murlo26

iTrader: (9)

I remember reading a lengthy article somewhere about the different styles of downpipe, with divorced wastegate, bellmouth, external dump...etc.

I can't seem to find it so I figured we could discuss the differences in downpipe styles, and try to not have this get into a vendor discussion, rather just a style one.

Please only link vendor ones if you don't know the style type and are curious about it, otherwise I would like to know why one makes more power or is there a for sure winner?

Personally I am in debate about doing an open-dump vs. bellmouth because I thought open dump made the most but have seen conflicting information.

Thanks for input guys!

Talon_66

iTrader: (6)

Open dump, supposedly offers better boost control.
So that should help net you better power.

murlo26

iTrader: (9)

Yea, that is what i have heard, but it seems most the time it is followed by supposedly, lol.

Looking for hard facts if possible, maybe some engineering lingo.

Clark_Kent

iTrader: (5)

Murlo, I don't think you will find any substantial facts. I was looking for the same information last year when I was shopping downpipes. You will hear mixed reviews even from tuners and manufacturers. While some claim there is more power to be had, others claim that an open dump downpipe is simply a noisemaker that pisses off motorists and triggers false knock. Even if the advantage is very slight, to the point of being negligible, the question you should ask yourself, "Is it worth the extra noise for a few more ponies?"

EvolNinja

iTrader: (22)

I'm getting the O2 eliminator from MAP and see how much more noise it will make. As far as I know, it will make more noise during WOT but suppose to be the same as any other DP during idle.

High_PSI

iTrader: (50)

Having a dump does many things if done properly. It takes all back pressure off of boost control so it is much better. It also makes your exhaust more efficient as it is not dealing with the additional exhaust flow from the waste gate. it allows you to run a larger housing to funnel air through, the Evo Power Mods unit I run is 40% larger then stock. It scares the **** out of people and makes tunnel visits legendary.

GetterDragun

iTrader: (2)

What does the different downpipe names mean? I often see downpipes listed as "Downpipe", "O2 Downpipe", and "O2 Eliminator Downpie" and do not know the differences.

Also, what does "Dump" mean? Is the dump basically seperating the wastegate from the exhaust and just piping the wastegate pipe to atmosphere?

lowkey

iTrader: (5)

Search on the Cobb website. They had a white paper posted with all the different packaging, power and complexity trade offs that goes into down pipe design.

But why bother? Just get the AMS:

- big bell mouth
- 3 inch
- cast
- flex section
- race proven

You won't be disappointed.

murlo26

iTrader: (9)

This was my original plan, for all those reasons and reliability since it is cast as you mentioned. I guess I am still wondering if it will be worth it to get an open dump. I had open dump in my rsx and it was awesome sounding.

murlo26

iTrader: (9)

Well my car is pretty much ridiculously loud already with the testpipe/buschur bullet catback and cams anyway. I don't think it can get much louder. And if it made 5-10hp over a big bellmouth, sure i would take the noise for that.

lousEVOxmr

iTrader: (3)

i bought 3 weeks ago the rexpeed one , for 180 $ wow , i was surprised of the quality saying that its 180$
i instaled it with no problems , its sound diffrent then befor ,
i will get #'S up as soon as i get retuned to find out the diffrences

murlo26

iTrader: (9)

Again, its nice you got your downpipe, but i want this thread to be more technical. Not how much power someone made on a specific setup.

I am hoping we could get a rating scale for an in theory this type of downpipe has more potential...but this isn't looking good.

lowkey

iTrader: (5)

Found the Cobb link for you with the discussion on DP design.

http://www.cobbtuning.com/info/?ID=3222

I had also posted a Poll in this forum sometime last year. It was kind of narrowly focused on just a few DPs, but there were some interresting comments.

https://www.evolutionm.net/forums/ev...downpipes.html

murlo26

iTrader: (9)

Yea that is the link i was looking for that I read before, thanks

So Cobb said they had the best results with the bellmouth design. Very interesting, seeing as how i would have thought the open dump would've been the best, but sounds like they say no.

lowkey

iTrader: (5)

Don't think they considered open dump in that paper, just divorced design with the wastegate section joining later down in the exhaust.