Racefiend's CA Legal 1992 LS Swap Build Thread

[Broski]

I agree with ceylonfj40nut about the brass radiator !

Where will the battery now reside ?

Nice work and attention to detail !! thanks for sharing.

 

[Racefiend]

Pretty rough stuff on that radiator... What did they charge you to clean that thing up?

It was $190

 

[Racefiend]

Those brass radiators do not cool as well. I would switch to a TYC aluminum. Do it before shroud mods.

I'm going to stick with this one and see how it performs first. I'd prefer to have brass over plastic if it will get the job done.

I agree with ceylonfj40nut about the brass radiator !

Where will the battery now reside ?

Nice work and attention to detail !! thanks for sharing.

I'm going to make a tray to fit between the expansion tank and firewall. The pics are a bit deceiving. There is a ton of room there. I'll probably increase group size to the largest I can fit.

 

[ceylonfj40nut]

It gets to 226+C quickly. If you tow or climb passes it will be an issue.

 

[Racefiend]

It gets to 226+C quickly. If you tow or climb passes it will be an issue.

Out of curiosity, were you using electric fans?

 

[ceylonfj40nut]

Nope. Blue fan clutch. Aisin. Moved to TYC and 15k fluid in fan clutch. Works very well now. TYC cools better than OEM in my opinion. Even though they are plastic reservoirs they last 20 years.

 

[Racefiend]

Nope. Blue fan clutch. Aisin. Moved to TYC and 15k fluid in fan clutch. Works very well now. TYC cools better than OEM in my opinion. Even though they are plastic reservoirs they last 20 years.

Well I'll definitely go with the TYC if this one doesn't keep up. I'm hoping to have it running by the end of the month. We'll be hitting 100+ degrees a plenty during that time. Perfect for seeing what this rad will do with an HD clutch on the LS. It will give me a reason to melt more aluminum if I have to mod the shroud again.

 

[White Stripe]

I tried a couple gm fan clutches. They all seemed to lock up too much of the time. The only gm fan clutch that worked decent was the original that came with my motor. You can lose a lot of power if the fan stays locked up.

 

[Racefiend]

After a long hiatus, I am finally getting some progress done again. Unfortunately work, life, and medical stuff put this project on hold. Now that things are in order, and after some subtle (and not so subtle) comments from the GF, it’s time to get this thing finished up.

The next step in the process was to work on integrating the FJ systems into the LS computer. I started with the shift indicator. I won’t bore anyone with the details, as MarkN already figured this out several years ago. You can check his thread out here:

LS Swap– Gear Range Selector adapter - https://forum.ih8mud.com/threads/ls-swap-gear-range-selector-adapter.908575/

I made some modifications to his design and built this:

Next up was the tachometer. The solution is pretty simple. I got a Dakota Digital SGI100BT to convert the signal from the LS ECU to the tach.



Next up was the cruise control. The GM switch has a shared power, and each button sends 12v to it’s respective input on the LS ECU. The FJ switch is the opposite. It has a shared ground, and the cruise control computer sends 12v on each input to the switch. When each button is pressed, it’s respective input at the computer is grounded. The solution seemed simple. Swap the ground for 12v at the FJ switch, and wire the switch outputs to the LS ecu. Add a relay to turn on the cruise control light. Like so:

I found an issue with this solution. The GM switch ON/OFF button is a normal switch. The FJ Main button is a momentary switch. I would need to integrate some sort of latching relay to send a constant 12v from a momentary switch. I selected this module from Amazon:

Amazon product ASIN B095YFJ69T
It’s a combination of a flip flop and a latching relay. You give it a momentary input and it switches to Normally Open. Give it the signal again and it switches back to Normally Closed. You can choose a 12v signal or ground signal by switching the jumper. Cut the power to the relay module and it reverts back to Normally Closed. Perfect!

The other issue is that the FJ has a cancel button. The GM does not. While not a big deal if you know about it, I didn’t want someone using cruise control and hitting the cancel button, only to find the truck kept on going. That’s a safety issue in my mind. So I integrated another relay to implement a cancel function.

The other thing I didn’t like was having to cut and reroute the ground wire for the FJ switch to 12v. One of my main goals with this project is to make it completely plug and play. No cuts, no splices, no repining, no surprises. If anyone in the future wanted to convert this thing back to stock, or to electric, or to run off potatoes, I wanted to be able to unplug what I did and everything would be back to stock. This is the final solution I came up with:

When you hit the MAIN (on/off) button, it switches the latching relay which sends out 12v. That splits to the 3rd relay, which turns on the cruise control light, and passes through the 4th relay to the ON/OFF input of the ECU, telling it to turn on cruise control. Hit the button again, and it shuts everything off.

Hit the SET/COAST button, and that activates the 1st relay and sends 12v to the SET/COAST input on the ECU.

Hit the RESUME/ACCEL button, and that activates the 2nd relay and sends 12v to the RESUME/ACCEL input of the ECU.

Hit the CANCEL button, and that energizes the 4th relay, cutting 12v to the ECU for as long as the button is held. The ECU will see this as turning the on/off switch off and then back on, resetting the cruise control. On the dash, the cruise control light will stay on, and it will work just like the Toyota owner’s manual says it should.

Be aware that this will only work up to 92. In 93 Toyota switched to a different system with cruise control switch with one input with various resistors. If you have a 93+, you'll need to swap out the cruise switch for an older one. I believe they're pretty much all the same for various models.

 

[Racefiend]

After all that, I decided I didn’t want a bunch of black boxes hanging under the dash. A tach adapter, a shift indicator adapter, and a cruise control adapter. I would combine them all into one unit. But that would still leave me with 1 black box hanging under the dash. What to do. Then I had an idea. The original cruise control module would be useless now, so why not make it all fit in there. But I could not get everything to fit in there with a prototype board type setup. I would need a printed circuit board.

So I took a quick youtube crash course in circuit board design and usage of a free online design tool. I had to redesign my conversion harness that connects all of the LS stuff into the FJ to reroute a bunch of circuits to make it completely plug and play. I added a second header for the outputs. I had a place make it, and this was the result

I then soldered on all of the components. The 90-92 connector header for the cruise control computer is totally unavailable. I could find the 93+ but not the earlier connector. I had to desolder it from the original board and transfer it to the new board. The end result:

And then with everything installed

If I had to do it again, I would have picked different small headers (the small white ones). The pins for those headers were insanely small:

What are these, pins for ants? Luckily I ordered extra, because I fubar’d a couple trying to get the hang of crimping such tiny pins.

I cleaned up the cruise control box, put everything in, and gave it a name, a part number, and a new sticker.

 

[Racefiend]

Next up was tackling the fuel pump and sending unit. The LS ECU will need to have proper fuel level readings to run and pass the EVAP tests. The FJ fuel gauge sending unit works opposite of the GM unit. I thought I could convert it using an op amp circuit. I know nothing about op amps. I learned what I could, thought I had it, but when I plugged my circuit into a simulator, it did not do what I wanted. My head was beginning to hurt, so I tossed that idea and decided to run dual senders.

I started by cutting the plastic sender holder from the GM fuel pump.

I then made a bracket out of stainless steel to mount the GM fuel level sensor holder.

I cleaned up the sensor holder and mounted it to the bracket with some rivets

Then I installed the the sensor and modified the float rod to join into the FJ float rod. I made a little T tube the GM float rod inserts into. The T can move up and down the FJ rod as well as rotate in case I didn't get the alignment perfect

I hooked up one wire of the GM sensor to the hanger ground. There is secondary ground wire (the black wire) which is just a redundant ground. I disconnected that wire from the hanger and stole the connection for the GM float signal wire.

 

[Racefiend]

Next I needed to fit the fuel tank pressure sensor. I could have just teed the charcoal canister hose and ran a hose the sensor, but that's janky. I cut the sensor hole from the top of the GM fuel pump, and drilled a larger hole on top of the fuel pump hanger.

Then I welded the GM piece onto the hanger. Installed the grommet and sensor. Perfect fit.

Next was dealing with the fuel pump. The LS fuel pump flows 33 gph. I looked up the fuel pump specs for the 3FE and IIRC it was 22 gph. It would need to be replaced. I looked up the 1FZ and it was 31gph IIRC. The aftermarket replacement pumps for the 1FZ I found were 33gph. A perfect match. I had to order the 1FZ fuel pump cushion from Toyota as the 3FE cushion will not work with the 1FZ pump. I then cleaned all the rust off, painted it, and slapped on a new gasket. The final result:

That's it for now. Onto the next step!

 

[NeverFinis]

So I took a quick youtube crash course in circuit board design and usage of a free online design tool. I had to redesign my conversion harness that connects all of the LS stuff into the FJ to reroute a bunch of circuits to make it completely plug and play. I added a second header for the outputs. I had a place make it, and this was the result


View attachment 3310647

That is great! Self-taught PCB person here as well, and I was thinking of making a custom PCB when I got to that stage.

Suggestions for next time:
I am not sure the size of your traces but they might be small for relays. The trace width should be sized for the current load. You have the space for larger traces, and really no reason to keep them small.

Do a "ground pour" after all the power/signal traces are done, on top and bottom of the PCB. It fills the unused spaces with copper, which helps mitigate electrical interference to and from it. It also makes it every easy to run grounds.

 

[Racefiend]

That is great! Self-taught PCB person here as well, and I was thinking of making a custom PCB when I got to that stage.

Suggestions for next time:
I am not sure the size of your traces but they might be small for relays. The trace width should be sized for the current load. You have the space for larger traces, and really no reason to keep them small.

Do a "ground pour" after all the power/signal traces are done, on top and bottom of the PCB. It fills the unused spaces with copper, which helps mitigate electrical interference to and from it. It also makes it every easy to run grounds.

Thanks for the tips! There are definitely a few things I would have done differently if I had to do it again (who knows, maybe it will burn up and I will have to LOL)

I used .5mm traces for the power and ground busses. .254mm for all signals and bulb outputs. I figured that should be enough to run signals, 2 bulbs max, and the latching relay and tach adapter. I didn't go bigger because I was scared of getting too close to the solder pads and somehow fubaring the traces while soldering. Should I have gone wider? Here is the schematic of the board:

 

[kenavt]

As someone who does a lot of PCB design for a living...

That is great! Self-taught PCB person here as well, and I was thinking of making a custom PCB when I got to that stage.

Suggestions for next time:
I am not sure the size of your traces but they might be small for relays. The trace width should be sized for the current load. You have the space for larger traces, and really no reason to keep them small.

Do a "ground pour" after all the power/signal traces are done, on top and bottom of the PCB. It fills the unused spaces with copper, which helps mitigate electrical interference to and from it. It also makes it every easy to run grounds.

These are some great tips.

Thanks for the tips! There are definitely a few things I would have done differently if I had to do it again (who knows, maybe it will burn up and I will have to LOL)

I used .5mm traces for the power and ground busses. .254mm for all signals and bulb outputs. I figured that should be enough to run signals, 2 bulbs max, and the latching relay and tach adapter. I didn't go bigger because I was scared of getting too close to the solder pads and somehow fubaring the traces while soldering. Should I have gone wider? Here is the schematic of the board:

View attachment 3311222

You have plenty of room to run larger traces. The blue compound on your PCB is "soldermask", it is there to prevent you fubaring the traces or otherwise messing up the PCB when you're soldering (solder can't stick to it).


For sizing traces if you want to go into the details... you really want to play with a calculator like this: Printed Circuit Board Trace Width Tool | Advanced Circuits - https://www.4pcb.com/trace-width-calculator.html. I would assume you have a 2-layer board with "normal" (1oz/ft^2) copper thickness. At 0.5mm traces you can handle ~1.5 amps without too much temperature rise (external layers in air). You'd want to check how much current your bulbs and signals are drawing then, and size appropriately. That said, looking at your layout, you could easy run traces that are a few mm or cm wide no problem

My fun anecdote is that I once designed a PCB for an old Subaru's ignition circuit that turned out to have 10A running through 0.25mm traces... fried the trace and peeled it right off the board within 30s

 

[Racefiend]

As someone who does a lot of PCB design for a living...

These are some great tips.



You have plenty of room to run larger traces. The blue compound on your PCB is "soldermask", it is there to prevent you fubaring the traces or otherwise messing up the PCB when you're soldering (solder can't stick to it).


For sizing traces if you want to go into the details... you really want to play with a calculator like this: Printed Circuit Board Trace Width Tool | Advanced Circuits - https://www.4pcb.com/trace-width-calculator.html. I would assume you have a 2-layer board with "normal" (1oz/ft^2) copper thickness. At 0.5mm traces you can handle ~1.5 amps without too much temperature rise (external layers in air). You'd want to check how much current your bulbs and signals are drawing then, and size appropriately. That said, looking at your layout, you could easy run traces that are a few mm or cm wide no problem

My fun anecdote is that I once designed a PCB for an old Subaru's ignition circuit that turned out to have 10A running through 0.25mm traces... fried the trace and peeled it right off the board within 30s

The relay coils only pull 12.5mA and the bulbs are about .1A each. The latching relay states 5mA. I couldn't find specs on the tach adapter. I assumed I had enough overhead to drive the tach adapter and signals. I guess we'll find out. Hopefully I don't beat your 30 second benchmark LOL.

My fear was applying too much heat and melting the mask around the pad and having solder run into a trace. Is that a misplaced fear? If not, what's the minimum distance between a trace and pad assuming average skill?

 

[kenavt]

The relay coils only pull 12.5mA and the bulbs are about .1A each. The latching relay states 5mA. I couldn't find specs on the tach adapter. I assumed I had enough overhead to drive the tach adapter and signals. I guess we'll find out. Hopefully I don't beat your 30 second benchmark LOL.

My fear was applying too much heat and melting the mask around the pad and having solder run into a trace. Is that a misplaced fear? If not, what's the minimum distance between a trace and pad assuming average skill?

That's not much current... probably not worth getting too worried about then unless you have issues IMO

It is not easy to melt the soldermask enough that you can access a trace nearby, you'd really have to work at it (or have your iron be much hotter then needed). Even if you do manage to "bridge" a pad and trace, you can try to use some solder wick to pull the solder off and try again with a bit more care.

Common PCB fab shops can do 0.15mm spacing between a pad and trace; in my opinion that'll be just fine.

Also meant to say before - way to make a board, this is a really cool purpose to make one and I love that it fits in the CC module enclosure! Awesome!

 

[Racefiend]

That's not much current... probably not worth getting too worried about then unless you have issues IMO

It is not easy to melt the soldermask enough that you can access a trace nearby, you'd really have to work at it (or have your iron be much hotter then needed). Even if you do manage to "bridge" a pad and trace, you can try to use some solder wick to pull the solder off and try again with a bit more care.

Common PCB fab shops can do 0.15mm spacing between a pad and trace; in my opinion that'll be just fine.

Also meant to say before - way to make a board, this is a really cool purpose to make one and I love that it fits in the CC module enclosure! Awesome!

Thank you! It's good to get tips from a couple guys in the know.

 

[Albatross80]

This thread is bonkers. Great content and write up. Subscribed since I’ll be moving to the west soon. Elegant solution to the tank pressure sensor problem.

 

[Racefiend]

This thread is bonkers. Great content and write up. Subscribed since I’ll be moving to the west soon. Elegant solution to the tank pressure sensor problem.

I have dozens of wiring schematics and connector pinouts I made which I'll post up once this thing is running and I verify everything is working.

Here's the progress so far. Made my integration harness which plugs into the LS wiring on one end, and connects to the FJ at the other end on IH1 and IH2.

Next I need to mock it up, do some finishing taping, and loom it.