jng1226

The search function is still not working for me, so I had to post again.

Is 3" or 75mm piping to big for an NA car without headers/cams? I know backpressure is important for low-end power with NA cars. If I eventually plan on headers/hi-flow cats/cams, does it make sense to get the 3" piping now or will I suffer to much low-end losses?

Thanks in advance.

Gsedan35

iTrader: (10)

On the surface the idea does raise the reg flag concerning back pressure or more importantly, exhaust gas velocity. At what point to you gross the line does tubing diameter become a liability vs a asset. We can look to the Nismo system for out anwser. The Nismo uses 76mm pipe diamter. Here are comment's gleamed from looking at the dyno comparo done by 350Zsport magizine.

Nismo (car 1) = 6.3 Hp - 4.5 ft/lbs torque (peak values)
Developed torque and Hp over wide rpm range. Torque increase starting at 3000 rpm. Most HP increase from 4800 rpm to redline. No power losses below 1800 rpm. 54lbs.

Now, let's look at the comments for three true dual systems.
Look at Hp and torque and WHERE it's made.

Borla (car 2) = 8.2 Hp - 2.7 ft/lbs torque (peak values)
HP increase from 5500 rpm to 6500 rpm range. Lost HP & torque below 1800 rpm. 60mm pipe. Weighs 52lbs.

Stillen (car 1) = 8.1 Hp - 7.3 ft/lbs torque (peak values)
Hp and torque increase starting around 3000 rpm to redline. Lost a little Hp & torque below 1800 rpm. 60mm pipe. 74lbs - 10 lbs heavier than the stock system.

Injen (car 1) = 7.6 Hp - 5.1 ft/lbs torque (peak values)
Small torque loss at 2800 rpm. Torque gain starts at 3300 rpm. Small Hp increase starts at 3300 rpm, maxing out from 5800 rpm to redline. Major loss in Hp and torque below 2200 rpm. 49lbs.

ares

iTrader: (2)

a single 3" pipe should be fine.

Gsedan35

iTrader: (10)

Oy good point, single 3"

Just like any good exhaust system. Their are way's to make power that obey flow dynamics and their are things that cost power. Most exhaust's here are picked because of sound and how the tips look.

ares

iTrader: (2)

because as you posted the best is 8.2, worst is 6.3. and to choose anything based on a 1.9hp difference is absolutely stupid. they are basicly equal. independent dynos may vary, but the best comparison we have is shootouts done by mags, and they show very little variation.

use sound, quality, and appearance to choose.

jng1226

Thanks for the replies, that makes sense, I just needed to be sure before I pulled the trigger. I'm looking at the Top Speed Pro-1 exhaust. It comes in 2.5" and 3.0" but the deal I'm looking at is the 3" and wondered if it may have drawbacks for my current situation (no mods as yet).

If the darn search function was working I would be looking up opinions on this particular exhaust!

Gsedan35

iTrader: (10)

And yet, that same dyno comparo show's what I'm talking about, the 5Zigen lost power, don't buy exhaust on sound and tips only, you might end up with 5Zigen type results and a lighter wallet.

5Zigen (car 2) = (-3.4) Hp - .02 ft/lbs torque (peak values) Lost Hp, no real torque gain. Most expensive. Loudest. 58mm pipe. Lightest
@ 25lbs.

jng1226

Do you mean a 3" single "Y-pipe back" type system, where the mid-pipe is 3"? If you look at the picture I posted, this is what I am referring to.

From what's been discussed, it sounds like a 3" DUAL (replacing the Y-pipe with an individual mid-pipe might cause more low-end losses than a 2.5" system of the same type, or a 3" single mid-pipe type system such as the one in the picture.

Thanks for the clarification.

DaveO

I've noted that your exhaust system priorities are indeed different than mine. Not wrong, just different.

Esentially I agree with your statement "...to choose anything based on a 1.9hp difference is absolutely stupid." However, IMHO, to buy an exhaust system only based on peak horsepower is not the way to go... at least for a street driven vehicle. (I won't say "absolutely stupid").

As the original Sport Z Magazine's Exhaust Shootout article indicated, each of us should research, prioritize and decide which system is "right" for us.

My personal priorities differ as follows:
1 - Power... best across the board torque, peak torque, across the board hp and finally peak hp.
2 - Quality & Sound
3 - Cost & Warranty
4 - Ease of installation

Before continuing, an observation... I find it interesting that my original Sport Z Exhaust Shootout notes, or portions thereof, still show up from time to time. Occasionally they're edited to reinforce or justify the poster's buying decision.

Here's what I originally wrote (edited for clarification).

After reading the [Sport Z Magazine Exhaust Shootout] article and "studying" the dyno charts I recorded my impressions and rated the systems based on my priorities [noted above].

They used two cars (2% Hp difference).
Car 1 Baseline = 233.2 Hp - 222.6 ft/lbs torque
Car 2 Baseline = 237.5 Hp - 224.0 ft/lbs torque (stronger engine - lighter wheels)

All manufacturer's systems Hp and torque numbers were lower than advertised. Not a surprise. [ECUs not fully adapted?]

Borla (car 2) = 8.2 Hp - 2.7 ft/lbs torque (peak values)
A top end system. Little HP increase until the 5600 rpm to 6500 rpm range. Lost HP & torque below 1800 rpm. 60mm [actually 58mm] pipe. Weighs 52lbs. 1 million mile warranty. Installation - Hard (17 [18] pieces)

5Zigen (car 2) = (-3.4) Hp - .02 ft/lbs torque (peak values)
Lost Hp, no real torque gain. Most expensive. Loudest. 58mm pipe. Lightest @ 25lbs. 1 year Warranty. Installation - Medium

Stillen (car 1) = 8.1 Hp - 7.3 ft/lbs torque (peak values)
Hp and torque increase starting at 3000 rpm to redline. Lost a little HP & torque below 1800 rpm. 60mm pipe. 74lbs - 10lbs heavier than the stock [350Z] system. Lifetime Limited Warranty. Installation - Easy

Injen (car 1) = 7.6 Hp - 5.1 ft/lbs torque (peak values)
Small torque loss at 2800 rpm. Torque gain starts at 3300 rpm. Small Hp increase starts at 3300 rpm, max Hp from 5800 rpm to redline. Major loss in Hp and torque below 2200 rpm. 49lbs. 1 year Warranty. Installation – Easy

Nismo (car 1) = 6.3 Hp - 4.5 ft/lbs torque (peak values)
Torque increase starting at 3000 rpm. HP increase 4800 rpm to redline. No power losses below 1800 rpm. 54lbs. 3 years, 36K miles if installed by Nissan dealer. Installation - Easy

My ratings for the 350Z/G35 Coupe Systems [based on the article with some limited experience with two of the systems]:
1 - Stillen
2 - Injen
3 - Nismo
4 - Borla
5 - 5Zigen

If B&B had been included, I would rate it ahead of 5Zigen based on the Nissan Performance Mag 350Z project car results.


Why I rated Stillen's system the overall performance winner. Based on the article's dyno charts, it had the highest average and peak torque and highest average Hp across the broadest rpm range. In this test it was second in peak Hp (Borla's was one-tenth Hp higher).

I rated Injen's system second and Nismo's third because of their good across the board Hp and torque. I rated Borla forth due to it's limited midrange power and hard to install rating, and 5Zigen last due to the fact that it lost Hp.

As a final note: I came across a 350Z Borla vs. Stillen exhaust system comparision done on a different dyno and on a different day. The results? Borla's system did much better in midrange power, however Stillen's system still provided higher average and peak horsepower and torque.

Is the Sport Z Magazine article the final word on these systems? Of course not, but I found it a good starting point. Is this information and my opinions worth very much? It's up to you to decide.

[Let the flaming begin.]

DaveO

KJY9

I'm running that exhaust with a Fujitsubo Y-Pipe (3" collector), high flow cats and crawford headers. I can't run it with the silencers out if I want to hear myself think.
Only 2hp difference with silencers in (on a dyno within minutes of each other).
I like it alot...it's fairly quiet until you get on it, then it screams. PM me if you want a video of the exhaust at the track to hear it and I'll email it to you

jng1226

Sweet! That's almost the exact setup I'm planning for (except Japtrix Y-pipe and Kinetix Cats). I would love to get all the vids you have - you've got PM.

Thanks again for sharing!

Regards,

Jeffrey

KJY9

YGM