As promised: more minor miscellaneous tuning bits. Couple things with injector settings and manifold runner control tuning.

Ever since installing the ID1050's and loading up the e85 tune, the car has bucked at tip in from zero throttle, and when overrun fuel cut enables. It's also ran super rich, around 11:1, at super low loads. I looked at some logs and saw some strange behavior. At super low load, fuel trims pull as much fuel as possible, up to 30%, but the lowest pulse width would go was 0.8ms. Went through some of the settings and sure enough the default minimum pulse width setting in ECUtek is 0.8ms. The ID1050's sport a minimum pulse width of 0.3ms, so I punched that in and boom, no more bucking or uber-richness at minimum loads. A small win, but a win! For reference, the car idles at 1.1-1.2ms and WOT pulse width peaks at ~6.8ms. The stock injectors definitely wouldn't get close to 0.8ms anywhere, but these are over triple the size so... yeah I guess that's to be expected. I haven't gone back to my supplied 91 octane tune but I assume this is why it was running almost too rich to even idle when I loaded it up.

Continuing on, this car's had a power dip from about 4.8k to 5.3k rpm since I put the 2.5L in it. Not perceivable via the butt dyno, but it was pretty obvious on the dyno sheet and the Aim data shows my other 2.5 NC buddies pulling away from me in areas right at that rpm (turn 2 at WSIR is full throttle at ~5k rpm for upwards of 10 seconds).


Power dip shown on a soggy dyno sheet.

I was reading some threads in the ROMdrop forum about experimentation with different intake manifold runner control opening values. The stock NC will enable the long runners at WOT from 3,250 to 4,750RPM, then switch back to short runners above that. Bigger motor and cams ought to change the ideal transition point, right? That seems to be the general consensus. I wonder where my transition point is set...

Bingo! Probably.



So the top highlighted line is engine load expressed as g/rev. Larger number equals more cylinder fill per revolution equals more torque. The bottom row where the IMRC control changes from "2" to "0" is where the intake manifold runners transition from long runners to short. Right as they close at 4,800rpm, there's a significant drop off in engine load, which doesn't recover until about 5.4k rpm. This is also reflected in the load scaling table and required injector pulse width to keep fueling around 12.7:1. I'm pretty sure my previous tune left the runner control transition point at the default value. I hit up my buddy Frankie for a WOT log and his showed the transition point at about 5,600rpm. Noteworthy, as his dyno sheet doesn't show the power dip I have, and we have nearly the exact same profile cams. Both dyno runs were done on a Dynojet (and I believe the same smoothing factor?) and our peak horsepower numbers are within 1whp of each other.

Next step will be to change the IMRC transition to ~5,300rpm and see if the engine load drop still occurs or not. I'm pretty confident that should eliminate the power dip but I'll do some modifications and logs tonight or tomorrow and confirm.

 

Threads like this remind me of the Good Old Days™ of Miataturbo.net and it brings me joy.

Takes me back to the days when I was clueless about everything, cuz I'm still clueless about this stuff

 

Annnnnd these kinda details are why I don't rely on predone, canned and locked tunes. Tuners dealing with a dozen different cars at any given time miss these kind of things or simply don't have/dedicate the time past "it hits the AFR target in 90% of the WOT cells and makes appropriate power, good enough."

Gimmi the ability to **** with, and correct my own tunes, 100% of the time, every time.

Also Ecutec table logic hurts my brain... But I'm so used to my kPa/RPM tables.

 

I wasn't there for the glory days, but I'm definitely getting deja vu from learning on my old Megasquirt. Lots of "WTF"'s followed much later by a few "Ahhh, ok"'s.
I also know nothing about this stuff. Started reading up on it all the way back in November and I'm just now at the point of being comfortable tweaking with my own car.

Yeah, I thought I was doing myself a favor by outsourcing the tuning on this thing. I was wrong. Not gonna claim I'm anything but an amateur but it's so nice being able to make adjustments myself again. That's absolutely it, there's just no way to get this stuff absolutely dialed without a certain amount of time devoted to it.

And yeah, it still looks weird to me too. There's a speed density option but I wanted to at least take a stab at using the factory logic first. Something about trying new things and getting smarter and more well-rounded or something...

Switched the IMRC crossover from 4,750 to 5,300 tonight and did some back to back pulls with both variations. Keeping the long runners active later seemed to increase cylinder fill up to around 5k. From 5-5.3k, it wasn't obvious if the long or short runners resulted in a higher load reading. Regardless, the load dip starting at 4,700 was still present with the long runners active, so I don't think it's a runner control issue. Maybe a result of my intake/cam/exhaust combination. Either way, the car picked up a miniscule amount of power between 4.7 and 5k, so I'm taking it as a win.



Above is the load drop noticed between 4.7-5k rpm with the short runners enabled above 4.7k rpm.



And here's the load numbers with the short runners enabled above 5.3k rpm. I took a couple logs with each setting and they both seem to track. Higher load values from 4.7 to 5k, but no real discernable difference above that. Can't feel it in the butt dyno, but I'll take every horsepower I can weasel out of this silly little car.

Also of note, the car definitely isn't out of fuel pump yet like I previously suspected. The fuel system's able to hold 12.7:1 all the way to redline at WOT. I noticed the previous tuner and I have arrived at fueling via very different methods. My current tune reads around 130g/s from the MAF sensor at WOT/redline whereas the previous tune would read up to 200g/s in the same scenario. Again, I'm not an expert here, but my fuel tracking seems to be working as is. Just an interesting tidbit.

 

What was always described as a learning curve has always appeared more like stair steps of leaps forward to me. Also reminded of learning megasquirt from your descriptions. Kind of sounds fun and interesting.

 

Cool to see you flying on track w/ this thing Zak! Impressive your pace at modding/hitting events hasn't slowed a bit! Awesome to see man.

Ya I completely agree on tuning cars. It just takes time/tedious work to get things really dialed in that most "tuners" simply can't/don't spend that much time with.

 

I need to unsubscribe from this thread or sort it to spam. Y'all are blowing up my inbox.

Glad to see your tuning experience is going well! Makes me want to dive back into an aftermarket ECU. I didn't realize the NC had a two stage intake manifold similar to the NB1. I've really been sleeping on NCs too much.

 

100%. I remember having the same experience with the Megasquirt too. Lots of head scratching for a long time and then one day you'd try something and lots of things would just click into place.

Yo, thanks Teg! I can't sit for too long or the voices in my head will start getting louder.

Yeah, sorry, I could probably slow down on posting here. I just keep getting really excited about all this stuff lol.

-----------------------------------------------------------------------------------------------------------------------------------------

I set the IMRC crossover to 5,100 last night and took another couple datalogs this morning on the way to work. Looks like 5-5.1k is where the engine wants the switch to short runners. Datalog shows load readings are still higher than before from 4.7-5k still so I'm going to leave the crossover at 5.1k for now. Probably only good for 2-3whp in that range, but I'm gonna call it a win.



Also this happened today. Kraken just dropped their complete NC top mount/ewg kit. And it's a f*cking steal. I'm going to close my browser before I make a bad decision.

 

Good stuff Zak! Got me looking into NC tuning now. I’m pleasantly surprised that RomDrop uses the same software and cable as I use with the Stealth (ECUFlash).

Keep it NA and keep having fun with your close running pack!

 

No no no, I was only joking about the emails! It's nice to have fast conversations on an active forum, and not just generic social media like Facebook. I wish my build threads were this fast paced!

Here's another vote for keeping it N/A. You've got a great group to fight for #1 with, that's a lot more fun than only trying to beat your own lap time when no one else has a comparable car!

 

Vote #3 here for staying N/A. It's more rewarding hurting feelings when people don't see a power adder under your hood

 

That's offensively cheap. Good for people who wanna turbo their NC for cheap, but a very questionable business decision on his end. Guy needs to charge enough to secure a future, wacky to sell this cheap.

 

As much as I'd LOVE to see this build spiral out of control into a full high horsepower unlimited T/A build, I'll 4'th keeping it NA.

Personally, I ended up with another miata (yea a 3rd one) recently that will be taking the super basic N/A track approach. The turbo car punches way above its weight level but there's something to be said about a cheap(ish) n/a car that can be thrashed endlessly and you can just focus on driver development. And even more so now that you are running with a tight pack of evenly matched friends. I certainly won't speak for anyone else, but for me I think my driving skills would really benefit being in a slower car for a while.

Maybe you need a 2nd NC for a turbo street car build?

 

This is the way.

 

Ya wow that Kraken NC turbo kit is insanely cheap (my NB kit was damn cheap as well). Not sure how he makes money, labor costs must be quite cheap in Bulgaria..?
What do I think you should do? I vote turbo because when is more power worse (it's not my money afterall )?? The simple truth is more power is better than less power. It would make for a very entertaining build.

Fixed that.

 

Man what the hell guys, I thought this was MiataTURBO.net! I thought you guys were my homies. More of you should be encouraging me to make bad decisions

I kid, I kid. Yeah, I think the general consensus is right. Reliability (and the resulting increase in seat time) trumps all for most of us. Even if I could get more power with this turbo kit for barely over half the cost of a 260WHP 2.4L Duratec...

That's what caught my eye. If the kit were similar in cost to the $5k Fab9 EFR kit, I wouldn't have batted an eye. The cost of the kit is just nuts. I could buy the kit with a full exhaust, sell my current exhaust for a profit (even keeping my header) and use the extra money to buy a backup 2.5L in case the worst happens. I think that's really what got the wheels turning

I'll third that this is the way. Only problem is that space in Orange County is at a premium and I don't have space in the garage for any more cars. Now if I could just get my roommate to ditch his Jeep that he never drives...

 

I am here to provide solutions to your problems.

 

Hey, I told you to buy a whole 'nother car and turbo that! Trust me, I'm here for you.

But all seriousness, we've all been through the mt.net cycle of life around here, and embrace the dead reliable n/a track car.

 

Have all the cats for that one. Having a job where I'm around lifts all day, that solution should've occurred to me lol.

Agreed about the circle of life haha. I guess you could say I've already done a round of that before. Alright yeah, I'll get my head on straight and fight the urge to make transmission-liquifying torque here in the meantime.



Backup engine procured. 111k miles on this one. It'll sit as a reserve until the end of Summer if needed, then likely get torn down in preparation for a high comp 2.4L build after that.

 

It's hilarious how cheap those motors are. I just spent that much in brake pads