Attention Problem Solvers - sled dies at higher RPM.

[SnowBigDeal]

Calling all problem solvers to my rescue

Sled: 2007 M8, Speedwerx Y-Pipe, Pipe, Can. Stock Fuel controller.

Background: First off, my compression in my PTO cylinder is down 10PSI from my MAG side due to stupidity on my part two weeks ago. I ran NOS without bleeding the air out of the fuel line (BOSS NOSS system). Therefore I detonated a lot on a big pull and thought I lost the piston but I was lucky to only be down 10PSI. Result was that I dropped from 7900 RPM to 7500RPM, but it is still good enough to get me through the rest of the season.

I went riding on Saturday and everything was working great, including the NOS.
Later in the day on a big climb I hit the NOS button for a split second (literally less than 1 second) and engine shut down. I pulled the pipe and the plugs and things appeared to be normal. I put the plugs back in and the sled ran, but only on one cylinder. I was not getting anything out of my PTO side no matter what I tried.

I got the sled home, checked my compression and nothing had changed from my initial readings before I went riding. I put my plugs back in and my sled fired right up and is running on both cylinders.

Here's the problem solving piece: Running in my garage, with no load on the track, I warm the sled up and run it steadily from idle up to 6800 rpm, and then the sled shuts down. It almost dies but continues to idle, then I can run it back up to about 6800 RPM and the sled dies again. I can hold RMP's in the 5k range, but as soon as I get into the High RPMs range, the sled dies back down to an idle.

Question: Any ideas on why it dies and won't hold anything in the high RPMs?

I'm stumped.

 

[KSH]

Are your power valves "Servo" opening?

 

[SnowBigDeal]

I thought about the servo and inspected things as far as I know how, which isn't a lot. I'm not getting the servo check light and none of the cables appear to have grounded out.

What is the best way to check the servo with the engine running?

 

[KSH]

I thought about the servo and inspected things as far as I know how, which isn't a lot. I'm not getting the servo check light and none of the cables appear to have grounded out.

What is the best way to check the servo with the engine running?

Just pull the cover off the Servo and watch it in the higher R's. It will twist to pull on the cables.
I don't know the 800's, but your problems seem to be in the power valve opening rpm range.

 

[minet]

i would pull the top end , maybe you mini siezed and if your deto was bad enough put tiny pieces or piston top around the sides , inducing sieze again.. then when it gets hot enough she squeeks

 

[m8magicandmystery]

reed or power valve issue possibly to start looking first ..and just for the heck of it when its running spray some starting fluid behind your primary clutch at the pto seal and see if it affects the rpm...just maybe she is really leaning out through a bad pto crank seal..

 

[markoo]

If you detonated and now have less compression and less rpm you need to park it and pull your engine apart before you blow something up and lose a cylinder of even worse your crank.

 

[SnowBigDeal]

Thanks everyone for the help so far. I have still not figured out the problem and it doesn't appear to be my Servo motor.

If you detonated and now have less compression and less rpm you need to park it and pull your engine apart before you blow something up and lose a cylinder of even worse your crank.

I agree completely, but I would first like to diagnose why my engine shuts down at high RPM. Otherwise I will rebuild and once I get it back together I will be trying to diagnose with a new top end, which I think is a lot more difficult due to break-in procedures.

 

[mmsports]

Without hearing it.

It sounds like your stator is coming apart and loosing contact. I would put a new stator in it should fix it. If its not the stator it in your wire harness but I would say stator first.

 

[backcountryislife]

I'm leaning toward Kevin's take, stator or electronic.

After hearing it run on sat, it's not valves at all. The problem happens before that & sounds nothing like a shut valve.

 

[KSH]

Calling all problem solvers to my rescue

Sled: 2007 M8, Speedwerx Y-Pipe, Pipe, Can. Stock Fuel controller.

Background: First off, my compression in my PTO cylinder is down 10PSI from my MAG side due to stupidity on my part two weeks ago. I ran NOS without bleeding the air out of the fuel line (BOSS NOSS system). Therefore I detonated a lot on a big pull and thought I lost the piston but I was lucky to only be down 10PSI. Result was that I dropped from 7900 RPM to 7500RPM, but it is still good enough to get me through the rest of the season.

I went riding on Saturday and everything was working great, including the NOS.
Later in the day on a big climb I hit the NOS button for a split second (literally less than 1 second) and engine shut down. I pulled the pipe and the plugs and things appeared to be normal. I put the plugs back in and the sled ran, but only on one cylinder. I was not getting anything out of my PTO side no matter what I tried.

I got the sled home, checked my compression and nothing had changed from my initial readings before I went riding. I put my plugs back in and my sled fired right up and is running on both cylinders.

Here's the problem solving piece: Running in my garage, with no load on the track, I warm the sled up and run it steadily from idle up to 6800 rpm, and then the sled shuts down. It almost dies but continues to idle, then I can run it back up to about 6800 RPM and the sled dies again. I can hold RMP's in the 5k range, but as soon as I get into the High RPMs range, the sled dies back down to an idle.

Question: Any ideas on why it dies and won't hold anything in the high RPMs?

I'm stumped.

It sounds like your stator is coming apart and loosing contact. I would put a new stator in it should fix it. If its not the stator it in your wire harness but I would say stator first.

I'm leaning toward Kevin's take, stator or electronic.

After hearing it run on sat, it's not valves at all. The problem happens before that & sounds nothing like a shut valve.

Are you sure that The Noss caused the detonation or could it of been the beginning of a electrical "stator" problem?

 

[backcountryislife]

The sled sounded perfect before he did that climb, seems odd that hitting a tad of nos would happen to coincide with an electrical problem if it wasn't somehow related. Could something have gone wrong with the boss system that would cause this?

 

[m8magicandmystery]

check the integrity of the boot seal between the throttle bodies and the cylinders as well..can use a spray as well to check...(leaks/cracks ets)..the possible reed/crank seal or boot issue possibilities could happen from a nos malfunction imo...and possibly just not the volume of fuel to sustain steady higher rpm..enough to coolect at lower rpm to get it to raise the the volume can not sustain it...so the pick up smart valves in tank acting up or fuel pressure or injector...??

 

[Qreiff]

I too, lean toward a bad stator issue, or electronic..........

 

[Rms Rydning]

Are the lights working on your sled?

If the fuse at the CCU is gone, the exhaust valves vill be closed, but you have no lights also...But it will not shut down the sled, it will only restrict the rpm to around 6500rpm..