View unanswered posts | View active topics It is currently Mon Dec 18, 2017 9:31 pm



Reply to topic  [ 3 posts ] 
Basic Tuning Techniques 
Author Message
Moderator
User avatar

Joined: Tue Jan 15, 2008 2:31 pm
Posts: 14914
Location: Home sweet home!
DRAFT - please post in this thread with your ideas and suggestions and techniques. Once it is fine tuned, I will migrate it to a web page and leave this thread for feedback and discussion.

Before you start, your Lambda table should be configured to represent what you desire in terms of fuel-air mixtures throughout your operating range. You then adjust the VE table to cause the chosen mixtures from the table to be reflected in the exhaust stream. This is all that tuning a fuel map consists of, in simple terms.

Your ignition timing table should also be tuned fairly close to where it needs to be, and slightly conservatively (retarded from estimated optimal numbers).

  1. drive, noting down details of issues and/or logging data
  2. tune a region based on sensor or vehicular feedback
  3. adjust adjacent regions to be similar and follow visible trends

Repeat 1 through 3 until fine tuned and as close to perfect as you want.

The usual method for gaining feedback about what to change is via wide band oxygen sensor in the exhaust stream, after the turbo, and not too close to the vehicle exit point. There are some catches to this method, however, in the most part, it works very well and is very straight forward. Be aware, though, that if the mixture is very rich, and the ignition can not cope with the richness level, a misfire will show as full lean in your recordings or readings. This can occur in the 9:1 - 11:1 range for normal gasoline/petrol and similar race fuels. Additionally, also be aware that ignition timing affects *visible* air fuel ratios as read by the sensor, but NOT the real value. If the timing is somewhat retarded

It is possible to tune without a wideband using a variety of techniques. If there is black smoke in the exhaust stream, it's probably too rich. If the plugs are black and fouling it's too rich. You can tune richer and richer under full load until you start to lose butt-dyno torque (or acceleration measured with a g-tech or similar) and then lean out slightly to your last setting with good torque. Likewise, in cruise regions, you can tune leaner and leaner until you start to lose torque or notice other inconsistencies, and then richen back up a little. The balance of the tune can be varied in between these extremes to feel good and not ping/rattle/knock/etc.

Note, tuning without a wideband is only recommended for those on a tight budget and with naturally aspirated engines on relatively low compression ratios.

If you find that the Lambda values are not suitable for your engine, or want to go richer in boost, or leaner in cruise, etc, just adjust the desired Lambda values in the Lambda table and if your VE is tuned well, you will get exactly what you enter as a result on the car. There should be no need to retune the VE table to effect this type of change. The VE of the engine does not change without a physical change to the engine such as manifolds, exhaust, cams, turbo, porting, etc. Beware in some other inferior and more primitive systems, you are forced to change "VE" values to change your AFR/Lambda. If you have to do this, then what you are changing is not actually VE at all - upgrade.

Good luck! :-)

_________________
DIYEFI.org - where Open Source means Open Source, and Free means Freedom
FreeEMS.org - the open source engine management system
FreeEMS dev diary and its comments thread and my turbo truck!
n00bs, do NOT PM or email tech questions! Use the forum!
The ever growing list of FreeEMS success stories!


Tue May 24, 2011 2:01 pm
Profile WWW
Moderator
User avatar

Joined: Tue Jan 15, 2008 2:31 pm
Posts: 14914
Location: Home sweet home!
A recent thread by Hentai on the same subject: viewtopic.php?f=54&t=1965

Maybe I should merge the posts?

_________________
DIYEFI.org - where Open Source means Open Source, and Free means Freedom
FreeEMS.org - the open source engine management system
FreeEMS dev diary and its comments thread and my turbo truck!
n00bs, do NOT PM or email tech questions! Use the forum!
The ever growing list of FreeEMS success stories!


Sat Dec 01, 2012 10:03 pm
Profile WWW
LQFP144 - On Top Of The Game
User avatar

Joined: Sun Jul 18, 2010 2:35 pm
Posts: 299
sounds good to me!


Thu Dec 13, 2012 1:01 am
Profile
Display posts from previous:  Sort by  
Reply to topic   [ 3 posts ] 

Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group
Designed by ST Software for PTF. ColorizeIt.