1990DX

Hey guys, I'm new here. Question. I'm building a b20vtec. Which consists of
b20b block
itr head- port and polished
itr cams
itr manifold with skunk2 68mm throttle body
jg edelbrock headers 2.25 collector/flange
itr 4.7 fd LSD tranny

okay so here is my question. Exhaust wise, will the 2.25" collector and exhaust I plan on running a bad idea? I am hearing mixed things, people are telling me that 2.5" is a bare minimum for a b20 build. But Some people say that 2.25" is good enough and won't choke the motor and make it lose power. I've taken my question here. Hopefully I get the solid answer I need. Thanks in advance!

bambam

Please tell me you're raising compression...

$hawNPeeZyy

I'd go with a 2.5" setup that included a header with a 2.5" collector, with a 2.5" setup you're able to extract more power and it's still pretty quiet. Just my $.02

GranDaddyPurp

you gotta pay to play. of course the 2.5 inch would be best to let the beast breathe but if you have a good deal on a 2.25 inch go get it. i chocked up my b20vtec when i was low on money i have a full 2.5 inch exhaust with hytech rep header. i sold the header and ran stock exhaust manifold from a 94 gsr. and my car def feels different but not as bad as you think

DDTECH

Why does everyone still believe in these small exhaust setups.

Go 3''..

and for god sakes.. if its a stock b20b blocks.. knotch your valve reliefs.

1990DX

Money isn't a huge issue, I was just wondering becuase the manifold that I have JG Edelbrock has a 2.25" collector. And people have been telling me to go bigger, but I just wanted some opinions on how big. And 3"? Isn't that overkill? I'm not trying to get pulled over every 5 minutes.

DDTECH

3'' with a good res wont be loud, unless you "Get on it".. you need to run bigger exhaust systems on these motors.

1990DX

Mind me asking why? I'm slightly noob-ish.

DDTECH

You, dont want any backpressure.. at all
You want more velocity flow..a 2.5'' header collector spread out to 3'' will do just fine.. put a res on there if you think its going to be loud..

B16's , bone stock b16's, have seen huge power gains from just bolting on a 3'' exhaust.. search.. there's alot of information out there about it.

1990DX

ohh okay. I will look into a 3" exhaust. with res.

midnighteg-6

yeah sounds like a mild build but i will still go 2.5 but i will really recomend you to trow some high dome pistons atleast some 11: cr or someting

MatthewFarrar

Totally agree, The 3 inch is the best set-up for a B20VTEC.

EpHatchy

WHAT ARE YOU DOING TO THE BLOCK TO MAKE IT PUT UP WITH THE ABUSE..UNLESS YOUR SHIFTING AT 7000RPM

SORRY FOR CAPS MY CAPS KEY IS BROKE

bambam

A smaller exaust would produce higher velocity. Think of blowing through a drinking straw compared to a paper towel roll.

DDTECH

Not.. really.. but w/e.

a smaller exhaust would produce higher velocity, going into a higher piping. notice all custom headers start small and work their way up to getting bigger, step by step..

2.25 and 2.5 is entirely TOO Small period for any all motor setup wanting to make power..

MatthewFarrar

I completley agree, But, Where as the 2.0 liter Motor breathes better with the 3 Inch Exhaust. A 1.6 liter Motor would Breathe fine with the Velocity of the 2.5 Inch, For a Mild Build atleast.

1990DX

okay so another noob question

b20b block
itr head- port and polished
itr cams
blox intake manifold with skunk2 68mm throttle body
hytech headers w/ 2.5" exhaust
itr 4.7 fd LSD tranny

how much power would I roughly be making? And I'm a decent driver this motor is going in a ek coupe. What times you think I could make on the 1/4?

DDTECH

170-180whp and your torque will be low , in a pig of a ek you might run low 14's.

PyroProblem

170-190 whp depending on the tune/dyno/countless other variables
2 liters typically produce around 145-150 tq at the wheels also depending on alot of variables...
I could see a nice setup hitting 13's easily.
You didnt mention any tuning. Have you thought about what your gonna be using?

1990DX

Tuning wise, I'm bringing it to a local Tuner. We still haven't discussed what we'll be using. I also changed the headers I'm going with. I got a wicked deal on a Skunk2 Megapower header. So I changed to that.

bambam

How so? I think you should research backpressure and scavenging.

bambam

Do you think that the fraction of a second that the exhaust valves in any cylinder open up to deposit the spent gases into the exhaust manifold creates enough force to get those gases all the way to the tip of the muffler all on their own? Believe it or not, exhaust sizing affects this process. . So does primary pairing as well as the distance between pairings. Your selection in exhaust sizing or header sizing will also affect exhaust valve or cylinder temperatures.

To say 3 inch is the end all be all sizing for an n/a setup is not true.

On a side note, which cylinder has the highest exhaust gas temps? On motors that spin a bearing, which cylinder does it occur in? In a plenum style intake manifold, which cylinder benefits the most and what cylinder benefits the least? How does this affect cylinder specific afr's? Just some food for thought.

slowsleeper

don't worry about it if you are tight on money. I made 240+ whp through a 60mm RS-R ExMag exhaust with a chambered muffler. Spend that money elsewhere for now..my .02

DDTECH

I've already explained in about 3 paragraphs the whole scavenging and backpressure blah blah blah.

there's plenty of dynos on here.. showing that bone stock b16's excel from 3'' exhaust... you realize you dont want any backpressure at all? If you think you do, please tell me, because i'm not going to even open up the discussion on exhaust tone, and how that creates power..

This isn't my first rodeo.. you wanna make power. Do whats been proven. Everyones saying run 2.25 or 2.5''.. I gainned 12 by switching to a 3'' from a 2.5, and i gainned even more running @ open header.

This goes without saying , its the same thing as tuning a "tuned " length intake.. the properly build header, connected to a non-bottle neck exhaust will provide good power..
Alot of people down here run a header thats 2.5'' collector, flare it to 3'', then right before the axle back flare it to 4''.
people are more concerned with noise then making power.. run 2 resonators if your worried about noise.


A smaller-diameter pipe geometry will tend to keep the flow rate up, but it will also lose heat more quickly (less exhaust gas per linear inch of pipe). Velocities is, if you can keep the exhaust gases moving in the exhaust pipe, they will cause a small reduced-pressure area behind the closed exhaust valve, in the exhaust. This happens because the gases have momentum. They move away from the valve, creating a localized reduction in pressure. When the exhaust valve opens, this reduced-pressure zone will help evacuate the burnt gases from the cylinder.
To create velocity, you need to start with a set base, thats why headers start with a smaller primary, and then get bigger, and bigger, then merge to a collector, from there you so flare out and go bigger..if you can afford it...look at all these custom headers..
You think these guys dont know what they are doing? Your obviously not paying attention to how the headers are built..

op, wanna make power, run a 3'', if not, run the smaller exhaust.

DDTECH

Think how much you could have made, had you let the motor breath better