First Run Tonight!

zouz10

Well-Known Member
Messages
1,493
Location
Florida
Well guys, I took my first official run tonight. Here is a run through.

Once the gas was in, the motor started right away (Zenoah 29cc) since I salvaged it from a previous car.
I started to run the beast. First impression, WOW that thing is nice going up and down the road. I did only asphalt and hard sand driving today, and it ran like a champ!

So the car handles as if it was on rails. The brakes are just plain amazing! I got a JR 9000 in there and had to place my servo travel well below 40% as the brakes require almost no torque whatsoever. The steering is very precise as well. However, I need to play with the servo travel since the turning radius is a little too wide!

Like Monotheist, I got a Samba pipe as well, and the noise is right on tune to his description. Since I got the stinger coming out of the bottom (that is the only place it can come out of) every time I went on grass, I felt like it would catch on fire.. LOL..
The pipe started to melt part of the shell, so I will have to fix that ASAP.

I was not too impressed with the top end speed. However, seeing how it was my first run (not with this engine) I figured the car needed to break itself in. At the end, the car started to bog, and when I lifted the shell, I found the header bolts for the exhaust were completely off and the header was just dangling there (no wonder there was no power in the end LOL)

I need advice on gearing though. Right now, I got the stock gears, and I was wondering what the best setup for speed was? If someone could please just let me know what combo to put in there, I would appreciate it. BTW: I suck at gear ratios!!! LOL
 

monotheist

Well-Known Member
Messages
174
Location
Melbourne, Australia
Yeah I forgot to mention one of my header bolts came a little loose as well...lol

The pipe should not be touching the shell (well at least mine doesn't) I have between 5-10mm clearence on all sides so if yours is touching maybe readjust the front flex joint so it sits lower. The stinger is protuding about 5-8mm through the hole in the side guard in mine if that helps any.

For higher speed try a 33/30gear combo but you will probably have to buy these gears seperately as they don't come with the kit. The Evos also don't come with the standard plastic 25T/24T (C & D gears) but are running 26T/23T steel ones instead so that will give slightly higher speed as well.

I am running a 27T/36T pinion/idler combo currently as I don't require top end for the track as its far to small to ever top out the engine. This makes for rather boring flat oval running as the top speed is not that great. Your engine should have more torque than my 26 so a 33/30 or even a 36/27 should give you the speed you seek.

Edit:
Just came back from another run trying out different ratios.

With the stock diameter wheels I am getting the following ratios (measured by counting the pinion rotations to one complete wheel rotation)

27/36/23/26 = 12:1
24/39/26/23 = 10:1
27/36/26/23 = 8:1

I ran the 12:1 ratio yesterday and while acceleration was ok top speed wasn't that exciting. By switching the 23/26 to 26/23 (8:1) I went out for another run today Top speed was now great but acceleration was rather poor. It was bogging off the line but once it wound out a little and hit the power band it was awesome. I have since switched to a 10:1 ratio and will try that in the next few days. This I believe will be the sweet spot between off the line torque and top speed. As I said earlier your 29 should have more grunt to cope with the higher ratios than mine so I would be interested in you trying the 27/36/26/23 combo to see what you think.
 
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zouz10

Well-Known Member
Messages
1,493
Location
Florida
Thanks Mono,
I will give it a try today or tomorrow depending on if the weather behaves!! I think that 10:1 ratio sounds like the ticket from your explanation. Currently, the car moves ok, but it feels like something is holding it back. I will also try to check my acceleration linkages and make sure they are moving all the way.
The header bolt came loose on yours too? Did you forget to put threadlock on yours or it just so happened?

The pipe touches just at one spot, where the diameter is biggest. You're right, I will have to push it down a little for some clearance.
 

zouz10

Well-Known Member
Messages
1,493
Location
Florida
Mono,
I did some calculations and it appears that applications from the MCD user guide on page 5 number 3,4,5 gear combo should be right around the ballpark of a 10:1 or 8:1 ratio. From stock it was way up there, it seemed 16:1 or more. I will start tonight with #3 which is 27/36/24/25 giving 1.38 and work my way down from there.
Thanks for your explanation it made a lot of sense!!
 

zouz10

Well-Known Member
Messages
1,493
Location
Florida
PM sent to Chicken lips.

I am currently on my second run and it is amazing the power and speed difference than it was the other day. As it turns out, I could only get it going as far as the 4th setup on the MCD sheet (I don't have all the gears) 27/36/25/24 and it rocks. I will buy some gears and do the 30/33/24/25 setup and that will be the max. That will be close to Mono's 8:1 setup and I think it will rock!!

The pipe stayed in this time and I put the stinger lower and there were no burns on the body this time!! Thank God

The car does tend to bog a little sometimes. I saw it was running low on gas and there was air in the fuel line, could this be causing it? Also, I have no vent hole in my gas tank, maybe this could be a factor! Is it better to place a vent on the rubber plug between the 2 fuel line (how big) or is it better on the gas cap?
 

monotheist

Well-Known Member
Messages
174
Location
Melbourne, Australia
Awesome man, that’s great. The 27/36/25/24 combo is good too but perhaps still a little low for your 29cc grunter. I thought the new Evo's had the metal 26/23 gears? Oh well. There a nice upgrade btw but are as notchy as hell when you first put them on so they require a fair amount of break in before they mesh 100%

With no vent line installed your tank is creating a vacuum as the fuel level drops which will ultimately cause fuel starvation so stick a breather line in the rubber grommet or fuel cap (doesn’t matter which) but make sure with either method the line doesn't protrude more than approx 1/2 inch into the tank otherwise it will become blocked with fuel on a full tank and cause a vapour lock defeating the purpose of it.

As far as bogging it could be a number of things such as being slightly lean on the L or H needles. There is a really interesting thread on RCU at the moment where a guy is trying to find out why he squeaked his new engine on this MCD. A few have said the MCD's put a much higher load on the engine than other large scales due to the additional drag of the 4WD system and higher weight which causes the engines to run hotter. On top of that most body shells do not allow sufficient air to assist with engine cooling which is something I noticed last time out. I have since cut a nice big hole in the windscreen to allow better airflow.

Air in the fuel line is something I have been struggling with for a while. It is mainly caused from air being sucked in from the fuel pickup which can flop around inside the tank. so make sure the weighted metal pickup is suspended just above the bottom of the tank and not folded over in an “L” shape as this allows it to roll around and suck in air when the car is tilted. Pockets of air in the line will cause a momentary lean condition which can also cause bogging.
 

zouz10

Well-Known Member
Messages
1,493
Location
Florida
Mono you are the man!! Thanks for the quick reply..
I believe that the bogging is due to the engine not having the vent. The first time I took it out it was running fine, but today the gas was very low and this is when it started occurring so I put 2 and 2 together!! I was surprised to find that my fuel tank did not include metal pickup lines but instead had plain tygon tubing.. WEIRD!! On top of that they don't sell those at largescalerc.com..
On the HPI baja gas tank, I believe the vent line is in the gas cap itself (a pin hole), would this work on the MCD?

BTW: I just placed an order for some more gears, I got a 30 and 33 teeth set! Can't wait to try those bad boys out.

I can see what is meant by the engines running hotter because of the 4WD and the weight. That thing is heavy, and I got to carry it up 4 fights of stairs LOL!! after that I need a beer or 2 for the strain relief!! LOL
 

whizzy

Well-Known Member
Messages
283
Location
paisley
u need to add clunks to your fuel line in your tank on the mcd so that u get every last bit of fuel and so your lines stay in the fuel too
 

zouz10

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Messages
1,493
Location
Florida
Whizzy, what are clunks? If someone tells me how to make them, I will definitely do it. At one point when I was running it, the engine would still be idling, but as soon as I would accelerate it would bog way down. After 2 seconds if was ok and would work again. Definitely fuel starved!!
 

zouz10

Well-Known Member
Messages
1,493
Location
Florida
I just placed my order for 2 clunks... I love the name..LOL
Do I need to put one on each line or just the line that sits at the bottom of the tank? Thanks for the info...
 

lauterbacher

Member
Messages
14
Location
Everett, Wa
It seems like you guys could solve all your boggy at least from gearing if you ran an adjustable clutch, so the motor is always taking off on the engines power band. I know it's a given in the racing circles.
 

zouz10

Well-Known Member
Messages
1,493
Location
Florida
Lauterbacher, I got an elcon clutch in mine, and I got the screws set at 1.5 turns. What would you recommend for the settings? Is 1.5 too much or too little?
 

lauterbacher

Member
Messages
14
Location
Everett, Wa
You need to adjust your clutch for RPM that the motor's turned. If you're good enough, you do that by ear, if not you have a tach. But a good starting place is usually about 8,000 RPM, because the way I read your posts, you guys are just depending on just brute bottom end horsepower to the way you're gearing, and that's not correct. You want an adjustable clutch so you can have your gearing on top and your RPM set on your clutch on the bottom to kick in where your horsepower is coming on or else it's always going to bog unless it's geared so low it's ridiculous. You can buy a little on board tachometer from Sendec for about $65. Just use Google to find them.
 

whizzy

Well-Known Member
Messages
283
Location
paisley
well i run a pitstop racing adjustable clutch and mine is set at 9000 rpm and i don't have any problems with bogging down the only problem i had was not enough fuel getting to carb between high throttle to low throttle and the 813 carb fixed that problem
 

monotheist

Well-Known Member
Messages
174
Location
Melbourne, Australia
Thanks for you feedback lauterbacher. Makes sense having the clutch kick in just as power begins to build. In all honesty I have no idea what revs my Elcon is set to. All I know it does take a fair amount of revs to begin to engage. I ordered a tach for my sensor radio which I will attempt to mount onto the flywheel to see what revs my engine is doing and at what point the clutch is engaging. Should provide some useful information.

EDIT: Just been looking at the Sendec products. Appears they are only capable of reading up to 16,000 rpm.
 
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