[Dmacc]

I need some help here.

Lately my car has been a little sluggish whether tuned or not. I had been chasing vacuum leaks, and even re-serviced my forge DV's because they were sticking. I logged the car today on the stock tune, I noticed throttle closures and timing drop outs. I am on 91 Octane and the car was up to temp, it was also hot today, but the IAT's look good to me. Could it just be the piss poor 91? The car has felt like this for numberous tanks, I only run Chevron.

AR kittyless dps
bmc dci
ER chargepipe
Forge DV's
7" ETS FMIC

New plugs and injectors 1k miles ago, 52k miles, original coilpacks, lpfp, and 02 sensors.

Thanks for looking!

http://www.datazap.me/u/dmacc/stock?log=0&data=1-2

[135Pats]

Dang the throttle is really stabbing. 91 is never a good starting point, could well be the cause of those timing dropouts.

Quite lean for pump gas IMO, though it richens up top.

[Dmacc]

Originally Posted by 135Pats

Dang the throttle is really stabbing. 91 is never a good starting point, could well be the cause of those timing dropouts.

Quite lean for pump gas IMO, though it richens up top.

I was thinking the same thing, but this is the stock tune. I was thinking possibly 02's as a culprit. I know I've had tons of smoke pour out of my exhaust in the past due to oil, but I'm not really sure what else would explain the high afr on the factory tune. Unless of course it's normal.

Another thought: I'm using my yellow springs in my forge dv, they are meant for tuned psi levels, could they be too strong for the stock tune?

[Tiago@VRSF]

What tune are you running?

You're definitely too lean for 91 although you could almost get away with it considering how little boost you're running.

[Tiago@VRSF]

Originally Posted by Dmacc

I was thinking the same thing, but this is the stock tune. I was thinking possibly 02's as a culprit. I know I've had tons of smoke pour out of my exhaust in the past due to oil, but I'm not really sure what else would explain the high afr on the factory tune. Unless of course it's normal.

Another thought: I'm using my yellow springs in my forge dv, they are meant for tuned psi levels, could they be too strong for the stock tune?

The spring won't matter, it'll just keep the BOV closed with a bit more force which won't cause any sort of throttle closure. It's probably not a good idea to run FBO without some sort of tune to be honest.

[Dmacc]

Originally Posted by Tiago@VRSF

What tune are you running?

You're definitely too lean for 91 although you could almost get away with it considering how little boost you're running.

Any ideas as to why I could be so lean? I've just replaced all 6 injectors, and my trims seem to be relatively in check. Too much airflow for the stock tune because of being FBO?

[Allen@MOTIV]

Originally Posted by Dmacc

Any ideas as to why I could be so lean? I've just replaced all 6 injectors, and my trims seem to be relatively in check. Too much airflow for the stock tune because of being FBO?

The N54 is 100% closed loop so any increase in flow will be taken care of on the fueling side by the DME(within reason, of course.) The DME isn't throwing a lot of fuel at it through trims so it may be possible the AFRs are where the tables want them. To be honest, it has been a long time since I've reviewed the stock BMW tune but I do know it runs considerably lean.

The free flowing bolt-ons however can definitely be the source of throttle closures on cars running the "stock" tune. FBO cars breathe much better than a stock car and typically require less DC and that can easily result in throttle closures.

Just looking at one cylinder makes it hard to tell just how bad the timing is but timing corrections on the stock tune can be common especially on lower grade fuels.

[Ilma]

Originally Posted by Dmacc

Any ideas as to why I could be so lean? I've just replaced all 6 injectors, and my trims seem to be relatively in check. Too much airflow for the stock tune because of being FBO?

I just checked the stock AFR tables and you are pretty much following it.

It specifies an AFR of 13.5 at 4500rpm dropping to 12.3 at 6000 rpm.

Your throttle closures are probably getting actual boost back up to target since they seem to happen when your boost gets about 0.5 psi below target.

Guess the stock DME doesn't allow for much boost target error .

I think Tiago is right......having FBO reduces pressure drop across the intercooler and exhaust, so the stock wastegate duty cycles are not going to be a good match for stock boost levels.

[Dmacc]

Originally Posted by Allen@PTF

The N54 is 100% closed loop so any increase in flow will be taken care of on the fueling side by the DME(within reason, of course.) The DME isn't throwing a lot of fuel at it through trims so it may be possible the AFRs are where the tables want them. To be honest, it has been a long time since I've reviewed the stock BMW tune but I do know it runs considerably lean.

The free flowing bolt-ons however can definitely be the source of throttle closures on cars running the "stock" tune. FBO cars breathe much better than a stock car and typically require less DC and that can easily result in throttle closures.

Just looking at one cylinder makes it hard to tell just how bad the timing is but timing corrections on the stock tune can be common especially on lower grade fuels.

Thank you for the explanation, Allen. It cleared up a lot of questions I had. I will get an appropriate tune asap!

[Dmacc]

Originally Posted by Ilma

I just checked the stock AFR tables and you are pretty much following it.

It specifies an AFR of 13.5 at 4500rpm dropping to 12.3 at 6000 rpm.

Your throttle closures are probably getting actual boost back up to target since they seem to happen when your boost gets about 0.5 psi below target.

Guess the stock DME doesn't allow for much boost target error .

I think Tiago is right......having FBO reduces pressure drop across the intercooler and exhaust, so the stock wastegate duty cycles are not going to be a good match for stock boost levels.

That's comforting, thanks for the info man. I will switch up the tune.