1.6 M45 - lose a boost coupling and the engine revs out of control - Miata Turbo Forum - Boost cars, acquire cats.

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Old 03-04-2013, 09:46 AM   #1
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Default 1.6 M45 - lose a boost coupling and the engine revs out of control

I doubt this is a 'new' problem, but I can't find info about it.

I've got an M45/JRSC and MS2. Recently installed the MS2 and working on tuning it.

I was out running the car last night and the coupling right at the S/C outlet blew off. I didn't know that right away but did after I inspected the engine bay. What I did find was that, if I ran the engine, it would rev. I'd cut the ignition before anything really happened, but I believe it would rev right past the limiter and blow the engine.

I'm wondering if it's related to the throttle body being before the S/C. I have lost this coupling before with the stock ECU, but the engine would stumble and not run as opposed to this. I now have a T-bolt clamp on that coupling...

Any advice? Is there a parameter in MS that I can/should adjust for this?

Last edited by mc85; 03-04-2013 at 10:18 AM.
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Old 03-04-2013, 09:57 AM   #2
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Engage your brain. You have a massive leak after the throttling device yes it will be like having a wide open throttle.
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Old 03-04-2013, 09:59 AM   #3
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And there's no way it would rev past the limiter, that's defined by your ECU. As leafy said, think about it.
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Old 03-04-2013, 10:10 AM   #4
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Quote:
Originally Posted by Leafy View Post
Engage your brain. You have a massive leak after the throttling device yes it will be like having a wide open throttle.
Sorry, I didn't mean to say I was concerned about the engine revving. I understand that it's like having the throttle completely open.

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Originally Posted by richyvrlimited View Post
And there's no way it would rev past the limiter, that's defined by your ECU. As leafy said, think about it.
The problem is that the rev limiter does NOT appear to be working. I have it set at 7100 RPM. From what I could see on the tachometer and hear from the engine, it blew right past it before I cut the ignition.

Could it not be reacting fast enough?
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Old 03-04-2013, 10:22 AM   #5
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Quote:
Originally Posted by mc85 View Post
Sorry, I didn't mean to say I was concerned about the engine revving. I understand that it's like having the throttle completely open.
Because there is no throttle when your pipe comes off!

Quote:
The problem is that the rev limiter does NOT appear to be working. I have it set at 7100 RPM. From what I could see on the tachometer and hear from the engine, it blew right past it before I cut the ignition.

Could it not be reacting fast enough?
Tacho on your laptop as reported by your ECU, or the tacho on your dash which is notoriously inaccurate and massively over-reads?

I'm massively impressed you can tell engine RPM by ear too
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Old 03-04-2013, 10:30 AM   #6
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Quote:
Originally Posted by mc85 View Post
Sorry, I didn't mean to say I was concerned about the engine revving. I understand that it's like having the throttle completely open.



The problem is that the rev limiter does NOT appear to be working. I have it set at 7100 RPM. From what I could see on the tachometer and hear from the engine, it blew right past it before I cut the ignition.

Could it not be reacting fast enough?

a 7100 limiter will look like ~8200 on your gauge cluster, because cheapcar.
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Old 03-04-2013, 10:42 AM   #7
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Quote:
Originally Posted by richyvrlimited View Post
Tacho on your laptop as reported by your ECU, or the tacho on your dash which is notoriously inaccurate and massively over-reads?

I'm massively impressed you can tell engine RPM by ear too
Tacho on the dash. I saw it sweeping past 8000-9000 before turning it off. I'm not saying that I was like "hmmm, that sounds like 6502 RPM", more so that it sounded like a shitload of RPM and that I could believe that it was past the limiter.

Quote:
Originally Posted by Braineack View Post
a 7100 limiter will look like ~8200 on your gauge cluster, because cheapcar.
I have hit the limiter since installing the MS, and it was around 7300 or so on the gauge. I can understand if the tacho was overreacting and the REAL RPM was less, but 9000?

There is no reason why the rev limiter would not have worked?
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Old 03-04-2013, 10:47 AM   #8
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I may know from a reliable source that a freshly built "stock" 1.6 will collapse new lifters at around 8400 rpm if you accidentally leave the rev limit at 15,000 RPM and go auto-x. So you didnt make it above that.
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Old 03-04-2013, 12:18 PM   #9
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Thank you and your reliable source.

Thanks guys for the advice this morning. I will assume that the tachometer was way off if 8400RPM would have meant engine failure. I can understand that having the engine running WOT with basically no restriction could cause the tachometer to sweep too fast. Almost seemed too fast for TS to even register it.

I would be tempted to disconnect the coupling and make sure it hits the rev limiter, but probably not. It sure seemed like the thing was past 7100RPM.
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