RACING INTEGRATION

will I benefit from a 3" exhaust with the folowing setup?

b18c1 block
82mm CTR pistons
arp rod bolts
ITR flywheel
ITR or P&P head
spoon cams
ITR or blox intake manifold
hytech tri Y headers
68 or 70mm TB
thermal intake gasket
ARP head studs
AEM v2 intake
microtech EMS




Modified by RACING INTEGRATION at 11:35 AM 10/22/2007

mar778c

iTrader: (1)

yes

Teamdiesel

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mar778c &raquo;</TD></TR><TR><TD CLASS="quote">yes</TD></TR></TABLE>
why?

mar778c

iTrader: (1)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Teamdiesel &raquo;</TD></TR><TR><TD CLASS="quote">
why?</TD></TR></TABLE>

lol, the same reason going from stock to 2.5" improves hp.

SleeperGSR

i'm not a pro engine builder. but from my understanding you don't want to go much over 2.5 for a N/A 1.8L motor. As long as your HP is under 400 i think you would be fine with a 2.5. N/A motor need room for a large volume of air to come out, but you still want some velocity around it to help suck it out.

b19coupe

There is a point at which switching from a 2.5" to 3" exhaust will benefit a naturally aspirated 4 cylinder Honda engine. I suspect that the power level/air flow volume that will require a 3" exhaust is in excess of 220 whp. There is such a thing as too big.

SleeperGSR

Guess i was a little off with my 400hp guess. Thanks for adding a realistic number.

Major_Wolf

BUT if you want a turbo on your b18c1 in....1 years,maybe the 3'' is a good option...

92cxturbo

I dont see how there can be such a thing as too big? doesnt pretty much any car benifet from running open header or down pipe? The only thing I see bigger hurting is noise factor.

AccordSleeperZzZ

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 92cxturbo &raquo;</TD></TR><TR><TD CLASS="quote">I dont see how there can be such a thing as too big? doesnt pretty much any car benifet from running open header or down pipe? The only thing I see bigger hurting is noise factor. </TD></TR></TABLE>

I believe once you go too big, you start to lose some "low-end grunt" if your power is below a certain point(I.E. like b19coupe's quoted ~220whp).

SleeperGSR

if it is too big the exhaust gass will slow down too much on the way out. Because there is so much pressure in a turbo system can help expel the gas. From what i understand a N/A build you want a high exhaust velocity and a turbo build you want a high volume of exhaust expelled. Maybe someone with more smarts than me can confirm this but that's what i can pass along. Sorry if it's not right.

b19coupe

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 92cxturbo &raquo;</TD></TR><TR><TD CLASS="quote">I dont see how there can be such a thing as too big? </TD></TR></TABLE>
On my 1.8 liter ITR motor I tested a standard Hytech ITR header against a big tube Hytech ITR header. The smaller header was better everywhere below 7,000 rpm. The big tube was only better at peak by about 3 or 4 HP. There is something to be said for picking the right parts for your particular engine combination.

acydphryck

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b19coupe &raquo;</TD></TR><TR><TD CLASS="quote">
On my 1.8 liter ITR motor I tested a standard Hytech ITR header against a big tube Hytech ITR header. The smaller header was better everywhere below 7,000 rpm. The big tube was only better at peak by about 3 or 4 HP. There is something to be said for picking the right parts for your particular engine combination.</TD></TR></TABLE>

DING!!! right on the money...can't have an exhaust that's too big for a certain motor setup. since his motor is still a 1.8L, going to a 3" exhaust piping may actually be too big...something about exhaust gases and back pressure...not quite sure how to explain clearly

92cxturbo

yes but we are talking exhaust not headers. primary tubes can play a big difference in power but after the collecter how much will it efffect power? thats the question.

mar778c

iTrader: (1)

Hmm, I had a 3" exhaust on my 1.6L and it seemed to be alright. I've tuned other NA cars with 3" exhaust and they seemed to make really good power. I guess I'm going i the wrong direction.

95BG33PGSR

when i switched from 2.5" to 3" on my engine, i noticed a conciderable HP difference, this was 2 years ago so im not sure of the exact number...but im also running a 84.5mmx89mm 12.5:1 compression engine... i would think 2.5"should be fine for your set up but you can always try it.

AccordSleeperZzZ

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 95BG33PGSR &raquo;</TD></TR><TR><TD CLASS="quote">when i switched from 2.5" to 3" on my engine, i noticed a conciderable HP difference, this was 2 years ago so im not sure of the exact number...but im also running a 84.5mmx89mm 12.5:1 compression engine... i would think 2.5"should be fine for your set up but you can always try it. </TD></TR></TABLE>

don't confuse peak horsepower with total useable horsepower. having the extra few hp at 7000rpm is nice, but what good it is if you have to shift right after you hit it? personally i'd prefer to have a little more midrange to play with. but, thats just me.

95BG33PGSR

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AccordSleeperZzZ &raquo;</TD></TR><TR><TD CLASS="quote">

don't confuse peak horsepower with total useable horsepower. having the extra few hp at 7000rpm is nice, but what good it is if you have to shift right after you hit it? personally i'd prefer to have a little more midrange to play with. but, thats just me.

</TD></TR></TABLE>
that's what i mean, i gained power accross the whole chart, not just on the top end.

b19coupe

I guess it's time for more dyno testing...

92cxturbo

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b19coupe &raquo;</TD></TR><TR><TD CLASS="quote">I guess it's time for more dyno testing...</TD></TR></TABLE>

X2

S@nt0s

Exhaust scavaging

copied from here

http://www.uucmotorwerks.com/h...h.htm

Some say that "an engine needs backpressure to work correctly." Is this true?

No. It would be more correct to say, "a perfectly stock engine that cannot adjust its fuel delivery needs backpressure to work correctly." This idea is a myth. As with all myths, however, there is a hint of fact with this one. Particularly, some people equate backpressure with torque, and others fear that too little backpressure will lead to valve burning.

The first reason why people say "backpressure is good" is because they believe that increased backpressure by itself will increase torque, particularly with a stock exhaust manifold. Granted, some stock manifolds act somewhat like performance headers at low RPM, but these manifolds will exhibit poor performance at higher RPM. This, however does not automatically lead to the conclusion that backpressure produces more torque. The increase in torque is not due to backpressure, but to the effects of changes in fuel/air mixture, which will be described in more detail below.

The other reason why people say "backpressure is good" is because they hear that cars (or motorcycles) that have had performance exhaust work done to them would then go on to burn exhaust valves. Now, it is true that such valve burning has occurred as a result of the exhaust mods, but it isn't due merely to a lack of backpressure.

The internal combustion engine is a complex, dynamic collection of different systems working together to convert the stored power in gasoline into mechanical energy to push a car down the road. Anytime one of these systems are modified, that mod will also indirectly affect the other systems, as well.

Now, valve burning occurs as a result of a very lean-burning engine. In order to achieve a theoretical optimal combustion, an engine needs 14.7 parts of oxygen by mass to 1 part of gasoline (again, by mass). This is referred to as a stochiometric (chemically correct) mixture, and is commonly referred to as a 14.7:1 mix. If an engine burns with less oxygen present (13:1, 12:1, etc...), it is said to run rich. Conversely, if the engine runs with more oxygen present (16:1, 17:1, etc...), it is said to run lean. Today's engines are designed to run at 14.7:1 for normally cruising, with rich mixtures on acceleration or warm-up, and lean mixtures while decelerating.

Getting back to the discussion, the reason that exhaust valves burn is because the engine is burning lean. Normal engines will tolerate lean burning for a little bit, but not for sustained periods of time. The reason why the engine is burning lean to begin with is that the reduction in backpressure is causing more air to be drawn into the combustion chamber than before. Earlier cars (and motorcycles) with carburetion often could not adjust because of the way that backpressure caused air to flow backwards through the carburetor after the air already got loaded down with fuel, and caused the air to receive a second load of fuel. While a bad design, it was nonetheless used in a lot of vehicles. Once these vehicles received performance mods that reduced backpressure, they no longer had that double-loading effect, and then tended to burn valves because of the resulting over-lean condition. This, incidentally, also provides a basis for the "torque increase" seen if backpressure is maintained. As the fuel/air mixture becomes leaner, the resultant combustion will produce progressively less and less of the force needed to produce torque.

Modern BMWs don't have to worry about the effects described above, because the DME (car's computer) that controls the engine will detect that the engine is burning leaner than before, and will adjust fuel injection to compensate. So, in effect, reducing backpressure really does two good things: The engine can use work otherwise spent pushing exhaust gas out the tailpipe to propel the car forward, and the engine breathes better. Of course, the DME's ability to adjust fuel injection is limited by the physical parameters of the injection system (such as injector maximum flow rate and fuel system pressure), but with exhaust backpressure reduction, these limits won't be reached.

- Adapted from Thomas V.
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Now for 99% or the NA set ups out there 2.5 is enough.. if your making more then 250WHP you might benefit from a 3".. key word was MIGHT

92cxturbo

I think that supports my opinion but Im alittle phaded right now, lol

AccordSleeperZzZ

not one to admit defeat without due proof(dyno testing, in this case), this article does seem to be damning my thoughts.

i'm not too big to admit when i'm wrong, but i would like to see a dyno to prove this because i'm still skeptical.

b20beast978

X2!

goforbroke

Where is the rest of your exhaust setup? Like your header......