3.6 conversion motor question
 

My 3.6 swap is working out well but at low rpms - 1000 to about 2500 I hear a faint buzzing, rattling, sound like marbles in a can - especially in 2nd gear. I thought it was pinging but if I lug the motor in 4th at a low speed the sound is barley there. Could it be pinging? Any way to check the knock sensors?
Thanks,
Manny
P.S. it is a hard noise to describe and is not evident with the car rooling or by just hitting the gas - it almost sounds like it is there throughout the rev range but as the exhaust gets louder you cannot hear it as the revs go up.

You sure it's not just the transmission rattling away?

It is quite possible - iit doesn't sound like pinging but I would like to be sure. Is there any way to confirm if it is the tranny - it almost sounds like a buzzing - an even sound that does not change no matter if I floor it or accelerate slowly.

Where is the sound coming from? Have you gotten out of your car and checked?

My starter always buzzes.

It sounds like it is coming from the engine compartment but you only hear it when the car is moving, not at idle. I may have to get someone to drive away while I stand next to it and jog behind it to see if it is noticable - the only problem is the exhaust is really loud and you don't hear much else from outside the car.

As you begin to accelerate, depress the clutch and see if the sound goes away consistent with disengagement. My guess is that you're hearing your clutch/tranny, etc., under load at low rpm's. Perfectly normal regardless of engine type.

Ok, I will give it a try - thanks!

You need to find a concrete wall that you can drive close to on the drivers side. After that, I would try and drive it with the engine as cold as possible next to the wall, and then to the other extreme with the car as hot as possible.
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Another idea is driving up a very steep hill when you have the engine good and hot.
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I don't know what type of chip you have but if you have a Cyntex chip, you have no adaptive KNOCK control. Your knock sensors are now useless weight. Which to me is unreal, but I chock it up to just another chump selling junk to chumps.
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Because of the high compression of these engines, a slight exhaust / header leak can easily mask itself as something else.
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Lastly, make sure nothing is loose like a bolt with a washer clanging on it, rattling engine tin, a chunk of weld in the muffler etc. All of these things can really take on the characteristics of a predictable mechanical problem because you may only hear the noise at a certain speed or RPM range, which may correspond with that chunk of weld rattling in the exhaust! Ask me how I know!!

Todd

I forgot, the 915 tranny rattle noise is usually more noticeable with the tranny good and warm setting in neutral with your foot OFF of the clutch. I have heard freshly and properly rebuilt 915's that sound like they are falling apart when setting in neutral!

Becareful Todd, the Cyntex chips do use the knock sensors.

prove it...talk is cheap.

Cybtex chips for the 964 do use the knock sensors. Proof is that the software is identical to the stock chip when you do a binary comparison.

Ingo

So for the 964, why not just use a stock chip?

A good performance chip has slightly modified part throttle and full throttle maps (lookup tables) for ignition and fuel while it maintains the stock executable code. It gains you a little bit more power (17 HP) if the gas you are using and the conditions (ambient temps) do not set off the knock sensor retart function. Furthermore it might raise the cut-off RPM value for fuel with the idle switch engaged. This helps the stalling issue with ligher flywheels.

If you decode different chips it is easy to tell what has been modified. Once someone tampers with the code or the base values it gets nasty. Advancing the timing moderatly and allowing for more fuel is fine as long as the knock-induced retard function can still retard enough to prevent knocking.