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I dynoed and got only 236 torque at the wheels (256rwhp though).
I have basic bolt ons.

Why is my torque so low? Is it due to the injen? I did notice a little bit of a low end loss when I installed it

Also, what is this fiberglass issue I heard about and how do I check it?

Thanks
 

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What was your hp and torque before you added the injen exhaust?
 

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I've also heard about low end loss with Injen exhaust. But dont know why. The problem with the fiberglass is people are finding fiber on there rear bumpers appearently coming from the packing in the cans. Supposingly Injen took care of the problem in the later SES model exhaust....
:newbie:
 

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Originally posted by Dozer@Jul 9 2005, 07:33 PM
I've also heard about low end loss with Injen exhaust. But dont know why. The problem with the fiberglass is people are finding fiber on there rear bumpers appearently coming from the packing in the cans. Supposingly Injen took care of the problem in the later SES model exhaust....
:newbie:
[snapback]129161[/snapback]​



loss of torque is becaue of a lack of X or H pipe.
 

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Originally posted by Zivman+Jul 9 2005, 09:50 PM-->
<!--QuoteBegin-Dozer
@Jul 9 2005, 07:33 PM
I've also heard about low end loss with Injen exhaust. But dont know why. The problem with the fiberglass is people are finding fiber on there rear bumpers appearently coming from the packing in the cans. Supposingly Injen took care of the problem in the later SES model exhaust....
:newbie:
[snapback]129161[/snapback]​



loss of torque is becaue of a lack of X or H pipe.
[snapback]129185[/snapback]​

explain this in more detail. borla and the other true duals dont have h or x pipes and their torque is just fine (i think)
 

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Maybe it is from the 2" piping and turbulence caused by the steps at the flanges? Injen claims the pipe diameter is optimized for power and is dyno tuned (this must be true, the marketing guy says so) but the factory used bigger pipe coming out of the cats and into the Y. I have never seen an exhaust that gets smaller as it goes down pipe.

Seems odd.

As for the packing coming out, some will say it is the resonators (front glass packs) because they sound hollow when you tap on them. Mine sounded hollow when I installed them and looking at their design I see no reason the packing would blow out. It’s just a straight through glass pack. On the other hand the back boxes contain silencers about mid way down. As gas flow increases this silencer becomes a restriction (that is how all silencers work and no it’s not a performance part) but unlike most placed at the end of the pipe (like your typical rice can), this mid glass pack insert causes gas to travel around it, flow through the packing and take the packing with it as it does so.

All this may be why Injen is redesigning their system.

Chris
 

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Originally posted by Conceyted+Jul 10 2005, 02:01 AM-->
Originally posted by [email protected] 9 2005, 09:50 PM
<!--QuoteBegin-Dozer
@Jul 9 2005, 07:33 PM
I've also heard about low end loss with Injen exhaust. But dont know why. The problem with the fiberglass is people are finding fiber on there rear bumpers appearently coming from the packing in the cans. Supposingly Injen took care of the problem in the later SES model exhaust....
:newbie:
[snapback]129161[/snapback]​



loss of torque is becaue of a lack of X or H pipe.
[snapback]129185[/snapback]​

explain this in more detail. borla and the other true duals dont have h or x pipes and their torque is just fine (i think)
[snapback]129228[/snapback]​



the borla true dual does have a H pipe
 

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I've seen pics of people who have gone to the local exhaust shop to get a custom h-pipe welded on. Seems to work out for them.

Is the Injen a true dual system? I can't remember. If so, then like Zivman stated, you should look into 'creating' that h or x pipe connection.
 

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Originally posted by Steve350Z+Jul 10 2005, 06:12 AM-->
Originally posted by [email protected] 10 2005, 02:01 AM
Originally posted by [email protected] 9 2005, 09:50 PM
<!--QuoteBegin-Dozer
@Jul 9 2005, 07:33 PM
I've also heard about low end loss with Injen exhaust. But dont know why. The problem with the fiberglass is people are finding fiber on there rear bumpers appearently coming from the packing in the cans. Supposingly Injen took care of the problem in the later SES model exhaust....
:newbie:
[snapback]129161[/snapback]​



loss of torque is becaue of a lack of X or H pipe.
[snapback]129185[/snapback]​

explain this in more detail. borla and the other true duals dont have h or x pipes and their torque is just fine (i think)
[snapback]129228[/snapback]​



the borla true dual does have a H pipe
[snapback]129255[/snapback]​



yes, the borla does have an H-pipe. Making the banks cross baths equallizes the exhaust pulses and increases scavenging resulting in more power. "Other true duals" may not have an H or X pipe and not loose any torque as a result of reduced diameter piping. I would be hoping for gains across both HP and TQ when investing in a $1000+ exhaust. Not a slight gain in HP and no gain, or even a loss, in tq.

On a TT setup, this becomes less important and what you need to focus more on is overall flow. On a SC setup, the H-pipe and/or X-pipe become increasingly important in addition to overall flow. With a Single turbo on a V6 motor, you will obviously not have true duals, so in that case, the B-pipe back is what you want to look into for adequate flow.
 

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The Injen has less back pressure. Back pressure is needed in an exhaust system to help make torque. If you decrease the back pressure to raise horsepower, the result will be lower torque. Most aftermarket exhaust systems are designed for a happy balance.
 

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Will the backpressure myth ever die?

Backpressure does not help anything. Velocity helps torque, to big of pipe hurts low rpm exhaust gas velocity and torque will drop.

A proper exhaust system can be built to yield high velocity and no backpressure (and for that matter be within the realm of street legal sound) and have the same power potential as open pipe.

Unfortunately, Injen marketing department, who claims to have gotten their information from their R&D department, believes backpressure is important (hey, that is what he said in the email to me).
"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."


So how likely are they to be building properly designed systems?
You also need to wonder why Injen is redesigning their exhaust for a third time.

If your interested, here is an article from a guy who has written "the book" on quite a few motors and has probably spent more time on the dyno than most people alive. It is centered around the Chevy 350, as this was the intended audience but most of it still applies. http://www.popularhotrodding.com/enginemas...ore/0505em_exh/

Just some thoughts

Chris
 

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Originally posted by HyperSprite@Jul 11 2005, 06:08 AM
Will the backpressure myth ever die?

Backpressure does not help anything. Velocity helps torque, to big of pipe hurts low rpm exhaust gas velocity and torque will drop.


If the exhaust velocity is reduced, then wouldn't the back pressure be reduced as well? Too big of a pipe would be over kill for a particular engine and allow the spent gasses to just tumble around rather than being pulled out...correct? So a smaller pipe, with a little bit of back pressure would increase the velocity and increase the torque.....correct?

sean
 

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The basic principle is that you want to find the smallest exhaust diameter that will flow the necessary amount of gas (if I am correct). Theory being that a small diameter keeps the velocity high. However, too small and you run into problems. To large, and the velocity slows and exhaust scavenging falls off.

So, for example, lets say that a single 2.5" pipe is found to be the perfect fit. To help keep velocity high, you could take other steps that would not be restrictive. I for one would wrap the exhaust. The exhaust wrap would help to keep the heat in. Hot exhaust is more energetic and this would help to keep the velocity up longer. This is the reason that my headers are wrapped. This is also the reason I am considering wrapping my cats and the section of my Borla exhaust between the cats and the H-pipe.
 

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Originally posted by socalsean@Jul 13 2005, 09:58 AM
If the exhaust velocity is reduced, then wouldn't the back pressure be reduced as well? Too big of a pipe would be over kill for a particular engine and allow the spent gasses to just tumble around rather than being pulled out...correct? So a smaller pipe, with a little bit of back pressure would increase the velocity and increase the torque.....correct?

sean
[snapback]131398[/snapback]​


Peptibond it right, there is an equilibrium that you are looking for. You want to go as small as you can, before it causes a resurrection.

What does not make sense about Injen is, I would think velocity would be through the roof with 2" pipe, somehow I think something else is disturbing the flow. As I munitioned before, there is a reduction in pipe size at the cat connection and it is quite abrupt, this might be doing something strange but who knows.

I so wish I had a flow bench to test these systems out on.

Peptibond, you should do some more investigation before wrapping the cats (unless they are just test pipes), they get real hot and holding all that in may break down the metal and cause them to disintegrate. I would check with thremotech or whoever is supplying your heat wrap.

Chris
 

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Question.....

My volvo is running just a three inch pipe out the turbo which is probably a foot long. It's actually larger than 3" out the turbo, but then reduces to 3". When I add the rest of my exhaust system tonight (Full 3" with magna flow straight through, side exit) will I feel more torque?

sean
 

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no... it will be much less. I speak from experience of having a Big16G'ed Eclipse GSX with full 3" from the downpipe back. The non restricted 3" exhaust from the dp back was a major flaw in the way i modded my car. I think i lost so much down low power that I almost wanted to redo the exhaust 2.25-2.5 just to gain some tq back.
 
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