So...I just got off the phone with Dallas at WarpSpeed Performance.

I bought a new Y-Pipe from him, and we shot the shxt for a little while, talking about maximas and what not. He asked me what shape my stock cat-back is in, and I told him some minor surface rust, but in pretty good shape.

He recommended something to me that makes a lot of sense. There is apparently a flattened spot right after the resonator that is about 6 inches long, designed by Nissan for the simple reason of "clearance issues". He recommended a very cheap alternative to a cat-back, and that is to cut out this "flat" piece and replace it with a 2"-2.25" straight pipe, and that would earn me "roughly eight horsepower".

Question here is, has anyone done this and/or does this make any logical sense to anyone out there?

Would it be worth it to do this mod? I mean, if i really get ~8HP just by replacing 6" of stock exhaust, i'm thinking "screw getting a cat-back!"

LMK. Thanks,
-tyler

 

that isnt going to do anything at all.. i will NEVER trust warp speed again.. my buddy at work had a ****ty y pipe from them and not recently i had sent mine inf for repair of the flex section they send it back and its louder than its ever been before... im not even gonna mention that i had to pay for the shipping there and back..

man do urself favor get a greddy sp2 and all it a day... dont buy anything from warpspeed..

 

^^ hmm... he told me he's never repaired a y-pipe under the "4-year guarantee" warranty, as in all of them outlive the warranty...

unless you're referring to something else.

well...if i get screwed, i'm sure i can get a good bit of money back in the classifieds lol

 

i believe that bend is to improve torque down low, every since i have started messing around with the y-pipe and the rest of the exhuast i have noticed a slight decrease in torque down low, like way down low(1200rpm on down), i dont believe that little section is worth 8hp and the diameter of the exhuast plays a big roll in the output. Most aftermarket systems only net 8-10whp so that doesnt seem believable.

 

yea mine was 4 years and like 2 months.. i didnt even drive the car last winter or the winter before that... and it still rusted to crap....

 

I call .

 

ok.. why would i lie about that? Dallas told me the date it was bought.. it was out of warranty...

but you of course know better since you have seen my car right?

 

I wasn't talking to you. I was talking about the "cutting out the "flat" piece and replace it with a 2"-2.25" straight pipe, earning "roughly eight horsepower".

 

my bad bro.. i read the post way too fast...

 

haha wow that guy is a moron. that crimp is there to clear a bracket in the exhaust tunnel. straight piping it wont do anything, let alone give you 8 hp. a catback wont even give you that on a stock car. warpspeed is a joke. x2 for teh greddy sp2

 

wait... so greddy is twice as much of a joke as warpspeed, or are you recommending greddy?

either way, i fucxing love greddy, but i'm too broke lol

 

Anyone got a link for the greddy cat back ?

 

guess i shoulda said +2, i fuxing love Greddy too...

 

... im using apexi... that i got for free.. from my friends Accord.. i know, I know.. but it was acutally the best free thing i put on my car.. i replaced the everything from (including) headers back at the same time...

 

free apexi?

I KNOW YOU HAX!

 

why does every1 bad mouth warpspeed? ive had no problems w/ my y-pipes from them. and if you bought an ALUMINIZED STEEL pipe what did you expect?? steel rusts w/o snow/salt. itll rust from just sitting rust is steel oxide not steel and snow. if you spend the extra $50 and got the stainless you probably wouldnt have the rusting problem. but yea i dont know how its possible to get 8hp from losing a flattened piece of pipe.

 

i found this a couple days ago...i would get it but it only fits 95-6:

http://forums.maxima.org/4th-generat...low-miles.html

300 shipped is a fucxing steal IMO...scoop it up!

 

hey homermac, which apexi muffler do you have? N1? want a greddy SP2? lol

 

I don't have any problem with warpspeed (their SFCs were one of the best mods I ever put on my car) but the notion that removing that small crimped spot on the exhaust will give you 8hp is laughable. An entire catback on a bolton 4th gen won't give you 8hp, let alone that little tiny spot. Maybe 1-2hp.

 

Ok I am going to drop some knowledge for all you individuals that are still perplexed by the exhaust performance debate...

The exhaust is merely a path for the exhaust gasses to pass through. If you are running a stock motor, naturally aspirated, you are not really increasing the input into the exhaust stream so putting a huge exhaust on is detrimental, because the amount of volume that you can move through there is not simply a product of pipe diameter, but GAS VELOCITY.

For example, if you eject a quantity X of exhaust gas from your engine at a pressure of 50 psi into a pipe which is twice the diameter of the exhaust runner in the cylinder head, there will be a pressure drop of 50%, and therefore a deceleration of 50% (approximately). Also keep in mind temperature... heat = energy = pressure increase. Pressure takes the path of least resistance, so too much pressure in the exhaust will create back pressure or reverse flow, which is also very misunderstood. In naturally aspirated applications a bit of back pressure is a good thing, and creates a bit of reciprocation in the valve train, freeing up more torque at low rpm operation. In forced induction applications the rules change drastically because you are actually increasing the input into the exhaust because of more air/fuel mixture being combusted during the combustion cycles. So if you are running 8-10 psi with some larger injectors, it would make a lot of sense to widen your exhaust pipe diameter to prevent the back pressure caused by higher volume and temperature of exhaust gasses.

In summation, mandrel bent 2.5" or 3" diameter systems should only be used with forced induction applications or high compression built engines with upgraded fuel delivery that produce considerably more power than stock. For stock engines with "bolt-ons" a decreasingly stepped diameter setup or even crush-bent pipe setup is ideal, since the slight restrictions actually produce gas acceleration zones that will yield more effective exhaust gas scavenging.

As far as all this +8 hp business, it is absolutely ridiculous! An exhaust won't give you any horsepower but a decrease in back pressure might free something up, but that will depend on what condition your engine and catalytic converter(s) are in. You want power, swap your engine or go forced induction, don't spend $1000 on an exhaust system that will just make you sound different...

 

^if that is true how would u explain the 3.5s making more power and torque on 3' exhaust compared to 2.5. Even honda guys have been playing around with large diameters 3" and make more power then the standard 2.5s" im still thinking about testing a 3" exhaust on a 3.0 and seeing what happens there has to be some exceptions to those "rules"

 

http://www.motorvate.ca/mvp.php/522


I am surprised nobody mentioned this. This is probably where the 8hp figure was taken from.

 

If that is true? This is the law of physics my friend, the dynamics of gas velocity is not a philosophical debate. A 3.5 yes, but this is a 4th gen forum, so there are only 3.0s, if you swapped the engine, you should re-read my previous thread where I said that larger pipe diameters will only help you if you go forced induction or swap the motor to a more powerful one. And a stock honda engine like a b18 or something is not going to see ANY benefit from a 3" exhaust over a 2.5", in fact, there will likely be a LOSS of low-mid range torque. It seems to me that you did not understand my previous post.

A stock VQ30DE will begin to lose low-mid range torque beyond 2.5" pipe diameter. I have 2.5" piping in my header and y-pipe that connects to high flow cat (not test pipe) and 2.25" b-pipe and 2.25" exhaust tip and I noticed an improvement from when I had a 2.5" straight thru system.

 

^^ thanks for your insight

so, would you recommend 1) high-flow cat to 2.25" catback, or 2) high-flow cat to: (stock resonator, 2.25" b-pipe, stock rear section, 2.25" tip on a stock muffler)?

i'm not sure there's enough of a difference. the muffler on any aftermarket catback will be fart-can style...well...except for pacesetter .

did you use the stock muffler and weld on a new tip, or is there some other brand you would recommend?

pleasedon'tsaydynomaxpleasedon'tsaydynomaxpleasedo n'tsaydynomaxpleasedon'tsaydynomax

 

its mostly the K-series guys that are seeing better numbers moving up to larger diameters. 2.5" piping is the standard for most cars and their aftermarket exhaust systems. It could be because they get in there element at such high rpm aswell contributing to the gains. And its not like those guys have enough torque to notice a loss or gain.

I dont know the extent of ur exhuast if it is stock b-pipe with an aftermarket axle back or what have u, but i will say when i moved to the current set up from a y-pipe on stock everything else to, the test pipe'd and Apexi, the only think i noticed and it is barely noticeable is at extremely low rpm, like below 1100 there is a slight loss in torque, everywhere else it has improved, up top especially

 

I would generally agree with Warpspeeds recommendation. That crush is bad for flow, but I wouldn't expect it to make 10hp. 2-5, probably. But only at high RPMs.

 

i believe LOR1DA is correct in his suggestion to only use 2.25" for the cat-back if you're N/A. i have a 2.5" cat-back and i'm sure the decreased flow velocity is why i don't feel any gains from it

 

On paper (theory), the upper limit of 2.25" piping is about 185hp, whereas 2.5" piping supports between 180hp to 220hp. Don't forget that the cat also puts more heat into the exhaust charge (because it's burning fuel), requiring a slightly large pipe size, so that pretty much seals the deal.
I personally would not run anything less than 2.5" mandrel on a VQ30, and would run either 2.5" or 3.0" on a VQ35 depending on my goals for that car.

 

you are mostly correct but your calculations are incomplete. you gotta remember a couple of things:

1. exhaust gases cool as they flow through the the exhaust system. if they didn't you'd need a cat-back just over 2.75" in diameter. and the cat is just a filter, slowing down gases, it does not heat them up.

2. while yes a larger pipe does support more power, it does not necessarily give it.
- in a FI application, the larger pipe means that more exhaust can be pushed out of the way.
- in N/A engines, the smaller size (appropriate to the displacement) will increase flow velocity and create a sort of vacuum in the pipe to "pull" the exhaust away from the cylinders. that's why equal length exhaust systems perform better, they provide a strong, smoother vacuum effect.

and 3. mandrel bent is good, but not absolutely necessary if you're just N/A. it does give a nicer sound though .

 

So, do any of you all think a y-pipe and a high flow cat will make any noticeable diffrence??

 

have u read the stickies yet?

all the answers are in there.

 

i have done this

about a year ago when i was building up my car i noticed the pipe crushes when i was putting my Greddy evo II in. i have full access to a welder and a shop so i decided to try it out. i welded up a new pipe the same diameter as the stock piping and put it in. i did this after running the car with the greddy installed so i knew how it was before. after installing the new piping (deleting the resonator and crushes) there was honestly no real difference that i felt.

 

y pipe will give you a slight difference... cat will do nothing..