BoostFrenzy

Did you notice any gains? did you have any spiking/creep issues? (main cat left installed)

looking for CONCLUSIVE evidence that it's worth it

nopistons94

look subaru i told you that you MIGHT have boost spiking issues with a catback installed it depends on the car. My car spikes with the mods and catback that you listed on transition between the turbos (4500 RPM) to 11 or 12 psi but I don't have a boost controller, just a ECU that can run enough fuel to 14.4 PSI so.

Gain wise I don't think it's much just cooler tone but I could be wrong since I've never drivin an FD with a stock catback

BoostFrenzy

yeah i know i'm just looking for some collective expierences, i always get like one MAYBE two people to respond

PhoenixDownVII

I've gotten a lot of odd feedback from those practicing the "3 Mod Rule" of Intakes/Catback Exhaust/Downpipe before ECU, somehow safely.

My car currently has a high flow MP and a CB, and doesn't spike at all, ever, even in freezing temperatures. I am a bit weary, as I am about to have a DP and revert to stock main cat (still keeping the M2 Dual catback), that buying intakes will cause "Some" spiking.

But being the OCD, **** retentive (spelling?), elitist ***** I am, I will not tolerate any movement from "near perfect".

And that feedback I've been getting from those who have done just the 3 flow mods is that "some" spike/creep occurs. "Some" is a little to much IMO, so why bother playing that game? Get an ECU/Boost controller, I know I will before the intakes arrive (or at the same time :P)

keynote22

Stock port & stock twins.

intake, dp, high flow cat, cat back = no creep for me

intake, dp, stock cat, cat back = no creep for me

intake, dp, mp, restricitve exhaust = moderate creep for me controlled by commander

intake, dp, mp, cat back = massive creep for me...spiked edge of my gauge and beyond

current set up = Intake, dp, high flow cat, gretty titanium exhaust = no creep


Gains? yes. Anytime restriction is/was taken out there was a gain in the butt dyno. The more restricitve the piece taken out...the more the gain. The lower restriction also caused the turbos to spool faster which also resulted in a nice change in the feel of the car.

keynote22

Food for thought: the three mod rule is more about too much HP with insufficient fuel to handle the gains causing the motor to pop. More mods = more power= leaner mixture on a stock ecu = careful. It really depends on the mods and what order they are done in. Boost creep is a different issue not really under the 3 mod rule IMO


I believe the general rule is a cat back will add 5-10% hp gains...but it really depends on what you are replacing. Racing beat claims 12 hp with a stock system and their fairly restrictive cat back.

adam c

iTrader: (2)

I had my Cheap Bastard intake, and a DP before buying my RB catback. I didn't feel much difference after intstalling the catback.

1wide7

iTrader: (1)

with hks intakes, hks carbon ti, and a downpipe = spike

i could not even think about boost it spiked as soon as the turbo's spooled but a manual boost controler brought me back to 10-8-10

RE Suzuki

Intake + DP = no problem
Intake + dp + Catback = little boost spike

dgeesaman

iTrader: (7)

I had K&N in a stock airbox, efini y-pipe, and downpipe. Still a normal 10-8-10. Added an old style RB Dual cb, and it went to 12-8-12. No creep or spike. Currently undergoing unrelated work (I will install a bigger wastegate pill since 12 is very dangerous.

Dave

Retserof

iTrader: (1)

My 94 is stock except for a Pettit downpipe. I wanted to add a RB catback, but with just the downpipe, I got about 1/2 lb of boost creep and almost 2 lbs of spike at 5.5K rpm, just after transition. In cold weather, I hit the overboost fuel cut at 5.5 to 6K rpm.

I went to a Holley #72 jet to replace the stock restrictor pill in the wastegate actuator hose, and now the post-transition spike occurs earlier, around 5K and is only about 1/2 lb. I think that the boost creep after transition is less too. I think I could install a catback now.

keynote22

I guess I need to add that I adjusted my wastegate duty cycle and turned the boost up a bit with my power fc during my various trials....although I was booting above stock levels, I was not exceeding my set points except where noted.

FlameThrowingRotary

When I put the greddy cat back on mine it gained 2/10ths in the quarter and like 4mph.

chris7777777

Hey guys,

Ive been searching and haven't found any posts about replacing just the main cat alone.

Reason is I want to maintain my car in stock form. I had to do the downpipe last year because my pre-cat was deteriorating. Now I currently have stock intake, stock main cat, and stock exhaust, with the 3" downpipe installed for reliability.

I really am not interested in making huge horsepower gains as I like my car as fast as it is now. Problem is I think my main cat is clogged up and that I have to replace it. When I rev the car, it comes back down very rough and can hear the exhaust rattling around the middle section of my car.

If I go high-flow cat, will I have boost spike and creep issues or can I be safe with stock intake, stock exhaust, DP and just new cat. Or should I just replace the cat with a non-high flow type.....is that being overcautious.

#2.....same question but keeping in mind I would be interested in the RB catback exhaust one day for looks only. I don't think I will ever change my stock intake.

DaleClark

iTrader: (55)

Just buy a good stock main cat - they should be a dime a dozen. Really doubt it's something wrong with your cat, though - they're quite hardy and you have barely any miles on the car. I'd leave it be and look elsewhere for your problem.

Dale

wutanec

Hey fellow Michiganian . My car had intake dp and the boost held perfectly. I put on exhaust few weeks ago and now it spikes to 11 or 12 psi right before secondary kicks in.

Narfle

iTrader: (16)

I noticed a little gain with the addition of a catback sometime in 2003 but as I recall my stock catback was thrashed and it was worth it for me just to make it sound nice compared to my rusted out stocker. You shouldnt have any problem with boost control issues but anything past this and you definitely will need a controller. So catback -> boost controller for you.

chris7777777

Thanks for replies so far guys.............I thought without touching the intake, leaving a cat in and RB exhaust would leave enought restriction for me.

t-von

iTrader: (8)

Same mods as you! I had slight boost creep with Cheap Bastard and DP with stock catback. Enough for me to buy and make the Home Depot manuel boost controller. I get even more creep venting the stock BOV. I guess some people have stock cats & catbacks that are less clogged than others? More clogged less creep, less clogged more creep.

t-von

iTrader: (8)

The water steam cleaning method does wonders for keeping the stock cat from clogging. I should have taken pics of mine with over 103k when I had my PPF frame down a couple weeks ago while I was doing the PPF reinforcement.