So I’m trying to work towards my first turbo build on my 1999 NB and I’m having trouble finding where exactly to get the wires and vacuum line through the firewall for the gauges. I’m trying to avoid cutting new holes if I can.

I’ve looked on the forums but most posts are nonspecific about which car (NA/NB) they’re working on, and I couldn’t find any good pictures or descriptions of where specifically to do this on an NB. I even tried watching YouTube videos of people showing off their builds for a chance glimpse of how they got through the firewall.

Do any of you NB owners have a good picture and description of where you went through the firewall?

 

Follow the OEM wires to a factory grommet.

Either pry the grommet open a bit to fit the extra wire in there, or cut a fresh one.

For MAP hose, there should be a few blanking grommets, just remove one of these and replace it with one with a hole and feed the map hose through.

Both methods of course you'll need to reach around and find the other end of the wire from inside the car and pull it through.



on my NB I just fed the MAP hose in through one of the blank grommets near the washer bottle.
Easy to reach, and also means the hose comes out right behind the glovebox, just above where the ECU is. (RHD)

 

Okay I’ll try going through the passenger side. If it works well I’ll post pics/YouTube video for future noobs like me.

 

next to the clutch master, there is a big ribber grommet where the factory wires go through.
make a new hole in the side of that large rubber grommet and push the vacuum hose though.
it will exit near your clutch pedal.

you can see this large grommet to the right of the clutch cylinder in the pic below

 

Make note he mentioned going that way because of RHD. For any U.S spec (LHD) the ECU is on the left driver side.

I ran my on the opposite side (left) side of the brake master. Removed one of the rubber plug/grommets and wrapped my cabling in some high temp, abrasive resistant sleeving I picked up from McMaster-Carr. This routes to a hole right above the gas & brake pedal.

 

Yep, just to make 100% clear.
Mine was for Right hand drive.

But some of the confusion is my fault, since while I knew the LHD/US cars had the ECU behind the dash, I always thought it was behind the passenger side of it (so, right hand side for US)

Didnt realise the US ones had the ECU on the left as well (must be tight in there with steering and ignition wiring there too?)



(for reference, RHD NA/NB have the ECU on the left hand (passenger side) footwell, behind a metal plate that doubles as a footrest and ECU cover, my mistake in that I assumed the ECU position to jsut be mirrored on LHD)

 

Fun fact, LHD EU-spec NB/NB2s have the ECU on the passenger footwell too.

 

LHD USDM NA6s have the ECU in the footwell. LHD USDM NA8s have them behind the passenger seat on the wall back there.

Yes, USDM NBs (not sure of 1 and 2?) Have them shoved up next to the steering columb and it sucks massivly.

 

I should also clarify. OP mentioned 99 NB so I just went off that notion. My understanding is that any of the US spec NA's have their ECU in the passenger footwell behind the metal plate and I believe all of the NBs have theirs under the dash next to the steering column and it sure is a dang tight fit.

 

I have come to the conclusion that Mazda's R&D department must have just had a big diagram of the car printed up.

And when it came to the LHD design they said "ok Jim, your turn to pick where the ECU gets mounted on this model. here's your blindfold, and a dart, start throwing!"

"great throw Jim, behind the seat for some reason, PERFECT!"

 

My car is a 1999 NB and I live in the US. My ECU is mounted kinda above and in-between the clutch and brake pedals on my LHD car.
I used that cone shaped rubber grommet to get all my cables and vacuum lines through. Diyautotune has good pictures in their 99-00 MSPNP2 installation guide of all the info I needed to install these guages (and immediately following, my ECU). Here's the link: MegaSquirtPNP by DIYAutoTune.com
Also, idk how I didn't see that grommet before. I must be blind and retarded.