CARBoy

Fuel tank pressure sensor: The GTO ecu wants to know the fuel tank pressure. I had the sensor from the GTO fuel pump assembly. We got a simple T connector from Home Depot and put it in the vent hose coming from the top of the tank. It may not be the prettiest setup, but nobody will see it, and it works. We ran the sender wires through the existing Miata panel plug. See attached pics. The final product included zip ties to hold the sender in place.

CARBoy

Tachometer: This was very simple. We attached the GTO wire to the Miata gauge and soldered in a 2.2k ohm 0.5 watt resistor in a pull-up arrangement. The wire from the PCM goes directly to the tach wire on the cluster gauge. A keyed hot wire with the resistor soldered into it is then spliced into the other two wires. The resistor is not in series between the PCM and tach gauge. The tach now reads only 100 rpm high across the entire range. I can live with that. (Pics to follow)

CARBoy

Speedometer: This was easy. I bought a Dakota box for $85. After some trial and error, we figured out how to program it. It appears to match perfectly while running on stands, but may need additional setting while actually driving. So we are leaving that in a place where we can access it once the interior is re-installed. (Pics to follow)

CARBoy

Water temp senders: There are two, the Miata and the GTO. The GTO was already in place towards the front of the driver side head. The harness connects up to it already and feeds the pcm as required, so no work was needed there. For the Miata cluster gauge, a stock Miata sender is needed. They can be purchased anywhere for cheap, or keep your old one. It screws right into the other head by the passenger side firewall. We replaced the cheap rubber washer with a crush washer. Also, be sure to retain the connector from the Miata harness. I let mine go with the engine/harness by accident. It wires right up to the gauge with only one wire. the other two wires are not needed and we sealed them up. (Pics to follow) Unlike the Miata oil pressure gauge, the temp gauge works well. Any stock Miata sender will work. I happened to get this one: Beck Arnley 158-0604. You can see the three connections. Only one is needed for the gauge: VIO/WHT, violet and white. Looks like purple and white.

New2miatas

hmm that's interesting. As for smog issues. Engines swaps got a little more frustrating with the "STAR" program that was introduced in 2012. The program drastically reduced the number of ecu self-tests that can fail and still pass smog. Nearly every modern engine'd smog legal swap thread I watch has required using the donor car's gas tank. I had not seen someone adapt the original car's tank to work.

CARBoy

Oil pressure senders. There are two, the GTO and the Miata. The GTO is on the top rear of the engine and is stock. It feeds the pcm. We left it in place.

The Miata oil pressure sender was another issue. I don't want to use the Miata cluster gauge. It's not accurate, even when the goo is cleaned out of it. It now shows pressure even though it's not hooked up to anything. How's that for reliability? I happen to have a couple of AutoMeter gauges and a dual A pillar mount, so I'm going that route. There are two ports in the oil galley of the LS2 on the driver side, but neither is fun to access. One is behind the alternator, so that's not possible. The other is above the oil filter. It is possible to use it, but the port plugs above the filter on the oil pan are much more convenient. I have a Mast oil pan, which works great, but it was a huge pain to find adapters for its port plugs. (I wish they had stuck with the stock ports.) They are 7/8" straight threads, or 5/8" 10 ORB. My AutoMeter sender is 1/8" NPT. I finally found a 90 degree elbow that fit, which I attached an adapter to for the sender to fit. (Pics to follow.) The part is 6805-10-08: #10 SAE/ORB Male x 1/2" NPTF Female 90°. I chose the 1/2" NPT side because the larger female end is supposed to increase pressure reading accuracy. Pipe tape was needed to keep the NPT threads from leaking.

CARBoy

Oil temp sender: It's probably just me, but for a daily driver, I like to know that the engine is warmed up completely before I stomp on it, so I like to know the oil temp. I have a dual A pillar gauge mount. One hole is for the oil pressure, so I'm putting an oil temp gauge in the other. Like the oil pressure sender, there are a few places to mount the temp sender. It can T off the stock location on the upper rear of the engine, but it's tight up there. It could go in the oil galley port plug above the oil filter, but that's harder to reach than the port plugs on the filter mount. It could go in the drain plug, but that sits very low and has to be dealt with for oil changes. A bung could be welded to the oil pan, but that's not really necessary. Therefore, we mounted it on the oil filter mount port next to the one being used by the pressure sender. The pressure sender is on the forward port, which is the exit port. The temp sender is on the rear port, which is the return port. (Pics to follow.) The wires for both run straight up against the firewall; very tidy. This is the port adapter I used: Brennan Industries 6405-10-04-O Steel Straight Tube Fitting, 7/8"-14 SAE ORB x 1/4"-18 NPTF Thread, 5/8" Male O-Ring Boss x 5/8" Female NPTF. An NPT-NPT adapter was then needed to fit the temp sender, and thread tape for the NPT threads.

CARBoy

The only code we're getting now is for the skip shift solenoid. It actually doesn't appear be working. So we have to fix it, and then delete it; hopefully with a 2.2k resistor. The smog stuff seems happy.

CARBoy

I know my posts are lacking some details, and pics. Please ask questions or for more pics. I'll fill in more of both in time.

CARBoy

Wheel/tires: My original research suggested that a 245/35 on a 17x9 with something like +35 mm offset would fit, with some fender rolling. (This goes against what the purists say and advice from Goodwin, 949, etc, but we're dealing with horsepower in the many hundreds, so why not?!) We were able to borrow a set from Cord at Catfish (thanks Cord!), who is located next-door to Monster Miata in San Marcos, CA. Instead of 245/35, his were 235/40. They looked awesome, but running the suspension to extremes proved that they were too large in every direction. Rather than gamble with purchasing a set of 245/35, I tucked my tail between my legs and got a set of 15x9 Advanti Storm S1 +35 in grey, and 245/40 Maxxis Victra VR-1. They look great. I have yet to run them to extremes, but they should only need a fender roll. More on that with pics later...
Maxxis

CARBoy

Rollbar: After researching the big players, I went with the NB GT3 from Blackbird Fabworx. The extra gussets, built-in harness bar, better rear view, perfect hardtop fit, and true legal status for SCCA and NASA sanctioned events sealed the deal. The other guys are good too, but this was the direction I went. I can add door bars later if desired. Installation took a good 8 hours and it went in and out several times for measurements, but we paid attention to details and it fits like a charm. The seat belts work ok. They are never as good with a rollbar. The carpet fits nicely...

CARBoy

Skip-shift: Obviously nobody wants the skip-shift to function, but there may be a need to keep it for the referee. It's part of fuel efficiency and the referee may require it. That's no problem, just get it working and "adjust" it later down the road. It only requires a 25 cent resistor to delete. I'll cover that another time.

The skip shift solenoid in my wiring E40 harness has two wires in its plug: grey and pink/blue. The PK/BU is ignition voltage and it's on the same circuit as the reverse lockout solenoid. The grey wire goes to C3 on the pcm. Keyed power to the PK/BU wire goes into C101 pin 5 at the front of the engine. It's the pink wire in the photo. The red and light green wires are for power to the coils. The black is ground. I'm researching the dark green wire. It's supposed to be ignition voltage and it affects the throttle, but it's not yet clear exactly how. More on that another time.

Update: After getting it to work, I've now disabled it using a $10 CAGS (Computer Aided Gear Selector) eliminator. It's a simple plug n play connector. No ECM code too.

CARBoy

Fuel tank level sender: This was one of the hardest items we tackled and we finally just solved it this weekend. The goal was to use the Miata fuel tank level sender, the float, with both the stock cluster fuel gauge and to feed the GTO PCM. The PCM needs the fuel level in order to determine when to open the evap purge solenoid. When the tank is 85% or more full, the purge valve should not open or fuel could be sucked into the evap system. That's bad. So the PCM needs to prevent that. It also doesn't open the purge valve if the tank is 15% or less full, although I can't recall exactly why just now. If the PCM doesn't receive a signal in the correct range, it throws an error code. When the tank is full, it expects 40 ohms. When the tank is empty it expects 250 ohms.

Basically, we needed to splice the PCM wire into the wire going from the tank to the fuel gauge. This proved very difficult because both the fuel gauge and the PCM use different voltages. We ended up using a modified converter unit called MeterMatch from TechnoVersions. Brian from TechnoVersions worked with us to remove one of its resistors. We then ran the engine and adjusted the output of the MM by reading the percent fuel tank level on a OBD reader with the tank full. Knowing the tank was full, we adjusted the MM until the OBD read nearly 100%. That meant that the MM was sending the correct signal strength to the PCM. When the tank is empty we will set the other extreme. Quarter and three-quarter tank levels can also be set. Uneven tank shapes can be accounted for with that. Pics to follow. Feel free to message me if you want more details.

BGordon

Do you happen to know which of the three wire connections is needed?

CARBoy

Oops. I should have posted that. Lots of details to fill in.
It's the VIO/WHT, violet and white. Looks like purple and white. The other two wires are just sealed off.

CARBoy

BIG milestone completed this past weekend. We solved the final two issues needed for smog, in theory: the skip-shift and fuel level. No more error codes. There are still a few other issues to sort out and then it's just a matter of cleaning up the wiring and buttoning it all back together. Soon!

CARBoy

Fuel level sender: This was maybe the biggest challenge we encountered. The GTO PCM needs the fuel level to determine when to open the evap purge. It keeps it closed if the tank is more than 85% full or less than 15% full. The GTO expects a signal range of 40 ohms when full to 250 ohms when empty. We verified this testing the sender from the GTO and its PCM. (I retained a lot of parts from the donor car.) If it doesn't get the correct range, the PCM throws errors indicating high or low. The OEM Miata sender/cluster gauge work within a range of 5-115 ohms, full to empty. (We confirmed full because the tank is full, but empty will wait until I've had a chance to burn some rubber.) The Miata cluster fuel gauge needs to continue to function, while the PCM also needs it's input. So basically we needed to splice the GTO PCM wire into the wire going from the Miata sender to Miata gauge. This presented problems due to varying signal strengths from both the Miata gauge and GTO PCM. We tried all sorts of strategies with resistors and diodes. We even considered attaching the GTO float to the Miata float in the tank, but that's not a great solution and would require routing new wires through the tank. Nothing worked and grey hairs piled up.

We ended up using a modified version of a converter unit called MeterMatch from TechnoVersions. Brian from TechnoVersions worked with us. Great guy. We remove one of its resistors: R1. We spliced a wire into the Miata sender to cluster gauge line. It's BN/BK, brown/black, and runs from the tank to the cluster. We added a 10k ohm resistor in that wire and ran it to the MM input pin #3. Output pin #2 goes to the GTO PCM.

With the engine running, we adjusted the output of the MM by reading the percent fuel tank level on a OBD reader with the tank full. Knowing the tank was full, we adjusted the MM until the OBD read nearly 100%. That meant that the MM was sending the correct signal strength to the PCM. When the tank is empty we will set the other extreme. Quarter and three-quarter tank levels can also be set so that uneven tank shapes can be accounted for. We had trouble getting correct readings using multimeters. We tried three. The signals were too conflicting, or something. That's why we used the OBD reader, which worked well. We will check the OBD again as the tank drops to different levels. Hopefully it works throughout the entire tank range. Pics to follow. Feel free to ask if you want more details.

CARBoy

Well, let's hope the referee thinks it's ok. If the evap system is working, there's no common sense in not passing it. We'll see.

New2miatas

Any new updates? Did this car make it through the referee?

CARBoy

As usual, I'm bad at blogging. It's been a busy couple of months, with some delays on the project due to unrelated events, but we've made great progress. The car will be road worthy next week and we'll start the shake down. All electricals were completed as of yesterday, including a couple of fabricated footwell lights. Most of the interior is in, engine bay is complete. Just the small stuff remains, which takes time to do right. I'll add some more posts on various items. In the attached pics, you can see the engine bay. It's very clean. And the rear end with the Ford 8.8" and 245/40 series tires. I have some JASS Performance hardtop brackets that will need a little trimming; I'll post about that. I have a number of pics of the Blackbird Fabworx GT3 rollbar installation, and will post about that. The plan is to get it tested at a regular smog shop to ensure that it passes the sniff numbers, and to make the referee's day that much easier. They love it when you show up and the car has already passed. Then I'll take it to the ref.

ToySnakePMC

Nice job. You are tackling something that probably would have kept me from finishing my V8M if I had to meet such emissions standards. Thanks for the update, and I like seeing more of these GTO-donor builds! Best of luck when you face the ref.

CARBoy

Today was its first day on the road, and WOW!!! What a day! It's AMAZING!!! I drove around for probably an hour, all over the place, on the freeway; ran like a champ. This week I'll setup front end alignment and initial smog test appointments, then comes the ref.

CARBoy

For whatever reason, the skip shift is not functioning, which is good. The solenoid is hooked up and it should work, but it goes from 1st to 2nd every time. It iisn't throwing a code. So I may be able to write that off as done.

CARBoy

We seem to have a problem. The tank is now at 3/4 full, per the Miata gauge, yet the GTO ECU is still reporting 100% via the OBD reader. So we need to solve that. It may not matter for smog, if I take it will a full tank, but I will sort it out eventually.

Update: We discovered that the conversion box was converted backwards. In other words, it was reading full when the tank was empty and vice versa. We simply reversed the settings at the different tank levels and it works great now.

CARBoy

Cruise control: There doesn't appear to be single report of a GTO engine swap into another car with a successful setup of cruise anywhere on the internet. Swaps from other LS engines seem to make it work, but not the GTO. Even Dakota doesn't make a setup for it. But we are determined to try. This item is waiting until after the referee, but we think everything is currently hooked up to satisfy the GTO setup; we have all of the original parts in the car, we think. So we tried it today, but it's not working. Of well, maybe after ref we can get it to work. It's really just the challenge of doing it. Of course the car doesn't need it.