About to install my MAP adjuster but...

[aaronkeiser]

called up Autozone and they've got the fuel regulator I need so tomorrow im gonna swap that bad boy in and see if it runs better. I took your advice 4.whoa and took my beast for a drive but forgot to cap the hole on the regulator. seemed to run a little better.

Does bumping the fuel pressure up 6 psi seem too much adjustment with 24lb. ford injectors?

[aaronkeiser]

If I'm running lean while just cruising down the road under light throttle (lets say 45MPH) would the adjustable map sensor fix my problem? Or does it only fix WOT lean mixtures? If so would a piggy back computer be the only thing that would fix my lean condition?

Any help would be great...im currently rolling around with expired registration so quick replies are needed. Thanks guys

[gradon]

The computer will add and subtract fuel to keep 14.7:1 in closed loop. I don't recall the max +/- but let's say it is +/-30%. Without the adjustable map, let's say your long term fuel trims are +20%(adding fuel to keep up to the 14.7:1), and your WOT is 16:1. You adjust the map so you get the 12.5:1 in wot and now maybe the pcm is adding +10% or taking out -10% to maintain the 14.7:1. On obd2 vehicles, you can plug in a scanner and get the real time fuel trim values. There are ways to getting around the 14.7:1: piggyback and standalone ecus, wideband o2 sensors with adjustable narrow band outputs to bias the o2 sensor(some people trick it to be leaner and save gas). My stroker doesn't like the 14.7:1 in the 2200-3000 closed loop range due to the high comp. I've been thinking about forcing it into open loop by disco'ing the CTS in the t-stat and tuning the psc1 to make that band richer than stoich.

[dwg86]

Don't mean to highjack this thread, but what is your comp ratio Gradon?

[gradon]

10:1scr 8.57dcr. I use 93 octane only and the rc7s, which reduced the pinging a bit, but it is there hot or cold so I know it is due to the compression. There's no lack of power and I never baby it, but it'd be nice to get to the bottom of it. For those planning high comp builds: Keep the DCR <8.4:1 and quench .040"-.051"(compressed gasket thickness and maybe a few .00_").

[aaronkeiser]

The computer will add and subtract fuel to keep 14.7:1 in closed loop. I don't recall the max +/- but let's say it is +/-30%. Without the adjustable map, let's say your long term fuel trims are +20%(adding fuel to keep up to the 14.7:1), and your WOT is 16:1. You adjust the map so you get the 12.5:1 in wot and now maybe the pcm is adding +10% or taking out -10% to maintain the 14.7:1. On obd2 vehicles, you can plug in a scanner and get the real time fuel trim values. There are ways to getting around the 14.7:1: piggyback and standalone ecus, wideband o2 sensors with adjustable narrow band outputs to bias the o2 sensor(some people trick it to be leaner and save gas). My stroker doesn't like the 14.7:1 in the 2200-3000 closed loop range due to the high comp. I've been thinking about forcing it into open loop by disco'ing the CTS in the t-stat and tuning the psc1 to make that band richer than stoich.

I understand what your saying but I was under the impression that the OBD1 (87-95) computers had pre programed fuel tables and didn't change. Mines a 91...first year of the MPFI in wranglers.

[4.whoa]

'87-90 are renix. '91-95 are obd I. All 4.0's are MPFI. '91 was the start of the HO.
They all run "maps" in closed loop and off the sensor inputs in open loop.

[SilverXJ]

you got that backwards. Open loop = no O2 sensor input, but other sensors, relies heavily on a fuel map. Closed loop = O2 sensor and other sensors read, relies heavily on O2 data.

[4.whoa]

whoops

[aaronkeiser]

Ok well now that i've beatin the smog nazies I'd like to correct my fuel problems. Would the best place to start be a Wide Band O2 sensor and go from there?

[Comanche91]

Yes, I would say so. You have to verify closed loop operation and know the stoich A/F ratio before you can dial it in. Otherwise you're more or less just Easter egging.

[SilverXJ]

x2 on the wideband

[herbiehind]

i'm new to this but dino's site talks about the need for an adjustible fpr on the pre 99's

[Cheromaniac]

i'm new to this but dino's site talks about the need for an adjustible fpr on the pre 99's

Either an adjustible FPR or a MAP adjuster. The difference is that with the AFPR you can raise the fuel pressure to get more fuel flow from the same injectors without altering the duty cycle, whereas the MAP adjuster allows you to raise the duty cycle to hold the injectors open for longer.
Both will allow you to enrich (or enlean) the A/F mixture but by different means. A homebrew MAP adjuster will only cost you $10 v $200+ for an adjustable FPR if cost is an issue.

[aaronkeiser]

I'm almost positive that I need more fuel but I won't know for certain until I splurge on a wide band O2. My motor defiantly pings under load (about 70% and up throttle) So I'm also between an adjustable MAP and and adjustable FPR or both.

Is upping the fuel pressure the same as adding bigger injectors?