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Good morning all!
My name is Westley, I recently purchased a "track-prepped" NA8T from another member of the site (dleavitt). My neighbor (Toiyabe) suggested hopping on here for more info on how to address some of my current issues.
The biggest drivability issue I have right now is "rev-hang". In short, the rpm range while driving and in gear seems to lock in place, even when out of gear and stopped. most of the time a quick blip of the throttle pedal will settle it down. I downloaded the appropriate programs to log and view, but soon after starting them i quickly realized I'm in over my head. I come from the diesel VW world and this car is my first gasser. The first thing i noticed when logging was that the computer says 7.5 AFR all the time. The only extra gauge in the car is an AEM AFR and that reads different values. Most driving according to the AEM gauge is in the 12-15 range, sometimes idle will creep up above 18, in which case the gauge shows --. Not sure if directly related, but it is a little concerning. I am attaching two logs which i hope will provide the info that a knowledgeable member seeks. If you want a different log, please let me know. the first log was started while driving, approaching a stop. Notice the rpm - vss - tps relationship. I got out of gear, and slowed the car via brake until the stop, the rpm did not drop until I touched the pedal again. I DO have other tuning related issues with the car, but I don't want to muddy this post up with too many topics.
First log shows the problem pretty well in my opinion, around the 12 second mark I am completely stopped and have been off the throttle for a few seconds, the rpm still hangs.
Second log is a "cold start" (two starts in that one, it typically dies the first time).
Also attached is a list of mods from the previous owner.
Any insight is appreciated, and I will try my best to quickly get whatever additional information is needed.
Happy to be here, and looking forward to becoming proficient in the miata world!
-Westley
Free bump. FWIW, I gave Westley a new wideband sensor to try as I had a spare and I suspected it may be the issue.
Car had been sitting for a bit, but was fine when parked a couple months ago. I was really glad I was able to avoid parting it out, hopefully we can get this figured out.
Hey, I'm actually the original tuner. If I recall correctly, the owner had my shop swap from CAN input to analog, or vise versa, after the same issue. Obviously it left my shop working, but sounds like it's back with the same symptoms. Those being it reading fine on gauge, not reading on MS. He tracked it, so it's entirely possible it's the sensor, however if the gauge seems to be reading accurately, I would look instead into settings and wiring. It's an MS3 basic with the CAN module, if the wideband still goes through it, I would try wiring directly to an analog input and seeing if that helps.
The MS will error out the wideband signal if it's stuck on 7.5, so every EGO/trim setting will be disabled. It'll cause minor issues, but not the idle hang (more below). I would prioritize fixing the wideband, it should have the ability to add a couple percent more fuel in boost if needed (although I'd have to double check the tune to verify this), and that can really help a turbo engine survive long term.
As for the idle hang, again if memory serves me, his particular IAC valve seemed to be very sensitive to changes in the initial value table. Try paying attention to whether its worse cold or hot, and select those regions and decrease them by 1-2% until it returns to idle better. If it starts to stall, you've gone too far.
If this is all over your head a bit, feel free to send me the latest tune (or more than likely I still have it on my laptop), and I can make some changes for you to try. You bought a car I've tuned, so with that comes a certain amount of post-purchase tech support. PM me for my email if you'd like.
Thanks for chiming in Josh! FWIW, I have not made any changes to the tune since you did your work and you've been the only one that has touched the hardware since then. Car was running fine a few weeks ago as far as I know (Westley was the one who drove it last on his test drives).
What I recall on the wideband input is that there was some trouble initially getting the CAN module to talk to the MS correctly. I had it set up when I dropped the car off, but then there was a firmware update that broke things and there was a little work to get things going again. I don't remember ever using the analog input, but that's obviously an easy thing to test. May even be a "permanent" solution if Westley doesn't care about the OBDII output the module supplies.
Thank you all for the replies! I'll dive into this deeper when I get back home this evening. I'll reply again after I know something new. I'm thrilled to have you available Josh! Much obliged, -Westley
UPDATE-I found some time yesterday evening to explore this further. Although I haven't made any software changes yet, the car is now running much better. Ive been messaging josh a little bit about this, along with a newer issue. It has been running very rough, and based on what I described he suggested looking at the plugs.
The wire boots don't actually fit that well, (definitely don't seal against the valve cover) and the two plugs (2&4) that don't have a raised lip on the valve cover had a good amount of water in the recessed area. I am almost positive this is due to the hood vent that's almost directly above the valve cover. Don kept this car inside basically all the time but I do not have this luxury. I plan on making a little something to divert the water that gets in there away from the valve cover area. Along with figuring out how to get the boots to sit right.
The plugs I removed were too hot (bkr5e). Lucky for me; toyiabe was at his shop and gave me some bkr7e's, which I gapped to .22 as Josh suggested. I also changed the wideband sensor while I had the car in the shop. Between the two of those things, it perked right back up. Rev-hang is still an issue but it's able to drive. I'll plug the computer in and look at the AFR today, hoping to see something other than 7.5 across-the-board.
Thank you everyone for all the help. Will update after suggested software changes have been made.
Here's the initial value table I referred to earlier. Once you hook up with the computer, pay attention to what coolant temp you're having the rev hang issue with, and select that ROW. Decrease it by 2% until the rev hang issue is gone. You can see some weirdness I was experiencing with his idle valve, typically the lowest duty you'll see at high temperatures. But once really hot, I was having stalling issues, so I had to add some warmer temps and actually increase duty. Unfortunately it's only a 5x5 table, so there isn't a lot of resolution to play with. I was also targeting a hot idle of 1100, I believe because that's where the vibration from the motor mounts was most tolerable.
05-27-2022, 01:04 PM
New member, NA8 turbo MS Tuning info request.
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