Exhaust sizing? b18c turbo.

[Naturally Aspirated]

A bit of context is actually a wonderfull a thing and you guys are right in making your points, but back on topic and to the main question...........being

Question: Will 3" make more power?
Answer: Yes


Bumped-eg, Did ronnie recommend a 2.5" exhaust system knowing that your running a 3"DP??

[Hayce]

^ who made you boss. The OP's question was answered ages ago

[Codeman]

Originally Posted by [hitonu

]

I honestly have no idea personly my self but its funny u say that "ronnie" recomended it... some one who def knows what he is on about... evan from speed factor also recomends a 2.5" over a 3" for a turbo honda setup and points out there 300kw+ turbo civic also ran a 2.5".... so i dunno what back ground all you "experts" come from but having 2 guys who def know what they are on about say 2.5" is the way to go makes me think the same

just pointing out what i have been told... i walked in there asking if i should upgrade to a 3" and was told not to bother

IT IS ONLY a low boost 8psi setup 200kw ish. With a not overly big turbo, So like you guys say, smaller will spool it quicker.. (maybe) but bigger will support bigger numbers..

It will be custom made anyway, and i dont have anything atm, so i just gota pick a 2.5 or 3" thats why im asking. the port from the turbo is only around 2" anyway, so having 3" would be bigger than the turbo exit by like an inch!

Im still deciding, loving the discussion!
As far as this ca18det, its 550atw so iv been told. And went slower down the 1/4mile with a 3". Dont have the proof myself, just came from the guy that drives it. he would know.

[Locust2000]

If all you care about is peak power, then yeah bigger is better. Since very little of your driving time is spent there, I've always been more concerned about the power curve on the way there. The reason the correct diameter was important was to do with exhaust gas velocity and temperatures. Same as for a NA car. The thing is, that usually the answer is 'wind up the boost' to solve design issues. With an NA setup you can't do that. The same rules of flow apply to FI, it's just that they usually don't have to worry about reversion as the new intake charge, instead of being sucked in by the negative pressure in the cylinder, is being pushed in by the positive pressure after the turbo. Since it's being pushed in anyway, you could say that you don't need to worry about having a lower pressure area to draw in the charge.

I suppose it's like a NA setup is like a kid pulling a car with a rope tied around the front bumper to move it. A FI setup is like a few guys pushing the car from behind. But ideally, if you could have those few people pushing from behind, AND the person in front pulling as well, even though the person in front won't make much of a difference, it still contributes. Usually the solution is to add more or bigger guys to the back(more boost). Like I said at the start, I was referring to optimal design, not off the shelf of necessarily practical(due to time/money) design.

I didn't have time to go to Dinsdale today, will try tomorrow.

[Cyclone21]

Originally Posted by Codeman

Have seen many many people go for 3" on stock b18c turbo's with the likes of a To4e and turbo's a bit bigger than my GT28,

I have been told that while going to 3" is good for outright power, A 2.5" can support up to 600hp (proven) and will be much better for spooling around the street. So why go for 3"?

Will it be more responsive on the 2.5" round the streets compered to the bigger? But Will a 3" make more power?

2.5" exhaust on rb30det maxed out at 340whp (told to come back with bigger exhaust), what car made 600hp with a 2.5" exhaust?

If you are aiming for 200wkw on a GT28 I would highly reccomend 3" (straight as possible) exhaust..

What ca18det makes a true 550atw figure in the country? LOL

You want as least possible restriction in the exhaust as possible for Forced Induction unless you have a lot of money to spend on extensive R&D

[Naturally Aspirated]

Originally Posted by Hayce

^ who made you boss. The OP's question was answered ages ago

Didnt mean to rub off as being bossy, sorry.

Slaps ass in Hayce's avatar....leaving handprint

[erichns]

Originally Posted by Cyclone21

What ca18det makes a true 550atw figure in the country? LOL

Only Lars' CA18DET can make that kind of power with 2.5 inch exhaust, You should learn that :wink:

[bumpd-EG]

well i hope I dont come across as someone who needs to take "the cheapest option"
I just took advice from someone who i thought may have been a little more experienced than any random person on a internet page...
also did a little bit of research on the internet aswell
yes 3 inch is probably better but considering I wanted a undertank system and dont particularly want it to be dragging on the ground all the time 2.5 fits nice and i very much doubt there will be much restriction on the flow considering how straight my system is

[FREEZN]

correct. 2.5" will be fine on both your setups

but from my knowledge it wont increase turbo spool time like some are suggesting

[Codeman]

Originally Posted by Cyclone21

2.5" exhaust on rb30det maxed out at 340whp (told to come back with bigger exhaust), what car made 600hp with a 2.5" exhaust?

If you are aiming for 200wkw on a GT28 I would highly reccomend 3" (straight as possible) exhaust..

What ca18det makes a true 550atw figure in the country? LOL

You want as least possible restriction in the exhaust as possible for Forced Induction unless you have a lot of money to spend on extensive R&D

Couldn't tell you mate, I have only been told this, and then going to 3" went slower.. Don't quote me on this.
Everything i posted was more of a question, not a statement luke.

Sounds like i have been told the same as bumped-EG and got told..
Its not "NEEDED" for our setups, BUT.. if you want more power and less money in you pocket Ect Ect go to a 3"

ONE more question.

AS far as plumbing pipe back for the gate, further down is better? and would i go for a 2.5" for that?? maybe create more volocity pushing it back into the exhaust?

[bumpd-EG]

but isnt having a wastegate screamer what its all about?

[SLOTEG]

Originally Posted by bumpd-EG

but isnt having a wastegate screamer what its all about?

only if your in a gsr on cutties and stolen chromes, with your screamer boosting at 7psi everywhere :wink:

[Codeman]

Originally Posted by bumpd-EG

but isnt having a wastegate screamer what its all about?

After WOF is done yes. :wink:

Any chance you could PM me some of the details of your setup(s) as in parts and what power it made ect please mate? always good to see what others have done. Cheers.

[nemesisteg]

screamer haters, i got something for yall asses

[Locust2000]

Yeah me to on the civic, I got something for ya to scream about

[Bazda]

screamers FTW

http://www.youtube.com/watch?v=5SDn49tXgaI

[Coupe-R]

They were also going to the level of having these extra lips on the inside of the headers just after the motor to help cancel reversion

reversion chambers, you will see them on REAL hytech headers.

Thing with N.A is you want the exhaust tuned to the engine pulses etc, basically harmonics etc. squeezing everything you can out of the motor.

Turbo, I say who cares, slamm that motor with boost and give it a big exhaust.

you can go too small on turbo cars(choking the motor) , but will a 4" loose power over a 3"?? maybe off boost it could yes (but who cares), but on boost maybe the same power.

So there is a point where going small COULD be better in certain circumstances.

If I already had a decent 2.5" system on a stock internal boosted honda I wouldn't be jumping at a 3" system tho

[nemesisteg]

Originally Posted by Bazda

screamers FTW

http://www.youtube.com/watch?v=5SDn49tXgaI

thats what im talking about, i was loudest at NIMM 8)

[Hayce]

Originally Posted by Coupe-R

If I already had a decent 2.5" system on a stock internal boosted honda I wouldn't be jumping at a 3" system tho

Right on.
This is horses for courses. The question was answered in the 1st post, bigger is better, going too big will not net a unfavorable result, going too small might.

Screamers hah up to you, the govt. will still have their way.

[b16a2]

lets get this back up ang going again

been talking bout this tonight with someone, and was trying to convince him, but I think he just left confused, so im gna write it up in an easy way of summing it up

both in NA and Turbo situations, its has been proven may times with dyno testing that open headers / open DP make more power than with an exhaust

so from that we can definitively gather an exhaust is a restriction in some form or another to the air being pushed out of the air pump( the engine), again if you want scientific backup, inside an exhaust there will be a higher pressure than atmospheric, why else would the air inside the exhaust leave the exhaust unless it has a lower presasure area to move to, simple fluid dynamics, and simply you cant get high pressure with out a restriction of some sort.

Now to side track and cover smaller exhaust = more torque, i still dont understand why people say this, and honestly have yet to see a dyno plot to prove this, how could an even smaller restriction benifit greater torque production?? i have heard some people say that smaller exhaust will help scavenge air from the motor.. no scavenging can not occur in the exhaust, where all the primaries have already merged, so i still dont see how more torque can be produced

NOTE: Simply put scavenging works as follows, a high pressure exhaust pulse moving through a tube, has a low pressure zone following behind it, almost like a plunger in a syringe effect, this low pressure zone will cause gasses of high pressure behind it to speed up and move into the low pressure zone, again, fundamentals of fluid dynamics, movement occurs from high pressure to low,
( now again more sidetrack – header tube size will affect power, as in each exhaust pulse there is only a certain volume of air, if the tubes cross section is too large the pulse of air will be diluted( also get cold and slow down = bad) and the pulse effect with low pressure behind it will not be as evident.))

Back on track --
Now the best way to move air from a container to outside the container would be to create a huge pressure differential between the inside and out( much like a planes fuselage rupturing etc) either a pump or piston on the inside or a vacuum on the outside, but again the goal is to achieve as larger pressure differential as possible

Well designed headers will see benfits over just having a head open to atmosphere because of Scavenging. With headers because of the sealed tube, the exhaust pulses created a vacuum= lower in pressure than atmosphere, pulling gasses faster than the atmospheric pressure could

Once this has occurred and the pulses have been merged( neccesarry for scavenging) a low pressure zone lower than atmospheric pressure cannot again be achived, therefore, what part does an exhaust play In making power? None in terms of power increase only decreasing power( for this forget the practical roles of an exhaust such as sound and emissions management)



So hopefully my mad rambling above will show an exhaust is restriction to power, and can no way increase power by creating a bigger restriction though a smaller tube diameter = Total BS
So you want max power, get rid of your exhaust, cant do that, do the next best thing, remove as much restriction from the exhaust as possible, ie go bigger, stupid analogy but which will flow more water, niagra falls with or a straw with 10000000psi going through it, obvious isn’t it bigger is better!!!


See a few link with dyno plots, ad there many more just search HT, bigger exhaust make more power na and turbo through out the engines operating RPM range
http://bbmoto.net/wiki/index.php?ExhaustTheory

http://www.honda-tech.com/zerothread?id=2298917&page=1


and a plot of open header vs exhaust
http://www.honda-tech.com/zerothread/2306105



Now there is the valid argument, that a big exhaust pipe will lead exhaust pulses to stall, or to loose their rigid pulse form and merge with others, or become turbulent, actually slowing down/ hindering the exhaust gasses from leaving the exhaust, … there is some truth to it, that turbulent gasses will take longer to get out etc etc, but now we move away from science to the real world, have you seen a headers or an exhaust together which is so perfect pulses are stoped from merging ( inside the merge collector) or even that don’t converge on each other and loose power, and at this point at the end of the headers, if you have by some extreme feat of design and precision fabrication achieved this, show me an exhaust that is so smooth and free from disruption, that exhaust pulses will stay as pulses until they exit, you wont see this very often, chances are you pulses have already merged and become turbulent a chaotic by the time the leave their collection merge chamber.,

above I have mainly been speaking of a na situation, with a turbo its imposibble for the exhaust to still exit in pulses, they have to go through a turbine wheel…. I don’t know how your gna disrupt flow any more than with a turbine wheel!!!!, so this theory applies very little to NA situations, and not at all to Turbo

I honestly don’t see how on a turbo car( forget na for this) a larger exhaust will not make more power… and don’t tell me you got a quicker ¼ time, or it felt faster, show me dyno plots, or write me an argument, pull mine to piece show me im wrong, im quite happy to debate this, as I am very interested in this, and would love know what correct, am if that means being wrong so be it.