Injector Timing

[TransAmDan]

Many years ago I installed a heads and cam kit. The cam is a 226/226, the standard cam was about a 198/200. Well a few weeks ago I was thinking that the valves open earlier, and there is an overlap between intake and exhast.
However with this change in valve events I havn't changed the injection timing. I've changed spaprk events and fueling, but not when the injector fires. I've never seen talk of this feature on forums so I thought I'd bring it up on the LS!tech forum, http://ls1tech.com/forums/pcm-diagnostics-tuning/1427353-anyone-played-injector-timing.html
Basically with this overlap in valve events, some of the raw fuel can get sucked out into the exhaust. So if the injection fired a little later after the exaust valve has closed then it can burn more of the fuel I squirt in.

 

[TransAmDan]

Went for a drive at lunch time doing some data logging on the laptop.
It seems to be pulling back at load load RPM's I'm still working on the fueling, although its not far off. While driving I took off 10degree of spark advance, at first this seemed to improved things, but once warmed up it was worse. I'll carry on working on the fuelling. I could toggle this timing advance on/off while driving at the click of the mouse button.

I'll do some more logging on the way home from work. Low loads at around 1500-2000 rpm. Want to get this spot on before doing wide open throttle tuning.

The car was running fine a few weeks ago, but I wanted to sort out the injector timing due to it firing when the exhaust port was open too. although its been like this for a couple of years, it would be nice to reduce the raw fuel smell when idling.

 

[TransAmDan]

Done some great logging on the way home from work. 35-40mins of good data from it being warmed up, the fueling is up to 8% incorrect in places depending on RPM, mainly at low loads between 1000-2500rpm.I'll implememnt the logged data to the next tuning file that I will zap in tommorow.

 

[TransAmDan]

Went for a drive at lunch time. I notice on a warm start its idles around 300-400rpm, and surges to 700rpm. I've adjusted the warm start to starting with more air on start up which will decay away about about 30 seconds.so this should idels around 1000rpm before dropping to about 750-800rpm. I've also adjusting the idle timing lower. Its nice and lumpy now. Just the way I wanted it. Was on tick over for about 90seconds, then when i got out of the car, I got very close to my rear end and couldn't smell gas at all (mind you I hadn't eaten the bacon&egg sarnie by then) there was no rich smell at all. Well chuffed.

 

[TransAmDan]

Done a little more logging at lunch time today. When I start the car up from cold and start drive just about 1200 RPM it runs really lean which ofcouase the after start enrishment should still be inplace at this point. With this leanness its a bit jumpy. At this point the Fuel Trims are ignores as its not in closed loop this early in the cycle, need to warm up to over 160 degrees. So this much be lack of fuel on the VE mapping. So at lunch time i logged the fuel trims and notice 6% of fuel needs to be added to those offending cells. This will very much effect the after start enrichment to be on target for the desired fuelling.

Also I've retarded the timing by a few degrees to have a better blend between idle spark and in gear driving spark as pulling away the fuel is about correct but the timing is a little jumpy. I think I'm getting there. I'll know more on the drive home from work.

 

[TransAmDan]

The injector timing has gone well. I've been altering the fuel mapping around idle and up to 2500rpm is pretty much spot on. Is a couple of percent too rich at 1500rpm, reading about 14.2 AFR instead of 14.6. This should be a minor tweak.
While I've been out looging data of the sensors for fuelling I just has to do a couple of WOT (wide open throttle) runs, couldn't resist. Done a quick of quick blasts on the way down to club night.
The ECU has a register called Commanded Air Fuel Ratio, this basically uses the fuel reading from the Volumetric Efficiency MAP, and multiplies it by the Power enrichment figure. I was asking the ECU to command between 12.5AFR and 13.2AFR depending on RPM when foot to the floor. However the commanded recult seemed to be 11.7 AFR, this is very rich for a naturally aspirated car (forced induction this AFR would be hi 10's to mid 11's). I've been comparing older log files and I can see the car has commanded the correct fuelling before. Looking deeper into the configuration, somehow the CAT over temp protection flag has been set. This means it will dump in extra fuel to keep the cats cool. I cleared this flag. And went for another run yesterday lunch time. WOT fuelling is working well now, and pulls very good with little black smoke behind apart from tyres. If the car runs too rich UN-burnt fuel appears as black smoke.
The car is feeling good and strong and good around town, got rid of the bucking.
Just need to get an extra pair of wheel nuts as have two missing at the back.