PLEASE help, IMPOSIBLE TO TUNE MR-12 ENGINE
 

Hi, I have a Mugen Mtx-3 and Mugen Mr-12/Rex pipe combo.

The engine was heat cycled and broken in by the previous owner.

Other then that, its pretty new, a few tanks through it.



Anyways, I am having so much trouble tunning it.

I fire it up, run it for a few min, its running great.

All of a suden it starts bogging down, I bring it over and it shuts off.

Smoke is coming out of the engine, I take the temp and its at 300-340!!

This is the second time this has happened.

So, I turn the HSN one full turn counter
clock wise, I run it, now i'm getting 280-290, still to hot.

I turn it one full turn back again.

Now its running cool but it wont shift into second gear because its so rich!!

It takes so long to shift and its so slow.


So I have confirmed, the engine needs to be at 280-290 for it to shift.

It runs at its peek in the 300's but will smoke and bog eventually.

It runs like shit at 220-230.


These are all full load temps, after running it for a few min.

I dont get it.

Fuel- Odonnel 30%, brand new.

THANKs

If you're using 30% nitro, best is to use colder plug and add more shim to lower the compression.

Im using a VERY cold RB standard plug.


I dont know what im doing wrong!!!

I have the MR12 and use 30% it come ready for 30% it might be loading up on the bottom end (to rich) get the bottom end (do pinch test) then go to the high end it could also be the clutch draging a little

I leaned out the LSN.

When I do the pinch test, how long should it stay on and where should I pinch.



ALSO, this thing is very hard to keep idle.

It turns off while idle almost every time.

Yeah, like I said above, I cant really do the pinch test because the car doesnt stay idle unless I apply throttle constantly.


The only way to keep the car idle is if I bring my trim down.

I keep my trim at 80 (max), bring it all the way to 60 makes it idle for a little.

Try adjusting your 2 speed to get it to shift at a lower temp

Set your HSN at 5 Turns out, LSN at 2.5 Turns out. Idle you want about a .8 to 1mm gap when throttle closed. This should get you on the rich side, but you wont hurt the engine. Tune the HSN first going no more than at eighth of a turn at a time. Temps should be in the 200 to 250 range. Dont get hung up on temps, as long as isnt more than 280 you should be fine. Tune for performance & reliability. You are correct that it is to hot when it bogs down after a few mins. If you are still having problems after tuning this way, you need to check for an air leak.

I screw in the HSN all the way, then screw it out 5 turns?

Same for the resT?

Are these stock settings?


ANYWAYS, the engine runs so bad at anything richer than what I am at now.


how do I look for air leaks?

My exuast gasket is a little ripped, thats about all I know.

somone said the fuel line may have a air leak.

I think this may be the problem.

Theres air bubbles in the fuel line all the time.

I think thats the problem,

Do you guys think changing the fuel line will fix my problems?

poorly running engine at idle to me means a worn piston and sleeve.

remove the glow plug and turn the flywheel over with your finger while the engine is still on the car. does it turn over easily? any resistance at TDC? if it turns over easy, I would guess the previous owner did not maintain the engine properly or while you ran it at 320F you lost the seal on the engine- piston and sleeve= gone.

most of these engines will run 280 no problem. with temps of 300+ you have usually cooked it.

That doesnt sound right, with the glow plug in, the engines flywheel has resistance meaning theres compresion.

Without the glowplug, its easy to spin the flywheel.

sorry to bud in...:D but i am totally confused with this manual testing for compression...:confused:

do we turn the fly wheel with or without the glow plug....???:confused: thank u...



p/s...fsturbo...your engine should be able to idle...if there is no leak..check your conrod..and piston sleeve and inner or oouter bearing...good luck..for your info i've encountered more than once this sort of problem...and it ends up ( for me that is) the conrod is the problem....:D

I never mentioned compression (which would be checked with the plug installed). I was talking of checking the "pinch" at TDC. The pinch at TDC is an easy indicator of the engine's compression- this is very easy to check without the added expense of a compression gauge. Usually if you have some "pinch" left at TDC, you have adequate compression (life left) in your engine.

If you want to check the compression of your engine, you can buy a $30 gauge from dynamite or try this:

remove the engine from the car and get the piston on it's upward stroke towards TDC. support the engine by holding only the flywheel and see how fast the engine rotates around the flywheel. If it falls right through TDC while holding the flywheel the seal (compression) is gone. if it slowly rotates through TDC your still OK. Obviously a new engine will not roatate past TDC with htis method.

sometimes it helps to put a little MMO in the exhaust port and rotate the engine. watch for bubbles to form as the piston travels up. you'll get some bubbles as the piston crosses the exhaust port, but if you see bubbling all the way to TDC you are losing compression in the sleeve fit.

As said above- also if the rod bearing is gone you will not be getting the full stroke of the crank, and hence compression will be very low (like adding shims).

Lets assume your engine (shim, plugs, compression....etc) are still good........now, leaving you the LSN, Idle and HSN to check...

(1) Your carb idling gap might not be right, cause you need to apply throttle to keep running....that can be caused by your LSN setting or item #2.
(2) Air leak on the carb....?
(3) Your LSN is not set correctly, yes, do the pinch test.
(4) your 2 speed was setup way too tight.
(5) your centax clutch was setup way too tight
(6) With 30% fuel, yes, 290 are too hot to see on engine.
(7) your HSN did functioning well, cause the temp does went down when you richen it.

I can only think of 4 things about high temperture of engine.

(1) not enought ventilation (very rare)
(2) engine under a lot of load (wrongly adjusting the centax)
(3) not enough fuel (less oil, not enough lubrication)
(4) engine on high rpm for a very long time (stayed on the 1st gear without going to the 2nd on a 200 foot straight...)