GM LFX 3.6L V6 Motor Swap

[gtpvette]

Originally Posted by ILLSMOQ

I like how 3.58 looks on paper compared to taller and shorter gears...I think if you switch to a gear numerically lower than the 3.58, your higher speed performance will suffer. I’m thinking if it were me, I’d leave the 4.10 in place until you’ve had a chance to drive it and then decide where the performance is lacking....also, instead of changing the diff maybe you look harder at switching to that other transmission if the ratios are an improvement.

You certainly have a point. Project scope creep at this point probably isn't a good idea if I want to get this on the road. I went out and looked at Cars-parts to see what was available as far as the CTS Transmission go. They're available at $1K give or take,, but the miles are higher.

Originally Posted by venturaII

If you could take gears 1, 2 and 3 from the FRS, and combine them with 4, 5 and 6 of the Camaro 'box, you'd be good with the stock 4.10s. Or you could make a less drastic change to 3.73, and have the V6 turning a little more relaxed speed...

EDIT: Of course, this is all in Imaginationland...lol

Originally Posted by AJPG

That could be done! It will be the frs gear box. The 4, 5 and 6 gears are almost identical on both.

I do believe both boxes are made by Aisian,, don't know about switching gears around LOL. Besides the FRS box is long gone.... The IS300 M85 (3.73) rear is still a possibility. Prices are a bit crazy for them though. That rear with the CTS Trans would work nicely I think.

[-Willis-86touge]

I wouldn’t waste your money on new gears the point of the swap is performance, the 4.10 looks optimal for this. Both engines redline nearly identical. Why change gears, just because the trans is a bit higher, let’s put it this way every one na puts a higher final drive to exact as much power as possible with in reason, the frs needs the push. Beside it’s the top end you worry about and with the 4.10 top end stays the same as factory. 167 is more than enough mph and that is with your calculations. I noticed you show a red line of 7000rpms? In reality its 7600rpms witch should give you near top end of 178 mph!!! More than enough also this would keep cruising speeds identical to frs, so highway speeds identical too. I state again “why” when you’ll just end up wanting to put it back in

[gtpvette]

I haven’t updated in a while so here’s the latest. Still messing with wiring. Got the Current Performance (CP from here out) box wired to the chassis. Really it’s just a few wires at this point though.


I wired the EFI MAIN3 relay to the Ignition On relay in the CP box. This triggers relays and power for O2 sensors, Coils, PCM Ignition On, and the MAF, VSS etc. One note, the EFI MAIN3 relay seems to get ground to trigger the relay from the PCM. When I initially tested it, it wasn’t getting any ground and with that no power to anything. All I could think of is the ground wires in the PCM from the AC1 plug 34,35,36,37 and 40. I grounded all of them and the EFI MAIN3 had ground finally and powered up. Also fuel pump kicks on and spits out some gas when the key is on now. I’m going to go back and try to sift through these ground wires to figure out which are needed.


The single fan is wired, ground to trigger the CP Fan2 relay via the Camaro PCM or when the CP box triggers the AC Compressor relay it’ll turn on the fan automatically. This latter item is a really nice feature of the CP fuse/relay box.


Speaking of AC, I’m going to initially try to wire up the AC outside of the Camaro PCM as I don’t think Colin is quite there yet and I have to have it. I‘ll have a regular universal binary switch on a 10MM port on the high side right out of the compressor. I’ll wire this in with a toggle switch (2 wire) in the cabin to kick on the AC compressor via the CP box. Once Colin is ready, I can remove that binary switch and swap in the GM OEM high/low switch (three wire) on the 10MM port with no loss of refrigerant, and wire in the Compressor On from the Camaro PCM to the CP Relay. The only item here is I have to wire the harness for the two different switches and activation of the CP Relay which I’ve done. There may end up being some freezing on the evaporator if it gets too cold with just a manual switch, but I can deal with that short term. I’ve included pics of the modified lines coming out of the firewall as well as the block and fittings on the compressor. Hopefully all of this is going to work as no AC in the summer would be hell.


Thanks to ILLSMOQ as he got me pointed to the backup lamp wiring,,,, works good now!


Was looking at the ground wires for the motor and chassis as I don’t exactly remember what I took off when I pulled the FA20. Looks like the wire that attaches to the negative port on the battery goes to the motor as well as a smaller branch that bolts to the chassis right by the passenger shock tower. Sound right??? Were there any additional wires from the motor back to the chassis for a better ground?????? You guys do anything else??

Saw I guy who modified some harbor freight crimpers so he could put a bead on a heater pipe. Totally copied him,,, works great!

Also, been trying different fittings on the slave side for a remote bleeder. I ordered a couple of fittings out of the UK as I couldn’t find anything here 8mm x.125. The bleeder will need a crush washer but hopefully it’ll work. We’ll see.


Driveshaft will finally be here tomorrow!!!

[venturaII]

That heater pipe bead making trick is brilliant - I almost look forward to having to try it!

[gtpvette]

I thought I had ruined those crimpers when I cut them,, way too close but that aluminum is really soft.




OK,,, anyone know about this item and how it works??? I think it's a evaporator sensor switch which could be a really good thing.

[Ultramaroon]

Originally Posted by gtpvette

I thought I had ruined those crimpers when I cut them,, way too close but that aluminum is really soft.




OK,,, anyone know about this item and how it works??? I think it's a evaporator sensor switch which could be a really good thing.

That is the thermocouple which tells the controller to let go of the compressor before the evaporator ices over. It's why, on low, the compressor cycles on and off so often.

[gtpvette]

Originally Posted by Ultramaroon

That is the thermocouple which tells the controller to let go of the compressor before the evaporator ices over. It's why, on low, the compressor cycles on and off so often.

Yes,,, I think you're right. It looks like there are fixed thermostats that might be able to shut down the compressor when things get to an exact temp. It's more old school as everything newer talks to the PCM. Stay tuned.

[gtpvette]

Ordered one of these from Rockauto,,, on at 45 degrees, off at 30 degrees. The PITA will be getting the probe into the evaporator. This should keep things from freezing up. Ordered a small 16MM lighted latching switch from ebay to mount on the dash. All together about $30.


So it'll be Switch to Thermostat, Thermostat to Compressor relay, Compressor relay power to Binary switch, Binary switch to compressor.

[gtpvette]

One step forward,,,, two back.

Got the driveshaft installed. Nice piece and fits just right. Thanks DSS! CV joint slides in and out a bit to allow it to be installed. i was also concerned about clearance to the shifter but seems to be just fine.

Put motor back in to finish wiring engine harness to chassis. Well shade tree engineering got me again. When I initially decided where to put the Camaro PCM the alternator wasn't installed. With the alternator installed no room to install the plugs. OK so I need to move it. The problem is there is no room on that side of the motor. This is 10lbs of stuff in a 5lb bag.

There's a guy who's installing an LFX into a Miata. He found a different water pipe from a CTS that runs from the back of the motor down low then out below the alternator. This might give me enough room,,,, I hope. I'll order one today,,, in the mean time back to the exhaust.

[Sportsguy83]

Originally Posted by gtpvette

One step forward,,,, two back.

Got the driveshaft installed. Nice piece and fits just right. Thanks DSS! CV joint slides in and out a bit to allow it to be installed. i was also concerned about clearance to the shifter but seems to be just fine.

Hey Fred, I was wondering what HP is the DSS driveshaft rated for?

[gtpvette]

Originally Posted by Sportsguy83

Hey Fred, I was wondering what HP is the DSS driveshaft rated for?

Honestly never asked as this motor is only 325hp. It's a 3" steel shaft (said no aluminum was available), CV on one side regular u-joint on the other. Looks plenty strong though.

[gtpvette]

I've been working on the exhaust the last few weeks. I've got to say,,, this was harder than I expected. The original plan was 2.5" true dual,,, dual pipes to a resonated x-pipe muffler, then down and out the back with twin Spiral flow mufflers. The biggest issue was getting around the differential. Just not enough room. Ended up doing an additional x-pipe there,, it's about 3.75" wide so should flow pretty well. Everything is tight,, close to the driveshaft and to the gas tank as well.

I'm waiting on exhaust tips to finish from the spiral flows out the back. Tomorrow I need to put an additional set of v-band clamps in after the muffler, clean up some welds and paint.

If I were doing it again,, after the resonated x-pipe muffler I'd go to a y-pipe taking the dual 2.5" to a single 3",, then just run it out the back. It's be so much easier. The thing is I had bought all of the 2.5" material,, so just went with it. Live and learn.

[DustinS]

Now try it with 3” piping haha. Looks great! Excited to see how it sounds

[gtpvette]

Originally Posted by DustinS

Now try it with 3” piping haha. Looks great! Excited to see how it sounds

I feel for you doing it in 3",, just no frickin room. I'm still a bit concerned that it'll rub or bang around,, we'll see. That y-pipe and a single 3" might still be in my future.