An improperly tuned engine can get bad gas mileage, and fail emissions tests. If your engine is modified, these are the least of your worries. An engine that is running too rich won’t perform to its potential, and an engine running lean can detonate and destroy itself. Regardless the error, an improperly tuned engine can cost you a race, a championship, or… just money!
When tuning modified engines, accurate, wideband oxygen sensing equipment is critical. The keys to this process are
A heated, 4-wire oxygen sensor like the Bosch LSM-11, or preferably a 5-wire NTK/NGK UEGO (or the Bosch LSM-4 UEGO). This is not the $28 sensor from the parts store. Good sensors start at $500 and go to over $1000. It is important that they be relatively new (less than 500 hours) and kept at EGT’s (exhaust gas tempretures) less than 900c.
The sensor must be correctly located. A sensor in the tailpipe will react too slowly to changes in the mixture. A sensor mounted too close to the exhaust manifold (particularly in boosted or rotary engines) will be destroyed by the excessive tempretures.
So, somewhere close (but not too close) to the manifold is preferable. It is not difficult to weld the proper bung (a nut) to a downpipe(turbo) or collector.
In addition to the sensor, you must have accurate hardware (a “controller unit”) to make corrections for exhaust gas tempreture and convert the 0-5v readings from the sensor into corrected data. The correction factors are critical when tuning for maximum performance.
Last, and this sounds obvious, but its easy to overlook, you need to be able display the O2 readings in a meaningful format – for a given O2 sensor reading, you must know “where you are” in terms of RPM’s, boost, etc…
so you can interpret your data. This tells you and your tuner where to correct your fuel injection maps, make carb adjustments, or other changes to the fuel/air/ignition combination.
This is why the big boys come to the DynoLab.
Call for details about your setup, and what we can do for you.