Hi, 20v st (bt electronic)

Andrey AE86
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Joined: Thu Mar 30, 2017 12:34 pm

Hi, 20v st (bt electronic)

Postby Andrey AE86 » Wed May 10, 2017 7:23 am

Hi my friends, i have an ae86 with 20v silver top (black top ecu and all bt electric parts) but i dont know if vvt is working. Can any person help me?
I dont know if is necesary the speed sensor to run vvt.
I check the vvt sensor and its ok, the wire signal and positive are ok too.
I hope any can help, and very sorry, i dont speak english very well jejejejeje, saludos desde Costa Rica ✌️

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s24a
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Re: Hi, 20v st (bt electronic)

Postby s24a » Wed May 10, 2017 12:08 pm

To quickly see if the solenoid is working, you can connect 12V to one terminal and ground the other while at idle.
If the engine changes rpm and maybe also roughness, then the solenoid at least is working.

As for the ECU, you need to take the cover off and look to see if the transistor in the center of the board (most likely branded NEC) is not blown.
If that is good, then your VVT most likely is functioning.
"When the going gets, wierd, the Wierd turn Pro" -- Hunter S. Thompson

Andrey AE86
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Re: Hi, 20v st (bt electronic)

Postby Andrey AE86 » Thu May 11, 2017 10:21 am

s24a wrote:To quickly see if the solenoid is working, you can connect 12V to one terminal and ground the other while at idle.
If the engine changes rpm and maybe also roughness, then the solenoid at least is working.

As for the ECU, you need to take the cover off and look to see if the transistor in the center of the board (most likely branded NEC) is not blown.
If that is good, then your VVT most likely is functioning.


Thanks my friend, I conectado 12v to the solenoid and its working,. Im going to check the transistor in the ecu.
I dont need the speed sensor signal from the cluster? The vvt work whitout that signal?

Andrey AE86
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Re: Hi, 20v st (bt electronic)

Postby Andrey AE86 » Thu May 11, 2017 10:23 am

Also my car is not a GTS, Its a SR5

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s24a
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Re: Hi, 20v st (bt electronic)

Postby s24a » Thu May 11, 2017 12:51 pm

The VVT should function without a speed sensor. The parameters for operation seem to be speed (RPM) and load (MAP sensor voltage and TPS position).
There is modification to operation points based on engine coolant temperature as well.
"When the going gets, wierd, the Wierd turn Pro" -- Hunter S. Thompson

taroroot
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Re: Hi, 20v st (bt electronic)

Postby taroroot » Thu May 11, 2017 9:08 pm

Open that ECU and look inside, ASAP. I don't know about BT, but ST ECU has very high probability of bad/leaky capacitors. 2 out of 2 for me. It causes all kinds of weird behavior, but if you catch it before it damages the board, it's like a $5 fix for someone who can do pretty basic desolder and soldering.
And yeah, I've read about the BT VVT transistor going bad too. ST seems to not be a problem.

jdm86gtz
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Re: Hi, 20v st (bt electronic)

Postby jdm86gtz » Fri May 12, 2017 5:36 am

If you have a timing light you can mark the intake pulley on the belt side and the cam side and even free revving you will see the pulley move when you shine the timing light at the pulley (timing light pickup on no.1 plug lead)
The blacktop VVT works early in the revs whereas the silvertop VVT is either off below ~4400(ish) and on above ~4400rpm(ish)

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s24a
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Re: Hi, 20v st (bt electronic)

Postby s24a » Fri May 12, 2017 6:23 am

The Blacktop ECU is not as susceptible to capacitor failure as the Silvertop ECU is.

The Silvertop Nichicon caps are basically junk. The blacktop uses a mix, so it is still possible some can fail.

The Silvertop has a robust MOSFET VVT transistor, while the blacktop has a lower current transistor (smaller die). The Silvertop transistor is a MIL-spec part.
This is why the Blacktop transistor is prone to failure. And hard to find, IIRC.

I have repaired several Silvertop and Blacktop ECUs, and I cannot believe that you can buy good capacitors (like Panasonic) for $5.00 for a repair.
My repair "kit" parts are well over that price. With labor I charge $85.00 to change capacitors and heat sink the VVT transistor properly (more if track repair is needed). However, I think shipping and handling charges outside of the US or Canada will kill you. Depends on how bad it is and how bad you might want it.

Hank
"When the going gets, wierd, the Wierd turn Pro" -- Hunter S. Thompson

Andrey AE86
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Re: Hi, 20v st (bt electronic)

Postby Andrey AE86 » Wed May 17, 2017 11:31 am

Thanks my friends, this weekend I'm going to open the ecu and check the capacitors and transistor's, your answer Realy help me, thank you very much. This weekend I'm gona write about how is the ecu internals

taroroot
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Re: Hi, 20v st (bt electronic)

Postby taroroot » Tue May 23, 2017 9:27 pm

OK, I might have been exaggerating with $5, I'd have to go look at my Digikey order, but it wasn't very expensive.
Labor and skill is where the cost is. For someone whos done a fair amount of basic electronics hobby work, it should be pretty easy, the ECU circuit board traces are pretty big. Modern electronics with lots of micro surface mount stuff takes much more experience, skill and equipment to do successfully, but not the case here. Anyway, check those caps!

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