What operates the stock boost gauge?? - MR2 Owners Club Message Board
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post #1 of 26 (permalink) Old October 28th, 2015, 20:05 Thread Starter
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What operates the stock boost gauge??

Ok so before everyone tells me to put in an aftermarket gauge let me tell you that's not what I want. I have swapped in a 1mz V6 with a TRD S/C and I want to keep the rest of the car as stock as possible. If anyone got into my car that didn't know a lot about an MR2 they would think it was a factory stock car. That being said the last thing I need to do is get the stock boost gauge functioning with the TRD SC

So my question is what drives the stock gauge? When I got the car it was just a rolling shell with a lot missing. Is there a sensor in the engine bay that I'm missing or is it driven by the stock ecu? Anyone know how I can make it work mechanically or with an output from my standalone Haltech Sprint 500?

Anything helps as when I search everything says to get an aftermarket gauge....

Thanks in advance!
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post #2 of 26 (permalink) Old October 28th, 2015, 20:16
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Honestly, hopes and dreams.

Seriously, I know you don't want to hear it, but I never noticed the stock boost gauge having any relativity to the actual boost level.

For example, go full throttle at say, 2000rpm, the gauge would stay at full vacuum (should at least go to zero) until about 4k, when it would then jump to it's regular full boost level (stock CT26 will make full boost by ~3k or so).

Would you be willing to consider installing a 45mm aftermarket gauge in the stock cluster? Nobody that doesn't know the car will even notice it.


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post #3 of 26 (permalink) Old October 28th, 2015, 20:21 Thread Starter
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Exclamation

I have looked into that as an option but the car has some chrome trim rings around the gauges that look really nice that I would like to keep

The second issue is that I'm only pushing about 5 PSI so a 30 psi max boost gauge is a bit much.

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post #4 of 26 (permalink) Old October 28th, 2015, 20:32 Thread Starter
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It's currently just pegged at all times...

https://instagram.com/p/9LTHTxNM4o/
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post #5 of 26 (permalink) Old October 28th, 2015, 20:59
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Completely uninformed on the ACTUAL circuitry of the system but.... it operates on a voltage from the stock solenoid through the ECU. I know that sounds stupid, but you can pull the gauge off the cluster and see, it is purely voltage driven in the system.
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post #6 of 26 (permalink) Old October 28th, 2015, 21:18 Thread Starter
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With that being said I need to figure out how much voltage it gets to read vac and boost. I just found some info online showing the output voltage of a Gm map sensor in relation to pressure. Seems at 14.7 psi its putting out 4.9 volts. Maybe I can run the gm map sensor to drive the stock gauge...thinking out loud...
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post #7 of 26 (permalink) Old October 29th, 2015, 07:24
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I wouldn't bother getting any information from that gauge. It's pretty much useless. There are no numbers on the face of the gauge, so it's not meant to measure boost pressure in any accurate way and relaying that info to you as the driver. Just get an aftermarket gauge and install in in the stock location to keep the stock look.
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post #8 of 26 (permalink) Old October 29th, 2015, 08:29
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Quote:
Originally Posted by nopistons93 View Post
Completely uninformed on the ACTUAL circuitry of the system but.... it operates on a voltage from the stock solenoid through the ECU. I know that sounds stupid, but you can pull the gauge off the cluster and see, it is purely voltage driven in the system.
solenoid? surely the signal is from the MAP sensor (PIM in Toyota speak)?

If the needle movement is purely voltage based it should be relatively easy to make an op-amd based circuit with zero and gain adjustments to drive the gauge.

Assuming the US clusters are basically the same as JDM then there is a small circuit board inside the cluster that uses 4 screws for mounting and connecting to the flexible PCB, it is this circuit that you would be replacing.

Pretty sure the 4 connections are going to be:
Ground
Power (pretty sure it'll be 12v)
Signal in (from Map sensor?)
Signal out to guage.
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post #9 of 26 (permalink) Old October 29th, 2015, 08:36
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Quote:
Originally Posted by devonperlenfein View Post
I have looked into that as an option but the car has some chrome trim rings around the gauges that look really nice that I would like to keep

The second issue is that I'm only pushing about 5 PSI so a 30 psi max boost gauge is a bit much.
It depends on how you do the installation, but you can keep the gauge rings typically. The way I did mine was to take the gauge out of it's case and cut the case shorter / remove the face so that the aftermarket gauge sits flush with the face of the cluster. It really does look stock. But, never seeing more than 5psi on a 30psi gauge wouldn't be much fun

It's not a great picture of it (I wasn't trying to take a picture of the gauge), but this shows it some:


Quote:
Originally Posted by devonperlenfein View Post
With that being said I need to figure out how much voltage it gets to read vac and boost. I just found some info online showing the output voltage of a Gm map sensor in relation to pressure. Seems at 14.7 psi its putting out 4.9 volts. Maybe I can run the gm map sensor to drive the stock gauge...thinking out loud...
That might be possible. Test the gauge at various voltages to determine what the response is, then maybe build some sort of circuit or program an Arduino to do the conversion. A lot of work to keep the stock gauge, but it does seem possible.


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post #10 of 26 (permalink) Old October 29th, 2015, 13:08
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The Omori 45mm gauge sits below the cover, which is what Alex and soooo many others of us have. I'd done a write up on the installation, just go to the Turbo section and search Omori 45mm boost gauge and you should find it.

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post #11 of 26 (permalink) Old October 29th, 2015, 13:43
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What year is the car?


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post #12 of 26 (permalink) Old October 29th, 2015, 13:48 Thread Starter
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Originally Posted by Milo_101 View Post
I wouldn't bother getting any information from that gauge. It's pretty much useless. There are no numbers on the face of the gauge, so it's not meant to measure boost pressure in any accurate way and relaying that info to you as the driver. Just get an aftermarket gauge and install in in the stock location to keep the stock look.

As I mentiond I want to avoid an aftermarket gauge. It's a supercharged car. I don't really need to monitor the boost pressure I just want to gauge to function.


Thanks for the other ideas guys. I'm going to open up the cluster and see what I can make work.
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post #13 of 26 (permalink) Old October 29th, 2015, 13:49 Thread Starter
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It's a 1991
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post #14 of 26 (permalink) Old October 29th, 2015, 14:38
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I also just installed the gauge from TCS motorsports, can confirm it sits below the cover and you will not have to remove the bezel you have on your car if it is attached to the top portion of the cluster.
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post #15 of 26 (permalink) Old October 29th, 2015, 15:06
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I don't know how much of the stock harness you have retained from the swap but all you need is the turbo map sensor and the EA1 connector in the trunk.

The signal coming from the MAP sensor is what drives the stock gauge and that should be plugged into pin 11 of the EA1 connector (it will be a blue and black wire).



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post #16 of 26 (permalink) Old October 29th, 2015, 16:49
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The slow response of the stock gauge is due to the driver board that sits behind the rev counter.

I replaced the board with one of my own design using a simple AVR microcontroller. Now the gauge is super responsive and it's calibrated to the max boost pressure I run.



https://goo.gl/photos/b1hjfpeSyH12TqDCA
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post #17 of 26 (permalink) Old October 29th, 2015, 18:41
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very nice Jon!
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post #18 of 26 (permalink) Old October 29th, 2015, 21:04
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Quote:
Originally Posted by Jon View Post
The slow response of the stock gauge is due to the driver board that sits behind the rev counter.

I replaced the board with one of my own design using a simple AVR microcontroller. Now the gauge is super responsive and it's calibrated to the max boost pressure I run.



https://goo.gl/photos/b1hjfpeSyH12TqDCA
Woh, that's awesome work!!!


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post #19 of 26 (permalink) Old October 29th, 2015, 21:19
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Thats pretty cool Jon.

Is it doing a2d on the input and driving a simple pwm output?

If there is a spare output you could strobe some bright red/orange leds mounted in the back of the gauge for overboost warning.
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post #20 of 26 (permalink) Old October 29th, 2015, 21:48 Thread Starter
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Great info guys! I pulled the cluster again today. My current map sensor is built into the haltech. That being said I'll source an external map and run the signal from it. Thanks for the help!
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