i got a larger throttle body while waiting for some other mods to arrrive i decided to go ahead an install to see if i notice any acceleration gains.

when adjusting the maf table for the larger bore in the tuner do you divide the new one/ by the old one and times that by 100? so going to from a 65 to a 68 tb would be a 4% increase. Did i do this right?

 

I have one and use one, but I've never heard of modifying in that manner for new TB's. Running different MAF's yes but your volume isn't going to read any different with the bigger TB. It's still the same air, just more of it. The signal needs to remain the same in order to compensate and ensure your fueling stays on par. Someone correct me if I'm wrong. But if you do that, you're tricking the MAF into thinking you're getting the same amount of air you used to when in reality you're getting more so that would make it leaner.

 

pacerSS is on the right track...

what your proposing is to increase the MAF table 4% to compensate for the increased diameter of the TB. this is not correct.

your engine will still require the same amount of fuel for a given air flow. the TB isnt forcing more air in. what it is doing is allowing more air at a lower Throttle percent. so if your pedal is at 15% you may be getting the same flow as your old TB at 16-17%... when at 100% you will be getting more flow then your old TB was capable of giving.

what you need to do to tune for the new TB is go out and get data. use the data to do a new MAF tune and your done.

if fueling was controlled directly by throttle percent then yes you would want to increase fuel... but this is not the case. the car uses air flow to calculate fuel requirements.

 

ohh i thought the Tb was holding more air since it wider and had the removal of hump above the maf sensor.

This might be the reason why im gettin burst knock retard when i go Wot.

So after doing a Maf tune ZZp suggest i go for a 13.0 AFR or around .860 - .880 mv on the narrowband o2.

Do i manually change the all the afr values of 14.7 to 13 or gradually lower the values and do more maf scans?

 

when you see 14.7 that is your idle Air fuel. do not change that. unless it is in Tq management to protect the engine from going lean. when they are saying drop to a 13.0 they are talking about PE. disregard anything from the Narrow band O2. as .860 on one car could be the same as .9 on another.

i forgot that the MAF is built into these TBS for you guys. my DOHC and my soon to be swapped engine have a separate external maf. still the best way to figure out the new MAF settings is to do maf tunes. a 4% increase in diameter prob wont dictate a 4% increase in flow nor a 4% increase in fueling... a few maf tunes and things will be dialed in very nicely.

 

im still having a few problem with the tune every time i start the car in the morning my ltft are around 16 stft are 0 and my idle is around 12-1300 rpms, cruising + or - 5 for both ltft and stft, when slowing down ltft goes to 6 thru 8 and when parking ltft back to 16 but the rpms idle like normal at 900

Any help?

 

Wait at least 3 restarts and 30 min drives for the fuel trims to level off.

 

yeah i been doing that and they still stay like that

 

Hey i was wonder how you guys actually start your scans? do put the key in turn it to the on position start scanning then crank the engine; or do you crank the engine wait 4 or 5 mins to do its loop and then start scanning?