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Since we have a forum again, I suppose it’s only fitting to christen it with the GTX build thread yet again (he says as Erich sighs under his breath “Just buy a C5 already…”) Luckily, we were able to save some of the posts from the old forum, so I’m going to try to start this off with recapping what was over there.
The 323 GTX was a homologation car made in the late 80’s so that Mazda could compete in the World Rally Championship. It featured 4wd, a turbocharged 4cyl powerplant making 130hp and a near equal amount of torque, locking center differential, and only weighed 2650lbs in stock form. Mazda planned on selling 2500 of these in the US per year, but with just over a thousand sold in ’88 and much fewer in ’89, it was quickly pulled off of the market. A lot of people claim the reason the car didn’t sell well was the price. At the time, it was nearly 2x the cost of a regular 323 at a base of $12,999 (most examples were ~15k with options.) 1243 examples were sold. The last solid number we have remaining is 690, though I believe that to be a bit high.
I bought mine after finding it on a Miata Facebook group. A gentleman had bought it from a friend and had decided to post about it. I quickly contacted him and said if he ever decided to sell, let me know. A week later, he contacted me. 3 days after that, I had a trailer, cash in hand, and a 2hr drive to Columbia SC.
The car had sat for a long time in a mechanics yard. Looking back on it, I think it’s easy to say that it was a few years or so since it had been on the road.
I took it home and immediately washed the dirt and grime off of it.
It looked way better than I thought it would. Paint didn’t have too much of a shine to it, and the bumpers were a bit faded, but it was all there.
A few days afterwords, I got the time to do an oil and filter change and try starting it. After a few cranks with the fuel injectors off to build oil pressure, I tried to start it and it fired immediately. The engine sounded great with none of the usual ticking you’d expect from a Mazda B6/BP engine. But, if you know about these cars, you know the engine wasn’t the main concern. I put it in reverse, and the car went backwards. Into first, and the car went forward. Second, car went forward faster. All good signs.
As I got more comfortable with the car, we did a few pulls up and down my driveway to umm…..dyno it. The car had some period 90’s mods on it, including an hks programmable fuel controller, boost controller, and a few other things that should, in theory, make this a near as makes no difference 200hp motor. The butt dyno gave a solid 160-180, not bad. However, when coming off of the throttle, white smoke kept appearing. Head gasket failure. I knew this couldn’t be this easy.
So out the engine came out and ended up at Daniels shop to be rebuilt.
(Picture links cause I’m too tired [lazy] to write this all again)
Engine Pull Album – http://imgur.com/a/qpi32
Engine Disassembly – http://imgur.com/a/ZxxcS
Engine Refinishing – http://imgur.com/a/HALKD
Sometime during this whole mess, I also did the Vacuum Lines because 80’s turbo car, and found time to detail the car and try to bring the paint back some.
In the meantime, I’ve amassed a huge amount of data relating to the GTX, including service manuals, original magazine reviews, common mods, everything that I can find.
So what’s happened since the old forum posts? Not a whole lot. The engine went back together, and everything seemed good, til we did a compression test. Long story short, intake valves are leaking/not seating and we’re not quite sure why. Probably going to have the valves lapped to try and get them to seat properly. Otherwise, I’ve found a cylinder head in a junkyard a couple hours away that’ll work.
I’ll try to end this on a brighter note. While all the problems with the valves were going on, I decided to get at least one project finished. The old valve cover looked like it had been to hell and back more than a few times.
So it got powdercoated back to more or less stock appearance by Bill at Kustom Kruisers. Huge thanks, this looks incredible and has got me back into this project once again.
That about does it. I’ll add more data as it happens. Thanks for reading!
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Been doing some seat of the pants math trying to calculate what the new compression ratio is going to be. Considering how much we’ve removed off of the head to bring it back to true, the concern is how much extra fuel (or higher octane fuel) I’ll have to dump in to keep it from detonating and pinging. Based this calculation off of a 15 thousandths cut on the head, along with some data and numbers pulled from Wiseco’s piston catalog. The change in combustion chamber volume (this is where the math gets speculative) was derived by considering the loss as a cylinder with a height of 15 thousands of an inch, and a radius one-half of the bore (I converted to imperial measurements for this step.) Using pi * r^2 * h, the volume of the imaginary cylinder was 0.11 cubic inches. Converting to metric, that’s a loss of 1.802557 cc’s (so much conversion, can’t we just use a real system of measurement?) Subtracting that from the original combustion chamber volume, which this online calc found to be 39.400 cc, left us 37.597 cc, or a 4.8% decrease.
Stock was around 7.8-7.9:1, depending on who you ask. Again, don’t trust these measurements because it’s entirely possible, bordering on a near-likelihood, that I did something wrong. Luckily, it doesn’t seem to have gone up a lot, so we should be in the clear!
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Thanks Art and Chris for the advice. Chris, those are the struts I was talking about. Apparently they’re the same size as my current ones, but since they’re built for a heavier hatch, I suppose they’re built to be much stronger, which would be nice. They’re also much more easier to get my hands on for what it’s worth.
Anyway, time for a sorta update on the GTX. The engine is done and is sitting over at Daniel’s shop waiting to be brought back to my garage. All it lacks are a few gaskets because I bought the wrong gasket set off of RockAuto. Got the set for a sohc Mazda b series instead of just buying the set for an 89-91 Miata. Anyway, those won’t be an issue to find and install myself.
In the meantime, a few things about this build have changed. A lot of thought has been given to reliability, and parts availability down the road. This started the other day while browsing the nearly 20 year old yahoo user group dedicated to the GTX.
Most people don’t know that archiving old websites and old user-generated information stored online is a big hobby of mine (see archiveteam.org for more info.) This started a long time ago, but got kicked into high gear when I got the GTX. You see, the GTX used to have its own forum with a dedicated user base and tons of information to boot. Unfortunately, the site was brought down by the creator and, as the story goes, even though people have tried to purchase the old backups of the site off of this created, he doesn’t want it back online because “it’s his.” Anyway, I didn’t want to see the data in this gem of a Yahoo user group go the same way (especially since Yahoo has a tendency to close down a service they host without notice. See:Geocities.) So I found a tool that allowed me to download the user group (and all 77k messages that have been sent on it) to a text file on my computer. A text file so massive that it crashes upon load if opened on anything except my 8 core desktop.
Anyway, coming back to the gtx, I started reading some of the old messages on the board, and the first one I read kicked off this new build idea. It was from the godfather of gtx tuning Mike Welch, where he was talking about the distributor on the gtx, not even 10 years old at the time.
This post from 1997 struck a chord with me. Am I still able to get these parts? Are they going to be like the radiator that has a 4 month lead time from Japan? (true story, btw) and is it going to be worth my time to go through this hassle of finding parts that are NLA, for a car that has no dedicated aftermarket? This goes beyond the distributor too. New turbos are impossible to find. To rebuild one, the only company I’ve found so far that’s willing to do it is in California, and they want nearly 600 for it (fair price all things considered.) And what about the ecu? The hks piggyback is impossible to tune, and the upgradable EPROM chips that went into them are also impossible to find. So long story short, the build is going in a new direction.
I’m going for reliability and a mild performance gain. I want to use parts that either replace something that’s NLA, will make the car safer to run and more reliably able to be enjoyed, will have replacement parts available for at least the next 10 years, and ultimately make the car as cool as it was in the 80’s. So, the plan is simple. I’m going to ditch the vj-14 journal bearing turbo and probably be going to a gt2554R ball bearing turbo. Garrett has been around for a long time and shows no signs of stopping, so replacements should always be available. This turbo is the smallest ball bearing turbo they make, and should spool much quicker than the old one, and it should provide a little more airflow for the car. I’m not looking for power here. I want to stay right around 225hp at the crank, which leaves me enough margin to keep the transmission happy, and is nearly a 100hp increase over stock.
For tuning, I’m planning a Megasquirt two with a coil on plug setup. Thankfully, to build one of these for the gtx is very simple because a kind gentleman has already written a full how-to for the turbo swap and MS install. See here: www.spitfireefi.com/files/GTX_MS_Install.pdf
So that’s where we stand. Overall, I think this is the best way to do right by the car and make it more simple and easy to work on as time goes on. Over the next month or two, I’m going to start collecting parts to accomplish this and begin working on this project again. Thanks to those that have kept up with the progress of this old car, and apologies for the long post. Needed to get my thoughts out.
See ya next time.
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So this found its way home today…
Took the chance to drain the secondary transmission fluid reservoir before I loaded it up. This reservoir is often forgotten and failure to change the fluid in it has been cited as one of the reasons these transmissions are prone to failure. Luckily, it was as fresh as the oil I removed from the main reservoir last year, with very minimal metal shavings on the drain plug (seriously, less than my civic had at its 80k service.)
Back at HQ…
Soon…
Anyway, what’s happening now? Now is the best chance I have to catalog the sensors that need replacing on the transmission and start it up. The transmission was in the corner of Daniels shop, so I never had the chance to do this previously. I also have a buddy coming over saturday to help me plan out everything needed for the megasquirt install, including sensors and what not. Once that’s figured out and ordered, it’s time to get the new turbo and get a new manifold made or an adapter plate fabricated.
Finally going somewhere on this, can’t wait!
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Started cleaning up the transmission today. It’s going to take multiple passes to get it as good as the block, but I’m fine spending a little bit of time on it. But, that wasn’t the interesting portion of today. Let’s zoom in.
Enhance!
Orange RTV (or equivalent sealing agent.) This transmission has been apart before.
Taking off the cover that goes over the 5th gear cog reveals some interesting things. This car is supposed to have about 136k miles on it. This is too clean, too new for 136k. Thinking it’s been rebuilt, which would be an awesome bonus attached to this car. I can’t be 100% sure though without cracking the transmission case, and it’s not worth doing that. But, just seeing this gives me hope that this transmission will handle the power the GT25R will throw at it.
Anyway, that is all.
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So, more planning, cleaning and whatnot happened over the weekend. First, while I didn’t get a pic of this, I took another cover off of the transmission trying to determine the condition of the internals. The cover happened to have attached to it the front differential, and it was as clean as the 5th gear cog was, so that’s really good news. There was some older, dirtier fluid still in the bottom of it, but I can imagine this may be a little lower than the drain plug, and it could’ve just been a settling point for older fluid and dirt. It certainly wasn’t bad, definitely less dirty than my civic at 80k miles, but it wasn’t super clean like the fluid I originally drained from the two reservoirs.
Current build list along with a total. I only have one quote on the turbo so far, looking to get a few more from a local shop to see if I can get some sort of discount, but this price still isn’t bad. Ecu build isn’t going to be as hard as I thought. I originally believed I’d need a trigger wheel on the crank for timing, but I found out from a friend that using a 1.6 CAS from an 89-93 miata would eliminate the need.
Also been taking the time to familiarize myself with TunerStudio, the software that the megasquirt uses for tuning. It’s pretty simple, much more simple than I had anticipated. The tune I have open in the screenshot is what I’m probably going to use as my base map. This is for a friends 1.6 turbo miata, with a build that is damn near identical to what I’m doing. Only big difference is he’s running a GT26R turbo, 6mm bigger than the 25R. Either way, it should be a very close match and saves me a bunch of time in getting this setup.
Today, I’m trying to get quotes on turbos and get funds set up to start collecting some parts. Waiting to hear back from Mazda to see if my missing engine mount is NLA or if it has a 3 month lead time from Japan (happened with the radiator.) Luckily, I have a friend heading out to Japan in a few days for the summer, so if a situation like that arises, it’ll be easy-ish to have him grab a part and send it back.
Lastly, had the time to perform a minor miracle. Hatch actually holds itself up now. Guaranteed it’s cause it’s warmer and the gas expanded in the cylinder, and the rear wiper motor was removed, but it’s a win in my book til I get MPV struts.
Anyway, I’ll stop talking to myself for a bit.
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So, things have happened.
Garrett GT2554R turbo with a custom v band inlet and outlet housing by ATP turbos. Huge thanks to Scott and the folks at HPT Autosport for getting this for me.
This also happened tonight. Motor is finally in. Going to spend the next few days buttoning up everything and making sure anything that can get in the way of the turbo setup is in its place. Car should be heading to ComposiMo next week to begin work on the manifold and other piping.
Super happy this is finally getting going. Huge thanks to all of those that have helped, either in person or with moral support.
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Quick post to catch up on what’s been happening. Motor and transmission are in, and the car is finally at ComposiMo. Don’t have much more to say than that, so here’s a few pics.
Look at all this piping that I get to get rid of….yay.
Finished product, all buttoned up.
Finally at ComposiMo!
Turbos and vbands and boosts, oh my….
Hopefully we’ll get started on this in the next few days. See you next post!
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I figure we’re way overdue for a GTX update. Header is taking time as we’ve been busy at Composimo, but here’s a few pics of it in progress.
PRL Motorsport Flange
Starting to take shape. This is more or less where it stands today.
In the meantime, I’ve been working on the ECU and electrical system.
The megasquirt has been pretty easy to map out. Thankfully, I have an excellent guide written by Ethan Ott for SpitfireEFI (Ethan, thank you tremendously) on how to install the Megasquirt ECU with the 323GTX harness.
Only complaint about the MS system…..anyone see what’s wrong? That’s right! The diagram is backwards. I found this out after about 20 minutes of backprobing the db37 looking for a specific ground…that was fun.
Next step was to get the old harness out of the car. If you ever do anything with engine harnesses or plugs, anything, get this tool kit. Easily saved me an hour of work.
Harness out and exposed.
Next up was mapping the harness out and figuring out where it all went. I didn’t know where this was heading, but it seemed like a good idea. The full wiring diagram in the service manual was invaluable.
It was around this time that I started thinking about what the megasquirt could and couldn’t run. The Evap system was first to go as the solenoids are operated from the stock ecu. Since it’s old enough, and since the county I’m in doesn’t have emissions, it’s not a big loss. Don’t worry, we’ll still have some kind of vent for the gas tank.
So much room behind the intake manifold now. So what do you do with the 4 plugs that would’ve gone to those solenoids? Well, no sense in keeping them.
Everything cut, heatshrunk, then taped back neatly to the rest of the harness. I left enough room on both ends to reverse this in the future if need be.
This…started out as just removing a few plugs. It did not end at a few plugs.
14 in total were removed. This really cleaned up the harness and will make it a lot easier to tuck in the engine bar. This is where we’re at now. Plans are to get the gtx harness mated to the MS harness here in the next week or so, everything is already mapped out so that wont take long. With that, we’ll end there. Thanks for reading.
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