unhealthy "rattle"

Shamrock

Hey,

I had posted previously about a rattle/knock and after tinkering around I think I can describe it better. My car is a 7AT with stillen headers\test pipes and an akropovitch full system exhaust. It was tuned and one of the throttle maps from the forum was added. Basically the rattling occurs at the 2500 to 3000 rpm range and it sounds like it is coming from the engine area. It doesn't always happen but I can always reenact it as follows; semi-hard acceleration in a high gear (five or six) from low rpm (2000 rpm.) Is this knocking, pinging, timing or perhpas nothing? I had been driving for two years without a tune and only with the above parts and I believe this started happening after the tune. My car only has 33000 km and I'd be petrified to think that I have done something that is causing damage to my engine. What say you all? Thanks

bullitt5897

You might want to video record the event. It could be a lot of things... The tone and pitch of the rattle could help determine the issue

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Shop Cars: 2013 318whp Nismo VspecII 370z *SOLD*, 2009 1000hp+ 93oct 4.0L TT 370z Fast Intentions STAGE 4 #054

Shamrock

I really have tried. It can't be heard over the noise inside of the car. What could it be that causes it to happen when the engine is under load at low rpm's? Also while cruising in drive at 2000 rpm when I press the gas pedal to accelerate the rpm's climb and when they hit the area of about 3000 rpm the rattle starts and ends right before the tranny shifts gears.

BGTV8

Get this professional inspected because if this is "knock" then you are doing damage to your engine.

Take it back to the guy who installed the tune if he has a rolling road so you can verify if it is knock, and the then tune it out.

Engine knock or pinging is not called "death rattle" for no reason.

Shamrock

Could a bad tune cause knock?
He has a dyno where he dettaches the rear wheels. Is this a rolling road?

BGTV8

Short answer is yes.

Knock can be caused by too much ignition and adding spark advance and a pulling a bit of fuel to run closer to a true stoic-ratio is the common way of a tune delivering more power. Most OEM setup are very "safe" to cope with global fuel quality variability and vehicle operating conditions - they run fairly conservative spark advance tables to leave a wide safety margin and avoid engine damage warranty claims. What the "tuning" industry does to take your engine closer to the knock limit which will deliver more power.

Too much ignition advance will cause knock - guaranteed.

Using a "hub-dyno" which is what you describe is one form of "rolling road" - it has the benefit of zero tyre slip which can happen with tyres on rollers style of dyno, so yes, a hub-dyno will do the job perfectly well.

Shamrock

Thanks...can the throttle map that I copy/pasted (not connected to the actual tune) cause the knock or is it just the tune. Does my description sound like knock to you? Thanks

Awgd8

Not at all. The best way to isolate the issue is switch to your stock map (stock throttle) and see if you will hear it. I changed my throttle maps maybe 20+ times already when i was learning to tweak the table and never had an issue like you mentioned.

Awgd8

Was it dyno tuned? Are you sure your tuner did not break a thing during the dyno? There is always a risk breaking stuff on the dyno...

BTW, I have a new throttle map design for the 370z let me know if you want to try it?

Shamrock

Please send me the map. My car is an automatic. I think if something was broken I'd hear it through the rev scale and not just at certain revs.

ANMVQ

I had the same noise same gear and RPM last summer after loading in my revised Etune( Different tuner not than Seymore4) It was a timing ping. I had the tuner revised it again. He told me it was something that sometimes happens when the VVEL timing is to advanced. I'd get if fix as soon as you can. Not something you want to be doing to hear the noise over and over. Mine actually threw a CEL light.

The other thing is can be is low oil pressure causing the VVEL to stick. ( Something I read) No clue if its true but makes sense as that gear see oil.

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Shamrock

Let's say it's timing. Could I have caused damage? It only happens at 3000 to 3500 rpm.

Awgd8

While still waiting to be fixed by yor tuner, any chance you can switch to stock map? If not , pump the highest fuel octane available in your area. That low of an RPM should not cause that much knock ir pinging unless timing is too advance. I wonder if there is just loose metal bracket that vibrates at low rpm?

ANMVQ

Yes it can if your doing it over and over again, that's where mine was it would go away in the upper RPM's but do what Awgd8 said till you can get it resolved .

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Shamrock

I am not going to drive it until my tuner gets back from vacation. There are no loose brackets. I checked everything from top to bottom. How can I know if I caused damage? What could the damage be?