Rev-built MS3 cut off at 4k - Miata Turbo Forum - Boost cars, acquire cats.

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Old 02-13-2015, 03:17 PM   #1
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Default Rev-built MS3 cut off at 4k

Guys,

Just installed my MS3, went for a test drive and i am hitting what feels like like a fuel/rev limiter cut off at 4000 rpms. I am using Rev's supplied base map, I'm still N/A until I feel comfortable with it. I don't have any real experience with tunerstudio yet, attached is a log. please advice

Thanks,

Dan
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File Type: msl FIRSTLOG.msl (450.8 KB, 45 views)
File Type: msl 2log.msl (1.31 MB, 35 views)
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Old 02-13-2015, 03:20 PM   #2
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what is the rev limit set to?
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Old 02-13-2015, 03:24 PM   #3
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7000
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Old 02-13-2015, 03:27 PM   #4
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check fuel and ignition cuts as well. posting your msq would be helpful too
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Old 02-13-2015, 03:29 PM   #5
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so there is only hard cut at 7k and not progressive cut or spark cut or fuel cut that might be set at 4k?

disable all of them and try again
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Old 02-13-2015, 04:46 PM   #6
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thanks for the replies, was driving around trying to figure it. The launch in was set and it was cutting it to 4k... turn it off and seems ok now. time to learn some more
Thanks all
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Old 02-20-2015, 11:51 AM   #7
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Just for reference in case other folks with similar symptoms look at this thread:

I had a similar issue when I first got my MS (stock engine, no turbo). The engine was VVT, but the MS was not controlling the VVT. I was using a base map from Rev, hadn't made any changes to it yet. It would rev up to about 4000 rpms and then seemed to struggle a lot to get above that. I noticed that the AFRs were going crazy rich, so I just started pulling fuel in that area, and after pulling quite a lot of fuel, it finally was able to rev past 4000.

My theory on why this happened is as follows:

Since it's a VVT engine, it's designed to use the VVT to help increase the efficiency lower in the rpm range. When the VVT is not working, it operates pretty inefficiently until about 5500, where the engine is designed to have max torque. At that point, the various physical/geometric and timing characteristics of the engine converge together, and there's a sudden jump in the volumetric efficiency of the engine.

If you're using a standard base map, the VE table tends to increase at a much more gradual rate, so by the time it gets around 4000 rpms, it's putting way too much fuel in for the engine to use, which causes it to struggle. When I finally got mine to rev all the way through the rpm range, I had this crazy jump in the VE table between like 5300 and 5500 rpms. It increased very little between about 2500 and 5000, and then the VE table almost doubled between 5300 and 5500, and then increased at a reasonable rate the rest of the way to 7300.

That's my theory anyway.

I just thought I would put this here, in case anybody with an issue similar to mine looks at this thread, since the symptoms are very similar.

Cheers!
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Old 02-20-2015, 12:03 PM   #8
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Nevermind I see you solved it. Read failure.
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Old 02-20-2015, 12:41 PM   #9
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Quote:
Originally Posted by Engi-ninja View Post
Just for reference in case other folks with similar symptoms look at this thread:

I had a similar issue when I first got my MS (stock engine, no turbo). The engine was VVT, but the MS was not controlling the VVT. I was using a base map from Rev, hadn't made any changes to it yet. It would rev up to about 4000 rpms and then seemed to struggle a lot to get above that. I noticed that the AFRs were going crazy rich, so I just started pulling fuel in that area, and after pulling quite a lot of fuel, it finally was able to rev past 4000.

My theory on why this happened is as follows:

Since it's a VVT engine, it's designed to use the VVT to help increase the efficiency lower in the rpm range. When the VVT is not working, it operates pretty inefficiently until about 5500, where the engine is designed to have max torque. At that point, the various physical/geometric and timing characteristics of the engine converge together, and there's a sudden jump in the volumetric efficiency of the engine.

If you're using a standard base map, the VE table tends to increase at a much more gradual rate, so by the time it gets around 4000 rpms, it's putting way too much fuel in for the engine to use, which causes it to struggle. When I finally got mine to rev all the way through the rpm range, I had this crazy jump in the VE table between like 5300 and 5500 rpms. It increased very little between about 2500 and 5000, and then the VE table almost doubled between 5300 and 5500, and then increased at a reasonable rate the rest of the way to 7300.

That's my theory anyway.

I just thought I would put this here, in case anybody with an issue similar to mine looks at this thread, since the symptoms are very similar.

Cheers!
no.
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Old 02-20-2015, 01:31 PM   #10
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No? Could you please elaborate?
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Old 02-20-2015, 01:50 PM   #11
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I guess it doesn't make sense to say that putting too much fuel keeps the engine from accelerating, but it definitely seemed like that's what the issues was. The AFRs were very rich when it wouldn't accelerate, and then they became reasonable after I had pulled the fuel. What would cause it to behave like that?
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Old 02-20-2015, 01:52 PM   #12
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Quote:
Originally Posted by Engi-ninja View Post
No? Could you please elaborate?
Your 'fuel theory' is not relevant to this discussion.
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Old 02-20-2015, 02:15 PM   #13
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Ah, I see. Ok, my apologies.
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Old 02-20-2015, 04:07 PM   #14
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or the answer to your issue.
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Old 02-20-2015, 04:16 PM   #15
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his comment about the VE table jumping at 53-55 on an nb2 is pretty acurate.

but the rest I just ignored lol
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Old 02-20-2015, 04:30 PM   #16
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Ok, well thanks for pointing out that I'm wrong. I'll be sure to keep it in mind for the future.
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Old 02-20-2015, 04:53 PM   #17
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I did a little testing with vvt too, the difference between advance vs retard was something like .5-.9 points AFR in the lower rpm range. up top didn't matter at all
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