E6K Tuning tips...
 

Have run into a couple of speed bumps on my long learning how to tune journey and wanted to know if you guys had any pointers for me.

Problem one: lean secondary transition, worse the colder the engine is. Using 550/1600 injectors. Is this just the nature of the beast or is it possible to smooth this out?

Problem two: WILD boost fluctuation from 3,500 to 4,000rpm at WOT in 3rd gear and above. Boost flys back and forth from 10psi to 20psi, can hear the BOV venting and closing in fast succession. Is this a tuning issue or something else? 1st and second gear are fine, above 4,000rpm is fine.

Any input would be great :]

You don't exactly want to be hitting the transition point when cold... that means you're stomping on the gas and boosting on an engine that isn't fully warmed up. Big no no...

Anyway, how bad does it lean? Enough to cause a hesitation and feel it? I run the same injector combo. I get a lean spot, but not enough to physically feel; I only see it on the wideband. Things to try: split the fuel feed to serve both rails; use a Y fitting. Try upping fuel pressure. Finally, try moving the staging point down 1 or 2 bars.

FWIW I run a little over 40PSI base fuel pressure, maybe around 43. I stage my injectors at bar 11, that's 1 before the 0/0 pressure bar on the map.

As for the 3500-4000RPM area... I have no idea what's wrong. How can you even make 20PSI at that RPM?

WOT isn't needed to transition the secondaries, I have it set to engage above 0psi. 1/4 throttle with the engine "warm" will make it stumble (showing around 15-16afr) before catching itself and running normally. It becomes less noticeable as the entire motor starts to come up to temp and the fan starts to cycle.

I've read other people having similar boost fluctuations after reflashing a tune on a newer car which makes me think it's something tune related.

You need to go through all the rpms and smooth out the transition point, Can't remember exactly what equation I used but I was having a similar issue about 4 years ago(when I had a E6K on my rx7) and I used it to smoothen out my transition. It took me a while though. Patence is key with this setup.

Move the transition point up to positive manifold pressure as long as the primary injectors will support it. You want the transition to be at a high enough load that you will not be all over it in normal cruising conditions. At 0 psi that is exactly what will happen.

To get it smoothed out, since it's lean, simply add fuel to the bars before and after the transition. I usually end up with the first bar after the transition being more pulse width than the 2nd bar after the transition. A load bearing dyno will make this easy as you can run the engine right on the transition and back and forth across it to get it just right. On the street it's a lot of trial and error.

What are you using for boost control? I'm guessing, if you're running the hybrid turbo in your sig, that you getting turbo surge. It's common with these hybrids. Really nothing you can do about it other than to swap to a different turbo.

I'll try moving it up a cell and see what happens, was considering doing it but wanted some input, thanks guys. I tried adding some fuel around the transition but it seems like it just ends up being way too rich if i transition slowly. Was messing with throttle pumps too but they didn't seem to have any affect on this issue.


I'm using a hallman MBC. It could just be surge, I didn't have these problems when I ran less boost pressure. Was only able to run around 15psi on my old exhaust setup, upgraded to full 3" and added water injection...but if i'm asking too much from the turbo then i'm just asking too much :[

Turned the boost down to 15psi to see if the surge would go away...nope. Starting to wonder if it's because of my compressor wheel. Ate the original and replaced it with an 8 blade unit from china, could the compressor wheel be that different from the original 7 blade to cause all this surge?