Map Sensors

M

MAK

New member
I bought a map sensor recently for my Ty. It was supposed to be a 3 bar. I also recently installed a 20g turbo and had Eric do up a Velosyty chip for me (set for 3 bar). When I started it up yesterday it idled great but would barely get up to 40 mph. I limped it home, took out the Velosyty chip and reinstalled the stocker and the Ty ran great.

This is the confusing part: if the map sensor I bought was a 3 bar, wouldn't the Ty run poorly with the 3 bar and stock chip?

I am doubting it actually is a 3 bar. This would certainly explain why it ran rough with the Velosyty chip.

If they did, in fact, send me a 2 bar, does anyone have a good 3 bar they could get to me quickly? I am dying to get this thing running to its' full potential.

Thanks.
 
Throws

Throws

Active member
Re: Map Sensors

MAK said:
I bought a map sensor recently for my Ty. It was supposed to be a 3 bar. I also recently installed a 20g turbo and had Eric do up a Velosyty chip for me (set for 3 bar). When I started it up yesterday it idled great but would barely get up to 40 mph. I limped it home, took out the Velosyty chip and reinstalled the stocker and the Ty ran great.

This is the confusing part: if the map sensor I bought was a 3 bar, wouldn't the Ty run poorly with the 3 bar and stock chip?

I am doubting it actually is a 3 bar. This would certainly explain why it ran rough with the Velosyty chip.

If they did, in fact, send me a 2 bar, does anyone have a good 3 bar they could get to me quickly? I am dying to get this thing running to its' full potential.

Thanks.
Click to expand...

I've got a 20G and the VeloSyty chip... you're in for a treat! :tup:

-P
 
M

MAK

New member
Re: Map Sensors

The one I bought has 9576-E 8 and PBT-GF30 stamped on it. This was to be the 3 bar.

I might get laughed at for this next question but I need to know and I can't find the answer:

There seems to be 2 identical or very similar map sensors on our trucks - one on the firewall (boost gauge line connected) and another to the right of the block (vacuum line connected). Which one needs to be changed to the 3 bar and what exactly does each one control? There it is, laugh away......:oops:
 
Chest Rockwell

Chest Rockwell

Active member
Re: Map Sensors

Got time to take a pic? Could you be mistaking the EGR solenoid for another MAP sensor? They're located on the same bracket.
 
M

MAK

New member
Re: Map Sensors

Chest Rockwell said:
Got time to take a pic? Could you be mistaking the EGR solenoid for another MAP sensor? They're located on the same bracket.
Click to expand...

I would have to get the picture tomorrow. FWIW, the sensor I changed is on the firewall (velcro) and it has a line attached to the nipple for the boost gauge. It is a map sensor, for sure. There just appeared to be 2.
 
M

MAK

New member
Re: Map Sensors

syclone809 said:
The map sensor that needs to be changed is right next to the intake manifold
Click to expand...

On the bracket? Wow....how did I miss that one......:banghead:

So any idea what this other sensor with the hard line attached is? It is to the rear of the upper intercooler. Mine is attched to the firewall by velcro but I assume it was somewhere else at some point.

I am guessing both were 2 bar sensors from the factory? I hope so.

Thanks for the help.
 
M

MAK

New member
Re: Map Sensors

nallj92 said:
a simple search came up with this thread.

http://www.syty.net/forums/showthread.php?t=87320&highlight=bar+map+sensor

we only have 1 map sensor on our trucks, the other thing you are currently describing is not a map sensor.

If you are wondering what the other item would be, a vac line diagram is helpful.

http://www.syty.net/forums/showthread.php?t=3045&highlight=vacuum+line+diagram
Click to expand...

I saw the first thread before. Not much use because the one I replaced on the firewall was definitely the same shape and plug type as a map sensor (whether it functioned as a map sensor or not) and I no longer have it to reference the numbers.

The second thread would have been very useful but I did not see it before. Now the great mystery...what the hell did I replace? Anyone? It is not part of the vacuum system, therefore, it is not on the diagram. Thanks for the link.
 
M

MAK

New member
Re: Map Sensors

To clarify, the part I changed out is identical to the map sensor next to the egr solenoid and intake. It has the same plug, nipple, shape....everything, although I can not confirm the part number. It does have a hard line running to the nipple from somewhere behind or under the intake/upper intercooler - I will trace it in the morning. Does anyone have an idea what this part is for and what it is?
 
DaveP

DaveP

Active member
Re: Map Sensors

MAK said:
Now the great mystery...what the hell did I replace? Anyone? It is not part of the vacuum system, therefore, it is not on the diagram.
Click to expand...

Our trucks only have one MAP sensor as-produced. The one on the LR of the engine on the bracket with the ignition coil. However, I have a thought:

What if a previous owner installed a 3bar sensor for the engine management system? The stock sensor also provides the signal to the instrument cluster for the factory boost gauge. With a 3bar sensor, the "zero" point moves down to about 7.5" vacuum reading. Perhaps this annoyed the previous owner enough that he installed the original 2bar and wired it to just the stock gauge to re-establish some semblance of accuracy.

And now you have two MAP sensors. One for the engine, one for the boost gauge.
 
Last edited:
M

MAK

New member
Re: Map Sensors

Holy cow, Dave...you might be onto something. I sure hope you are right. I am so confused as to what that sensor was doing over there on the firewall. It has an OEM style plug running to it so I figured it was a factory part. So now that I have a bigger turbo and the Velosyty chip (set for 3 bar), if your idea is correct, won't I need (2) 3 bar sensors?
 
DaveP

DaveP

Active member
Re: Map Sensors

MAK said:
now that I have a bigger turbo and the Velosyty chip (set for 3 bar), if your idea is correct, won't I need (2) 3 bar sensors?
Click to expand...

The gauge is calibrated for a 2bar. So if you want zero on the gauge to be zero, you need a 2bar powering the gauge. You can also do "mental math" if the gauge is powered by a 3bar. In this case, zero is about 1/3 into the vacuum area. And full scale boost is 29.4psi.

But the cluster gauge is not very accurate. I'm not sure it's worth the effort to try to calibrate and retain. I'm not sure I've ever seen discussion regarding a separate 2bar for the dash gauge when changing engine management to a 3bar sensor. Kind of 'new' thinking.

Trace the wires. See what it's for, and let us know.
 
M

MAK

New member
Re: Map Sensors

DaveP said:
The gauge is calibrated for a 2bar. So if you want zero on the gauge to be zero, you need a 2bar powering the gauge. You can also do "mental math" if the gauge is powered by a 3bar. In this case, zero is about 1/3 into the vacuum area. And full scale boost is 29.4psi.

But the cluster gauge is not very accurate. I'm not sure it's worth the effort to try to calibrate and retain. I'm not sure I've ever seen discussion regarding a separate 2bar for the dash gauge when changing engine management to a 3bar sensor. Kind of 'new' thinking.

Trace the wires. See what it's for, and let us know.
Click to expand...

Will do, Dave. Thanks a million. I am guessing the map sensor for the engine is the only one that needs to be a 3 bar. So, from what you are saying, if the other sensor is just for the boost gauge and is calibrated for a 2 bar sensor, it will need to remain a 2 bar sensor to be accurate? I am fine with that....no need to change it. I will trace the wires and hard line in the morning and post back.

Leave it to my damn luck to run across some crazy thing hardly anyone has heard of. And I am sure everyone on here thought I was crazy for saying I had 2 sensors......:rotf:

Wait....confused again.
 
M

MAK

New member
Re: Map Sensors

Dave - I got my gauges mixed up. The cluster gauge is calibrated to a 2 bar, the pillar gauge also had a 2 bar. If I change the engine sensor to 3 bar it will cause the cluster gauge to be evn more inaccurate - I get that part. What should I run for the pillar gauge sensor? Since it had the 2 bar to begin with, should I leave it with a 2 bar or go with a 3 bar to show the higher boost levels? Is the pillar gauge affected by this?
 
DaveP

DaveP

Active member
Re: Map Sensors

MAK said:
Is the pillar gauge affected by this?
Click to expand...

Normally, it's not. The overwhelming majority of pillar boost gauges are mechanical. They have a tube to them connected directly to the upper manifold. They are not electrical, so are not influenced by changes in MAP sensors.

If on the very odd chance the pillar gauge is electrical, it could well use the second "mystery" MAP sensor. But I doubt it. You're going to have to sleuth it out. Follow wires and chit, and school yourself as to what you've got.

You'll get it.
 
M

MAK

New member
Re: Map Sensors

Thanks, Dave. I am almost certain the mystery map is for the pillar gauge due to the hard plastic line attached to it. I will take a good look at it tomorrow. I need bed now. I have been up WAY to long to be thinkng this damn hard. Thanks for the help.
 
S

Syclone22

Member
Re: Map Sensors

Well not all pillar boost gauges all mechanical
Autometer has a electric boost gauges that uses
a map sensor for pressure signal maybe the sensor
you have on the firewall was for this type of unit !!! :tup:
 
You must log in or register to reply here.
Top