Hi all:

Just wondering, does the Greddy EVO 2 merge the exhaust gasses into a single pipe halfway down or is it true dual?

I have read conflicting information and numerous searches have yielded that it is either a) and X pipe, or b) true dual.

Could someone please set the story straight? Pic courtesy of ACP, thanks in advance.

Ravi

CLICK ME FOR PIC

 

Picture says it all really. True dual then into one pipe then dual again.

 

Yep, it's an X-Pipe....Pic Here

 

Thanks for the reply--I thought it was an x pipe. Did you notice any performance gain after installing it?


I'm trying to gather information from n/a evo2 users.

ravi

 

I posted in another thread about perf. gains. I'm putting my car on the dyno at AAM tomorrow, so I'll have HP/TQ numbers for the EVO2 with Random-Tech cats.

Honestly, I noticed some low-end torque loss, but the high-end seems to flow better. The graphs will show tomorrow I guess.....

 

Thanks--I assume the low end torque loss can be attributed to large diameter piping and a leaning out condition.

It will be interesting to see.

Thanks again.

 

Actually, a lean engine generates more power, not less, so it doesn't have to do with mixture ratios. Additionally, nothing on my intake side has changed, so I'm not flowing any additional air into the chambers that could generate a lean condition.

There is much science behind back pressure with regards to valve overlap, vacuum, exhaust pulse and exhaust header balance, etc. As a result, there is also much argument about back-pressure and it's effect (positive or negative) on engine power, but for the most part, I believe that for an engine of this displacement, the back-pressure applied by the stock system is crucial to generating low-end torque.

The only way to correct low-end torque loss condition is to balance it out with more airflow before the cylinders. This can be done with plenum, intake, etc., or with F/I, which is the route I am going.

Anyway, I'll post numbers tomorrow night.

 

But what about more air AND fuel.

 

Sure that generates more power, and it's done by pushing the gas pedal.

Actually, adding more fuel and air in appropriate ratios, I'm learning, is a true art. The more I read about F/I, the less I feel like I know, but I've had a few good conversations with experts that are getting my head straight.

I think the original statement by GQ 350z implied that by freeing up exhaust gas flow, you somehow increase intake *air* flow, that wasn't compensated for with additional fuel to maintain that magic ratio of somewhere around 11.5:1 or 12.0:1. As far as I know, that's not the case. All of the factors that affect A/F ratio really exist on the intake/fuel side, not the exhaust side, but I could be wrong.

 

Yes, my mistake--I should have elaborated.

 

Not to be a stickler or anything but this is an actual X pipe:

http://cgi.ebay.com/ebaymotors/ws/eB...category=42610

The Greddy looks to be a 2->1->2, more or less a double Y pipe.

 

So, essentially, not true dual?

I'm heavily considering the Injen because of this, and really can't make up my mind.

The sound doesnt concern me, as long as I get similar gains before and after FI.

Ravi

 

That's what I'm gathering form the pictures I've seen. If you are going FI in the near future usually you want to get the most free flowing exhaust you can find. You will probably sacrifice sound and any NA power gains though.

 

Yeah, FI is easily a year away.

What would you guys do? I'm figuring I can just sell the Injen before I go FI. I want to have some modding fun lol.

ravi

 

Yeah, that's definitely an X-pipe, but from a fluid-dynamics standpoint, they probably do the same thing, they allow the exhaust pulses to collide, and they allow the pulse of one bank to affect the back-pressure of the other.

Anyway, I got my two runs on the dyno today. The better of the two showed 246.9HP (uncorrected).

After SAE correction, I pulled a 238.7 HP/ 233.1 Tq. I'm not sure how this compares to bone stock, but I'm guessing it's not that much better.

Anyone else have any dyno #'s for their N/A setup?

 

Damn, based on what I've seen that is in line with a stock Z's dyno numbers. How coud this be? I would hate to spend neary a $1000 only to have two nice cannisters on my back side (at least while I'm N/a).

ravi

 

I mis-typed above, the torque was off. I've edited to correct, and I've put this info in our other thread as well.....

As far as the seemingly low numbers, I don't know what to say. I guess it just goes to show that the numbers posted by the manufacturers are "best case scenarios".

 

You'd have two nice cannisters and a sweet sounding exhaust. I have the EVO2, and it is awesome. It opens up the undercarraige of the car which looks really nice.

Yes, I would consider the EVO2 a true dual setup. The cross-over pipe is beneficial or Greddy would have not incorporated it into the exhaust IMO.

If I didn't buy the greddy exhaust, I would have seriously considered the new HKS or APS exhaust.