Turbo Pressure Sensor

Q&A regarding engines, turbos, and intercoolers and power upgrades

Postby erolit » Mon Feb 06, 2006 7:20 am

Nice bump.

The 5s engine is totally, completly different to the 3s.
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1991 Aus-Delivered ST185

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Postby epinasty » Mon Feb 06, 2006 12:18 pm

The blocks are the exact same. The head is different and i assume that makes a lot of other things different but when something as large a part of the engine as the block is the exact same. Then the engines are pretty similar when we are talking about all internal combustion engines.
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Postby AZautoXr » Fri Apr 10, 2009 4:14 am

erolit wrote:TPS = Turbo pressure sensor. on the st185 it provides a pressure signal to the ECU from which the ECU calculates fuel cut. It also has a separate wire connecting it to the stock boost gauge on the dash board.

Appart from these 2 functions it serves no other purpose. There is no pressure sensor based fuel/ignition corrections on an st185 ECU.

If you electronically disconnect it from your engine (ie you cut the PIM wire, unplug the sensor wiring harness etc.) the ecu will begin to calculate fuel cut based on the signal from your AFM & throttle position, and when you hit airflow based fuel cut you have to reset your ECU (by pulling a battery terminal). Basically dont do it.

It will also (by some means which i have yet to establish) pull ignition timing much more readily with the sensor electronically disconnected.

If you want to kill fuel cut, the best way to do is is to unplug the vacuum line from the TPS, and leave everything as it is. This is 100% effective with zero side effects (except for complete absence of pressure related fuel cut)

Elliott


I think this is what has happened with my car ('88 'Trac). I am going to try and disconnect the vaccuum hose and see if it cures the fuel cut and limp home mode that the car is experiencing when it hits stock boost. I sure hope it helps, because we spent 3 days trying to work around it, and it is no fun to autocross this way; guessing where max boost is while trying to see the course! :shock:
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Postby bccentaur3 » Fri Apr 10, 2009 5:12 pm

epinasty wrote:The blocks are the exact same. The head is different and i assume that makes a lot of other things different but when something as large a part of the engine as the block is the exact same. Then the engines are pretty similar when we are talking about all internal combustion engines.


In no way shape or form the blocks are the exact same. Yes they look similar but no way Jose..

Try to mount your awd transmission with the transfer case onto the block. It is impossible without grinding the block and transfer case a little. Well a lot on the block and a little on the transfer case.

Yes they are both cast iron but thats about it. Internally they are obviously different there too, but NO a 5s is not the same as a 3s block.
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Postby Kcman91gts » Fri Apr 10, 2009 5:22 pm

The one on the bottom is the turbo pressure sensor with the vaccum hose and those wierd white attachment in the line . the top on is the AC vsv which runs to the AC idle up vsv which sits mid firewall attached to the center of the strut bar .
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Postby sbart83 » Sat Apr 11, 2009 3:40 am

yes that is correct. i think throttle position sensor when i see or hear TPS.
the turbo pressure sensor is the unit that the bottom green arrow is pointing to. it does say something like "turbo pressure assembly". IIRC it's a greenish label. top arrow points to the 2 vacuum hoses that go to the a/c idle up valve, center firewall as described above.
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Postby built2run » Sat Apr 11, 2009 7:46 am

it also takes a baro reading just b4 cranking so there are 3 functions of the MAP sensor; it has nothing to do with the A/C
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Re:

Postby Rallly » Fri Dec 16, 2016 5:41 pm

91 Celica AllTrac oem turbo

After disconnecting the rubber hose(blocking it with a bolt) that goes to the turbo pressure sensor, my fuel cut has been gone, YAY:)
With the nipple capped on the sensor side my oem boost gauge is always showing MAX boost in my gauge cluster.

With the nipple NOT capped, oem boost gauge goes up and stays at 1/4.

Car seems fine both ways but I wonder if with it capped showing full boost on cluster if this will alter what the ecu does with fueling?

Any ideas?




erolit wrote:TPS = Turbo pressure sensor. on the st185 it provides a pressure signal to the ECU from which the ECU calculates fuel cut. It also has a separate wire connecting it to the stock boost gauge on the dash board.

Appart from these 2 functions it serves no other purpose. There is no pressure sensor based fuel/ignition corrections on an st185 ECU.

If you electronically disconnect it from your engine (ie you cut the PIM wire, unplug the sensor wiring harness etc.) the ecu will begin to calculate fuel cut based on the signal from your AFM & throttle position, and when you hit airflow based fuel cut you have to reset your ECU (by pulling a battery terminal). Basically dont do it.

It will also (by some means which i have yet to establish) pull ignition timing much more readily with the sensor electronically disconnected.

If you want to kill fuel cut, the best way to do is is to unplug the vacuum line from the TPS, and leave everything as it is. This is 100% effective with zero side effects (except for complete absence of pressure related fuel cut)

Elliott
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Re: Turbo Pressure Sensor

Postby freddie » Sat Dec 17, 2016 3:11 am

Hey Brian, thanks, you have explained a mystery I have had. I have a JDM 165. No Turbo Pressure Sensor and no factory Boost Gauge (just a green light.)
I have always wondered what controls fuel cut. Now I know, the AFM. The green boost light must be activated the same way. Now all the pieces fall into place.
When I did a little mod. putting a direct air pipe/duct from the AFM to the turbo inlet and installing a hi-flow air filter, the turbo pressure went from 10psi to fuel cut which is 12psi and the engine runs better. The improvement was not so much as to air flow to the turbo, but the reading the AFM provides to the ECU.

It is going to be a bummer hooking up the AC when I put the 205 engine in lol.

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