Bisimoto Pulse Chamber Review

[blpetry]

A few weeks ago I purchased the Bisimoto pulse chamber exhaust in "spec" (stanless steel) finish. Bisi is in California and I'm in Ohio so it took a couple weeks to arrive (thanks to Naomi at Bisimoto for keeping me apprised of order status along the way).

Once it arrived, it looked like a piece of artwork. I just let it sit on my desk and admired it for a few days.



Installation was relatively straightforward with the exception that the exhaust hit my valence ever so slightly near the rear edge of the cutout. I was initially aghast at even the thought of taking an angle grinder to my car, but after taking a look at what I was working with, that valence gets pretty beat up over the years and it didn't feel like too much of a sin to grind away 1/4" of material or so from the bottom.

NOTE ON INSTALLATION: I think the fitment issues some have experienced are not the product's fault at all, I think it fits a perfect car perfectly. But, remember, when we (hamfisted and inexperienced) DIY mechanics do engine drops, we, at least for a short period of time, sit (or drop) the engine down right on the exhaust system, which has got to tweak it a little. That, coupled with the fact that the stock tailpipe is *tiny* compared to this unit, doesn't leave very much room for tweaking. There is probably also at least a little bit of wiggle in the heat exchanger's mounting to the head and in the engine mounts themselves, where even a fraction of a degree can mean a couple MM at the tailpipe.



Once I fired it up, MAN was it LOUD A.F... Good sounds, not a bad thing to be heard, glorious actually, but it is LOUD. Fire-breathing dragon is the best way to describe it. From a pure sound-quality standpoint, I think its one of the best sounding exhausts I've ever heard. The burbles and pops on deceleration are just pure awesome.

My wife was sitting outside when I fired it up, and she immediately agreed that I should purchase the optional sound arrestor (I think she even offered to go to Bisi's site and order it for me). So, a few days later it arrived.



The arrestor seemed to do the trick and makes it much more socially acceptable. Its still very loud, but not so loud as to annoy other drivers. The arrestor takes some of the bass out of the sound and makes a little more raspy note, with a little less burble, but still enough. I've even driven it through a drive-through (although in general I don't like sitting and idling in an aircooled car).

Even with the windows down, you can still carry on a conversation or listen to the radio both with and without the sound arrestor. Its not really that loud INSIDE the car, its a very directional sound.

Disclaimer: I am a crappy videographer and my phone's camera (used for the interior videos) sucks. I got a better camera for the exterior videos.

Also note that my car has a gutted cat, so a car with a functioning cat may be a little bit quieter than mine.

Here are two startup videos, first without the arrestor and then with.

Without: https://youtu.be/3GY_rGJUrww

With: https://youtu.be/mdFUbl1BI04

Now, here are two driving videos (interior).

Without: https://youtu.be/Uj0Wwf0sIOA

With: https://youtu.be/Q4kq_PtRPgM

Finally two more (exterior) driving videos).

Without: https://youtu.be/K4s0f2auOWI

With: https://youtu.be/He32zqaAsWg

User HWG09 also recently posted this excellent review video (much better than mine) that shows the install (it seemed to fit perfectly on his really straight car):
https://youtu.be/NuzIn000xi8

Performance-wise, the pulse chamber appears to have done basically what Bisi is seeing on his dyno. These graphs were made with an android app that I wrote for myself a couple years ago (because the ones out there are too gimmicky or simply inaccurate).

Here is a HP/Torque curve with the stock muffler


With the pulse chamber (no arrestor).


With the pulse chamber (with arrestor).


As you can see, the pulse chamber results in a 12 HP and 16 (15 w/arrestor) increase on my car, pretty much as-advertised.

In my final assessment, I love it! Most days I have the sound arrestor in, but if I'm going for a spirited drive in the country its really easy to pull the sound arrestor out for the day. Even if I were building a car with an unlimited budget, I don't think I'd use a different exhaust, this one is low-hassle and great value for the money and SUPER light weight.

[lpsalsaman]

Nice review and showing your gains really helps! I been on the fence about this upgrade, but it seems as if I'm going to have to pull the trigger. Anyway enjoy it!

[Trakrat]

awesome write up.
Hopefully they will make a setup for my fabspeed exhaust headers and have one on each side!!!!!

[tdw28210]

super write up. Thanks for spending the time to create and post this.

[RarlyL8]

It would be more accurate to compare performance with the OEM muffler removed, just using a premuffler or cat with no muffler. You will see the same 12HP increase. That sound arrester looks like a 2" straight pipe. Not sure how that is different than putting a tailpipe on a premuffler.

[Bisimoto]

Bl, thanks, so much for your comprehensive review. I sincerely appreciate it. It is so exciting to see fellow Porschephiles experiencing and loving the benefits of the pulse chamber, and the wave technology it uses.

I am so intrigued by your app as well. Is this available via iOS?

A simple straight pipe does not give the sound, performance, power, or aesthetics of the pulse chamber and it took hundreds of engineering and dynamometer hours to perfect the design. Even the arrestor takes advantage of sound wave reflection.

Enjoy, and have a wonderful balance of the week. Cheers.

[douglas bray]

Very cool. Love this thing.

[ShoeDoc]

BPS: Purchased earlier this spring, just got around to installing it yesterday (Friday). My set-up: 1980 911 SC, completely stock rebuilt motor, transmission, suspension, gutted the interior & replaced. Cams are standard SC but "advanced"; exhaust system is stock with Cat delete. Sound absorbent materials in place, even replaced the head liner.

I can only estimate (as we've not done a dyno) but reasonably believe to be making approx. 210 HP. After installing the BPC with sound arrestor, I have to say the motor sound is just short of what a race car sounds like.
Whew! Admittedly, it is an intoxicating sound - complete with deceleration burbles, pops, gurgles. My "seat of the pants" dyno estimate is a nominal 10% HP gain - maybe 20 horses (?). What I can say is the RPM's come up substantially faster and without question the motor is breathing much easier.
Found myself pulling 5500 RPM's effortlessly and had to constantly watch my foot - the sound of the motor wrapping up plastered a huge smile on my face... had a one hour drive home from the shop and it's a screamer after 4K. Oh my... weak in the knees!

Now for the other side: It sounds like a race car. Would fit in wonderfully at Sebring. Living in FL means A/C and windows up; I can have a conversation with a passenger, listen to tunes on stereo, make phone calls and such.
I live in a semi-rural area - houses are spread out, lots of open roads, not much in the way of urban traffic or stop and go... no "concrete canyons" to reflect the sound.
That said, I still wish it were quieter; I came out of a stock muffler so I guess I have to allow for that as a reference point but the BPS - even with sound arrestor (I believe its supposed to reduce idle sound by 14db?) is LOUD. TOO loud.

I love the power.
I love the sound.
Love the scream of the motor.
Just not on a car that I drive every other day.
Track car? You betcha. Race car? Absolutely.
But, as things stand, I will remove it shortly.
However, I will also contact Bisi and see if there is any progress in developing an improved sound arrestor... 'cause if he can just get the db down, I could say without reservation, this is the least costly, easiest and simple 20 HP gain I ever had on any car I've ever run (I started 45 years ago with a '58 Corvette with a 283, but I digress.)

So, that's my take on the BPS... great device, well engineered & fabricated. Just a bit over-the-top for my aural tastes now.

ShoeDoc, aka, Bill in Florida

[Gaspassin]

Hello,
I also recently purchased a Bisimoto for my 1979 911 SC. My car had a goofy custom exhaust that sounded fine, drones a bit around 3K, but the muffler hung below the rear balance which bothered me a bit. AFAIK the exchangers and cat are stock. So I pulled the old exhaust off and went to put on the Bisi. When I did I also had a clearance issue with the rear valance. It's almost like the Bisi wants to be about a half inch shorter where it attaches to the Cat.

I am reluctant to start chopping the Cat both for the purposes of reverting back to stock or custom, and also for clearance issues with the pulse extension and the back of the carrier.

I also don't want to cut the valance to fit the new exhaust. I checked the part numbers on the exchangers and the Cat and the valance and they are all Porsche parts consistent with my car's year. I am going to post a few picture under my car and hope that someone in the brain trust here can identify my issue.

Thanks for the help!

[J-Mac]

So you can't really expect your new muffler to fix the issues if your old one is also off?

[Bisimoto]

Gas,
I may have a simple and elegant solution for you. Kindly write to me at Bisi@bisimoto.com. Cheers.

[Gaspassin]

Originally Posted by J-Mac

So you can't really expect your new muffler to fix the issues if your old one is also off?

The old CUSTOM Muffler hung low on a custom bracket off the carrier. When I test fit the bisi it didn't fit in the valence. I have the original bischoff (sp?) exhaust which when I test fit the tail pipe is centered on the valence. I was hoping that maybe someone looking at the stuff under there could give me an idea why maybe the bisi doesn't fit.

[Gaspassin]

Originally Posted by Bisimoto

Gas,
I may have a simple and elegant solution for you. Kindly write to me at Bisi@bisimoto.com. Cheers.

Thank you Sir.
I shall email you immediately.

[Duc Hunter]

Shame there isn't one for a 3.6.....hmmm

[Gaspassin]

Originally Posted by Duc Hunter

Shame there isn't one for a 3.6.....hmmm

Seems like it would be perfect for an outlaw widebody. I would guess Mr Bisi isn't making much money on the BMPC he sold me.

[Duc Hunter]

Originally Posted by Gaspassin

Seems like it would be perfect for an outlaw widebody. I would guess Mr Bisi isn't making much money on the BMPC he sold me.

Thats what I was thinking! Hmmm.

[bweiss1]

I am close to you in Cincinnati, and was thinking of putting this on my 87 Carrer. How is it after living with it for a few months? Do you still like it? I think it sounds amazing.

[oilman]

I’ve been running mine for 6months now. Love the sound and the power gains!