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R/C Tech Forums Thread Wiki: Kyosho Inferno MP9 TKI4 1/8 Buggy Kit
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Picked up a TKI3 and want to upgrade to TKI4 ? Here are all the updated parts:

Shocks

IF347-155 1.5X5 Pistons
IF471-01 Front Shock Body
IF470-01 Rear Shock Body
IF470-03BK Shock Adjust Dial
IFW154 Boots
IF346-05C Shock End Set

Wing

IF491BK Wing
IFW460B Wing Mount/Stay

Rear End

IFH006W Wheel
IF490 HUB
IF490-01 Hub Insert
IF492 Shock Pin
IF423HB Rear Arm
IF287 Hard Upper Rod Rear

Front End

IF489 Steering Rod Set
IF488 Knuckles
IF487H Front Arm
IFW458 Hard Lower Pin
IFW425 93MM CVD
IF286 Hard Upper Rod
IF486 Lower Susp Holder
IFW459 Servo Saver (Hard)
IF446B Ackerman Arm
IF426-64.5 Susp Shaft


Other

IF469B Filter
97035LW-13 Clutch Bell
IF453B Body Mount
IFW107GM Hexes
W300910 Washer
IF443B Center Diff Plate
IF444C Tank
IF479B Radio Box
96772 13x16x0.15mm Shim
IF481B Fuel Tank Stay
IFW336GM Wheelnut
IFB008 TKI4 Body
IFD403W TKI4 Decal

---------------------------

Another option if you want TKI4 Durability but TKI3 geometry of the front arm is :

IF493 Front Arm (Updated MP9 front arms replaces IF427B as a direct fit. Left and right.)

They use the older TKI3 captured outer hinge pin and screw. But if you just reem out the the outer hole you can use TKI hinge-pin/nut (IFW458)
---------------------------

Optional Updates / New Parts:

IFW469 IFW469 Aeration Cap Set(Threaded Big Shock/MP9)


Optional Alu front hubs:
- IFW412 - 13 deg (like stock plastic ones)
- IFW436 - 16 deg
- IFW461 - 19deg

M2C 1mm engine spacer: M2C9610

Body Options

New Bitty Force Body

Tebo's Build Videos

Video #1

Video #2

Video #3

Video #4

Video #5

Video #6

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Original Kyosho MP9 TKI Thread

Setup Sheet and Tuning Original Post
The setup sheet is getting crowded with all options but don't worry once you get acquainted with the parts will make sense.
Run the car as is, more than probably you won't need anything else. Using my setup as an example:


Diff gear has two options, normal and LSD. LSD stands for limited slip differential and is like using thick oils because you can't tune coast from locked.

Shock setup is a bit more confusing, you have two shock body sizes (S and M and truggy sized rear shocks that only the first version had so forget this one), three types of pistons (flat holes and surfaces, flat holes tapered surface and tapered holes with tapered surface): tapered have most pack, then black(simple piston) and then white because length of the holes. Then you have different length springs to account for different shock sizes, for a standard wheelbase/no weights car a good combo is Light Blue front and Orange rear, if you extend the wheelbase then I expect the included Light Blue rear springs be money instead of Orange.

Ride height is self explanatory, start always with lower arms parallel because good suspension geometry will be far easier to achieve. Rebound is used as total shock length no idea why they call it rebound, either use total shock length or maximum exposed shock shaft length. Camber self explanatory, run more camber in the front than the rear to make the car oversteer and more rear than front to make it understeer(grossly oversimplified).

Toe same deal as camber(again grossly oversimplified) but this you have to run the least amount you can. I use around 2-2.5 on my cars, never more as I can find traction by other means with way less impact on performance.

Wheelbase is a powerful setting, changes a lot of stuff. Let's just say that it can make the car behave neutral or not in that small range. Try for yourself. I like to use the longest setting and tune from there.

Shock position self explanatory, something most don't change and I don't play around with it. I do have a method but involves much work (with the car bottomed out, see which position places the shock 90 to the lower arm and then chose spring from a couple equations and bam done, I can do it easily so anyone interested just ask.

Rear upper arm position is again an important setting, you change both camber gain and roll centre. The rear roll centre should be higher than the front, that's why I use the middle hole inner row as a starting setup.

Suspension arm, self explanatory: there are two different length arms and each has a hard and a normal flex plastic.

Front suspension bushing is for upper arm alignment, also same deal as rear upper arm position changes both camber gain and roll centre.

Suspension holder is for kick up (pro dive is the correct naming). I believe tki4 9 of kick up to be better than 9 of kick up using the tki3 parts because you can run the car lower (26mm front ride height) and use the +2mm front shock tower if there's too much camber gain or it's stiff in roll. So use +2mm lowered roll centre to keep most stuff unchanged or use the bushings with the dot up to lower the roll centre a bit more, doesn't hurt anything.

Front hub carrier, self explanatory. I am trying to use the out hole on top of the carrier as it is better during braking and accelerating. Together with the higher front roll centre on the tki4 should provide enough camber gain during cornering if not then more caster will do.

Rear roll centre and anti squat(wrongly called skid angle). Again same thinking as the front, lower the car and keep roll centre in the same height as before(that will need a change in upper arm position which my setup does). Anti squat is changed only if the pitching motion causes too much camber to be gained by the rear tires on power, nothing more.

Front knuckle, apparently there's a difference in the Ackerman arm. Can't say anything about them as I don't know enough about both.

Rear hub carrier,there is one made of plastic (which doesn't have offset apparently so it's suited to long arm setting) and three aluminium versions. One similar to the plastic one, other with offset and a new one with offset and adjustable hub height.

Rear tread can be used as arm length and outboard toe(never seen it being used but the possibility is there). Longer is better most of the time (only on really low traction).

Chassis brace, wheel hub, sway bars and weight are self explanatory. No need to use weights nor other hubs. A couple of roll bars would be a nice addition. About the aluminium braces I am torn, I guess the car doesn't need flex with this setup but won't recommend the stiffer braces but the lower engine mount is very nice to deal with flex around the clutch.

Wing and wing stay are like the d81x had regarding height and position. The wing should be as low and have free airflow as possible.

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Old 09-12-2017, 02:31 PM   #1966
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Originally Posted by rcmoe View Post
And what flaw might that be?
Lack of traction, why I don't know for sure. Of course i have a hunch
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Old 09-12-2017, 05:05 PM   #1967
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Lack of trackion when using allum braces? Yes it will lack trackion
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Old 09-12-2017, 05:06 PM   #1968
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When you said flaw, I thought you were referring to things breaking or bending do to the flex.
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Old 09-12-2017, 06:22 PM   #1969
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Quote:
Originally Posted by 30Tooth View Post
Lack of traction, why I don't know for sure. Of course i have a hunch
Interested in seeing what you find as well or come up with for a solution. The little that I know from being in the 1:1 racing suspension industry, the thing they always say is that, let the suspension do the work not the chassis. I mean you rarely hear anyone say my chassis is too stiff, because it's a good thing. Rally chassis for instance have more braces, stich welds than Steve Urkel and it's all or mostly in the suspension. Like most I ran the tki3 when i first started racing nitro due to everyone saying this chassis creates a ton of traction and glad they didn't change for the 4 because it freakin works like magic 😀. But it seems it's sort of backwards from 1:1 and I'm guessing its because the suspension on RC's is way behind what they can do in real cars and this all we have for now and to "tune flex chassis" lol.
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Old 09-12-2017, 09:10 PM   #1970
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Hello JLRC and Friends,

I was thinking about this Theory "Stiff Chassis let The Suspension do the work" since in my early age of racing R/C too, but come up to a point that realize that our R/C Shock is too basic/simple to do all the necessary suspension work. So, Chassis Flex is still necessary for the current technical know how on the R/C application.

Also, in my opinion, using an Aluminum Front and Rear Brace will move the stress point to the center of the chassis. And because of the current common 1/8th Buggy design with 2 big opening on the center of the chassis, Flywheel opening combine with the Spur Gear opening, right around the middle is the weakest point. If You notice a worn chassis will bent slightly diagonally crossing between the 2 openings on the middle of the chassis. Usually will be also in-line with the screw hole for the sideguards.

So, what I am trying to tell is that using Aluminum Brace will make the chassis bend faster despite the dynamic driving benefit.

Cheers..

Quote:
Originally Posted by JLRC View Post
Interested in seeing what you find as well or come up with for a solution. The little that I know from being in the 1:1 racing suspension industry, the thing they always say is that, let the suspension do the work not the chassis. I mean you rarely hear anyone say my chassis is too stiff, because it's a good thing. Rally chassis for instance have more braces, stich welds than Steve Urkel and it's all or mostly in the suspension. Like most I ran the tki3 when i first started racing nitro due to everyone saying this chassis creates a ton of traction and glad they didn't change for the 4 because it freakin works like magic 😀. But it seems it's sort of backwards from 1:1 and I'm guessing its because the suspension on RC's is way behind what they can do in real cars and this all we have for now and to "tune flex chassis" lol.
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Old 09-13-2017, 12:38 AM   #1971
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Quote:
Originally Posted by stanleyw808 View Post

Also, in my opinion, using an Aluminum Front and Rear Brace will move the stress point to the center of the chassis.
So, what I am trying to tell is that using Aluminum Brace will make the chassis bend faster despite the dynamic driving benefit.
I think it's the opposite. The max stress point is already in the center of the chassis (when the car cases a landing), so adding aluminum braces just decreases the magnitude of the max stress (and deflection) at the center of the chassis, resulting in less likelihood of bending because it takes more force before it reaches its max stress before bending. At least that's the simple explanation.

Here's a FEA screenshot I did with a stock chassis on another car, and later confirmed the above by adding an aluminum front brace.

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Old 09-13-2017, 07:23 AM   #1972
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Quote:
Originally Posted by rcmoe View Post
When you said flaw, I thought you were referring to things breaking or bending do to the flex.
Not a flaw like a design error but like a hack, maybe the car could work with less flex but Kanai-san choose more flex. That's my intent, to discover if the MP9 can be run with less chassis flex because bending centre axles is no fun.

Quote:
Originally Posted by stanleyw808 View Post
Hello JLRC and Friends,

I was thinking about this Theory "Stiff Chassis let The Suspension do the work" since in my early age of racing R/C too, but come up to a point that realize that our R/C Shock is too basic/simple to do all the necessary suspension work. So, Chassis Flex is still necessary for the current technical know how on the R/C application.

Also, in my opinion, using an Aluminum Front and Rear Brace will move the stress point to the center of the chassis. And because of the current common 1/8th Buggy design with 2 big opening on the center of the chassis, Flywheel opening combine with the Spur Gear opening, right around the middle is the weakest point. If You notice a worn chassis will bent slightly diagonally crossing between the 2 openings on the middle of the chassis. Usually will be also in-line with the screw hole for the sideguards.

So, what I am trying to tell is that using Aluminum Brace will make the chassis bend faster despite the dynamic driving benefit.

Cheers..
With plastic braces bending areas are spread away from the centre and the force is transferred slower than with aluminium braces. We will see, got some cards up my sleeve

Quote:
Originally Posted by 8ight-racer View Post
I think it's the opposite. The max stress point is already in the center of the chassis (when the car cases a landing), so adding aluminum braces just decreases the magnitude of the max stress (and deflection) at the center of the chassis, resulting in less likelihood of bending because it takes more force before it reaches its max stress before bending. At least that's the simple explanation.

Here's a FEA screenshot I did with a stock chassis on another car, and later confirmed the above by adding an aluminum front brace.
*snip*
Hope that aluminium brace is released, only thing that I have worries on that car. Good job!
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Old 09-13-2017, 12:42 PM   #1973
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I've been driving this car almost 5 yrs now and I've bent maybe 2 rear center unis. One for sure I remember because it was bent so bad. Now I've bent quite a few rear chasis braces. Ive tried adding a carbon stiffener to the brace that I made but didn't like how the car drove. I've since removed it. I still bend them periodically but I just deal with it
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Old 09-13-2017, 03:57 PM   #1974
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Exactly, it's not a deal breaker but a small nuisance.
Who's want/can try orange rear springs with the aluminium brace? @rcmoe, can you try your brace with carbon stiffener and orange springs?

Also going old school with longer rear arm, that's something I want to try.
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Old 09-13-2017, 05:04 PM   #1975
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I run rear orange springs often on loose tracks. Ran it with the stiffener. The car wasn't bad but was still better without the stiffener
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Old 09-13-2017, 05:09 PM   #1976
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There's a noticeable bow in my rear brace now. Guess I need to get this replaced but the buggy is still dialed. Complete teardown after the JBRL this past weekend.
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Kyosho Inferno MP9 TKI4 1/8 Buggy Kit-tki4-brace.jpg  
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Old 09-13-2017, 06:23 PM   #1977
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have tried aluminium rear brace with orange springs and it is still far from ideal, the car just suffers too much on bumpy and whoop sections, its actually good when landing large jumps but the negatives outweigh the few positives.

a good compromise is to run the extended one peice engine mount made by kyosho, you can feel that it has tightened the core of the car without upsetting its rough track handling or grip generation too much. it doesn't drastically reduce the chance of bending a rear brace though, but like rcmoe it is something i live with and happily replace them on a regular basis.

i will say though that it is important to replace them when they show any sign of being compromised, if you continue to run them you risk bending the centre shafts and the chassis itself, you can tell when your chassis is tweaked as your car will not fly straight when going over a large jump (it will want to twist mid air after leaving the lip), i was having that issue at a national race and tried so many things, eventually i noticed a subtle tweak in the chassis and switched it out, immediately the car went back to flying arrow straight.
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Old 09-14-2017, 10:30 AM   #1978
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Thank you all for contributing to this aluminium brace setup query. The matter was that drivers asked me how to make it work on those tracks that one mistimed jump can cause enough damage to DNF.

The engine mount is an interesting one, I think a plate screwed to the chassis lengthwise down the centre could be enough to stiffen longitudinally but allow enough movement side to side.
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Old 09-14-2017, 11:12 AM   #1979
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Reading back on some older post yesterday and found out I have been running the wrong or undesired front 78mm LT Blue springs when I went to the MS setup. Didn't really look at the spring rates at the time and thought it was the same as the 70mm LT Blue ones. So I guess I was running the same spring rates front and rear(It blue) this whole time lol. Just curious why they recommend it and what was the thought process behind it? Just put the 70mm LT Blue's back on last night Thanks guys!
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Old 09-14-2017, 11:52 AM   #1980
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The chassis flex is an interesting topic. Makes me think of motocross when Honda went to an AL frame on the 97 CR250 and that thing was the worst the frame was so stiff compared to the steel frame - harsh! You saw all the manufacturers add more and more flex and "tuned flex" to their frames over the years, which aids in traction. It's not always about the suspension not doing its job but under power the chassis loads up and a properly tuned chassis can put the power down better, along with handling bumpy tracks.
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