metallic rattling noise on 4th gear accelerating
 

Hello all, this is my first thread/query in this forum and hope you can help.
Facing the problem of metallic rattling noise on 4th gear when stepping on the gas, especially when car is at 60-80 km/h.
Have read several similar threads in the tech forum but have not really seen a clear cut finding of cause/solution.
Noise seems to come from just beneath the console towards the front.
Could be transmission or engine but frankly not sure.
But definitely central and not to right or left.
Please help if you can, thanks.
ps. model is RX-8, 5MT

Hi drphy68,

If your 8 has a 5 speed manual, does it also have the lower power engine? As you use km/h, what country do live in and what is the octane rating of gasoline? Ths could be interesting as I have noticed the exact same noise on the North American 6 speed high power. Have you noticed any misfiring or hesitation accelerating above 5000 revs - this is related but I want to be sure we are talking about the same thing:)

Thanks for the resopnse.
The RX8 I have is a Japanese Domestic Model (JDM) 5 Manual Transmission rated at 210 bhp.
I run it in Sinagapore (environment temp 28-32 celcius, humid) using RON98 unleaded petrol.
(Read elsewhere in the forum that: US premium octane 91 is equivalent to RON96).
The metallic rattling noise on 4th gear when stepping on the gas from 60-80 km/h comes on consistently since day 1.
It is so correlated to the gear used, travelling speed and gas stepping (no noise on cruising) that I have excluded engine knocking or misfiring.
Have not experienced misfiring or hesitation accelerating above 5000 revs also.

I believe I have the same noise. I've also noticed it from the first day I had the car. It happens in 4th and 5th gears when I press on the gas - mine's a 6-speed. There's never been any hesitation or any other mechanical problem with the car so far - over 6000 miles. I've always used 93 octane gas.

I've just gotten used to it and don't notice it any more. I have no idea what it is.

hi loco4rx8,
did u approach Mazda US,
n did they have others with same issue?

To be honest with you, I've never mentioned it to Mazda. Since the car has no other symptoms, I just figured that's the way it sounds.

The (second hand) info I have from Mazda is for 2 differnt noises. In the US some 6 speed transmissions make a noise most noticable at idle. The other noise during acceleration while driving is thought to be from ignition timing and gasoline combustion. Canzoomer has a thread in this forum (discussion area) about an ignition reset procedure. This may not apply to the JDM cars.

Thanks for the info drphy68. Does your 98 RON gas contain methanol or ethanol? The Mazda tech I talked to thought this can be a factor if the content is excessive as it effects burning time and ignition advance. Where I live the alcohol content is supposed to be 10% but sometimes "errors" happen and we can have more :) While it is unlikely you could have a point in the ignition timing map that causes a slight engine ping under conditions of higher temperatures.

Think the gasoline (trademark as petrol in this part of the world) has ethanol as octane enhancer but restricted to below 10% for sure.
Went to a garage with technician claimed to have visited Japan for training on Mazda's RX 8s. Mentioned the noise problem to him and the immediate response was it was to do with the gear box, and the solution is to change to a 'thicker' transmission oil. Sounded like he's handled this before.