New 3" Exhaust System, No Power.

[pentae]

Hey Guys,

My car has been at the exhaust shop for the last 7 days getting the following exhaust system bolted onto my stock GTR:

- 3" Stainless Steel Dumps

- 3" Fabricated Front Pipes

- 3" Mandrel Bent Piping

- 3" Hi-Flo Cat

- 3" Muffler

This is an upgrade from the stock exhaust system which was shagged.

I went for a 3" System because I believed that the low down torque and response would be better than a larger 3.5" sized system. The guys spent a lot of time doing it and there was a few minor setbacks (rusty old exhaust system was hard to get off the turbos etc)

The car sounded pretty good of course, so I jumped in it and the first thing I noticed was the complete lack of power. The thing feels as though its bogging down under full throttle, sure it has an underwhelming amount of life in the 4,000 - 7,000rpm top end, but anything under that and it is hopeless!

The popping is a lot louder and it just seems to be trying a lot harder for bugger all difference in performance.

Can anyone offer some light on my situation?

[pentae]

What i'm trying to say is that the car has about the same amount of performance as it did before, now it just sounds louder

Edited September 13, 2005 by pentae

[Buddy Club R33]

When I got my 3" catback exhaust installed the mechanic told me to reset the ecu and rev the car higher the next day. That seemed to do the trick.

[Bov]

The best exhaust on a Turbo is no exhaust. The reason we go large is to make the things work even better.

If you have performance problems I doubt its the exhaust causing it.

Cheers

[WazR32GTSt]

agree with bov...

something else has to have been altered when they changed the exhaust

i instantly noticed more power when i had a 3" made for my rb20..

Warren.

[pentae]

Thanks for the suggestions guys, I reset my ECU (unplugged the battery and stabbed the brake pedal several times, then reconnect it) .. mild improvement but still just as powerful as the car was before the exhaust.

The exhaust fitter said he had to slightly customise the dumps to accomodate the o2 sensor.. maybe its that. I'm dropping it back in tomorrow morning.

[Beer Baron]

out of interest what do the custom dumps look like? is there a particular reason you went custom over the available off the shelf dumps? is it possible the new cat is causing a restriction? what type of cat is it?

also have you had the car dyno'd before? if so dyno it now and see what happens.

Also, just out of interest how much was the exhaust? and mild or stainless?

[pentae]

They where off the shelf dumps, and other than the muffler the rest was custom.

Dyno, no, I havent yet. I already can feel a problem with the car, i'd rather take it in when its healthy! which i will do once this problem is sorted.

All up it cost $1700 at mates rates.

[wrxhoon]

You don't say if you still have the stock computer and stock boost .

If you have the stock ecu its probably running very rich .

[Sacony]

Pentae - I have the same sort of modification to my exhaust system except I have 3.5inch back from the cat, but I don't have any aftermarket dumps. I am running 14psi boost and this gave me an extra 60KW at the rears assuming standard is around 170KW. So you should be feeling a big difference! As for below 4000rpm didn't have the chance to drive the standard exhaust system, but mine is pretty sluggish too until i hit boost at about 3500rpm.

[MerlinTheHapyPig]

yeah, 3.5inch would have been better than 3inch. a smaller exaust will only rob you of performance, it won't give you any advantage in throttle respose or low-down torque.

In N/A's maybe, as backpressure is required, however in turbo's the turbo creates ample backpressure

If you are experiencing lack of power. TAKE IT BACK and tell the guy who installed it all. As they haven't done their job properly if this "upgrade" is giving you poorer performance.

[mr 32]

it could be your air filters i had k&n m's when i got my gtr went like crap till about 4000rpm put a set of apexi's on it now you can fell it at 2500-2750rpm

[RellikZephyr]

i had twin apexi air filters and SS dump pipes and 3in turbo back exhaust fitted to mine

HUGE difference

stock ecu and all that, the with exhaust and intake mods stock boost jumped to 14 psi

and can feel boost about 2700rpm full boost by just before 3500rpm

also i havent dynoed but will have just over 200awkws

so somethings wrong in urs

good luck

RellikZephyr