Revealing busa ECU secrets, part 3 - Ignition

[PetriK]

This is the final part of revealing busa ECU secrets covering the ignition. One of the main reasons why one should consider upgrading the stock ECU is the ability to change the ignition maps to reflect the changes made to the engine. Ignition is the key ingredient in making the most out of the improved volymetric efficiency of the engine.

For example a cam change enables usually more overlap and hence better fill of air/fuel mixture at a particular rpm. More fuel/air mixture compared to a mixture where fuel/air & burned gases (=less VE efficiency) means different burning speed, i.e. different ignition advance.  Another thing effecting the VE is a simple modification of changing the throttle bodies changing the VE at certain parts of the RPM band. For me the key ingredient of timing change is the ability to have retarded timing for nitrous usage, something the turbo guys may also appreciate.

K5&K6 (and assume the same applies to K4&K7 too) Busa as such has the following ignition maps when it comes from the factory:
- Gear 1 ignition map
- Gear 2 ignition map
- Gear 3,4 ignition map
- Gear 5,6 ignition map
- Neutral / Clutch ignition map
and all of these are doubled into two banks, one for inner other for outer cylinders. Additionally all the maps have a "spare copy" that can be programmed behind the MS (map select signal), i.e. a swhich that does the map change (e.g. for nitrous or boost). So all together 32bit busa has 20 ignition maps with some adjustments there too. 

Alike to the injector coils the ecu expects to receive the coil reverse voltage peak as an indication of healthy ignition system. The coil charge seems to change according to the RPM, but I have not yet found the coil charge map. The coil charge is quite big at lower rpm getting very low at around 5-7k then getting bigger again at around 8-9k. The changing coil charge means that the ecu program tries to keep the coils temperature low and make the coils last longer. So after figuring this out I dont anymore have any reasons to consider an ignition upgrade.... as there also seems to be a map that compensates for a lower voltage in the system.

Some of the maps are very alike, but biggest differences are between map for 5&6 gear vs. the rest. Also there is quite big difference between Bank A and Bank B maps. I suspect there being two reasons for the A/B difference: first at lower rpm the throttle bodies make the VE different between cylinders. At higher rpm the differences are much smaller, but I believe that Suzuki wanted to run the middle cylinders a bit cooler and kept the advance a bit lower. But these are just my personal thoughts.

Even though I am not exactly certain about the exact timing in absolute degrees, here you can see a sample of various maps that K5 Euro Busa has for your information.

Gear2 BankA, note the dip for lean cruising area:


Gear5,6 BankA, note how there is much more torque at acceleration area


Gear5,6 BankB, note how this is different to BankA


Neutral/clutch map, note how this is only RPM, totally independent of TPS position.

[dakinebusa]

Interesting work.
I really like the color coded tables.

[ECS Walter]

The velocity stacks could be reasons for differences in the 1-4, 2-3, maps??


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[PetriK]

The velocity stacks could be reasons for differences in the 1-4, 2-3, maps??-

Yes - as I AM now running all short after getting rid of the FP velocity stacks I am thinking to custom tune the cylinder banks A/B to me more closer to each other. The ignition is about 3-4 degrees different between inner / outer cylinders up to top where its only 1 degree. The inner cylinders are also running a tad bit richer until after a point where the outers almost are the same indicating the power curve being slighly different. To me this is definately an area for testing if there is more power because of the short stacks mod to be gained.

Unfortunately its very witery here so time must wait unti next season. But certainly I am interested in flatteing the differences  of those maps for more peak power.

[gazza414]

The bottom line is you will never know unless you put widebands in each header.... what the assumption is "is that the dynamics in the airbox provides uniform feed to all stacks at all operating conditions"

something to consider

ps PetriK  , as a side note why did you get rid of the Factory Pro stacks?

[PetriK]

ps PetriK  , as a side note why did you get rid of the Factory Pro stacks?

Instead of cylinder specific WBO, just thinking of checking the EGT per cylinder.

About FP stacks, I think I wrote it somewhere here in more detail, but basically lost noticeable power at high end where as did gain some lower end. For my goals the top end is more important.

[emptys]

any change of making these three postings sticky?

i know i'm going to want to re-read them, and figure
i'll lose track of them ... by ... uh .... tomorrow.

[DaveO]

The velocity stacks could be reasons for differences in the 1-4, 2-3, maps??

Walter,

I believe cylinder temps are the reason. Many manufacturers have had diff jetting/tuning for the center two cylinders with all stacks the same length....

Dave

[PetriK]

The velocity stacks could be reasons for differences in the 1-4, 2-3, maps??

Walter,

I believe cylinder temps are the reason. Many manufacturers have had diff jetting/tuning for the center two cylinders with all stacks the same length....

Dave

TOP rpm no doubt, but really also at low rpm area ?

I have always thought that the low rpm and low VE means lower cylinder temps due to unburned gases being left in the cylinder  ? (like the EGR valve in cars). With AFR one can not change much, but with ignition advance due to different burning speed you can move the peak power (14deg atdc in theory ?).

So I would be still enclided to say that with low rpm area and a partial cylinder fill (not optimal throttle body size) means different ignition curves to optimize the torque and power ?

???

[ECS Walter]

I was thinking the same, fuel and timing demands for the ways the shorter and longer stacks are filling the clys. at different RPM's? I was assuming thats how they are smoothing out the power curve on a stocker.


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[DaveO]

Petrik,

I would think the timing for the center cylinders would be a couple degrees retarded to minimize detonation from the higher temperatures...as good as H2O coolin is...I am sure the center two chambers are warmer due to less external surface area...Just my personal opinion...

I know in 2000 they changed the ECU software to have diff cylinder timing for 1/4 and 2/3...I ASSUMED it was for this reason....I have never proved it...and testing on the dyno did not show it....

Anyhow a BIG thanx for bringing this info to us!!!!

Dave

[ECS Walter]

+1


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[PetriK]

Petrik,

I would think the timing for the center cylinders would be a couple degrees retarded to minimize detonation from the higher temperatures...as good as H2O coolin is...I am sure the center two chambers are warmer due to less external surface area...Just my personal opinion...

I guess this meant to say CO2 as that is the residual gas left in cylinder preventing high burining with low VE:s.

I am not really trying to argue here, its just that the data does not match what is assumed.

These are my findings related to how much bigger advaces for BankA (outer cylinders)
800rpm       +4degrees
1200rpm     +8degrees
1600rpm     +3degrees
2000rpm     +12degrees
4000rpm     0 degrees
6000rpm     +5degrees
8000rpm    +4degrees
10000rpm   +1degrees
In the above it she area <4000rpm that caught my interest as there the main reason is very unlikely to be the cylinder temperatures.

Corresponding fuels are cyl 0/1/2/3
800       72/62/68/72
1000     72/68/68/72
2000     72/81/81/21
4000      86/89/89/86
6000      97/96/96/97
8000      103/104/104/103
10000     97/94/94/97

So they are running less fuel in middle cylinders (or I may have copied something incorrectly) and still more advance there particularly at low VE area ? Does not make sense to me as an attempt for cooling effect (exept around 8000rpm which is the peak torque area and maybe most prone to detonation) ?

Maybe its something else - maybe for emission reasons they needed to do something to the burning process due to different cylinder filling ratios ? In that range in some cars you actually need to pump up the fuel at low rpm with PAIR on just to ensure that the cats are running warm enough. And when reading the above this is from CATTED version of busa....

[gazza414]

Cyl temp variations in a water cooled engine??? I'd suggest very unlikely.

old days of air cooled jetting kits yes.

The other way PetriK is to see if you can find target A/F's table...you may have to work backwards though

[Busa Quick]

Cyl temp variations in a water cooled engine??? I'd suggest very unlikely.

old days of air cooled jetting kits yes.

The other way PetriK is to see if you can find target A/F's table...you may have to work backwards though

 DaveO said: I would think the timing for the center cylinders would be a couple degrees retarded to minimize detonation from the higher temperatures...as good as H2O cooling is...I am sure the center two chambers are warmer due to less external surface area...Just my personal opinion...

[DaveO]

Petrik/Gazza,

It is just assumption on my part...I have no other reason why the difference for the center bank.

Dave

[dakinebusa]

Nobody has ever built a motor where the cylinders all run at the same temperature.
Except for a single

[Busa Quick]

  Sticky please.


Mark

[glenn71]

ive got  wideband bungs for each header,the middle 2 run leaner with all short stacks and unified ignition and fuel maps.I added 1-2% fuel to them.

[Pete]

Cool that's great info - thanks

[Johnnnycheese]

I need to see a copy of a Neutral map
I don't have a 32 bit at the shop right now.

[Oz Booster]

Bottom of the first post on pg 1

[sportbikeryder]

Or here....   

[Johnnnycheese]

thanks i missed it.

[gazza414]

those 2 ignition maps that have been posted ( Petrik and Sports* ) have different values  to each other JC