undercoverz-28

When i ran on the dyno i had my air/fuel read too and it read lean, 13.9 to be exact. i was told to get an adjustable fuel pressure regulator so i could up the fuel pressure and balance it out also increasing HP. Someone then told me the computer will still send the same ammount of fuel to the chamber so it didnt matter if i put one on. If anyone has any knowledge of this please let me know.....also a good adj. fuel press reg...if it will work. thanks.

96capricemgr

iTrader: (1)

That is a halfassed way of doing things not particularly appropriate for cars where doing it in the pcm is so cheap and easy. What all have you done to the car?

undercoverz-28

160 deg. thermostat, BBK Under drive pully, SLP CAI w/o the MAF sensor, full exhauts (mid length headers, Y pipe with no cats, etc...) with no O2 sensors anywhere....yes its been reprogramed, hotchkiss rear suspension kit, aftermarket torque arm and a pro 5.0 short shifter.
but as far as my a/f mixture i saked my teachers in my auto class and they said that 13.9 is a bit rich but almost perfect (14.7 = perfect) and not to touch it. so??????

TwoFast4Lv

iTrader: (8)

Some one needs to pull there head out before giving advise! (not you 96 )

At WOT on a Dynojet we shoot for 12.5-13.0 N/A.

14.7 will get you broken parts! I recently saw the inside of a Cobra engine where the owner was given the same advise you were....I saw it in an Engine shop...or I should say what was left of it! Looked like some one took a blow torch to the piston and cut clean through it and the rings to spray all over the nice rods those engines come with

I would run far FAR away from that advise!

undercoverz-28

thanks. finally it seems like someone who knows wtf they're talking about. any info on how to get it to balance out some would be useful. 96 said something about the pcm adjustment being cheap and easy??? shrug

96capricemgr

iTrader: (1)

Honestly if you are running NO O2s atall as in deleted the front ones too you are beyond help unless you are willing to step way back and do things right.
When modifying a computer controlled vehicle you will have MUCH better results working with the injection rather than against. Our O2s only function to keep cruise AFR around 14.7 which is where it should be and are a very good thing, the AFRs TwoFast listed are proper for WOT.
MAFs are a great thing for all but truely wild setups, it along with the O2s go a LONG ways towards keeping the motor running correctly at all times.

I guarantee you that if you put O2s and MAF back in and get good custom tuning like say madz28.com which is $125 for OBD2 your car will drive better and be faster. Not only can it get fueling right but can modify timing as well and tranny functions if applicable.

undercoverz-28

ya when i bought the car the guy before me had taken all this stuff out and i have no idea why. actually i think i do know why, from all the repair work i've already had to do to the car.....LAZYNESS. i've noticed some of his "shortcuts" and ghetto-ness like pvc pipe in the CAI where the MAF was and his crappy welding of the exhauts. the best has been the 3 or 4 bushings which crumbled out when i went to replace them. he even did the paint job in his back yard...which actually isnt too bad but anyway, i'm not keeping it. i wanna upgrade to an LS1 soon.

blkchevyz

that not really true, if you crank up the fuel pressure the computer will adjust the time the injectors stay open depending on how rich/lean it is... but at wot the computer will not pull fuel out. it will add it if the car was lean right before it went to wot.



oh and yeah put the o2s and maf back on.
you can probably get a muffler shop to weld some o2 bungs on for fairly cheap... if your headers dont have them already.

dhdenney

iTrader: (53)

Well, at Thunder, Shane told me to play with the fuel pressure until I got 43.5 psi with the vacuum line off. Then he said to play with the parameters in the computer.

blkchevyz

thats the best way of doing it.

01Z28M6

My a/f was 14 at WOT and I'm wanting to take it down to 13.
Does anyone have any experience with the Granatelli programmable maf sensor kit?

http://www.granatellimotorsports.com/gmmafamatic.htm

This seems like the way to go to me but I need help from experienced people.

thanks

dhdenney

iTrader: (53)

For the price of what thing probably costs, I would choose Lt1 Edit or Tuner Cat. You'll have more tuning options and ability.

01Z28M6

I posted this in the wrong section. My question is for the LS1. Sorry and thanks.

96capricemgr

iTrader: (1)

43.5 is supposed to be the stock pressure, so yeah adjustables are not that useful for most of us.

96capricemgr

iTrader: (1)

The answer still applies. Playing with the MAF or AFPR will accomplish halfassed fueling "tuning" but neglects timing adjustments software could make, software can also adjust tranny functions.

HBHRacing

the reason that adjustable regulators are produced for stock ish cars, is really for a different reason then most think. For example, TPIS points this fact out in there book but doesn't really explain why. The stock PE tune for LT1's is pig pig rich. TPIS tells you to buy there AFPR and LOWER the pressure. They say that they get a gain from this but not why. The reason why is because your leaning out the ratio and will make more power.


Do you need to do this? Not really. Your much much better off getting a quality custom tune done to change the PE tables. 99% of the time on a near stock car, they will lean you out. You will generaly pick up power and notice (epically in the case of a loudmouth system) that your exhaust note is cleaner.

Some people argue that APFR's are not needed because the PCM will adjust to the change in time anyway. This isn't really true. It will adjust based on idle and part throttle operation, but not in PE mode when the 02's are ignored and it runs off the PE tables and other inputs.

Higher pressure is also useful if your on the cusp of needing larger injectors. However it's important to note, that stock injectors can only operate on lower pressures then aftermarket. If your just about maxing out your injectors on a modded motor and don't want to switch from a 32pound to a 36 pound, Slight increase in pressure would just be a small safety buffer.

One other reason to favor a regulator is that at higher pressures, you get better fuel spray patterns, better atomization, and less biuld up on the injectors.


Summery: On a stock-mildly modded car, there is really no significant need for an adjustable regulator. highly modded motors might could use one for the reasons that I listed above. It's really not the correct way to lean a stock tune, or fatten up a lean tune.

As far as your dyno guy... never, ever go back to him again. 14.7 is your stoichiometric ratio. It's fantastic for good power, great fuel econ and low emissions........ while your cruising down the highway. at WOT when your in need of massive amounts of fuel, 14.7 will turn your pistons into Swiss cheese. in PE mode, shoot for 12.7-13.3 range and tune from there for best results.

z_speedfreak

iTrader: (3)

stoichiometry...you just brought back horible memories from high school. hahaha
thanks allot though, it cleared up alot of fog. =)

blkchevyz

you are correct that the o2 are ignored, but if the blms are way lean when it goes to pe mode its going to add a percentage of fuel to the table to keep itself safe.

dhdenney

iTrader: (53)

I bought one because I think my stocker crapped out. Although my fuel pressure showed good, I was only getting like 12 mpg with an M6. With the adjustable regulator as the only mod, I managed 18 mpg. Then I swapped in the auto and now I'm back to 12.

dhdenney

iTrader: (53)

I know O2's aren't the best way to monitor A/F ratio, but does anyone know O2s voltages for APPROXIMATELY 14.7 cruising? I don't have a wideband and will not buy one so I was always wondering how good my highway tuning was.