2 stroke engine flutter

[hivoltagesledhead]

I have a flutter in my 09 summit 800 turbo engine that occurs in the midrange and at full throttle. Any one have any ideas what this may be and how to correct it? I have tried jetting up and down...raising and lowering needles. I have tried 4 different plugs and different combos of race gas and 91.Could it be an electrical issue? possibly a timing thing? It keeps throwing the knock code and when I pull out of that rpm the code goes away. It is driving me freakin nuts.
I did plug checks(kill the engine when it happens and let it come to a rolling stop) when the flutter occurred and the plugs are awesome. Actually,the plugs look great throughout the entire powerband. It happens at all altitudes,choke on or off,powerjets opened/closed more or less,egts cold or hot,on or off boost but always in the mid range and ft.
I am going to doo dealer to get my codes cleared and see what they say.

Any other ideas?

 

[gus bohne]

FWIW..

My sucess rate with reprogramed cdi's is less than 50 % with BRP
With Poo its about 30%.

On 1 particular xp turbo same issue as You,, found timing in 6000- 7500 range at + 32 degrees !!!! thats + 7 from stock...NO adjustments were made according to them..??? others that would not rev past 1500 rpm,, sent back and worked when returned..rev limit accidentally moved down to 1500 ???

swap boxs ?? put a timing light on it and check ?? I check with a light on the stand or dyno with a friend to operate throttle..NO more than 14 at peak rpms,, like 14 from 7800-8400 then down to 12 after that..

use the cheap timing lights,, Snap on will not keep up ,, goes out over 5000..

You can install the degree wheel under the clutch bolt,, LEAVE clutch on...make a pointer or put a mark anywhere you can and set degree wheel at .065 down at 15 degrees.. Now your dead on for TDC..good to go.
Unfortunalty we have to triple check all work we SEND out for errors..


Gus

One unit would deto pistons at 11.1 on o2 gauge ONLY at part throttle or in mid rpm window where timing was WAY out of spec..

 

[powder freak]

I don't have a turbo xp and I'm not familliar with that system. I'm thinking of building one for next season and just looking to get some info. I currently have a turbo m8 and was having a similar problem as you. I could dial the fuel controller as high as it would go and no change. I turned up the fuel preasure to 42psi from 36psi and dialed the fuel controller back down to where it should be and problem solved. Again I'm not familliar with your system but it sounds like your not getting enough fuel in. Hope this helps

 

[nuttyn01]

flutter

I would pull your fuel pressure regulator apart....you might have a blown diaphram.

 

[brycter]

sounds like pipe surge to me. the only way that i know to get rid of that is to clutch through it or get a different pipe.

 

[hivoltagesledhead]

What is pipe surge? Neil built my pipe with the engine & turbo specs that were given to him,so,I would think that pipe surge should not be the issue.

 

[gus bohne]

bov creep at mid rpm, fuel pressure creep from routing the reference from the same souce as the bov.

Wish you and niel would take your turbos to someone and identify them. Halverson was buying 2860's from silber.If they are 2860's thats the route of your issue with altitude.
Mallory regulators are well known to fail , they dont quit, they leak down and drop fuel pressure over 5 seconds. it doesnt show until you are at a steady prssure not on and off the power.
aeromotive all the way.
Gus

 

[hivoltagesledhead]

I talked to a garret dealer this am in Kentucky and he confirmed that I do indeed have a GT2871R turbo....so we can eliminate any 2860 issues from the problem.

 

[winter brew]

I know little about turbos, but what you describe can occur in a NA if there is not enough load on the clutching.....perhaps add weight and see what effect it has. ??
Or try wrapping the pipe. ??