djamps

iTrader: (1)

Well I got my PMAS about a year ago (right about when they became practically unavailable) and it has crap resolution at idle. In fact with engine off it still shows about 0.7 volts and voltage slowly drops at WOT gear after gear at the 1/4 track. you can see the voltage actually go backwards in the logs as RPMs increase on a hard pull. Not only that, but it seems every PMAS has different transfer functions down low so by replacing it you have to rework some of the tune. I was able to 'tune around' the idle stuff for the most part but it's still nothing like stock.

Massairdirect

As I said, you can have more resolution down low by using more data points in the lower half of the curve. The voltage with the car not running is unreliable, the sensor needs air moving across it to start reading.

.7V is only about 4 KG/HR, way below anything seen entering any engine aside from a lawn mower so that makes sense.

1.1V is a lot closer to what you should be seeing at idle.

Here is the idle portion of the HPX transfer function.. As you can see, a very small voltage change will show a very small change in flow.

2.9" I.D. Tube
Volts Flow Kg/HR

0.88 6.07583
0.89615686 6.682653
0.91231373 7.306136
0.92847059 7.947277
0.94462745 8.607071
0.96078431 9.286515
0.97694118 9.986604
0.99309804 10.70833
1.0092549 11.4527
1.0254118 12.22069
1.0415686 13.01331
1.0577255 13.83155
1.0738824 14.6764
1.0900392 15.54886
1.1061961 16.44991
1.1223529 17.38057
1.1385098 18.34181
1.1546667 19.33463
1.1708235 20.36004
1.1869804 21.41901
1.2031373 22.51254
1.2192941 23.64164
1.235451 24.80729
1.2516078 26.01049
1.2677647 27.25223
1.283921 28.53351
1.3000784 29.85532
1.3162353 31.21866
1.3323922 32.62452
1.348549 34.07391
1.3647059 35.56781

It sounds to me like some people might be using the wrong transfer function from the start, or some modified version and making up differences elsewhere in the tune.

It is impossible for the maf sensor to not show an increase in voltage with an increase in airflow.

Just because RPM's are going up does not mean airflow is still increasing. Too small of a turbo or supercharger will cause boost to fall off and give you maf results like that every time. It's actually very common.

Massairdirect

As every intake system, mounting flange, maf placement, tube diameter, albow angle, is also different. The voltage differences are just more pronounced at lower voltages.

I assure you the maf transfer function is the same. But the amount of air going across the sensor might be slightly different.

Vince@R/TTuning

iTrader: (7)

^^^^ u cant change the load points in the Nissan ECU's. You can change the value at each load point but the load point itself (I.E. voltage value) is not adjustable.

Vince@R/TTuning

iTrader: (7)

let me just say that I have had good results with PMAS MAF sensors. But when you have a stock sensor that is good up to about 400whp and then another sensor good to about 1000hp obliviously the resolution has to be affected, with that said it is expected and comes with the territory....

350z006

iTrader: (79)

I'm not a tuner by any means nor do I know enough about tuning to really get into it with you guys, but I have had my car tuned with the PMAS sensor...

While my tuner has been successful tuning my car with the PMAS, there was a time when my PMAS MAF failed and I purchased a new PMAS, and at least at idle the car had to be re-tuned with the new MAF because it just wouldn't idle properly with the original tune from original PMAS MAF...the setup itself didn't change...thoughts?

Massairdirect

it was probably an early sensor when they were still trying to find the perfect idle portion of the curve

djamps

iTrader: (1)

As vince already mentioned you cannot change the number or placement of voltage data points in Osiris it's kind of pointless argument. The data might 'be there' at very high resolution but the ECU will never be able to make use.]

That said I don't have any major issues with my PMAS. Gets the job done and handles a silly amount of flow with only slightly impacted idle a/f stability.

Massairdirect

Well that is unfortunate that Osiris won't unlock that part of the code. It would be very easy for PMAS to modify the curve on the sensor to change the idle voltage.

If anyone has some input on what range they would like to see I can get some changes made.

nathanwl2004

iTrader: (2)

I have no real experience with the pmax our any data logs of my car, but im running the GT MAF and it idles pretty damn close to stock. So much so that i would venture to guess most people wouldn't know the car is nearly as modded as it is if they didnt already know..

Ngo

thanks for the link to the PMAS transfer function. anyone have the transfer function for the Uprev GT Maf?

nathanwl2004

iTrader: (2)

Come to think of it that would explain why uprev also sells another MAF thats supposed to support higher flow levels but degrade idle slightly. It may be more similar to the old pmas sensor.

djamps

iTrader: (1)

The best thing to do is emulate stock flow transfer function as close as possible <1.5V or so. Not sure if it's even possible without creating an issue elsewhere, but it would sure be nice.

Massairdirect

It's actually not that hard. Anyone interested in a group buy if I can get it done? lol

djamps

iTrader: (1)

Honestly if you could really make this happen (+ consistency between each maf), probably rename it as well due to the HPX history, you'd have a leg up over the GT maf (more flow + perfect idle trims) and it would likely fly off the shelf.

Massairdirect

Get me some maf voltage datalogs at idle if you can

djamps

iTrader: (1)

It would be best put a stock MAF on a flow bench, as we know Osiris doesn't have the same voltage resolution compared to the logs you posted, so the logs might not be useful.

Massairdirect

I already have that data, I need to know what airflow VQ30 and 35's idle at.

Vince@R/TTuning

iTrader: (7)

^^^Not to be a dick but.... Why don't you source a 350z/g35 and then do the datalogs yourself as you are the company that would be profiting from them. As well as making sure you have the correct data to make a superior product.

djamps

iTrader: (1)

I would help but I don't have access to a reflashed G/Z with stock MAF.