Katech Stage 2 engine : DFCO transition not smooth, strong engine braking, weird...

[Sachs]

Guys,

I'm currently finalizing my tune on the Katech engine I installed myself on my C7 GS. Car made 552WHP/489 WTQ on E80 (Katech LT1 Torquer cam, PSI 1511 spring, Katech ported heads, E85). Right now I'm working on driveability. Overall it is superb except few details below.

I'm having an issue with the DFCO

The transition between gas release and DFCO is not smooth and consistent.

Sometimes after a full throttle when I let the gas the engine goes in DFCO right away. Sometimes it does like stock (coasting for few seconds, then DFCO) but the engine braking comes strong and with a strong transition, and engine braking seems stronger than before...

I also noticed than when I do a quick full throttle between 2-3000 rpm and release quick, my lambda goes to 0.55 !! and the car never goes to DFCO, then when I take the gas there is a significant misfire (obviously way too rich at 0.55 !!). It does not happen if I floor above 3000 rpm. If I'm smooth it does not happen.

I did not log the issue yet. It seems to me in MAF mode this issue is not there (I'll double check tomorrow) but the DFCO issue mentionned earlier is there. I'm wondering if there is not a transient issue in my VE tables and I'm wondering if there would be a correlation with my DFCO issue and this one...

So some questions :

- Is there a way to smoothen the transition between coasting and DFCO
- Is it possible to go directly to gas to DFCO without this transition ?
- Would a messed up VE table on the very low value (0.10-0.14) create the second issue mentionned ?

Thanks for your help

[Sachs]

So I confirm second issue is absent in maf only mode, so my VE tables in the 0.12-0.16 is probably messed up. I need to retune my VE again for those ranges

[Sachs]

Putting back my min and long spark table to stock (except 0.08-0.16) solved my dfco transition. I'm really surprised how much impact this table has on dfco transition

[TriPinTaZ]

The Minimum Spark Tables is the floor for Torque Management Advance. It can really screw up drive-ability if you're not careful.

[Sachs]

Indeed !