2jz-gte (swap), idle up for a/c? [rare schematics inside]

[wilbo666]

im not up with 2j EFI systems so i may be wrong here, but wouldnt the factory setup simly open the idle speed valve more to increase the idle, with no change in throttle position?

dont see how it would be any different if you were to have another bypass system....

VVTi 2JZGTE has Fly By Wire Throttle (FBW).

There is no ISCV in VVTi 2JZGTE. The engine ECU simply opens the FBW throttle a little bit more to raise the idle RPM....

So that being the case the issue I can see is that the ECU has it's set idle, at lets say 650rpm... when you 'bypass' the throttle the ECU will see the increase in RPM, and I'd hazard a guess it will try and close the FBW throttle to compensate

You might be able to set the throttle stop so that it can't idle below 650, so that way it can't close the throttle more... but this might make the ECU throw an error code... something that will need to be checked

Cheers
Wilbo

[George]

I've occasionally read that something can be done to ETCS (trying to manually move the choke or to limit its movement) that choke position fails to correspond to controlling signal and the ultimate solution then is to buy another one.

Just have done an experiment with quite funny result. A pin "ELS" is present in 2JZ-GE's ECU as well as in one of 2JZ-GTE's, at the same location. I decided to try it, but what I got was idle drop by some 70 RPM. Pretty unexpected behavior )

[wilbo666]

Hmm I wasn't able to find ELS listed on the drawings I have at a quick look... which plug / pin was it meant to be on?!


Anyway I think I've come up with a solution for you!

If I was in your position what I would look at doing is using a small micro controller.

What do you think of the below plan?

2JZGTE VVTi AC Idle Up:
-Sample output of the TPS via ADC
-In normal operation the DAC outputs the same voltage as the signal from the TPS
-If the AC is ON and then the minimum TPS value is raised as if the throttle is slightly open and the idle will be increased as required. This modified signal is then outputted via the DAC.



Cheers
Wilbo

[George]

The ELS pin isn't listed in the schematic given in this topic, but here at Toymods a topic exists where plenty of schematics is listed. Among others there's a fully translated 2JZ-GTE schematic, showing ELS at G26 (red-yellow wire) (should I repost it here?). The sockets shown there are the same as at the schematics here.

Your solution is good but to my mind it's a little bit straightforward. It has the disadvantage that for solving some little problem we drop overall reliability. I will not ever reach the build quality that would allow a circuit board to survive in automotive application in our climate for several years.

A little example: you are about to overtake some truck, the road you drive have 1 lane per each direction, and there's a car driving on the other lane. Now if say my DIY speedometer breaks then nothing bad happens, then imagine for a moment what happens if TPS stops showing full throttle for some reason. So in such applications I'm after factory-made solutions. I think I'll play a bit more with air bypass valves for now.

[wilbo666]

The ELS pin isn't listed in the schematic given in this topic, but here at Toymods a topic exists where plenty of schematics is listed. Among others there's a fully translated 2JZ-GTE schematic, showing ELS at G26 (red-yellow wire) (should I repost it here?). The sockets shown there are the same as at the schematics here.

JZA80 VVTi engine ECUs have the ELS pin.

However on the JZS161 engine ECUs the pin that is ELS on the JZA80 VVTi engine ECU ("G26") is the Park Gear-ECT Position Indicator. Which would explain while the idle drops when you connect it to +12V

Your solution is good but to my mind it's a little bit straightforward. It has the disadvantage that for solving some little problem we drop overall reliability. I will not ever reach the build quality that would allow a circuit board to survive in automotive application in our climate for several years.

A few ways to improve the reliability that I can think of
-Mount the Circuit board inside the car, in a box
-Conformal coat the PCB
-Pot the PCB
-Choose components that are rated for automotive use and have -40->+80DegC temperature range

A little example: you are about to overtake some truck, the road you drive have 1 lane per each direction, and there's a car driving on the other lane. Now if say my DIY speedometer breaks then nothing bad happens, then imagine for a moment what happens if TPS stops showing full throttle for some reason. So in such applications I'm after factory-made solutions. I think I'll play a bit more with air bypass valves for now.

I'd imagine it'd be a very similar situation as if the mechanical throttle cable / linkage broke or jammed at the moment...

Currently in the factory arrangement if the TPS loses power (Broken / shorted wire) you'd also loose 90% of your throttle... there is a small mechanical backup, but it is not much.

I do understand what you are saying, but I feel that with good design most of your risks can be mitigated. For example the below circuit shows more of what I would do if I was implementing the design - The above schematic was just a quick drawing to give you an indication of the concept

I'm sure there are still more ways to improve the below circuit also.



Cheers
Wilbo

[George]

However on the JZS161 engine ECUs the pin that is ELS on the JZA80 VVTi engine ECU ("G26") is the Park Gear-ECT Position Indicator. Which would explain while the idle drops when you connect it to +12V

FUNNY INDEED =) I knew that there would be some other pin so I've first checked it to be pulled up to 12v (or down to gnd), then tried activating with 100mA fuse and a milliampermeter. Which shown about 12mA so it really was an input. I however couldn't imagine it to be ANOTHER input :-)

Here's an example of a bit smarter solution. We could actually run some circuit in parallel to the TPS output. And have a Shottky diode in series with the circuit output. Then if TPS shows more percentage than our circuit does, the circuit is just ignored. And for sensing we can use closed throttle sensor. In the case we don't need a controller. But the design is still a bit lame )

Unfortunately for the topic, we are now more concerned of turbo refarbing, and the problem of the AC has shifted to some background.

p/s here's a brief sketch of what I'm thinking of
http://sites.google.com/site/yurybar..._on_rev_up.jpg
When the A/C is ON, then voltage at the TPS input of the ECU will never drop below ~0.7V.

[triptek]

I thought i'd add an update on this. I'v just got my cressida back from the exhaust shop and i decided to test my aircon. It was still gassed up from my 2jzge conversion. The ecu seems to compensate for most of the drop in rpm when i turn the ac on. The rpm will drop down for a split second then it will come back up just below normal idle speed.

[George]

ours doesn't , but thanks anyway...