Realcanuk

Can you post a pic of the tube and maf placement?

RealQuick

iTrader: (14)

ill take one and post it up later. Keep in mind, MAF and placement is unchanged from previous setup.

RealQuick

iTrader: (14)

rpm vs time attached.... you can see rpms fluctuating, which might be the cause of the MAF readings fluctuating.

RealQuick

iTrader: (14)

Shot of A/F versus rpm. Look at the lines that connect adjacent data points to each other. You can see the rpm fluctuations reflected in the A/F jumping around.

RealQuick

iTrader: (14)

MAF vs rpm... you can see the rpm fluctuation appears to be messing with the AMF readings.

So... perhaps clutch slippage is causing this, or perhaps blowout?

I theorize that perhaps its the clutch slip unloading the motor/turbo, which changes the MAF readings (which changes the A/F readings).

RealQuick

iTrader: (14)

Here are two screen shots of another run on the dyno where slip was much more visible. I circled rpm and mph in each pic.

RealQuick

iTrader: (14)

Pic attached.

pantera_efi

iTrader: (1)

Hi, I believe your ARF is too Rich (rich miss-fire), these depends on the UEGO Meter used, many read different such as Innovate with a -1 AFR report often.

I use EGT to help with the AFR requirement.

What are your EGT's ?

Lance

RealQuick

iTrader: (14)

Lance, thanks for the reply. I am not sure of the EGT as I dont have a sensor in place.

If my WB was off, then the dyno's WB would have to be off as well correct?

Where the issues were happening, the dyno A/F has me between 11.5 -12.5 A/F, while my WB showed 10.6-11.3 A/F. I expect the WB at the tailpipe to be leaner (typically 0.5 A/F leaner, but my cutouts were open for this run). You are implying that perhaps I am even richer than 10.6-11.3? I dont know if I buy that, but it is something to certainly consider. I will say that at idle/part throttle, the fuel trims from the NB readings align with my WB, so the WB would have to me malfunctioning at WOT only.

EDIT *** I have the AEM Failsafe WB*****

Realcanuk

MAF placement doesn't look bad, although that big bend right after could be having some effect. Maybe try tuning SD and see if the problem disappears just to rule the MAF out.

kingtal0n

iTrader: (1)

If you have any proof at all that the clutch is/was slipping then that should be taken care of first before anything else in my opinion. I didnt realize you had substantial evidence of that, and yes it can and will definetely alter engine flow rate if the rpm slips up and then back down again, both in terms of turbine/compressor rpm and the engine flow rate itself, and it may "rubber band" the airflow (more and then less) which may cause a stall condition at the maf sensor (you see the maf reduce voltage/frequency when the air stalls, such as during surge condition).

RealQuick

iTrader: (14)

I 'll cruise around some more, try and get some heat into the clutch. I'll do some street pulls at 8psi and see if I still get MAF fluctuations. If I do, I'll export the log to excel again and see if the rpms flutter again. I could try speed density and repeat the process. The clutch is definitely slipping (I aborted a couple runs because it free rev'd after the hit on the dyno. As I made multiple back to back pulls it started to hold better (but clearly not 100%). I may order a fresh WB sensor too.

I created this pos t because of my research online that showed similar dyno graphs with spark blowout, so figured I'd ask. Clearly the clutch is slip is muddying the diagnosis up. I do appreciate everyone's input on this.

pantera_efi

iTrader: (1)

Hi Quick, the AEM "read" is found by most as ACCURATE.

What is the sensor location, if before turbine, as the "read" IS effected by EMAP ?

You can "melt" a piston crown with too little Spark Advance AND too much Fuel.

That case is found by observing EGT.

I am able to "clean" a Hot Wire sensor by removing the duct, then to spray some CarbKleen.

MAKE SURE it's cool first, NOT with Key ON.

I have seen cases that allow a baffle to be installed in the air tube before the MAF, this will stop the air "spin".

Lance

RealQuick

iTrader: (14)

lance, thanks for reply.

WB is downstream from turbo in the DP, probably 40" away.

i am running 12 deg @ pk torque and 15 deg at peak power at 16psi.

Ill give the sensor a cleaning. I am gonna go back and look at old logs with the old clutch to see how the MAF readings were

RonSSNova

iTrader: (3)

Had my buddies TT C10 on the dyno with the same meth setup. Plus 93
We tried the suggested 10.8:1 AFR.
It wasn't happy.
It was quite happy at 11.5-11.7:1

RealQuick

iTrader: (14)

i looked at the log from the smooth dyno curve and the MAF readings are choppy as well. The difference is the choppy curve keeps moving to the right (where with the funky graph I had MAF readings going left and right as you can see in one of the pics above).

therefore, even on smooth dyno graph I still see I have MAF fluctuations. While it didn't cause any issues before, if I want to address it in the future, I'll need to work on a flow straightener or go speed density as you mentioned.

Short term, I need to get more heat into this clutch and see if I can get it to fully grab.

RealQuick

iTrader: (14)

last time out I noticed that it was a little choppy below 10.0 AFR. Once I got above 10.0, the curves smoothed out. On the smooth dyno curve from before, I had AFR range from 10.7-11.2 and it seemed to like it. I am still on stock bottom end, so I don't want to push it too much.

Dian

why do you run a maf?

blowout = missfire. afr should reflect that, no?

RealQuick

iTrader: (14)

i learned to tune my car when it was N/A, and used the MAF then. Got used to tuning with it and didn't find a need to change.

my AFR does show a reaction (leaner) in the area of concern, just not substantially leaner.

RealQuick

iTrader: (14)

Pulled the plug wires and found 4 out of the 8 were cracked. So with new plugs/wires and if clutch will hold, I should be able to improve on the 817rwhp.