maf question

[390STEVE]

I was driving my car today the temp was 49 out. I noticed that my scan master went from normal 812 area to 754. Is this because my maf does not read the amount of air going into the car? if so would a ls1 maf with translator fix this?

also I am seeing 5.3 knock retard. I did not have this before.

Thanks steve from Minnesota

mods are
Kirban, fuel pressure regulator
CAS V4 intercooler
PTE-51 polished
Walbro fuel pump
ATR downpipe
Catback exhaust aerochamber
SMC alky kit
Bruce T. PTS Killer/Street tranny
PTS 9/11 3000 stall
MSD 50 injectors
Eaton posi
Boost controller BSTC
Scanmaster
Cold air intake "big mouth"
PT51 turbo about 5K miles
ATR 1 3/8 sway bar
Belltech 2" drop spindles
B&M tranny cooler
Power plate

BOOST AT 23
FUEL PRESSURE 45
The chip is a Joe Lubrant from PTE, Precision Turbo and Engine. Timing is set at a modest 20

 

[ijames]

On these cars the maf was just about pegged at wot, stock. Any mods and you are pretty much guarranteed to be flowing more air than the maf can handle. Chipmakers basically guess how much fuel to squirt based on how much airflow they think you will have, based on your combination and boost level. It is up to you to make sure the air/fuel ratio doesn't get too far off. Cold weather means dense air so you will lean out if you don't turn the boost down or turn the fuel up. You saw that with the lower O2's, and got lean enough to get some knock. You basically have to keep the tune turned down and rich enough so you will be safe through any weather changes you have, or keep an eye on the tune and tweak it up as needed if you want to go faster.

While some have gone 9's on the stock ecm, this "guessing" on the fuel works well in the 12's, okay in the 11's, but somewhere in the 10's starts to get a little too much for most people so they change to a speed density system (aftermarket ecm, ME-R, or Translator Pro). The other option is a translator and lt1 or ls1 maf and extender or extender extreme chip, which will keep the airflow on scale and used for fueling well into the 10's.

 

[390STEVE]

Thanks

Thanks for the responce. how high can you go on the fuel pressure?

 

[ijames]

Depends on your fuel pump. The output volume falls as the output pressure rises, so you can reach a point where you raise the base fuel pressure but the wot fuel pressure stops rising. And there is a bypass valve that opens somewhere between 65 and 120 psi depending on pump model and brand. Generally, I think that if you are pushing 50 psi base (engine idling with the vacuum hose on the fuel pressure regulator off) fuel pressure you really should move to bigger injectors. Some would say 45 psi, others 55 psi or more . With 50's and your combination you should be good for 12.2-12.5's on 93 octane (with no alcohol injection adding extra fuel; it takes a lot of fuel to go quick on 93 octane) if you get agressive with your tune, and 11.0's on race gas where you can run leaner. Besides adjusting the fuel pressure you can go with a chip that lets you adjust the fueling, like the translator or a turbotweak or max effort chip.