Has anyone found that this works at all?

I was playing with the stock Mazda/Denso sensor plugged into the side of the PFC yesterday, and when both pressurizing the sensor, and pulling a vacuum on the stock sensor with the ign on engine off, boost did not change pressure the PFC is seeing.

I would think that if it did infact work I should be able to see a change because the range of pressure change is substantial enough to easily be seen I would think. It looks like a good std number is 1 Psi per 2000ft of elevation change, so just in my neck of the woods (which I will be driving in hence the reason why I want a barometric correction) there should be up to a ~4 Psi change from sealevel to drivable mountain ranges. Enough to worry about IMO.

Anyone bother to install this and test to see if it even works?

My stock map sensor seems to be operating correctly so I am sure the stock sensor is working properly, it just doesn’t seem to adjust or change the pfcs boost readings at all.

 

this is the same thing that the "PFC Boost Kit" is based off of (using the stock boost sensor as a barometric reader, the new 3 bar boost sensor to read boost, and the AVC-R solenoid to control boost) . I would like to know as well if it "really works".

 

I looked at the circuit inside the PFC and all there is from what I can tell a small resister between the negative (black) and the input channel (green) on the side port on the PFC.
The ground runs throughout the board as most electronics are configured.

Is it possible to run a signal through a circuit like this? making it posible for this to even be a posibility that current modles of the PFC carry this feature?

I cant remember where I read the actual text from apexi that stated that this was the purpose of this port, does anyone have the actual manual or PDF stating this should work?

 

I will take a look at the actual PFC manual tonight to see if they say anything about that port

 

I read a post on the Datalogit forum about a guy with the Apexi boost controller setup (stock MAP hooked up to the PFC port) and he said it didn't zero out the pressure reading of the PFC. It seems this feature does nothing. Also, I vaguely remember reading somewhere that the relative boost is only calculated when the ignition is first turned on which means no help when driving into the mountains. This may not be true but for your testing maybe you should turn the ignition off and back on when looking for changes.

I have been playing with the Datalogit Setting 3 and have discovered how to make the PFC boost readings more accurate. Most of the accuracy needs to be in the 10-18 psi range with 14 psi being in the middle. So in Setting 3 <PIM scale, offset> I raised the scale and then zeroed out the PFC pressure with the offset until I had the kg/cm^2 match the boost guage at 14 psi. I used a Mityvac t-ed into the MAP and boost guage for testing. My scale is 35500 and offset is 3370 at ~1000 ft elevation. PFC users close to this altitude should be able to use these numbers to make their boost more accurate (within .5 psi from 10-18 psi). Anyone else want to try? At higher altitudes you would need a bigger scale and then rezero your offset and compare values at 14 psi until they matched. This wouldn't help you when driving into the mountains where the elevation changes unless you took your laptop with you and entered new values along the way but it could make the pressure values closer than what they were. Note that all maps will be read different so previous tuning will be off! Maybe we could make a list of "better" scale and offset values based on altitude this way...

alltitude=1000' scale=35500 offset=3370

 

I have been working with the same issue Matt as per Chucks recommendation for correcting boost readings.

I am able to get a scale and offset for very close to correct for the entire vacuum range, I can also get a scale and offset that works very well for 0,10,15,20 Psig but cant get the 0-10 section to work out because my 5 Psi = ~3.5Psig on the commander readout.
Running an apexi 3 bar sensor.

To me it looks like to get it close over the entire range we would need to use a polynomial, which there is no facility to do this in the software.

I wonder if it is something that Fasthatch could integrate as a add on?

 

Also what is your correlation for your boost readings Matt? What Psi are you reading on the commander compared to the actual gauge readings you are observing?

Do you happen to have a link to the thread you are talking about, I would like to read over it and see what it has to say.

 

So you have the Apexi 3 bar MAP sensor but that changes things very little. I believe the scale stretches the pressure readings across the whole range of MAP voltages and the offset changes where zero begins when converting from absolute pressure. You might try lowering your offset until the Commander pressure blinks between 0 mmHG and 0kg/cm^2. This may help your low boost readings but you may have to change your scale again for accurate boost readings and rezero at atmospheric pressure and repeat. I'm not so sure the PFC has a conversion error but maybe the default scale/offset values are poor (garbage in garbage out) and the MAP voltage output is not completely linear as you suggested. I guess this could be tested with datalogging. I'll retest my PFC pressure readings across the whole vacuum boost range for accuracy.

Interesting Datalogit threads but you must be a member...

http://sports.groups.yahoo.com/group...S/message/4710
http://sports.groups.yahoo.com/group...S/message/4370

Good conversion site...
http://www.onlineconversion.com/pressure.htm

 

Luckily I do and got in a long time ago when there wasn’t such a long wait.

Thank you for posting the links.

I don’t think I have read any success by using this port for this purpose,

I will try and test for initialization at startup, though I don’t believe this has any effect, as the map alone plugged in would be able to give a signal to the PFC at startup and it would recalibrate the system based on initial barometric readings if this were true I would think, making it useless to have the 2 bar operate in this manner at startup only. But I will try that.

I know my PFC will hold a reading not equal to 0 with the 2 bar plugged in to the side port, and is a common symptom from reports.

 

Altitude=900'-1000' Barometer=30.08 scale=35500 offset=3370

VDO Boost guage | PFC kg/cm^2 | PFC->English

18 1.24 17.64 maxed out!
17 1.20 17.07
16 1.12 15.93
15 1.07 15.22
14 0.99 14.08
13 0.92 13.09
12 0.87 12.37
11 0.79 11.24
10 0.73 10.38
9 0.64 9.10
8 0.59 8.39
7 0.51 7.25
6 0.46 6.54
5 0.39 5.55
4 0.32 4.55
3 0.27 3.84
2 0.18 2.56
1 0.11 1.56
0 0 0
- 5 -101 -3.98
-10 -233 -9.17
-15 -350 -13.78
-20 -490 -19.29
-25 -600 -23.62

My PFC is within .5 psi from 7-17 psi. The barometric pressure for the chart is 30.08 inHg while I edited the scale and offset when the pressure was ~29.92 inHg = 1 atmosphere. Reading an analog needle by eye is not the most accurate. I compared the VDO guage to an Autometer and they were in the same ball park.

 

Altitude=900'-1000' Barometer=29.93 scale=35500 offset=3377
'93-'95 RX-7 OEM MAP sensor

VDO Boost guage | PFC kg/cm^2 | PFC->English

18 1.24 17.64 maxed out!
17 1.19 16.93
16 1.12 15.93
15 1.05 14.93
14 0.98 13.94
13 0.91 12.94
12 0.85 12.09
11 0.77 10.95
10 0.71 10.10
9 0.63 8.96
8 0.57 8.11
7 0.50 7.11
6 0.44 6.26
5 0.37 5.26
4 0.29 4.12
3 0.24 3.41
2 0.16 2.28
1 0.09 1.28
0 0 0
- 5 -111 -4.37
-10 -238 -9.37
-15 -362 -14.25
-20 -490 -19.29
-25 -610 -24.02

I did some more testing and changed the offset a little more when the barometric pressure was close to average = 29.92 in Hg. I got the boost to read within .5 psi for all readings. The vaccum appears to be off by a little more but 1 in Hg = .49 psi. My VDO may not be as accurate in vacuum as well. Overall the 2 guages agree very well and the PFC pressures look mostly linear (at this altitude at least) and with a well chosen scale and offset should remap to any desired pressure. The idea that the pressures are not calculated correctly by the PFC appears to be wrong.

 

I looked at the conversions between absolute PIM (kg/m^2) and relative boost pressure (mmHg & kg/cm^2) since making the PFC read the same boost pressures as my mechanical boost guage by changing the scale and offset. My PIM pressure read 10399 kg/m^2 the other day while the PFC boost read 0 before starting the car. Some people may think this should read 10000 because that is where zero is on the P rows of the 20x20 maps. However, 1 atmosphere which is the average pressure at sea level equals 10332 kg/m^2. The barometric pressure was about 30.13 inHg (29.92 inHg = 1 atm) which is about 72 kg/m^2 above average and 10399 - 72 = 10327 kg/m^2. This is very close to the average pressure at sea level but I'm at about 1000 feet where the average absolute pressure just happens to be about 10000 kg/m^2. When I made the PFC boost match my boost guage, I made the absolute PIM pressures relative to my elevation (kind of like adjusting a barometer for elevation). This is the only way to get the PFC boost to equal the PFC PIM. The P row map reference for zero boost should be changed from 10000 to 10332 when making these changes so zero is still zero. I would also recommend adding 332 to all the other P row map reference values to keep the spacing the same. This would also be the most compatible with tuning that already exists. The high boost cells of the fuel and timing maps should still be changed though. Here are the steps to making the PFC boost reading accurate for those with the stock MAP sensor...

1. In Datalogit setting 3, change active PIM scale to 35500 and add 332 to all Map Reference Boosts. Turn ignition on but don't start car. Upload the new map to the PFC. Adjust the PIM offset until the PFC boost equals 0 and the PIM boost equals 10332. Upload new map to PFC after each change and recheck PFC boost and pressure. It's best to do this when the barometric pressure is average or make adjustments if it's not.

2. In Datalogit setting 1, Enter appropriate boost values. The correct boost will be achieved now.

3. Check and adjust fuel maps and ignition maps. Vaccuum areas should be close but the higher the boost the more changes should be necessary. Be careful at higher elevations as the same boost will produce more heat than at lower elevations.

If I'm correct about how the scale works, then 35500 will be appropriate for everyone with a stock MAP sensor. Those with other map sensors will have to figure out the appropriate scale (with MityVAC) as described in earlier posts in this thread. Make a backup of your current PFC map and be sure you have the proper tools and knowledge to tune the PFC before making these changes. I'd like to hear from anyone who has tried this.

 

Just as a small update, it seems this functionality may not be intended for the 7 at all.

http://paulr33.skylinesaustralia.com...ro-harness.jpg