Injen's Dirty Little Secret about the Injen SES1985C for the 350Z

While their website is short on information about their products, it has lots of information about how they are trying to protect their good name from counterfeiters. I for one believe the best way for them to protect their name is by not selling deceptive products like the Injen SES1985C for the 350Z.

On the outside one might believe from looking at the SES 1985C, that it is an unrestrictive straight through system comprised of four mufflers. The straight through four muffler part is true but unrestrictive, it is not. The deception is where they put the restriction. The silencer, previously removable on the earlier 350Z systems, is now permanently in place in the center of the back mufflers just out of view from the casual inspection. There is no place in a performance exhaust for this type of "restriction silencing", a tactic OEMs have used for years to make cheep quite mufflers (a primary reason aftermarket systems showed gains on almost every application).

This form of silencing is also the reason why the Injen SES 1985C for the 350Z is louder at low RPM than high RPM. At low RPM exhaust moves easily through the silencer but once the motor reaches about 3000 RPM, it is at it's maximum flow rate and the rest of the exhaust gasses either back up in the system or is forced though the packing. Absorption type mufflers were never designed to have exhaust forced thought the packing, this causes the packing to get blown out prematurely and fiberglass to cover the back of the car.

This is an illustration of the back muffler on the Injen SES 1985C for the 350Z, the light red arrow is free flowing exhaust passing through the center of the silencer, the dark red arrow is exhaust bypassing it and pushing through the packing.

This shot of the Injen SES1985C for the 350Z was taken with a mirror, in the center you can make out how much smaller the silencer is than the main muffler tubing. Perhaps Injen should have used a slightly smaller tubing in the muffler but this was probably the one they had on the shelf.

This is about all you can see of the silencer from the back of the car but this is the clue that something is in there.

This is a shot with the webcam coming from the engine side, note the gap at the leading edge of the silencer. If packing was coming from the front boxes, I would expect to find it in between the perforated tube and the silencer I could find no such evidence of packing here. 

Here is a movie I made with a web cam and a usb light, it's not perfect but I think it shows the restriction pretty well.

Injen Exhaust Web Cam < click

(the single splice in the movie was done to cut out the minute or so of time I was trying to get the camera past the obstruction)

I wrote this because I was a loyal customer of Injen who feels they were deceived by a company claiming to sell a performance product.

 

  

DocCNader wrote Injen regarding this page with the following

Dear People at Injen,

I just ordered an injen straight tip exhaust for my 350Z and until now
I thought i was buying a good system that would achieve more HP. Doubt
has risen do to recent posts on www.my350z.com and this article
http://www.hypersprite.com/auto/pic...nd002/injen.asp Can you
explain to me if the information on the article is true and what can
be done about it?

Thanks,
C

INJEN'S ANSWER>
 

The fiberglass is due to the exhaust system breaking in and the period in
which it will settle will vary. We have had similar situations with other
350z owners who have expressed concerns about the fiberglass turn around to
tell us that it eventually stopped. Or when they have claimed it to be
completely blown out, to us having them come in and find nothing wrong with
the system whatsoever. We are not saying that this is the case here, but
there are many variables to lead to the difference in break-in period. It
may in some cases take longer than expected.

As for the silencers, what you need understand that the 350z or any car in
that matter, relay on a certain amount of back pressure and/or restrictions.
This is quoted from our R&D dept... "Not all engines need free flowing
exhaust pressure. They need the right combination of free flow with the
right amount of restrictions. For example most people think that
turbocharged vehicles need the biggest exhaust piping you can squeeze in the
car. This is not true due to the motor not being in boost 100% of the time.
It's all about combination...if there is a restrictor there, then it was put
there for a reason...to control exhaust flow to achieve the best possible
air flow for that specific car.

Remember when it come to intake and exhaust systems it not about max air
flow...it's about combination, combination, combination!!!"

Also, we produce products intended to be used in a legal format and hence
abiding to the California Decibel requirement. After our first initial
release of the 350z angled tip exhaust with removable silencers, we listened
to all the 350z owners whom suggested changes to be made to the system due
to the awkwardness of the silencers and overall look. Therefore, the release
of the newly designed straight tips with built in silencers were made. You
may have negated the fact that we in no way hide the fact that there is the
apparent addition of the built in silencer and in fact is also one of our
many key points of the system. Not to mention, the 350z exhaust system along
with all of our cat-back systems are dyno proven pieces that have been tuned
accordingly as a complete system with all components added. So your so
called "[Dirty Little Secret]" is not really a secret now is it?

We do not take offense to your posting, but please be fully aware of what
you are stating and have it backed by information that is relevant and not
just a mere "findings." If you look at any exhaust company on the market,
from a straight flow design or a chambered design, everyone differs and has
engineered their system to a specific design for a reason. Ours, as in the
aforementioned, were to offer a great upgrade on the existing stock
component- adhering to legal requirements and to give you an added
performance gain. I hope this information will shed some more light on the
matter.


Best,

Duy Le
Sales/Marketing
Injen Technology Co., Ltd.
(909) 839.0706 x201
(909) 839.0427 fax
 

My response to this email is this

INJEN'S ANSWER>
As for the silencers, what you need understand that the 350z or any car in
that matter, relay on a certain amount of back pressure and/or restrictions.
This is quoted from our R&D dept... "Not all engines need free flowing
exhaust pressure. They need the right combination of free flow with the
right amount of restrictions. For example most people think that
turbocharged vehicles need the biggest exhaust piping you can squeeze in the
car. This is not true due to the motor not being in boost 100% of the time.


Here they are just perpetuating the "backpressure" myth. There is no science behind it, just trial and error system design that resulted in incorrect conclusions based on results. Exhaust design is not "the right amount of restriction", it's velocity, and velocity can be maintained without restriction. If in fact his response is based on the R&D department at Injen, they have some real issues.

It's all about combination...if there is a restrictor there, then it was put
there for a reason...to control exhaust flow to achieve the best possible
air flow for that specific car.

* see not below


Remember when it come to intake and exhaust systems it not about max air
flow...it's about combination, combination, combination!!!"

Well really, it should be about 2.2 CFM per horse but whatever. Is each side of the Injen system flowing around 320 CFM, anyone have a flow bench?

Also, we produce products intended to be used in a legal format and hence
abiding to the California Decibel requirement. After our first initial
release of the 350z angled tip exhaust with removable silencers, we listened
to all the 350z owners whom suggested changes to be made to the system due
to the awkwardness of the silencers and overall look. Therefore, the release
of the newly designed straight tips with built in silencers were made.

* The restrictor was placed inside so Injen could claim a 50 state legal system. The earlier system had removable silencers so they could attempt to meet the 95 db limit. California does not permit user adjustable exhaust systems, so by making the silencer internal they stay within the law. So is this system form over function. Here it sounds like the silencers stuffed inside to make the system look better.

You may have negated the fact that we in no way hide the fact that there is the
apparent addition of the built in silencer and in fact is also one of our
many key points of the system.

Not to mention, the 350z exhaust system along
with all of our cat-back systems are dyno proven pieces that have been tuned
accordingly as a complete system with all components added. So your so
called "[Dirty Little Secret]" is not really a secret now is it?

Anyone know where I can find these "many key points" or a mention of built in silencers? There website, at last look, has very little in the way of information on their design, even the dyno charts have become hard to find.

We do not take offense to your posting, but please be fully aware of what
you are stating and have it backed by information that is relevant and not
just a mere "findings." If you look at any exhaust company on the market,
from a straight flow design or a chambered design, everyone differs and has
engineered their system to a specific design for a reason. Ours, as in the
aforementioned, were to offer a great upgrade on the existing stock
component- adhering to legal requirements and to give you an added
performance gain. I hope this information will shed some more light on the
matter.

What do I have other than findings from investigation. I posted what I found and what effects I thought it had. I believe it better describes not only the fiberglass issue but also why it is so loud at low RPM.

What I do know is Injen has an issue with fiberglass blowing out of their systems and other than a "beak in period" excuse, they don't seem to adequately explain any of it. I know that if you take a back box off the car after 3k miles, and flip it end to end, you can hear the packing land with a "thunk" inside the muffler each time it's turned over. I know that every Injen system I have seen has the drivers side tip sticking out further than the passenger side. I know that the piping is smaller diameter than the little ends of the stock Y pipe.


 

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