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1991 VR4
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You have to change how you think a little bit when you tune an ARC2. You aren't tuning low, mid, and high RPM ranges like an SAFC. The low knob increases the entire spectrum numerically. That by nature effects the low load much more than high load. Pulling 20Hz from the idle makes a huge difference, pulling 20Hz from 3000Hz at higher load goes nearly unnoticed. The high knob adjusts the entire spectrum by percentage. That by nature effects the high load much more than low load. Pulling 10% from 3000Hz drops you to 2700,(very noticable) where 10% from 50 drops you to 45HZ. (not quite so noticable)

The mid knob controls the transition curve, and is typically a constant as it is what matches the linear output of a hotwire MAF to the not so linear output of a Karman Vortex sensor. It's almost always going to be -7 in that application regardless of tune or fuel used.
I dont even use a ARC2 (i run SAFC) and this is a very informative explanation of how the adjustments are actually "tuning".
 

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Discussion Starter #102
My mind is toasted. fought with this damn maft and im finally seeing good things. First the maf adaptor harness had a pin that wasnt seated and wouldnt so I cut that up and hardwired it, then the tach signal on the CAS wasnt good so I ran it to the ptu, doing that I forgot to tighten the clamp on to the throttle body and it blew off as I pulled on to a busy road. Im finally seeing good things though as cruising Im getting great AFR. After letting it run for 20-30 minutes my hot idle was 13.0 afr (WTF). I shut it off and started it back up and its 16-18+. So I dont get that. Also intake temp is at 125 degrees according to my lcdbc, the maft says it should be fixed at 80 degrees

Anyways its now time to datalog and I downloaded EVOSCAN and got a rs232 to usb cable and I cant get it to connect to EVOSCAN from the lcdbc. Wheres some help on this?

So great...Need input on why my air intake is 125 degrees instead of 80 like maft says it should be. Also need to figure out why I cant connect my lcdbc to evoscan. Soooo yea.
 

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Discussion Starter #103
I guess I have the wrong cable. The rs232 to usb isnt right?
 

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You have to make sure the RS232 to usb cable has the FTDI chipset built in if it’s going to be compatible. Also, your baud rate and a few other things are unique to the LCDBC and the settings you need for Evoscan are in the user manual on Antero’s website.
 

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Discussion Starter #107
Im curious if I could wire the maft up to the ls6 5 pin MAF's IAT sensor? Then it wouldnt be fixed at 80 if not 125. Theres definitely a wire for it but not sure it sends the right kind of signal. Im guessing that throws some stuff off though?
 

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Discussion Starter #108
Just found this in my basement. It won’t hook up to the lcdbc, but is it enough to datalog with using evoscan? Currently I’m looking at fuel trims vs airflow hz more than afr. I can monitor wideband afr when the other cable shows up and I can go through the lcdbc.
291528
 

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Discussion Starter #109
YES!!!!!! So I cut all the arc2 wires and ripped it out. FUCK THAT THING!!! Whatever is wrong with it has been the root of all my issues. My air intake temp is now 80 degrees, my idle isn’t all over the place, hopefully this is the start of a good relationship with my car! The maft is a bit confusing to me. I can tune base settings off sound and I end up tuning for what looks like aux9 base 2 510cc injectors instead of aux a base 2. But she’s running way better now that the computer sees 80 instead of 125 degrees for air intake.

fingers crossed that I’m finally heading in a good direction!!!
 

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Discussion Starter #110
hahaha I love it. Go to start the car this morning and it hates me. With the MAFT should it do a fast idle still? I think its dumping fuel in because its cold but its not revving up enough to use the fuel. possible FIAV sticking I guess. This morning it was 35 out.
 

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hahaha I love it. Go to start the car this morning and it hates me. With the MAFT should it do a fast idle still? I think its dumping fuel in because its cold but its not revving up enough to use the fuel. possible FIAV sticking I guess. This morning it was 35 out.
What RPM was it idling at on the cold start?
 

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Discussion Starter #112
What RPM was it idling at on the cold start?
Like 900. Pig F-in rich. Apparently I am just incompetent with this damn car. Tonight I am going to set the injectors to aux A base 2 and just run with it. if its rich on start up its just gonna get revved to 1800rpm. Those are the 660 numbers.

Stupid thing is really getting to me. Went and ran to the gas station and restarted it and go to drive out of the parking lot and its bucking and shit, then it drives fine 2 seconds later. Its very annoying because I cant start it and do a 1/4 mile pass. It runs like shit until its driven for a bit. hot, warm, cold, doesn't matter. Its had 2 ecu's in it. Maybe my supra fuel pump is shit, maybe my 660 denso injectors are shit.

The only good things that are happening is its atleast targeting 14.7 while I drive it. Thats new over the arc2.
 

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Discussion Starter #113
So for the hell of it I unhooked the battery to reset fuel trims. Set the maft to 660 size and started it. While cold it was reading lean off the wideband with narrow band 02's reading low voltage (.03) and not dithering. After a few minutes they started to dither and wideband afr read 15's. After 5 minutes of idle the wideband then started to read 13's with narrow band 02 sensors at .96 with no dithering. Fuel trim never changed for low mid or high active fuel trim never changed from 100 either.

So I Should dial out some fuel on the idle switch of the MAFT, that makes sense right? Should I turn on the cold enrichment for the MAFT dip switch #3? Who knows lol.
 

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Discussion Starter #114
Well, new plan. Stock injectors, fuel pump and maf are going back in the car. Will set boost controller to 10psi or so.
 

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Sounds to me like you got problems a Chromed ECU could solve, or better yet, a full stand-alone. ;)
 

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Well, new plan. Stock injectors, fuel pump and maf are going back in the car. Will set boost controller to 10psi or so.
You have an AFPR right? I was going to say to go back to stock MAF lol... I would say go back to stock MAF and stock injectors, but leave hotwired denso for now. You can use AFPR to adjust fuel to a certain extent, although you will still run into issues cranking up the boost (even if you have enough fuel) if you hit load limits in ECU (fuel cut). The car should at least drive and run well though, even if you can't make big power. Then you can decide where to go from there.
 

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Discussion Starter #117
Ok @jrhorne and @TurboSinceBirth and anyone else who’s throwing input to me.

This morning I started the car, much to my surprise it did a high cold idle. Super lean but hey it was doing it and running ok.

I’ve just found something out that is a game changer with this car. My issue currently has been a lean cold idle to a decent idle at a certain temp to a rich idle when hot. Just drove it 20 minutes and it was doing it again. 12.9 idle. Fuel trims for today averaged out at 128low 91 mid and 100 high. Active fuel trim is what’s been killing me at idle. It’s a rock solid 100. Doesn’t matter what temp the engine is or when it ran last.

So I get to where I’m going and I pull the ebrake and viola, my active fuel trim at idle starts pulling fuel like a motherfucker and targeting a high 16 idle!!! Within seconds the low fuel trim has gone from 128 to 81!! Release the parking brake and it goes to a solid 100 active trim again, put one brake and it starts trimming idle again.

WTF!?!? I generally park the car in neutral with parking brake off. So wtf is the parking brake sending to the computer to tell it to start trimming idle that the computer doesn’t see when I’m stopped at a light?!
my head is spinning right now as to what’s going on.
 

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Um, I'm not sure the ebrake on/off signal directly interacts with the ECU in any way, especially on MT cars? Just the dash light and maybe some communication to radio if you have aftermarket? If having the ebrake on/off truly changes the behavior and is repeatable, i would suspect a wiring/ground issue...

Hol' up, what? You leave your car in neutral with the e-brake off? So your car can just roll away?
Yeah also was wondering this lol?
 

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Doesn't really seem to interact with anything but the light on the gauge, then again I'm terrible at reading circuit diagrams.
 
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