When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
It took me a second to get this. I propose a Lamborghini bull front half, representing the car's powerplant, combined with the backhalf of the Redbull Bull, representing my late night fuel.
Car wasn't broken and I had a full week until an actual competitive event. So good time to stick it on a dyno a try to yeet some rods.
First off I want to say tuning the 07K felt much more like tuning a BP then a K. And I appreciated all over what an incredible engine the K was when it came to raw performance and numbers. The K responded better to boost, wanted far more ignition angle, had a far greater effective VVT, and ultimately... yielded a better power curve.
07K: 501whp, 450tq.
Initially I was revving it all the way to 7500... It didn't like it. Power drops off hard after 6500. I lowered the limiter to 7000 for the rest of the dyno session.
Power seems great, right? 500whp/450tq, solid torquey motor! But then I pulled up the peak dyno plots from the K... wow. What a motor. Same dyno 9 months later, same turbo, same fuel. Yeah the 07K has an automatic behind it instead of a manual, but AFAIK the 8HP locks up tight unless commanded otherwise so shouldn't be losing much to the torque converter.
Blue is peak K, red is current 07K.
Wow. K's are monsters. 90ft/lb, 120hp more at 4000RPM, 60hp/80ft/lb more at 6000RPM, and K still keeps going to make peak power at 6300. It's a damn shame they vibrate chassis to pieces and don't hold together all that well with the balance cartridge deleted.
Now, a few caveats. That was a fully built, high compression K with a super short cast turbo manifold. Rods, pistons, 12:1, bigass cams, light valvetrain, balanced, ect. 07K is a 9.5:1 motor, right from the junkyard, and I don't think it's at peak health... cylinders #3 and #5 run about 100* lower EGT temps then the other three. I've not bothered to compression test it. I'm also mildly doubtful of the overall efficiency of the turbo manifold as it has quite a few tight bends and is very much unequal length. A slightly better comparison is stock for stock, although the K was on the smaller G25-660 turbo and Z3 head.
07K comes out mostly on top... I think I did eventually turn the K up more than this, but then sent the motor into meltdown shortly after. Still, the differences in low end torque, where I expected the 07K to really shine, shocked me. K24 peaked at 26-28PSI, 07K choked out around the same point. I shoved 30PSI into it to break that 500whp mark, but it was basically down to gaining 5whp/psi at that point. When I build an 07K, cams or intake porting might be avenues to explore to help extend that powerband and find some more effective RPM.
All three generations together. Built K, stock 07K, stock K.
End of the day... number is lower, yes, but I don't think it's necessarily a "bad" thing, or that the car will be substantially slower because of it. While I dyno queened the K at 600whp, I only put that much power though it in 6th gear. 450-500whp is much more faithful to where it lived at normally. Gears 1-4th are still very much traction limited, not power limited, and with the faster shifts/respool time from the 8HP I think the power will be put to use much more effectively. And of course, the 07K doesn't shake your teeth out, loosen your ball joints, or break turbine housings. Biiiiig ups for that.
If the internet is to be believed, the 07K will live for quite a long time at 500whp. Time will tell.
First hillclimb of the season this weekend in Pineville Kentucky. Hope to run with NASA at CMP the week after. Here's to a season of DIY R8 noises
First off, congrats on surviving the dyno sesh and the 500whp
Honestly, I'm really surprised at how aggressively the 07K falls on its face after 6K. Maybe that's more a testament to the K series and not a detriment of the 07. Would more aggressive cams on the 07K allow the VVT to operate in a more effective window up top?
Like you said though, with the 8HP blipping through the gears it probably won't be hard to keep it in the powerband and in boost.
Honestly, I'm really surprised at how aggressively the 07K falls on its face after 6K. Maybe that's more a testament to the K series and not a detriment of the 07. Would more aggressive cams on the 07K allow the VVT to operate in a more effective window up top?
Same. I didn't expect it to make power up at 7500/8000 like the K, and honestly I didn't expect same peak power, but how hard it falls off really surprised me. Cams would probably help, as hard as the turbo is pushing it seems like it has to be an airflow limitation. But cams/porting/valves are all $$$ that I don't feel like putting into this current motor. Future things.
Last edited by Wingman703; Apr 22, 2026 at 12:11 AM.
Two upcoming back to back events? Sounds like you have plenty of time to punch those dyno numbers into @Padlock’s tractive force calculator!
Just spitballing off of your gear ratios, I’d imagine it’ll be easy to keep it between 4k-6k on track. Were you able to feel that fall off at 6k pre-dyno? I’d imagine it’d be really noticeable on the butt-dyno.
Same. I didn't expect it to make power up at 7500/8000 like the K, and honestly I didn't expect same peak power, but how hard it falls off really surprised me. Cams would probably help, as hard as the turbo is pushing it seems like it has to be an airflow limitation. But cams/porting/valves are all $$$ that I don't feel like putting into this current motor. Future things.
Any chance the cam timing was off either physically or in the VVT settings?
If that really is how the stock motor behaves I'm sure someone will have a remedy soon as these motors seem to be gaining popularity quickly.
Secondly... the sharp drop-off at 6k rpm does NOT seem cam related to me, but it does seem valvetrain related. Something serious is causing that drop in VE. My bets are that you are seeing valve float causing cylinder filling to go to hell, power nosediving, and torque falling harder than airflow alone would predict. You're likely making enough exhaust and intake pressure for valve float on either side to be a risk and that turbo shouldn't be running out of breath at only 500hp. That hp curve is probably good for another 40-70hp up top if it didn't fall off a cliff. Looking forward to seeing what you find to resolve it, but in the meantime, best of luck at your event!
Nice work on the swap! Watched your video and the car sounds amazing and these engines are incredibly reliable units in the racing world once you find the magic setup.
I don't spend much time on the internet but was pinged by a racing buddy on your build. I went through several rounds of oil pans for this exact swap running the 07k in our Miata for the Champ Car endurance series a few years back:
Getting proper oil pickup geometry with this engine is the principle challenge of the swap. Like you, I spun a lot of rod bearings until I got it right. Looks like you're on the right track from your photos and hopefully you have success. I tried for a few years using home brew solutions before I solved it with a billet oil pan:
Now the car will sustain 1.5g in the carousel at Road America and not drop oil pressure with 250 degree oil temps on 0w-40.
Anyway, I don't want to clutter up your thread any further, but you're welcome to reach out if you have any questions with the swap or get stumped with the oil pan or any other issues.
I went through several rounds of oil pans for this exact swap running the 07k in our Miata for the Champ Car endurance series a few years back
-Paul
This is awesome! I've heard a few people say "oh I've seen an 07K in a Miata before" but this is the first real, hard evidence I've been able to find of it! Does this car still actively compete or is it mothballed currently?
I'd definitely love to pick your brain on a few things... That billet pan looks super fancy, and I'm also guessing pretty expensive. I'll shoot you a PM at some point if that's fine. Sorry for the late response, I was at the hillclimb season opening event all weekend.
So this weekend was the opening event for the 2026 Appalachian Hillclimb Series, Pine Mountain hillclimb. It was also the first competitive event this current form of the car has been to.
Saturday was... a total mess. They were trying a new timing system that turned out to be extremely sensitive to everything and returned zero reliable times. It was so bad they declared all day 1 runs "practice". So not only did we only get 3 runs all day, we didn't have ANY times until later that night when they were able to hand calculate times or something.
The car didn't really care the times weren't being recorded and popped up a handful of issues anyway. First, the EPS motor sheared the mount that kept it from rotating around the steering column, so every time I turned the wheel it would swing 20* and wack something. This might be because I had cranked up the assist to turn the newish 275's with the tiny GT wheel to get around this tight course easier. I strung a bunch of zipites daisy chains to the cage crossbar and... somehow that held.
The more concerning issue was the brake pedal migrating around. I think run #2 I went to the brakes and it felt like I had soft pedal... but the car still stopped normally. Then next time I went for them the pedal had moved over an inch, and continue to move over towards the dead pedal. Once I got to the top I popped under and found the actual OE bracket that holds the brake pedal was bending and allowing the pedal to move. To be fair, I had trimmed this bracket a loong time ago to help fit the EPS motor controller, but its been a few years and its never given me an issue till now.
As I'm typing this up, I'm realizing the motor swinging around probably wacked the bracket at some point and weakened or bent it, starting everything. Huh.
Anyway, that's where the pedal ended up after each run, compared to where it should be.
Sunday the timing system still wasn't fully operational so they were basically calling in raw time stamps and car numbers to a base station and manually calculating times. A late start, slow manual timing, and a few cars going off ment Sunday was a repeat of Saturday with only a few runs. I think this was the roughest event I've ever been to in terms of flow. Definitely frustrating for everyone involved.
I toughed the sketchy brake pedal out for three runs on Sunday, but then I almost blew the brake zone for T2 and decided that would be my last run. It was also my fastest run of the weekend, landing a solid P2 in class, and 1.5 seconds faster than my previous PB on this hill. Was a really good battle for P2/P3. Cody in P1 beat us all by a few seconds, as is normal. I think once I get some more seat time with this setup and get the car a little more optimized it will close the gap to him a good bit.
Also got my P2 championship trophy from last year.
The 8HP was incredible all weekend. Zero transmission or engine issues. Got a ton of compliments on how the car sounded. Car definitely needs a longer diff though. Top speed was only 92mph and I'm already in 5th for that. Tons of fun banging 3 gears on a small straight but probably not the quickest.
Half dozen items to fix/address/change then I'm taking it to CMP to run NASA TT this weekend. Quick turnaround.
God damn, that road crown is so gnarly. Props for ripping that thing as hard as you were haha. Glad to see the car doing what it was meant to do again and can't wait for the CMP report.
Before heading to CMP, I addressed a few pressing issues. First off was the brake pedal that was relocating itself. The crux of this issue was that I had trimmed some of the OE bracket that holds it in order to better fit the electric power steering ECU. While it had been fine for a good amount of time, I guess over time the metal had fatigued and allowed it to twist.
Red line is where the OE sheet metal had been, mirroring the opposite side.
I pulled the EPS "ECU" off the steering rack, it juts off the column at an unfortunate angle which is what caused the interference in the first place. I had to extend the 4 wires from it to the motor assembly, but this allowed me to mount it at a better angle and directly on the column itself. I threw some silicone over the now exposed wiring contacts to prevent any future issues from metallic dust/general grim intruding.
With the ECU out of the way I welded back in sheet metal to approximate the OE design. I also added a secondary "anti-rotation" bracket to the other side of the collum(can't see it in this photo) so the entire job of bracing against the motor rotation wasn't also on the brake pedal bracket. I slammed my full body weight into the pedal a few times and it no longer travels side to side.
Accusump was installed in the truck and plumbed in. The iABED oil filter adapter plate I have has a spare 10AN port that dumps just pre-oil filter, so that made it very easy to plumb in the accusump. Of course, the 10AN line from trunk to engine got its own dry break. I opted for the remote manual lever over any ECU controlled valve. After asking around, it seems the optimum and easiest way to run these is open the valve on your out lap, and allow it to fully regulate on its own, then just remember to close it again during your cooldown lap before you hit paddock so its filled and ready for the next session.
Thought an amusing series of events, I ended up with a precut 1/2" birch splitter blade. Its waaay lighter and in better shape then my janky old plywood splitter, so I wet laid a sheet of fiberglass over the top for support and threw that in. It had the slots cut for splitter tunnels, so I did some suuuper quick and dirty splitter ramps out of fiberglass. The quality of them isn't amazing by any means, but it was more a quick and dirty test run to see how well the mold release I had worked. They came out better then I had expected, but I am NOT looking forward to doing this for bigger items, like the bumper/fenders. For now, they will suffice.
Nearly 3 weeks ago I had bought an open 2.73 getrag off of ebay. The seller dicked around for a few weeks, then while I was at Pine decided they didn't actually have this item in stock and canceled my order. Big mad. So I scrambled around some and was able to locate another 2.73 getrag that was at least on the same coast as me, crossed my fingers and hoped it would show up for CMP. And wouldn't yah know it, 3:00 Friday, the day before CMP, look what showed up.
Now you're probably thinking "Wait you have a super nice OSG Getrag, why are you bothering with a shitty open unit?" Great question, and it's something that's given me a LOT of headaches.
For starters, the gearing on the 8HP is suuupper tight. My 1:1 gear is 6th, and while 7 and 8 are overdrive gears, they are not designed to have real load put through them. 1-6th should be limited to 8200 driveshaft RPM, and 7/8th should be keep under 5200 driveshaft RPM, with high load not recommended. I.e, not holding WOT at 150MPH. Failure to do so can result in the transmission literally tearing the rear casing off itself... something about the bearing design, never dug too deep into why. Anyway, all that to say is that the 8HP, for track use, needs to be treated like a 6 speed transmission with a 1:1 final drive.
Add in to this complexity, the 15" wheel, and you can see why a super long diff would be required. In my case, my 3.42 limited me to 138mph, and 1-3 are just spin city, the gearing is so tight. Yeah, it's fun banging 3 gears to go from 30-90mph, but it's probably not the fastest.
"Ok fine, so pull the OSG out of your 3.42 and install it in a 2.73, stop making this so complicated"
Welll.. you can't. To account for the larger pinion in the 2.73, Getrag moved the ring gear location in the casing, close to a half inch. The OSG does not fit, no aftermarket LSD will fit, and the 2.73 never came with a G80 "factory LSD" option. So the longest gearing I can get out of a Getrag with an OSG installed, would be a 3.23. Still faaar too short for my needs.
Originally Posted by Padlock
Time to swap to an 8.8 to get a 2.73........
So... yeah. This will have to happen. The 8.8 can be built with a 2.73 or 3.08, and OSG offers an LSD for them. This does, however, mean I have to cut out all the Getrag mounting, build a new mounting setup for an 8.8, and change both my axle and driveshaft ends. In short, it's gonna be a lot of work and a pain in the ***, not something that happens in a day or two.
ANYWAY, all that to say, I needed a longer diff for track stuff, and throwing an open 2.73 Getrag in was my quickest and least painful option. Everything just bolts up and the diffs are not massively expensive, I think this one was $400 shipped to my door. With the 2.73 6th will top out around 175mph which... umm... would probably be terrifying, but makes 1-3rd much more useable. So for the time being, I'll be swapping diffs depending on if I'm hillclimbing or going to the track(a good diff is worth multiple seconds at several of our tighter hills, so no chance I'm running an open for them).
ANYWAY anyway, diff showed up at 3pm on Friday, threw it into the car, took it for a test drive to confirm it wasn't bad out of the box, loaded up and drove the 4hrs to CMP that night.
4
Mad props, this thing looks like an absolute riot!
