View Full Version : Any noticable hp's on y-pipe?
lucky
12-11-2002, 08:00 PM
Please someone tell me if they got any noticable hp gains off the y-pipe?
DemonSVT
12-12-2002, 04:00 AM
Yes.
SLaPiNFuNK
12-12-2002, 04:56 AM
it would come mostly because of the either gutted or high flow cats in the y pipe...
lucky
12-12-2002, 09:24 PM
Well, i already gutted both my pre-cats and main cat. So is it worth buying still. And is it true that gutting the main cat can cause hp loss at low end rpm's?
DemonSVT
12-13-2002, 03:31 AM
Originally posted by: lucky
And is it true that gutting the main cat can cause hp loss at low end rpm's?
Yes. At any rpm actually!
ShinyBlackCat
12-13-2002, 04:09 AM
Originally posted by: DemonSVT
Yes. At any rpm actually!
Why would removing a restriction in the exhaust cause a loss in power?:confused:
PacmanTravis
12-13-2002, 04:17 AM
so, a y pipe with removeable cat is useless?
SLaPiNFuNK
12-13-2002, 07:51 AM
so then gutting the PRE-CAT good...
with no cats on the Y pipe = bad?
CougarDemon
12-13-2002, 11:36 AM
precats is ok. main cats is bad because the motor needs some back pressure to run properly.
PacmanTravis
12-13-2002, 01:51 PM
precats is ok. main cats is bad because the motor needs some back pressure to run properly.
Then why would yodude bother offering a y pipe with no cat and with removable cat?
Gutting precats is OK - chamber close to exhaust ports functions as expansion chamber for superhot gases sucking/scavenging them from exhaust chamber,
Gutting main cat bad because large increase in pipe diameter will slow exhaust gas velocity. It does reduce backpresssure which is good but this benefit is cancelled by drop in velocity.
Putting a pipe in place of cat OK because velocity is not slowed, backpressure drop benefits can be realized.
CougarDemon
12-13-2002, 03:11 PM
correct me if i'm wrong but you need a certain amount of back pressure for the car to run right.
mcon99
12-13-2002, 03:31 PM
WRONG
backpressure...ahahahahhaha.. ya right.
it is about FLOW and VELOCITY
CougarDemon
12-13-2002, 04:06 PM
i dunno this post is still a virgin so we'll see. i always thought you need back pressure for a better runnig car. yes it may be faster but then look at it this way if you run your car without a exhaust or y-pipe or anything how long ya think your cars gonna last running good? not long at all. i think i'm right. not a flame war but i was always told and heard people who know about cars you need some back pressure in your car for it to run good. i'm talking running good here. not speed
lucky
12-13-2002, 10:57 PM
Back pressure is a OLD wise tail my friend. don't listen to you grandfather when it comes to motors (just kidden w/ you). But, i do agree w/ the fact that gutting the main cat can cause some lose. But what does the car sound like w/ a straite pipe???
CougarDemon
12-13-2002, 11:29 PM
Originally posted by: lucky
Back pressure is a OLD wise tail my friend. don't listen to you grandfather when it comes to motors (just kidden w/ you). But, i do agree w/ the fact that gutting the main cat can cause some lose. But what does the car sound like w/ a straite pipe???
true. i'm looking at it in the sense of it will work but isnt healthy for your car but all and all what mod or poormans mod is. yes given the mods are made for the wear and tear but other things in your car you dont replace arent so basically your damned if ya do and damned if ya dont...heheh
DemonSVT
12-14-2002, 03:40 AM
Originally posted by: DanN
Gutting precats is OK - chamber close to exhaust ports functions as expansion chamber for superhot gases sucking/scavenging them from exhaust chamber,
Gutting main cat bad because large increase in pipe diameter will slow exhaust gas velocity. It does reduce backpresssure which is good but this benefit is cancelled by drop in velocity.
Putting a pipe in place of cat OK because velocity is not slowed, backpressure drop benefits can be realized.
Very well stated.
To answer the backpressure myth
..ANY backpressure is bad... It's all about velocity & scavaging.
lucky
12-14-2002, 06:13 PM
Thanks you guys!
IamSPDRCR
12-14-2002, 06:29 PM
Gutting precats is OK - chamber close to exhaust ports functions as expansion chamber for superhot gases sucking/scavenging them from exhaust chamber,
This is the biggest urban legend of them all. An expainsion champer on a 4 stroke engine serves ZERO purpose. If our Cougars ran a 2 stroke engine then an expansion chamber would be needed.
soooo.. what you're saying is, i need a lawn mower engine in my cougar so i can use the exhaust manifolds as expansion chambers? man that could work, lemme give weaponr a call so they could copy a briggs and stratton 2 stroke and sell it as the 'mad power yo-yo!' :)
IamSPDRCR
12-14-2002, 07:05 PM
Let me clarify myself a little more I'm not trying to be a prick to DanN. The is reasons why a 2 stroke motor needs an expansion champer and a 4 stroke doesnt. If you chose to gut your pre-cats then by all means go and do it but don't think that your getting something extra by the means of an expansion champer. If anything it will hurt your performance then enhance it. I will try to explain this the best I can.
Four-Stroke:
1) Intake (piston goes down, intake valve open)
2) Compression (piston goes up, both valves closed)
3) Power (piston forced down by expanding gases, both valves closed)
4) Exhaust (Piston goes up, exhaust valve open)
You'll notice that there's only a power stroke every other revolution.
2 Stroke:
1) Compression
2) Power
The power stroke is where there is no ignition that you can use to
suck gas/air into the cylinder ready to be compressed and burnt. On a
2-stroke you've got to get gas/air into the cylinder, compress is, burn it
and expel it all in a single up/down movement of the piston.
When you install an expainsion champeron a two-strokes. You can over-
scavenge them, i.e. blow too much fuel/air mixture through the engine
and into the exhaust (You can't do this on a 4 stroke as both valves are closed
making an expainsion champer useless).
The expansion chambers are designed such that
there's a reflected pressure pulse that packs these gases back into
the combustion chamber before the exhaust port closes. This is in
effect turbocharging with no moving parts. The arrival of this
pulse relative to port closure is dependent upon engine rpm, hence
the power band described by another denizen as 'violent'. Straddling
something like a YZ500 two-stroke when it 'comes on
pipe' can be described as a 'memorable' experience.
yah i understand that dude..
my comment was just for comedic purposes... not to have been taken seriously or literally..
cougar4life
12-14-2002, 07:12 PM
Originally posted by: ov3n
soooo.. what you're saying is, i need a lawn mower engine in my cougar so i can use the exhaust manifolds as expansion chambers? man that could work, lemme give weaponr a call so they could copy a briggs and stratton 2 stroke and sell it as the 'mad power yo-yo!' :)
:rofl:
IamSPDRCR
12-14-2002, 07:50 PM
ov3n,
I think your idea was a great one. Hell with the size of most 2 strokes we could put at least a dozen of them under our hoods!
CougarDemon
12-15-2002, 12:05 PM
i understand about the combustion chamber thing but how did i get the performance from gutting my precats? the less restriction thing?
secondly ok say i get the y-pipe with no cat on it. will i pass emissions with just a muffler on the exhaust system?
what i'm really thinking of doing just incase is get the long cats y-pipe. now what does a long cat do? is it just as good a s a regular sized cat? rob any performance?