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Discussion Starter #1 (Edited)
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:
- O2s
- CPS
- TPS
- 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.
 

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Discussion Starter #2 (Edited)
Wondering if it's not a software issue is it possible the Aeromotive pump could affect the factory fuel regulator and that leads to AFR drop? I've never replaced the regulator, should I give a try?
 

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Wondering if it's not a software issue is it possible the Aeromotive pump could affect the factory fuel regulator and that leads to AFR drop? I've never replaced the regulator, should I give a try?
That is a crazy graph, no doubt. The problem with the stock ECU is you never really know what's happening or if some unknown table is kicking in.

I'm not sure how a hardware issue could cause this set of conditions repeatably, but replacing the regulator is cheap and easy so it's worth a try. Also check to ensure the vacuum reference line to the regulator is hooked up, both at the regulator and at the engine.

Do you have a graph of the timing throughout the pull? Would be good to see if the ECU is pulling timing, which might indicate a knock sensor going off.

Good luck. Dealing with these issues with the stock ECU can be infuriating.

--Peter
 

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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:
- O2s
- CPS
- TPS
- 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.

Regards,
Jerry
 

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1. Who is tuning your car?
2. It could be the dyno, I had similar experience
 

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Discussion Starter #7 (Edited)
That is a crazy graph, no doubt. The problem with the stock ECU is you never really know what's happening or if some unknown table is kicking in.

I'm not sure how a hardware issue could cause this set of conditions repeatably, but replacing the regulator is cheap and easy so it's worth a try. Also check to ensure the vacuum reference line to the regulator is hooked up, both at the regulator and at the engine.

Do you have a graph of the timing throughout the pull? Would be good to see if the ECU is pulling timing, which might indicate a knock sensor going off.

Good luck. Dealing with these issues with the stock ECU can be infuriating.

--Peter
I will do my best to get a graph with timing too.

can you map the actual cam position vs rpm and correlate it to the AFR graph?
Yes, it possible. Will do.

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.

Regards,
Jerry
That's right. The black line shows the AFR.

CPS were replaced with OEM.

Fuel pump sits in the factory bracket so I'm sure it's fixed well.

We're using meth just for cooling and safety. The problem occurs with meth ON and OFF, no difference.

AFR is still around 11s for safety reasons at least until we catch what causes the drop after 6000 rpm.

1. Who is tuning your car?
2. It could be the dyno, I had similar experience
The tuner is a local guy here in Bulgaria.

The problem occurs both - on the road and the dyno. On the road I just can feel power loss when the AFR drop hits.

Thank you guys for all guidelines. I will follow your advices and get back to you with results. Meanwhile if anyone has a tested tune for mine or similar setup (at least these injectors) so I can check if it's a software issue would be awesome (not for free of course).

Alex
 

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I'm not sure how a hardware issue could cause this set of conditions repeatably, but replacing the regulator is cheap and easy so it's worth a try. Also check to ensure the vacuum reference line to the regulator is hooked up, both at the regulator and at the engine.
I'm more curious as to why there's a spike and then a dip. I wonder if the stock FPR is functioning properly. How much boost can the stock FPR handle and still work correctly?
 

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Have you tested the Vanos?

If the car ran fine before SC then it’s the tune or the tuner.
 

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Discussion Starter #10 (Edited)
Have you tested the Vanos?

If the car ran fine before SC then it’s the tune or the tuner.
Yes, we've done vanos test before SC and worked fine. But Will do it again...

I have a dyno graph before the SC with one bad CPS, but after replacing I haven't dynoed again. I noticed two of three runs the car has had too low power peak in the RPMs (6300 instead of 6600). Is it possible the bad CPS caused that effect?

 

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It’s rare for TPS sensor to go bad. I’ve experienced failure of the aeromotove pump when it gets hot.
 

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Discussion Starter #15 (Edited)
I could try to get back to the original fuel pump but because it's runnig rich and not lean makes me think the fuel pump is not a problem. I'm going to replace the fuel pressure regulator first, although I can't explain myself how a bad regulator or something bad in the fuel system at all could cause running rich irregularly? When the FPR fails it not regulates the fuel pressure correctly and makes more fuel to pass than it should be, am I right?

The only one constant is the problem appears after similar RPMs every time.

Anyone has an idea what else from mechanical side would be good to be replaced?
 

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I could try to get back to the original fuel pump but because it's runnig rich and not lean makes me think the fuel pump is not a problem. I'm going to replace the fuel pressure regulator first, although I can't explain myself how a bad regulator or something bad in the fuel system at all could cause running rich irregularly? When the FPR fails it not regulates the fuel pressure correctly and makes more fuel to pass than it should be, am I right?

The only one constant is the problem appears after similar RPMs every time.

Anyone has an idea what else from mechanical side would be good to be replaced?
Unless I am not reading your graph correctly, it looks like it is running rich AND LEAN. There are two "spikes", one up and then one down. So it looks like it goes very lean (upwards spike) , then very rich (downwards spike). Perhaps it is the lean condition causing the problem? When it goes so lean, the computer is overcompensating and you get the momentary richness until the computer catches up? (remember, no O2's online during WOT). Computer should really react faster though. Can you hear any noise when it goes lean? Any knocking?

Since it happens at a certain rev range, I keep thinking less fuel pump/FPR and more CPS/Vanos. Something that causes a running change. Cam timing would do that. Have you run the Vanos test on the computer?

Regards,
Jerry
 

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Discussion Starter #17 (Edited)
Unless I am not reading your graph correctly, it looks like it is running rich AND LEAN. There are two "spikes", one up and then one down. So it looks like it goes very lean (upwards spike) , then very rich (downwards spike). Perhaps it is the lean condition causing the problem? When it goes so lean, the computer is overcompensating and you get the momentary richness until the computer catches up? (remember, no O2's online during WOT). Computer should really react faster though. Can you hear any noise when it goes lean? Any knocking?

Since it happens at a certain rev range, I keep thinking less fuel pump/FPR and more CPS/Vanos. Something that causes a running change. Cam timing would do that. Have you run the Vanos test on the computer?

Regards,
Jerry
The uploaded graph is random - just one from many while we were still in the tuning process. I've got graphs without runing lean, we were able to fix it but running rich is most of the times and that's what interferes us to do a final tune.

We've done vanos test recently but looks like will need to do again just for double check.
 
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