Sean
Newbie
I have a 2006 apex with a alpine front mount 2860 and I am having a heck of time tuning out a lean spot in the mid range. The sled has an old powderlites based dobeck box on it. This problem comes on during cruising along at half throttle running the mid range. The rest of the time the sled runs good. The low end A/F ratio looks good, the high end on boost looks great. The mid range looks good right up to about 6500 to 7000 rpm. Around that point, depending on motor load, the the A/F starts going lean and will creep up to 18.1 or 19.1 if you let it. While this goes on the sled starts missing and running bad of course. I know it's starving for fuel but I can't figure out how to find the right circuit to add fuel to help fix the problem. This usually happens when the sled is showing just few pounds of boost. It's like it has a problem and gets hung up when it switches from the main jet and goes over to boost. You can work your way right through it and it doesn't effect how it runs on the top but I know it can be better.
I know I am missing something simple and that this can be tuned out of it but so far it doesn't matter what I do with the fuel controller it just makes it worse. The fuel controller adjustments for a Powderlites dobeck box are these.
1- green - low end cruise circuit
2- Yellow - Accelerator pump
3- Red - Main jet
4- Green / blue - Boost fuel + or - when on boost
5- Yellow / blue - Lower switch point of yellow accelerator pump.
6- Red / blue - Lower switch point of main jet - means lowering rpm at which red comes on.
Any ideas or insights are defiantly appreciated. I know eventaully I will probably try a RB3 box but first I want to figure out how to make this one work. I know it's something simple. Thanks
I know I am missing something simple and that this can be tuned out of it but so far it doesn't matter what I do with the fuel controller it just makes it worse. The fuel controller adjustments for a Powderlites dobeck box are these.
1- green - low end cruise circuit
2- Yellow - Accelerator pump
3- Red - Main jet
4- Green / blue - Boost fuel + or - when on boost
5- Yellow / blue - Lower switch point of yellow accelerator pump.
6- Red / blue - Lower switch point of main jet - means lowering rpm at which red comes on.
Any ideas or insights are defiantly appreciated. I know eventaully I will probably try a RB3 box but first I want to figure out how to make this one work. I know it's something simple. Thanks
You need to look at the GEM box to see what color light is on. (green,yellow) When it is going lean, then add more fuel on the GEM for the same color.
Skydog P.S. I would bet it is going to be green but may be yellow...
Skydog P.S. I would bet it is going to be green but may be yellow...
I am sorry not GEM box but you get my point...
Sean
Newbie
Skydog, Thanks for the ideas. 
On this powderlites box the only time it changes lightes is when it is on boost. The rest of the time it just shows the one green light.
I did some more testing today. What seems to happen is that when the motor has a load and you are into the throttle about 2/3, the engine has built about 4 or 5 pounds of boost at this point. This also around the 7000 rpm range when it has built the 4 or 5 pounds under load. If I push thru it fast to full boost it runs great. If I ease into it, it starts leaning out real bad about 5 pound mark.
The question I have now is when do the dobeck boxes start picking up boost? Do they start adding fuel at 1 pound or 10 pounds? That info would defaintly help answer some of my questions
On this powderlites box the only time it changes lightes is when it is on boost. The rest of the time it just shows the one green light.
I did some more testing today. What seems to happen is that when the motor has a load and you are into the throttle about 2/3, the engine has built about 4 or 5 pounds of boost at this point. This also around the 7000 rpm range when it has built the 4 or 5 pounds under load. If I push thru it fast to full boost it runs great. If I ease into it, it starts leaning out real bad about 5 pound mark.
The question I have now is when do the dobeck boxes start picking up boost? Do they start adding fuel at 1 pound or 10 pounds? That info would defaintly help answer some of my questions
Are you good every where eles? If so go up on the green 1- 1.5
Skydog P.S. What does it idle at?
Skydog P.S. What does it idle at?
Sean
Newbie
Everything else looks great. I'm seeing 11.1 to 11.4 on top end at full boost. 14 to 14.5 at an idle and 10.1 to 12.5 all thru the bottom end till I run into this low boost lean spot.
I will have to check the idle RPM.
I will try richening up the bottom end also. At this point I am game to try anything.
The sled runs great other than this stumbling spot. It's more of pain in the rear than anything else.
I will have to check the idle RPM.
I will try richening up the bottom end also. At this point I am game to try anything.
The sled runs great other than this stumbling spot. It's more of pain in the rear than anything else.
Yea turn up that green buddy! I bet you will be good! May be alittle down on the red. Little more HP there.
Skydog
Skydog
Sean
Newbie
THanks!
Thank you sir for the info, I will try it tommorrow.
Thank you sir for the info, I will try it tommorrow.
Any time buddy!! Good luck!! AND BOOOOST AWAY!!!
Skydog
Skydog
Sean
Newbie
Just a quick follow up on my fuel controller problems. After some help from NM, Skydog and others I was able to tune some of the problem out of the sled. I was never able to totally solve it though. I did get my new PureLogic controller from Alpine motorsports and all the problems have went away. After talking to the guys at Alpine it turns out I had one of the earliest fuel controllers they had sold. After changing out the fuel controllers it was amazing how much better the sled runs. No more lean spost and way better throttle response. Sled seems to run great.
Anyway thank you NM, Skydog and others for the help. I apprecaite it.
Anyway thank you NM, Skydog and others for the help. I apprecaite it.
SWEEEEEEEEETTT! BOOOST ON BUDDY!!!!
motohd66
Pro
i am having the exact same issue while i am tuning in my pc111 on my s/c apex. right around 7500 it goes really lean and i cant seem to get it out but if i roll though that rpm range quickly it doesnt even affect the sled. i got a tip from mr. ulmer last night so i am headed to the lake to give it a shot.
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