I have a 91 N/A with RB True Duals. I love the way it sounds with the pedal to the floor but there strange noise upon deceleration, almost like a fluttering of air. The engine is a fresh rebuild with a moderate streetport (not exhaust). The car is currently running off Megasquirt 1 V3.0. I would love to hear what you guys think is causing this stange "fluttering" upon deceration.
It's not a rubbing noise, it's comes with the airflow out of the exhaust. And it happens at the same time coming out of both pipes.
Is this some kind of Megasquirt tuning issue?

The link below will take you to the video of the car accelerating and decelerating. Note: When I move the camera in the video the sounds gets worse. The most accurate sound of the phenomenon is in the first 20 seconds.

http://www.youtube.com/watch?v=XxUmud-JLic

Thanks for all your help,

Brian

 

I'm also interested in people's insight. I just recently bought a stock 90 N/A and although it doens't have an aftermarket exhaust yet it still makes that same sound, just not as loud. I suspect if i put an RB exhaust on, which is a plan for the future, that the sound would be magnified similar to this?

 

Dosn't seem like a megasquirt issue to me.

The only thing I can think of is have you either hooked up or blocked off the tube going from the RB header to the aux. port actuators? Your car looks like an S5 so I think you would need to block it off.

That's the only thing I can think of.

 

The car is an S5 and so the RB header so it does not have the tube found on an S4 header. The airpump actuates the aux. ports.

 

It's due to the true-dual exhaust design. That's the only time I've ever heard that.

 

my car is bone stock and it still makes that noise. It definitely isn't as loud as RX7tuners but it's most definitely there. Mine only makes that noise when the engine decelerates from just under 4k rpm back to idle. It doesn't seem to do it when the car's in gear just when it's in neutral or when the clutch is in. Is it something i should worry about or just a nuisance that i'll have to learn to live with?

 

I have heard odd noises on decel from not cutting fuel, or at least not reducing it enough in those situations.

 

Oh, my fault. But, yeah, I agree with Ken. Check your kpa, tps, and rpm set points in your overrun settings. Depending upon porting, etc., it will differ, but mine is somewhere between 32 - 34 kpa and 1400 rpms. Also, in the "tools" pull down menu, calibrate your tps, and whatever your closed throttle #is at, just add 2 more to it, and put that # in.
As an example, my #'s are: rpm greater than:1400rpm, kpa lower than: 34, tps lower than: (my closed # +2), and coolant greater than: 150
If that is not it, then I honestly do not know.