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John, your build is really outstanding. You should be proud of such an huge accomplishment.
First class build.

Hi John, Have you done anything to feed vehicle speed info to the ECU (VSS circuit)?

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Peace, Ron

Nope. There is no input of the vehicle speed into the ECU. So far it seems to work fine w/out it, but to be honest I didn't think to look into what parameters the ecu may regulate with vehicle speed other than cruise control. I'll eventually be switching over to a standalone ecu, and I don't think they use the vss for anything (I picked up an old Link for the '96 miata, or I may upgrade to a Hydra, but the Link in my turbo miata is still going strong - $100 out of pocket sure beats $2000).

If you have any insight on how the stock ecu utilizes the vss input I'd love to know.

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- John

Sorry I haven't updated the blog in a while. If you recall, about four (yes FOUR) months ago I was starting the process of getting my car legal on the road in Colorado. Just this week I finally got my metal license plates on the car and I have to wait another 4 weeks for the title to come in the mail. I thought the process was going to be fairly straightforward, but it ended up being a royal pain in the ass.

One piece of advice for anyone in Colorado would be to make sure you have proper title or proof of ownership of the engine and trans before you start the title process. In my case I thought I was in the clear because I had a salvage title for the donor car, but because I never bothered to transfer ownership into my name (they changed the law, and I didn't realize it was necessary) I ended up having to get a full appraisal on the car and do a bonded title. In my case it added about $350 (which I could swallow), but it also added what turned out to be 10-weeks to the process, which kinda sucked.

So far I have been able to put about 350-miles on the car and it has been almost flawless. I did have one little issue with the steering column support bushing getting heat soaked on really hot days and because it was a plastic bushing (CTE about 10x that of the steel steering shaft) the plastic would expand; but because the bushing was encased in an aluminum sleeve, instead of the bushing ID growing and becoming looser, it actually contracted and would slightly bind on the steering shaft. It was never a major safety issue, but I ended up increasing the clearance by about 0.002" and now it works fine at all temperatures.

I also added a fire extinguisher in the passenger compartment - just to be safe. And I got a spare shifter from another NA8 miata and shortened the shaft by about 1.5" - the shifter feels much better now, and changing gears is just a flick of the wrist - feels right and looks better too.

The exhaust was a bit too loud for my taste so I continued to play around with some internal baffling. I ended up adding a flange just aft of the collector so I could add something similar to what "car chemistry" makes. Seems a lot of racers use this style of baffle to meet race track sound regulations, and claim it doesn't cost too much HP. I was running it with my side exit pipe for a while and it made a big improvement, but just today I switched back to the rear exit pipe with this baffle at the collector and it sounds really nice. I've test driven a lot with all the different configurations and I really can't notice any loss in performance, but really appreciate the stealth exhaust note - very throaty with a touch of deep rasp - it seems to fit the car very well.

Also, I painted the nose black and it made a marked improvement in looks. My goal for this summer was simply to get the car roadworthy and licensed on the road and I'm finally there. Pretty happy with how it looks. Lately I've been focusing on the upcoming restoration of my '91 BRG miata that I've owned for 12-years (and wrecked 6-years ago....) so I think I'm going to leave the Seven alone for a while and just enjoy driving it - I figure it will be a work in progress for many years to come. Oh, I may make a bikini top and some doors over the winter, but the car is a hoot as it is.

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- John

Some manufacturers use vehicle speed to trim fuel and timing. I haven’t found a reliable source that tells me whether or not Mazda implemented this in the NA Miata’s.

Congrat’s on getting it licensed!

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Peace, Ron

Congratulations on the metal plates, John! I'll keep your advice in mind when it comes time to register mine. Would love to see the car again and maybe go for a ride sometime.

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--Eric

"Stuckness shouldn't be avoided. It's the psychic predecessor of all real understanding." --Robert Pirsig

Grey 2019 Hyundai Veloster Turbo
Red 1989 BMW 325is

Wow, I guess it's been almost two years since I posted anything here. Sorry about that - life has been busy. My goal was to get the car on the road, then have it be a work in progress for a while - that's exactly what it's been.

Overall the car has been great! I've put a bit over 2k miles on it so far. I had a couple of minor hiccups early on, but I've spent a bit of time refining things and it just keeps getting better. Still haven't had it on the track yet, but that will come.

There were two problems that other members of the forum had expressed concerns about, and they were right. The first was my LED 3rd brake light - I ended up blowing that out early on due to too much current - I simply re-built it and added current limiting resistors - been working fine ever since. The second problem was a real PIA until I figured out the solution. Due to the fuel pickup being on the far right side of the tank, with anything less than 3/4 tank of fuel it would starve and surge while going around right hand turns at speed. This severely limited the fun factor, and I ended up not driving the car nearly as much as I would have because of it. My original plan was to run a separate surge tank and pressure pump, but I didn't have any time to make it, so I let the car sit. I was talking to my buddy Josh who races Class 11 Baja and rally-X's a bimmer and he recommended a new product that Holly had come out with - the Hydromat. I checked it out and decided to give it a try. The thing is simply magic! By doing nothing more than replacing the fuel pickup sock with a Hyrdromat, and locating it near the center of the tank, I have never had a single fuel surge since, and it will drain every last drop out of the tank without giving you a warning that you're about to run out of fuel (ask me how I know...). It's an easy solution, and I wouldn't consider building another race car without it.

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- John

Some other details I've added: Body trim surround on the exhaust opening, simple bracket on the wind deflectors to keep them from flying forward during hard braking, new shift knob (shortened the shifter rod as well) and E-brake handle.

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- John

I added a wideband O2 sensor and gauge to assist with future engine tuning. I made a sliding bracket so the gauge can be tucked away when not in use - otherwise it interferes with the passengers legroom.

I also played around a lot with different exhaust & muffler combinations to try and quiet the car down while retaining a nice throaty sound. I ended up making my own muffler - 6" diameter aluminum case, with a 2-1/2" perforated core wrapped in stainless steel wool and fiberglass packing. The muffler was a little bit too quiet at first, but now that I've upgraded the engine to something with more compression and better breathing, it's perfect (more on the engine later).

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- John

The new muffler removed the restriction of the previous baffle I had made, and definitely pulled harder up top. In preparation for some engine changes, I added a 5X racing AFPR to allow some simple tuning of the fuel curve while retaining the stock ECU (spec miata trick). This simple change really woke the stock motor up - felt like maybe 5-7hp by the seat of the pants. Since I was planning on swapping in a new motor soon, I was curious to do a dyno run of the stock engine so I could make future comparisons. 122-whp, and 114-lb*ft of torque - not too shabby for a stock, low compression '96 engine. Before the dyno I had simply tuned it by feel and the AFR gauge - the three runs show different fuel pressure setting I was curious about - funny, no real change in power, but safety factor at WOT can be seen. The thing the dyno does not show is how different the engine feels at part-throttle settings while driving in the real-world.

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- John

In preparation for a fresh motor build, I modified an oil pan for improved ground clearance. I was able to gain 1-1/4", which is almost a 50% gain in ground clearance - much needed clearance, as the stock pan sat only 3" above the ground. I also made a splash baffle to help keep the oil from splashing up the sides into the crank. I had to modify the oil pickup tube - this was easily done by heating and bending.

The end result is now in use, and added a little under one Qt to the capacity of the sump. No issues with oil starvation that I can tell.

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- John

Since the transmission bell housing now hung lower than the oil pan, I shaved about 3/8" off of it.

Here's picture of the transmission mount I made after 2k-miles - still looks new. Glad to see it's holding up to the abuse.

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- John

Long story short: I rebuilt one of my spare '99 engines - blue printed, balanced, & minor bowl blending - all stock internals - just grabbing the low-hanging fruit. I used ACL race bearings and Sealed Power rings & valve springs (stock 1.8 pressure). I also zero-decked the block (-0.014") and shaved 0.028" from the head to improve squish and bump the compression to a true 10:1. (side note, the stock 9.5:1 engine actually CC'd at only 9.2:1).

My theory is that this is about as far as I'd want to go while running on the stock ECU on pump gas. I've had the engine in for a couple of weeks now and put 185-miles on it. Breaking it in by not babying it, and just did the compression test at 180-185 psi across the board (at 5600-ft elevation - using a correction factor of 0.853 for altitude this would be 211-216 psi at sea level). This engine runs pretty strong, and it keeps getting better. By the feel I'd say it's maybe 15-20-hp more than the stock '96 engine. I want to run it another 1000-miles on 30w dino oil before I switch to synthetic and put it on the dyno.

I'm currently running a VTCS ('01-'05) intake manifold that has been de-butterflied and port smoothed. I will also play around with the VICS manifold to see which one feels better - maybe do a dyno comparison when the time comes.

The idea for this engine is that if I'm happy with it on the stock ECU, then I saved a ton of money and tuning headaches. If I later decide to do an all-motor build, then I can still swap this engine in to my bone-stock '93 miata DD, and it will run fine on the stock ECU in that car.

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- John

I forgot to mention that I also swapped out the stock brake pads for some porterfield R4S pads. I run these on my DD miata and have been pretty happy with them both on the street and for limited track use. I'm pretty happy with the swap. They're certainly not full-race pads, but they are very easy to live with day-to-day, and the performance gain over stock pads is noticeable. I think they're a good compromise.

I have also spent a lot of time tracking down and eliminating rattles and squeaks on the car - these little things make a big difference when driving the car. There is still plenty of mechanical music coming from the car - the very light flywheel makes quite a bit of drivetrain noise, especially on decel, and the intake and exhaust are very vocal. The car is a real hoot to drive.

Future planned changes are to modify the intake manifold (or fab custom) to move the throttle body to the rear of the engine, and add an airbox ala Caterham 420R (see photo). That will allow me to run a full-width radiator with proper surround baffling to improve cooling. The cooling system is fine, but in stop & go traffic it does get a bit warm, and I know the intake is drawing in hot air from around the radiator.

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- John

A truly awesome build!! Thank you for the updates John, what thickness Ali did you use to do the sump modifications?