MAF readings

[mdegracia]

Hey Guys,

I picked up a Ross-Tech and have been doing some logging.

Had a question for the group:

My bank 1 (Is this the driver side?) MAF readings are within spec, but lower than Bank 2.

@ idle about 1 g/s less
@ WOT anywheres from 20-40g/s less

In general, even stepping on the throttle, the Bank 1 MAF readings lag significantly behind the Bank 2 readings.

I have swapped the postition of sesnorsto determine if it was the a bad MAF, but the reading differential was still with Bank 1. I have pressured test and smoke tested the intake system sans airbox. Found a leaking intercooler. Fixed that and tested a again. Everything tested out fine. So that left me to thinking the MAFs seals were faulty...installed the Apikol pieces and the MAF readings at idle are the still off!

Also, I am getting the TCS light during WOT pulls and I see the tach dipping and catching itself several times during the pull w/o wheelspin...

Thoughts?

Matt

[hahnmgh63]

Something to do with the intake design (location, plumbing bends, slight differences in diameters of plumbing) Bank 1 (drivers side) usually always reads less than Bank 2 and your posted differences seem to be well within spec. Posting the actual logs will better determine how the overall flow is doing but 20~40g/s is pretty good tolerance. The ESP light flashing is a common problem with the RS6, I sometimes get it too and it may just be the sensitivity of the system. I've never had a Vagcom error with mine but it is suspect. On an agressive dry road run I just turn off the ESP.

[mdegracia]

Thanks!

Just while in Park, stepping on the throttle and letting off, the Bank 1 MAF reading will zero out immediately while Bank 2 will gradually return to idle. Is that considered normal?

I guess I was just expecting more "pop" with the REVO tune. Looks like I am going to have to play with the settings. Hmmm, I will be Chicago end of the month, maybe its not too late for a Eurocharge tune instead....

Yes, I will post some log results. I did a few initial pulls in 2nd through 4th. Are those usable or are forced 4th gear pulls prefered?

[Chung]

I had similar issues. Mine were a result of bad MAF wires.

[Brav]

I had similar issues. Mine were a result of bad MAF wires.

How did you fix it? DIY?

to the OP - yes, its normal. Mine does this as well. Not sure about the delay to zero however.

[mdegracia]

Sweeeet....
Any advice on where to setup the other terminal for continuity testing?
And what are my alternatives? Cut and splice?

Thanks,
Matt

[Chung]

My original intention was DIY but I got lazy. I just paid my local technician to splice in new MAF wires. My wiring had already been redone but the reworked wiring failed.

It was $600 for both sides plus the new seal install.

[mdegracia]

Ok took a loook at the MAF wiring. I saw no signs of fraying or damage. Readings at each terminal mirrored both banks. So I think I can rule out the wiring as the fault.

Also, while running the car in the garage with the MAFs in place, I disconnected the harness from the passenger side bank and the Bank 1 reading went to "0", so Bank 1 is actually the passenger side for US.

I swapped DVs as my last saving grace...no change.

What else can be left to check? What other sensors are the MAFs dependent on, if any?

I am running the Revo stage 2, so the front O2 sensors are deleted, besides, that I am not getting any DTCs for the O2's.

[ben916]

now I am mixed up: Bank 1 Bank 2, etc. I seem to remember that speedtrapped had a MAF issue similar to this ^^^ and for some reason the MAF connections at the firewall were reversed, not sure it will help. Hope he pipes in...

[mdegracia]

Interesting, I am pretty sure the mafs are matched up to corrct harnesses...they are extremely short so not much play.

I just did a quick run and maf readings are way off. 20-40 g/s versus 120-130 g/s for banks 1 and 2, respectively! Only until engine load gets above 100% dies bank 1 start to catch up and only be off 20 -40 g/s....

[lswing]

I guess I was just expecting more "pop" with the REVO tune. Looks like I am going to have to play with the settings. Hmmm, I will be Chicago end of the month, maybe its not too late for a Eurocharge tune instead....

You should be getting a big jump in power with that tune, something else might be off. I'm running the Revo, and believe it's stage 2 or at least has the boost turned up, it's a frickin' rocket! It was on the car when I purchased. Got even better when I fixed up the IC's. It still wants more so I'm adding the water/meth kit as we speak...good luck there! Are you meeting full boost? What is the expected boost in your logs?

[mdegracia]

Around 1600-1800mbar...nothing near the 2000 range...

There has to be something off on that passenger side bank. I did disconnect the passenger side wastegate to seperate the trans and engine...im wondering if I need to tighten up the flapper. I can't remember if I did that or not! Farck!

[hahnmgh63]

The only difference in what Revo calls the Stage 1 & Stage 2 is that the Stage 2 has the "REAR" O2 sensors coded out. Revo software is adjustable with the SPS Select tool for Boost & Timing but the basic Boost & Timing for both versions is the same.

[mdegracia]

A brief log under 30,000 characters!

Engine Speed	Engine Load	Mass Air Flow	Mass Air Flow		Engine Speed	Engine Load	Boost Pressure	Boost Pressure
(G28)		(G70) Bank 1	(G246) Bank 2	TIME	(G28)		(specified)	(actual)
/min	%	g/s	g/s	STAMP	/min	%	mbar	mbar
4280	118	100.72	125.31	9.46	4280	117.3	1570	1350
4320	118	104.17	126.39	9.55	4360	118.8	1570	1340
4400	118	107.31	132.03	9.66	4440	118	1580	1350
4480	118.8	110.47	130.03	9.77	4480	118.8	1580	1360
4560	119.5	111.92	131.06	9.88	4600	118.8	1590	1360
4600	119.5	115.94	134.78	9.97	4640	119.5	1600	1360
4680	120.3	118.25	139.33	10.08	4680	121.1	1600	1360
4760	121.1	121.14	137.72	10.19	4800	124.1	1570	1360
4840	122.6	121.97	145.22	10.3	4880	123.3	1560	1370
4920	122.6	124.11	146.78	10.41	4960	122.6	1550	1370
5040	122.6	132.25	153.03	10.52	5040	123.3	1560	1380
5120	123.3	137	153.03	10.63	5160	124.1	1570	1380
5200	124.8	137.17	155.72	10.75	5240	122.6	1490	1400
5280	127.8	141.33	158.08	10.86	5320	127.1	990	1360

[mdegracia]

a little before so that you can see the MAF lag...

Engine Speed	Engine Load	Mass Air Flow	Mass Air Flow		Engine Speed	Engine Load	Boost Pressure	Boost Pressure
(G28)		(G70) Bank 1	(G246) Bank 2	TIME	(G28)		(specified)	(actual)
/min	%	g/s	g/s	STAMP	/min	%	mbar	mbar
3000	90.2	26.44	103.11	7.55	3040	91.7	1550	1150
3120	93.2	29.5	108.06	7.65	3120	94.7	1600	1170
3160	95.5	30.08	111.92	7.74	3160	95.5	1590	1200
3200	97	32.72	114.39	7.84	3240	97	1600	1220
3280	98.5	34.67	117.78	7.93	3280	100	1600	1250
3360	102.3	40.39	120.25	8.02	3360	102.3	1590	1260
3400	103.8	46.31	119.19	8.12	3440	104.5	1590	1280
3480	106	52.44	116.06	8.21	3480	106	1570	1280
3560	106	58.22	113.97	8.3	3560	106.8	1570	1290
3600	108.3	62.81	117.17	8.4	3600	109	1570	1300
3640	109.8	68.06	115.86	8.49	3680	109.8	1570	1310
3720	110.5	69.92	116.64	8.58	3720	110.5	1560	1320
3760	111.3	75.44	114.83	8.68	3800	111.3	1560	1320

[TozoM8]

Bank 1 pass side, bank 2 driver's side. Make sure your intake is seated on the mafs and there is no leak. You could swap the mafs to see if the lower reading goes to the other side.

[4everRS]

Those are stock numbers. Your bleeding boost somewhere. And yes, that's a pretty big difference in mafs in low Rpm's but alright in higher.

[mdegracia]

I actually swaped the MAF sensors around, no change.

I also removed the MAFS from the air box and installed them directly in the TB to insure a positive fit, same results....

I am really starting to think I didn't fully seat the wastegate flapper. It can't be more than a 2-3 threads open though!