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Car Forum / Ford / Ford Mustang / May 2005Dan's KB Odyssey continues
Well, I got the car on the dyno today and did some tuning to it. Right now, with a max of 17 degrees of timing and 15 psi of peak boost, the car made a best of about 454 hp/404 ft-lbs at the rear wheels, uncorrected (SAE 558 hp/497 ft-lbs). There's more power in there and the fuel system appears to be fine, however, there's some issue with the system that we can't figure out. On every run, at some point, the AFR started trending lean. We would adjust the tune and the trend would move out to a later RPM, but it would still occur. It looks to me like the MAF is behaving as if it were pegged but it's only showing 4.6 volts max at 6k rpm. So, right now, the AFR is below 12.5:1 all the way to 6500 and the timing is way conservative, so the motor is safe. But I won't spin her up to redline until we get an idea of what's up. The car moves though. It's a whole different beast just using the middle of the curves :). | The car moves though. It's a whole different beast just using the | middle of the curves :). Makes my heart beat fast just thinking how nice it would be! Kate >Well, I got the car on the dyno today and did some tuning to it. Right >now, with a max of 17 degrees of timing and 15 psi of peak boost, the [quoted text clipped - 14 lines] >The car moves though. It's a whole different beast just using the >middle of the curves :). lmfao is that all ya got hurc ast > Well, I got the car on the dyno today and did some tuning to it. Right > now, with a max of 17 degrees of timing and 15 psi of peak boost, the [quoted text clipped - 14 lines] > The car moves though. It's a whole different beast just using the > middle of the curves :). I'm not sure what other mods you have done but keep in mind that to make 550-600 rwhp you need to move allot of air. There might be a restriction in the intake tract or exhaust system. If you open it up the power will be there with a good aggressive tune. Since it performs well in the low-mid rpm range I bet you have a restriction somewhere that is hurting top end air flow. KB's respond well to large MAF's, throttle bodies and connecting tubes I dig. I've got a big throttle body, short inlet tube, and an open air element. The MAF may be the restriction but I know others that make more than me with it when they massage the signal to the PCM with a MAFExtender or Diablo MAFia. What makes me lean towards the MAF is that we used the transfer function to modify the fuel curve for this tune. After several adjustments it was clear that all of them were occurring around the same MAF voltage; 4.3 to 4.4 volts. So, the mass transfer function has this hump in it around 4.35 volts. Further, I was really anticipating the MAF to peg 5 volts; I'm moving enough air for that. Yet it never occurred even though, each time we made the run following an adjustment we took the car to a higher rpm. For example, the first run started the lean trend at around 4700 rpm with the MAF at about 4.4v. The next went lean at 4900 rpm and 4.35v, and the next 5200 rpm and 4.4v, and so on. So, it appears to me that the MAF signal has flattened out early, like it's pegged. Dan 2003 Cobra convertible With some stuff and things I not real familiar with the Cobra fuel systems but have you checked fuel pressure to see if is is a fuel supply problem? It could be the source of a lean condition. What size fuel injectors are you running? > I dig. I've got a big throttle body, short inlet tube, and an open air > element. The MAF may be the restriction but I know others that make [quoted text clipped - 17 lines] > 2003 Cobra convertible > With some stuff and things The fuel pump duty cycle was around 49% on these runs, with a KB Boost-a-Pump set at 25%. The BAP increases the pumps' flow capacity and the stock fuel pumps need a bit of help for these power levels :). My fuel injectors are 39 lb/hr at Ford's rail pressure. They should be able to support the current power although they will be a bit over 80% duty cycle. Also, every time we demanded more fuel we got it and the curve richened up a bit. I would think that if the car was out of fuel, either pump or injector, the system would just continue to go lean on me no matter what was demanded. Unless I'm missing something in my thinking :). One thing I've just discovered is that I need to rewire the BAP. I wired it according the instructions but there's apparently an "upgraded" wiring procedure that improves it's utility on my car. I dunno if that will help but I'm on it :). Dan 2003 Cobra convertible With some stuff and things > The fuel pump duty cycle was around 49% on these runs, with a KB > Boost-a-Pump set at 25%. The BAP increases the pumps' flow capacity and [quoted text clipped - 11 lines] > "upgraded" wiring procedure that improves it's utility on my car. I > dunno if that will help but I'm on it :). IMO, 39# injectors are cutting it close for power levels over 400+ rwhp. Also, on the 5.0L cars getting over 80% on the duty cycle was cause for concern. I think the returnless cars raise the fuel pressure a good bit more than the old style so maybe the thresholds are different. |
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