Cheap Electronic FCD - Revised

ciper · Post by **ciper** » Mon Jan 12, 2004 11:38 pm

Another update.

We are going to use the TLO74 instead of a lm324. Higher quality and larger operating temperature -65 to +70 celcius!!! It costs alot more but it should be VERY rugged

Also we will remove the 5 volt line and use a regulator. This will reduce the number of ECU leads to 1 cut.

We will install a momentary switch that will connect the 5 volt line to the input line. This will activate the maximum output voltage and using a volt meter allow you to easily tune the cutoff.

The bypass switch (to allow normal operation) .

ciper · Post by **ciper** » Mon Jan 12, 2004 11:55 pm

Another feature that at the moment I cant mention. Lets just say its bells and whistles that will help seperate this from the rest. It will also make the passengers ask about the FCD and give free marketing.

boostjunkie · Post by **boostjunkie** » Tue Jan 13, 2004 12:01 am

ciper wrote:Also we will remove the 5 volt line and use a regulator. This will reduce the number of ECU leads to 1 cut.

I actually used a Radio Shack 5v voltage regulator to hook up a 12 input as a 5v source for my MAP sensor (the ecu 5v lead was fried). Measuring the 5v output to the TPS (the only other 5v source in the car) vs. the regulated 5v sourcethe voltages matched exactly!!

ciper · Post by **ciper** » Tue Jan 13, 2004 12:03 am

I know I dont have to convince you guys as much as the general public but Im trying to use the highest quality components possible. You wouldnt beleive how cheap (relatively) it is to do it. I could sell these at wholesale to different tuner shops and with markup still undercut the cost of any FCD available. Plus we will have equal or better features!

vrg3 · Post by **vrg3** » Tue Jan 13, 2004 12:56 am

ciper - I'm not sure which version of the TL074 you're talking about... -65 to +70 is a weird range. 70's also a little low for automotive applications. The TL074 comes in -40 to 85 and -55 to 125 versions, either of which is probably okay.

I guess it makes sense to not need the ECU's 5-volt rail to minimize the damage an incorrect installation can cause.

boostjunkie - You just got lucky. :) Also realize that they matched when you tested, but may not always match as the voltages vary with temperature and current.

J-MoNeY · Post by **J-MoNeY** » Fri Jan 16, 2004 4:50 am

ciper wrote:I know I dont have to convince you guys as much as the general public but Im trying to use the highest quality components possible. You wouldnt beleive how cheap (relatively) it is to do it. I could sell these at wholesale to different tuner shops and with markup still undercut the cost of any FCD available. Plus we will have equal or better features!

I would be VERY interested in buying one of these once you want to sell them. I'll PM you.

ciper · Post by **ciper** » Fri Jan 16, 2004 9:25 pm

I should receive a couple prototypes by the end of next week.

One modification is that we will probably use a 10 turn high precision pot to adjust the voltage. It will be from 2.5-5. It will take many turns to tune it but you will be able to adjust it in micro volts if needed

We will also include a two color LED. This is the cool part that will act as free advertisement of the chip.
There will be a switch on the FCD for normal or bypass operation. When in normal the LED will be one color (showing that its powered). Once you hit the mark where fuel cut would have occured the LED will change colors.

Meaning the LED will let you know every time you would have hit fuel cut. FCD are usually installed up and inside the vehicle, completely hidden away. If the activity light is installed in a viewable position it will let you know every time the device has done its job and prompt others to ask about it, thus creating more interest in the product.

Im going to use "highest quality" as the main sales pitch on these. Im even having a custom board built for them. Second will be ease of installation, only one ECU line will need to be cut otherwise just a ground and +12 is supplied.

evolutionmovement · Post by **evolutionmovement** » Sat Jan 17, 2004 1:14 am

I love the LED idea. Good thinking. How big is it? Could it fit behind where the little open pocket to the left of the steering wheel is? Out of curiosity, which board house did you use?

Steve

ciper · Post by **ciper** » Sat Jan 17, 2004 2:24 am

I had planned to have the LED external to the box so that you could mount it anywhere you like. Im not sure about the external size yet, we are still working on the mounting options and if to have the controls exposed or covered.

Ill have more details next week to share.

NemesisEJ22t · Post by **NemesisEJ22t** » Sun Jan 18, 2004 3:15 am

Here's another idea for the homemade FCD from the MR-2/Celica All-Trac crowd. We have had sucess from this for a few years now. I'm not sure exactly how well it will fit in with the Legacy's ECU, but it is very simple to install on a Toyota. It is variable as well, allowing you to raise/lower the fuel cut to whatever value you want. Here is the site: http://www.alltrac.net/mods/fuelcut.htm. You might want to take a look at it. If you have any questions about the 3S-GTE ECU, send me a PM, i know it well, and maybe if i talk to someone who knows the EJ22t ECU we can figure out how to adapt the FCD to the Subaru computer.

vrg3 · Post by **vrg3** » Sun Jan 18, 2004 3:40 am

The basic idea of the setup described on that page is to scale the pressure sensor signal down a bit. The main problem with doing that on an EJ22T is that the EJ22T ECU uses the same sensor to measure manifold pressure as atmospheric pressure. So, with one of these in place the ECU would misread barometric pressure and it would affect your air/fuel mixtures.

It also loads the pressure sensor, giving it a 25K load to ground, while simultaneously increasing the output impedance. While probably okay, it's generally better to avoid that.

One nice thing about ramping the voltages down, though, is that you get to keep a fuel cut which is a good safety feature.

ciper · Post by **ciper** » Sun Jan 18, 2004 7:54 pm

No offense but the design from the alltrac site is pretty crappy. Not only does it modify the signal from the sensor all across the range but it is barely adjustable. The more you try to reduce the voltage the more low end you are loosing until the point you might as well just inplug the sensor all together

vrg3 · Post by **vrg3** » Fri Jan 23, 2004 8:57 pm

I've just updated the web page with a revised design. I don't know why I didn't see this before, but you can reduce the effect of the op amps' input offset voltage by taking feedback for the first stages from the output of the circuit.

If you've already made the original design, it should be fine, but the new design is a slightly preferable. The parts are exactly the same; the hookup is just slightly different.

I'll probably be tossing a couple of these FCDs up in the parts shed again, since I assembled them just for pictures.

boostjunkie · Post by **boostjunkie** » Fri Jan 23, 2004 9:47 pm

Another vouch for this fcd's capability. Although I have the un-updated design, it's work on the stock fuel cut is flawless!! Thanks again!

ciper · Post by **ciper** » Sun Feb 15, 2004 2:46 am

Just as an update, Im on the third "revision" of the board. Had some prototypes made but on the last version miscommunication happened with the desired size. We ended up with a 3 inch by 5 inch board with a few components here and there

vrg3 · Post by **vrg3** » Sun Feb 15, 2004 4:31 am

If you can, ciper, I recommend taking the feedback for the input-stage op amps directly from the output as per my revised design.

legacy92ej22t · Post by **legacy92ej22t** » Sun Feb 15, 2004 7:12 am

boostjunkie wrote:Another vouch for this fcd's capability. Although I have the un-updated design, it's work on the stock fuel cut is flawless!! Thanks again!

Yes sir, I'm now running a Phase II vrg3 FCD myself and it works perfectly!

I couldn't be happier.

ciper · Post by **ciper** » Sun Feb 22, 2004 2:11 am

I just finished testing the latest version. Im very happy. Still a few small changes need to be made but Im about ready to start mass production.

They are VERY precise, to go from 3 volts to 3.27 volts is a complete turn! About 9 turns from 2.5 volts to 5 volts.

A two color LED connection will be supplied along with a bypass switch and a tuning jumper. When the curcuit is enabled and the pressure is below fuel cut the LED will be green. When the fuel cut pressure is reached the LED will turn orange. If the switch is in bypass mode the LED will be off and the curcuit will be completely isolated from the ECU and the car will act as normal. The tuning jumper will disconnect the input from the sensor and allow you to adjust the cut off point.

Some of the changes I mentioned are one cord exiting the unit, instead of individual wires. The size of the wires will be increased to the next gauge. External ground wires will be reduced to one.

Im going to package these for under dash installation, I see no benefit to putting them under the hood. You will only need to touch one wire on the ECU (pressure sensor), + and ground can tapped directly from the ecu or other power source active with ignition.

My only big problem is finding a suitable box. Everything I have seen so far is ugly. Any suggestions on a supplier?

mikec · Post by **mikec** » Sun Feb 22, 2004 6:39 am

If its intended for under dash installation, does the look of the box really matter? I'd probably grab one of these, and I'd definitely be more interested in function over form, especially if most of it's gonna be hidden under the dash.

Note: Don't mind the drunken guy posting when he should be sleeping.

evolutionmovement · Post by **evolutionmovement** » Sun Feb 22, 2004 6:57 am

Here's to the drunken posters! Screwdrivers with Goose here, baby! Convertingh two novels to screenplays is more fgun this way. Makes up fro all the content I need to gut.

Steve

mTk · Post by **mTk** » Sun Feb 22, 2004 11:22 am

evolutionmovement wrote:Here's to the drunken posters! Screwdrivers with Goose here, baby!Steve

Here yee!

MK

ciper · Post by **ciper** » Sun Feb 22, 2004 9:28 pm

I agree its not very important on how the box looks, but I want to be able to sell these to local speeds shops and through ebay. The boxes I saw where really bad, I would have been better off getting them through frys!

Would you guys care if the unit was 3 x 3 x 1? Or is that too big

mikec · Post by **mikec** » Sun Feb 22, 2004 10:05 pm

I must have missed the part where you wanted to sell them to the general public as well. Sorry dude!

Those dimensions don't seem to bad to me. There's easily that much space behind the dash.

evolutionmovement · Post by **evolutionmovement** » Sun Feb 22, 2004 10:27 pm

Generally, electronics enclosures are going to be cheap looking. All the ones we had at work looked like shit, both plastic and metal. The stuff in the catalogs looked no better. They don't seem to make them for style or even quality, but then again, we made low-end product...

Steve

vrg3 · Post by **vrg3** » Sun Feb 22, 2004 10:49 pm

Yeah, you should probably just look for a nice compact black-anodized aluminum housing and then have a label printed to fit over the entire top face.

You should drop these guys a line: http://enclosuresandcases.com/. They have some types of housings that look like they might work.

legacycentral bbs

A forum for 89-94 BC-BF(BJ) Legacy Owners and Fans

Cheap Electronic FCD - Revised