[Subscribe to Daily Digest] |
Hi !
Let me try to explain some basic ideas.
First why use lambdasensor, EGT.
The lambdasensor (broadband) gives you correct information about actual fuel/air deliverd to the engine.
A lambda value around 0.90-0.95 will give you maximum power for a given airmass, however, TuRbo charged engines usually run richer than the optimum lambda (0.90). They just need that "extra" fuel to cool down the combustion. Without this enrichment we can have the following problems: overheated exhaust valves, overheated exhaust manifold/TuRbo charger, general overheating of the engine, knocking.
So, some "rules of thumb" run as "lean" (abt. 0.90) as possible WITHOUT having problems with knocking and high EGT.
Do not run richer than abt. 0.65 sine this will (more or less) wash a way the oil film on the cylinderwalls. You also LOOSE quite a bit of power running this rich !
When tuning (making a fuel map) an engine use lambda so that you know "where you are".
EGT: EGT is used as a limiting value.
Or in other word, there is a maximum limit you need to stay below !
Otherwise you engine will be damaged, exh.valves, turbine, exh. manifold, cat.
The EGT dependes on a combination of fuelmass and ignition timing at a given airmass flow.
So, lets's say you're running at 3000 rpm/1 bar of boost, more fuel will give you lower EGT, advanced ignition timing results in lower EGT.
And the other way around, less fuel will raise the EGT, and retarded ign.timing result in higher EGT.
You NEED to "BALANCE" fuel and ignition to et an engine that runs without knocking and too high EGT.
A change in the fuel map calls for an adjustment of the ignition timing, and to make it really fun, a change in ignition timing calls for a fuel adjustment. I'll guess that the most useful method for most "street" applications is to use an EGT sensor to make sure that the engine is within limits. The lambda sensor is used as a guide, so that you know that the changes you make results in something. And make sure that you not running too rich. Too lean will normally be indicated by HIGH EGT and/or knocking.
A good knock sensing device is VERY useful......
I'll have to do something else now, I'll be back !
posted by 62.20.185...
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
