webdr

I have a monster gt 4.6. I have just completed the engine break in and am "tuning for performance" now. Im following the directions in the manual. Ive got it almost dialed in but when I open the throttle from a dead stop, it accelerated great for about 5 to 10 feet then bogs and will die unless I let off the throttle. Its not an instant stop, more like a bog that gets worse (1 to 2 seconds from bog to engine cut off) until it shuts off UNLESS i reduce the throttle. The stock setting is 2 3/4 turns for the high speed and 6 1/2 turns for the low speed. It seems af if I have adjusted each needle almost 1 to 2 full turns in each direction with no change in the bog. Is this a high speed needle or low speed needle problem? It seems like the engine tacks up before it bogs but Im nowhere near 2nd gear. UGH!
Also, Ill note that the engine is running between 190 and 220, there is some white smoke but I dont know if its more than average or less considering this is my 1st nitro vehicle.

Dale Gribble

My Feedback: (4)

Sounds like you are doing good! That was a good bit of progress for your first go at it. Many new nitro hobbyists have a few more hangups before even getting through the process.

Your description sounds 99.9% like it's too lean on the HSN. If the engine takes off great and then bogs it is too lean on the HSN. Basically, it starts starving for fuel and cuts out. You definitely don't want to get crazy with the needles; 1-2 turns is HUGE for a nitro engine. Most fine tuning is gonna be in 1/16-1/8 turns. You probably overshot the sweet spot.

No problem at all. Set both needles to factory settings. As a rule of thumb, you always want to tune the HSN first. So, start the truck and get it warmed up. You do not want to attempt a tune when the engine isn't warmed up fully. When it's warm, start making WOT straight line passes. Once you make a few passes, bring it in and turn the HSN in 1/8 turn (turns in /clockwise = lean, turns out / counter clockwise = rich). This is the HSN, so don't focus on faster take offs, focus on higher top speed. The truck should be a hair faster now. Make a few more passes, and repeat the process until the truck is winding up good and shifting into second gear; once you get close to the sweet spot, don't tune in more then 1/16 turn increments. Don't tune by temperature as your first guide. Once you get the truck shifting and clearing out the pipe good, you will probably find your temps around 230-250 which is just right for a big block stock engine. Good temperatures is a CAUSE of a well tuned engine, it shouldn't be the guide. You will find as you get better that you basically know what temp range your engine is just by how it is running.

Don't forget, this is all without even touching your LSN. Now, once the truck is shifting into 2nd gear and hauling butt at WOT, it's time to tune the LSN. Bring the truck in, and start turning the LSN, 1/8 turns at a time and repeat until you get strong takeoffs from a dead stop.

Once the LSN is dialed in, your truck should have great low and top end power and shift into 2nd.

Good luck!

ccamachotc3

it should be ur high speed is to high turn the throttle down a little first start with the high then with the low. also turn the carb needle towards the front of the car. i mean stand at the rear for the tires look at the carb and turn it forward to open it up if that doesnt work stand at the rear of the tires and turn it towards u. the mgt runs lean and rich but not to lean and rich if u get wat im saying

webdr

good info gribble. Im going to do what you recommend when I get home from work. Ill let you know.
Matt

webdr

OOOOKKKKKKK, Ive come to the conclusion that there is something besides the HSN causing this lean out...
Why?

I spent 2 hours adjusting the HSN in small increments with zero change in the conditions of the lean out. I richened it to the point of spattering and bad performance but everytime it cleaned out and the rpms got pretty high, it died.

I began to think there was a hole in the fuel line or air getting into the tank somehow so I held it and slowly advanced the throttle to wide open. All the while watching the fuel line....not one air bubble!

I then thought it was the fuel filter that I installed when I purchased it that was causing the fuel flow to be restricted and starvation at high load.......so I took the filter element out of the annodized filter case. No change at all.

I do know that its leaning out because when the engine dies, about an "inch" worth of air back siphons from the carb into the fuel line and sits there.

Is my fuel system not pushing enough fuel to supply the engine at high rpms? thats what it seems like to me.
I took the pressure end off and blew through the system as hard as I could. The fuel only inched out of the carb end....should it be really flowing??
Dale, give me some feedback bro!

webdr

Ha!!!! I figured it out!!! FACTORY SCREW UP!!!!


The primer ball has "A" marked on the inlet and "B" marked on the outlet. Each plastic ball valve that is inserted into each end of the rubber primer are also marked "A" and "B" for directional flow one way only. Well there were two "B" ball valves instead of one a and b.

They screwed me up from the get go and Ive been suffering for days trying to figure out why there was a lean out when in reality it was a total lack of fuel flow from the mis-assembled primer.

Thank GOD!

Dale Gribble

My Feedback: (4)

It makes sense that when you blew through the fuel pressure line that there wasn't a smooth flow on the carb side. The tank actually builds up a substantial amount of pressure (that's why it's sealed). You would have to blow significantly to build up tank pressure to get fuel flowing freely. It wouldn't like just blowing soda out of a straw so to speak as one would think. So, that's probably working as designed...

So, you are doing really good so far with good troubleshooting. You troubleshot the fuel side well as a cause of running lean and it sounds ok. However, there is another huge factor that causes lean performance- air leaks! An engine can run lean either by fuel starvation, or by excess air getting sucked in somewhere. If the engine gets air from anywhere besides the carb, the air-fuel ratio will be off and it will run too lean. I have had an engine run too lean because of a cracked carburator, but that was the POS composite carbs on a Traxxas 2.5.

You shouldn't have this problem and this could be a manufacturing issue. You have to decide whether you want to fix it on your own or get Team Associated involved and maybe RMA the engine and/or truck. I am happy to walk you through the process further, but since the truck is so new and under warranty, you might just want to talk with associated and send the engine/truck in (whatever they require.) Air leaks aren't easy to find and the engine would have to come out and be pulled apart. If it was an older truck, we could do it, sure.

Talk with Associated and see what they say. Granted new trucks can be challenging, but maybe not this challenging yet...

Dale Gribble

My Feedback: (4)

Sweet! Well, there ya go!

webdr

Im glad I finally figured it out cause Team Associated is currently changing to new headquarters and their phones are going to be down for a few days!

Ewanni

I'd still give Associated a call and let them know. If the primer ball limited the fuel you're getting, I'd be concerned that this happened during the break in process and ran it too lean.

I also have a new MGT and haven't started the break in yet. I just checked my primer ball and it has A to B going in the direction from the fuel tank to the carb. So this one looks alright.

mentorman

My Feedback: (2)

Your probably ok, unless you went lean at high speed, sounds like it never really ran that way. Call them and get a new primer anyways.