Notices
HPI Monster Truck Forum Talk about HPI monster trucks here. The infamous Savage 21, SS, .25 or any other HPI MT. You can optionally discuss HPI in our general MT discussion forum if you prefer.

Savage x f4.6 cutting off after WOT

Old 07-19-2014, 07:59 PM
  #1  
Foslanden
Junior Member
Thread Starter
 
Join Date: Jul 2014
Posts: 8
Likes: 0
Received 0 Likes on 0 Posts
Default Savage x f4.6 cutting off after WOT

Hi!
Im new to this forum, and nitro cars in general. Got my first nitro car a few weeks ago and got about half a gallon through the engine.

Got some real trouble tuning the engine, the problem is the idle adjustment. Maybe a combination of the LSN and idle screw? I dont know.

Anyway the problem is that i cant have a low stable idle without the engine cutting after WOT (after i let the throttle off). I can adjust the idle so that the engine wont cut off, but then it will be way to high and engaging the clutch.

Dont know if it really matters, but after i let go of the throttle and at those times the engine doesnt stop, the idle drops instantly very low and then rises back up to where i set it to be.

This happens very often, and gets very annoying as i cant figure it out!
Hope anyone here can help me out

Got a video showing what happens. Didnt even go WOT here. Turn up ur volume to hear the engine.


https://www.youtube.com/watch?v=jBV-...9OFOknMngFTk6A
Old 07-20-2014, 07:57 PM
  #2  
-SomeGuy-
Senior Member
 
-SomeGuy-'s Avatar
 
Join Date: Nov 2005
Location: Montreal, QC, CANADA
Posts: 3,739
Likes: 0
Received 0 Likes on 0 Posts
Default

Looks like it could be a number of things but start with the most obvious which is tuning. Best thing to do when you're not sure is to start back at the beginning. Go back to factory settings (both screws flush with casing) and get it to idle. Next do high speed passes and tune the high speed needle till it goes as fast as you can get it to go, then back it down 1/8th turn. Next adjust the low speed be mashing the throttle from a stop till you get the desired effect. You'll probably need to adjust the idle as you go since, as you said the low speed and idle work together and have to be in harmony. Once you're done with the low speed, fine tune the idle and you should be good to go.

This being said you might have other problems as well. You could have an air leak on the engine (look it up) or your plug might not be the right one for your engine. One problem i had when i first started was i had the idle adjusted with a throttle that was held a tiny bit open by the servo and when i would brake it would die. Took me a while till i noticed this problem that had nothing to do with the engine. It doesnt look like you were braking so you can rule that out, its just an example of why you should never overlook anything.

Whatever you do dont pay someone to work on it for you. They overcharge, dont always do a great job and you learn nothing.

Good luck and welcome to the forum.
Old 07-21-2014, 09:16 AM
  #3  
Foslanden
Junior Member
Thread Starter
 
Join Date: Jul 2014
Posts: 8
Likes: 0
Received 0 Likes on 0 Posts
Default

Thanks for ur reply!
Few days ago i found a small air leak on the pinch bolt, that i sealed up. But didnt make any difference.
I have also adjusted the throttle trim so that when i break, the idle opening doesnt close.

About the tuning ive had a friend of mine who has had a savage x 4.6 for a few years, to help me out. But we just cant get this problem to go away.
Old 07-21-2014, 06:17 PM
  #4  
-SomeGuy-
Senior Member
 
-SomeGuy-'s Avatar
 
Join Date: Nov 2005
Location: Montreal, QC, CANADA
Posts: 3,739
Likes: 0
Received 0 Likes on 0 Posts
Default

Make another vid with as many examples as you can including some from a birds eye view with the lid off. Try and duplicate the problem in as many ways as possible. Someone might be able to spot something.

How long can you go WOT? Does it die when you let go of throttle? You mentioned that the idle drops very low when letting go of throttle after WOT. That is probably a rich high speed setting thats flooding the engine and it needs to burn off the excess to be able to idle properly. Either that or idle is set to low.

Keep us posted.
Old 07-21-2014, 06:48 PM
  #5  
Foslanden
Junior Member
Thread Starter
 
Join Date: Jul 2014
Posts: 8
Likes: 0
Received 0 Likes on 0 Posts
Default

Yeah i actually think the real problem is that the idle slows down when i let off the throttle, which is making the engine shut off before it has time to rise the idle to normal.
You say that it might be a rich HSN, but could it also be the LSN is too lean?
From factory settings ive now leaned out the HSN around 1 turn and richened the LSN 1/2 turn, I thought the factory settings was supposed to be very rich to begin with? How do i find out if its the HSN or the LSN? How do i move forward from this point?

Last edited by Foslanden; 07-21-2014 at 07:09 PM.
Old 07-23-2014, 12:45 PM
  #6  
pcarluvr
Senior Member
 
Join Date: Nov 2006
Location: butler, PA
Posts: 290
Likes: 0
Received 0 Likes on 0 Posts
Default

To me, it sounds like it is idling a little on the low side? Maybe adjust the air gap a little bigger with the idle stop screw. I think all nitro's call for a 1mm gap but sometimes just a wee bit more helps.
Old 07-23-2014, 06:35 PM
  #7  
-SomeGuy-
Senior Member
 
-SomeGuy-'s Avatar
 
Join Date: Nov 2005
Location: Montreal, QC, CANADA
Posts: 3,739
Likes: 0
Received 0 Likes on 0 Posts
Default

If its dying as you're giving it wot then HSN is to lean. If its dying after you let go of WOT then its rich with idle set to low. Factory settings are on the rich side but all to often they come from the factory way way to rich. A friend on mine had to turn in his LSN 4.5 turns just to keep the engine running, no amount of idle gap helped.
Old 07-24-2014, 05:10 PM
  #8  
Foslanden
Junior Member
Thread Starter
 
Join Date: Jul 2014
Posts: 8
Likes: 0
Received 0 Likes on 0 Posts
Default

Thanks for your help and support guys!

I think i got it running kinda good now, atleast its kicking wheelies and top speed is awesome.

But im gonna make a video of how the engine is running, idling, pinch test etc. The temp was kinda high (260) so i might have to richen the HSN alittlebit. The temp dropped fast on idle aswell.
Still alittle insecure about the LSN and idlegap, and where to set it. It seems fine for now, but ill let you deside when i get the video up.

Last edited by Foslanden; 07-25-2014 at 12:17 AM.
Old 07-26-2014, 09:21 AM
  #9  
-SomeGuy-
Senior Member
 
-SomeGuy-'s Avatar
 
Join Date: Nov 2005
Location: Montreal, QC, CANADA
Posts: 3,739
Likes: 0
Received 0 Likes on 0 Posts
Default

260 is fine, just keep it under 280, under 260 might be running to cold which is not any better than to hot.
Old 07-26-2014, 10:32 PM
  #10  
Foslanden
Junior Member
Thread Starter
 
Join Date: Jul 2014
Posts: 8
Likes: 0
Received 0 Likes on 0 Posts
Default

It was getting low on fuel, so might have been too lean. If you watch the end the engine just stops. The fuel tank was very low, but not empty.
The temp didnt drop at idle, which it did last time i drove it. Was aroud 247-250 now.
Pinch test sounded fine to me i guess.
Also theres very little smoke comming from the exhaust. But no matter how rich it is, there wont come any more smoke. I think its because of the fuel brand im using. 25% 9% Rapicon.

Let me know what you think of this
https://www.youtube.com/watch?v=e86L...ature=youtu.be

Last edited by Foslanden; 07-26-2014 at 10:39 PM.
Old 08-09-2014, 07:38 AM
  #11  
rcbence
 
Join Date: Jan 2013
Location: , OR
Posts: 50
Likes: 0
Received 0 Likes on 0 Posts
Default

If raising the idle or richening or leaning the lsn didn't help.....than I'd look into how much pinch you have left on the engine. If you take the piston and sleeve off.....push the piston up the sleeve. You'll see the top dead center wear mark. It should stop there. With a little bit of force it might go passed it a little.


Anymore than a little and its done.

I couldn't get more than 1.5 gallons on 2 4.6f engines.

They started doing the same annoying thing. Cutting out at idle. Couldn't hold a tune once hot.

9% oil doesn't help especially if you break them in at idle. I suspect its worn out.
Old 08-13-2014, 06:25 AM
  #12  
supertib
Senior Member
 
supertib's Avatar
 
Join Date: Mar 2004
Location: , MB, CANADA
Posts: 7,241
Likes: 0
Received 0 Likes on 0 Posts
Default

whats wrong with 9 % oil ?

what nitro % are you working with ?
Old 08-13-2014, 06:28 AM
  #13  
Foslanden
Junior Member
Thread Starter
 
Join Date: Jul 2014
Posts: 8
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by supertib View Post
whats wrong with 9 % oil ?

what nitro % are you working with ?
Nothing wrong, i just remember i read something about this fuel brand that it doesnt make as much smoke as other brands.

25% nitro
Old 08-13-2014, 06:58 AM
  #14  
rcbence
 
Join Date: Jan 2013
Location: , OR
Posts: 50
Likes: 0
Received 0 Likes on 0 Posts
Default

Couldn't see the vids as they are private. I just lookedthe fuel up.....its all synthetic. At 9% you won't see as much smoke. It might be less by volume. Wouldn't be surprized if it's 7-8.

IMO its not an air leak. The engine wouldn't dip down at idle. It would do the opposite.

Have you tried leaning the lsn from the factory setting?
Old 08-13-2014, 07:04 AM
  #15  
Foslanden
Junior Member
Thread Starter
 
Join Date: Jul 2014
Posts: 8
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by rcbence View Post
Couldn't see the vids as they are private. I just lookedthe fuel up.....its all synthetic. At 9% you won't see as much smoke. It might be less by volume. Wouldn't be surprized if it's 7-8.

IMO its not an air leak. The engine wouldn't dip down at idle. It would do the opposite.

Have you tried leaning the lsn from the factory setting?
I think the video works now.

I did find a airleak around the carb, sealed it up but didnt make any noticeable difference. Maybe it was too small. Shouldnt be any more airleaks now anyway.

I did try to lean the LSN but it just made everything worse. Richening the LSN and leaning the HSN made the car run kinda good, but now im scared i made that "rookie mistake" by richening the LSN covers up a too lean HSN.
Old 08-13-2014, 07:28 AM
  #16  
rcbence
 
Join Date: Jan 2013
Location: , OR
Posts: 50
Likes: 0
Received 0 Likes on 0 Posts
Default

Didn't sound that bad I guess. I think your lsn is close. If it was too rich it wouldn't accelerate that good out of the hole.

Even if the lsn is too rich you can still tune the HSN pretty close. Just gotta keep it at close to full throttle for a bit to clear it out. But you sound decent.

Its true though, that once you have a pretty good lsn tune and idle....it shouldn't be touched. Or at least very minor tweaks. If they get tweaked all the time its most likely air leak or worn piston/sleeve. If you don't have to tune those all the time then your alright.

The HSN just needs small tweaks if the weather changes.
Old 08-13-2014, 07:40 AM
  #17  
Foslanden
Junior Member
Thread Starter
 
Join Date: Jul 2014
Posts: 8
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by rcbence View Post
Didn't sound that bad I guess. I think your lsn is close. If it was too rich it wouldn't accelerate that good out of the hole.

Even if the lsn is too rich you can still tune the HSN pretty close. Just gotta keep it at close to full throttle for a bit to clear it out. But you sound decent.

Its true though, that once you have a pretty good lsn tune and idle....it shouldn't be touched. Or at least very minor tweaks. If they get tweaked all the time its most likely air leak or worn piston/sleeve. If you don't have to tune those all the time then your alright.

The HSN just needs small tweaks if the weather changes.
Oh thanks, i didnt know that ill try to set the LSN and idle gap as perfect as i can!

I think i can manage to set it properly now. Im starting to understand this whole nitroengine alittle better now.
But if i stumble upon more problems ill just reply to this thread
Old 08-18-2014, 02:59 AM
  #18  
supertib
Senior Member
 
supertib's Avatar
 
Join Date: Mar 2004
Location: , MB, CANADA
Posts: 7,241
Likes: 0
Received 0 Likes on 0 Posts
Default

the idle needle should be the needle you touch first when you retune day to day...when someone says you set it once then leave it they are very wrong.... idle gap is not something that can be preset to one setting...idle gap needs to be adjusted according to the amount of available 02 in the atmosphere........many times when the climate changes all that is needed is a slight change of idle gap, many people make the mistake of adjusting mixture needles first.....

Last edited by supertib; 08-18-2014 at 03:07 AM.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.