maft GEN2 tuning questions

TurboStreetCar

TurboStreetCar

Formerly Nosechunks
Feb 25, 2006
2,778
13
38
Long Island, Ny
hey guys i have a question, i just recieved my maft gen2 and i was driing and trying to tune a little to get rid of fuel cut and ecause my air fuels are at about 10.5 via my zeitronix. so i go out and i take about 5% out of around 4krpm and up, and it doesnt change much on my zeitronix. so i take some more and i see it start to make a change. when i actually start noticing a actual change of more then .2 AFR, i end up at about 20% from 4600 and up. i thinkin that that is way too much to be able to take out on a stock AFM stock injectors and stock fuel pump and not make a 1-2AFR change.

can the computer learn a fuel curve and correct in open loop? or am i doing something wrong. i seems that its hit and miss with the air fuels, ill make one run and itll be around mid 11's and ill be like sick, and without changing a thing make another run and its back to low 11's high 10's

i did notice though if i maybe 3/4 throttle it, itll run at around mid 12's but if i full it goes down to around 11 flat.

anyone got any input on this?
 
TurboStreetCar

TurboStreetCar

Formerly Nosechunks
Feb 25, 2006
2,778
13
38
Long Island, Ny
nah thers 3 load levels, low medium and high, theres a calculated load that u can set how its calculated, u can have it calculated by throttle position, afm/rpm or a map sensor. i have it set for AFM/RPM and the points are preset but adjustable. i drove my car while looking at the unit untill i was bosting up but not full throttle, i was around 170 load, so i put the high point there.

im adjusting the high table and i kno im adjusting the right RPM points, i just think something is wrong because taking out 20% fuel HAS to make a BIG diffrence in aif fuel.
 
TurboStreetCar

TurboStreetCar

Formerly Nosechunks
Feb 25, 2006
2,778
13
38
Long Island, Ny
yea i hook it up all good, soldered all connections. i kno its hooked up right because i was fooling around with the frequency max output settings the other night while i was driving and went i turned it off and it went to 50 the engine ran funny and my wideband went to like 16:1 cause it cut the frequency of the AFM from like 75 to 50. so i kno it CAN alter the air flow signal. also i adjusted the main scale 5 % while i was idiling and looked at the HZ in and HZ out side by side on the sensor monitor and saw a diffrence to make sure it was working. that was before i was playing with the frequency limiter.

i havnt looked at the VF but i thought that in open loop it didnt have any correction?

also my AFM took a shit today, its been cutting out when it rains so i guess it was on its way out. so i cant run the car untill i get my 3.5 inch GM maf that i ordered today. guess ill just have to wait and see what happens.

under the AUX input for the map sensor it has a 2 bar input and since im not running over 10 lbs, can i hook the stock boost sensor up to the maft unit and use it to calculate load? or would the scaling not be right?
 
TurboStreetCar

TurboStreetCar

Formerly Nosechunks
Feb 25, 2006
2,778
13
38
Long Island, Ny
ooohhhhhhhhhh so if the load level for the high range is just to low and is sometimes applied when in closed loop itll throw off the open loop mixture aswell. that would explain it, because id tune it and it would run mint and id make another run without touching anything and it would be back to where it was. so to change open loop mixture without the TCCS correcting, i will have to make sure it only tunes in open loop, and if i ONLY tune in open loop it wont corect for it. right?

thanks Drj

im gona have to try out setting the load points diffrently, maybe ill run it off the TPS and with the car not running monitor load as i push the pedal down and a little before WOT ill set for the high load. that way i kno it wont be applied for closed loop.
 
TurboStreetCar

TurboStreetCar

Formerly Nosechunks
Feb 25, 2006
2,778
13
38
Long Island, Ny
ok so i got an old GM 3 inch maf in the mean time while im waiting for my 3.5 inch gm maf. i hooked everything up and i went into the configuration screen and i chose LT1 3in becaue it was the only 3 inch GM selection that i knew of. i knew it wasnt off an LT1 but i figured id give it a whirl. turns out it wasnt that close at all on the scaling and i had to go into the MAF scaling adjustment and subtract about 30% above 64g/sec. finally i got the VF to be in the 3volt range consistently and if not on the 1.5 volt side, id rather the computer be subtracting fuel then adding.

i then started carfully adjusting the low, med and high tune's untill i was running really good. its running mint now, high 11:1's across the board. but im still having a couple problems.

the tip in off idle, and ONLY off idle is very harsh. goes to about 19;1 and almost feels like its gona stall then abruptly comes back. it only does this off idle, if i am the slightest bit off the idle stop and i crack the throttle quick it just accelerates.

number 2, in 1st and sometimes second (automatic) when i accelerate its like the maf cuts out, almost like fuel cut but to fast to be fuel cut. its like a rappid occurance of fuel cut maybe 3-5 times in the time fuel cut usually hits once, its more like a rev limiter then fuel cut, but its at like 2500 and only in low gears. it happens intermittenly and isnt only at full throttle. i tihnk it might just be a bad connection somewhere so im not to worried, im gona go over it tomarro.

number 3 and finally, on deceleration or just under cruising throttle, like slowing down without braking to a light thats about to change to green, the mixture goes either very lean or very rich. i tried setting the maf min and maf min tps and the rpm maf setting to get it to stop but it doesnt seem to want to stop. also if i free rev to 1500 rpm and hold for a second or so and let off, the mixture will go down to 12:1 and then rise up to about 17-18:1 and hang out for about 2-5 seconds and slowly come down to 15-14.5:1. at the time that its running the 18:1 the frequenct out to the computer from the GEN2 is ~25 and remains 25 when it comes back down to 14.5 15:1, and the rpm is constant at a 650-700 rpm idle.

sorry for the long post, im just trying to describe it the best i can.

also i reset my computer before starting the car with the gm maf so i also think it might take a day or so for it to fully learn the tip in and decel fuel map. i will also chekc and make sure there are no engine codes tomarro.

DrJ, u were right on about getting the VF signal satasfied. thankyou so much.

-Dan
 
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TurboStreetCar

TurboStreetCar

Formerly Nosechunks
Feb 25, 2006
2,778
13
38
Long Island, Ny
also the 3.5 inch maf i bought is off of a 2000 chevy express (G van, GM part # is 25008308, ac delco#213-252), is that maf programed into the gen2? or am i gona have to program it again like i did for the 3 inch one i have now?
 
T

turbobob

New Member
Aug 15, 2005
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Near Detroit
set the unit for "LS1 aluminum".

Load AF/RPM attempts to calculate MAP. So 100 is about zero psi.

The tuning is interpolated between the load levels. so set your high load point below your max load. Like half way from 100 to max load (135?)

Bob
 
TurboStreetCar

TurboStreetCar

Formerly Nosechunks
Feb 25, 2006
2,778
13
38
Long Island, Ny
well i tried the LS1 aluminum and it was still not workin with this maf, unless u mean for the 3.5 inch i ordered? i have no idea what this maf is out of and theres no good gm or acdelco numbers on it (i work at a chevy dealership) but the one i ordered looks to possibly be a LT1 3.5inch.

i have the load calc, set to TPS and at full throttle its about 223 load, the load points are 45, 100, and 200, i set the high point really high because i wanted to have no chance of tuning in closed loop. the points are all working good and the tuning is good, the only problems im having are at idle and just off idle.

The tip in off of idle is the only real problem im having, i played with the MAF limit and maf tps points and i got it to respond how i wanted, it doesnt bog out after i gently let off anymore. any ideans on how to richen up idle tip in?

Thanks for the help guys.
 
T

turbobob

New Member
Aug 15, 2005
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Near Detroit
as far as I have found, all 3" MAFS are the same. 3" LT1/Impala is the same MAF as on my son's Lumina and my wife's old minivan....

the 3.5" LS1 Aluminum is the one you ordered.

Bob
 
TurboStreetCar

TurboStreetCar

Formerly Nosechunks
Feb 25, 2006
2,778
13
38
Long Island, Ny
alrighty sweet, i tried putting the one i have now on ls1 aluminum cause i was unsure if thats what u ment and it wasnt working right, it was good at idle but as soon as the rpms went up the scales were way off. i just put it back how i had it.

im still having a problem with coming off idle, the little hesitation. would the idle switch in the TPS have anything to do with it? maybe bypass it?
 
S

Spiv

hooligan
Mar 31, 2005
88
0
0
44
Orlando, Fl
It does sound like the off-idle tps switch, maybe it's not working right? Maybe you did something to the wire for it while installing the genII?

Very curious about this, I was having this problem a little while ago on the stock system. Got it working right, but i'm about to go to the genII myself. don't want to see any of those problems again, it drove me crazy.
 
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