Hammer,

That may have been a bit too short. If you can still try it, I would suggest 30cm instead! That would be my guess based on the Macs 15cc pipe.

I measure along the pipe to the middle of the case. This is a little bit trickier to do, but it means that the angle of the header is not a factor, as it is if you measure from the plug. Measuring pipes is a lot trickier than many people imagine, and is only really a valid measurement if for the same pipes and exhaust timings, and measurement methods! :

Ian.

 

[TimD]

Mac's 15cc pipe on a 90 I usually start at 300mm from centre of plug to the weld in the middle of the pipe and shorten from there.

The way to measure different pipes against each other is to use the point halfway down the rear cone. That accounts for different cone angles. The exhaust timing changes the effective length also.

 

[Ian Inverarity]

Tim,

A Macs 15cc pipe has a straight centre section, so which weld in the middle do you mean? From memory the 13cc pipe does not have the centre section.

The problem with measuring to the middle of the converging cone is you cant even see it on muffled pipes! And what do you do with pipes with multi-stage converging cones like the Bolly, parabolic MAC pipes, and the CMB 67/80 (fat) pipes? Hehe!

Dave Marles (English Multi racer, who designs, makes and sells pipes) says the only valid method of measurement that allows comparison of engines with the same timing but with different pipes is the distance from the face of the piston at the exhasut port to the start of the stinger. He swears by this system. (Same problem with muffled pipes too!) I have never tried it, but I know that comparing lengths to the start of the converging cone, or the middle of the converging cone, is not a truely accurate measurement. But measuring halfway down is most certainly a better measurement!

Of course if you are simply comparing engines with the same exhaust timing and pipes, it doesnt matter where you measure, as long as both are measured in the same place! ;D

Ian.

 

[Twin_k90]

we know all about measuring in the wrong spots dont we Ian!!!

 

[Ian Inverarity]

Yep! :

Wow, that was a stuff up! Thanks for reminding me! ;D

Ian.

 

[Hammerhead]

I was going by the book "Advanced RC boat Technics" by Finch. I thought that my method was the standard way. I always ran my O.S 90s somewhere between 27.5 and 28. It l'm running my Kingcraft at 28 now. I would appreciate it if you could draw something up on your Microsoft paint that explains your middle of the case method, and post it.

Hammer

 

[Anders]

Dale , i have tested to preheat the cooling wather before the engine and i don`t like that.

I got "steam locks" in the engine and no wather went trough.

So what i do is to take the wather from the rudder to the engine and from the left front sponson to the manifolder when i run K manifolder or nothing more if i use the MAC 67/84 manifolder.

AND i don`t restrict the wather outlet on my engines or manifolders.

I can let you all know another thing ;D

On my boat after a race i have NO greasy oil at all!!

Just some thin film of oil as small dots,but that is almost dry.

The thing is that when you find the right setup there will not be any oil on your boat and in the pipe.

Ian , I use the mac 13cc pipe with a pipe length of 295mm with 188 deg of exhaust and 9,1:1 in comp in EAP.

In some of my K90 engines i have a ring and in some i don`t so it`s a mix.

AND i always messure in the middle of the engine to the widest part of the pipe.

On the pic i made the link to i have a old PICCO pipe mounted and that is the best alround pipe to have but the problem is that you can`t get it anymore .

Anders

 

[Twin_k90]

Anders,

Thanks for all the great info, it is awesome when people all using the same products put there heads together,

i will try not using the lower cooling ring after the nationals,

i am using exhaust throttles so the boat gets pretty messy, when i was using the standard headers there was no mess in the boats at all,

we have nationals next week, my boat is flying at the moment.

here is a pic, it is a bit old and dosent have the exhaust throttles etc on it, ill get some updated pics next week.

Also where do you purchase your K90's from??

Hammer,

got the cheque yesterday, all is just about ready, just waiting on the trim plates and engine mount rubbers and a radio box,

Dale

 

[Ian Inverarity]

Anders,

Good stuff! 8)

If I can find a Macs 13cc pipe at a good price I will try one! 295mm is pretty close to what I am running with the 15cc pipe, but mine is also in a mono. A heavy mono!

I am not sure off the top of my head what the exhaust timing is, but I think mine is 189. The compression ratio is 17:1, that is the conventional ratio of combustion chamber volume plus swept volume to combustion chamber volume. I dont know what it is as a trapped compression ratio.

I pre-heat the water thru the header first, then under the exhaust port then head, but do not restrict the lines. I am using the line underneath the exhaust port, as I have done with my A-90's and A100's, but I dont think this would really do much.

Because of the carb orientation my transmitter gets oily when I start the boat!

Hammer,

Looking at the lower picture of Dales twin, I measure to a point just above the middle of the "K" on the case. 8)

Ian.

 

[TimD]

Dale,

You need to post some new pic's - it look's a bit different now compared to back then (goes much better too!)

Tim.

 

[Twin_k90]

Tim

i know but i havent got any new pics of it!! ill have to get some!