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Post Info TOPIC: ECU engine tuning theory and application


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ECU engine tuning theory and application


The next step now after knowing most of the maps and having tested that they work as expected is to start consider how to put all this information into practical use.  This writeup is really about considering the options and possibly building tools for tuning in real world.

Btw. maybe this could be a topic for new subforum ?
ECU engine tuning theory and application
... as this is really about putting the theory in practise in the seek for more power and more speed.

As we all know Bike tuning in its simplicity is really all about making a run and then correcting the values for a better run. All the changes usually are made to maximize the power, even at a cost of increasing fuel consumption, risk for engine failures and increasing emissions.

There is in prinsiple three major areas to concentrate when tuning the bike for maximizing the power after any major changes made:
1) Fuel maps
2) Ignition maps
3) Acceleration enrichment

The fuel maps are used to compensate the VE of the engine by increasing or decresing the amount of fuel delivered to the engine. The target AFR for optimum power is around 12.8 - 13.1:1. Anyhow this is only part of the equation where the residual gas, cylinder temperature and several other factors play a major role. Also the various compensations play a role, like ram air compensation which from my opinion should really be "disabled" for the gear used in dyno.

Tuning for fuel delivery for max power

To be able to tune for the fuel we need to know the following things at any given moment:
1) Which map is used
2) What is the RPM
3) What is the IAP or TPS value
4) What was the map value used
5) What was the actual AFR
6) Was there any major fluctuations between cylinders

For me there is two major approaches for obtaining that information:
A) Using an external datalogger like LM1 and hooking that into analogue sensors (IPA,TPS, Gear, RPM and WBO)
B) Building a datalogger that logs any run either using the serial protocol or alternatively using the AUD inverface and then combine that information with external WBO sensor from dyno or LM1.
Also a combination of both of these can be an alternative.

Tuning for ignition for max power

Tuning for ignition is slightly different from AFR. The information about best ignition requires an additional sensor information. Either having an EGA (exhaust gas analyzer) or at minimum an EGT sensor. As the EGT sensors are way cheaper and widely available I will be opting to go for that route. Afte the AFR is set the EGT sensor will show a drop in the EGT when detonation start to occur. On the other hand the EGT will raise if the valves are starting to open when the fuel is still burning. But the good thing of this information combined with a WBO is that unburnt fuel means changes in AFR. So for tuning for ignition advance we need to add EGT sensor information to the list:

1a) Which FUEL map was used
1b) Which Ignition map was used
2) What is the RPM
3) What is the IAP or TPS value
4) What was the map value used
5) What was the actual AFR
6) Was there any major fluctuations between cylinders
7) What was the EGT reading at any given moment

Tuning for acceleration

From my previous experience tuning for acceleration is a fairly different to getting the best power out of the engine. Even in dyno the acceleration enrichment may play an important role. Also at lower gears we have a different situation that with higher hears due to the load generated. When accelerating with gear 1 & 2 the key objective is really to keep the front wheel down - not usually even close to the maximum power. The power delivery can be controlled e.g. with less ignition advance. So its very good to have separate ignition maps for lower gears. At higher gears the low end torque plays a major role so that becomes a game for avoiding detonation where EGT information is handy.

For best acceleration we need to add some more sensor information to the equation including which gear was used and at what time which rpm was reached. Additionally information about wheelspin would be handy to have but not mandatory. All this information must be able to be presented in a timeline of events.

1a) Which FUEL map was used
1b) Which Ignition map was used
2) What is the RPM
3) What is the IAP or TPS value
4) What was the map value used
5) What was the actual AFR
6) Was there any major fluctuations between cylinders
7) What was the EGT reading at any given moment
8) Which gear was used
9) A timeline of events

With all of this information processed I am really geared towards connecting an external datalogger into the bike to monitor the above mentioned sensors/information. Even how tempting it would be to connect a wide band oxygen sensor into the busa oxygen sensor input and just run all the data through the ECU I still currenly believe that all the information needed can best be pby Innovate LM1. When connected to the sensors above it has capasity to output e.g. TPS/RPM, IAP/RPM maps and timeline of events.

The following is real world information from far from well tuned engine from last summer. That information now combined with things we know about fuel maps at full throttle really explains why it was running so rich with intake well advanced for peak power.

TPS/RPM AFR
TPS_RPM_AFR.JPGrovided
IAP RPM AFR
IAP_RPM_AFR.JPG

A timeline of events
quartermile_timeline.JPG

Some background reading for the topic:
http://www.clubwrx.net/forums/showthread.php?threadid=14426
http://www.innovatemotorsports.com/forums/archive/index.php/t-1232.html



-- Edited by PetriK at 13:04, 2008-01-06

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