How long is your J-pipe / HelmHoltz resonator?

So drone has become a hot topic lately. Figured I would start a thread for people to list EXACTLY what exhaust they have and how long of a J-pipe / HelmHoltz resonator they put on to stop the drone for an easy reference for others.

:ford:

They are going to vary in length but for the most part, I believe 18-21" covers the desired length to cut the drone. I had a pair welded on to my Flowmaster Outlaws about a year ago and they COMPLETELY removed the drone. I was very pleased with them.

-Nick

MoneyPit#53 said:

They are going to vary in length but for the most part, I believe 18-21" covers the desired length to cut the drone. I had a pair welded on to my Flowmaster Outlaws about a year ago and they COMPLETELY removed the drone. I was very pleased with them.

-Nick

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That is way too short imo. Even 21" is for 2,400+rpm.

OP here is the table I spoke of in the other post.

Jay-rod427 said:

That is way too short imo. Even 21" is for 2,400+rpm.

OP here is the table I spoke of in the other post.

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This. Also, you'll get best results at that specific RPM, but will also significantly improve resonance at about +/- 200 rpm from that point.

Mine are inside my mufflers. :bolt:

BmacIL said:

This. Also, you'll get best results at that specific RPM, but will also significantly improve resonance at about +/- 200 rpm from that point.

Mine are inside my mufflers. :bolt:

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Exactly. That's why I went 25" 2,000 rpm target. since the coyote drone is worse from 1,800-2,200. 25" worked perfectly.

What is the recommended diameter of the pipe for that pipe length? Any pics? Great topic..

I can go home and measure my Solo performance J pipe.
I think it's 1.5 inch diameter.

I used 2.5" but I think you could go smaller and be ok.

Jay-rod427 said:

That is way too short imo. Even 21" is for 2,400+rpm.

OP here is the table I spoke of in the other post.

Click to expand...

Was this a breakdown from your personal car? I would imagine the frequencies from different exhausts can have a different range. Or is this going by the equation that I have been seeing out there that they say can be used for any car, that all is needed to know is the cyl#?

Right that is the frequencies for any v8, or v6. exhaust system has no effect as far as frequencies. exhaust system may make a difference covering up those frequencies.

The frequency table is purely the math of a v8 firing 4X per revolution of the engine, thererfore the number of pulses per minute.

Thanks for the chart!!! I just ordered my J-pipes for my next mod!!!

Jay-rod427 said:

That is way too short imo. Even 21" is for 2,400+rpm.

OP here is the table I spoke of in the other post.

Click to expand...

I feel like this would be a good question for a woman to ask a man at the bar...

Jay-rod427 said:

Right that is the frequencies for any v8, or v6. exhaust system has no effect as far as frequencies. exhaust system may make a difference covering up those frequencies.

The frequency table is purely the math of a v8 firing 4X per revolution of the engine, thererfore the number of pulses per minute.

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Awesome!! Thanks, I had seen folks talking about the equation but also saying to get the Hz freq that's irritating and go off of that freq. Glad to finally get someone to explain it in stupid for me. I got some Pype Bombs on the way an Hpipe on it now so I have heard there will be some drone to deal with so this will help immensely.

Ok, a good way to measure the frequency is with an Spectrum analyzer App to identify the offending rezonant frequency and with that determine the requirements for the J pipe. A good one is Advanced Spectrum Analyzer PRO.

Orange_cru$h said:

Ok, a good way to measure the frequency is with an Spectrum analyzer App to identify the offending rezonant frequency and with that determine the requirements for the J pipe. A good one is Advanced Spectrum Analyzer PRO.

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You're overthinking it. You can get an exact frequency from an engine RPM.