LT1_King

iTrader: (1)

hey guys i have a 94Z A4 with stock manifolds. i deleted the cat cause it wa clogged. i put a strait pipe in place of it and i have the LM1. performance wise it took ALOT of my power down and didn't even gain alot up top. the only reason i took off the cat was cause it was clogged. has anyone ever done this and if you have what are your opinions on it? i think its not worth any gain. it just hurt my performance. i don't like it. i think i'm gonna put a high flow cat for a while till i get my LT's.

3pnt4maro

iTrader: (2)

seems to me you lost your backpressure cause the lm is straight through

LT1MAN

iTrader: (6)

i had mid length headers when i gutted my cat. i didn't put the straight pipe in tho i just left the shell of the cat, i felt like i picked up a few plus a few extra exhaust tones, but i definately did not LOSE power.

LT1_King

iTrader: (1)

see but i'm running stock manifolds. their flow really sucks. lol. yeah i understand with some headers you don't need a cat cause headers are WAY better flowing than manifolds.

LT1_King

iTrader: (1)

yeah i think i lost ALOT of back pressure cause down low it just flat out sucks. i thought i was gonna gain alot up top but i didn't gain much. lol. i'll be putting a high flow pretty soon.

sdm1234

iTrader: (8)

with the manifolds not flowing too well, you wouldn't lose power due to lack of backpressure. there's already significant amounts of backpressure through the manifolds. how do you know you lost a lot, down low? maybe you heard a different/maybe louder exhaust note and just EXPECTED more but didn't get anything...

1bdbrd

iTrader: (12)

loss of back pressure should result in a gain in power over the entire rpm band. what he might have lost was exhaust scavaging. that will result in lower power. but going from a clogged cat to a straight pipe, unless its a smaller pipe,, i would imagine wouldnt cause that.

LiENUS

I wasn't aware you were running a carbureted LT1, why'd you abandon the fuel injection? Who did the tuning of the carb and how much did the whole setup cost?
http://www.club240.com/forums/showpo...11&postcount=3

3pnt4maro

iTrader: (2)

but wouldnt a loss in backpressure cause a loss of torque down low which is why he thinks he lost power

94CamaroZ28SS

I have a 94 z28 A4, I did a cut out and i gained 32 RWTQ but lossed 4 RWHP.

before Cut out and MOROSO CAI 268 RWHP & 303 RWTQ

After the Cut out and Moroso CAI 264 RWTQ & 335 RWTQ

LiENUS

A loss of velocity would cause a loss of torque down low. A loss of backpressure will increase power throughout the rpm range of the engine, including down low. Read the link I linked to.

UnitZ28

if they were electric i would close them right after my tq rpm peak so you might get the hp up top back where you need it

LiENUS

4rwhp is attributable to error, if you dyno the same car 3 times back to back not all 3 results will match.

LT1_King

iTrader: (1)

see the cat wasn't completely clogged it was getting there. see it felt a whole lot stronger. it was a high flow cat that the previous owner had on there. the pipe that i put in place of the cat is a 3" pipe.

LT1_King

iTrader: (1)

the cat wasn't completely clogged but it was getting there. the pipe that i put in place of the cat is a 3" pipe. the throttle felt a whole lot different once i put the strait pipe through. see the way i noticed the difference was because me and my brother both have the same exact car with the same gearing. we would be side by side every time we would race. now he just beats me like nothing. that's why i noticed a big difference. see and when ever i gave it full throttle it didn't feel like it started pulling till about 2800 rpms.

Revelation Z28

iTrader: (10)

with a V8 backpressure is your enemy. with a 4 banger, you need that back pressure, but not that much of it.

3pnt4maro

iTrader: (2)

ok well i was just saying..that was my understanding on it..not exactly a rocket scientist or nothing..thank for clarifying

LiENUS

back pressure is your enemy for both a V8 and a 4 banger. A v8 is just two 4 bangers joined together, dodge even produced a slant 4 that was nothing but a hemi v8 cut in two (not in any production vehicles). If back pressure was truly a good thing then we would have butterfly valves in our exhaust systems that are almost closed at low rpms and slowly open up as the rpms increase. The only systems which do do this do not use butterfly valves but rather use something to alter the effective diameter of the pipe or are only closed at certain cam events.