3-Bar map sensor?
 

I got another question. When running the Power FC when do you need to get the 3-bar map sensor? You need it when you run over 15 psi right? I gonna be running the Greddy profec B spec II with the PFC. I plan on running around 18 psi high and about 14psi low. Where can I get this 3 bar map sensor for a good price and how does it wire in to the FD? As everyone can tell I'm new to this PFC deal. Thanks...Tony

You can get the map sensor from Jason @ the rx7store I believe. It's the Apexi SAFC soleniod if I'm not mistaken..

Thanks....so how do you install it? I'll have to check how much it is at the RX7store, anyone else know of any other sources?

Should be plug and play I believe...

It's not plug and play.

You need to goto to OPTION 2, set scale to 41800, and offset to 0. The wiring is:

GM 3bar | Function | Rx7 Factory Wiring
A | GRND | Black/Grey
B | MAP SENSOR VOLTS | Greeen/Yellow
C | 5V | Brown/White

R-magic....thanks for the help. So I will need to get this GM map sensor if I run more then 14 psi correct? Also where can I pick up one of these GM map sensors? GM dealer :-)

Thanks for clearing that up. :)

You can run up to 17 or 18 psi boost with the stock map sensor ... but if you overboost there is no way to compensate with more fuel or conservative timing. You will get whatever you program at 17/18 psi. Assume you overboost to 20+, you will be lean compared to 17/18 psi boost.

My stock 2 bar map sensor would not read above 16.8 psi. And i have a few junk motors to prove it! Also have the car tuned for the higher levels with race gas only. Anything above 15-16 psi for pump gas. At least not unless you run some real conservative timing and maybe water injection.

So is this they only option with the 3 bar GM MAP sensor? I have heard of someone else using option 3. Just doing my home work because I am going to a gm 3 bar map. Any and more input would be great.

Thanks

My stock MAP sensor tops out at 1.15 kg/cm^2 ~= 16.3 psi. You'll need a 3-bar sensor for running above that boost level for the reason that twokrx7 described.

-Max

I should have stated that I run the PFC w/ commander.

Correct me if im wrong but wasnt the max boost on the stock map sensor 16psi?

17 psi stock MAP sensor

option 2,3,&4 are all the same.
option 1 is for PowerFC boost kit

Hmmm - here's what I did for Apexi 3-bar
 

Well, I'm unsure about the GM 3 bar, because I ordered the Apexi 3 bar sensor only out of the Apexi boost kit. Swaped it with the stock one no problem. Changed to Option 1 on the PFC, but needed to use the datalogit to adjust the offset a bit to zero out boost with the car off. Stock setting is 43860 scale, 3289 offset. I used the same scale but and offset of 2820. Boosting to 15 lbs on a t04s very nicely right now, and have very briefly (as I adjusted boost settings with my controller) got it up to 18 lbs (very, very, very short burst) and it accurately reflected 1.29 on the 3-bar.

The nice thing about the Apexi unit is no hacking of the harness - it plugs in just like the 2 bar.

Beast

16.3 on a PFC is going to be around 17-18 on a gauge.

STEPHEN

hmmm, that apexi one seems nice, where did you get it?

Source for 3 bar
 

I purchased mine from Motorsports Dynamics in Sacramento. Cost was ~ 70 bucks, and it took a month or two to come from Japan.

I've got the GM 3 bar sitting in my garage, does anyone know how to hook this up? I see where R Magic posted the wire conversion BUT what do I splice it to? The map sensore just has holes where a plug would clip in. The stock plug doesnt work so I'll have to cut it off. What do I splice on in its place to plug into the GM sensor???

Anyway know?

Thanks,
STEPHEN

DId you guys see this one at rx7.com? what do you think about it? and does it work the same as a gm sensor or as a boost kit from the pfc


http://www.rx7.com/store/rx7/fdecu.html

MAP (manifold absolute pressure) sensor in a factory 3rd Generation RX-7 cannot see past 17psi. Using a 3 Bar MAP sensor will allow the computer to map engine management strategy up to 29psi. Note: to be used only with A’PEXi PowerFC or Haltech ecus. PowerFC requires special programming, call for details.

3 Bar MAP sensor
Price: $99.00


3 Bar MAP sensor connector and pins
Price: $12.00

That's not the Apexi 3 bar...
 

I think that's the Haltech 3-bar. I have no idea how to hook it up or what scale/offset to use. Looks like they'll supply the needed info and hardware if you buy it.

The Apexi 3 bar looks exactly like the stock unit - you can't tell the difference unless you look at the parts number.

My 3bar sensor that came with the Boost control kit didn't look like the stock sensor at all. There is a pic in the PowerFC forum of the kit.

Looks the same to me....
 

The component I'm talking about is the black 'tee' looking piece in the upper middle right side of your photo, right above the plastic baggie. The hose nipple attachment is where the vacuum hose plugs in, the two metal rings are where your screws tighten in to the mounting pedestal on the fire wall, and it even has the same three-pin plug for the harness. Plug and play for me.

Now, the boost controller pieces I don't know about. I don't use the boost controller from Apexi - I have the old dial-boost setup that Pettit sold some 5 years ago.

Am I missing something, Steven? Wouldn't be the first time....

https://www.rx7club.com/attachment.php?postid=798689

just to clear things up the stock map sensor reads to 1.15bar or 16.8psi. This is a FACT its not 15 or 16 or 17 or 18 or whatever you want. And what twokrx7 said is exactly true. Thats why when I boosted to around 30psi even though my car was tuned super rich above 16psi on the stock map sensor all it saw was the max it can read 16.8psi and it gave all the fuel it could but that wasnt near enough for 25-30 at 6500rpms...

steve is it the new or old # 3 bar sensor? its a good idea to buy the connector that goes with it but if you have the old sensor only its gonna be hard to find the old connector. Garfinkle told me he used a 3 wire weather pack instead of the connector which if you have the old sensor is a great idea. Then you just want to cut off the stock connector and splice those 3 wires with the wires that come out of the connector A B C on the sensor. Simple but it still took me about 3 hours to mount the sensor and wire/solder it and insulate it like factory. pretty cool mod for safety IMO...and for the soldering go pick up some Flux, you shouldnt do anything without it.

Yes we are talking about the same 3 bar MAP sensor in the photo. Every stock sensor I have seen is mounted to a metal bracket that attaches to the firewall with a M6 bolt. It does not have the side mounting wings like the 3 bar sensor. The electrical side is definately plug and play.

Re: Looks the same to me....
 

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

-Sean

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

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?

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

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.

Replies .....
 

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 anal geeks around here, aren't we? :-)

Beast

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

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?)

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

Re: Replies .....
 

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

You can fix the negative vacuum....
 

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.

Price??!!!!
 

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?

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?

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

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


http://www.hondata.com/images/gm3bar.jpg

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.


http://www.hondata.com/images/3barplug.jpg

For Michael F - yes and no
 

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

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

'Nimrod....
 

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

:D

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

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

Re: Extra Ben Franklin
 

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.

Re: Re: Extra Ben Franklin
 

Can I get an AMEN!

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

Programming.
 

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.

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

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.

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