Engine bogs after idling

[Th3Art0fRu1n]

Hello everyone (I know this is a long thread, but bear with me please)

I have an OFNA Hyper 7 TQ 1/8 scale buggy. I got it about a year back and played with it on and off. Recently, I got back into it and finally got it tuned to my liking. Everything seems to be in its correct place (as far as the needles go).

There is only one problem I'm experiencing:
My car runs great. It accelerates nicely, reaches top speed and doesn't bog. However, when I let the car idle for a bit (maybe 30 seconds, or enough time to refill the gas tank), I cannot take off without blipping the throttle a few times to clear it out. I do realize that if an engine idles too long it will "load up" and must be cleared by tapping the throttle a bit before it can run at full. The car will idle forever, at least until it runs out of fuel.

Lately, though, I've noticed that it will do this without idling for a long time. Sometimes I will run a lap or two, then pull the car up to my feet to inspect for loose nuts/bolts/etc (just 15-20 sec at the most) and when I give it full throttle it will bog and die if I'm not careful. I'll have to let off and blip it a few times before I can run it at full throttle. When I apply the throttle after letting it idle for a bit it produces a lot of smoke. Once this smoke returns to the normal amount (i.e. what it should be under normal circumstances), the car is fine.

I have a feeling my LSN is running too rich. I read something about this possibly being caused by setting the LSN too rich and having the idle set too high, causing a false idle and excess fuel to build in the engine. This, in turn, will cause the engine to cut out after applying a lot of throttle after idling for a while.

I may not be describing this correctly, but it is getting to me. Any help would be appreciated. I can clarify on things if I missed something. Thanks for any help guys, I'm looking forward to getting to know some of you!

Edit: I have read through multiple tuning guides, including the one on this site. They don't seem to help me, but I may be reading them wrong or missing something. Once again, any help would be greatly appreciated.

-Harland (Ru1n)

 

[mrbones]

This is for your LSN adjustment. Get it running and pinch the fuel line. Right before the engine stops, the RPM should rise just a little and stall. If it rises a lot, lean it out and do it again until you get it to rise just a little. If when pinching the line the engine just dies with no RPM increase, it is too lean. You need to set your idle air gap at about 1mm (the thickness of a credit card) before you adjust the LSN.

 

[ozziii]

It does sound like your LSN might be set to rich, a small adjustment to lean the bottom end would probably help. Try out what mrbones has said above, or if you do have a good amount of smoke coming out at low revs, then you could just lean the LSN 1hr at a time & you should see an improvement. Watch the temps though & make sure there is smoke right through the rev range.

 

[lesclaypool]

Sounds like you've done your homework and are on the right track! I'm pretty sure you nailed it, and the problem lies in your LSN. I know you mentioned that you've read the tuning guides, but have you read this one: https://www.rcnitrotalk.com/forum/showthread.php?t=76808

I think if you set your idle gap to.5-1MM max, and follow that guide exactly, you'll get that LSN dialed in in no time.

 

[Th3Art0fRu1n]

Thanks for the responses guys! Unfortunately, I'm in the process of repairing my setup. I had issues with the steering links and stock receiver battery pack. Too much bashing All I have to do is put in the new battery pack and I'll be ready to get back out there and give it a go. I also forgot about my exhaust gasket (that seals where the manifold meets the engine) is burnt and cracking a little. I noticed it a little while back (maybe a month and a half) and forgot about it. It hasn't gotten any worse, but I'm sure it isn't helping. I'll get on that asap.

I've always figured my LSN was too rich, but when I would lean it out I would get a high idle when I bring the car in from a few laps. I think I've been keeping my idle too high and my LSN too rich. I'll be ready to run tomorrow or the next day so I'll keep everyone posted. Thanks.


@Mr. Bones: I've noticed that when I do the pinch test, I usually end up with the engine taking a while to cut out and the RPM raising a lot. I've tried using this method, but maybe I just haven't given it enough time. Thanks for the advice.