poormxdad

Gentlemen,

I was at Dominion Raceway yesterday. The car was a beast. I was near a personal best on R-S4s that I had made on NT01s. On the back section after clearing the last right-hander on the Big Esses, I stabbed the throttle and the car went GrGrGrGrGr. I believe that happens ~1753 seconds into the log. I did the "WTF was that", thought at first I was out of gas--it didn't feel like the supercharger belt was slipping--but when the gauge settled, I saw I had plenty of fuel. I decided to make another lap and see if I could recreate the problem. I believe it happens again at ~1849 secs and again at ~1863 secs. Otherwise, the car runs fine.
The log doesn't show any CEL codes, and there was no loss of sync. It didn't buck like the cam position sensor had failed, it just seemed to not want to rev any higher.
Any assistance would be greatly appreciated.

poormxdad

I've been looking at the log, and the video of the session. I was consistently in the 1:37s, so in the log, I'm in roughly the same place on track every 100 seconds or so. I had a pretty good lap going, but I screwed up Turn 6 and took a breath. I got back into it after Turn 7, but consequently entered the Esses about five mph slower/400 rpm lower than previous laps. However, TPS, Fuel Flow, Boost, and Load were all about the same anyway. When I jumped on the throttle, boost went up, fuel flow started to increase, but rpms didn't, so I backed off.

Again, any words of wit would be greatly appreciated.

poormxdad

At 1863 secs, I go WOT again. However, this time when the GrGrGrGr occurs, I lift a little. The rpms continue to climb, as does boost and fuel flow. That seems to rule out the fuel pump. The throttle body seems fine. The butterfly is not loose. The TPS readings in the log seem normal.

I'd take any educated guess as to where to start troubleshooting.

curly

iTrader: (25)

Looks like ignition issue to me. Check out the screen shot below from ~800 seconds. You're full throttle (purple line), but RPM has a couple bobbles in it, which is usually a misfire or crank sensor issue. I'd recommend replacing the plugs with NGK BKR-7E, gapped to .025", then retest.

Please also note, the yellow line is your AFR target, you're at 8psi targeting 12.1, which is already too lean for my tastes, ESPECIALLY on track, but the green line stays above target at 12.2. Mean while, EGO (yellow line 2nd graph) has reacted as fast as the sloth from Zootopia, having pulled as much as .2% from your base fuel after your shift, but it's graciously added .1 back after a second or so. This .1% change would theoretically take your 12.2afr and change it to ~12.19. So you have multiple issues going on here, EGO isn't acting fast enough, fuel table isn't rich enough, and targets aren't rich enough.

Idle is also a little wild, hunting between 830 and 950. Increase your idle ignition correction by a factor of 10 and turn it on with CL idle activation to help control this.

Ignition table is a little weird too, you could probably increase timing between 90 and 120, and should probably decrease it more above that. Your table sits at 19-20 degrees from 3-9psi. Typically I drop at least a degree of timing per psi of boost.

poormxdad

Curly,

Thanks for chiming in and being so thorough.

A quick visual of the engine at the track didn't reveal anything out of the ordinary, so I had hoped a review of the log would tell me what was wrong. I was already at the end of my planned track time, so I packed up and went home during a more agreeable time for I-95 traffic rather than screw around with the car. I didn't have a chance to actually mess with her until yesterday. She had lost both nuts and one of bolts that holds the coil for cyls 1 and 4 to the coil pack frame. It was literally being held up by the stiction from the two plug wires, both of which had started to slip out. There was a little bit of arcing crud present in the 1 and 4 plug towers. I cleaned the coils and plug wire connectors. I had a couple of the OEM bolts and nuts in my box of stuff at the house, so I'm calling it fixed. However, I have not driven her yet since the repair.

I confirmed that the boost portion of the AFR Table is the same as that for the 99-00 Miata from the Trubokitty website. I changed anything that was leaner than stoich in the table when I started trailering her to the track. I would be happy to take any recommendation from you for changes.

I've been running that spark table for years, but haven't changed it for an increase in boost of a couple of pounds. I told the tuner I wanted a conservative spark map that would allow me to run for an hour in the middle of July--I wasn't interested in making maximum horsepower. The only thing I've done to it was change the left side to account for being in the wrong gear while towing. Again, I would be willing to make changes based on your recommendations, but here I'd need something more specific.

Tuning idle has been problematic for me since adding the Rotrex and the big injectors. I tuned the idle boxes for when she's warmed up and heat soaked in the summer, and I get a very rich idle from those same numbers when the temps are cooler and the engine is cold. I created a 32 kPa row, which is where she tends to idle at, and a 900 rpm column where I'd "like" her to be. I'm fairly certain the idle is rough due to an adjacent box needing tweaking. I have no WUE. When she's cold, she'll idle up in the 13s, and I have EGO take care of it after 135 degrees coolant temp. If the temps are below 40 or so, she'll start up in the 12s. I know when it's cold out that she won't start during the first crank, but will on the second try. I've accepted it as imperfect, but don't worry too much about it now that I have a trailer.

I don't know how to fix the speed EGO reacts, but I do believe it reacts slower when using the separate authority tables rather than a controller authority percentage. I wanted to give EGO the authority to add a shitload of fuel if it thought necessary, but not remove a shitload. I believe the only way to do that is with the tables.

Thanks again,

LeoNA

I would adjust the RPM lag factor down from 95 to 50-70. You might also try a more aggressive RPM timing correction and raising the idle to 950.

curly

iTrader: (25)

So I typically start the above map at +10/-10 degrees for -100/+100rpm delta, and go even further above/below that, adding/subtracting another couple degrees by 200 and 300 degrees delta. Base around 18, so a couple degrees above where you're at.

EGO reaction isn't affected by authority tables, that's only the max percentage it's able to change before stopping. Typically in boost it's a big number at idle, like 10 or 15%, getting smaller with boost or high rpm. I'm typically +5% in boost, -2-3%. You can add up to 20% in boost currently, which is scary. If you have a sensor fail and it dumps an extra 20%, you'll be replacing your o2 sensor and your plugs.

What you want to tune is your PID settings. You're currently at 15/35/5, try 40/20/0. Your ignition events/step is also at 4. That means while idling at 1000rpm/min, EGO will adjust up to 250 times/min. I'd recommend turning that down to 20-30.

There are a lot of videos out there on how to tune PID controllers, they theoretically should behave identically, but none of them do. But each term affects how EGO adjusts differently. Each change can be observed at idle to see if it's oscillating too much or not enough, but that's a single RPM. You really want to log a session like you did above, and make sure it's not swinging wildly when RPM is also changing. Start by lowering those targets like I mentioned earlier though!

You're supercharged? I typically don't target leaner than 14 at idle for superchargers, the pulsing from the constantly rotating impellers causes instability for whatever reason. It's been a minute since I've tuned a rotrex, but try targeting 14 or 13.5 at idle, see if that helps stabilize it if any of the above doesn't work.

poormxdad

Gents,
Thanks much. Have a couple of cats.