djamps

iTrader: (1)

I was able to tune around the low idle resolution but it did take quite a bit of trial and error (the level that most tuners wouldn't waste time with working on the clock). Where were you a few years ago when I needed you LOL.

Massairdirect

Sorry man.. You must have spent A LOT of time doing that.

Massairdirect

I still need a screenshot or excel file of the stock maf transfer function so I can modify the new HPX-N2 spreadsheet to have the correct stock voltages.

Massairdirect

Here is the new transfer function tool for the Precision Flow labs HPX-N2/GT4 calibration..
should be useful and you can add your own voltages.

http://www.massairdirect.com/resources/PFLHPXN2GT4.xls

tcode

iTrader: (7)

Oh yeah, you can't probably imagine how much this helped me, with the rest of this topic too. I'll explain this .

Not very long time ago (I should probably start a build topic in FI section ) I hit 5.12V at 5k rpm with my ProCharger setup (9PSI pulley set). Since I decided to keep this car in as much as possible in a stock form, didn't want to go with Stand Alone unit, so UpRev Osiris Tuner gives me the most of the stock ECU. So, logically, had to swap stock MAF sensor with rescaled one capable of measuring much more air mass than stock. Searching this and other VQ forums, found that there are two routes only. The PMAS and UpRev GT.

The GT one supposedly should give stock like idle with much more air flow measuring at higher Volt values. The other one, disreputable PMAS has much lower price (tipically half of what people for GT wants), but most of the people said it's overkill and it won't work good at low loads.

Now, I'm handicap too, because the ECU in my car is one of the rare which aren't real time tunable. So, UpRev GT seemed much wiser route. However, I couldn't resist on the brand new PMAS HPX-N sensor showed up on ebay for just $110.


While waited to be delivered, reading mostly more and more about people complain on a PMAS . Finally it showed up at the local post office. Decided not to install it one more day which I spent on carefully analyzing and transferring values for a given air mass between stock and PMAS using XLS file quoted above. Of course, most of the load points had to be interpolated and I didn't even used calculator for that, just doing it by "feel", a few hundred points up or down between two values. Didn't touch K constant or fuel compensation table at all (alll values are 100 currently) since I did everything on a MAF table. Finished late night so it was time to go to sleep.

Woke up this morning early, was pretty excited how it will turn out so I couldn't sleep long . Get to business soon, installed sensor, reflashed ecu ONCE and this is the result (the engine sits overnight, so completely cold):
http://www.youtube.com/watch?v=c0FZd...ature=youtu.be

My tune is right where it's supposed to be, except above 5k rpm where it wasn't tuned even before since I maxed out stock MAF sensor at that point. It starts cold, warm and hot same as a stock, idles PERFECTLY as it idles with stock MAF, no hesitation, misfires or anything odd. The only difference is that I hit 3.6V at 5k now (5.12V before with stock MAF).

Thanks all for your time reading this post and valuable info provided here. People, don't be scared of PMAS, it can be done right .

djamps

iTrader: (1)

Glad you did it right and set the MAF table correctly instead of changing everything else instead (K, fueling, ect ect). Try to tune the rest on the MAF as well, keep the fueling as close to (+/- 5%) as possible. Your car will run like stock in and out of boost . I did 90% of my fueling with PMAS on maf alone and you'd swear it came boosted from the factory, startup, idle, part/full throttle, all of it..

tcode

iTrader: (7)

Thanks!

I did whole fueling tune just on a maf table with stock sensor and yes, engine response and driveability on and off boost is awesome, exactly like it come that way from a factory . Later, just transferred to PMAS curve. Will definitely do the rest on maf table too.

BTW. First three load points above 1V of stock and PMAS sensors are the same, idle portion. Well, it is at least on a PMAS sensor I get.

Fixxxercask

iTrader: (21)

So if someone replaced their MAF/intake piping with a larger piping and attempted to re-use the stock MAF sensor, they would have to do a lot of trial and error to get the voltages adjust correctly in the table to now match the additional air going into the engine so that it puts the correct amount of fuel in?

My next question. The alternative to that would be to buy one of these PMAS MAFs and use that excel sheet to punch in your MAF piping diameter and it calculates everything for you? You then take that data and import it into the table.

Am I understanding that correctly?

tcode

iTrader: (7)

Having transfer function of stock maf sensor would put you right on spot with different tube size.

Assuming you have near perfectly tuned maf table with stock sensor and stock diameter tube. It's not hard to do it with djamps web tool. Make a log file with most driving conditions, idle, partial throttle and wide open throttle through all revs. It will give you enough maf voltage vs air mass (gram per second) load points.

Now, having correct transfer function of any other maf sensor and you can make it work at once. Maf table is two dimensional, a voltage and value directly in relationship with injector pulse width. For every voltage on maf table, look up for corresponding air mass in your log file. Then look up in excel file of uprated maf the closest voltage value for that air mass you found in your log file. Finally, find in the maf table that voltage and enter value of stock maf sensor for given air mass.

Damn, I'm not sure will you understand, but I am doing my best .

djamps

iTrader: (1)

^^ On point. I wish I had a transfer function back in the day.

Fixxxercask

iTrader: (21)

That is good info. I think I understand for the most part. I think I will go that route instead of buying an aftermarket MAF. I am not boosted so I don't really need an aftermarket MAF. I will just be running a 4 inch intake pipe NA. So I can basically take the excel sheet from say the PMAS MAF and compare that to my logs to get my numbers for the larger diameter piping?

Is there a transfer function spreadsheet for the stock MAF sensor? I would think I could just use that an input my larger diameter piping size since it can do the calculations. Then from there just input that info into the MAF table?

tcode

iTrader: (7)

So far I didn't found transfer function for the stock MAF sensor. But I think you should be able to make your own using PMAS xls file as a template for formulas and calculations and log with stock diameter pipe.

Massairdirect

That's awesome, glad I could get the correct info out there for the sensors. The new HPX-N2 curve is even better than the original curve I made.

Massairdirect

Dont use the PMAS sheet for the stock maf, they are totally different.

djamps

iTrader: (1)

You should be able to just tweak K and some fueling values a bit with a larger MAF tube on the stock MAF. No way do you need to recalculate the whole table. Like Massairdirect said the stock MAF and PMAS are completely different...

Massairdirect

Newmafvalues=(newmaf housing area)/(oldmaf housing area)*originalmafvalue

djamps

iTrader: (1)

In uprev you can use K to achieve the same as changing the whole MAF table

NewKvalue=(newmaf housing area)/(oldmaf housing area)*originalKvalue

Massairdirect

Nice!

Fixxxercask

iTrader: (21)

That sounds like the best way to go. Just apply that formula to the K values already in the table. Does anyone know what the ID of the stock intake pipe is? I can measure, but just curious if anyone knows.

350z006

iTrader: (79)

The stock MAF pipe is 2.75"