Single turbo/cam set up Cutting out at high RPM

[robbiegordon]

So I sent this question to my tuner to hear his thoughts but thought maybe someone here had or has the same thing happening

Normal daily driving everything runs fine. 3/4 or less throttle easing through gears... ect

However in 1-2nd mostly, around 4500-5000 rpm (revving up fast/ full throttle) it cuts out/ backfires slightly, sounds like its hitting the rev limiter or maybe traction control kind of. (Still does it with traction control on oroff) sounds like 2 step

It doesnt feel like its losing power when it does this but you can feel a little variation in the rpm

Doesnt do it as consitantly in 3rd or 4th gear, but occasionally it will when revving through 5k rpm

Not throwing codes

Over the last few months I've gone over plugs/plug wires checked grounds ect...

Fuel psi is holding 60-62psi under boost
And afr seems fine. Pegs over rich 10.5/11 ish

Car is ls3, cammed, single turbo, tuned on 91. Recently rebuilt the heads, new springs/valves ect.

Thanks in advance for any input !

[Greenhornet2]

Are you spinning when it happens? My TC will kick in even when TC is off if i get wheel hop.

[stevieturbo]

So has it ever ran correctly ? If so when and what changes have been made since ?

And what do you mean it "pegs rich"....even crappy gauges read down to 10.0:1, so the gauge cannot be pegged at 10.5:1 ?

[robbiegordon]

Originally Posted by Greenhornet2

Are you spinning when it happens? My TC will kick in even when TC is off if i get wheel hop.

Not spinning, does it after it hooks for sure

[robbiegordon]

Originally Posted by stevieturbo

So has it ever ran correctly ? If so when and what changes have been made since ?

And what do you mean it "pegs rich"....even crappy gauges read down to 10.0:1, so the gauge cannot be pegged at 10.5:1 ?

Yeah you're right. Technically not pegged. . But close . Ran correctly before alot of work. Cam replaced, heads rebuilt lifters replaced. Basically the whole valvetrain.

[robbiegordon]

My afr gauge is ballpark at best I think. Is why I say it that way. On the turbo downpipe. Very close to the turbo. ��*♂️

[robbiegordon]

Finished building it a year ago, just been dealing with the sputtering at high rpm.

[0331Marine]

Mine did it and it was a bad plug wire. It would break up under boost but drive normal if I wasn't in it.

[robbiegordon]

Originally Posted by 0331Marine

Mine did it and it was a bad plug wire. It would break up under boost but drive normal if I wasn't in it.

Thanks .for the feedback, I think I may just buy new plugs and wires again . Hopefully it's an easy fix

[Greenhornet2]

I wonder if you're blowing it the spark as well. Valve float would be another concern after a cam but shouldn't be a problem if you did good springs as well.

[robbiegordon]

Originally Posted by Greenhornet2

I wonder if you're blowing it the spark as well. Valve float would be another concern after a cam but shouldn't be a problem if you did good springs as well.

Yah, im going to pull the valve covers and make sure there isnt anything weird going on, but it's done it since day one. I'm using .660" PAC Dual Valve Springs

And TR7IX gapped to .028, considering gapping down a little, but I'm only making 9 psi

[stevieturbo]

So it's never ran correctly ? Has it ever been tuned properly ?

And does it run 100% at lower loads ?

[robbiegordon]

Originally Posted by stevieturbo

So it's never ran correctly ? Has it ever been tuned properly ?

And does it run 100% at lower loads ?

Its had this hiccup since day 1 but

Yes it runs great up until over 5k rpm in most cases. it doesnt always cut out. But I can get it to do it more consistently when flooring it through 2nd gear. I've done 4th/5th gear pulls and had it run 100% / No issues. But it will cut out ocassionally. ~ every other pull in 4th/5th.

I'm having the tuner relook at everything. But it is only street tuned through data logging at the moment.

The fact that it does it sometimes and not others makes me suspect its mechanical rather than tune, but I'm not ruling it out

[Greenhornet2]

My first thought was a fuel issue, but since you say there's no hiccup in the fuel pressure that kinda dashed that thought. I'm not familiar with turbo setups tho that would probably be what i was looking at next piping ect any restriction on the filter side, collapsing tube. But at 9 psi i wouldn't think so.