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This is my 05. Bought it for 2800$ with 120k on it. Car has a salvage title for front end damage. Googling its vin you can find a black NB2 with the front end smashed off. This car doesn't have any evidence of being repainted.
I autocross the car, and possibly will track it.
Car has a bunch of mods, but big ones are MS3, RB header, Roadstersport3 Exhaust and a DIY'd intake. I'm still wishy/washy on if I want to buy another Miata to autocross, and then turbo this one.
Could the torque curve’s initial shape be influenced by the pull start point? 3k for a pull to start seems a bit high, not sure why the tuner did that. Dyno Limitation?
Dyno pulls from before MS. Torque curve is way broader. Different dyno, so numbers don’t compare. Does shape?
Sat in the drive through of a pharmacy. Which usually is only a 5 minutes wait, but social distancing made it about 20 minutes.
My cars idle got worse and worse. It wouldn’t die, but watching the AFR gauge I figured I was heatsoaking. I was at 16/17:1
Everytime my Fans kicked on, my IAT sensor would read 30F higher. Ambient was about 50F.
I did some testing in my garage and figured that my idle issue was being caused by bad IAT sensor placement.
My sensor was behind a heatshield (an aluminum air box), behind the passenger side headlight, and threaded into a PLA body.
But the sensor wasn’t in the engine airflow path. Just next to the filter.
The PLA mount would get warm, but never as warm as the brass sensor did.
I tried hanging the sensor by it’s wire, and it still got heat soaked.
I put the sensor into my intake tubing, smack dab in front of the valve cover, and that was just heatsoak city. No engine air flow was helping it out.
Then, I figured that my air box, even though it was insulated, sealed against the body and hold just wasn’t cutting it.
I tried putting the sensor up by the driver’s side cowl to see if that was a good spot for me to relocate everything, and it too was getting hot. And it doesn’t get good airflow when driving.
I put my sensor into the bumper. No heatsoak, but then my AFRs went rich. The intake air was getting heated.
The GM IAT sensor that we all use, with the brass body is to blame I say. I pulled my sensor out when it was reading 90F, used a laser thermometer to double check it’s calibration in TS. It was good. The body was reading about ~120F. If I blew on the sensor, it would read lower. But as soon as I let off, it would heat back up. This is how I’m making the conclusion that the brass sensor body absorbs too much heat. I tried this with two brands of sensors, and got the same result. During this test, the sensor was sitting in ambient air.
I could then determine that the crossover tube was an issue as well.
We all love the hole behind the driver’s side headlight, so I made it a friend on the passenger’s side. I used some old intercooler piping I had lying around and fit the filter just below the chassis, in the wheel well.
The sensor also now lives in the wheel well, just above the filter, in the intake piping.
My heatsoak tests are going way, way better. Even when the A/C fan kicks on. I’m still seeing some heating, but it’s in the 5-8F range, vs 20-30F. And today has a higher ambient temp to boot.
The heating I’m seeing, does not contribute to a massive AFR change, and I suspect this is because it’s getting its heat through conduction of the piping. Which, I can believe is good enough for now. As the intake charge is obviously being heated too.
Some crappy pictures to get an idea of my hackery.
I can’t go out and get a plastic style GM intake sensor because of what’s going on in the world, so I’ve ordered one. I’ll see if it does better, heat absorption wise.
At the dyno. Heatsoak was a big issue here. This is the only picture I have handy of my old intake The pipe was wrapped in electrical tape, and F4 tape to prevent it from being damaged while banging into the metal hole. Unfortunately the FM crossflow + FM reroute put the coolant hose straight under my intake. There’s about 3mm of space between the two tubes. I drove the car and checked for evidence of abrasion. I didn’t see any. I’ll be making a bracket to hold the tube down another CM or so, for safety.
Driving the car, I can definitely feel the dip in torque that having a shorter intake path gives. However, it would really act funny around the 4300 mark. Right about where VICS would shut on/off. (4250 was picked by my tuner).
This got me to look at my tune, and compare to others. I had the same
Power on Values: Off, Active Value: On. BUT rpm > 4300. I think this effectively reverse my VICS operation.
I'm a bit confused by the operation of the VICS. When the output is on, it grounds the solenoid, which is now open. So vacuum pulls the solenoid to what, close the butterflys? I want the smaller chamber at lower RPMs, and the bigger at higher.
Has anyone tried hooking up a MAC Valve to the VICS actuator to get a variable VICS?
Since posting the picture of my intake, I managed to use a "VTCS Solenoid" signal (labeled so in the WD) that lived on the passenger side for my IAT signal. That way I'm not running a wire across the engine bay.
In addition, I used a couple of other mysterious solenoid signal wires that ran to the ECU as inputs for another IAT sensor (one sensor lives in the engine bay, the other in the wheel well) and an oil temperature sensor.
The 5V pull-up is done by using the 5V line that used to go to the MAP sensor. A couple of 2.4k resistors were used.
I soldered everything onto some perfboard, covered in some hot glue, and heatshrunk over. Been using some fake AMP Superseal 1.5 connectors to build my own harnesses, along with some no-name brand crimpers that work well for the sealed pins.
Depinning the Multlock HD connector at the ECU was a royal PITA. The 2 rows on the NB and NA are way easier to depin. The locks on the 3 row just wouldn't disengage from the pin. I had the gate pulled down all the way too. No idea why it was so hard.
I also pulled out the fuel dampener that sits on the frame rail. I've found a few posts here and there from people running without one, and having zero issues. I pulled mine, and managed to gain some clearance for my reroute hose.
I did manage to mess up the easy, quick job by not clipping the fuel line fully onto the hard line. Took me a minute to realize why my engine wouldn't start, even though I could hear the fuel pump prime. Took me a good 4 primes before I smelled gas.
I'm not sure how I feel about the new intake. It has a bunch of bends. The 90 coming into the TB is pretty harsh, and probably doesn't help things. It really doesn't feel like its helping my N/A motors bad torque.
I've thought about sticking on the resonator from the stock intake tract, just to see if it does something.
Another idea would be to run the intake up the engine bay, relocate the windshield washer bottle and build an airbox there. Cut some holes for a Randall-type intake?
03-18-2020, 03:27 PM
Nordic Fjord Spice Sparkle NB2
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