1JZGTE ISCV & MAP Sensor Questions...

[JZA70 R]

What is the maximum boost the 1JZ map sensor is capable of reading?

Reason i ask is because my supra is booked in for its first tune with the power fc dec 13 and... i cant actually control boost below a minimum of 1 bar or 14 - 15 psi... and this is on a warm day so im anticipating on cooler days ill be seeing anything up to 18 psi.

I want to know if the map sensor will be able to measure this boost and pass the info on to the power fc? ...or will it go dumb at 1 bar and possibly cause troubles with tuning.

If so what are my options?

---

About the ISCV, can someone tell me how this contraption works. I mean i know what it does, but i had it apart the other day for a clean and i cant work out how it actually regulates air. i dont understand how the valve inside it works.

Thanks.

[wilbo666]

The ISCV is controlled by the ECU to adjust idle...

It is the ECU's way of cracking open the throttle slightly to allow more air past the throttle body and hence into the engine. There is a stepper motor that moves a section in-out making the effective size smaller or larger, I'm sure if you have a look at it you will work it out...

The rubber bit with flaps is a one way valve to stop boost going back through the ISCV when you are on boost.

Cheers
Wilbo

[Mr DOHC]

ppl have run 19psi thru stock turbos on stock ecu's {fcd tho} so i know it can do at least 19psi

[JZA70 R]

Mr DOHC do you realise what you just said?

[thechuckster]

fwiw, map sensor ranges seem to come in 0.5 and 1 bar increments... my MS ECU's all have 250kpa (or 2.5 bar) sensors that can cope with 21psi boost. There are sensors with greater ranges (e.g. 300 and 400 kpa - 28 and 43psi respectively) available from electronics supply places.

Map sensors used in some of the original MS ECU's (and we're talking about uber-cheap off-the-shelf sensors) were 1.5 or 150kpa sensors - 7psi boost

Anyway - ending this minor digression, it's quite likely that the MAP sensor in the denso casing is similar to the others on the market given that they behave electrically similar so it's most likely rated for either 14psi (which Phil has disproved) so more likely 21psi.

[Mr DOHC]

Mr DOHC do you realise what you just said?

yes

why??

[JZA70 R]

So your saying the map sensor can see, measure and provide a correct voltage for 19 psi using a fuel cut defender which actually clamps the maps voltage (psi) below 14.5 psi?

I know just because the ECU does not like over 1 bar that the map sensor cant measure over one bar, but i also know just because you can trick the ecu into accepting a real 19 psi that the map sensor is providing a correct voltage for 19 psi.

[triptek]

From memory 1.1 or 1.3 bar comes too mind. I think the 1.1 is the 1jz and the 2jz is a 1.3 bar. This is why my mate put a 2jz map sencer on his jza70 with power fc. This is obviously fuel cut, dunno the limits of the map snecer though.

[Mr DOHC]

So your saying the map sensor can see, measure and provide a correct voltage for 19 psi using a fuel cut defender which actually clamps the maps voltage (psi) below 14.5 psi?

I know just because the ECU does not like over 1 bar that the map sensor cant measure over one bar, but i also know just because you can trick the ecu into accepting a real 19 psi that the map sensor is providing a correct voltage for 19 psi.

how dare u prove me wrong, prepare to duel

[JZA70 R]

hehe, ive been searching for the answer, i would have thought someone would know by now it not like no one has met the limit of the 1JZ map sensor before.

Before i started searching i was sure the 1JZ was a 2 BAR sensor that could read to 1 BAR and the 2JZ sensor was a 3 BAR unit that could read to 2 BAR absolute.

But im not so sure.

And as for the ISCV if someone could explain how that funny valve actually does its thing, or has a diagram that would be cool.

[wilbo666]

And as for the ISCV if someone could explain how that funny valve actually does its thing, or has a diagram that would be cool.

The ISCV is controlled by the ECU to adjust idle...

It is the ECU's way of cracking open the throttle slightly to allow more air past the throttle body and hence into the engine. There is a stepper motor that moves a section in-out making the effective size smaller or larger, I'm sure if you have a look at it you will work it out...

The rubber bit with flaps is a one way valve to stop boost going back through the ISCV when you are on boost.

Cheers
Wilbo

Not a good explanation?

Also

http://www.cygnusx1.net/Supra/Librar...on=FI&Page=106


http://www.cygnusx1.net/Supra/Librar...on=FI&Page=107



Cheers
Wilbo

[JZA70 R]

Wilbo thanks for your help. I initially said i knew what the ISCV did and how it does its thing, its the valve im curious about (the 7M diag doesnt help that)... However going by the diag i might hook power up to it next time its off to see how it all works.

Thanks again.

[Mos]

The two centre tapped windings and the rotor form a stepper motor (ie it has distinct steps and needs to be "stepped" in sequence to rotate).
The rotor either has a thread that runs into the valve shaft (making the valve shaft move up and down as it rotates), OR the thread is stationary and the rotor makes the valve shaft rotate around the thread to make it move up and down. (I've been meaning to pull one apart...).

The latest JZS147 Aristo 2JZ-GTE map sensor tops out at approximately 17.5 PSI (1.2bar or so) - this is in addition to the approximate 10 PSI of vacuum (0.7bar). These are both measured values, therefore factual. There may be variations with different engine versions.
Given the factory 2JZ runs more pressure than a 1JZ (for various values of "1JZ"), I would expect the 1JZ map sensor to have a lower range.

Mos.

[JZA70 R]

Thanks mos.

[e30-323ti]

There is an epically long thread on this somewhere with logged outputs from both 1JZ and 2JZ sensors from a P-FC IIRC

I'm sure it was manny, but can't find the thread to save myself, sorry.