JCR-Porsche

Ill prep another

JC

SpydrGuy

I'm considering the JCR non-silenced valved exhaust for my Spyder. No doubt it is exactly what I'm looking for at full throttle. But how livable is it in everyday driving below 4K RPM at part throttle acceleration and cruising? I suppose with OEM valve control it shouldn't matter whether PSE is on or off in this RPM range, correct?

works_team

That is what I ordered from them a week ago. I will report when received and installed. I don’t plan to add any other parts, this seems exactly the right solution for me.

DocMo

I’ve had it for 6 months. It is significantly louder and better sounding than stock. My Porsche SA loved it too. It has a little drone on the highway between 2000 and 3000rpms but it remains neighbors and wife friendly. I really like it!!! If you plan only the cat back, it is the way to go! Quality is pretty amazing too. My wait time was ~10weeks

Westcoast

As opposed to the non-silenced JCR I have the 'silenced' version, I think it strikes a perfect balance for all out sound and below 4k cruising especially because with the valves close and the silencer in play it make the system a little more livable. Jonny could comment how many dB quieter the silenced version is a part throttle but to me it is noticeably quieter with the valves closed... yet throw them open and WOW is is pretty intense and I doubt it gives a lot away to the non-silenced version in this setting. IMHO the best of both worlds!

works_team

3-4db quieter in closed flaps mode if I remember correctly

SpydrGuy

Thanks Westcoast. Your posts and DocMo's have provided a lot of really useful firsthand information on the JCR silenced and unsilenced valved exhausts. I like the JCR because not only does it sound great, but it was designed to work with the OEM valve controller and OAPs, and as we've learned if you take away either one of those it's a lot more difficult to control drone. I'm leaning toward the unsilenced exhaust to get a bit more volume since Jonny said it was only 2-3 dB louder than the silenced version. I just want to make sure it doesn't make everyday driving where the valves are always closed annoying. DocMo said it passed the wife test, which is a pretty good indication I'll be happy with it.

Are you still running the Akra OAPs? I thought I read that you believed the silenced JCR was maybe a little too quiet with the OEM OAPs, but with the Akra OAPs maybe a little too loud at times.

UncleDude

Isn’t 2-3db a lot? I don’t think it is a linear measurement.

Westcoast

Yes, 3 dB increase sound energy is doubled, or 3 dB decrease sound energy is halved and it is not linear but uses a logarithmic scale.

A decrease of 3 dB is quite noticeable.

Westcoast

Yes, I still have the Akra OAP's in place, I find that it improves the overall clarity of the full throttle sound you hear when the valves are open and yes I found that with the OEM OAP the JCR system was just a little quite/muted.

When you are in the mood, open the valves (I have the Cargraphic controller) and enjoy the 4.0l flat-6 song all the way to redline, but when there is the desire to have a more civilized tone, set the valved to OEM and let the silenced portion of the JCR provide that additional sound control to provide a quieter cruising sound, still clearer than with the OEM OAP's but not too loud.

SpydrGuy

Mathematically you are correct that 3 dB doubles the energy, but the human ear is not linear either. It depends on frequency, but in the music world a change of 3 dB is accepted as the smallest difference in level that is easily heard by most listeners listening to speech or music. It is a slight increase or decrease in volume. I'm not an expert, but just reporting what Google thinks.

Westcoast

Yes a doubling of sound energy, and from direct experience with the JCR rear section on the 718 4.0l I have no doubt that you would hear the 3 dB difference valves open to closed.

In the workplace a 3 dB (A) increase in sound energy cuts the allowable exposure time in half so you can imagine how much sooner you would tire of the sound level of the exhaust during a long cruise... As an example without hearing protection and with the sound at 97 dB only 30 minutes of exposure is recommended, at 100 dB this drops in 1/2 to 15 minutes!

SpydrGuy

This is what makes picking an exhaust so difficult. Watching videos and quoting numbers is no substitute for first hand feedback from owners who have driven with an exhaust extensively, so I greatly appreciate your opinion. FWIW, I don't know if the 2-3 dB increase in sound volume with the unsilenced JCR exhaust over the silenced version is at full throttle, cruise, or both. Hopefully DocMo and Jonny can chime in. A 3 dB increase at full throttle might be perfect, while 3 dB at cruise would probably get tiring quickly.

Poupon McArr

Absolutely agree with this.

Also from what I can remember I believe 3dB double something related to sound, but a 10dB increase needed to double human perception of volume.

But your last part is spot on I think it depends where the 3dB increase is - if it’s at 2500-3000 RPM only then I would think that would get annoying and not worth it. If it’s across the whole rev range then it may be worth it and if it’s only above 4k or so then that’d be ideal.

hugo993

I am in exactly the same way, with a preference for the non-silenced version and keeping EOM opf and gpf
I don't know if I can sum it up like this: non silenced vesion if you keep opf and gpf.
silenced version il you want change opf and gpf
the opinions of those who have a non silenced version with EOM gpf and opf?