1JZGTE ISCV & MAP Sensor Questions...

[thechuckster]

is it the map sensor that has a max of 1.9-2.0 bar (absolute) or the electronics that interface with it at the ECU? It just seems odd that Denso would make many slightly different map sensors when it's a lot cheaper to do any control work in the ECU firmware.

[Mos]

The transducer in the sensor is different. (Or I would expect it to be different given the pressure range mapped to the 5V voltage range).

The transducer effectively measures the difference between two pressures - in the case of absolute sensors one of the pressures is a vacuum reference of a certain value compared against the pressure of choice.
The 2JZ sensor went from somewhere around -10PSI (either 0V or as close to 0 volts as it could get) to somewhere around 17.5PSI (5V or as close to the supply voltage as it could get).

The main reason for using a sensor of a certain range is resolution. The higher the range, the smaller the voltage change for a given pressure change.
There is little point using a 2 bar absolute sensor for atmo engines (extreme example) as only half of the range of the sensor would be utilised - but in theory it should be cheaper, because you double your usage for one particular part number. The same theory follows for a 12PSI vs a 17PSI sensor - if the engine is not designed to run outside of the range, then the sensor doesn't need the extra range.

Given that pressure sensors can be had cheaply in any (stepped) pressure range you may desire, I have no doubt that Denso can get *any* specific range they want custom made in the 20,000+ runs of exotic engines with no price penalty. Denso already has microcontrollers made to their specifications at the packaging level - the silicon die, in some older micros, appears to be rotated 90 degree inside the resin casing to make sure nothing off the shelf will replace it.

The other aspect you mention - ECU firmware - might not yeild the benefits you suggest. If an ADC has a 5V range, using the entire range gives the best resolution for engine mangement. Obviously you could just use a 2.5V chunk of the range and then scale the result in software, but you have lost half of your resolution. You could also scale the 2.5V back up to 5V in hardware, but that will attract extra costs that could easily be avoided by using a sensor with the correct output range.

Thoughts?

Mos.

[thechuckster]

yup ... i understand the pointlessness of using a >100kpa sensor for a NA engine ;-)

i guess i've become somewhat conditioned by the megasquirt experience - with 250kpa-capable sensors at retail for as little as USD$15/unit (from 1000+ lots) it just seemed odd that they would do different batches for 170kpa, 210kpa, 250kpa etc... particularly as Toyota have a habit of re-using a lot of hardware across their model range.

i neglected to consider output resolution - my bad <doh!1>

The MS-1 units do an 8bit D/A conversion of the MAP sensor 0-5v output which seems to satisfy most users - the speed-density algorithm they use is optimised with that accuracy from the Freescale MAP sensor anyway so there's no rescaling of the data for non-turbo operation.

[chris davey]

I was under the impression that 1jz = 1 bar, 2jz = 1.2bar. Using a 2jz map sensor is a common upgrade in the US to get around boost cut if you don't want to go too crazy but are just hitting the boost cut occassionally.

[JZA70 R]

well in a week ill all let you know if my tune goes smoothly. its as simple as watching the boost readout from the map sensor on the controller. if it reads past 1 bar then its a great start.

[Ribfeast]

Around 1 bar for the 1JZ (of positive/boost pressure). And about the same the other way. Best bet would be to apply increasing levels of pressure to it, and log the corresponding voltage output. I'd be keen to know for sure.
The stock sensor will not allow the PowerFC etc to add any more fuel past around 14 or 15psi, so if you plan to use the stock sensor and run more boost, make sure you add additional fuel to handle it.
I run 18psi fine in my 1JZ on stock map sensor and ECU.

[JZA70 R]

I might give toyota parts a call to see what a 2JZ map sensor goes for trade. Hope the PFC is compatible with it.

[JZA70 R]

err i just realised how easily i could have & can answer my own question regarding the map sensor.

car + pfc + air compressor = answer. (car off and low pressure obviously)

ill install the pfc and hook up the air compressor and give this a try tonight.

[JZA70 R]

ok so here i am, in my car, laptop in hand, pfc plugged in, bonnet popped, air compressor line plumbed directly into the map sensor. all sweet.

ive got the ignition turned on, in the pfc i go to MONITOR > 1 CHANNEL > 1 BOOST > and straight away ive got a boost figure of -28~30 mmHg. Weird, car isnt running so i pull the compressor line off. its still hovering around -28 to -30 mmHg. if i blow almost all breath power into the map line and it changes to 0 .00 kg/cm2. weird again.maybe my map sensor is stuffed?

so i plum the compressor back in and turn it on. the boost monitor on the power fc controller starts climbing.

it stops at 1.16 kg/cm2. or converted thats 16.5 psi or 853.25 mmHg or 1.14 bar.

i slowly let the air out of the compressor and watch the figure fall back to 28~30 mmHg.

voltage information is as follows.
ambient pressure
-28 mmHg = 2612 mV (2.6v) PIM volts & 0.00v 'BOST'

+1.16 kg/cm2 = 4.912 mV (4.9v) PIM volts & 3.55v 'BOST'

+0.00kg/cm2 = 2700mV (2.7v) PIM & 0.00v 'BOST'
(i had to have the compressor slightly charged to yeild that last line of figures.)


pressure sensor pdf.
http://www.autoshop101.com/forms/h35.pdf

[chris davey]

good research +11

[JZA70 R]

ok so after talking to a mate with the exact same setup as me (car and ecu) i had another play tonight.

there are five mip settings available... one is standard (yeilds the .5 psi vacum @ ambient pressure)

another is SW20 which yeilds a POSITIVE pressure reading of .23 kg/cm2! @ with the car turned off!

the other 3 are 'apexi', option1 & option2. all three read .3X kg/cm2.

i did not get to measure the map sensor in these modes tonight as it was late. ill do that tomorrow.

the good news is my friend said his pfc was tuned with the SW20 option selected. and with the car turned off his also reports +.23 kg/cm2. so i think my map sensor itself is fine, and that there are some discrepencies with this ecu in our climate? who knows.

anyway... im gonna see if a 2JZGTE map sensor is a direct plug n play, and if it is ill find out what max pressure it reads.

[thechuckster]

can you measure the raw voltage output from the sensor?

[JZA70 R]

yes, i believe that what the 'BOST' figures above is referring to.

[JZA70 R]

update.

i tested atmo and max map pressure in the 3 available preset modes on the power fc and put together the following information.

PIM VOLT > NORMAL
...ATMO -16 MMHG (2646 MV PIM) (0.00 V BOST)
MAX +1.16 KG/CM2 (4916 MV PIM) (3.55 V BOST)


PIM VOLT > SW20 NORMAL
ATMO +0.25 KG/CM2 (2646 MV PIM) (0.77 V BOST)
...MAX +1.84 KG/CM2 (4916 MV PIM) (5.61 V BOST)


PIM VOLT > APEX PRESS
ATMO +0.38 KG/CM2 (2646 MV PIM) (1.17 V BOST)
...MAX +1.88 KG/CM2 (4916 MV PIM) (5.74 V BOST)


PIM VOLT > OPTION1 SAME AS ‘APEX PRESS’ MODE
PIM VOLT > OPTION2 SAME AS ‘APEX PRESS’ MODE

So it appears that 'SW20 NORMAL' and 'APEX PRESS' mode yeild more resolution from the map sensor, but im not so sure as their maximum readings was achieved with only 1.1 bar of regulated pressure being fed into the map. so they cant possibly be even half accurate.

To simplify that again, in NORMAL mode i would max the map out at 1.16 bar, stop the compressor and switch through the available modes. each one i swapped to would instantly read maximum pressure (1.8 kg/cm2) despite the compressor pressure of 1.1 kg/cm2.

Im still waiting on someone to loan me a 2JZ map sensor so i can get some readings from that.

From the data ive collected it appears the 'NORMAL' mode with a max map pressure of 1.16 bar, would be the best mode to tune in as its the most accurate.

[JZA70 R]

I spoke to Manny the other day, he confirmed the different modes were directly relevant to the map sensor you were using.

Normal - being the factory 1JZ-GTE map sensor.
SW20 Normal - being a specific generation map sensor from a 3S-GTE SW20
(this is a common sensor to use in japan and apparently is the same as the 2JZ-GTE map sensor.)
APEX PRESS - this is for when you use the apexi power fc boost control kit. a apexi map sensor is supplied with the kit.

the optional modes are for a after market map sensor that you need to calibrate in these 2 optional modes.

Ive decided to buy the boost control kit for the power fc and use the 3 bar map sensor that comes with it. about $380 delivered from nengun.