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I just encountered a new problem with my 1996 1.8l turbo miata.
At around 5-7 psi, or normally in the ranges of 4-5k rpm it sounds like i'm hitting a rev limiter. Im guessing that it is misfiring. I have changed plugs and re-gapped them. I just changed the wires too. It cant be the tune because i haven't changed anything. I am aware my fueling is all over the place, not sure about the lean spikes, but this is a newly tuned car. Go easy im new.
What are your AFRs under boost? looking at this it seems like they're in the 10s which might cause blowout on the stock ignition set up. I'm not 100% sure if this would be it but it is something that looks wrong. I'm currently at work so I cannot look right now, but a datalog would be useful to look at. That or at least position the cursor better to where we can see the AFRs under boost.
With my flowforce R8 coils (which are a lot stronger) and stock plug gaps (0.4ish iirc) I saw blowout in the 9.5:1 territory when dialing in my new engine and it sounds very similar to what you are describing. I'd target at least AFRs of 11.5:1, and for 6-9psi that would still be very conservative at that little amount of boost.
Also, I did some snooping on your other post. One tip when using the autotune feature is to create a custom filter using "TPSdot > 5, TPSdot < -5". I'm not sure if that's the proper syntax but what you're wanting to do is filter out the transient moments as that will require different amounts of fuel than "steady state conditions" (aka constant throttle, constant MAP). If your tps signal is noisy increase that number to the biggest variation. Mine is not noisy at all so I can get away with 5 TPSdot.
Thank you for the tip. I tried plugging in that custom filter, but it its giving me errors. My AFR's do seem to be very rich when the problem is occurring, 10;1 - 10.5:1. Could that be it? How could I go about tuning that area of my VE, efficiently. The auto tune feature seems to be adding a bunch of fuel in these high boost areas, is that correct? Does this seem right? Thank you.
Here are my AE setting as well if anyone wants to take a good look at them and help me out.
misfire reads as lean, autotune will respond by adding fuel. your VE table (VE% as low as 10% and as high as 134%) is EXTREMELY suspect. Turn on Incorporate AFR, confirm req-fuel/dead-time and get those safe-ish to screw-up areas under 4kRPM and 100kpa into a more appropriate range (50-80%)
I did all of those things and autotune still wants my VE table to look like that. Could it be my injectors? I have no idea what my dead times should be, im just using the base tune injector characteristics. Also in terms of tuning, should I just let the auto tune do its thing while its misfiring like crazy above like 135kpa. It seems to pull fine under around 20-30% throttle, once i give it more it just starts to misfire like crazy. Im wondering if I should go back to a base VE table and start from there with the correct req-fuel/deadtimes. Because my fueling is all over the place.
Attaching the data log to the post is much more convenient for us than posting a momentary chart export .png, since we can then scrub through and get a better idea of the trends.
The IAT correction is very wrong and probably explains why your VE minimum is at 10. There should not be a 1.67x fuel multiplier at 68 degrees, and that multiplier certainly shouldn't increase as IATs go up. Revert it back to whatever was there at the start or look up the graph that is based on the ideal gas law.
That VE table is cursed and needs to be addressed before applying accel enrichment. Take a look at some youtube vids that will guide you through the process of establishing a table on the road. Autotune is good for finding trends in the table, but it's not reliable enough to be tasked with generating the table on its own.
I'm seeing in the log image that your injector duty is reaching 86%. In your Settings>Injector Characteristics you have the safe cut set to 90%. This could be causing a cut under boost, which is where your duty will be the highest. On the topic of duty cycle though, 86% is pretty high on 650cc injectors at only 8-10 psi, though I have a feeling that will be resolved once you get your AFRs closer to target. Additionally, a 1:1 FPR is a fantastic investment for boosted cars.
05-18-2023, 12:01 AM
Is this spark blow-out???
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