Guys, we're in a process of tuning my supercharged M5 but we have an unknown issue - sometimes (irregularly) the car running rich after 6000 RPM. AFR just drops suddenly from 11s to 9s. We did runs in 3th and 4th gear, with meth injection ON and OFF, also with two different AFR sensors. Tuning guy revised the tune so many times but still he can't find an issue. I already believe something from the hardware could cause this. Here it is the setup.
ESS kit with 92mm pulley, custom tune, Bosch Green Giants 42lbs injectors, SS mufflers, SS x-pipe, Magnaflow cats, stock headers, RK Autowerks plenum plates, RK Autowerks carbon fiber plenum cover, Aquamist HFS-3 meth injection, achieving strong 8-8.5 psi of boost. All new:
- Fuel pump Aeromotive 340 lph
- Fuel filter
- No codes after diagnostics
And this is the dyno graph:
- the black line shows AFR
- the upper red one shows power
- the lower red one shows boost
We tried almost everything but now every idea is gone so if you have something in your mind please share.
I am having a little trouble reading the graph. Is the black line for AFR the one that starts way in the upper left hand corner? It then comes down, spikes UP then spikes DOWN. Is that your AFR line?
Ignore O2, they are off line during WOT.
I assume you replaced CPS with new style, known vendor. The fact that is intermittent seems to rule out mechanical issue. Those things either work or don't work.
If the fuel pump correctly seated? Is it possible it is not and therefore shifting around?
Are you tuning meth for power or cooling? If the latter, then hitting the meth should richen up your AFR's a bit over running without meth. Any difference in readings?
Finally, when I did my tune a couple of years ago, the tuner said the prior tuner had used a very old BMW base program from the original tune. The old tuner simply tuned on top of that. So while it was OK, it was not smooth or consistent. So my new tuner wiped that out completely, it was over 10 years old. Then he proceeded to put in the latest BMW tune and the his tweaks on top of that. And he tuned the meth for power. Tune was done live on a dyno, which is my preference. The new tune is lights out!!! So you may want to ask your tuner what he is using for the base BMW program.
BTW, I think 11's are a bit on the rich side. You should be shooting for low to mid 12's.
Dinan Stage 3 suspension, SS jet coated headers, ESS SC kit w/ 1 range colder NGK's, 92mm pulley, 440 Big Greens, TTFS alpha N tune for meth, RK plenum plates, SBC Endurance Stage 3 Kevlar performance clutch setup, "Jed" lightened DMFW, open brake ducts, TEC cupholder, U.S.(Euro style) tilt/slide armrest, 6k HID fogs, Umnitza bi-xenon flamethrowers w/6k super white low beams, rear fogs, V1/Stealth1, dual head LI, 2.65 diff w/40% lockup/2x dynamic, compact spare, M5 logo trunk carpet, Euro trailer hitch, Mocal oil cooler, ACS type rear spoiler, Rogue custom SSK and tranny mounts, ST 355 BBK (fronts), BP sway bar brackets, Bluetooth retrofit, Speedhut boost gauge (20 psi), Dinan TB's and VS, KB BAP, Howerton/HFS-3 Aquamist WI trunk setup (50/50), with 2nd gauge in rear view mirror, aftermarket trunk mounted sound system integrated into stock unit (amps, crossovers, sub and speakers).......
Last edited by gsfent; 10th October 2017 at 12:58 AM.