Calculating acceleration enrichment on alpha-n

[GintsK]

With ITBs my suggestion is camsync, yes. It makes difference for sure!

I just took a look to your config. Before accel you have to tune your VE table. You do not need a rolling road for VE table optimization. Just drive around on various loads, change throttle position as smooth as you can, and finally use VE tune by statistics under tools. From your log it already calculates more common shape of VE table.  I think you can find some video on youtube how to.

Where your injectors are located? Does it sprays directly to valves? Or?

[se7ensport]

Cam cover: ebay here I come!

I have looked at tune by statistic, but I assumed that live VE tune was more accurate which is the approach I used on the dyno.

My injectors are in the throttle bodies, immediately after the butterflies, they are angled towards the head.

[GintsK]

Live tune can not be more accurate. It changes just current cell while neighbour still have influence.
Tune by statistics do not corrupt table at one point and that means - error from ideal is smoother if initial table is smooth.

Just towards the head or exactly towards the valves? It is important. Spray pattern as well.

[se7ensport]

Interesting comment on live tune, I'll make the effort to get a good log and use tune by statistic.  Out of curiosity, how do you tune a new engine from scratch?

Injectors are spray type "E" (dual spray), 20 degree alpha 50, a clocking angle of 90 degree.  They are angled towards the head, not exactly at valves as they are around another 40 degrees away.

[GintsK]

Even on dyno I use tune by statistics. Still MLV. First is raw tune. Second WOT runs - from them I find optimal places for rpm axes. Then fine tune.
BTW EGO correction nowadays is pretty fast. You can rely on it for WOT tuning. May be not on second gear. But third is OK.

If you want streetable/enjoyable car it is very important to spray directly to valve. Valve is way hotter than walls. If injector sprays on walls most of fuel just form huge liquid film. And you do not knew when this fuel going to burn. Ten cycles after. Or even never. That is worse than carburettor. At full load picture comes better because of air flow. Watching your datalog tended me to ask this question.

Gints

[se7ensport]

Great info and thanks for taking the time to look through my log.

I can easily move the injectors to the head, which I'll do at the next opportunity.

I'll also use ego correction, what is a sensible number of engine cycles before a change?

[GintsK]

If you have place at head, there is still option to add second row of injectors and use staged injection. It is easy to tune, but you have to knew exact flow rates of both rows.

Cycles. 4 if sensor is very close to head. 10 if more than 1 meter.

One note: first value in accel enrichment should be zero: 0 40 60 120. Otherwise Ego correction might not work.

[se7ensport]

Once again thanks for the info.

The engine currently has 4 x 440cc injectors sat in the ITB that are active, it also has 4 x 240cc in the head that are unused. 

The simplest option would be to move the 440cc to the head and map from there. 

I'm expecting there to be a drop in top end performance, if its a couple of %bhp i can live with it, what would be your ballpark expectation?

If its a bit more I'll get hold of some injector clips and make a new bit of loom.

[GintsK]

Mapping with staged is similar. You only have to determine when start to add fuel from furtherest injectors. Say 240 will be maxed out at 200hp. Somewhere at 70...80% would be reasonable to add spray from secondaries. Watch at what rpms/tps you reach 70..80% of your current max duty cycle - and choose those for switching. Switching point can be changed on tuned map.

From my understanding main advantage from distanced injectors is cooling. Vaporization of fuel from walls may reduce temperatures below environment. Cooler = more air = more power.

So if you want technical way - go for staged. If you want just drive with less building efforts - 440cc at head would be OK.

[fphil]

I have increased the accel enrichment to dTPS 3/10/33/150 with % 5/40/60/120, but I'm still seeing quite a swing from lean to rich on acceleration. I am also

btw, for what reason those % are computed  from the req. fuel (ms) parameter (engine set up) and  so are independent of the VE values

[GintsK]

VE values? VE values for speed density is almost constant... don't knew...
There is fuel film values what is PW dependent. Try those.

[se7ensport]

Progress, but settings confirmation needed:

I now have 215cc injectors in the head and 443cc in the throttle bodies, I have set the thresholds for secondary injection as 25% tps and 1700rpm.

What I would like to understand is how the actual fuel injected is calculated and should the thresholds used be the same as figures the VE table.

Example: Using only 440c injector the RPM/TPS table at 25%TPS the amount injected goes from 100 at 1500rpm to 110 at 1700rpm, and at any point between the two figures VEMS calculates the required fuel between the two i.e. at 1600rpm it would use 105. 

Now with two set of injectors (215c primary and 443c secondary, which gives a total of 547c once second injectors are triggered) and the staging set to 25% and 1700rpm I calculate the table to become (roughly) 200 at 1500rpm and 80 at 1700rpm.

So what does VEMS do at 1600rpm??? My concern is that it would interpolate a figure of 140 but only use the primary injectors as the trigger threshold for the second injectors has not been passed.

Do I need to use threshold figures that match the X and Y axis on my VE table? 

We'll I got the above totally wrong, VEMS manages the second set and the 'VE table has its regular shape, I had mistakenly thought the table would drop in values as the second set came in.