DeaconFrost

Wanna sell me that PFC boost control unit? how much?

-Sean

maxcooper

This is a minor point (not a flame, just the facts), but the stock sensor tops out at 1.15 kg/cm^2 for me, which is 14.22 * 1.15 ~= 16.35 psi. I can imagine that other people's stock sensors might read higher or lower or may have different calibration settings, but that's what mine tops out at using the default PFC calibration.

-Max

apexkw

beast i think the way that you did it is probably going to be the best. lower cost so far and its plug and play. i am going to try to see if i cant source it out from the local shops. do you have a part number by any chance for just the 3bar map sensor?

SPOautos

The stock map sensor is exactly like Max said, it tops at 1.15 on the PFC which converted is 16.35psi BUT since the PFC is always lower than peoples gauges on a guage your going to see about 17-18psi.

I know cause I was running as much as 20psi of boost daily for a year and it NEVER goes over 1.15 on the PFC. As a matter of fact it really seems to loose its resolution at about 1.13 because my gauge has hit 20psi before and the PFC not register more than 1.13.

I just run the last rows real rich. However I am in the process of putting in a GM 3 bar so I can do it "right"

STEPHEN

Snook

iTrader: (12)

yes sorry i converted the 1.15 wrong that is the max on the commander for the sensor. maybe you need to look into a better gauge becuase what the map sensor is reading is whats important. Oh and your welcome for the info on the connector. also if you go to gmpartsdirect.com and put in your sensor # it will tell you the connector part # you need if its old they may not have it and youll have to use the 3 wire weather pack.

Beast From The East

apexkw - I don't have the part r handy, but all you eed to do is talk to Henry @ Motorsports Dynamics 916-648-8000 and they can get it for you and drop ship it. Just be prepared for it to take a while because I believe they have to get it through a Japanese Apexi source.

Motorsport Dynamics website:

http://www.motdyn.com/

SPOautos - ya know, Stephen, now that I think about it, you may be right on the mounting. Chris left the stock 2 bar on the pedestal and just zip-tied the sensor through those two holes to a brake or a/c line that runs along the firewall in the same area as the stock mounting point. I didn't think about that. I'll pull the old pedestal and stock sensor and take a look.

BTW - you already know this, but your "poor man's" tuning isn't providing you with much granularity over 15 lbs of boost. Kinda scary - get that $hit fixed :-)

maxcooper (longtime Big lister...) - you beat me to the punch on the minor calc issue. We're all a bunch of **** geeks around here, aren't we? :-)

Beast

SPOautos

You correct in that what the map sensor reads in correct to the PFC for tuning, HOWEVER its not the accurate boost. There are many old discussions in the PFC section that all come to the comclusion that the PFC reads the map sensor wrong which is why the PFC reading is off as compared to a gauge....with the stock map sensor anyway

Pretty much everyone I've ever talked to said thier PFC was a little lower than thier mechanical gauge

STEPHEN

$150FC

Hey Stephen, did the PFC read the correct pressures below ~1.13bar?

I mean, you say that the PFC reads the stock MAP incorrectly, but apparently you can calibrate it, too. Could it be that it is not calibrated correctly up high? (for instance, like someone else said, when the car is off, do the gauge and the PFC both read 0?)

SPOautos

Nope, the PFC reads negative vacume when its off.

The boost level is just a arbitrary number anyway that tells the PFC what cell to look at. As long as the scale between the PFC and map sensor stay the same it wont matter what the atual numbers are

STEPHEN

SPOautos

Yea, I know but its just going to make it rich at 15. I never run a solid 15 it just zips past 15 on its way to 18+ LOL

I'm typically either running vacume up to about 5psi just cruising around.... or 18psi lol

BUT still, I know its not "right", I've got a GM sensor ready to go in the car as soon as I get done redoing my fuel system.

STEPHEN

Beast From The East

Steven -

I, too, had neg vacuum with just the key on on my pfc - about 30mm Hg give or take. You have to adjust your scale to zero it out (see my earlier post on the scale adjustment). You need to do this with the regular setting for the 2 bar and with the 3 bar Option 1 setting (at least, for the Apexi 3 bar. I'm sure you also have some fine tuning with the GM 3 bar). My Autometer gauge now reads pretty close to what the MAP is telling me. It used to be off by 2 or 3 lbs, now they match up at 15 lbs.

mavila

iTrader: (58)

I just called Motorsport Dynamics to order one of those Apex units. Guess what - the "new" price is $162!!! WHOA!! Talk about an increase! Suddenly the GM unit seems like an interesting alternative. How much are those anyone, and where's the best place to get one?

Michael Filippello

I have a quick question regarding this subject. i understand that the stock sensor only reads to 1.15 bar, and that above this the computer uses the last row (p20) for its fuel and timing numbers. but if you only change the sensor but do not change the parameters of the cells, then does it really make any difference what sensor you have?

For example, from the factory, the last row in the power FC is set to 2.4 pressure ratio. This is around 1.4 bar correct? So if the stock map sensor only reads to 1.15 bar then when would you ever enter into row 20. if you change to a 3 bar and do not change the pressure ratios in the rows, then even with the higher resolution of the map sensor, you are only set up to 1.4 bar. any thing over this and you only have maps for 1.4 bar working. Is this correct? or does the computer continue extrapolating above row 20 using the info from the map sensor to tell it how high you are. If not then you would have to change the parameters of the rows to accomidate the higher boost you plan on running in sacrafice of better resolution down low.

Am I correct on all this or am I missing something. We can not add rows, only spread our boost range among the 20 rows presently available. This means the higher boost we tune for the less rows for each boost level we get ie. less resolution. Is this how people are using the power FC to run 25+lbs of boost.

Mike

PS I guess this wasn't a quick question after all. Are any of them?

Michael Filippello

While this is correct, it also is somewhat not true. If you have your power FC's boost setting set to 16psi and you over boost the power fc will fuel cut once you overshoot by 10%, if I recolect. This means that the computer should shut you down in the evnt of overboost not let you run lean. Now if you set your boost for 25 psi and go to 25 psi then you are in for trouble as the computer will not hit boost cut and you go well past the limits of the stock map sensor and/or your last programmed cell.

mike

busy13b

iTrader: (5)

This may be of some help:



This place sells them for $69.95, but if you check with your local GM dealer, you can probably find them even cheaper.

GM 3-bar part#: 16040749


Pin A -- Ground
Pin B -- Sensor output
Pin C -- +5 volts




If you cannot find the correct wiring harness, you can use a Conduct Tite brand GM A/C pressure switch plug (part# 85146 from Pep Boys, about $10).

Cut a small slot down the side of the connector to make it fit the MAP sensor.

Beast From The East

Michael, the short answer is yes but you missed a couple of things that add some 'no' to your statements - no matter how high a boost you run, with the stock map sensor the highest row you will hit is the one programmed for 1.15 kg/cm^2 (which is not 1.15 bar, and is equal to 14.22 kg/cm^2 *1.15 = 16.353 lbs of boost). The out of the box default setting for that row in the PFC is between p18 and p19. That's as high as it goes, no matter if you run 8 gazillion lbs of boost. Therefore, the pfc will not use row 20 if you boost over 1.15 kg/cm^2 unless you change the resolution using the dataloggit system. If you change resolution, then some other row has to suffer.

Stock settings:

p18 = 1.00 on map sensor
p19 = 1.20 on the map sensor
p20 = 1.40 on the map sensor

I've added some additional granularity in that area:

p18 = 1.00
p19 = 1.15
p20 = 1.3

I run 1.054 (15 lbs) as an everyday setting with 550/1300's, and will run 18 lbs on 103 octane when I put in 850 primaries.

Hope that clarifies the issue for you.

Now, mavila, as far as the cost goes, even at $162 it is worth it for plug and play vs. hack the harness in my book. If $100 is an issue and you're planning on running in the areas requiring proper monitoring of high boost, then this may not be the right car to own. You needed to spend some dough to get all the needed pieces in place to take advantage of high boost - what's another hunski?

Beast

gdnimr0d

iTrader: (4)

hmm i am new to where i can install the 3 bar map sensor...well where is the original map sensor....and can anyone post some pics of there 3 bar map sensor setup...thanks peace out

Beast From The East

Well, the standard reply would be SEARCH, YOU NOOB!



Now, something a bit more useful for you - the picture of the Apexi 3 bar map sensor is in the picture on the top of this page. It's the little black thing with the tabs with holes in it on either side, upper right corner of the photo. It looks just like the stock 2-bar map sensor, which you will find on a small black pedestal mounted against the top of the firewall on the driver's side in the engine bay. There will be a small vacuum line running from the bottom of it over to the passenger side of the upper intake manifold.

The GM 3-bar is in the picture in the middle of the page.

One thing you should invest in is the Factory Service Manual (FSM) - you will be able to look this stuff up, and also many other items about the car. Worth the money to purchase.

Also, the search feature is a really good tool on the forum - there is little under the sun that has not been already hashed to death on this forum. Chances are if you have other 'I'm a new guy, how do I do XXX?' type questions you will be able to get the answers on your own by using the search feature.

Beast

Michael Filippello

or, if you are cheap like me, you can go to this website and download the entire manuel for all years as well as parts manuels. you will save some trees as well

http://www.iluvmyrx7.com/index.htm

mavila

iTrader: (58)

Well, you are right and I ended up getting one from RX7store for about $132. Not quite the $162 from the other place, but still more expensive than the GM one. I'm also a big fan of plug and play. However, when you're spending like $6K again when you've probably spent $10K in each of the last 2 years on various upgrades, you start trying to save when you can. This is an EXPENSIVE hobby.

Beast From The East

Can I get an AMEN!

Q: How do you make a small fortune in racing?
A: Start with a large one.

Northwest FD3S

A quick question on programming the PFC, do you require the datalogit to program the scale and offset? In the prgramming menu on the commander i can find the oprion 1, 2 , 3 menu under the PIM Volt, but the settings there are for voltages between 1V and 5V and also an RPM selection. Not sure where to set the scales and offsets, any help would be great thanks.

Boostn7

Ok...here it goes again....

Tested w/ pump vs 2 gauges(HKS) with default settings w? OEM Mazda 2 bar

Psi = Kg/cm2 on PowerFC
0 = .25mmHg
2 = .10 kg/cm2
4 = .25
5 = .31
6 = .39
8 = .51
9 = .58
10 = .65
12 = .78
14 = .92
15 = .98-.99
16 = 1.06
17 = 1.12-1.13
17.5 = ~1.15 kg/cm2

These are my results....and every PowerFC I checked it always read less then actual boost.
Simple test....turn ignition on.....if boost readout is in mmHg then its reading less already. This could be adjusted to read almost always "0" by adjusting the offset for any map sensor.

With new ProfecB boost controller which also had digital read-out it would say 17 psi and PowerFC would register 1.12-1.13 kg.cm2....almost maxed but easily over the 16.3 psi many believe is the max!!!!

JD

CCarlisi

Is anybody using a scale of '45274' with a GM 3-bar? Mine was originally set to 41800 with zero offset and Demetrios changed it to 45274 with zero offset.

MrBob 86

That is the GM sensor. You can get a 3 bar MAP from just about any auto parts store. They came on the 1989 Turbo Trans-Am.

GP Sorenson # 77911510
GM # 16040749