FourMoBro Posted April 20, 2009 Share Posted April 20, 2009 Any ideas what would cause AFRs to be high in the mid-range rpms, but fine in the lower and high rpm ranges? Background: My car was on the dyno after the latest goodies purchase. Come dyno time, and 2 hours later, the tune has to be called off because of this issue. Now the tuner, is a god. he has tuned over 3000 subies and has never seen anything like this. The whole shop crew, who are very very good, was looking over trying to figure it out. They check/replaced the fuel pump again, no fix They swapped out intakes, no fix They swapped out MAF sensors, no fix They think it may be an injector (DW 850), and will look at it again this week. They may try to get another set from the supplier. Any input form the forum? and no, i dont have any logs. List of mods can be provided if you think it is useful. Link to comment Share on other sites More sharing options...
rao Posted April 20, 2009 Share Posted April 20, 2009 Were the AFRs good at high rpm under boost? Rob IF YOU CARE ABOUT YOUR CAR YOU SHOULD NEVER DRIVE IT Link to comment Share on other sites More sharing options...
FourMoBro Posted April 20, 2009 Author Share Posted April 20, 2009 yes they were. I am no tuning genius, but i wanna say the AFR was between 17-20 between 2-3.5K and then would come down to 11 or 12 by redline. I think i am right in quoting those numbers. Link to comment Share on other sites More sharing options...
rao Posted April 20, 2009 Share Posted April 20, 2009 I'd bet on the fuel pump controller; it changes the duty cycle of the fuel pump based on load. Rob IF YOU CARE ABOUT YOUR CAR YOU SHOULD NEVER DRIVE IT Link to comment Share on other sites More sharing options...
FourMoBro Posted April 20, 2009 Author Share Posted April 20, 2009 so can that be reprogrammed in a tune, or replaced? How is it remedied? Link to comment Share on other sites More sharing options...
rao Posted April 20, 2009 Share Posted April 20, 2009 Replaced. It is a pretty small metal box bolted to the side of the trunk. The signal to it can be logged, but unless they really screwed up the tune he signal to it should be fine. The thing runs 3 duty cycles - 33, 66 and 100, corresponding to idle, part throttle and WOT. It might be skipping the 66. There is only one way to find out - measuring fuel pressure. Just about any 02+ Subaru has one, so a swap is easy. Either way a check of fuel pressure is needed. Rob IF YOU CARE ABOUT YOUR CAR YOU SHOULD NEVER DRIVE IT Link to comment Share on other sites More sharing options...
FourMoBro Posted April 20, 2009 Author Share Posted April 20, 2009 thanks for the input. I will report back in a few days. Link to comment Share on other sites More sharing options...
caramall2 Posted April 21, 2009 Share Posted April 21, 2009 Could it be FPR? My symptoms were a bit different, but that was the problem...the vac/pressure hose connecting the FPR to manifold popped off. Not to be dumb, but you are using a Wide Band O2 sensor, and comparing AFR of the wideband to you fuel map, right? Link to comment Share on other sites More sharing options...
rao Posted April 21, 2009 Share Posted April 21, 2009 It could be the regulator, but the shop with so much experience should have checked the obvious first, especially when it is so easy to check. Of course, the didn't have a fuel pressure gauge so you never know Rob IF YOU CARE ABOUT YOUR CAR YOU SHOULD NEVER DRIVE IT Link to comment Share on other sites More sharing options...
mickeyd2005 Posted April 21, 2009 Share Posted April 21, 2009 What pump are you using? Link to comment Share on other sites More sharing options...
FourMoBro Posted April 21, 2009 Author Share Posted April 21, 2009 walbro 255? Link to comment Share on other sites More sharing options...
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