doing some datalogging today notice how its seriously wot 102% (ok so i probably need to adjust max volts parameter by .1 or whatever) but im not in my highest vacuum column. my foot was certainly pushed to the floor. it becomes rather annoying as around 6000 rpm it will switch over and start reading a different column. is this indicative of a problem with my setup.

 

What is your engine setup, intake & exhaust included?
A little bit of background information would be very helpful.

940mbar (2inHg) is pretty close to atmosphere (1013.25 @ sea level) When you are still pulling vacuum at WOT that generally means that you have a restriction in your intake tract. At 940mbar that could be something as small as the length of your intake tube or the your air filter.

I'm not sure what you are talking about when you refer to it shifting columns. The columns are RPM and vacuum based... it will only change columns if the RPM or vacuum signals change. Are you talking about the maps switching over to the high cam map from the low cam map?

 

I believe if your vacuum increases with rpms you have a restriction somewhere.. Also elevation will play a role in your wot vacuum.. If hes at 2" at 3k rpms and 4" at 8k rpms i can see the ecu shifting columns..

 

hi, by shifting columns i was referring tothe map reading from the far right column with the .6" heading.

81.5x89mm lsvtec
p30 pistons c/r right about 12:1
b16 head
itr cams and valvesprings with brian crower steel retainers
3" shortram with bpi vstack
60mm tb on a portmatched p30 intake mani
old edelbrock 4-2-1 with 2.5" collector
2.25" exhaust with magnaflow cat and straight through muffler
gsr tranny with ls 5th

running 93 pump gas

i set the motor up to have good midrange and make peak power around 7000rpm not up like 8000rpm since its a daily that i put 60-80 miles on every day .
it has around 6000 miles on it, compression is 230-235 and leakdown is 10% but it seems all my motors throw out about 10% leakdown

 

Maybe an old map sensor? Wiring to sensor?

 

Do you reach 0psi (atm) at lower rpm? If you do then this would indicate an intake restriction. Its very easy to spot on a NA motor as you will see manifold pressure taper off as rpm increases at WOT.

 

Key On, engine off...what is your MAP reading?

If less than zero...

Barometric pressure low
Altitude high
Bad Map Sensor settings

 

You'll notice your atmospheric pressure (PA in the list) reading is 0.6 inHG. Your MAP sensor should read the same (Or extremely close) with key on engine off. If it does the reading is more than likely accurate.

 

yes, absolutely. it jumps over in the mid to upper 6000 rpm range.

i have a skunk2 pro series intake manifold sitting in a box somewhere around the house, but i wanted to use the p30 manifold. i had found a fair amount of information with similar motor setups making good torque and very comparable power (at least up till around 7000-7500 rpm) using the p30 vs like an itr style.

even if i swap over manifolds, i only have a stock throttle body still...

 

off the cuff i believe it reads .2" key on engine off

 

well i put the sk2 pro series manifold on yesterday and then went for a ride with the laptop. bad news its still doing it, but honestly its not consistent so some runs it stays off the .6 and 1" column, other times it dips over to the 1" and 2.5".

good news is that i did catch a few rainbow trout making a quick stop at a creek while on my tuning adventure

 

1.8... 1.5... Seems pretty repeatable. It's not going to just go away. That is how your engine setup is breathing. It will vary slightly based on the day to day atmospheric pressure.

 

yeah it runs great and has no problem getting out of its own way. i have dyno time coming up soon and i just wanted to make sure ive got everything up to par

 

Appears fine, so good luck at the dyno!

 

Again, you can tweak your map sensor settings to match your Baro reading. Or try a different map sensor.

Heck, it could just be a wiring issue...measure what your supply voltage and ground are sitting at, could just be skewed based on where your main engine ground is located.

 

Map sensor voltage can be higher with bad or corroded grounds, especially at higher RPM. Just to be on the safe side you might want to clean off your thermostat ground, in case it's corroded it may get worse over time and throw off your tune.