rodneybarrett

iTrader: (50)

I have a TOP TSR12S3 engine just recently broken-in and I can't seem to get the tune just right.


I have properly set the HSN and LSN accordiing suggsted tuning techniques.

Here are the symptoms:

I bring engine up to temperature (approx. 200 degrees), then if I let it sit for more than about 10 seconds and take off full throttle, The car takes off fine with a nice trailer of blue smoke, and gets about mid way in its rpm range and just dies. When I say mid way, I am talking about the car running for about two seconds and getting at least 40 feet away from me before it dies.


I bring it back and it starts right up, no problems at all.


Once I get past that initial take off, things seem to be fine.
Meaning, I can sit for 10 seconds and take off without any problems.


I have tried several needle positions (mostly all on the rich side of things) and nothing seems to correct it.

The only thing that I can think that is somewhat common is that I think it always happens when I have a full tank of gas.


Any suggestions?

AMGRacer

Sounds to me like an overly rich bottom and a lean top end.

A few things you can do to test. Pinch the fuel line at idle, it should die in 3 seconds or so, more means too rich. Make sure the gap at idle on the slide is only around .5mm. If it is wide then your bottom is too rich.

rodneybarrett

iTrader: (50)

Actually, it's not.

If you're familiar with the needle settings of a nova carb then here they are.


HSN - just a tad richer than 4.5 out (factory settings are 4.5).
LSN - 2.75 out (factory settings are either 2.5 or 3.5, I hear one thing from one person and something else from another. The engine won't even start and idle at 3.5 turns out)

The idle is approx .5mm open. it is a nice low, smooth idle.

And again, once I get past that initial launch, this doesn't seem to happen anymore (from my recollection).





And if it were a lean condition on top end, wouldn't I see some signs. For instance, when I take off, blue smoke all the way up til it dies. I wouldn't think I would have that much smoke if it were rich. Always, it seems there would be some hesitation as well. Just my thoughts.


I am starting to lean more toward an issue with the tank and pressure line system b/c it seems to always happen right after the tank has been filled.


any other suggestions or attempt at diagnosing the issue?

AMGRacer

You cant rely on those numbers to set the needles, several of my engines have run well far away from those settings you mentioned.

The too rich low end disguises the lean top end. At idle the motor loads up and provides excess fuel which is why you are seeing blue smoke. I have had the exact issue I am describing and it never looked lean.

Do the pinch test I provided above first. If this is OK, then richen up the top end so when you pull WOT it does not pull maximum RPM then start leaning it again while checking performance on the track. Run it for a while and check the temps. If this is all OK then you likely have some form of mechanical issue.

If your fuel system has a problem it generally makes the car run lean and your temps should keep getting higher.

teammpp

I totally agree with AMGRacer. Everything you described points to a too rich bottom end and too lean top end. Lots of blue smoke shows on acceleration tauts that the engine is running rich bottom end. Try taking the HSN out to 5.25 turns and the low needle in to 2.25 turns (which mine are set at). It may still require minor adjustments at these settings as each carb will work differently because of several variables.

rodneybarrett

iTrader: (50)

ok. still having problems with the engine. I have tried the different needle settings but they made the bottom end way too lean.


Here is something interesting.

My TOP TSR12S3 is the latest modified version (like the ones in the magazine) but the crank opening (the one that the carb exits to) does not have RTV or anything in it. The opening actually goes another 3mm further back (toward the clutch). I thought these engines were suppose to have filled crank. Wouldn't this cause some fuel flow issues is that volume is too big.


Can someone else take a look at their engine to confirm this.


This may be one of the causes on my problems.

kevink2

That's normal, it lightens the crank.

Lean it out! What king of fuel are you using? Any shims added? What plug?

rodneybarrett

iTrader: (50)

I know it lightens the crank but if the crank was designed to be filled (according to the pictures), and is not, doesn't that mess up the fuel volume?

30% Maxy Fuel
Have tried both a Novarossi 6 cold and hot
A copper shim added.


If I lean it out at all, I start getting temps of close to 300 degrees and the engine starts sounding like it's starving for fuel.


I run other engines without problems (Rossi R12, Mugen MT12, etc.) But this is my first higly modified engine.

teammpp

How long are the fuel tubes for the carb and exhaust??? If its only happening with a completely full tank then its possible you are getting to much pressure feed from the exhaust to the tank.

rodneybarrett

iTrader: (50)

The current sizes are as follows:

Pressure line: 12 inches
Fuel line: 5 inches

My other engine (Rossi 3 port) seems to work fine with the same setup

teammpp

Try shortening the pressure line to 8 inches.

AMGRacer

The crank is normal and wont cause you problems. How did you determine that the bottom end was too lean?

Have you tried what I have suggested above:

If you do this you cannot get the tune wrong it is impossible. Running 30% fuel makes tuning more delicate. Start from rich and follow the procedure I outlined. I am no nitro genius and I get my motors tuned perfectly. This is also the proceedure that Josh Cyrul recommends. Forget about the temps for the moment, get the motor running so it sounds and reacts correctly. Then let the motor cool down and run it. If it is getting too hot at that point you need to:

1. Check the clutch is set right.
2. Ensure your fuel is good quality (I dont know that fuel you are using)
3. Add head shims.
4. Check for air leaks.

rodneybarrett

iTrader: (50)

AMG,

I do appreciate the help.

However, I have tuned several other engines (MT12's , Rossi's, etc.) without problem so I have a pretty good idea of what is going on.

Matter of fact, a buddy or mine and I tried for 2 hours one day to get this engine to act right. Without any luck.


Too lean: When I used the suggested needle settings recommeded on this post (HSN: 5.25 and LSN 2.25) here is when it was too lean. I determined it was lean a few different ways. First, the pinch test. When I pinched the fuel line, the engine stopped immediately. Secondly, you could hear the engine revving and then slowing down, revving and slowing down at idle. Thirdly, if I shut it down and tried to start back up, it is a bear and you can hear it starving for fuel. To me, that is a sure sign of a too lean LSN.


The reason I am even posting here is because I have tried all the usual techniques and nothing seems to work. If I get it running to where it will stay running, The temps go off the chart (yes, over 300 degrees). If I riched the needle settings up then it start the flame problems and also runs like crap.

I have been very patient in moving the high and low needles (one hour at a time, which BTW, is very tediuous to do) and have still no had any luck.


this why I thinking it may something more than a tuning issue.



now, you say the crank is ok, but according to the way it is suppose to be (filled crank), there is a much larger volume in that chamber than the design calls for. This could mean more fuel, more air, or a combination of both. This is why I was asking that question.



Sorry to ramble but I cannot for the life of me figure out how to correct my problems.

rodneybarrett

iTrader: (50)

Also, I am pretty sure it is not mechanics on the car b/c I can throw another engine in and everything works fine.

Johnnytc3

iTrader: (1)

I think you have a carb problem. Tuning an engine with a bad carb is like ... well you know. Take your MT12 carb and swap it over and retune, i think it will solve your problems.