M7 RGT servo closing causing bog. Fuel or electrical?

[bowerman61028]

’05 M7, Boondocker Race Gas Turbo @ 9 lbs @ 6,000-8,000 ft., running 110 premix, Boondocker box.

Was out riding and about ½ way back to the truck when the sled just bogged out and now won’t pull anything about 3,500-4,500 rpm’s. If you feather the throttle you can get it going but the mid-top of the engine is just not there. Got home and started going through the sled. Found that when the sled would bog the servo motor was closing and I thought causing the bog. I took the servo of a stock ’05 M7 and swapped them. When that didn’t work I swapped power valves and still got nowhere. Fuel pressure is a steady 45lbs and dips to 42-43lbs when it bogs down. I’m going to pull the primary and secondary injectors tonight to see if there are any problems with them and tomorrow I’m sending the box off to Boondocker to get updated because it is the original box from 2005. I checked the pistons and both are in great condition with no scoring or pitting.

I’m still leaning towards the power valves or servo being the problem because when you start the sled up and open up the throttle it will rev and the servo will open. Then the servo will close and it bogs. If you hold WOT it will rev then bog as the servo opens then closes.

Does anyone have a trick where I can fix the servo open to eliminate the power valves as a possible cause? Any other possible things it could be I’ll check if there are any suggestions.

 

[mt st helens]

I would say electrical. I tried the BDX delete but it made the bottom end worse that it already was so I went back to the servo. Is it not throwing the servo code on you? Mine would go into limp mode when my valves got dirty. But it would not cycle up and down. By the way my 7 runs a lot better at 12lb boost on 110 than it does on lower boost. I also just run 41lbs fuel psi.

 

[bowerman61028]

Is it not throwing the servo code on you? Mine would go into limp mode when my valves got dirty. But it would not cycle up and down. By the way my 7 runs a lot better at 12lb boost on 110 than it does on lower boost. I also just run 41lbs fuel psi.

It is not throwing any codes. I'm thinking I could switch the ECU from the stock M7 but I would also have to change the injectors because the turbo is a "square" and the stocker is a "triangle".

I have run 11lbs of boost, but I wanted to be safe while I was still dialing in the fuel maping. Once I have the maps set up close to what I want I'll be turning the boost back up. I'll try turning up the boost to 11 and adjusting the fuel psi.
Thanks for the tip.

 

[mt st helens]

I ran 50/50, 110/92 all last year on 12 lb boost.

 

[bowerman61028]

Figured it out last week. It was the screen in the tank that was kind of clogged. A coat hanger and new screen and the sled is dialed in.

 

[Tonysnoo]

Figured it out last week. It was the screen in the tank that was kind of clogged. A coat hanger and new screen and the sled is dialed in.

What did you find clogging them? Was it the black tar gunk?

Thanks for the feedback on the solution to your problem. Weird set of symptoms.

 

[bowerman61028]

What did you find clogging them? Was it the black tar gunk?

Thanks for the feedback on the solution to your problem. Weird set of symptoms.

There wasn't a lot of build up in the screen. When it was pulled out of the tank it was draining slowly. Replaced it with a new one and runs like a champ! Could have been going on for a while and finally just plugged up enough that it was a noticable problem. The up side is, I went through every electrical, fuel, and oil line on the sled before I found the screen on the tank so I know the sled is in perfect condition for the rest of the season. Could have saved myself a whole lot of time but it took a second set of eyes to see the problem. He figured it out in 1 minute and I felt stupid