Low plastic ramps under the towcar rear wheels FTW! The back-friendly option!!

 

Congrats on the time dude! Getting reffed for “questionable performance” is one of the highest honors you can receive! Assuming your car is class legal lol.

Solid work with the dialing in tire pressures too. Were you checking hot pressures as well? Or is that semi-irrelevant given the lapping format?

 

Yep! That's what I've been using.

Thank you sir. The car is legal. I haven't been to a dyno for a real power figure, but under the rules I'm not required to, and I still estimate it around 130whp but more torque under the curve than the old BP4W. I know the weight is within the rules as well.

I wasn't checking hot pressures because by the time I got to pits they had likely dropped a bit (cooldown+showing the timing folk my run). I really was going by feel, watching the thread wear near the sidewall, and guessing by past experience. Tires pressures are definitely relevant in this format too, I just didn't find a good way to check 'em. Maybe next time I'll pull over right away and have a friend check them.

I have been eyeing one of these for monitoring pressures through the ECU though: https://ecumasterusa.com/products/wh...44631712202993

 

That's pretty cool... but the price!

 

Haha that's why I'm still eyeing, and not buying.

 

My thoughts as well! Haha, have you considered a standalone TPMS unit? Not as cool as interfacing via the ECU but still should get the job done. After my recent experience with the screw on sensors, I'd probably recommend one that utilizes sensors in the valve stems instead.

Either way, I'd imagine you could get the job done for a fraction of the cost of that module. Being able to see hot pressures while on track is a game changer.

 

There is an Aim TPMS product, looks same but a bit cheaper - I only found a UK price though, and it is not compatible with Solo2, so probably not with their low end dashes either as I understand they use the same OS as the Solo2. But it is CAN and I presume there is nothing stopping you feeding that into an ECU ...

I looked at something similar at WTAC last year, c$1500AUD. I think all/most of them use the same hardware, with their own version of the s/w, or maybe it is just a badging exercise?.

 

Thanks for sharing those. They seem pretty cool. I played around with the software and was able to set them up with the Aim MXS v2, so I'm going to assume it would work with any of their dashes that support 2 CAN Buses. There is a way to make them interface with Link, but I need to find a software to convert their CAN protocol binary file to something I can read.

 

Just came across these: https://trailbrake.com/tpms-unlimited/ which provide their CAN protocol as a DBC file for ECUs and XC1 file for AIM dashes. I think these might be the ones for me but need do more research.

 

I wouldn't mind a standalone unit, but if I'm going through the hassle of having the valve stems replaced, I feel I'll do the whole shebang. You experience with the external ones was scary, and until I saw your post I was considering some cheapo external ones too.

 

That looks like the Aim system I found on the Aim UK site, but cheaper, much cheaper! And they are an Aim dealer, they seem to have put their sticker over the Aim one!

 

from what I’m reading on forums, these are all manufactured by one of 3 Chinese companies and sold without a finished firmware? Then it’s up to the supplier (AIM, Haltech, etc) to write the firmware and CAN protocol format

 

You are killing it out there!

The extra shifting of going down to 2nd feels faster because you're doing more things, but you're taxing your brains front side bus, unsettling the car, and wasting time with all the extra shifting.

 

I made some time to get the car on a dyno today.

Tomorrow I'll write a detailed description of all the experimentation we did, but here is a TLDR:
The car made 127whp on the first pull on the dyno. They pumped the air in the tires to 30psi, and then it did 128whp. Some more timing, 130whp. A spec of better VVT tuning, 132whp. Open filter makes more jam but heatsoaked in one run and lost half the gains. Longer trumpets make more jam.




I'll post a video link as soon as it uploads!

 

Final pull with heat soaked open filter.


Part throttle runs to warmup coolant and oil

 

Thank you Ben! I forgot to follow up on this, but I agree about keeping third gear. Final MPH while holding third was 1 to 2mph higher and it helped me focus more on the right line through T3 and T4. Will try again next time now that it has a bit more torque at 4k RPM.

 

The dyno day went splendidly. Trailered the car to a place called Dyno Edge in Albuquerque and everyone there was a proper car nut. They specialize in big power mustangs, but they all liked the ITBs and 3D printed stacks.

The way it worked was that Chris was driving the car and operating the dyno while I handled the laptop. We started with a couple of baseline pulls to see where the street toon stood. First pull it did 127.6 whp. Chris asked about tire pressures which I had left untouched from the track day. He pumped it from 25psi to 30psi and did another 2 pulls, and it made 128.1 and 128.7 whp respectively. We called that a good baseline, and I was surprised how close it was to virtual dyno.



Next he recommended I test running it leaner. The targets at WOT were about 12.5, so we tried tapering from 13.0 to 12.7. It did not like that and lost 1 whp in a few areas, so left it at 12.7@2k RPM, to 12.5 the rest of the way also to hopefully keep the catalyst happy.

Next we played with timing. I was already running a fairly aggressive timing advance considering it was only street tuned, from 25* at 3k up to 28* at 7k RPM on 91 octane. Mostly trusting the knock sensing in Link and knowing at our altitude it is ok to do. So we ran a baseline pull with 24* degrees across the board to verify my knock sensor settings. Then increased a few degrees at a time and watched the change. The spark map I was running pre-dyno actually wasn't too far off from what it wanted, some areas were slightly over, others slightly below. Unfortunately this was not a load-bearing dyno and I couldn't test the part throttle areas, or under 2800 RPM. At this point it was at 131 whp with 50mm stacks and carbon airbox.



Next on the list was VVT. For this I wanted to do various pulls at different angles (0,10,20,30,40), compare them all and decide what angle to use for which RPM. This is somewhat tricky without closed-loop control, as VVT angles directly affect cylinder efficiency and can make the engine run rich or lean enough to remove any power gains. I left the G4X on closed-loop lambda control to help with this and it worked well, with a flat 12.5 across the board. The results were very interesting but nothing groundbreaking. It was just cool to see it happen with my keystrokes. It liked 30* advance at 3800-4300 RPM, tapering down to 0* at 6500 RPM. An interesting portion I didn't expect was that there was no difference between 30 and 40* advance in the peak torque area. I expected closer to 40 to make more power there, but it liked 30 the best. I wonder if longer trumpets might change this somewhat, but I didn't bring the 60mm trumpets. I also wonder if that higher overlap helps turbo spool? At this point it still made 132 peak whp but improved midrange with 2-3 whp higher everywhere under the curve than when we started. Unfortunately I don't seem to have that dyno graph, so you'll have to trust me on that.



At this point I was ecstatic and ready to hop out and stick my ear next to the trumpets. Chris kept mentioning he thought the air box was a restriction, so we put the big filter on and to my surprise it made more power everywhere. Ran it again, and it lost power from heat soak. Ran it again, and it made the same power as the plenum. Heat soak is a bitch. Hearing the induction noise being next to the trumpets was the best part of my day. What a rush! So I'll be running the plenum on the track and filter on the street as I did before.


Airbox vs open filter, and filter vs heatsoak

Lastly I swapped to the 25mm trumpets that Borla sent, and it lost power everywhere except at 7100 RPM. Theory says short trumpets are better at high RPM, but this BP only revs to 7200. This tracks with what I've read from Emilio and Keith, both suggesting longer trumpets, Keith actually told me to run the longest trumpet I can fit. I'm going to reach out to Reverie and ITG to see if I can source a larger internal filter for the airbox because I think the lesser internal area is messing the airflow around the velocity stacks. The big filter has a lot more internal area.


50mm vs 25mm velocity stacks

So that was the end of the dyno tuning. Without a load bearing dyno I wasn't able to do the rest of the spark and VVT map as I wanted, but that's ok. The main goal was to prove Scooter is legal in D class. With 132whp with the plenum and 2430 fighting weight it puts it at 18.4 weight/power, which is D class. Only this time it actually makes 132whp with more power under the curve. I'm excited to drive it around and see how it feels in the hairpins next time on track!

 

Yo, good stuff dude! Super fun to see the changes happen play by play. Is it just me or is tuning N/A more fun because you really gotta work for every horsepower? Lol.

If I remember right, you said you had to be at 130whp or less to stay in class, correct? Or was the figure 130-ish? Either way, solid numbers and I'm glad you picked up some power under the curve!

 

The 130whp makes that 1:32 all the more impressive! Lots of butts being hurt by Ricardo lately!

 

There are calculators/formulas floating around the web for determining runner length. I forget the actual formula but recall it's pretty simple. It's been nearly 10 years ago we put 45mm ITB's on Taxi's 2.0L Whammy engine. After a bunch of measuring we ended up with the absolute longest possible stack we could fit inside of the fenders. The velocity stack and filters are key ingredients and need to be factored in. Made good torque. Filter rubbed the inner fender well.

From what I have seen, virtually every B series ITB build on the interweb uses runners that are like, way too short. Putting second order resonance at like 10,000rpm where there isn't enough cam or head flow to reach. IIRC, Taxi came up maybe 10-15mm short on runner length for the 7500rpm I was targeting. Anyway, here's the plot. The key takeaway is the midrange torque which was huge on this motor. But it still pulled like gangbusters on top.

https://www.miataturbo.net/engine-pe...00whp-n-74903/