Cylinder Airmass PID for Speed density LSJ?

[darthchicken]

Anybody have one? Everything I've found keeps referencing back to MAF, and I don't have a MAF sensor anymore (just using it for AIT, its not in the airflow).

Yes, I searched.. found nothing

[Leafy]

You'll have to make a custom one, one which uses PV=nRT and stuff. How are you controlling spark? The stock LSJ computer uses the MAF sensor to control spark.

[darthchicken]

No, it uses cylinder airmass to control spark. And I know that if maf is disabled it uses somthing else other than maf to calculate cylinder air. What I'm not entirely sure of, is what that other is. Is it ve? So would the new calculation for a 4 cylinder car be "ve*30/rpm"? Ie replace maf airflow numbers directly with ve numbers? That sounds too simple

[laser_racer]

The maf sensor has your iat1 sensor on it and that will mess with timing and fueling. You really need to keep the maf to keep everything working correct.

[darthchicken]

Yes I know, that's why I have it zip tied inside the engine bay near the air intake.

[laser_racer]

Thats not how that works it measure the temp of the incoming air. Why did you not put it back in the intake?

[Leafy]

What's funny is that if you are actually making enough power for this no maf thing to be necessary you's already be running a stand alone because a grand for the new aem unit is pocket change to your 1200 hp build.

Just fucking get a bigger maf and the scale the maf tables if you're making under 900-1200hp.

[darthchicken]

Not sure what all the hating is about - its a simple question.. or maybe it isn't. Maybe there are a lot of kids coming here and asking stupid "what if" questions..." its probably because of my post count or something.. maybe I should go post random useless stuff like "What's funny is that if you are actually making enough power for this no maf thing to be necessary you's already be running a stand alone because a grand for the new aem unit is pocket change to your 1200 hp build.

Just fucking get a bigger maf and the scale the maf tables if you're making under 900-1200hp" to bump my post count

The MAF sensor measures AIT1. That IS air temp. Whether or not its on the inside of the filter in the tube, or zip tied off to the side doesn't matter, AIT1 is AIT1.

I'm running an EFR6758 turbo, with plans to run at 25psi on my Ariel Atom with Ecotec engine. With a custom 3" inner diameter MAF tube, I'm hitting 9400hz.. at 15psi. That won't work obviously. Over the weekend, I installed a LS2 MAF, and what do you know, it actually reads HIGHER than the custom 3" with the cobalt MAF sensor (10,100hz). Must be something with the way it converts to hz... all I know is that it reads higher. There is probably some converter do-hicky I need to buy that I haven't figured out yet.

There isn't a lot of room on this car. Here is the LS2 MAF installed on the car, as you can see, I barely have enough room to make it all fit.



MAF isn't going to work in this setup unless somebody can convince me of something otherwise. It's just to much air through this turbo. A standalone is not an option, not at this time. If it was, I wouln't be here, I'd be on the AEM or Motec forum.

[Leafy]

Ok so. Basically you need a maf to run this pcm. Bam done end of story. The cylinder air mass that the pcm uses for spark control is only taken from the maf sensor (well 90% taken from the maf). It has a backup speed density table for limp home mode if the maf dies that hpt cant get to (and I fucking hate it when people tune these cars on that spark map with the maf un plugged). How much power are you making anyways, I'm not too familiar with borg warner turbos. I know that ZZP is making over 900 hp on the dyno with the stock lsj computer so asking them may be a good start.

But still I did answer how to get cylinder air mass from the map sensor, and it required you to do some reading because frankly I dont feel like having to go look it up for the 20th time again. You literally have to do the speed density calculations out. Its your lucky day, I found the link, guess I saved it. http://marcintology.com/tuning/HowSp...ityWorks16.doc Digest all that and then make a custom pid.

[darthchicken]

Thank you Leafy, I'll keep that doc (just scanning through it, it looks like I need to re-read it about a dozen times to absorb the information in it). I appreciate the help!

In the meantime, since I've got the LS2 MAF on the car, I'll leave it there, and disable my MAF. I assume the MAF will still read hz when its "there" but disabled (maf max set to 0), and that it will continue to figure out g/cyl properly?

The goal is "only" 400whp, but as I said, the issue on the MAF is packaging size. My MAF sensor can only really fit one place, and its very close to the filter. With the 3" MAF, a slight breeze would change the idle, and eventually kill the car. I tried putting a screen on the intake, and that helped out a lot, but still, when you're talking about a MAF sensor 2" from the great outdoors, things go south pretty quickly. The larger the MAF tube, the worse it gets, and from what I'm seeing, I'd need a 3.5" MAF tube with the stock cobalt sensor to make it work without overflowing the 11.1k hz table limit. And there is no room for a MAF sensor in the boost tube, post intercooler... again, packaging concerns.

[Leafy]

Thats weird. For only 400 you should be able to do it on a 3 inch. Hmm what might help would be using some of that aluminum honey comb. They use it as screening in some stock mafs. But buy it a few inches thick and fill the area between the filter and the sensor with it, even extend it into the filter if the filter is large enough, you basically need to make the flow as close to laminar as possible entering the sensor cross section. Even if its turbulent as long as its mass flow direction is parallel to the axis of the sensor tube you should be fine. Its when you have a weird flow direction in there, like the wind blowing across the filter that it read really weird shit. You can also cheat on the stock maf and put an extra voltage source across the hot wire sensor (the reverse of the resistor trick some maf companies use to allow you to use a bigger maf on the stock tune). That would make it read a lower frequency for the same airflow, but it would require some 20 dollars of circuitry that I cant for the life of me remember how to create, I know it needs an amperage control and that's about all I can remember.

Pro tip. You changed me for being a douche to being helpful by having a car that doesnt suck.

[Chris@HPTuners]

the VE table controls the cylinder airmass when the MAF is disconnected.

you cannot log the cylinder airmass directly, but you can log the VE Airflow and then create a custom PID to convert this airflow to cylinder airmass.

The equation is:

airmass(g/cyl) = airflow(g/sec) / (RPM / 60) / (numcyls / 2)

or for a 4 cyl engine:

airmass = airflow * 30 / RPM

Chris...

[Dennisscars]

Shhhh.... Don't tell my car because it has had the MAF depinned for 50+ track days using only the IAT1 sensor running VE only with 1000cc ID injectors.

[darthchicken]

the VE table controls the cylinder airmass when the MAF is disconnected.

you cannot log the cylinder airmass directly, but you can log the VE Airflow and then create a custom PID to convert this airflow to cylinder airmass.

The equation is:

airmass(g/cyl) = airflow(g/sec) / (RPM / 60) / (numcyls / 2)

or for a 4 cyl engine:

airmass = airflow * 30 / RPM

Chris...

Thank you Chris, that is what I posted back in post #3, nice to have it confirmed!

[omega_5]

You Ariel Atom guys are a bit strange sometimes.
It baffles me how we can make 500+hp with the stock PCM and all the stock sensors, and you guys have trouble even hitting 400hp.
Are you you guys using a 3" ID blow-though tube?

But for the record... no, the car doesn't need the MAF to run, only the IAT1 sensor. The entire system is designed to fall back on to the VE tables if the MAF ever fails, or is removed.

[darthchicken]

There's no room for a blow through tube.. and a big part of the problem IMO is the exhaust. Everything is just crammed into a tiny space, and there isn't enough room for much of anything.

The great news, is that at 300whp it'll beat just about anything out there and is scary as hell to drive on the street, at 400whp I'll be bringing a change of underwear with me anyplace I go, LOL

[HAWAIIZUKA]

I know this is old thread, but I'm on the same boat now.
I made custom PID for my Camaro. it looks okay 98% same under MAF limit. but when I raised boost to 7-9 start showing little differences.
so using this equation, airmass(g/cyl) = airflow(g/sec) / (RPM / 60) / (numcyls / 2)
looks like this?? can anyone confirm?? it is working and looks okay...
[PID.2311.MET] /([SENS.70]/60)/([HPT.NUM_CYL]/2)