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View Full Version : 82 W/safc2 Using Map Sensor? (no Tps)



mkiimaniac
09-23-2006, 01:12 AM
Ok boyz, go easy on the Maniac, as this is unchartered territory for me and am getting my feet wet. I have read several threads by you guys but still need a little guidance here in between my additional Google searches....

Here is the problem, which does cross-reference into a thread I have started "safc on an 82- who has done it?" but b4 getting too technical there i thought it better suited here for you big brained standalone tech-talkin circuit lovin brothers...

Problem is for the SAFC to tune effectively I need the inputs from both RPM & TPS but as many know the input from 82 TPS will not work in the 0-5v range that the SAFC wants.
Now since both MAP & TPS are putting out voltage, I don't think the SAFC knows/cares whether its from a TPS or MAP sensor & will respond with corrective fuel signal outputs to ECU accordingly (to how i have it set)

If I haven't murdered it too bad, read on.

My question is simply can I use a MAP sensor & run it to the SAFC MAP sensor input wires IN PLACE of the TPS signal input so the SAFC will have a more accurate reading of what is going on in the manifold (boost vs no boost)?

If yes, which map sensor is recommended? I don't quite undertsand the 1 bar 2 bar 3 bar shit but here is what I found on another Import Turbo thread about Map sensors,etc...

Has anyone done this & if so can you help me out a little? I finally broke down & got a SAFC2 & brand new LM-1 Wideband so I am prepared somewhat to do this.

Heres what that thread had to say.....
_____________________________________________
"on a stock map sensor, the amount of boost you can run is limited due to the fact that it doesn't know what to do with it, and throws a code.

OBD0 .65 KG/cm2= 9.24 PSI
OBD1-2 .75 kg/cm2 = 10.66 PSI

if you want more than that, you need to run a GM 3-bar map sensor (common) or others like the gm 2.5bar, the aem 3.5, and there are other crazy ones out there that are like 5 or 6 bar.

Remember, your tuning software must have the proper voltage assigned to the sensor. Both stock and the 6 bar maps operate on a fixed voltage range (0-5volts), but each psi moves a different amount of voltage over. Therefore it is imperitive to be using the right map sensor's output voltage range when you're tuning, and thus in your software.

A linear example (not accurate numbers, just for display purposes)

Code:
0------------------------------------5v 0----1----3-----5------7------9-----11 psi (oem) 0-1--3--5--7--9---13--15--19---21---27 psi (gm 3bar) 0-5--10--18--23--27--32--38--41--48-56 psi (5bar)

keep in mind, 1 bar is alread used by the atmospheric pressure, so it leaves you about 2 bars give or take your elevation left for boost... about 26-28 psi (depending on elevation) on a GM 3-bar."

4SFED
09-23-2006, 10:58 AM
How much boost you plan on runnin? If you're staying below 14-15psi use the 2 bar sensor, whereas the 3bar is good to about 28-30psi. And you would be better off with the 2bar vs 3bar if under 15 because regardless of whether 1, 2 or 3-Bar MAP sensors are used, each range of MAP sensor still generates a signal between 0.5 to 4.9 vDC (0-5v), depending on engine load, so spread it out and use the whole voltage range and make it more accurate with the 2bar as you can see from your own code example above.
I'm gonna have to check out your other thread you mention above, however, the 82 is a switch-type tps and you need a variable resistor type tps. I've never owned an 82, is the tps open on the side so you can see the end of the throttle shaft? You could get a longer throttle shaft and get a variable tps with an open straight-through drive tang and mount both tps on the throttle D-shaft together.
Also, the tps as mentioned is variable but also linear so you have a signal that changes at a linear rate as mechanical position of the throttle changes. You want the map sensor for engine load conditions.

4SFED
09-23-2006, 11:18 AM
I just found your other thread

Ok boyz, go easy on the Maniac,
I don't quite undertsand the 1 bar 2 bar 3 bar shit but here is what I found on another Import Turbo thread about Map sensors,etc...
can you help me out?
I'll help you out - which way did you come in? Really, get a grip on the basics and you will then logically (hopefully) understand what you need to do to accomplish your goals.

mkiimaniac
09-23-2006, 10:23 PM
Boost will be around 10-11 max-using stock ct26-don't want to get stupid with it....just get it tuned halfway decent & reliable & then my 7M in the 85 is next

If I go with the 2 bar map sensor, which one do I get...this is what I need to know...just for kicks I was at Toyota today looking up a MK4 TT Map sensor just to check price, etc but the guy couldnt even find the damn thing (lol)

A part #, website, etc would be helpful so I know exactly what MAP Sensor to get...I have heard that GM is OK but what have you guys used & with what success. There are hundreds of types of cars & years out there.

mkiimaniac
09-23-2006, 10:23 PM
ignore this..hit submit twice by accident

4SFED
09-24-2006, 01:10 PM
I use a GM 2bar - works fine

mkiimaniac
09-24-2006, 01:42 PM
Yea, after searching some more this morning found a 2 bar map sensor that should work ok too....

The only thing I'm trying to figure out in my head is how the stock TPS signal to the ECU is going to play into the equation.
If I have RPM & MAP signal to SAFC2 & stock TPS stays going to stock ECU I just don't know if all of it is going to work together or not--thats the part that's still over my head but I am still searching & trying to learn this stuff....thnx for the ideas & helo thus far...I'll get some pics up & try to document the install to help other 82 GTE'ers.

Also found this which seemed to be more accurate scale,...at least for a Chrysler P.O.S.
"The chart below describes the pressure-to-voltage relationship of the stock Chrysler Turbo MAP sensor (2 bar):

Manifold Pressure
(relative sea level / absolute) 2 Bar
MAP Output
14.31psi / 29.01psi 4.90V
14.00psi / 28.70psi 4.84V
13.00psi / 27.70psi 4.67V
12.00psi / 26.70psi 4.50V
11.00psi / 25.70psi 4.33V
10.00psi / 24.70psi 4.16V
9.00psi / 23.70psi 3.99V
8.00psi / 22.70psi 3.82V
6.00psi / 20.70psi 3.47V
4.00psi / 18.70psi 3.13V
2.00psi / 16.70psi 2.79V
0.00psi / 14.70psi 2.45V
5.00inHg / 12.24psi 2.03V
10.00inHg / 9.78psi 1.61V
15.00inHg / 7.33psi 1.19V
20.00inHg / 4.87psi 0.77V
25.00inHg / 2.41psi 0.35V
29.10inHg / 0.40psi 0.02V"

935motorsports
09-25-2006, 04:33 PM
Grab a Supra Boost sensor from a MK3. They are almost always free. I have a whole box of them.

When I use SAFC on any MK3, I always read from the map sensor instead of the TPS. This lets me tune via boost instead of throttle position. Since most cars have a turbo back exhaust, you can be only at 10% throttle and boosting over 10 psi. The SAFC will not know how to handle this. By tuning via boost, you can be aggressive pre-boost and then scale it rich for boost.

The only hard part is figuring out where zero psi is. The SAFC has to "learn" the boost sensor as a TPS input. It takes about 20 mins to dial it in. After that it goes on a linear scale.

mkiimaniac
09-25-2006, 07:03 PM
Grab a Supra Boost sensor from a MK3. They are almost always free. I have a whole box of them.


The only hard part is figuring out where zero psi is. The SAFC has to "learn" the boost sensor as a TPS input. It takes about 20 mins to dial it in. After that it goes on a linear scale.

A whole box, huh? Hook a brotha up!

So not being too familiar with the MK3, how exactly is the boost sensor differ from a map sensor?

Also, you said you always use the input from the Boost sensor or Map sensor to the SAFC on mk3's but they also didnt come with a TPS but on my car I'm tryin to figure out what to do because I will still have;;

stock tps going to ecu
new map/boost sensor going to SAFC along with tach/rpm input

IS this all going to work together..i know on most cars you have either inputs from a map or tps but not both....

now im willing to say this is a little over my head but open for the education...thnx

935motorsports
09-25-2006, 07:42 PM
You wont touch the TPS signal. You will simply put the new boost sensor output, to the TPS input on the SAFC.

You can do this for NA or turbo.

The stock MK3 sensor is good because it will read up to about 14 psi. That makes it roughly a 2 bar map sensor. (1 bar for atmosphere). Since they are free you can also usually clip off the pigtail wiring and use that as well.

You just need to find a ground and a 5 volt reference.

mkiimaniac
09-25-2006, 08:40 PM
Ok, thank you for the clarification...I am really learning alot & trying to pace myself as to not get overwhelmed...

I just need to get in there & do it...(SAFC comes this week)

I have a 87 7MGTE complete in the shed...I'll take a look..
I should be able to find it on the intake somewhere I guess..

Actually there is 1 in an junkyard nearby I could snatch...does it matter what year it comes off of?

mkiimaniac
09-25-2006, 11:34 PM
Ok, was at a friends tonight...found the sensor by the pass side strut tower "assy turbo pressure sensor" or something like that & also had "5v" stamped on it....

That, i believe goes straight to the boost gauge IIRC which makes sense assuming boost gauge also goes up & down according to voltage input from this sensor...& does not get fed to the 7m ecu but sounds like I could cut that off as you say & wire it to the SAFC.

Also, seems that the sensor is on the body harness not the engine harness which is perfect becauswe I can take the one off my 87 mk3 turbo parts car & use it.....only problem is to figure out which wire goes where.