View Single Post
  #3  
Old 09-02-2004, 09:03 AM
hotrod hotrod is offline
Senior Member
 
Join Date: Oct 2003
Posts: 307
Default slow and methodical

Just like folks can road tune an ECU rather than do it on a dyno, if you take your time, and methodically make small incremental changes you can over time dial in a very agressive system.

You description leaves a bit out though, its not just a single pass process.

Basically you start with a stable tune and gradually make small additions/changes while closely monitoring all the available information.

Remember until recently, people did not have the luxury of buying affordable wideband O2 monitors or even logging engine operations. They had to pull and read plugs, watch drag strip times, use their butt dyno sense of how the engine was running, did it have snap, or was it a bit flat. Get knowledgable friends to listen to the car as it went through the traps and then make sense of all the little clues.

Come up with a best guess of where they were, make a small change in the direction they wanted to go, and then do it all again. For folks who didn't live at the drag strip it might take a full season of tinkering to get the system dialed in to 90% of where they wanted to be. Then another season to get that last 10%

The system is much like the basic process of dialing in a new engine and carburator or distributor before all the magic diagnostic resources were availble.

From the basic safe street tune they added water until the engine sounded and acted "soggy" fiddle with the turn on point a bit to find where they "needed" the injection to come on, and where the engine "liked" it to come on.

Then they started adding boost in small increments. If the added boost cleared things up, then when they got close to detonation, they would add a bit of timing or subtract a bit of timing, or subtact a bit of fuel or add a bit and see if things improved or got worse. If the move was good, then they would add or subtract a bit more. They would basically baby step their way towards an agressive tune. First adding boost, then changing ignition timing, then tweak the air fuel a bit. When they were to the point the could make no more improvements, they would start over adding more water. If they developed a flat spot or other rpm dependent problem they would then fiddle with the turn on point or jet location of the injectors. Some times going to multiple staged injection, where one set of jets came on at one boost level and another came on at a higher level.

One of the advantages of this process is you learn how the car behaves if it has more ignition timing or fuel or boost than it wants, so you become better at reading the behavior when all other means of diagnosis fail.

Larry
Reply With Quote