New Ohio user with a P3 set

Hello forum, new guy here who just bought is first P3 set. I’ve ordered the bracket/manifold kit from realtrainhorns and will be selling the original manifold that the horns came with.

I’m going to be installing the setup on a 2010 Lexus GS350, and will be needing some tips here and there. Here’s my current parts list:

Nathan P3
RTL bracket kit
Puma air compressor
Parker 271-8 1/2" air brake hose
HB 1/2" solenoid for normal usage (idiot prevention)
Graham White 383-103 for demonstrations
HB 1/4" solenoid for remote tank purge
HB 4 gallon pancake tank to go in my spare tire hole
HB 90-120 PSI electric pressure switch
Load Genie check valve

To support extended compressor run times with the car off, I’m also wiring a dual battery kit with the following components:

Sears Die Hard Platinum 34/78 (rebadged Odyssey PC1500)
2 lengths of 2/0 SGX cable from front battery to rear
2x Blue Sea ANL fuse holders (one for each end)
250 amp fuses for each end
Merlin SmartBank Advanced dual battery solenoid and monitoring system
Steel battery bracket for rear battery
125 amp side terminal fuse for accessory distribution block
Blue Sea 6 port fuse block

Phew! Now I need to figure out how to get 3 large diameter “things” up to the front of the car - 2 battery cables and one air hose, each of which are about 3/4" diameter on the outside. Has anyone ever routed stuff on the outside of a car like mine? Anyone with a similar vehicle that can share their experience?

P.S. You might notice that the pneumatic portion of my setup is somewhat incomplete - that’s because I’m an electrical kind of guy. Anyways, recommendations for the right fittings for the hose I have would be much appreciated. Parker has hundreds of different styles and I have no idea what to get.

Hi and welcome to the forum. I run a dual battery system for air myself and can vouch for the effectiveness of that kind of setup. I ran cabling and air lines underneath the car following the fuel and brake lines but every vehicle is different I suppose. The P series have such a lovely sound, so I’m looking forward to seeing some pics and vid.

It’s probably going to be a few months before I can get everything all installed and working, but I’d like to get all the right parts now so I’m ready. I’m going to need to find someone with a lift and knowledge about my car, as well as the ability to fabricate some stuff since I can’t.

How long do you guys think I can run the Puma compressor in my trunk without ventilation? Anyone used one of these things before? Even with the pancake tank in the spare tire hole, the ports are going to stick out the top so I will need to build a box or something to protect the fittings from damage.

Welcome to the forum.

Thanks Dan! I’m in the process of buying some NPT tank plugs to fill some of these holes that I won’t use, and a few other miscellaneous fittings. I have a Load Genie coming so I can ditch the huge factory pressure switch and unloader valve combo and replace it with the more compact HB pressure switch.

Load genies are extremely torque sensitive so be careful when installing - 10 ft/lb max at both ends so pay close attention to its instructions.

I’m not sure how much 10 ft/lb is, but I’ll be very careful when installing it.

I just got my kit from RTH that will allow me to break each horn out onto its own bracket. This is going to be great!

Anyone have any experience with how much heat the Puma air compressors put out? I don’t want to melt my trunk if I let it run for too long!

Holy Cow!!!:eek::eek::eek::eek:what a setup!!!

Oh yea, welcome!!! Lol

I’ve started my install! Some pics to follow…

Starting with the second battery, installed in the left rear quarter panel on top of where the muffler is, and wired to the fuse holder that will be part of the dual battery wiring:

I had an Amish guy build me a wood platform to mount everything to. Once I get everything mounted, wired, working, etc, I will paint or carpet the wood. I might even build a box to enclose everything, but I would have to consider ventilation too:

I mounted the compressor head after removing it from the tank it was attached to, using the rubber feet from the bottom of the old tank for vibration protection. Also connected the leader hose to my 4 gallon pancake tank via the Load Genie check valve, and mounted the tank to the board as well:

Here’s a video of the setup running with no load for 5 minutes to break it in before closing off the tank and airing up:

Next, I mounted the dual battery relay and a fuse block for accessories, as well as the solenoid for the air compressor:


Going to a shop next week to use their lift in order to run my dual battery wiring and air hoses, as well as mounting the horns up front. Hopefully this will be done pretty soon.

Looks like the start of a really nice install.

Is that the stock leader hose? The compressor head will get HOT and the leader hoses are normally some kind of braided stainless or PTFE line hose.

Yup, that’s the stock copper hose with steel fins - I found that the necessary fitting was a 37 degree -8 flare, and it works perfectly.

Ahhh, after looking closer, I see that now.
It kind of looked like corrugated plastic tubing.

Looks good so far!

If you haven’t bought the power cable, let me suggest welding cable instead. These are made for lots of power and it’ll help with moving the load and won’t get hot while doing it.

Also, what are you doing for the alternator? Are you adding a second, or swapping to a higher output unit?


Hello Kris, thanks!
I’ve already bought my wire - it’s 2/0 SGX which is a high temperature automotive wire that is specifically designed for use in the engine bay. It has high abrasion resistance, good low temperature performance, and is rated for 125 degrees Celsius.
My stock alternator is 130 amps which should keep me going for a little while, but once the car is paid off and the warranty is up I will be upgrading to something a bit bigger.

Nice install, so far so good, looking forward to some Hornage :smiley:

Unfortunately, the P3s don’t fit. :frowning: I was at a friends body shop this weekend to see what we could make happen, but there was no way in hell that we could fit them in. My car has every single square inch taken up by something. I might have to use Shockers, but that sucks since I bought the P3s based on their awesome sound.

Great!! Another Lexus with horn. Lexus rules!! I am a noob tambien…

What year and model do you have? Seems like most of the newer cars don’t have much space at all.

Welcome to the forum NathanH5

I had a Lexus GS300, nice car, but no real Horn space! So it had to go!:frowning: