I need a small electronic board built for an intake system.

The board has to take an audio signal, filter it, invert it, and variably delay an output signal from 0.05-.5 sec.

The input for the delay would be RPM based and probably use an induction pick up off a coil.

The delay base would also be adjustable manually for tuning.

Also needed would be signal amplitude modulation by TPS maybe?

Anybody here that can help? I know I can find an engineer to make it but I worry of high costs for just one or two for now.

 

[QUOTE]Originally posted by cmnsnse
[B]I need a small electronic board built for an intake system.

 

kewl, someone who knows what I want

answers, 1: ummm well good enough to produce a clean wave if needed at about 80hz. and size big enough to last about a second.
2: Well thats tough to say as one effect might be optimal but as a baseline would start with a simple 18db/oct slope at 40hz and 200hz for the window between. Now Possibly the best thing may be a pre-recorded signal timed with a cam position now its getting more complicated . . . but anyhow.

3: Just phase inverted

4: Ask away

To give you a better picture of what Im doing , I just need the computer for optimization . . . is that a word?

http://www.s2000online.com/forums/showthre...p?threadid=5536

 

[QUOTE]Originally posted by cmnsnse
[B]1: ummm well good enough to produce a clean wave if needed at about 80hz.

 

This is looking very interesting - I'm glued to this post for sure.

 

Im Im thinking a high power subwoofer will work, as long as I chamber it right but if I use an amplifier in-line it has to have a pretty good damping factor.

Depending on where I put it and the chamber's size, dictates the capacity and stregnth needed. I just need to figure out how Im going to integrate it into the manifold. I


I have done some recordings of the manifold and have to do more so I can get a better idea of the signal needed to be introduced and how it needs to be modified throughout RPM and throttle position.

BTW the recordings are digital so I can give you good stuff.

Im also thinking that instead of modifying an incomming signal It may be better to just use a predetermined signal that is variable manually and also by input sensors.

 

Hi. I'm an audio DSP engineer and have made digital ANC systems before. My thesis was actually on one of those things.

I think you may well need an adaptive system here (to cope with temperature and altitude changes), but it's better not to get into that until you've tried something simpler.

Your idea is a good starting point, but your "filter" response may end up being too restrictive. Your biggest problem is the flat response in the passband. I doubt that whatever transducer you can build will have a flat response 0 to 80Hz, and it's also unlikely that the "noise field" has a flat spectrum in that range either.

Are you thinking feed forward or feed back control here? If it's feed forward then you're going to have a problem of mic location. It has to be somewhere that the transducer can't influence the sound pressure it picks up (that would be feed back ). I think that's going to be hard to achieve so you might need a feed back system with a high loop gain. Here another problem is stability of the closed loop, which might be marginal at the extremes of your frequency range. That's usually solved by cutting the loop gain at the point where the stability margin is exceeded. Feed forward has problems of its own, the biggest of which is calibration, hence the adaptive suggestion above.

My first suggestion is that you go for the simplest possible analog circuit first and see what happens. Digital is best if you need to do a fixed delay, but remember that at 80Hz the wavelength is 4.3m which is over 14ft. I think you therefore don't need a delay at all, but a simple microphone placed in the airbox connected to the transducer via a high negative gain. You can do that with an op amp circuit. Your transducer will more than likely supply the necessary rolloff above 80Hz (or whatever) that you need for phase (stability) margin. Another advantage of such a feedback arrangement is that the non-flat response of the transducer and noise field are not a problem.

If any of this is just mumbo jumbo I can possibly make it clearer.

 

lemme do some study time and Ill determin the best thing to do.

It would have been a feed back system, but would need a variable delay simply because the pressure wave needs to be sent at different times per RPM . . .

anyway It might be best for a predetermined signal to be used instead of processing an incomming one - so I can time off of a cam sensor rather than getting into the complications of tuning a noise cancelation project.

BTW the freq range is 30hz - 350hz and that should be good for 1000 - 10,000 rpm operation

 

MacGyver,

OK here is where Im at, needed features:

-2 predetermined signals(waves) one for non-vtec and one for vtec (I have them if needed)

-Timing adjustable from 0* to 180* crank (Manually with good resolution)

-Input from VTEC solonoid, to switch waves

-Signal amplitude adjustable from -18db to 0 in relation to throttle

-output frequency dependent on RPM . . . 2xRPM/60 = Hz so its within 30-350hz sensed off of crank/cam

Maybe an amplitude gain in relation to rpm/vtec . . .

Things I need to find out:

How difficult it would be to piggy back off 3 sensors without hurting the ECU's ego.
TPS resistance/voltage
VTEC wouldnt be so hard
Crank angle signal ? How many pulses per rpm?

Nevermind about signal processing, its not needed. I just need to work with pressure waves. One thing I may run into is a natural resonant freq. of the system - it may need a cut at that one point.

naishou,

Thanks you talked me out of DSP, heh
I think a natural responce of a subwoofer (not being flat) might work the right way in respect to RPM and freq. and the needed pressure waves.

The biggest benifit of this system would be similar to a 1-2 psi boost and depending on how you set the timing, reduced intake noise

Now I need to think about the manifold . . .

 

As I'm passing through tonight, I thought of something else to try...I don't know what the response time is like, but you might want to look at simple pressure sensors instead of trying to record, delay, the playback a sound. If the pressure sensor works, you could use a prerecorded sound played back at different speeds (for the different RPM ranges)...no need to record real-time, which also removes a lot of the necessary filtering of the incoming signal.

Naishou...I'm glad to see another DSP guy on here, I was starting to get lonely