MAF and SD

[emdub27]

In a 2 bar sd tune is it possible to leave the maf fail frequency at 11500hz so that the maf will function until it maxes out. And then be ignored once it maxes out so that the computer will operate in SD. If Anyone cares to know it's an 04 silverado ss. LQ9 364cid, Vortech T trim at 10# with BOV, 60# delphi injectors at 60psi, stock ported maf and tb. NX fogger 50 wet shot used for cooling because IATs max out. Full longtube headers and custom dual 3" exhaust with cutouts and magnaflow. 255lph walbro with magnavolt.

Just looking to get the most driveability possible, currently running 11.9's without the nitrous with crappy 1 bar tune fudging after 5000rpm. This is about the upper limit on the bottom end so a custom 408 is in the works, that will be able to withstand 15# boost with a 250 shot.

[Russ K]

The maf will be used unless the fail freq is changed to 0. Only then will the truck be in SD mode.

Russ Kemp

[emdub27]

I don't want to run in sd all of the time, believe it or not this is truck is regularly street driven 3-4 days a week. what I am asking is if I leave the maf fail frequency at 11500hz, will the truck go into speed density after the maf exceds 11500hz. and utilize the maf below 11500hz

[Russ K]

Why don't you want to be in SD all the time? My car has been mafless for over 2 years. The 2 bar SD OS is designed for SD operation only, so you must set the maf fail freq to 0 in order to be in SD mode. If your maf is functioning and the airflow exceeds 11500 hz, then that will set code P0103 and then you should be in SD. Sounds like odd way of tuning a 2 bar SD set up.

Russ Kemp

[emdub27]

let me clarify. The truck will always be raced/ pounded on in an SD only tune. It currently has a SD tune and runs completely fine where it was tuned. About 2000ft and about 80*f. But we want this to stay a driver and since we live in CA it needs to be able to work well from sea level to 10,000ft and from about 40* to about 100*. Thats my problem, I can get a damn good sd tune for one location and temperature. The AFR varies to much at others. At my house which is about 5 miles from my track I have it dead on at 11.4. This last summer I was seeing AFRs in the 15's and 16's driving at sea level at about 95*, not pretty.

[Russ K]

What will happen after P0103 is set, yes you will be in SD, but that code will remain current until the engine is turned off, then restarted. So the truck will be in SD mode while code P0103 is current. A proper SD tune's AFR will be right no matter what the altitude or temp. I drive my car through mountains (up to 6600 feet), down to sea level, then back home (1800 feet)

Russ Kemp

[speedyss]

how can the sd tune remain the same with the change in temp and alt. I have a problem runing sd for day to night i have to have 2 tunes to make it run right, it runs richer at night, i thought this was due to the IAT but then i put a potentiometer on it and left it at 60*f where it ran best at night but when i put the IAT there during the day it still ran like crap, i dont know what other sensors the ect is read to know the diff between day and night other then temp?

[buldogg]

I have the same question I started a new post and didnt know about this one. Please someone give us a definite answer. It wouldnt matter if the p0103 code was in the computer if you are racing it would reset its self every time you turned your car off. so this kinda sounds like a solution. I too am having problems with mine being dead on during the day at 70 degrees then at night and in the morning I am way rich. I dont know what I am doing wrong

[Joe6pt0]

how can the sd tune remain the same with the change in temp and alt.

Here's a good answer to that.

http://www.hptuners.com/forum/showth...?t=6345&page=2

Its a few pages long, but worth the read. Some have found major success with this method of setting Cylinder Charge Temp Bias toward ECT. I'll be trying it out shortly.

[speedyss]

i did this about a week ago and it didnt work, still had lean starts, hot and cold, i know its working cuz i can see it in hpt, when i change the pot postision, the temp changes, i can go from 20* to 200*, but i doesnt help my lean starts and it doesnt help my tune no matter where what temp i tell it, and i try bias set a 0, .5, and 1 and still doesnt change anything, but here the the bias doesnt work on older os's mine's a 99, i soon am get the 1 bar os from hpt tho, will this help some of my problems?

[Russ K]

Did you try disabling the air pump? The air pump be operating every time you start the car untill it goes into closed loop.

Russ Kemp

[speedyss]

mod list, i have race style long tubes and no egr or air pump, and im runing in sd mod all the time, no maf, untill i can tune my ve table in correctly.

[Russ K]

Post your tune & the scan log from it, and I'll take a look at it for you.

Russ Kemp