Run car w/o MAF Sensor in SD all the time ?
05-07-2005, 10:12 PM
#21
On The Tree
Join Date: Feb 2004
Posts: 114
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by WS6FirebirdTA00
also, based on calculations, the car would actually theoreticly run richer in hotter temps. so tx horns, i wonder why you got negative with colder temps? at least this is just what my professor said.
the fact is that SD tunes are very dependent on the accuracy of the IAT sensor to comp for temp changes in the calculation of the mass of air entering the cylinders. but with the MAF it measures Mass Air Flow in a manor that is much less dependent on the IAT, due to the fact that the sensor element is heated to >600 deg, a 30 deg swing in IAT with an error of 5 deg is nothing. The maf is a much more accurate (provided that it is calabrated correctly) sensor in the range we use it. the SD setup that is calculating the mass air flow from the MAP sensor and the IAT with the same 5 deg error on a 30 deg temp swing will give a much worse result.
when it is all boiled down you can get just as good of a tune with just the SD setup, but it will be more work to keep it tuned than a MAF/SD combo setup.
JMO
More Than Zero
05-08-2005, 12:18 AM
#22
TECH Fanatic
iTrader: (12)
Join Date: Jan 2004
Location: Houston, TX
Posts: 1,869
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by M_T_0
the fact is that SD tunes are very dependent on the accuracy of the IAT sensor to comp for temp changes in the calculation of the mass of air entering the cylinders. but with the MAF it measures Mass Air Flow in a manor that is much less dependent on the IAT, due to the fact that the sensor element is heated to >600 deg, a 30 deg swing in IAT with an error of 5 deg is nothing. The maf is a much more accurate (provided that it is calabrated correctly) sensor in the range we use it. the SD setup that is calculating the mass air flow from the MAP sensor and the IAT with the same 5 deg error on a 30 deg temp swing will give a much worse result.
when it is all boiled down you can get just as good of a tune with just the SD setup, but it will be more work to keep it tuned than a MAF/SD combo setup.
JMO
More Than Zero
when it is all boiled down you can get just as good of a tune with just the SD setup, but it will be more work to keep it tuned than a MAF/SD combo setup.
JMO
More Than Zero
And to avoid any confusion, I had my tune setup very well in SD, and right after recalibrated my MAF. This will be a necessary order of things to do to get your fueling right. Tune the MAF as soon as your SD fueling is within a well accepted range.
05-08-2005, 09:32 AM
#23
Teching In
Thread Starter
Join Date: Feb 2005
Posts: 35
Likes: 0
Received 0 Likes
on
0 Posts
Good points, guys. I calibrated my VE table without the MAF connected, and got all cells pretty close to zero, i attached a pic of the LTFT histogram. I will calibrate the MAf and see if the car runs better with a good tuned MAF. As i said before, the car surges a bit on light cruise and it "feels" more smooth and stable in SD. Might just be because my LTFTs are well out of range when MAF is reconnected.
05-09-2005, 10:32 AM
#24
I haven't use the excel file as I can't figure it out 
Never used excel before...at all.
What I did is I tuned <4k rpm VE from 0 to -3 everywhere then plugged the maf back in. The entire table was +14 to +16. I multiplied the entire maf table (line) by 16%. Now all my MAF connected LTFTs are 0-3, sans the idle cells. Due to the cam but we're all aware of that problem.
I am sure using the mass air calcs are more precise but this got me in the ballpark.
Never used excel before...at all.What I did is I tuned <4k rpm VE from 0 to -3 everywhere then plugged the maf back in. The entire table was +14 to +16. I multiplied the entire maf table (line) by 16%. Now all my MAF connected LTFTs are 0-3, sans the idle cells. Due to the cam but we're all aware of that problem.
I am sure using the mass air calcs are more precise but this got me in the ballpark.
Last edited by mr2guru; 05-10-2005 at 01:05 AM. Reason: corrected error
05-09-2005, 10:43 AM
#25
TECH Fanatic
iTrader: (12)
Join Date: Jan 2004
Location: Houston, TX
Posts: 1,869
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by mr2guru
I haven't use the excel file as I can't figure it out Never used excel before...at all.
What I did is I tuned <4k rpm VE from 0 to -3 everywhere then plugged the maf back in. The entire table was +14 to +16. I just reduced the entire maf table (line) by 16%. Now all my MAF connected LTFTs are 0-3, sans the idle cells. Due to the cam but we're all aware of that problem.
I am sure using the mass air calcs are more precise but this got me in the ballpark.
Never used excel before...at all.What I did is I tuned <4k rpm VE from 0 to -3 everywhere then plugged the maf back in. The entire table was +14 to +16. I just reduced the entire maf table (line) by 16%. Now all my MAF connected LTFTs are 0-3, sans the idle cells. Due to the cam but we're all aware of that problem.
I am sure using the mass air calcs are more precise but this got me in the ballpark.
05-09-2005, 03:10 PM
#26
Teching In
Thread Starter
Join Date: Feb 2005
Posts: 35
Likes: 0
Received 0 Likes
on
0 Posts
I too would think to increase MAF values if LTFTs are in the positives. e.g. i have 39.72 g at 5000 Hz, i will add 15%, so i come to 45,68 . . .
I will do this with all values and log again LTFT to see how things has changed . . .
Thanks,
Jochen
I will do this with all values and log again LTFT to see how things has changed . . .
Thanks,
Jochen
