HMS rear exhaust review & HMS midpipe review; EDIT: Dyno Charts added

[oystero]

Ian / Joe. You will hear them soon enough

[Goombeh]

Well was fortunate enough to be at Active MotorWerks in Vic this afternoon when 1MOZ's 1M was started for the first time with the HMS exhaust.

I've never been a fan of the Akras as I found them a little raspy and high pitched (personal only of course). But when this HMS came to life.. .. ooohhhhhh..

My word, what a sound!! It makes the most glorious deep, racecar like sound. When the taps are closed, it's almost like stock, when the valves open up however... just sensational, loved it!! It was a great sound and one that has to be heard in real life I think.

[Piets94]

This is a brief review of the HMS midpipes running in conjunction with the HMS rear valve-exhaust.

Fitment is relatively simple - the pipes came in two parts that are connected and then tightened by clamps, and bolts up to the downpipes and rear exhaust.
Quality is as per the rear exhaust - excellent.

Dimensions are similar to the stock midpipes - 2x 60mm non-resonated and non-catted pipes, extending to a single 76mm connecting pipe; so no real increase in diameter from stock.

Cost - just under 1.3k AUD (to supply, ship & fit) (under 1k US) - $$$
These are essentially expensive straight cat-delete pipes for the 1M, but are 60% of the cost of Akra Ti midpipes, whilst a Berk/Maddad are again 60% the cost of the HMS midpipes.

Power gains - ??? Dyno to come soon. Certainly feels stronger, particularly higher in the rpm range.

MOST IMPORTANTLY, the sound:
Insane.
Perhaps a little too loud for daily driving, which initially disappointed me. With the rear valve-exhaust alone, I was driving around 90% of the time with the valve open and savouring the deeper sound from the exhaust. I believe that will change as the sound has been intensified in every way. The beauty of this exhaust is that with the press of a button, the sound becomes similar to stock.
Valve-closed - no drone, stock-like sound, perhaps a little quieter than OEM. Great for suburban cruising, cross-country commuting, law-enforcement.
Valve-open - loud, some drone at low rpm (around 2k rpm), pops and crackles, a characteristic backfire in M-mode under full-throttle at high rpm upshifts, definitely more racecar-like. The sound is AMAZING, but is certainly more at home on a race track.

To summarise:
For most people the HMS rear valve-exhaust will be enough, and I believe allows for more accessible use of the valve-open function for daily driving. The addition of the midpipes creates a whole new wild dimension that may be too much for everyday driving (necessitating the closing of the valve ), but allows for wider smiles when open But then I guess that's the whole point of this exhaust...

I have included some photos (the final photo is from the GMPPerformance website), and I have added a You Tube clip of the full exhaust sound (under threepeat).

Soon to come: DYNO to show any power gains from the HMS exhaust; & GoPro trackday vid.

Cheers!

[Piets94]

Not sure if this works. The camera doesn't quite capture the backfiring from the exhaust at high rpm in M-mode and valve-open. So addictive!

[1MOz]

Originally Posted by Piets94

Not sure if this works. The camera doesn't quite capture the backfiring from the exhaust at high rpm in M-mode and valve-open. So addictive!

Totally agree with your review mate.

Mine has N55 mid with HMS rear muffler and I am loving the sound it produces...and with a press of a button, it's all back to stock sound.

[Piets94]

Originally Posted by 1MOz

Totally agree with your review mate.

Mine has N55 mid with HMS rear muffler and I am loving the sound it produces...and with a press of a button, it's all back to stock sound.

Would love to hear a vid of your n55/HMS and hear if there is much difference to the full HMS sound. It's so obnoxious, but in a good way.

[Smiley1175]

I've got the berk mid pipes mated to the HMS and I must say its quietened down after 1000 km's.

I want it louder again!

Down pipes next I think!

[Piets94]

Originally Posted by Smiley1175

I've got the berk mid pipes mated to the HMS and I must say its quietened down after 1000 km's.

I want it louder again!

Down pipes next I think!

Hey, that's good to know. There's hope to keeping that valve open everyday then!
Any attention from the police yet? With the mids on I reckon it's only a matter of time. You'll need earplugs with down pipes fitted

[Smiley1175]

Originally Posted by Piets94

Hey, that's good to know. There's hope to keeping that valve open everyday then!
Any attention from the police yet? With the mids on I reckon it's only a matter of time. You'll need earplugs with down pipes fitted

No issues as yet, but I have closed the valve when I see cops around!

I'd actually like the valve to open on start up and only close when you manually select it.
Each morning as I start the car, valve open, mdm on.

[-Z-]

so, we already know it sounds great, any hp gains / weight savings?

thanks.

[1MOz]

Originally Posted by -Z-

so, we already know it sounds great, any hp gains / weight savings?

thanks.

Neither IMO, well not much to consider it a performance mod. This is purely a sound gig.

[-Z-]

Originally Posted by -Z-

so, we already know it sounds great, any hp gains / weight savings?

thanks.

Just read the OP again, he suggested it looks about 2/3 weight of oem, given that stock is 26.5 lbs, we could see about 8-9 lbs savings... At the same time this means it weights close to titanium 12 lbs vs 18 lbs, is that for real?

Something tells me there are extra hp gains there too...

[Piets94]

Originally Posted by -Z-

so, we already know it sounds great, any hp gains / weight savings?

thanks.

Dyno to come, but I presume any gains will be from the cat-delete midpipes and similar to the small gains reported with other brands.
According to HMS, weight is approximately 1/3 lighter than stock, but I haven't verified this.

1MOz is correct, it's more of a sound thing.

[a7med606]

where is the valve control button ?

[E30 Racer]

What's the tube diameter where the axle back bolts to the midpipe? Does it come with an adapter to fit the smaller diameter of the original/N55 midpipes?

[1MOz]

Originally Posted by a7med606

where is the valve control button ?

Read here: http://www.1addicts.com/forums/showthread.php?t=914108

[1MOz]

Originally Posted by E30 Racer

What's the tube diameter where the axle back bolts to the midpipe? Does it come with an adapter to fit the smaller diameter of the original/N55 midpipes?

From memory, I am certain it's the same diameter so it's a straight connection.

[Piets94]

Originally Posted by Ian///M

I'm surprised HMS get away with engraving trademark '///M' logos on the exhaust

Hmm. Not sure of the legalities involved, but they don't normally offer the 'M' logo. It's usually either their own 'HMS Performance' logo or none at all. They offer to design a custom logo based on customer wishes for $200. I asked for the 'M' and that's what I got.

[a7med606]

Originally Posted by 1MOz

Read here: http://www.1addicts.com/forums/showthread.php?t=914108

i dont why you just posted the link for the first page , just tell me where is it and we are done .

still i didnt find the valve control button :S
if you dont want to explain it there is many other members that will help me to find it or will tell me how it works

[Cope]

Originally Posted by a7med606

i dont why you just posted the link for the first page , just tell me where is it and we are done .

still i didnt find the valve control button :S
if you dont want to explain it there is many other members that will help me to find it or will tell me how it works

Read his original post in that thread. It says quite clearly:

Wired valve-control - the exhaust flaps are controlled by a wired button, and installed anywhere within the car interior. The installers opted for a location just near the OBD port for maximum stealth from law enforcement! Glows 'red' when in 'attack' mode. Apparently a bit of pain to install, but this could be as simple or as difficult as you make it. The installers opted for max discretion (and max difficulty), so ran the wiring beneath the interior trim. This required the rear seats out, but the result is no visible modification to the car. Alternatively, the wiring could be run below the car, which would make this part of the install much easier.

There's even a picture of the valve control glowing red in one of his photos.

[E30 Racer]

Originally Posted by Piets94

Hmm. Not sure of the legalities involved, but they don't normally offer the 'M' logo. It's usually either their own 'HMS Performance' logo or none at all. They offer to design a custom logo based on customer wishes for $200. I asked for the 'M' and that's what I got.

You made the correct decision...looks (and sounds) perfect.

[E30 Racer]

Could someone please take a picture of where the stock N54/N55 mids and the HMS rear section bolt together? Curious to see the difference in diameter.

Here's the Akra mid jointed to the OE rear section for comparison sake: