Playing with the AEM piggyback on C200K

[piko]

Hi!

My C200K has a 220mm crank pulley installed. I wasn't satisfied with how it ran with the stock ECU.
From 3500 to 5300 afr's would climb from 12.5 to 13.9. Not good....
I installed 12% bigger injectors and after the the fuel trims settled the afr situation was the same as before but with big negative LTFT's.
I then installed a new Pierburg maf and again the same, but my LTFT went under -25% and triggered a cel.
Then refitted the stock injectors along with a 4bar FPR and waited for the fuel trims to settle and again the AFR's stayed the same.

With the bigger pulley I get a good 0.8 bar of boost in higher revs, but I could feell the car wasn't giving it's best given the lean AFR's and the ECU pulling timing.

So I decided to install an AEM piggyback controller.

Started just with dataloging as was with no corrections. In closed loop AFR's are spot on, so corrections will only be need in open loop at boost above 0.4bar.
The negative fuel offset from 3500 to 5300 is really strange as you can see from the graph. I more or less ironed it out later on with aditional fuel trimming. My final AFR at WOT is just over 12 and power increase is very noticable along with a healthier sound from the engine when timing is not beeing pulled.
I'm used to tuning Volvo 5 cylinder turbo engine which produce one of the best engine sounds BTW .



I had to clamp the MAF signal to the ECU at 4.69V to prevent fuel-cut at 4.8V. The fuel-cut really kicks in hard, much harder that the rev limiter.

Now that I am able to watch injector duty cycle much is clearer now. Fuel cut is where standard injectors reach duty cycle of 100%.

The 4bar FPR adds just a good 4% of fuel thus barelly at 100% duty cycle allowing the engine to run at AFR of 12:1 up to the rev limit at 0.8bar.

When I install bigger injectors and trim the fuel I'll have it dynoed.
I'm shure it will clear all the talk about how much power the stock injectors can handle with the 4bar regulator.

I can tell you imediatlly that even with the 4bar FPR they can barelly handle a 220mm crank pulley.

[KrumB]

Hello,

Very interesting thread!

I'm using a phone app to measure HP. It works quite good if used properly.
Here's a link:
http://www.perfexpert-app.com/en/

It will give you a pretty good idea where you are.

Please keep us posted.
Cheers

P.S.
It will be very useful if you can post copies of the logs (AEM data file) with and without corrections!

[piko]

The logs dont look much different appart from the leaner 3500 to 5300 range, which I have no idea why happens.
I'm adding around 20% fuel in that part and around 15% before and after.

[KrumB]

One more question....
Do you have a way to log the factory ECU and if yes can you log the knock control?

[piko]

One more question....
Do you have a way to log the factory ECU and if yes can you log the knock control?

You can log two parameters at a time with resonable rate with a ELM327 interface and some OBD software.

Best way to log with RPM and igniton or load or MAF g/s or ignition retard.
But I'm waiting for a new interface because mine stopped working.

The next thing I found out today is that the MAF stops increasing voltage at 4.83V athought the revs and boost keep increasing.
So 0.79bar (11.45psi) boost is where the MAF is maxed out but mine keeps climbing to 0.83bar (12.04Psi) just before the limiter.

I have a feeling It would be possible to get a decent power increase by raising the limiter and maybe retarding the exhaust by a few degrees. I might need to get me some 350cc injectors.