Test pipe, do they really do you any good?

[krogoth]

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

[82911]

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!!!

[beeza]

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.

[aaronng]

How about you showing your sources for that post and give them credit for the information that you post as your own.

Can you give a link? I searched and didn't find a source of info that he could have copy and pasted from.

[82911]

How about you showing your sources for that post and give them credit for the information that you post as your own.

Hang on there fella......
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.

[tekung89]

lol its ozhonda

[beeza]

lol its ozhonda

Meaning?

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 ya know?

[krogoth]

lol...........................................

zombiez and crabz

[beeza]

hahhahahahahahahahaha ahhhhhhh just AWESOME!!!! ohhh yeah!!!!

[aaronng]

If that is your original thinking good on ya. The reason I questioned your post was you are an un-introduced noobie that posted some advanced information that is way beyond what normally comes from noobies. Perhaps if you had introduced yourself or posted something like "after building engines for 20 years I have found......"

Didn't you notice the smiley?

As for the forum gadfly what makes you think that some wacko in need of serious professional mental health repairs posting about zombies and reptiles taking over the world on a CAR FORUM (and believing it) would not scare off more noobies than someone questioning the origins of another post?

Some advice drink the RED koolaid.

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.

[82911]

Aah... whatever........

[aaronng]

Aah... whatever........

Hope you don't feel too offended and hold it against us at Ozhonda......