hodge9386

What would cause my maf to be unstable at wot like this? I am trying to dial in my wot and it is OK but I think my maf is causing it to fluctuate more than it should. I run a 85mm truck maf connected to the filter of my hurricane intake. Is it because the big cam/fast 102 or because it's to close to the filter? Do you thing it would help moving it more towards the throttle body?

jglassmaker

I have a similar issue with mine, but doesn't seem as consistent as yours. I've heard a few fixes are:
MAF cleaning
MAF was "de-screened" - get it back to stock form
MAF is bad - replace

I am going to personally try cleaning it tonight and also see if mine was "de-screened".

hodge9386

I cleaned the maf not to long ago when i put the new filter on. the car dosent get driven to much.
Its a 85mm truck maf and im pretty sure it still has the screen

RonSSNova

Looks normal to me.

tblu92

Larger than stock MAF's don't really mean more HP or more airflow-----The MAF sensor is strictly a sensor that measures airflow-----A stock MAF from 97-2006 is plenty capable of reading airflow up to apprx 500 crank HP After 07 the newer MAF's can handle more up to maybe 600 crank HP-------
So there is no advantage to using a larger than stock MAF unless you have boost and exceed those limits----PLUS the larger ones make it a bitch to tune P/T fuel
Also GM calibrated the stock MAF to read correctly only in the stock location from the T-Body Moving it closer or further away will only add in making it read in correctly
Yes a tuner can recalibrate your MAF to work correctly but NOT on a dyno it takes hours and hours of P/T driving to scale a large MAF as the MAF readings at P/T also greatly affect the WOT fueling as well
It is not uncommon for the MAF readings even if stock to spike very high from a dead stop---- but only briefly-----If your readings are showing very high spikes then your MAF is reading wrong-----Put the STOCK maf back on---try to get it as close to the stock location as possible---
Tell me more about your mods and apprx HP level

hodge9386

99 corvette with ls1 returnless fuel system
tick performance sns tq max stage 3 cam 235/243 .630"/.610" LSA111+2
fast 102 intake
ls2 ported tb
ls2 injectors
lightly hand ported 243 heads, no mill
long tubes/full exhaust
85mm truck maf
hurricane intake

I thought it might be injector data related but I have verified the data. I'm not 100% sure it's the maf causing my wot afrs to be unstable, they fluctuate about +/- .4 at wot which seems a lot to me. I know they won't stay a steady 12.8 but I would thing them being +/- .2 or so is not to much to ask for. I am also having issues over shooting the target afr using the copy afr error, x % 1/2 method. I may have to manually do it to keep it from over shooting the target. I do a log now and my afrs will be slightly rich (6-8%) and I make a correction, hand smooth and they will go slightly lean. It just goes back and forth between lean and rich and not finding the middle ground. I am very close to just saying screw it and calling vengance and setting up a tune appointment.

tblu92

I hope you are using a wideband to determine actual AFR and not using COMMANDED AFR from a data logger---- this is the only way to exactly read your WOT AFR --- and also remember you cannot read AFR's even with a wideband until the trans is in a ratio of 1:1 on an auto trans this is 3rd gear reading AFR's in 1st or 2nd gear will always read richer as the engine is not under full load

Finally you say the % shows +/- at WOT Do you mean the fuel trims are reading +/- 4 % ?? or where are you getting these numbers ?
If they are from your fuel trims It is slightly complicated---WOT fuel trims will lock on only a positive fuel trim---a negative fuel trim will always lock on "0" A positive fuel trim does not come from WOT but is carried over from fuel trims "Just Before Going To WOT"
so to clean up fuel trims at WOT that are positive you need to make a + correction in % in your MAF table in the area where you just before going to WOT-----Typically this can be as low as 4000 HZ on your MAF table

hodge9386

yes i am using a wideband connected to hp tuner. I cant really do a 4th gear wot pull because i would be going 150 on the street and i dont want to do that. i know it is best to use 4th to get a nice long pull and collect a lot of more accurate data but its not reasonable for me so i do wot pulls in 3rd from around 2500 to 6500 rpm which is still putting me going 120 on the street but its what i got to work with.

Im not saying +/- 4% i saying the wideband fluctuates from +/- .4 from my commanded 12.8 at wot. i know it wont read perfect 12.8 through a entire pull but if i could to get it to read around 12.7-12.9 i would be happy. They are not from fuel trims, i run ol the entire time im tuning and when im done i turn stfts back on and leave ltfts off so there is nothing carrying over to pe. my stfts are all within 3% anyway.

I noticed my wb doing some crazy stuff last night that there was no way was actually happening so im pretty sure the sensor is going out which might have been contributing to the erratic behavior.

you can see here my wb is all over the place and i have some funky stuff going on that is honestly kicking my ***. you can see where i go wot that it is still fluctuating a little. i expect there to be some fluctuations when in closed loop because the 02s are switching but his seems a little much.

hodge9386

thats honestly a bad example of what i got going on i was doing some transient fuel and 02 stuff here and it was all jacked up. this log is a better example of what i have going on.

hodge9386

and yes i know idle is lean. i run ol idle and the wb is reading a little leaner than it actually is, it is actually around 16.5 at idle or at least it should be lol

CTD

I'm still struggling with new HPT software I don't see your WB in the log.

I have been waiting for you to post a screen shot of that as well Dynamic Airflow. Your log does show that airflow in the channels & it is very stable. Others have said the MAF looks normal & I have to agree.

You may want to try adding some additional fuel in the peak torque area for giggles, need to see the WB.

There was a comment in the other thread about watching injector pulse width, it's following dynamic nicely.

hodge9386

post 8 wb is a the bottom. it should also be in the log i posted but i dont know if you will be able to see it because you dont have my math or config.

enoniam

Your MAF and WB look pretty normal to me as well. I usually log Dynamic Air as well as the MAF calculated output because it seems the Dynamic Air is a filtered version of the MAF at higher rpms and shows much smoother.

I don't recommend running with LTFTs turned off outside of doing tuning data logs. My car was tuned that way when I bought it 2 years ago - that was one of the first of many things that I've fixed on it since then.