GuitsBoy

iTrader: (4)

Hi all - Ive recently been running around with my MAF unplugged and a z06 VE table in my HPT bin. Im trying to tune my LTFTs / VE. I had no f'ing idea the car would run this well with the MAF unplugged and the SES light glowing in my face. The drivability is definately awesome running SD - atleast compared to what I had imagined. Im just wondering what the pros and cons are to running mafless for good? Is it just my imagination or has my gas mileage gone down over the last few days worth of commutes? Maybe its cause im at different throttle settings trying to hit different cells? I had the spark tables cloned, so i wasnt defaulting to the low octane table. Any comments as to why I should or should not go SD?

Thanks,
-Tony

HumpinSS

iTrader: (1)

I haev seen nothing but pros running MAFless and I dont plan on going back. The car is more responsive and feels peppy all the way around. Mileage prolyl has gone down because of your right foot

WS6snake-eater

Agreed totaly here. My milage actually seems to have gone up considerably. I've almost got it nailed down perfect. Just a few more tweaks and I'll be all done.

GuitsBoy

iTrader: (4)

Well, you guys almost have me sold on speed-density. Just to play the devil's advocate: Surely, there must be some reason car companies use mass-air in the first place. Does it aid in changing elevations? Is it simply more accurate? Is it safer? Does it blend the VE table to make driving smoother? I feel like if I know the reason why the factory went with a MAF, I can weigh the option myself, and then I can decide weather it's worth it or not. If nobody can tell me what the MAF is used for, then I automatically assume the worst and figure that its some completely necessary piece of equipment for all cars except true race cars.

Also, I do not have wideband, and I don't really want to hit a dyno. There are places charging $120 for 3 pulls w/ wideband, and I can see spending a day getting my OLFA down being an expensive proposition. What is my best bet in tuning using only HPTuners, the stock o2s, knock sensors, and a g-tech to measure performance increases. Maybe this throws a wrench in the SD works and I would be better off strapping my MAF back on?

Thanks for all the help guys,
-Tony

HumpinSS

iTrader: (1)

The maf was prolly put there to be more stringgent on Emmsission. That is the only fucntion of our PCM's. Better emmissions management using the MAF. Since most of us are modding our cars and are prolly in violation of some emissions laws I dont see the need to run one if the car runs fine and better without one.

If you dont have a WB you can use tuners and your trims to dial in the ve table. I would raise the PE threshold so you dont skew your results. In doing this be careful not to beat on the car because you will be running an AFR less that ideal for power and the car will detonate. Easy driving hitting as many cells as you can without blipping or stabbing the throttle should get you pretty close. As long as the car doenst go into open loop or PE then your trims will learn and update. This informatioon can then be used to tune the ve table.

GuitsBoy

iTrader: (4)

Thanks HumpinSS... Ive got that pretyty much down. Ive got my WOT TPS% at 80 exept for the high rpms. Ive split my FTC boundaries at 1125, 2250, 4000; so now im using all 16 FTCs for added LTFT accuracy. I really dont want to disable PE altogather via 250 on the ETC. Im pretty sure this is a good effort at tuning my part throttle LTFTs, using only the tools Ive got. How do I go about tuning for PE now? Keep leaning until I start getting some KR? Ive got the gtech so I can measure gains to juggle a happy medium between leaning out and advancing timing, before KR rears its ugly head. Any other pointers? Im using the stock z06 VE table modified on the left hand side for my trims, but the right hand side is still as it was.

HumpinSS

iTrader: (1)

The reason you disable pe is because the trims stop learning. PE is divided by 14.7 AFR so 14.7/1.13=13:1 AFR. IF YOUR VE table is correctly dialed in and you set your PE table to 1.13 you will automatically command 13.0:1 or close to it. Disabling the PE allows no outside influences and allows you to hit many cells before you trims lock to 0 and stop learning. Once the ve table is dialed in you wont have to worry about PE because you will know what it is allready. Thus not having to tune from your KR sensors

GuitsBoy

iTrader: (4)

Okay, I know what you mean by this. I however dont want to be at 90% throttle at 5600 RPMs and running a 14.7 a:f Thats why I left PE at 80% TPA so that I could populate the vast majority of my LTFT histogram with useful data. I just didnt want to disable it all the way. If I really NEED to disable it completely, ill do that then.

Also, some people still use the PE table while others set it to 1.00 and use the OLFA table. Which is the recommended method?

Thanks,
-T

HumpinSS

iTrader: (1)

The pe table is way more straig forward than the open loop fa table since that table is indexed by ECT. doesnt matter the PCM picks the riches value of the two and uses that in PE mode and when not in pe mode it uses the Open Loop F/A table.

P Mack

iTrader: (6)

There are 3 advantages of the maf that I can think of. One is for people who mod their cars without tuning, the maf will sense the increased airflow, but the ve table will not be accurate anymore. That is true for mods like intakes, heads, cam, but not so much for anything before the intake like a lid. Also you need a maf if you're running a dry nitrous kit. The other reason is for forced induction, if you're running any boost at all it will max out the map sensor, but it doesn't matter cause the MAF can read the increased flow (until it gets maxed out too).

About the PE thing, i think it would be cool if you could set the fuel trim histograms to ignore the open loop ftc's. Anyone reading this?

jimmyblue

iTrader: (11)

What is it about a dry shot that requires the MAF? Just
how whacked the IAT is (throwing off the SD calcs)?
If you had an IAT that was telling you the truth (like
potted into the intake mouth) do you suppose you
could get a good tune then?

Another_User

I was thinking about this. I have been pondering drilling a hole for the IAT in my MAF delete tube. Sweet.

P Mack

iTrader: (6)

It's because a dry shot does not have a fuel solenoid to supply the extra fuel need for the nitrous. The MAF has to "read" the nitrous as air and supply the extra fuel through the existing fuel system. You could go mafless with a wet shot but not with a dryshot.

GuitsBoy

iTrader: (4)

I was gonna say, I know the IAT can tweak timing advance, but I dont think it changes anything that would add more fuel. Because of the way the MAF sensors work, the cold nitrous makes the MAF read more (denser) airmass is coming in. All the IAT would do is bump up the timing due to the cooler temperatures, and thats not even a good thing... Now I dont think that nitrous should affect the MAP sensor, so the burden of telling the ecm to add fuel is on the MAF alone.

JS

iTrader: (4)

What about weather conditions in SD....
Wont the A/F go off in low or high temps once you've tuned it at a certain temp.

A Fast or a Gen VII has the ability to run SD via WB correction.
What are u guys using for that,the iat/map,IMO thats a junk way to tune.

If the Factory pcm had a WB then SD would be fine but it doesnt and relying on other sensors when the weather changes is stupid.I've talked to a few tuners and they told me unless your using a correcting WB to change the A/F then your better off with CL tuning.

P Mack

iTrader: (6)

Right, the maf works on temperature and nitrous is cold.

P Mack

iTrader: (6)

Theoretically no. The pcm uses ve to get volume flow. It uses temperature (IAT) and pressure (MAP) to get density. Density times volume flow equals massflow. So any changes in temperature would be accounted for in the density calculation.

JS

iTrader: (4)

It doesnt work well bro...
Talk to few tuners (EMIC) that really know the powertrain system in our cars.
U need a true A/F adjusting WB to do what your saying correctly.

I dont buy it.....
I had SD tuning,horrible A/F at idle,stalled and the idle rolled to much and lets not even talk about gas mileage.

NicD

iTrader: (7)

Then it wasn't done properly.

JS

iTrader: (4)

I think I understand now,I'm sorry it looks like u guys are pretty sharp.
You guys are taking the time to get the VE tables correct,logging alot of info and then once your tuned in your letting the equation of Density times volume flow to get the A/F corrected via the IAT/MAP.

Okay I can agree with that...
I'm so use to the old maf-less junk back in the 80's and didnt realize this pcm is much faster/smarter.

Maybe I'll try tuning this way down the road.
Whats the biggest advantage to SD if u dont mind ansering guys?

One thing though,if I get the Ltrims done correctlt via closed loop using my WB Then how will that effect my open Wot tuning.IMO It cant because I've got the ltrims done right,or am I wrong in my assumptions here too?