I thought that exhaust was suposed to give MORE power?

[focusedrage]

Ok just the other day i added a 3" cat back system from extreme motorsports to the following mods:

Injen Intake
Magnacore Wires
NGK Plugs
BCS mod

Now the car is totaly different... i have to pushe the pedal down a lot farther to make it do what it used to, and i can just put the pedel at a certain point, it like stops revign up at about 4000... i mean when i want to go fast it works pretty good. WHat is the problem?

Did i shift the powerband?

Also when i put a boost controler and a gauge in will iu beable to kick up the boost enoguh to compensate?

Sounds great though, thanks for any help

 

[boostin97talon]

Running a 3" catback with the bcs mod is not a good idea. Your boost is probably from 17 to 19 psi with spikes around 22 psi. I read about that happening, and have had the same thing happen to me. Either put the restricter back in the bcs, or get a boost controller and gauge asap.

 

[doug]

Originally posted by focusedrage
Did i shift the powerband?

I think so-- 3" systems are said to cause a loss of low-end torque. That's the main reason I went with a 2.5". On my A/T, I need all the low-end torque I can get.

 

[froodawg]

Hey you gurus, back me up on this.

My take on it is this: Exhaust by itself isn't necesarily that much of a boost ... unless you take your engine to the limit. What you're doing by expanding your exhaust line is increasing the amount of 'potential' your car has.

Understanding this, you know that if you go WOT you'll see more gains, but if you drive it like you got stock you'll see a reduction unless you've modded your intake/cams/injectors/fuel pump etc.

I've got the same deal going on ... understand this.

When I installed my K&N FIPK (the first mod I did), I thought I #@%#@%#@%#@%ed my car up because my turbo spooled faster and didn't pull as hard. I've come to understand it's because it made my turbo spool faster (which I DID notice) and consequently top out at a lower level ... or perhaps the same.

What you have to understand is that when you expand your exhaust outlet, you're simply giving yourself more room to breathe. If you go WOT, you're gonna notice some gains ... but unless you mod some other parts you ain't gonna see jack.

 

[RedTurboEclipse]

u just got the catback? u still running stock o2 housing dp cat..? imagine if you had a full exhaust system.. woo hoo..

 

[focusedrage]

now would a turbo xs manual boost control just replace the bsc? oh belive me i will be gettign those gauges and things soon... how might i get back some low end?

 

[focusedrage]

oh wait, i thought the stock bov leaked so even if i was getting odd boost it woudl only end up at 12psi?

 

[Antilles]

Yeah, but thats a cookin 12psi. Get a MBC and you'll knock less and make more power.

 

[cucumber]

Yeah, it's imperative that on 2G cars the first mod you perform is a BOV. I suggest a 1G BOV, but I went with the Greddy Type-S due to its "bling-bling" factor...j/k

When you put that exhaust on, it's not upping the boost. You are leaking still at 12PSI, and now that you have a 3 inch exhaust, you are loosing that backpressure, so yes, it probably does feel slower.

In essence, purchase a BOV, and everything will feel alot better.

 

[CBgst]

The very first mod I recomend is the uicp and BOV. If you don't do that your waisting your time with the other mods because you can't hold boost above 12psi. As far as your exhaust a cat back helps some but the stock o2, down pipe and cat are in front of that so the exhaust is getting slowed down before the cat back. You don't loose bottom end with 3' exhaust either. The turbo provides all the back pressure you need. The bigger the better. Do the uicp and BOV then get the rest of your exhaust and you will see a big difference. That's how I did my car and that's my opinion. I didn't loose any bottom end with my 3' exhaust I got gains on the bottom and top.

 

[Tevenor]

2 phrases that you should take to heart:

If it can't breath, it can't make power. Get rid of that stock CBV (BOV) as soon as you can.

If you can't get it out, you can't get it in. The catback is a help but you still have a restrictive downpipe.

As far as the 'loss' of power, I am not sure. Did you JUST do the catback at once?

As far as 'low end grunt', thats a good theory on NA cars, but on a turbo car, your power is made by the turbo. The expectation is that off-turbo is going to be less than on-turbo. You can minimize the affects but the goal is to maximize the on-turbo, not the off.

 

[focusedrage]

"Did you JUST do the catback at once?"

what, jest i did put the cat back on at one time...? any way yeah all of your advice is helpful i do plan on getting some greddy icp and bov soon buth jese that plus a mbc and gauges and stuff, lota money... but hey my baby's worth it

 

[doug]

One of the very FIRST mods you should do is a BOOST GAUGE. Otherwise, how can you tell if you're doing something to your car that's raising boost to dangerous levels? Sure, just adding a catback won't blow your car up, but you need to add a boost gauge before you do anything to your car that will raise boost levels higher than stock.

 

[Eclipsed]

"you are loosing that backpressure"

You make it seem like a bad thing. You don't want backpressure! The least amount of back pressure the better. You don't need backpressure at all. What people really should say is that they want a high exhaust stream velosity with the lowest amount of back pressure. If you open up your exhaust you'll probably lose some low end torque with you stock turbo but belive me you'll gain high end. With a bigger turbo you dont lose any low end. With my alpha I pull alot harder then I did with the stock at low end anyways!

"I think so-- 3" systems are said to cause a loss of low-end torque. That's the main reason I went with a 2.5".

Its almost impossible to have to big of and exhaust on any turbo car. The turbo provides the stream velocity you need. If you have to big of an exhaust on a NA car then you have a low stream velocity because it doesnt have any where to stream to it just builds up and eventually goes back into the engine creating more back pressure.

 

[Axis187]

remember that you need some backpressure so your intake valves can open up again. I would say that a 3 inch exhaust is meant for a car with a large turbo running higher boost. When you are actually cramming that much air into your engine than you should open up the exhaust.

 

[mrmadmax]

Originally posted by Axis187
remember that you need some backpressure so your intake valves can open up again. I would say that a 3 inch exhaust is meant for a car with a large turbo running higher boost. When you are actually cramming that much air into your engine than you should open up the exhaust.

WTF?? As was previously stated, you do not need backpressure. Your intake valves are opened by your intake CAM last I checked.

In general, a larger exhaust system decreases exhaust velocity (stated earlier), which tends to reduce/reverse the scavenging effect (hence power loss) at lower RPM's. In a turbo DSM, however, I have little experience with exhaust mods, so you'll have to wait for one of the wisemen to chime in...

 

[mrmadmax]

oops, damn double click...

 

[Tevenor]

If your turbo is not the biggest restriction in you exhaust system, you have issues. The turbo provides more 'backpressure' than any 2" exhaust system.

You do not need 'backpressure to open the intake valves'. This is silly, at least for a 4G63 engine. You have a charged air mass on the intake side and a huge restrictor (the turbo) on the exhaust side. This is not an NA car.

 

[focusedrage]

yeah i now understand, now that i have realy driven it... i know, when i slam the peadle down it GOs, thats wear the power is. but yeah i ordered soem hgauges and a boost controler so ill be good to go soon...

Now i know crazy powereful NA cars go BANG BANG BANG when they let of the gas, do turbo cars do that? or is it just the PSHSHSHSHHS from the bov

 

[Axis187]

#@%#@%#@%#@% I completely forgot about two very important parts about the engine. Didnt mean to confuse you.

 

[froodawg]

Hey Rage,

Is the BANG BANG BANG you speak of possibly due to backfires? High HP engines (turbo or N/A) will backfire if the exhaust is too rich as it exits the manifold ... letting off the gas quickly or downshifting will increase the temperature and ignite your exhaust.

BLANG BLING BANG!

 

[focusedrage]

WHAYO, yeah i think thats how it works...

My understandign is that when the throtle plate closes, the deceleratign cylanders greated a suction in the exhaust that pulls oxygen rich air into rich exhaust gas = expolsion, i love it, when i went to the grand prix, i wet my pants it was so lound, jk, but still it sounds like there are deamons deep in the heart of the car

 

[custom240sx]

I am putting the APEXi N-1 turbo back on my car. Cant wait till i have no more back pressure. I had the n1 on my 240sx and it was a 3" system. No power below 4 grand. Well that was also with 13:1c/r and 6000$ in head work