kokamo

Ok. I'm installing a heated oxygen sensor in my nova I am putting a TPI into. Now I'm down to the fuse box part and I was wondering what amperage fuse should I use for it.

THANKS FOR THE HELP!!!!

Joe

Vader

Three-wire or four-wire HO2S?

The GM factory wiring for cars that used HO2S fused them at 20A and usuaaly shared the load with the digital (stepper motor) EGR valve, EGR solenoid, and EVAP purge. I'm guessing that 10A would be fine, and either way, it would be better to start with a low fuse, measure the current, and fuse the circuit at about 125%.

anondude13

Installed my 3 wire yesterday, 3 amp fuse and it works as intended.

kokamo

3 amp it is.....oh yeah, it is a 3 wire o2s, part number asf-74

THANKS FOR THE HELP!!!!!!!

Jade Grey

iTrader: (1)

r3pp3r, where did you run your third wire lead? I know it has to be hot only with ignition on.

kokamo, I did not know that you should run it all the way back to the fuse box. I had heard it was easier to pickup a lead from a underhood relay or something.

I'm interested in this mod even though I'm only going to shorties.

anondude13

Through the firewall grommet to the fusebox. It is linked to the wiper motor source. Any ignition switched 12 V will work, I hear there is a nice one for emissions stuff in the engine bay, but I didn't find it.

kokamo

Jade Grey.....Remember, I Am doing a swap into a chevy nova. The fuse box is very limited to sources of power, so I made my own fuse box. Yes, MY OWN FUSE BOX. I built it specifically for this car, and I mounted it right below the computer that is where the glove box is supposed to be. Therefore it really wont be very far away from the oxygen sensor.....about two feet or so...just guessing. Anyway, I dont think you have to run the hot wire to the 02s all the way back to the fuse box, but I guess it wouldent hurt anything. I think r3pp3r is right. You could prolly run it anywhere you wanted. I put it on a 1 amp fuse last night and let it get pretty dang hot in my hands and it never blew the fuse. I just don't know if it will have the same draw when it is in the car under normal load. I think this is where trial and error come into play!!!! I'm gonna stick with the 3 amp for now and see how it goes from there.


Later!!!

Joe

Jade Grey

iTrader: (1)

kokamo, yes I understand that you are doing a swap into a Nova. Sorry, I was thinking about a 3rd gen application when I posed the question.

I would still like to know who has connected the lead to a source underhood though. Maybe I should just start a different thread about that.

kokamo

Jade...no prob man, I understand now. It's all good. Maybe you could turn on the ignition and get under the hood with a test light and probe around to see whats hot and whats not. Start with the basics. Oh maybe you can get power from the altenator. I think it's on the right side.....right???? Dunno for sure. how bout the ignition coil, it has power all the time the engine is running. OR you may try to start another thread and see what you may get...... good luck for your hot wire!!!!!!

Joe

P.S. If you have to cut the oxygen sensor lead to run to the computer rather than use the weather pack, you might not want to use your good set of wire cutters. For some odd reason, they make that wire out of some super duper bad a$$ kinda steel. I had nine kinds of hell tryin' to cut through it so I busted out the torch and got it done. I ruined my good pair of cutters by figuring this out. Just a note to let you know about this rediculous wire.

onebinky

iTrader: (1)

It's a special stainless steel resistance wire. Some people recommend not cutting it for fear of changing the accuracy of the sensor. Some have done it and not had issues, some have done it to find a completely dead sensor.

Do you have any pics of the fuse box? I was thinking this morning about doing something ssimilar, and am looking for ideas.

kokamo

onebinky....Yes I do have pics of the fuse box I built. I will post them prolly on sunday cause i'm at work now and won't have a chance to do so until sunday. Please don't laugh at it because it is made out of some leftover junk parts from my work. (i work at a rentals stor that rents out small equipment) The fuse box is constructed from a plastic air cleaner housing from a briggs and stratton engine. I'll explain later.

Until then, see ya!

Joe

onebinky

iTrader: (1)

Hey, if it works it works

I'll be waiting for those pics

kokamo

Ok... here it is. I drilled all the holes according to the width of the fuse, then I put the wire thru the hole and crimped on the female spade connector. After that, I shoved the connector in the hole which was pretty dang tight for the size of hole I drilled and put some good ole two part epoxy on both sides of it. The next day it was solid as a rock. From there, I took some of the medium sized heat shrink tubing and cut it to length to cover up the spade. Personally, I think it's a work of art. But hey....like you said, if it works it works. IT will work, and it's FREE!!!! I have it in the car at the moment and I tested it last night. Please pay no attention to the amps on what it is going to. The pic is what I just put in there to make it look purty for the pix. Remember if you want to use an air cleaner lid off of a briggs and stratton motor.....you might want to find one made of plastic. I started building one made out of steel, when I got half way thru drilling the holes it all dawned on me that it might not work. So I decided not to make an insurance claim on a buned up car and found a plastic one!!! I will look around for another if you would like.

By the way....the last pic is the fresh TPI setup in my 73 Nova. It is on a 11.5 to 1 compression 283 small block with a big ole lumpy cam. Again, that pic is kinda a rough draft.

LET ME KNOW WHAT YOU THINK!!!!

Joe

kokamo

another.....

kokamo

last one of the 283....

onebinky

iTrader: (1)

Very nicely done, that's definately something to be proud of. I'll bet that if you smooth that panel and lay some nice flat or matte black on it, it would look OEM.

Is that powder coat on the manifold? Looks very glossy. Well done

anondude13

Looks nice. Very clean job.

kokamo

HEY THANKS FOR THE COMMENT. I only did this to save a few bucks. I guess it will make me a little more proud of it in the end if you know what I mean.
Yeah, I thought about painting it. It would prolly make the dark spots where the epoxy is go away. I never did paint it and it is already under the dash. No big deal, I can still prolly hit it with a can of flat black and call it done. The only thing I don't like is the way there is nothing to separate the fuses, you know like the OEM ones? I kinda wish I had spaced em out just a little bit farther apart so I could get a peice of plastic between em. OH WELL!!! already done and under the dash.....nobody harly ever looks there anyway.

onebinky....I wish that was powder coat! I am kinda on a budget with this entire thing so I got some dupli-color hi-temp engine enamel and put about 5 or 6 coats on it and then I wet sanded with 1500 grit and then 2000. After that, I busted out the turtle wax and you get what you see.(glossy) I think it looks pretty good myself.....I am proud of it now that you mention it. THANKS!

r3pp3r.....THANKS FOR THE COMMENT!! I was wanting the entire thing to look good and work good at the same time. I have spent sooooooooo much time trying to "learn" how a TPI system works, the wireing system, and doing lots of mockup. Notice the fuel line routing. I had the fuel line come in on the original spot but modified that a little too. Then I rerouted the return line to the back of the manifold. Look at the left side of the rear of the manifold and you will see what I'm talking about.

Guys, you all have been alot of help. Now maybe I can get this thing running to morrow!!!!

I'll keep ya posted on that one!!!

Joe

P.S. Here is the Nova the TPI is going into.