MAF Output Choppy
Thread Starter
Joined: Nov 2001
Posts: 5,649
Likes: 9
From: Warr Acres, OK
MAF Output Choppy The car is a 02 T/A with a p1sc 6 psi procharger and mac headers/ory. That's pretty much it for engine mods. Still using the stock cam and springs. It's making 489hp/463tq sae. Was wondering if the stock valve springs could have something to do with the choppy MAF output up high. I realize they are never perfectly smooth, but this one seems to be pretty bad. I'm thinking maybe valves bouncing on the seats a little when they close. If not the stock valve springs causing this, what could be some other possibilities? The car runs good though.
Launching!
Joined: Oct 2002
Posts: 256
Likes: 0
From: Tulsa, OK/Gainesville, Fl
There is a guy in my car club who just dynoed similar numbers with similar mods as you. (he posts on here as well) I believe he is also having a floating valve problem. I did when i first went turbo and I switched to some CC 918s pretty quickly and it helped a ton.
Completely normal, different MAF, different logging program, 9psi on a stock motor with 918 valve springs - 10.90 @ 126mph full weight so it ran OK 
You can change the springs and it may help on the top end power a little but it wont get rid of the jagged MAF line.
You can change the springs and it may help on the top end power a little but it wont get rid of the jagged MAF line.
Thread Starter
Joined: Nov 2001
Posts: 5,649
Likes: 9
From: Warr Acres, OK
Originally Posted by vhgjk123
There is a guy in my car club who just dynoed similar numbers with similar mods as you. (he posts on here as well) I believe he is also having a floating valve problem. I did when i first went turbo and I switched to some CC 918s pretty quickly and it helped a ton.
kp, this car is a lot worse than I'm used to seeing. Just looking for a cause and why the A/F oscillates from 11.0 to 11.5 from 4700 rpm on up when I'm commanding the same value in the PE table. I didn't see this oscillation before MAC headers were installed, but the wide band was in the cutout in the I pipe before the headers and this time it was put in a bung in one leg of the Y pipe.
Originally Posted by 2xLS1
That's the car I'm posting about.
kp, this car is a lot worse than I'm used to seeing. Just looking for a cause and why the A/F oscillates from 11.0 to 11.5 from 4700 rpm on up when I'm commanding the same value in the PE table. I didn't see this oscillation before MAC headers were installed, but the wide band was in the cutout in the I pipe before the headers and this time it was put in a bung in one leg of the Y pipe.
kp, this car is a lot worse than I'm used to seeing. Just looking for a cause and why the A/F oscillates from 11.0 to 11.5 from 4700 rpm on up when I'm commanding the same value in the PE table. I didn't see this oscillation before MAC headers were installed, but the wide band was in the cutout in the I pipe before the headers and this time it was put in a bung in one leg of the Y pipe.
I believe the PCM 'smooths' the MAF signal to a certain degree, at least thats what I was told. The ATI plenum is whats causing the peaks and valleys, lot of bad juju going on in that thing but in the long run it wont affect anything much.
FWIW My LC1 logs in the HPT input were very jagged, the flashscan is very smooth so there is some extra filtering going on with the EFIlive external input it appears as well.
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Originally Posted by 2xLS1
I'm takling about the dyno wideband and how Winpep 7 plots it.
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