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i've heard many stories regarding test pipes.
some say u lose torque because there is not enough back pressure and the car drives like shiet, but however u gain top end. others reckon it doesnt benefit NA cars at all, only boosted cars.
anyone wanna throw in their 2cents and post some dyno sheets =]
The only benefit is a lighter wallet when the EPA fines you $10,000 for not running a cat. Go for a high flow cat instead.
if it didnt give u more power why would ppl take their cats out n put the test pipes in?
cause they're too cheap to buy a high flow cat :p
It would really come down to the build set-up wouldn't it?
only good for track
only good if u want you future kids to be poisioned with polluted air
coz putting a test pipe make u a rebel and give u 2 more whp only ur engine is quite highly modded.. putting a test pipe without engine mods is prob 0.5whp..
That makes sense :thumbsup:Quote:
Originally Posted by 90LAN
umm har har? im asking if there is any benefits to a test pipe, not wat it does to the environment. and obviously track use onlyQuote:
Originally Posted by BlitZ
straight through pipe --- more power
You are better off using a straight through exhaust with no muffler and no resonators with a cat, then if you used an exhaust with mufflers but no cat.
possible pop some flames to ;)
they only make a difference on HIGH horsepower cars that make big power at the top and don't need the backpressure. People who do them on mildly modified cars don't really know why they do it... its coz their friends mums brothers dogs girlfriends auntys sons moms sister said its t3h h3ktic1!111!!!!Quote:
Originally Posted by absolutR
heres simple proof, on a bogstock B16a2, get a full 2.5in mandrel bent exhaust, you will notice a loss in low-mid range power and response for a MARGINAL gain in topend.....
a very effective high flow cat will actually give gains because:
- the catalyst is more effective while flowing more therefore...
- apart from burning like blow-by oil that went in the combustion chamber...
- it effectively ignites any unburnt fuel mixture also which may cause exhaust pop...
- and because exhaust cools down as soon as it leaves the head, the catalyst re-igniting them creates heat and accelerates exhaust velocity again, therefore...
- 'scavenging effect' is increased as increased exhaust velocity creates vacuum and pulls gases from the combustion chamber when the exhaust valves open, therefore...
- also scavenging more air on the intake side come the time the intake valves open....
I noticed the characteristics/power delivery of the motor changed but not worth the smell and pollution to justify it.
Just get a nice big hi flowing cat ;)
are those figures from said drag cars or your average car?Quote:
Originally Posted by claymore
coz i'm speaking from experience from a few years ago.. there was a 2-4wkw power loss before 5000rpm range and i think ~1.7wkw peak gain somewhere above 6800rpm.
annoying thing was that the exhaust shop didn't tell me about the legailities even though it was my choice.. i was going to keep it until another customer that day actually told me about the fines, etc... i think as an exhaust shop it should've been their job to inform customers of these things.
when your young and not many performance parts are available to you and don't know much about cars you end up buying stupid things like these... i was one of them, even bought hiclone, fuel line magnets, etc...
sometimes a test pipe is used to replace the cat when tuning. instead of tapping a 2nd bung into your headers the extra bung is on the test pipe for wideband O2 Usage.
for example
http://images.channeladvisor.com/Sel.../HC9600GSR.jpg
http://images.channeladvisor.com/Sel.../HC9600GSR.jpg
yes!! and it sounds so beautiful :thumbsup:Quote:
Originally Posted by aaronng
Quote:
Originally Posted by claymore
real drag racers/circuit racers are running 600-8000 horespower and massive displacement engines with turbos and superchargers, or just big n/a motors, there is no need for backpressure.
on a street driven, N/A 1.6 litre 4banger, back pressure is needed.
i think u might be a little wrong, 10-15hp gains? these figure probably only apply on high powered vehicles or perhaps large displacement engines, i jus cant really see how u could gain that much power out of a 4cylinder, unless u can prove me wrong =]Quote:
Originally Posted by claymore
also something interesting i found: you could probably say a high flow cat would give u the same gains as a test pipe and also making things legal
http://img503.imageshack.us/img503/9...stdynosqk2.jpg
http://img503.imageshack.us/img503/1...resultszu5.jpg
:thumbsup: cool post, good info
Standard cats are extremely restrictive, but I understand what you're saying. Upgrade your mufflers/delete them first, then if you're game, go for the cat (once you get off the public road ofcourse!).Quote:
Originally Posted by aaronng
I want to get a custom side-pipe from my J's racing headers for the track. I'm happy with the performance of my car, but when I'm on the circuit I love to have the sound of a race car (which mine sounds like with BC cams, quads etc.).
awsome find buddy, i wonder if that stock cat was a jdm one though?
I would think 90% are the same..Quote:
Originally Posted by EGJOE
I have never heard a japanese cat giving more power than an aus cat
My understanding is Honda's like back pressure.
yeah they are running open pipes. no cat, no mufflers.Quote:
Originally Posted by claymore
this doesnt mean they dont need backpressure
lets say for example we have two engines, they are the exact same, they need to be, due to class regs.
one of them has a "normal" sized exhaust, whatever that may be, say 2" and one of them has an exhaust that is 6" the whole way.
what one do ytou think would be making the best power curve?
Really?Quote:
Originally Posted by beeza
afaik back pressure is undesired on any motor setup
i believe the idea is that smaller motors can't maintain a high velocity of gasses through such large pipes i.e. b16 with 3" exhausts
the whole 'it needs back pressure' idea is a myth
it needs an appropriate sized exhaust to keep exhaust gas velocity high
too big exhaust, and the motor can't move the gas through the large diameter pipes efficiently
Yeah,that's my understanding.Quote:
Originally Posted by fatboyz39
So U need to choose the right size pipe.Then are resonaors and cat's just restrictions then?
Read Vinny's post. He got it right. The idea is to maintain the exhaust gas velocity. For a fixed volume, the velocity decreases as you increase the diameter of the piping. Too small, and you create backpressure. Too big and you lose velocity. You want to go as big as possible without having the velocity drop too much. Of course, the volume of the exhaust gas is never constant. At low RPM, the volume is smaller. At high RPM, the volume is larger. So you choose your diameter based on the volume of exhaust gas at the RPM that you want optimum power/torque at. Hence street cars have a smaller diameter for low to mid RPM, while race cars have it larger since they stay at high RPM most of the time.Quote:
Originally Posted by beeza
Cats, resonators and mufflers are all restrictions which slow down gas velocity. The are a must for environmental reasons in a street car. But for a race car, they are undesirable.
Perfectly said!
Thanks so much Aaron :)
fkn well said guys
So true eh!
I've been looking for this for a while now.
the term "back pressure" is just another mis used and mis understood term in the car modifiying world. Like "coilovers" etc.
It all makes sense to me now.Similar when people say MSD ignition systems do nothing :)
post up some pics of ur teg timmy !!
can i summarise by saying:
dont get an open pipe for ur street car for two reasons:
1. u will lose power in the low rpm range, for the reasons mentioned before, some small gains in the high rpm range
thats pretty useless since its a street car, and for u to really feel a difference ud have to be living in vtec for ever, this creates all kinds of issues
but since i assume u drive normally most of the time, u will appreciate the power loss ALOT more than the power gain
2. Its illegal for street cars to run an open pipe
10k fine
environmental filth
and most likely ur car will smell like a broken lawn mower leaking fuel forever
The statement that a NA engine needs backpressure is a myth,as explained by Vinny in post #31, and expanded on very well by Aaronng in post #33.
If I could bring a little "tech" to the discussion.....:)
The reason that most people arrive at the conclusion that they need back pressure is that the engine feels unresponsive in the lower rpm ranges after they go to an "open system" or delete the mid pipe/ muffler/cat/ resonator.And this is true, the engine will lose some torque in the mid range, but the reason it does this is not strictly to do with air speed (scavenge velocity) though it does have an effect.
A highly tuned engine relies heavily on "overlap scavenging" by the exhaust to get the best from the longer duration cams used.This scavenging occurs due to pressure waves that reflect up and down the exhaust system at varying velocities due to rpm.These pressure waves are created by the high pressure exhaust gas exiting the chambers and through the ports being forced though a change in the exhaust systems cross section. Either the end of a pipe or the restriction of a muffler or cat.
In a road car the pressure wave is reflected by the cat, in a race car it is the open end of the pipe.So by simply removing the cat what you are doing is dramatically lengthening the point at which the exhaust negative pressure wave is reflected back to the cylinders.It is this pressure wave that helps to pull the intake flow into the cylinder while BOTH intake and exhaust valves are open (overlap).So the engine see's a rather dramatic loss in pressure drop through the intake ports(suction).That is why the engine loses some torque in the mid range. Eventually as rpm rises the window of overlap decreases in relevance and the torque loss is recovered.
At this stage I know little of the Honda engines tuning requirements, though an engine is only an air pump so they are all similar. However, I would think that the goal of most would be to maximize power upwards of 5000rpm, if this is the case, it is all about minimzing restrictions, whilst being midful of the intake/ cam/exhaust tuning.
For the street... high flow cat is the go.
For the track.... play with different reducers/expanders and varying cross sections of pipe, the fun never ends!!!
DAMN!!
We got to sticky this sh!t!
I can't believe how tech that sounded yet I understood all of it!
Thanks so much for expanding on this.
Can you give a link? I searched and didn't find a source of info that he could have copy and pasted from.Quote:
Originally Posted by claymore
Hang on there fella......Quote:
How about you showing your sources for that post and give them credit for the information that you post as your own.
plagiarism isn't my thing.
When you have been building race engines for over 20 years you learn a thing or two. Sometimes you might even share a thing or two....
This was one of those times.
Think you better sack up mate and appologise.
lol its ozhonda
Meaning?Quote:
Originally Posted by tekung89
There's a right way to do things and there's the wrong way.Claymore demostated the wrong way to go about it and he has pissed people off.
I really couldn't be bothered to write this because me and Claymore are buddies now :) but it's this attitude that stops people coming here and sharing thier wealth of knowledge with us.Those that do make it through the storm will be watching thier back = honda-tech.com :thumbdwn: ya know?
lol...........................................
zombiez and crabz
hahhahahahahahahahaha ahhhhhhh just AWESOME!!!! :) :) :) :) :) ohhh yeah!!!!
Being a newcomer does not make a person a "noobie". Everyone on this forum was once a newcomer. Doesn't mean that they are noobies.Quote:
Originally Posted by claymore
Aah... whatever........:zip:
Hope you don't feel too offended and hold it against us at Ozhonda...... :(Quote:
Originally Posted by 82911
Nah.... my skins too thick for that.:thumbsup:Quote:
Hope you don't feel too offended and hold it against us at Ozhonda......
hehehe
X2 so true!!:thumbsup:Quote:
Originally Posted by aaronng
this is getting of topic but atleast the thread has been covered and thoroughly discussed, more questions to come from me soon lol
huh.?Quote:
Originally Posted by claymore
just to add some juice to the fire,
ive personally seen a back to back, stock cat plus HKS cat back on an aussie P72 B18C realise a very healthily rising curve from about 4000rpm to 15kW peak,thru the stock cat being punched out & dollied up dead straight 2.5" pipe to the rear of the car held up by a jack stand.
was on an indoor dynojet & the fricken loudest thing ive ever heard in my life.
I don't intend to drag this thread any more off topic than it already is, except to correct Mr Claymore's insight into the thinking behind my "radiator upgrade thread".
The asumption that I asked a "noobie" question regarding radiator sizing in a civic also asumes that i would have little understanding of WHY you would upgrade a radiator in the first place. It is my experience that heat transfer and eventual rejection is very model specific and that is indeed the reason for the question.
Noobie to Honda... yes!
Noobie to internal combustion....no.
But thanks for the welcome!!!!:thumbsup:
Well I went to my muffler shop to get the resonator taken out but he talked me out of it,saying I will lose low/mid range, but he wasn't sure about the twin loop muffler and how it works exactly....
My set-up:
d16y4 (non-Vtec) Automatic
X-force headers
2" exhaust
Hi flow metal cat
Resonator
X-force twin loop exhaust
I definately don't want to lose low/mid range on my daily.What do you guys think?
removing the resonator won't do squat but make it sound a bit different
true on a honda :pQuote:
Originally Posted by vinnY
~2wkw gain on sr20 back to back.. but the rubber intake on that engine was a huge hindrance to begin with
It's has been doing my head in! So I'm happy to hear that.It will make it more droney sounding in the car too wouldn't it?
dont do it. You'll regret it.
Cheers Fatboy!
So glad he talked me out of it :)
If it's just resonators, it's no biggy.
I've had 2 removed and only left the CAT + muffler on a 2.5" system.
You get more of a open sound, more bark.
Previously had no CAT and below 4,000rpm it was kinda annoying. More reason to stay above 4,000rpm I say :)
haha forsure! only thing is ya use more petty offcoarse..it's a trade off.Sometimes I put in $50 and have fun.