New project - an old 1.8L engine swap

[Joel Sass]

Hey all. Just looking for some advice here since it's been a while, and I've lost some of the lore.

I bought a GTX with a 1.8L BPT engine swap midway through completion about 10 years ago. I finally have time to get to it, and intend to "do it right". "Do it right" includes stuff like a standalone ECU and coil-on-plug conversion. I am trying to remember how similar the BPT is to a Miata so I know what I should and should not purchase to get this project underway.

I'm pretty sure that Miatas never had a rotor, and operated on wasted spark, whereas this engine has a rotor and cap. Is the 1.8L cam angle sensor for a Miata a direct swap for this application?

Should I get a toothed wheel for the crank angle sensor?

Is it safe to assume that the 1.8L GTR engine is just a BP engine with a rotor, or are there any other physical differences that I should be aware of? If it's pretty much equivalent to a Miata, are normal standalone turbo ECUs an easy way to get this started?

Any hints, guides, or experience are appreciated. I am probably going to jump on the turbo Miata forums to get some ideas as well, but I figured I'd check in here for experiences before I start looking elsewhere.

Thanks!

-- Joel

[Sam]

I am running a standalone speeduino ECM on my 323 GTX with the 1.6 B6T. I have it set up using a Miata CAS and Toyota coil packs. I took the engine / transmission harness out, stripped it down to just the stuff for the transmission (I think just the 4wd actuator stuff) and built a new engine harness from scratch, which worked very nicely. I ditched the stock IAC entirely and am running an external IAC since the stock IAC is weird and draws way too much power for the speeduino and most other standalones.

The Miata CAS works great and the 1.6 and 1.8 CAS should both fit either the 1.6 or 1.8 engine. I am using the optical version of the CAS that I put a different higher resolution wheel in and I am using it as both the cam and crank signal to the ECM. I actually have some extra high res disks if you end up going that way and want one? 

[Joel Sass]

Well a higher resolution wheel sounds like a good first step. I'll shoot you a separate email in a second to set that up. Which version of the CAS does that fit? Or are they all the same? If there's a model year, let me know.

Out of curiosity, did you go with a wasted spark setup or sequential spark? Also, did you make any fuel modifications? What kind of initial map did you go with to get things started? How much boost are you running?

Since this is a 1.8L with a viscous LSD, I don't have to worry about much transmission wiring besides the backup lights. I'm interested to know more about the IAC valve you picked up. Also, I'm interested to know if you integrated knock sensing into your ECU.

--
You received this message because you are subscribed to the Google Groups "323gtx" group.
To unsubscribe from this group and stop receiving emails from it, send an email to 323gtx+un...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/323gtx/5d60f319-c338-4067-a20e-9e0e0b730162n%40googlegroups.com.

[Sam]

This is a picture of the wheels I had made. The outside ring is 24-1, and the inside ring is just that one large notch. For the speeduino you only need to wire up the outside ring part of the CAS to the ECM as a crank sensor and then in the base map set it to be a cam speed crank sensor. The extra one tooth inside ring is just in case I ever switch to a different ECM that needs it. The speeduino also has you set an ignition angle offset or whatever which is the difference between when the missing tooth passes over the sensor and the actual top dead center of cylinder 1. You can't really see when the missing notch passes under the sensor very well with the way the CAS works inside, so you just have to set a random guess value then dial it in with a timing light. Oh also the wheel only fits the optical version of the CAS. The optical version came on the 1.6 engine Miata from 1990-1993, and has a flat top. The disk I made is a tiny bit thicker than the original one so you have to sand down a spacer inside the CAS to make it fit. It's pretty easy and obvious what needs to be done when you have it open.

I am running full sequential spark and injection. I am using Fuel Injector Clinic 550cc injectors meant for a 1.6 Miata engine because the original ones in my 323 had a pretty bad spray pattern from lots of miles. The stock ones would work fine though if yours are in better shape than mine were. I removed the stock fuel pressure regulator and I am now running an external adjustable fuel pressure regulator. 

I actually just set up the base map myself, but its pretty easy on these cars because the engines are very simple. The hardest parts are getting that crank sensor settings set right, getting the crank sensor offset value I talked about earlier dialed in with the timing light, and getting the coil pack settings right. There is one setting for the coil packs that I think they call like "rising edge vs falling edge" that if you set it wrong it will melt the coils. Luckily the Toyota coils are pretty common for Miata owners to use with standalone ECMs so the settings are readily available online for that and dwell time and all that fun stuff.

This is the IAC I used. It's honestly really overpriced and I am pretty sure it was way cheaper when I bought mine, so maybe go another route on that. I have found out recently that my car idles fine using only the idle adjustment screw on the throttle and blocking off the IAC entirely, so you may not even need one if the 1.8 has that same idle adjustment screw on the throttle. My car also doesn't have air conditioning so if your's has it you may actually need an IAC more needed.

I am just running the same amount of boost as a stock 323 GTX at the moment. I don't have knock control and the speeduino doesn't support it unfortunately. I may end up switching to a Link G4X eventually because the speeduino isn't perfect and it's hard to find people who want to tune it.

[nowi...@yahoo.com]

Sam, it was interesting following along on Turbomiata.net….until you stopped providing details of your build.  Did you ditch the project?

 

https://www.miataturbo.net/build-threads-57/1988-mazda-323-gtx-restoration-modification-log-106635/

 

Lots of follow through threads and participation at miataturbo.net, which is quite interesting reading.

 

From: 323...@googlegroups.com <323...@googlegroups.com> On Behalf Of Sam
Sent: Tuesday, April 18, 2023 7:56 PM
To: 323gtx <323...@googlegroups.com>
Subject: Re: 323GTX Group Re: New project - an old 1.8L engine swap

 

To view this discussion on the web visit https://groups.google.com/d/msgid/323gtx/015ab4fb-efb2-4b0b-90a7-5476235f30d1n%40googlegroups.com.

[Sam]

I didn't ditch the project, just forgot to take pictures. I got it all together and working fairly well, and I drove it around to some cars hows and stuff last summer. I am doing some much needed suspension work right now and finally replacing the cracked exhaust manifold so I suppose this would be a good opportunity to post some updates on that thread.

Here it was last summer at cars and coffee next to a 1988 MR2.