M8 bog on top end frustrating! please HELP!

[akmaxdawg]

I have a 2005 M6 that has a D&D m8 kit in it with a D&D single pipe and D&D can. Timbersled intake. Boondocker box. supreme tool rave style exhaust valves to eliminate that problem. It is a really great sled when it runs but last winter i couldnt figure out what was causing my problem. I have good compression on the both pistons. replaced the throttle bushing.Here is the problem:

Sled runs very strong and normal up until 6500rpm where it bogs. When it bogs, the EGT shows the PTO cylinder losing all temperature and going back to 700-900degrees or lower while the MAG side cylinder is reading the normal temp of 1200-1250 degrees. Once in a while it seems if i let the sled cool down(5-10mins) i get full power for a short burst of 10 to 45seconds or until i hit a bump or something that puts an additional load on the eingine and then back to the bog of 6500rpm . When it runs for a brief couple seconds it runs like a raped ape with both egts reading normal temps. so that makes me think that it is not a clutch problem. plus if you put the sled in the garage and runs adn shifts it up it runs up fine. i have checked the barometric pressure sensor coming from the efi box and it is free and unrestricted. The air temp sensor is mounted in the timbersled intake and was not an issue in the stock intake or the timbersled intake because the problem had not changed. I rode the sled all last season like this with the intermittent burst of power but 99% i was limited to 6500rpm. I still managed to put 800mi on it last year and tow various skiers around the alaska backcountry. This fall i want to get this thing fixed!

Here is what i have come up with:
engine is obviously cutting out on the PTO cylinder at 6500rpms in someway causing me to lose egt temperature to about 700-900degrees. after reading through the forums for help this is what i am thinking.
stator failing - cant supply enough spark energy but why would it go for so long and not completely fail?
Corroded injector wire- not able to keep spark energy at high rpms
Coolant bottle cap cap has typical sealing issues - but why the intermittent power just to tease me?
Faulty injector seems like its in the area and could cause a problem like this.
Bad efi box i hope it is not this, and why would it run once in a while at full power?

I will also try to emulate the problem in the garage where it appears to run fine. ( no load) I will be trying the coolant tank replacement to see if that gets me better results first since it is the cheapest and easiest to fix at the time. Any help would be greatly appreciated. I just wanna keep her pinned at 7800rpm because that feels so damn good!

 

[mtn_extreme]

What elevation?

Sounds like your to fat on your boony numbers and getting a fat bog. Easy to do.

Also, what is your clutching? if your helix is too steep it will bog on top as it cant hold it.

 

[tundramonkey]

Exhuast valve sticking on the PTO side? Can you switch sides with that type of valve to see if the problem follows the valve?

 

[winter brew]

Try fixing the EV's wide open, also make sure all the BD box wires have solid clean connections and nothing is melted. How about melting around the injector harness?? Taillight wire grounding out at the rear of the tunnel??
Secondary spring adjuster backed all the way off (yes, it CAN make a HUGE difference)...and have you tried the stock silencer?

 

[mtn_extreme]

That would have been my next suggestion, put the stock pipe and can back on and see what happens.

 

[diggerdown]

Did you try switching the plug wires around to see if the mag side dropped temp and the pto stayed up? Could be the coil or the wire. A sticking exhaust valve or bad injector or injector wire plug perhaps.

 

[F_ast]

can also check TPS. Make sure you arent pulling the safty switch from your throttle cables being too tight. Had a similar issue on my F7 when i added my riser. i just cut all the zip ties and freed up as much slack as possible. What happens is the computer cuts out a cylinder at 6300 rpm and wont open the AVP, sled just falls on its a$$ like your running out of gass

 

[akmaxdawg]

back to wrenchn'

Thanks for all the support and quick responses!
Ive tried adjusting the boony numbers and that doesnt seem to take the bog out. helix is a 36, elevation for riding is 0-3000ft. I will be trying just about all the suggestions that have been offered over the next couple days and post my findings! Thanks for the help! Max - bound and determined.

 

[akmaxdawg]

Just a quick question

How does the efi box control just one cylinder? It seems to me that only fuel could be regulated on a cylinder per cylinder basis (not spark)and this would send me down the injector, wiring harness, wiring short path. If I switch the plug wires and I still get the identical problem. then it would seem that some where in the fuel delivery system would be where the problem would lie.

I have had the servo actuated EV's go out me hence the gas operated EV's. The engine actually limped on both cylinders not just one. I can pull the valves up with my fingers freely so i would think that should normal. Also can anyone explain the mechanics of how the engine responds to the coolant system lid not closing tight could affect the motor. I realize that the coolant doesnt build pressure but how does that affect the running of the motor?

 

[m8matt]

I would go after your exhaust valves. I am pretty sure they are supposed to open right around the rpm you are having problems. Try putting the stock ones back in and see if it works. Or try switching them from one side to the other. It's an elimination process. Do one thing at a time and you will track your problem down way faster.

 

[mtn_extreme]

Coolant won't affect it until it gets to hot and then it will go into limp mode. To adjust individual cylinders you have to use the trim button in your settings, this will add or subtract from the pto side(?) or the mag side, don't remember which. But you set can tell with your egt's/

 

[m8matt]

Coolant won't affect it until it gets to hot and then it will go into limp mode. To adjust individual cylinders you have to use the trim button in your settings, this will add or subtract from the pto side(?) or the mag side, don't remember which. But you set can tell with your egt's/

I wouldn't adjusting my boondocker box at all. Eliminate the easy stuff first. It doesn't cost you anything to put your stock stuff back on. Assuming you still have it. Try one thing at a time.

I have been over the same thing with my m7. I put a whole bunch of after market stuff on and it ran worse than when I started. I ended up starting over at stock and adding one thing at a time. It ended up being the aftermarket silencer that I had. For what ever reason my sled didn't like it.

I don't think you want the repair bill leaning down one cylinder.

 

[diggerdown]

There also has been a number of the boondocker boxes that were faulty.

 

[akmaxdawg]

the one cylinder

Just playing the devil advocate here but how would the can affect just one cylinder with a single pipe? That seems to be the oddest part to me.

 

[JHG]

There also has been a number of the boondocker boxes that were faulty.

This is my bet. I would send it in and have it tested while they are slow for the summer. If its not exaust valves I would say next look at the BD box.

 

[mtn_extreme]

"I wouldn't adjusting my boondocker box at all."

I guess if you don't understand the box then this might be safer, but if one cylinder is bogging and not the other, it very easily could be that your running on the line of fat or lean and one cylinder is handling it and the other isn't. They usually do not run even.

 

[slomo]

why not swap injectors side to side to eliminate them as the problem

 

[akmaxdawg]

I have tried to leaning down the PTO side cylinder to see if was running rich with out any luck towards my problem. I think that i will send the box back to see if it has gone bad too.

 

[akmaxdawg]

Alright im getting a good plan of attack for this beast. Im gonna swap plug wires first. then swap injectors. replace the stupid coolant tank and cap with the 07 screw on lid. see how she goes. then it would be the BD box. I really would like to thank everybody for their support!

 

[SafetyBob]

Alright im getting a good plan of attack for this beast. Im gonna swap plug wires first. then swap injectors. replace the stupid coolant tank and cap with the 07 screw on lid. see how she goes. then it would be the BD box. I really would like to thank everybody for their support!

Whoa! Hold on a minute, you should really call Boondockers first, 1-877-522-7805 ask for Junior or Kyle they will walk you through this. Thanks Diann