3bar = incorrect stock boost gauge ?

[pacecarta]

question

i installed the 3 bar with the PAC kit and noticed my stock indash boost gauge is way off (low) ...not a big problem since i run a seperate boost gauge but just curious incase i decided to go stealth and remove the aftermarket gauges once its dialed in

i dont know if it has to to with the PAC controller tap of the map signal wire (didnt cut just stripped back insulation ) or is it just the 3 bar map
is there something i can to do to bring it back to being accurate or can i just swap back the 2bar map and run with that.
is there a downside to using the 2bar in an alky setup?

 

[Slow91z]

Don't use a 2 bar with Razor's PAC....it will not up the alky pressure after 15 PSI.

The reason it's different is because they both use a 5 Volt reference voltage...The 2 bar maxes out at 15 PSI and the 3 bar maxes out at 30 (roughly)...So you're stock boost gauge now reads double (15=30).

 

[HellOnWheels]

I installed Razor's PAC system on my 87 which already had the 3-bar MAP used in conjunction with the Boost Sensing Harness. I tied in to the 3-bar and could NOT get the turnon point of the PAC system to turnon any earlier that 8 #'s of boost no matter what, only when I tied into the stock 2 bar was I able to set the boost turnon at 4 #'s boost.

Anyone else notice this problem?

HOW

 

[pacecarta]

my turn on is about 6lbs ,never touched the settings in the controller

plan to run with around 20lbs so the 3bar stays ,

couldnt i just get another map connector and tap the power and ground wires (piggyback basically) , tee the vac/ boost line and run both maps with the 3bar feeding just the controller and the two bar running my gauge ?

 

[Slow91z]

That's the way my Boost sensing harness is...I have the MAP's right next to each other with a Vac Tee right in front of it...I'm sure Razor can offer a suggestion on where to get the 5V voltage for it...My harness has it coming from the TPS harness.

 

[Razor]

Well you have a couple options if you want to have your factory guage work correctly.

First is the only way the 15 PSI guage will work is if its connected to the 2 bar. The three bar will need a new harness to put power,ground on it. What I can recommend is on the plastic line leading to your aftermarket boost guage, cut it and install a brass T fitting under the dash. From the T fitting run a hose to the nipple on the 3 bar. Next you'll need a harness for the 3 bar this can be gotten from AC Delco or a junk yard..If you get one from a junk yard.. it will be "keyed" different. To re-key the plug, use a single edge blade and cut the notches into it accordingly. The harness will require a 5 volt source. You can get this source from the ECM, or build a small regulator with parts obtainable from radio shack.. or buy one from me. I sell the regulators for 10.00 12v in, 5v out. Hook up the green wire to the center lug on the 3 bar MAP. Done. Your factory guage then reads to 15 PSI.. the 3 bar will drive the controller. And all of this can be done under the dash.

Now the issue with the T-link boost sensing harness is that it alters the voltage coming out of the sensor. See all of these sensors work on 5vdc. A one bar reads 0-5v in vacuum. A 2 bar reads 0-2.4 vacuum, 2.4-4.8 boost. 4.8=15PSI. A 3 bar reads 0-1.6v vacuum, 1.6-4.8 boost. 3.2=15PSI.. 4.8=30 PSI.

Too be technical, 1 bar = 14.7, 2 bar =29.4

I preset the PAC at 2.2vdc turnon so on a 3 bar=4 psi approx.

These voltages can be read by using a digital VOM monitoring the green center wire.

HTH

PS.. want stealth put the boost guage in the glove box and get a recall kit for it.

 

[pacecarta]

The reason it's different is because they both use a 5 Volt reference voltage...The 2 bar maxes out at 15 PSI and the 3 bar maxes out at 30 (roughly)...So you're stock boost gauge now reads double (15=30).

went and made up a pressure tester using my spray gun regulator and hooked it up before my autometer gauge tee (where it connects to the manifold lines)
this allowed me to vary the pressure and read the both gauges (better than doing it under boost at 90mph)


takes 10psi to light the first four bars (about 3lbs on gauge)
15lbs lights 8 bars (about just past 5lbs on gauge)
20lbs lights 11 bars (about 9 lbs on gauge)
25lbs lights 15 bars ( around 12lbs on gauge
30psi lights full scale (15lbs on gauge)

i plan on getting some white rub on number transfers from staples and rescale the numbers above gauge

 

[Razor]

Would be neat to make a vinyl/plastic transfer for the boost guage like an overlay. Think it would be a neat item to sell.

See the 2 bar at 0 psi= 2.4 volts. The 3 bar at 6-7 PSI = 2.4 volts so it takes about 10 PSI before it really starts registering. So your numbers are correct.

So if a 3 bar at 3.2=15 PSI.. a 2 bar at 3.2volts = 7-8 PSI

 

[HellOnWheels]

What, other than the stock boost gauge, is the stock 2-bar needed?


HOW

 

[Razor]

Only used for the boost guage.

 

[Slow91z]

Originally posted by Razor
Next you'll need a harness for the 3 bar this can be gotten from AC Delco or a junk yard.

You can also get the harness from Caspers.

http://www.casperselectronics.com/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=8687GN_splices

Don't know who would be cheaper (ok the junkyard, but I mean who's cheaper new).

 

[turbowannabe]

Off topic but..

My stock boost gauge reads way off(too high, I get boost readings at idle). Also, my stock tach is always maxed out(may not be related at all, but I thought i would mention it.). Could the high boost readings be caused by a faulty MAP sensor, and could this give me BLM problems if so? I don't mean to get off topic, but this is sort of what you guys are talking about and I won't need to make another post.

thanks
Dan

 

[pacecarta]

the map sensor is just for the boost gauge , nothing else runs off it (the digital dash cars dont even have one)

high blms are indicating a lean mix, unmetered air getting in after the maf (vac hoses , maf hose, pcv valve , egr, sol )or you have too low fuel pressure (blocked injectors ) .
what is your IAC counts and O2 CC's ,


my tach is off , scanmaster and scan tools show its off (high) by few hundred rpm at idle and gets worse as it goes up (I dont trust it and wouldnt look at it it even if it was correct) but my boost was dead on (before the3bar)

john spina at caspers fixes the stock gauges and does an outright exchange so they work the way they should

 

[turbowannabe]

I've replaced bassically all of the vac lines thinking it was a vac leak and still no luck. I've got 50lb injectors that are 3 years old and have engravings on them from 2001 when they were flow tested and marked what they rated at. I've tried a couple different chips and still no luck. I'll probably replace the egr gasket just for good measures.

Iac is in low 60's, CC's are all over the place

I don't really want to get too far off subject and jack the thread, so sorry if anyone doesn't like me posting here.

-Dan

 

[pacecarta]

this thread was basically answered
probably should have been in general tech forum
i tried to edit but timed out so heres edited post

if you search BLM youll find more to read
btw your IAC seem high if that at idle warm ,cross counts shouldnt vary much , remember IAC CCC and BLM really only matter at idle , have you tried a new O2 sensor?


EDITED LATE
my mian problem arose when installing the alky kit which needs the 3bar map sensor , my dash boost gauge was dead on and after razor explained it i understand fully why (could write a paper on the subject now)
the map sensor is just for the boost gauge , nothing else runs off it (the digital dash cars dont even have one)

high blms are indicating a lean mix, unmetered air getting in after the maf (vac hoses , maf hose, pcv valve , egr, sol )or you have too low fuel pressure (blocked injectors ) .
low BLM is too rich (excessive fuel pressure or incorrect chip for your injectors )
what is your IAC counts and O2 CC's? ,

my tach is off , scanmaster and scan tools show its off (high) by few hundred rpm at idle and gets worse as it goes up (I dont trust it and wouldnt look at it it even if it was correct)
john spina at caspers fixes the stock gauges and does an outright exchange so they work the way they should

 

[Razor]

Originally posted by turbowannabe
Off topic but..

My stock boost gauge reads way off(too high, I get boost readings at idle). Also, my stock tach is always maxed out(may not be related at all, but I thought i would mention it.). Could the high boost readings be caused by a faulty MAP sensor, and could this give me BLM problems if so? I don't mean to get off topic, but this is sort of what you guys are talking about and I won't need to make another post.

thanks
Dan

Dan I wrote an article in the library section of www.T6P.com relating to chasing the BLM's.

IAC needs to come down, into the 20's at idle.. actually anything above zero is ok.. just not far off. 60 only if AC on, lights on, fans on, all the possible loads at idle. In park, car at 160 degrees.. nothing turned on.. 20's. Open the throttle blade a little and readjust your TPS.

Your BLM condition.. thats a totally different animal.. if you need help with it, let me know. I've worked on plenty of these cars with high blm issues. Hope you read my article.. employ the advice.. and if all that fails, contact me. I like the obscure stuff.

Cross counts have no bearing on your BLM issue, unless your O2 sensor is bad. Only use original AC Delco parts whenever possible.

 

[Razor]

BLM..

http://www.t6p.com/forums/showthread.php?t=1127

HTH

 

[ijames]

Too be technical, 1 bar = 14.7, 2 bar =29.4

1 bar = 14.5 psi, not 14.7
1 bar is not equal to 1 atmosphere, 1 bar = 1 kilogram / meter^2 which just by coincidence comes close to 1 atm or 14.7 psi