Modifying timing/fuelling easily and effectively
11-21-2005, 12:19 AM
#32
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
What has big eyes... green, pink or purple long straight hairin the style of Don King that poofs out when you spin it in your hand? 
Thats may take.
over and out.
Thats may take.
over and out.
11-21-2005, 02:10 AM
#34
Three Wheelin'
Originally Posted by sjsj
The DFA can be considered a general purpose voltage remapping device. It works within 0-1V (so can modify an O2 sensor signal), 0->5V and 0->12V range as per article http://autospeed.drive.com.au/cms/A_2418/article.html . From my experience it can also be set to intermediate ranges such as 0->6V for instance by changing the adjusting the onboard adjustable potentiometers.
The DFA allows +50% and -50% adjustment of a signal at any of it's points along it's range. The only thing it doesn't do is invert the signal if you are for instance mapping 0-5V to 5-0V, as is the case for me changing from a AFM to a MAF, yet the ECU still requires an AFM type signal. I'm playing with my DFA to do this.
sjsj
The DFA allows +50% and -50% adjustment of a signal at any of it's points along it's range. The only thing it doesn't do is invert the signal if you are for instance mapping 0-5V to 5-0V, as is the case for me changing from a AFM to a MAF, yet the ECU still requires an AFM type signal. I'm playing with my DFA to do this.
sjsj
11-21-2005, 03:47 AM
#36
Advanced
Thread Starter
Join Date: Nov 2005
Posts: 88
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Louie928
Sounds like it would work then. You'd need to enable it only at WOT when the LH is in open loop.
My understanding of other cars I've worked on is car goes open loop during WOT and constantly changing throttle positions. It's there that the MAF signal is used when the O2 signal is too slow to respond.
The O2 signal is used during constant cruise conditions such that AFR is maintained at 14.7:1.
EFI cars can and do run without the O2 signal connected, just that they are running open loop which usually hits fuel economy pretty hard.
Cheers,
sjsj
11-21-2005, 01:19 PM
#37
"One thing to remember is that the 928 in stock form is already tuned very close to optimum. Those Porsche engineers were no dummies. You can tune timing a little closer to the edge and extract a litttle more. Mixture tuning doesn't get a lot more power since it isn't very critical except for needing rich at the top end of the power range for thermal safety. Until you do other things to the engine to get it to pump more air, and the stock A/F map doesn't quite fit anymore, you won't get a lot of gain."
- Louie928 -
He's said it all! The above statement should fully clarify the basic results of a DIY tuning
effort, whether it's on a basically stock 928, 944, 911, or most late model vehicles with
an engine management system.
- Louie928 -
He's said it all! The above statement should fully clarify the basic results of a DIY tuning
effort, whether it's on a basically stock 928, 944, 911, or most late model vehicles with
an engine management system.
11-21-2005, 05:47 PM
#38
Advanced
Thread Starter
Join Date: Nov 2005
Posts: 88
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Lorenfb
Until you do other things to the engine to get it to pump more air, and the stock A/F map doesn't quite fit anymore, you won't get a lot of gain."
- Louie928 -
He's said it all! The above statement should fully clarify the basic results of a DIY tuning effort, whether it's on a basically stock 928, 944, 911, or most late model vehicles with an engine management system.
- Louie928 -
He's said it all! The above statement should fully clarify the basic results of a DIY tuning effort, whether it's on a basically stock 928, 944, 911, or most late model vehicles with an engine management system.
AFM equipped cars will, as a natural course of their design, become richer through time as the spring mechanism weakens and is no longer "as tight" as from the factory. A richer mix means the engine bogs down and does not provide maximum power. A basic fix is to open the cover of the AFM and recalibrate the AFM . See following URLS for more info:
http://www.bimmernut.com/wwwboard/e23/messages/71.html - calibrating AFM
http://www.alfagtv6.com/afm_mods.htm - shows internal pics of AFM
As to '"the stock A/F map is already tuned for best performance", I suggest looking at the various different fuel grades available and then evaluating this question. The porsche engineers gave an approximate fuel map to cater for most cases. It will not be a high performance map specifically to your car..
Put in high octane fuel and your fuel maps are no longer at their best performance level. Higher octane fuel can be likened to 'richer mix'. Make any other mods to intake, exhaust of combustion without correcting maps and open-loop operation suffers [closed loop will compensate via the O2 sensor], but floor it and it's not gonna hit you in the guts to the level that it could.
Consider viewing other thread at https://rennlist.com/forums/928-forum/239258-inexpensive-way-of-converting-to-better-flowing-maf-or-from-afm-to-maf.html for an which details an inexpensive way of plumbing in a tunable MAF/AFM or swap out a AFM for a better flowing MAF.
sjsj
11-21-2005, 06:25 PM
#40
Addict
Rennlist Member
Rennlist
Site Sponsor
Rennlist Member
Rennlist
Site Sponsor
Sjsj .....you appear to be very good at internet research and accumulating information. Perhaps some day you will understand all that you know. Credibility is something which develops over time and I am thinking in your life there has been little opportunity for that. In life when you encounter a new situation , new group social setting it may be best to emulate the behavior of monkeys. Young males leave the family group and travel until they find a new band. They observe from a distance for a day or so then enter the band and pick a fight with just one resident if they win then the newcomer's status is just above the defeated monkey. That is so much better than having to fight all the monkeys just to figure out where he fits in ....
11-21-2005, 07:33 PM
#43
Advanced
Thread Starter
Join Date: Nov 2005
Posts: 88
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Jack '84 928s
I think Sjs' friends are named copy and paste and arm chair racer. He probably knows car and driver and google really well also.
Thank you for your kind works.
I know you. Those hand gestures are a sure fire dead giveaway! You're a movie star! Been in Starwars: Return Of the Jedi.
sjsj
11-21-2005, 09:17 PM
#44
Three Wheelin'
Originally Posted by sjsj
<snip>
As to '"the stock A/F map is already tuned for best performance", I suggest looking at the various different fuel grades available and then evaluating this question. The porsche engineers gave an approximate fuel map to cater for most cases. It will not be a high performance map specifically to your car..
Put in high octane fuel and your fuel maps are no longer at their best performance level. Higher octane fuel can be likened to 'richer mix'. Make any other mods to intake, exhaust of combustion without correcting maps and open-loop operation suffers [closed loop will compensate via the O2 sensor], but floor it and it's not gonna hit you in the guts to the level that it could.
<snip>
sjsj
As to '"the stock A/F map is already tuned for best performance", I suggest looking at the various different fuel grades available and then evaluating this question. The porsche engineers gave an approximate fuel map to cater for most cases. It will not be a high performance map specifically to your car..
Put in high octane fuel and your fuel maps are no longer at their best performance level. Higher octane fuel can be likened to 'richer mix'. Make any other mods to intake, exhaust of combustion without correcting maps and open-loop operation suffers [closed loop will compensate via the O2 sensor], but floor it and it's not gonna hit you in the guts to the level that it could.
<snip>
sjsj
11-21-2005, 10:20 PM
#45
Advanced
Thread Starter
Join Date: Nov 2005
Posts: 88
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Sterling
sjsj you have inspired me to do something no one else has done in the almost 5 years I have been on rennlist. I figured out how to put someone on ignore..... I've seen some annoying know it all's on rennlist, and you take the cake. (thankfully they are few and far between) I wonder why you even read the forums since you seem to know it all.
sjsj