Knocking when cold
#1
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If you have ever driven a miata with VVT this will be a bit easier to explain, but here I go:
When I normally cold accelerate with the stock ECU with constant throttle, it is a little sluggish until it hits like 3500 and then it jumps. I believe this has something to do with the VVT system, but I may be wrong.
With the MS cold accelerating under constant throttle, I hear what I believe is knock until it gets to that same point around 3500 and it seems to stop knocking.
Now to make it even more strange, I only hear the knock when it is cold. I used to run a more advanced spark table (knocked at cold and fine when hot), which felt really great, and now I am running a retarded 96-97mspnp map, which is more conservative before retard, it still knocks cold and feels slower hot.
Any ideas? I want to be able to run the advanced timing, but not at the cost of knock...
edit: I drive a 2001 for the record.
When I normally cold accelerate with the stock ECU with constant throttle, it is a little sluggish until it hits like 3500 and then it jumps. I believe this has something to do with the VVT system, but I may be wrong.
With the MS cold accelerating under constant throttle, I hear what I believe is knock until it gets to that same point around 3500 and it seems to stop knocking.
Now to make it even more strange, I only hear the knock when it is cold. I used to run a more advanced spark table (knocked at cold and fine when hot), which felt really great, and now I am running a retarded 96-97mspnp map, which is more conservative before retard, it still knocks cold and feels slower hot.
Any ideas? I want to be able to run the advanced timing, but not at the cost of knock...
edit: I drive a 2001 for the record.
Last edited by compy; 05-09-2008 at 12:05 AM. Reason: more info
#3
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Your timing map looks pretty conservative to me. But since it's only doing this cold, and not hot, I think we can ignore that table. Is it possible that you may inadvertently have some ludicrously high numbers in IAT/Clt Related Ignition?
You're absolutely certain this is detonation, and not some mechanical noise? Hell, my transmission pings when it's cold and I'm accelerating below about 2,500 RPM in 3'rd.
You're absolutely certain this is detonation, and not some mechanical noise? Hell, my transmission pings when it's cold and I'm accelerating below about 2,500 RPM in 3'rd.
#6
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Turned it off and still had same knock result. I'm pretty sure what I am hearing is knock. Seems to get louder with RPMs. Symptom of knock? The pretty concrete reason I think it is knock is because it never happened until MS started doing timing.
Maybe I can erase the "add degrees" and jack up the ignition retard and make it so it retards the timing while car is cold.
It is just so strange to me that it goes away once it warms up. I would figure if it was too advanced cold, it would be too advanced hot. It certainly is getting enough fuel since it has the warmup enrichments and such adding fuel while its cold.
Maybe I can erase the "add degrees" and jack up the ignition retard and make it so it retards the timing while car is cold.
It is just so strange to me that it goes away once it warms up. I would figure if it was too advanced cold, it would be too advanced hot. It certainly is getting enough fuel since it has the warmup enrichments and such adding fuel while its cold.
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find the VTCS solenoid and un plug it. it's the small valve with the vac line on the intake manifold near the firewall... not the EGR, the small one. unplug that when the car is cold and try driving it and see how it is.
#17
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hard to say. try blowing through your nose with it plugged and tell me what the noise is--cuz that's about what was going on. the VTCS butterflies were closed and obstructing flow.
#20
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Do they only stay closed when cold then since the issue goes away when warmed up? It's just weird to me that switching over the timing made the issue develop. I would think the stock ECU would still do it's job of opening and closing them. If it isn't knock that I hear then it wouldn't bother me that they do not work, but I don't want to damage my engine. I had to send my knocksense back to be repaired, so I'll have to wait until I get it back to confirm it. I'm surprised nobody else has had this issue (and resolution) with the megasquirt.
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