Warbling sound coming from nitro engine

bobbd

Well-Known Member
Messages
153
I think i got this 4.6 tuned finaly i can get temps up to 225 -230 after half tank of fuel with blue smoke but when i let off trigger i here a warbling sound Is that normal?
 

BrandNewSavvy

Member
Messages
6
Hi my friend,

I think it's very difficult to diagnose without actually hearing the engine, but the wookie sound (love that description BTW) is quite common. However I would do the exact opposite of what is written above, in this case.
The 'wookie idle' is almost always due to the HSN being lean and the bottom end being fat (rich). So richening would just make it worse. I see it a lot though as it does mask the two-stage (so it makes the idle sound "less bad")...but it's going backward with respect to tuning your engine.

So as an example:
1. Your wookie sound is due to the idle gap being so wide open.
2. Go try to close your idle gap. Most likely you wont' be able to close it any further without the engine stalling.
3. The reason you can't close it is because....the low end is too rich.
4. So...you need to lean the low end, and then you can decrease the idle gap.
With that said, it's not just turning the low end and hoping it starts to sound right. THere are explicit keys you should be listening for when you are tuning the low end. else you the only way to tune it is to...get lucky! ;)

Finally, don't let it frustrate you. Getting the idle to settle down and still allow the low end to crisply clean out is perhaps the most difficult part of the tuning process. Most folks just give up and make it by raising the idle which is why you see so many de-tuned engines.
Good luck!
 

bobbd

Well-Known Member
Messages
153
Can not get rid of the chewbacca sound it happens when i let off throttle..ive leaned and richened the low speed needle to no avail..other then that runs great.
 
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