AUSTRALIAN X-TRAIL FORUM :: DIY Guides & How To :: ECU/MAF interceptor DIY ~ Runboard



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Australian X-Trail Forum DIY Guides & How To
ECU/MAF interceptor DIY

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MosaicT30

Date Registered: 09-2009
TOTAL POSTS: 17

ECU/MAF interceptor DIY

I have designed and built an Interceptor to control a 'problem' in my 2005 T30 Xtrail GT ECU behaviour.

Using the Blazt consult II cable logging I have discovered the following:

My Exy goes WOT open loop and .9 o2 rich (.45 is stoich) by 1700rpm or 1.04 tps. Now it ain't a normal exy, it's the sr20VET GT. With that WOT setting I can't cruise economically. In fact I get only 15 mpg on RON 95, the best available fuel.

What the mod does:

The circuit takes input from the MAF sensor, O2 sensor and the Boost sensor. Based on air flow it decides when to insert its control into the ECU's behaviour. Based on the air flow Voltages the RPM range of 2000 thru 3500 is the mods active region.

The mod has calibration rheostats which allows for altering of the rpm range and boost range sensitivity. It is preset for stoich mix at .45 O2 volts.

The main calibration (done while driving) allows for setting the minimum amount of MAF voltage reduction to force a lean cruise condition when ECU is at WOT below 3500 RPM. The mod oscillates the MAF voltage to cycle lean/rich averaging around .45 O2 volts. This oscillation is slightly damped to simulate normal a/f correction over a 1 to 2 second period.

In heavy acceleration or load the boost sensor will cause the mod to revert to stock ecu behaviour once around 1.5 psi boost is detected.

Thus I can cruise hovering around stoich. and still have rich boost on tap.

I will be hooking this circuit up this weekend to do some testing.

Anyone have any comments or suggestions?

15/Oct/2009, 5:05 am

Robbo0001
X-TRAIL LEGEND

Date Registered: 07-2008
Location: Brisvegas, Australia
TOTAL POSTS: 533
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Re: ECU/MAF interceptor DIY

Are these high settings factory preset? Have you been able to confirm that these figure are indeed "base line" for the GT (with 1 or two other cars), and not a possible error or fault in your vehicle?

Dont get me wrong,you sound like your all over it emoticon

But it would suck to do all this and discover a faulty connection or sensor at a later date. And as you know...the ECU has a a habit of not recording every fault, so no fault code necessarily has to show up.

Is this a variation of an adjustable "pot" series of resistors placed on the outputs of the MAF/O2 and airflow? Or a circuit card/programmable set-up?

If its a circuit card...and someone starts talking binary or something...I am outta here
emoticon

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Dave
02/T30 TI (C)

15/Oct/2009, 7:02 am

Revhead Kev
X-TRAIL HOLIC

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Date Registered: 10-2006
Location: Mona Vale, Sydney, AUSTRALIA
TOTAL POSTS: 2952
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Re: ECU/MAF interceptor DIY

Hi mosaic,

Very ambitious of you to make this circuit.
Sounds like you are using a PIC of some kind.

As Dave has asked, I too would be interested to know if you have hooked your Blazt to another GT to see if the same happens on it as yours.
I am sure you could find another GT somewhere over there by joining a few other local Xtrail forums or groups and posting the question for someone to accept an invitation to allow you to test theirs if you went to them.

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Kev X450(c)
2003 Titanium Ti Luxury Series 1

15/Oct/2009, 7:49 am

jalalski

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Date Registered: 02-2004
Location: SUTHERLAND, SYDNEY
TOTAL POSTS: 16452
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Re: ECU/MAF interceptor DIY

The guys are making a valid point. I didn't come across a GT owner previously who reported poor fuel consumption, so it could well be a fault with your xtrail that needs to be checked out.

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15/Oct/2009, 8:31 am

MosaicT30

Date Registered: 09-2009
TOTAL POSTS: 17

Re: ECU/MAF interceptor DIY

I certainly think sumthin is up with the WOT from 1.04 tps, my investigations reveal that WOT is supposed to be at 3.4 TPS or so for sr20ve.

I am gonna pull down the ECU to see if its been modded. The exy is a JDM from Tokyo and given the number of velcro pads and small screw holes in the front interior makes me feel that the prev. owner diddled with it.

It has a 2.5" s/s cat back and performance (red) coil overs running 18 " rims and 50 series rubber......when i got it.

BTW...the circuit ain't binary...its an analog computer. All hardwired for this specific capability. Based on a bunch of op amps. I certainly can't just put a resistor to gain specfic trigger points and progressive A/f control with boost safety triggers.

Can u guys point me to a link showing how to access the ECU on a T30 series II please? I'll need it to wire in the intercept anyway.

thx

15/Oct/2009, 1:34 pm

Revhead Kev
X-TRAIL HOLIC

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Date Registered: 10-2006
Location: Mona Vale, Sydney, AUSTRALIA
TOTAL POSTS: 2952
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Re: ECU/MAF interceptor DIY

Here is what it looks like behind the glovebox.

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Kev X450(c)
2003 Titanium Ti Luxury Series 1

15/Oct/2009, 11:34 pm

MosaicT30

Date Registered: 09-2009
TOTAL POSTS: 17

Re: ECU/MAF interceptor DIY- Ecu not stock?

Guys,

The ECU is labelled "IMPUL - HI-Power CONTROL UNIT" and their appears to be some modification to the harness as I see some black electrical tape wrapping wire joints in the harness just before the ECU connector which I hardly think is stock Nissan. I found this link:

Impul site

And I found this as well:

Skyline with Impul

The green tamper paint on the ECU screws show that the ECU has been opened. The IMPUL label appears to be a stuck on plate.

My take on this is: The previous owner Chipped the stock ecu with an IMPUL daughterboard. Clearly, WOT by 1700 RPM ain't for cruising. I have not pushed this exy to find out if the RPM limit, boost limit, or the Speed limiter is gone, nor have I monitored the CAM hydraulic solenoids for non standard behaviour. I suppose simply placing LEDS on the CAM Solenoids so that they display on the dashboard can tell me whats happening there.

Trying to track the correct wires in the ECU harness looks a bit tough.

Are there any pinouts I can use as a possible starting point? Or should I just use a DMM and try to trace by continuity?

18/Oct/2009, 5:11 am

cooch t31
X-TRAIL HOLIC

Date Registered: 06-2008
Location: Blue Mountains, NSW
TOTAL POSTS: 1435
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Re: ECU/MAF interceptor DIY

This might sound a bit drastic but have you thought about replacing the ECU. Cost might be a factor so maybe check out your wrecking yards for one.
It may be a little less of a headache.
Just reading what you have or are about to do makes my head hurt. emoticon

Tony

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Tony X-891c
2008 T31 St
HERE is my X Trail

18/Oct/2009, 6:16 am

MosaicT30

Date Registered: 09-2009
TOTAL POSTS: 17

Re: ECU/MAF interceptor DIY

Not many Exy GT's here ..prob less than 10 nationwide...so wrecking yards are out.

Further, there is a good chance that the chipped ECu is performance minded. Thus I may have extra boost, and no fuel cut .

I will be installing the Circuit I built tomorrow. I have traced the sensor wires into the ECU harness. I am mounting the Display LEDs and making a tiny wire harness out of regular RJ11 phone wire & jacks.

Hopefully tomorrow... this Exy GT will have a lean cruise which I can define in terms of RPM range and closed loop control.

18/Oct/2009, 2:29 pm

Robbo0001
X-TRAIL LEGEND

Date Registered: 07-2008
Location: Brisvegas, Australia
TOTAL POSTS: 533
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Re: ECU/MAF interceptor DIY

It certainly sounds like that a previous owner has "done some digging around" already in the ECU. Its a pity that no documentation or information came with the car so you could actually know whats been done.
It would be pretty safe to say that very few of the GTs wiring actually corresponds to anything in Australia, have you tried the Sentra forums for guys who have done a half-cut swap out, and possibly hacked into the ECU harness? (not program)

Have you tried ringing around any local installers (who may have actually done the original IMPUL job) to see if one of them knows what was attempted?

quote:
nor have I monitored the CAM hydraulic solenoids for non standard behaviour. I suppose simply placing LEDS on the CAM Solenoids so that they display on the dashboard can tell me whats happening there.

I will readily admit that this has me stumped emoticon

but I understand that you are trying to lean out the fuel mixture while cruising, but still have the opportunity to dump more fuel in on boost.
Be very interested in how you go...

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Dave
02/T30 TI (C)

18/Oct/2009, 2:52 pm

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