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Bought this car 2 years ago when my dumb K24 NB was taking longer than planned and I wanted a quick and easy track car. Here's the car when I bought it. Had 700/400 Ohlins, Giken, rollbar, seat, and something like 155whp from the stock 2.0L. And a totally ridiculous Affinity wing that I still need to sell.
I ended up liking the car A LOT, and when my NB still wasn't finished last summer, I said **** it and took the NC to the cage builder and started buying parts for a 2.5 swap to make it a GLTC racecar.
The rest of 2020 was a struggle. Got 4 bad motors from LKQ before finally getting one that I was willing to put in the car, and then had non-stop issues with the factory wiring harness for the rest of the year. Didn't make a single GLTC race after starting the 2.5 swap, but did make it to a few NCM test weekends.
So I tore out all the factory wiring over the winter and had Haltech Chris do a full rewire with a Nexus PDM. We intentionally left the loom off to start so that we could fully verify the harness and then go back and add Flexo braided split loom. Also yes my cage and interior still aren't painted. It's been high on the list since the day I got the car back from the cage guy but other **** keeps going wrong and taking higher priority.
Did a few test weekends at Putnam and NCM in March and early April to get ready for the April NCM GLTC race, and the car was great. I still needed a dynojet sheet for GLTC classing and finally got an appointment the week before the race. Disappointing results... 186whp and I needed to be 196 minimum, preferably over 200 so that I could detune for flat power. I'd already noticed that my straightaway speeds were really disappointing at the previous test days, but my driving always sucks at the first few events after winter so I'd just been working on myself instead of blaming the car.
Comparing data with a couple other fast GLTC guys at the race weekend was the final confirmation that my motor is a turd, so I started looking for quick ways to fix it without going too extreme and missing races. The other NC GLTC guys have been blowing up lots of 2.5 motors (stock and built) and also having problems with the 6 speeds (stock and built) so I started thinking outside the box.
Old setup:
-2.5 Fusion motor with Esslinger St.2 cams and full Goodwin exhaust
-Walter Motorsports 6sp
-NC 4.1 diff with OS Giken
New:
-Unopened 75k mile 2011 NC2 2.0L
-Stock NC2 5sp (same ratios as NB)
-RX8 diff conversion with 2010+ 4.77 ratio (will get a Giken later but running the stock LSD to start)
-Fab9 GT turbo kit with Kraken top mount manifold and GT2860RS (smallest they offer) https://fab9tuning.com/fab9tuning-gt...-kit-nc-06-15/
I started this thread because this will be my first turbo experience and I didn't do near as much research as I should have before buying. I talked to Passey about his experience with this turbo kit on the Good-win time attack car and I feel pretty good about the reliability aspect, but I'm still very unsure about the turbo choice and the boost control and tuning stuff for reaching my power goal of 195-210 with a flat powerband. Fab9 said this turbo is going to want to make about 240whp on the low end on a stock 2.0L.
I did some more turbo reading and I'm questioning whether the GT2860RS is the right choice. I did a little searching before placing the order and it looked like the potato was a little too big, but the smallest option that would work with the fab9 manifold and downpipe. I'm trying to avoid any customization so I can just get this on the car quickly with the standard kit parts.
The garrett website shows the 2560 as having a different shape 5 bolt flange than the 2860RS, but I now see that there are a lot more options than what's on their website. I found this one that should be a perfect fit for the fab9 kit. https://www.atpturbo.com/mm5/merchan...Code=GTGT2560R
So right now the top options I'm seeing are:
GT2560R
GT2860RS
GTX2860R (seems like a waste?)
EFR6258 with custom downpipe
It sounds like the NC 5sp might be a little stronger than NB, but I'm guessing I should still try and limit it to around 220-230 wtq. So my goals are around 200-210 dynojet whp at 7500 rpm and 230ish wtq at 4000-4500rpm if I want to do a serious flat power tune. I'm feeling semi-competent on the compressor stuff but I still don't have a great understanding for the turbine side, especially the limits of internal wastegates when trying to run low boost at high rpm on a small turbo like the 2560.
Once I ported my wastegate on the 2560, then it was able to hold low boost to redline on my NB. The stock turbine has a hard 90 degree turn for the gate and the air doesn't want to make that turn. The bigger engine will affect power levels some, but the 2560 is probably better sized for GLTC power.
I've haven't been keeping up with turbo stuff since my K-swap, but I think the EFR turbos are considered better.
I think I'm settled on sticking with the 2860RS but I'm still open to advice. I found this dyno from fab9 of a stock NC2 2.0L with nothing but their 2860RS kit, I think on wastegate pressure only. I haven't been able to get an answer from them on which actuator ships with the kit... seeing 7psi in one spot and 12psi in another.
I love the NC, the 2.5 swap thing always looked awesome to me until I saw so many blowing up when subjected to serious track duty. This might be a good solution. Lots of room up front for a V mount too.
One thing a long time turbo Miata racer friend of mine and I talked about on my low boost BP for GLTC is that a larger turbo can improve driveablity. On his 1.9L BP he prefered a 3071 to an of the GT25 or GT28 series turbos (at that time). The slower response actually allowed him more throttle control a corner exit even with boost by TPS setup.
One thing a long time turbo Miata racer friend of mine and I talked about on my low boost BP for GLTC is that a larger turbo can improve driveablity. On his 1.9L BP he prefered a 3071 to an of the GT25 or GT28 series turbos (at that time). The slower response actually allowed him more throttle control a corner exit even with boost by TPS setup.
That's something I've been thinking about. Going bigger should mean less engine bay heat for the same hp numbers as well which is definitely a plus. I'm definitely not seeing any reason to go down to a 2560 at this point. The fab9 2860RS graph above is at full torque by about 3500 which I'll never even need.
Jensen Little with the badass time attack "NC HAMR" actually suggested I move up to a GT30 series as well just for less heat and stress, but I'm really worried I couldn't get power turned down low enough with a turbo that big. Goodwin upgraded their fab9 kit to a 2876 (I think) and melted the plastic valve cover on the first day out, so there isn't much room to go bigger with this manifold. One easy option would be to swap my 0.64 a/r housing for a 0.86, but I don't know if it'll make enough difference to be worth the effort.
Talked to Brian at fab9. He's pretty sure the graph above was with the 12-14psi actuator but he thinks he remembers it only making around 9psi. Wastegate blowing open I assume? They normally include the 12-14 actuator but shipped my kit with the 7psi actuator.
Any thoughts on what I'm going to need? I'm starting to think I'll need a twin port to hit my flat power goals. Turbosmart only makes a single port as a bolt on kit for the 2860RS but they said it's pretty easy to buy the universal twin port and bend the rod to the shape needed, and I can buy the bracket and clevis from the disco potato kit separately.
One thing a long time turbo Miata racer friend of mine and I talked about on my low boost BP for GLTC is that a larger turbo can improve driveablity. On his 1.9L BP he prefered a 3071 to an of the GT25 or GT28 series turbos (at that time). The slower response actually allowed him more throttle control a corner exit even with boost by TPS setup.
This delayed throttle response is the exact thing I'm trying to unlearn since I've gone NA. My turbo used to do the throttle modulation for me.
Long time no update. I worked on the turbo stuff some back in May when the parts arrived, but between day job, miatahubs, jerfspeed, and racecar, I got burnt out and needed a break. Didn't touch the NC for a couple months. Been hitting it hard for the past few weeks and finally hit the dyno last week and track today.
Catching up on old stuff...
Followed instructions found in another build thread and drilled the block for the oil drain. This SUCKS. I attempted to drill it so that the fitting is parallel with the ground, but the block is angled at this location so the thread engagement is weird. It's impossible to get a proper NPT thread seal because as you're threading it in, the top is wiping away the sealant and the bottom side is left with no sealant. It leaked at first startup and is currently gooped up with a shitload of RTV which I'm not happy about. DO NOT do it this way. Fab9 includes a fitting that runs the turbo oil drain into the drain plug on the oil pan, which I didn't like, but I would 100% do that over this specific block drilling method.
Made a little hold down bracket to use a 2.5 bar mazdaspeed3 TMAP (IAT and MAP) sensor. The mounting hole is on the wrong side for the NC intake manifold.
Cheap Dorman 5/8 elbow for the PCV hose, otherwise it will kink and block flow.
Downpipe brace inspired by inconel stud research and bob bundy.
Managing coolant temps has been one of my biggest concerns with the turbo setup and I was adding a decent chunk of weight to the front, so I decided to mount the engine oil cooler under the trunk. Derale 15865 25 row cooler assembly with fan for $210. Has AN10 ORB ports instead of metric and looks identical to the setrabs I've seen. Also Derale filter block, which has AN10 instead of metric and looks identical to setrab. Mountune takeoff plate for the block.
Alternator relocated to intake side with Mazda3 unit. Some grinding is required to clear the steering shaft but I also did some mods I hadn't seen mentioned before to clock the power cable, otherwise the positive terminal was closer than I liked to other metal bits. I wouldn't do this alternator relocation unless you have good reason. Getting the alt in and out is a pain in the *** and requires draining the coolant. The stock location is much easier to service.
Unmodified (but damaged) one that LKQ sent in an empty box with zero packing material...
Modded:
The image below shows the bolt that needed clearance for the steering shaft.
Trunk patch panels after oil cooler install.
New dash bracket for fire system pull handle and stock mirror controls.
Custom 11ga stainless heat shield and some heat wrap around the turbo. The heat wrap on the drain hose was poorly done. I thought I melted the drain hose at the track today (based on the amount of smoke) but it was just the heat wrap burning from touching the turbine housing. There's a hose clamp under the heat wrap... I'm going to get some smaller diameter heat wrap and put the hose clamp over the heat wrap instead of under.
Turbosmart dual port wastegate with custom bracket and clevis. The clevis was a super rushed hack job but it's working fine so **** it. I'd already bought the parts and started fabbing this setup when someone posted a few weeks ago about this turbosmart unit having a shitty amount of travel before it gets in a bind, and they were correct. I stuck with it anyway and it's working fine. The wastegate flapper doesn't open ALL the way before the actuator binds, but I ported the wastegate opening in the turbine housing and so far it's been good down to 3-4psi of boost.
I mentioned in Emilio's Kaiko build thread that I'd go bottom mount if I were starting over, and these pictures show a little glimpse of why. Everything is super tight around the ABS pump and brake hardlines, and the whole "easy maintenance of a top mount" that I had in my mind doesn't exist. The custom bracket for the turbosmart took multiple revisions.
Dyno time. Started with a 5lb spring but it kept wanting to make 220-240hp no matter what we tried.
We were having some weird fuel issues, so I went home and ordered a set of ID1050x and swapped to a 3lb spring. Back on the dyno and got to this after a bunch of pulls. 7-8psi down low and 3-4 up top.
Did a single pull with 6psi commanded across the board, but it was running out of fuel pump up top so we stopped here.
And finally some glamour shots at the track today. I got there late and only did 2 shakedown sessions before I thought I melted the oil drain hose and packed up, but it drives great. It felt pretty rowdy when I took it out for some street driving last week so I was worried that boost onset was going to be tough to manage on track, but it's super tame at high speeds. Feels basically like my old 2.5 but with a much fatter midrange. There's one slow turn at NCM where I had to plan ahead with my throttle input, but I think I'll get used to that pretty quick. I just hope it's reliable.
Oh yeah, I finally painted the interior and (mostly) loomed the harness. I ran out of loom and keep forgetting to order more. I hate windshield glare/reflections and I love the way modern carbon tub racecars look with bare matte carbon, so I decided to ignore the people telling me it was a terrible idea and try flat black interior paint. I loved it at first, then immediately hated it when I started putting stuff back together and getting sweat and oily handprints all over it, but now it's starting to wear in and I love it again. Terrible for a show car but nice and functional for a racecar.
IT DIDN'T HAPPEN UNLESS YOU HAVE VIDEO! We demand vidz
What trans and final drive did you go with for this? Also, I see that mirror adjuster on your little cluster, I vote to ditch the OEM mirrors all together!
Stock 5 speed from an NC2. Was originally going to do RX8 4.77 diff conversion at the same time, but my first event for the turbo was supposed to be the GLTC race at Mid-o and the NC 4.1 with Giken looked like a much better fit for that track, so I left it. I'm gonna leave it for the rest of the year and decide on the RX8 diff over the winter.
05-01-2021, 12:49 PM
NC GLTC low boost turbo build
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