black_phoenix

iTrader: (27)

The reason im making this thread is because lately i have seen some threads popping up on how the car would run with open LT headers.. so i thought i would share

So lately i have decided to modify my 98 trans am. Its an automatic with 2.73 gears, nothing special with descent pick up from the factory...

Anyway, im on a budget so ive decided to keep it simple. LT headers, Catted Y, stock catback with cutout, and a 3400 stall converter with 3.73 in the future. I have personally never done this before so i wanted to experiment a bit

So far i have Volant intake, ptb, and open cutout. Good start.

This sunday, my long tube headers have arrived and me and a couple of friends decided to install them, but since welding was required to install my cats, and Y pipe to the catback, i have decided to keep open headers with no O2 sensors (reason for no front O2's is because i have to order my extentions)... So I ended up driving my car back with just open headers home for about 25 miles

And let me tell this, for the ones who want to run their car with just open headers... dont! For the following reasons:

First: its terribly loud even on an ls1 with stock camshaft even at idle, loud enough to set off some car alarms. Under WOT, its waaaaaay louder. Example: As i was driving on the interstate, i see a rider on the Harley with loud pipes, as i goosed my car a little next to him he literally flinched... yes im a douchebag for doing this
When i was driving on the highway, the drone was pretty intense... enough to make coins in my cupholder jingle lol.

Second: Your car will not feel faster... but rather noticeably slower. Its all noise and no go, which makes sense since there is absolutely no backpressure

Third: If you drive past a cop, you will get pulled over and since i was driving late at night, i have not encountered any, thank god.

In conclusion, my car idles fine, but just unuseable on the street with no performance gains.

Later this week i will complete my exhaust set up as well as a stall following by a nice dyno tune, once i get my funds together.

Well, that was just my opinion, if you still wanna do it, noone is stopping you.

nissan 570sx

http://www.hondacivicforum.com/forum...ts-wrong-3064/
http://my.prostreetonline.com/forums...php?t-1639.htm
http://mechdb.com/index.php/Exhaust_back_pressure_myth
http://www.dsmtuners.com/forums/freq...kpressure.html
http://www.rx8club.com/showthread.php?t=28945
http://www.fullsizechevy.com/forum/g...sure-myth.html
http://my350z.com/forum/intake-exhau...k-for-n-a.html (the long post about half way down the page)
http://www.miata.net/garage/KnowYourCar/S4_Back.html

omarrakeen

iTrader: (2)

^ ...op your car felt slow may be due to wrong AF ratio AND loudness! i drove mine with open headers and i agree with u totally unusable lol

sscamaroburn02

iTrader: (14)

wow LOL!!

LeanPocket

iTrader: (6)

thx lol

RPM WS6

iTrader: (3)

Where is it that some people have gotten this crazy idea that backpressure makes power?

If you are down on power it's because you don't have front O2s yet, or any sort of tuning for the headers.

01ssreda4

iTrader: (96)

Back-pressure does create torque, or a more torquey feeling powerband. Anyone who has changed exhaust can feel the power-band move up.

SuperSport01

Get the o2's hooked up and drive it again. You'll get your answer.

ivan_key

Had to run mine to the shop with open headers, not a very fun ride

thunderstruck507

iTrader: (18)

It's more noise throwing off perception than anything.

I can open my cutouts and swear the car is running like crap, but up until a week ago when I removed the tail pipes over the axle (made the car extremely quiet) it would pick up a tenth and a half and over 1 mph at the track.

But yeah anyone running open headers on a street car is a moron. And anyone running nothing but pipe with no muffler or resonator has no tastes and must just like being loud for no reason.

LeanPocket

iTrader: (6)

sooo, whats the perfect combo?

Lt's, ory, catback?
Lt's, highflow cat, catback?
or some other combo?

Sorry, but i get way too many conflicting stories
https://ls1tech.com/forums/drag-raci...ss-pics-9.html
this guy uses open headers for the track, & a sweet setup an runs low 11's

lemons12

iTrader: (71)

My car went from stock with loudmouth to ms4 4400 stall and open headers for a weekend, felt slower. All the noise was throwing kymy perception off, it was still moving good.

Lts xpipe 1 chambers is my personal opinion.

bww3588

iTrader: (49)

bingo...

back pressure means your engine has to work harder to expel the exhaust gasses, thus making your car FEEL faster because it is working harder. ever wonder why your exhaust sounds mildly different under a large load than free revving at idle?

when i installed headers, and ran them open up and down the road a few times just for ***** and grins...i noticed i had lost low end TQ, but gained a bunch of power up top. that is just the characteristics of the exhaust being moved faster due to no back pressure, your engine can breathe more at higher RPM's.

black_phoenix

iTrader: (27)

i retract my backpressure statement then

black_phoenix

iTrader: (27)

definitely possible

zracer323

iTrader: (12)

^^This...my car seems slower to me with my cutout uncapped, but runs faster at the track.
I agree with the OP. I ran open headers to get my y-pipe welded up and it was rediculous.

Benjamin Russick

iTrader: (1)

Heh. I too ran open headers to the welding shop...awful experience. A tuned exhaust sounds so much better...

Starz T/A 17

iTrader: (6)

Front O2's control the fuel ratios so if you didn't have those in that would be the main reason it ran like crap. People unplug the back ones because those just control the CEL light to make sure the cats are working, but you HAVE to have the front ones hooked up for it to run decent

nissan 570sx

No. Back pressure is not what causes an increase in torque, the increase in exhaust velocity is what increases the torque. Back pressure is simply a byproduct of running smaller pipes, which is one of the methods of increasing exhaust velocity but it is NOT for the reason for the increase in torque.

If you really wanted to see evidence, bolt a plate on a set of header collectors with a 1.5" or so hole in it. You'll get a ton of back pressure from doing that but your exhaust velocity and flow are going to be killed and you're going to lose a bunch of horsepower.


back pressure = bad

RPM WS6

iTrader: (3)